CA2128092A1

CA2128092A1 - Composite abrasive filaments, methods of making same, articles incorporating same

Info

Publication number: CA2128092A1
Application number: CA 2128092
Authority: CA
Inventors: Loren L. Barber, Jr.; Dennis G. Welygan; Richard M. Pihl
Original assignee: Individual
Current assignee: 3M Co
Priority date: 1992-03-19
Filing date: 1993-02-11
Publication date: 1993-09-30
Also published as: EP0739261B1; TW222668B; EP0739261A1; DE69320375T2; US5616411A; JP3683581B2; AU658494B2; DE69320375D1; US5460883A; CN1092434A; US5571296A; US5737794A; ATE169545T1; WO1993018890A1; AU3664493A; JPH07504852A; KR950700811A; ZA931149B; BR9306055A; US5518794A

Abstract

A composite abrasive filament, including at least one preformed core at least partially coated with a hardened, abrasive-filled thermoplastic elastomer, exhibits increased abrading life over previously known abrasive filaments. Previously known abrasive-filled nylon filaments have limited stiffness and lose their stiffness as temperature approaches 70 ·C. The composite abrasive filaments of the present invention are more efficient and more resistant to flex fatigue failure than abrasive-filled nylon filaments. Also disclosed are methods of making such filaments and using such filaments in article form to abrade a variety of workpieces.

Description

-- w ~ 93/lXX9~ PCT/US93/01246 COMPOSITE ABRASIVE FILAMENTS, METHODS OF MAKING SAME, ARTICLES INCORPORATING
SAME

S ~ CHN~CAL PIELD
The present invention relates to composite abrasive filaments comprising preformed cores coated with an abrasive-filled thermoplastic elastomer.
Z~;~8(~92 BACKGROUND ART
Nylon abrasive filaments were developed in the late 1950's as a man made alternative to natural abrasive filaments. At about that time an extrusion process was developed for dispersing abrasive par~icles uniformly in a nylon matrix in the form of a filament (U.S. Pat. Nos. 3,522,342 and 3,947,169). A
review of nylon abrasive filaments is presented by Watts, J.H., "Abrasive 15 Monofilaments-Criticai Factors that Affect Brush Tool Performance", Society of Manufacturing E~ngineers Technical Paper, 1988, a written version of a presentation by the author at the WESTEC. Conference, held March 21-24, 1988. As explained by Watts, as filaments of this type wear, new abrasive particles are exposed. An abrasive filament brush.tool made using a plurality ~0 of these filaments is thus regenerated during use. Some of the advantages of nylon abrasive filaments are their safety, cleanliness, cutting speed, low cost,superior radius and finish control, adaptability, and ease in design.
A key property of nylon and other thermoplastic matenals is its "memory". In a brush filament this is referred to in the art as "bend 25 recovery", or the tendency for a deflected filament to retum to its original deployment. The bend recovery for nylon is generally over 90%, i.e., the filament returns to about 9Q% of its original deployment after being deflected.
Over time in operation, such as in a brush tool, rnost abrasive-filled polymeric filamen~s will take a set shape, and unless the filaments of the brush30 tool recover, the brush tool becomes soft and loses its effectiveness. Bend recovery is determined by filament diameter, relaxation time, strain, deflection WO 93/18890 PCI~/US93/0!?,.~16 Z~2809Z - 2 - I
time, and environmental conditions. Among synthetic filaments made to date, nylon offers the best bend recovery from strain held for an extended period of time.
While adequate for many purposes, the inventors herein have found that S the various nylons have property limitations which make their use less than optimat in abrasive filaments. Nylon abrasive filaments have limited stiffness and may lose their stiffness as filament temperature approaches 70C, and thus may not be suitable for remov~ng heavy scale or burrs when elevated filament temperatures are developed. Temperature resistance is critical in maintaining 10 filament stiffness. Elevated temperatures generally af~ect all nylon polymers in a similar way: stiffness~ as measured by the bending (tangent) modulus, decreases as temperature Increases. Heat generation is normally not a problem in long filament deburring where brush tool speeds are low. However, in short trim ;power brushes, tool pressure on the part and/or high speed in a dry ,~ -- 1 S eovi~nment can geneNté high temperatures at the filament tips.
Anoth limitadon of nglon abrasive filaments is that moisture from any - ~ source can have a noticeable affect on nylon filament brush tool performance.
Moisture affects filament stiffness and Ihereby tool aggressiveness. Nylon 6,12 - ~ retains stiffness better than other nylon materials and is 2-3 times sbffer than 20 other types of nylon in high humidity or when saturated with oils, solvents or when~ water is present.
In all abrasive fi~led polymeric filaments~ as the degree of abrasive loading increases, the tensile strength and flex fatigue resistance tend to decrease, due to insufficient binding of abrasive and polymer. Bending 25 moduius for a filament can be simply defined as the resistance to bending. This is an inherent characteristic of the polymer used for the abrasive filament.
- ` Bending~mddulus is generally independent of the filament diameter, and since the bending modulus of a family of abrasive filaments made from the same polymer will be the same, the ma n characteristics which affect filament 30 ~ ~sdffness~are the~diameter and length of the filament.

~,: , " ~

;, ~,~: .:
.:, , . ~ wo 93/l8890 2~L~8~9;~ Pcr/US93/01246 The abrasive cutting ability of abrasive-filled nylon filaments exhibits the distinct characteristic of cutting relatively well at the onset of the operation, followed by clear loss of abrasive action within about 1 hour. FIG. 7 shows the degradation in cutting ability of abrasive-filled nylon filaments, filled with a 5 typical aluminum oxide abrasive, when the filaments are attached to a hub to form a brush and the hub rotated so that the filaments strike (and therefore abrade) a stationary workpiece. FIG. 7 represents the cut obtained on a flat carbon steel (1018) plate as a function of time at a constant load of 1.36 Kg.
Equipment is typically designed to reverse the brush operation to restore the 10 abrasive action to its original level of activity. An abrupt increase in cut can be achieved if the brush is ~dressed". for example, by operating the brush against a wire screen. ThiS is shown at 2 hours 15 minutes in FIG. 7. Another problem associated with abrasive-filled nylon filaments is their poor flex ~atigue resistance. Over extended periods of operation the filaments tend to break near 15 tl~e point~of attachment to the hub, an inconvenience to the user, resulting in dec eased life and economic value of the brush.
The present invention addresses some of the problems mentioned above with abrasive-filled nylon and other filaments by presenting a composite - ~;ab~asive filament comprising a preformed corè coated with an abrasive-filled-20 thermoplastic elastomer. This approach centers on the idea that a preformed core coated with an abrasive sheath has a higher initial bending modulus, a more constant bending modulus as a function of time, temperature, humidity and chemical environment, and higher tensile strength than an abrasive-filled thermoplastic filament.
2S Composite~ abrasive filaments may allow for up to twice the loading of abrasive grains into the thermoplastic elastomer coating without exhibiting significantly reduced flex fatigue resistance cornpared with abrasive-filled nylon filaments. Much higher levels of initial and continued abrasive action were - observed than would have been expected from the increase in abrasive loading.
~ ~ ~30 This behavior relates to the compositional nature of the thermoplastic .

",, WO 93/18890 PCl /US93/Ol.~A6

2~Z809Z 4 elastomers as well as to the method of preparation of the composite abrasive filaments.
Experimentation with and production of abrasive filaments has a long history. Representative of the state of the art are U.S. Pat. Nos. 2,328,998;
2,643,945; 2,793,478; 2,920,947; 3,146,560; 3,260,582; 3,522,342;

3,547,608; 3,669,850; 3,696,563; 3,854,848; 4,097,246; 4,17~,440;

4,507,361; 4,627,950; 4,585,464; 4,866,888; and 5,068,142. other references include French Patent Application No. 2,624,773, and EPO publication 0 282,243.
The present invention is concerned with composite abrasive filaments comprising preformed cores at least partially coated with abrasive-filled thermoplastic elastomer compositions, which have the unexpected properties of allowing up to twice the loading of abrasive grains into the binding polymeric sheath while exhibiting many times the flex fatigue life compared to previously 15 known filaments. Much higher levels of abrasive action were observed ~han would have been expected from the simple increase in abrasive loading.
Thermoplastic elastomers are defined and reviewed in Thermoplastic Elastomers. A Comprehensive Review, edited by N.R. Legge, G. Holden and H.E. Schroeder, Hanser Publishers, New York, 1987, (referred to herein as 20 "Legge et al. "). Thermoplastic elastomers (as defined by Legge et al. and used herein~ are generally the reaction product of a low equivalent weight polyfunctional monomer and a high equivalent weight polyfunctional monomer, wherein the low equivalent weight polyfunctional monomer is capable on polymerization of forrning hard a segment (and, in con3unction with other hard 25 segments, crystalline hard regions or domains) and the high equivalent weightpolyfunctional monomer is capable on polymerization of producing soft, flexible chains connecting the hard regions or domains. This type of material has not been suggested for use in abrasive filaments. "Thermoplastic elastomers" differ from "thermoplastics" and "elastomers" (a generic term for substances 30 emula~ing natural rubber in that they stretch under tension, have a high tensile strength, retract rapidly, and substantially recover their original dimensions) in :

wo 93/1XX90 X~ 9;~ PCr/US93/01246 _ S _ that thermoplastic elastomers, upon heating above the melting temperature of the hard regions, form a homogeneous melt which can be processed by thermoplastic techniques (unlike elastomers), such as injection molding, extrusion, blow molding, and the like. Subsequent cooling leads again to

5 segregation of hard and soft regions resulting in a material having elastomeric properties, however, which does not occur with therrnoplastics.
Some commercia11y available therrnoplastic elastomers include segmented polyester thermoplastic elastomers, segmented polyurethane thermoplastic elastomers, segmented polyurethane thermoplastic elastomers 10 blended with other thermoplastic materials, segmented polyamide thermoplastic elastomers, and ionomeric thermoplastic elastomers.
"Segmented therrnoplastic elastomer"? as used hereinl refers to the sub-class of thermoplastic elastomers which are based on polymers which are the reaction product of a high equivalent weight polyfunctional monomer and a low 15 equivalent weight polyfunctiona monomer.
UIonomeric thermoplastic elastomers" refers to a sub-class of thermoplastic elastomers based on ionic polymers (ionomers). Ionomeric thermoplastic elastomers are composed of two or more flexible polymeric ~ ~-chains bound together at a plurality of positions by ionic associations or 20 clusters. The ionomers are typically prepared by copolymerization of a functionalized monomer with an olefinic unsaturated monomer, or direct.
functionalization of a preformed polymer. Carboxyl-functionalized ionomers are obtained by direct copolymerization of acrylic or methacrylic acid with ethylene9 styrene and similar comonomers by ~ree-radical copolymerization.
25 The resulting copolymer is generally available as the free acid, which can beneutralized to the degree desired with metal hydroxides, metal acet~tes, and similar salts.
Composite abrasive filaments of the present invention comprising preformed cores and abrasive-filled thermoplastic elastomer coatings produce 30 much higher levels of ini~ial cu~, m~untain thelr higher cutting abili~y once an :, wo 93/18890 2~ 809~ - 6 -equilibrium condition has been achieved, and are much more resistant to flex fatigue failure than abrasive-filled nylon filaments.

SUMMARY OF THE INVENTION
The present invention overcomes or reduces many of the problems associated with previously known abrasive filaments. In accordance with the present invention, a composite abrasive filament is presented which includes at ~ -least one preformed core at least partially coated with a thermoplastic elastomer having abrasive particles dispersed and adhered therein, the thermoplastic 10 elastomer and abrasive particles together comprising a hardened composition.
It is considered within the scope of the invention to include more than one thermoplastic elastomer in the hardened composition.
As used herein the term "hardened" refers to the physical state of the thormoplastic elastomer when the temperature of the thermoplastic elastomer is 15 below~;the melting or dissociation temperature of the hard regions (segmentedthermaplastic dastomers) or~lonic clusters (ionomeric thermoplastic elastomers), `;
as detérmined through standard tests such as American Society of Testing :, Mat:rials (ASTM) test D2117. The term can also be used des~ribe the room ~`
temp~rature (i.e. about 10 to about 40C) hardness (Shore D scalej of the 20 thermoplasdc elastomer. lt is preferred that the room temperature Shore D ~-durometer hardness of the thermoplastic elastomers used in the invention_be at least about 30, more preferably ranging from about 30 to about 90, as ;~
determined by ASTM D790. The term is not meant to include physical and/or chemical treatment of the thermoplastic elastomer/abrasive particle mixture to 25 increase îts hardness.
As used herein the term "composite abrasive filament" means an abrasive filament having the hardened composition above described over at least a portion, preferably over the entire surface of at least one preformed core, where the ratlo of the cross-sectional area of the hardened composition to that of thc preformed~core ranges from about 0.5:1 to about 300:1, preferably from ~:
about l:1 to about 10:1, more preferably from about 1:1 to about 3:1, the . .
: ~ :
- , :
, ' , , 2~;~8092 `
wo 93/18890 rcr/uss3/01246 - 7 - ;;
cross-sections defined by a plane perpendicular to the composite abrasive filament major axis. The composite abrasive filaments can be of any length desired, and can of course be round, oval, square, triangular, rectangular, polygonal, or multilobal (such as trilobal, tetralobal, and the like) in cross- ~;
5 secdon.
"Preformed core", as used herein1 means one or more core elements which are formed in a step separate from and prior to one or more coating steps, one of which coats the preformed core with abrasive-filled thermoplastic elastomer; in other words, a preformed core is not made simultaneously with 10 the hordened composition. The cross-section of the preformed core is not limited~ as to shape; ~however, preformed cores having substantially round or rectangular cross-sections have been found suitable.
The preformed core can be continuous Individual metallic wires, a multiplicity of continuous individual ~metallic wires, a multiplicity of non-15 metallic continuous filaments7 or a mixture of the latter t~,vo.
Preferred preformed cores indude~ single and multistranded metallic cores, e.g.,~ plain~carbon steels, stainbss steels, and copper. Other preferred ~~
~; prefonnd;coresinclude~a,multiplicity~ofnon-metallicfilamentse.g.,glass, '~
~ ~ ~ ca nics, and synthetic organic polymeric materials such as aramid, nylon,20~- polycstcr, and polyvinyl alcohol.
Segmented thennoplastic elastomers are preferably the condensation reacdon product of a high equivalent weight polyfunG~ional monomer having an average functionality of at least 2 and an equivalent weight of at least about 350, and a low equivalent weight polyfunctional monomer having an average 25 funcdonality of at least about 2 and an equivalent weight of less than about 300.
The high equivalent weight polyfunctional monomer is capabIe on polymerization of forming a soft segment, and the low equivalent weight ; ; polyfunctional monomer is capable on polymerization of forming a hard segment. Segmented thermoplastic e!astomers useful in the present invention 30 include p~lyester TPEs, polyurethane TPEs, polyimide TPEs, and silicone elas~mer/polyamide block~c~ymeric TPEs, with the low and high equivalent wo 93/18890 Pcr/US93/0~16 2~28092 weight polyfunctional monomers selected appropriately to produce the respective TPE.
The segmented TPEs preferably include "chain extenders", low molecular weight (typically having an equivalent weight less than 300) 5 compounds having from about 2 to 8 active hydrogen functionality, and which are known in the TPE art. Particularly preferred examples include ethylene diamine and 1 ,4-butanediol.
Blends of TPE and thermoplastic materials are also within the invention, allowing even greater flexibility in tailoring mechanical properties of composite ~
10 abrasive filaments of the invention. ~.
Another aspect of the invention is an abrasive article conlprising at least ~ ~`
one type of composite abrasive filament, preferably mounted to a substrate such as a hub adapted to be rotated at a high rate of revolution, the filaments ~ ~.
compnsing a preformed core at least partially coated with thermoplastic 15 elastom having abrasive particles dispersed and adhered therein, the the toplastic elastomer and abrasive particles together comprising a hardened com~osition .
A fur~ther aspect of the invention is a method of making a composite abrasive filament ~as above described), the method including the steps of: --(a) rendering a TPE molten and combining abrasive particles therewith;
(b) coating at least a portion of a pre~ormed core with a coating comprising the molten thermoplastic elastomer and abrasive particles; and (c) cooling the coating to a temperature sufficient to harden the molten thermoplastic elastomer and thus ~orm the hardened composition.
Preferred are methods wherein the TPE is segmented, wherein an extruder is used to render the TPE molten, and wherein the preformed core is 30 stranded metallic or stranded non-metallic matenal. As used herein the term "molten" means the physlcal state of the I~E when it is heated to a temperature ~.

~ ~ `

... wo 93/l8890 Z ~8C19;2 Pcr/Us93/01246 ~
g at least above the dissociation temperature of the hard regions or ionic clusters of the TPE under high shear mixing conditions.

BRIEF DESCRIPTlON OF THE DRAWING
S FIGS. 1~ each show an enlarged perspective view of one of four embodiments of composite abrasive filaments in accordance with the present invention, each having a portion of its abrasive-filled TPE hardened composition removed to show the preforrned core;
- FIG. 5 shows a perspective view of one embodiment of a brush tool (in 10 this case a rotary brush tool) incorporating composite abrasive filaments in ~:
accord~nce with the invention;
FIG. 6. is a cross-sectional view (reduced) of an extrusion die, with molten, abrasive-filled TPE and preformed core shown in phantom; j :
FIG. 7 is a bar ~raph which reveals the weîght in grams removed from 15 ~ a w~ie e ~(also ref rred to in: Ihe art as "cut") as a functlon of time for a rotating: brush tool having a~ plurality of prîor art nylon abrasive filaments; -:~
, FIGS. 8, 11, 13, 15, 21 and 23 :are bar graphs showing test results ~:~
comparing ~e amount of 1018 steel plate removcd as a function of time by ~: : brushes employing prior art nylon abrasive filaments with brushes employing :
. ~
20 composite abrasive filaments in accordance- with the present invention;
FIGS. 9, 12, 14, 16, 22 and 24 are bar graphs simîlar to FIGS B,11, 13, 15, 21, and 23, respectively, comparing the amount of 1008 steel perforated screen removed;
FIG. 10 is a ~raph which shows the effect of increased ab~asive loading 25 in TPE coabngs of the composlte abrasive filaments of the invention on the ability of rotating brushes incorporating same to abrade steel plate and screen;FIGS. 17-2Q are bar graphs which show comparative abrasion test results of rotating brushes which include composite abrasive filaments of the invention in brushes, the filaments having various types of abrasive particles in : 30 the hardened composition; and ~

, , , Wo 93/18890 ` PCr/US93/0!.?.~6 2 ~ 28092 FIGS. 25-28 are bar graphs which show test results of workpiece --removed as a function of power level for cylindrical brushes incorporating ~ `
composite abrasive filaments in accordance with the present invention.

D~SCRI~ION OF PREFERRED EMBODIMENTS
Composite Abrasive Filament Embodiments Four embodiments 10, 20, 30, and 40 of composite abrasive filaments in accordance with the present invention are illustrated in enlarged perspective ;
views in FlGS. 1-4, where in each embodiment it will be appreciated that a 10 portion of the hardened composition comprising TPE and abrasive particles has been removed to show the preformed cores.
FIG. 1 shows an enlarged perspective view of composite abrasive filament 10, having a preformed core 12 partially covered by a hardened composition 14 of TPE and abrasive particles 18. Preformed core 12 in this 15 embodiment is a 1 x 7 strandcd preformed core, formed for example from seven~ individual stainless steel wires 16. The TPE of the hardened composition 14 has- dispersed throughout and adhered therein a plurality of abrasive particles 18, such as aluminum oxide abrasive partides.
FIG. 2 shows an alternate composite abrasive filament embodiment, 20 wherein the preformed core 12a is formed from a plurality of parallel, - continuous metallic wires or non-metallic monofilaments 16a, while FIG.~3 shows a second alternate embodiment, wherein the preformed core 12b is a cable having 3 x 7 arrangement of three strands 16b, the strands in turn being each 1 x 7 strands of seven individual metallic wires or non-metallic 25 monofilaments as in FIG. 1. The composite abrasive filaments 20 and 30 each have a hardened composition 14 of thermoplastic elastomer having abrasive particles 18 dispersed and adhered therein partially covering preformed cores 12a and 12b, respectively. Regarding the embodiment shown in FIG.2, it should be noted that the hardened composition can be between the parallel 30 monofilaments of the preformed core, so that the individual monofilaments equally ~or ~unequally spaced ~apart.

"~ WO 93/1X890 2 ;~9~ PCI`/US93~01246 - 11 - . .
FIG. 4 shows an enlarged perspective view of another composite abrasive filament embodiment in accordance with the present invention.
Preformed core 12c is this embodiment is a single continuous wire or monofilament of, for example, stainless steel or glass fiber. As with previous S embodiments, core 12c has thereon a hardened composition 14 of TPE having dispersed and adhered therein a plurality of abrasive particles 18.
Preforrned core diameters for composite abrasive filaments of the present invention used on typicals hand-held tools are preferably at least about0.1 mm, while the composite abrasive filaments themselves preferably have a 10 diameter ranging from about 1.0 mm to about 2.0 mm. ~;
Composite abrasive filaments of the invention having a diameter ranging from about 0.75 mm to about 1.5 mm have an ultimate breaking force (measured using a standard tensile tester known under the trade designation "Instron" Model TM, according to the test described below) of at least about 15 2.0 kg, a 50% fatigue failure resistance (i.e. the time require for 50% of the filaments in a given brush to detach from the brush at given conditions) of at least about ~S minutes; and an abrasion efficiency (i.e. weight of workpiece removed ~per weight of filament lost) on cold rolled steel (1018) plate of at leasst about 2. As may be seen by the examples herein below, balancing these 20 preferences may be workpiece dependent.

Thermoplastic El~tomers Segmented TPEs useful in the composite abrasive filaments of the present inv~ntion generally and preferably comprise the r~SSction prodsuct of a 25 high equivalent weight Spolyfunctional monomer having a functionality of at least about 2 and an equivalent weight of at least about 350 adapted to form a soft segment upon polymerization, and a relatively low equivalent weight polyfunctional monomer having a functionality of at most about 2 and an equivalent weight of at most about 300, adapted lO form a hard segment upon 30 polymerization.

wo 93/lX890 - Pcr/US93/Ol~

Z~ Chain extenders are typically used ;n segmented thermoplastic elastomers to increase the hard segment and hard domain size and thus provide one mechanism to alter the physical properties of the resultant segmented TPE. -Chain extenders useful in the segmented TPEs of the present invention 5 preferably have an active hydrogen functionality ranging from about 2 to 8, preferably from about 2 to 4, and more preferably from about 2 to 3, and an equivaleni weight less than about 300, more preferably less than about 200.
Well suited chain extenders are the linear glycols such as ethylene glycol, 1,4-butanediol, 1,6-hexanediol, and hydroquinone bis(2-hydroxyethyl) ether.
Segmented TPEs useful in the composite abrasive filaments of the present invention preferably comprise segmented polyester TPEs, segmented polyurethane TPEs, and segmented polyamide TPEs. The low and high equivalent weight polyfunctional monomers are variously chosen to produce one of the above segmented TPEs. For example, if the TPE comprises a segmented 15 polyester, such as the segmented copoly(etherester)s, the low and high equivaient weight polyfunctional monomers are preferably poly(tetramethylene terepht~h~alatej and poly(tetramethylene oxide), respectively. If the TPE
comFises a segmented polyurethane, the low equivalent weight polyfunctional monom is preferably a polyfunctional isocyanate and the high equivalent 20 weight polyfunctional monomer is preferably a polyfunctional amine.
The weight percent of low equivalent weight polyfunctional monomer in the tota1 weight of monomers which react to produce segmented TPEs preferably ranges from about 20 to about 60 percent, more preferably ranging from about 20 to about 40 percent.
Ionomers useful in forrning ionomeric TPEs typically and preferably comprise the reaction product of a functionalized monomer with an olefinic unsaturated monomer, or comprise a polyfunctionalized preformed polymer.
- Within the terms "ionomeric TPEs" and "ionomers" are included anionomers, cationomers, and zwitterionomers.

~```',~'`'`~`'`'``;'`'.'' wo 93/1X890 231 ;~8C~9;~ Pcr/uss3/01246 TPEs (segmented and ionomeric) useful in c~mposite abrasive filaments of the invendon preferably have Shore D durl)meter hardness values ranging from about 30 to about 90, more preferably r~nging from about 50 to about 80.
The mechanical properties of segmented thermoplastic elastomers (such S as tensile strength and elongation at break) are dependent upon several factors.
The proportion of the hard segments in the polymers which form the TPEs, their chemical composition, their molecular weight distribution, the method of preparation, and the thermal history of the TPE all affect the degree of hard domain formation. Increasing the proportion of the low equivalent weight lO polyfunctional monomer tends to increase the hardness and the modulus of the resultant TPE while decreasing the ultimate elongation. ;
The upper use temperature of segmented TPEs is dependent upon the softening or melting point of the low equivalent weight polyfunctional monomer comprising the hard segments. For long term aging, the stability of the high 15 equivalent weight polyfunctional monomer comprising the soft segment is also important. At elevated temperatures and with a lower percentage of hard segments which can contribute to hard domains, bending modulus and tensile strength of the TPE are generally reduced. `
Preferred TPEs having the above properties and useful in the invention 20 include those formed from segmented polyesters represented by general formula -zol ~c_o_~c~z~_o~c~c-ot~c)l~) ol and mixtures thereof wherein:
d and e are integers each ranging from about 2 to about 6, and wherein d and e may be the same or different, but not differing by more than I integer; and `

WO 93~18890 . PCI~US93/0~6 - 14 - , x and y are integers selected so that the resulting segmented Z~LZ809Z polyester TPE has a Shore D durometer hardness ranging from about 30 to about 90.
Total molecular weight (number average) of segmented polyesters within 5 general formula I ranges from about 20,000 to about 30,000; x ranges from about 110 to about 125; and y ranges from about 30 to about 115, more preferably from about S to about 70.
Preferred ionomers used to form ionomeric TPEs useful in the invention comprise the copolymerization reaction product of a functionalized monomer 10 and an olefinic unsaturated monomer, the ionomers being represented by general forrnula II

R;~CH2 CH2~ (cH2f~R~ (II) D ~1 ~

and mixtures thereof wherein: ;:
Rl, R2, and R3 which may be the same or different and a~e selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, and substituted aryl;
m and n are integers which may be the same or different which are selected so that the weight percentage of the ~unctionalized monomer ranges from about 3 to about 25 weight percent of the total ionomer weight and so that the resulting ionomeric TPE has a Shore D durometer ranging from about 3(1 to about 90;
D is a functional group selected from the group consisting of Coo and S03~; and :~

.- ~ wo 93/18890 z~ 92 Pcr/lJs93/01246 M is selected from the group consisting of Na, Zn, K, Li, Mg, Sr, and Pb.
Particularly preferred are those ionomers represented by general formula II
wherein Rl = R2 = R3--CH3 and D = COO. A particularly preferred 5 ionomer is when Rl = CH3, D = COO, and M = Na, such an ionomer being commercially available, for example that known under the trade designation "Surlyn 8550" (du Pont).
The values of m and n are normally not given by manufacturers but are selected to provide the resulting ionomeric IPE with a room temperature Shore 10 D durometer ranging from about 30 to about 90. Alternatively, m and n may be characterized as providing the molten ionomeric TPE with a flow rate ~forrnerly termed "melt index" in the art) ranging from about 1 gm/lO mins to about lO gmstlO mins (as per ASTM test Dl238-86, condition l90/2. 16, formerly Dl238-79, condition E). Briefly, the test involves placing a sample 15 within the bore of a vertical, heated cylinder which is fitted with an orifice at the bottom of the ~ore. A weighted piston is then placed within the cylinder bore, and the amount in grarns of moiten polymer exiting the cylinder through the orifice is recorded in grams for a lO minute period.
The functionaIized monomer may be selected from acrylic acid9 20 methacrylic acid, vinyl acetate, and the like, and copolymers thereof, with acrylic and methacrylic acid particularly preferred.
The olefinic monomer may be selected from ethylene, propylene, butadiene, styrene, and the like, and copolymers thereof, with ethylene being the olefinic monomer of choice due to its availability and relatively low cost.
The functionalized monomer and olefinic monomer are typically and preferable directly copolymerized using free radicals, such methods being well known in the art and needing no further explanation herein.
Particularly preferred segmented polyamides useful in making segmented polyamide TPEs useful in the invention are those segmented polyamides 30 represented by general formula III

wo 93~18890 PCI`/US93/01 -- 16 -- ! `
2~Z809Z
o o HO---C--PA--C--O--PE--C)----H ( I~
Z

and mixtures thereof, wherein:
PA = a difunctional polyamide having equivalent weight less than about 300;
PE = a dihydroxypolyether having equivalent weight of at least 350 and comprising polymers selected from the group consisting of dihydroxypolyoxyethylene, dihydroxypolyoxypropylene, and dihydroxypolyoxytetramethylene; and z = an integer selected to provide the resulting segment~
polyamide TPE with a Shore D durometer hardness ranging from u -: about 30 to about 90.
Segmented polyamides within~formula III are commercially available, such as~ those hlown under the trade designation "Pebax", available from Atochèm~ Group of Elf Aquitaine, with the 63 and 70 Shore D durometer 15 versions being particularly preferred in the present invention.
Although values of z are proprietary to the manufacturers, and polymers within general ~ormula III may be characterized according to hardness, they may alternati~ely be characterized according to their melt flow rate (as described above), with values ranging from about 1 cjm/10 min to about lû
cjm/10 min being preferred (ASTM 1238-86, 1~0/2.16~.
Particularly preferred segmented polyurethanes useful in ma}~ng polyurethane TPEs useful in the invention are those segmented polyurethanes I
represented by general formula IV and mixtures thereof wherein:
polyol = a polyester polyol or polyether polyol having an average molecular weight ranging from a~out 600 to about 4000;
and ,'~': :
,:, ,.,,:

-~ WO 93/18890 2~C)9Z PCI~US93/01246 t--an integer selected to provide the resulting segmented polyurethane TPE with a Shore D durometer hardness ranging from about 30 to about 90.

80 ¦ --N~CN~3N 0--tCU; ) 0 C~ (IV) --N~CH~ C--O--(p~l- ol ) ~ OEI

The value of "t" is chosen relative to the moleeular weight of the polyol to give a range of ~olecular weights; typically and preferably, the number aYerage molecular weight of segmented polyurethanes represented by general fonnula IV ranges from about 35,000 to about 45,000.
In general, segmented polyurethanes may be made by mixing the first 10 and second polyfunctional monomers and chain extender together at tempeIatures above about ~C. Preferably, the ratio of isocyanate functional groups to isocyanate reactivë gr~ups ranges from about 0.96 to about 1.1.
Values below about 0.96 result in polymers of insufficient molecular weight, while above about 1.1 thermoplastic processing becomes di~ficult dlle to 1~ excessive crosslinking reactions.
As mentioned pre~iously, blends of TPEs and other polymers have also proven useful, such as the polyurethane/acrylonitrile-butadiene-styrene blends known under the trade designation "Prevail", grades 3050, 3100, and 3150, all from Dow chemical. Grade 3050 has a melt flow rate (ASTM-1238-86, 20 230/2.16) of 26 gm/10 min, and a Shore D hardness of about 62.
Block copolymers regarded by those skilled in the plastics processing art as TPEs~ including the elastomeric copolymers of silicones an,d polyimides, may also prove useful in composite abrasive filaments of the invention.
,, ~'~ ~ ~,~ , ~,~

WO 93/18890 PCl`/~ lS93/01~
2~ 28~92 - 18 - ` i Commercially available elastomeric copolymers of thermoplastic silicones and polyimides include those known under the trade designation "Siltem STM-1500", from GE Silicones.
Each of the polymers within formulas I-IV as shown above are now 5 discussed in greater detail.

Se~mented Polyesters As noted above, if the TPE is based on a segmented polyester, such as the segmented copoly(etherester) as shown in formula I, the low and high 10 equivaIent weight polyfunctional monomers are preferably based on poly(tetramethylene terephthalate) which forms the hard segment upon polymerization and poly(tetramethylene oxide) which forms the soft segment upon polymenzation, respecovely. The poly(ether) component of the copoly(etherester) is preferably derived from a-hydro-cl~-15 hydroxyoligo(tetramethylene oxide) of number average molecular weight - rang~ing~ from about 1,000 to about 2,000. The copoly(ester) component of the copoly(~ercster) is p eferably based on poly(tetramethylene terephthalate) which forms hard segments upon polymerization, having average molecular weights~ranging from about 600 to about 3,000. The molecular weight for 20 copoly(etherester) polyesters within formula I preferably ranges from about - ~ 20,000 to about 40,000.

Ionomers Ionomers which may behave as ionomeric TPEs and thus useful in the 25 present invention, such as those ionomers known under the trade designation "SURLYN" lformula II), are preferably prepared by copolymerization of a functionalized monomer and an olefinic unsaturated monomer, or by direct ~ functionalization of a preformed polymer, as previously noted. Ionomers - ~; within formula II are particularly preferred for forming ionomeric TPEs for use 30 in hardened compositions in composito abrasive filaments of the invention. The 1 argé quantities of commercial quality ethylene/methacrylic acid copolymers, , . . .

~- ~ WO 93/lX890 PCl'/US93/01246 -- 19 -- ! , for example containing between about S and about 20 weight percent 2~2~9;~
methacrylic acid component, makes these ionomers particularly useful in the present invention.
M in formula II is typically and preferably chosen from sodium (Na) 5 and zinc (Zn), although ionomers using potassium (~C), lithium (Li), magnesium(Mg), strontium (Sr) and lead (Pb) are considered within the scope of formula II. -.''`"

Segmented Polyamides `
Polyamides within formula III and useful forming segmented polyamide ~ -TPEs for use in the invention are typically described as polyether block amides (or "PEBA"), wherein the latter may be obtained by the molten state polycondensation reaction of dihydroxypolyether blocks and dicarboxylic acid-based polyamide blocks as shown in formula III (wherein PA represents 15 "polyamide" and~PE r~plesents "polyeth"). Dicarboxylic polyamide blocks may be~ produced by the reaction of polyamide precursors with a dicarboxylic acid chain limiter. The~ reaction IS~ prefe~ably carried out at high temperature~prefel~ably higher than 230C) and preferably under pressure (up to 2.5 Mpa).
The molecular weight of the polyamide block is typically contro!led by the 20 amount of dain limiter.
The polyamide precursor can be selected from amino acids such as aminoundecanoic acid and aminododecanoic acid; lactams, such as caprolactam, ~-lauryl lactam, and the lik~); dicarboxcylic acids (such as adipic acid, azelaic a~id, dodecanoic acid, and the like); and diamines (such as hexamethylene 25 diamine, dodecamethylene diamine, and the like).
The dihydroxypolyether blocks may be produced from polyether precursors by either of two different reactions: an ionic polymerization of ethylene oxide and propylene oxide to form dihydroxypolyoxyethylene and ~`dihydroxypolyoxypropylene polyether precursors; and cationic polymerization 30 of tetrahydrofuran for producing dihydroxypolyoxytetramethylene polyether p~cursors.

~ ' ,' '~-, ~; ` ` -WO 93/18890 PCI`/US93/01?~1~b 2~Z~09Z . - 20 --The polyether block arnides are then produced by block copolymerization of the polyamide precursors and dihydroxypolyether precursors. The block copolymerization is a polyesterification, typically achieved at high temperature (preferably ranging from 230 to 280C) under 5 vacuum (10 to 1,400 Pa) and the use of an appropriate catalyst such as Ti(OR)4, where R is a short chain alkyl. It is also generally necessary to introduce additives such as an antioxidant and/or optical brighteners during polymerization .
The structure of the resu1ting polyether block amides comprises linear, 10 regular chains of rigid polyamide segments and flexible polyether segments.
Since polyamide and polyether segments are not miscible polyether block amides such as those represented by formula III present a "biphasic" structure wherein each segment offers its own proper~ies to the polymer.

I5 Segmented Polyurethanes Segmented polyurethane TPEs useful in the present invention are prefelably formed from segmented polyurethanes within formula IV, which are comprised of a high equivalent weight polyfunctional monomer and a low equivalent weight polyfunctional monomer as above described, and may also 20 include a low molecular weight chain extender, also as above described. In thermoplastic polyurethane elastomers, the hard segment is formed by addition of the chain extender, for example, 1 ,4-butane diol, to a diisocyanate, for example, 4,4'-diphenylmethane diisocyante ~MDI). The soft segment consists of long, flexible polyether or polyester polymeric chains which connect two or 25 more hard segments. At room temperature, the low melting soft segments are incompatible with the polar, high melting hard segments, which leads to a microphase separation.
Polyurethanes useful in forming segmented polyurethane TP~s are generally made from long chain polyols having an average molecular weight 30 ranging from about 600 to 4,000 (high equivalent weight polyfunctional monomer), chain extenders with a molecular weight ranging from about 60 to - WO 93/188g~ PCI`/US93/01246 - 21 - ~.28~P92 about 400, and polyisocyanates (low equivalent weight polyfunctional monomer). Preferred long chain polyols are the hydroxyl terminated polyesters and the hydroxyl terminated polyethers.
A preferred hydroxyl terminated polyester is made from adipic acid and 5 an excess of a glycol such as ethylene glycol, 1,4-butanediol, l,~hexanediol, neopentyl glycol, or mixtures of these diols.
Long chain polyether polyols useful in making polyurethanes within formula IV useful in making segmented polyurethane TPEs useful in composite abrasive filaments of the invention are preferably of two classes: the 10 poly(oxypropylene)glycols and~the poly(oxytetramethylene)glycols. The former glycols may be made~by the~base catalyzed addition of propylene oxide and/or `
ethylene-oxide to bifunctional initiators, for example, propylene glycol or water, while the latter may be made by cationic polymerization of tetrahydrofuran. Both of ~these classes of polyethers have a functionality of 15 about~2. The mixed polye~ers of tetrahydrofuran and ethylene or propylene - oxi~de may also ~be e~fectivdy used as the sofl segment in the polyurethane TPE.
ln~contrast to other polyurethanes, only a few polyisocyanates are - suitable for~producing thermoplastic dastomer polyurethanes. The most useful ~prefei~ polyisocyanate is MDI, ~mentioned above. Others includ~e 20 he~xarnethylene diisocyanate (HDI), l-isocyanato-3-isocyanatomethyl-3,5,5-~- ~ trimethylcyclohexane ;aPDI); 2,4 and 2,6-toluene diisocyanate (IDI); 1,4 benzene diisocyanate, and trans-cyclohexane-l,4-diisocyanate.

Preformed Cores Preformed core materials useful in the present invention can be envisioned as an abrasive coadng substrate that can be selected or modified in its surface characteristics, mechanical properties, and environmental stability properties. The preformed core material is preferably selected or capable of being modified so that its surface has the ability to achieve adhesion between 30 the core and thermoplastic dastomer coating. Important mechanical properties ;" ~ , ~

,, ,,, ~ , :- . : :

WO 93/18890 PCI/US93/Ol~<~

include tensile strength and flex fatigue resistance whjle operating under various chemicaL thermal and atmospheric conditions.
Preformed cores useful in the composite abrasive filaments of the present invention include: metal wire such as stainless steell copper, and the 5 like; inorganic fibers such as glass and ceramic fibers; synthetic fibers, such as aramid, rayon, and the like; natural fibers such as cotton, and mixtures of these. Although continuous monofilaments may be used, preferred are stranded, cable and yarn versions of these materials. "Stranded" as used herein refers to twisted together wires while "yarn" refers to twisted together non-10 metallic monofilaments. Typical arrangements include 1 x 3, 1 x 7, 1 x 19,and 3 x 7 arrangements, wherein the first number refers to the number of strands or yarns and the second number refers to the number of individual monofilaments or wires twisted together in each yarn or strand. "Cable" refers to two or more strands twisted together, while "plied yarns" refers to two or 15 more yarns twisted together, preferably having the opposite direction of twist ~ compared with the cables (for example, if the cables are twisted together "right - handed" the plied yarn may be twisted together "left handed"). Alternatively, the performed core may be in the form of untwisted continuous wires or monofilaments. Preferred yarns include yarns of glass fibers, ceramic fibers, 20 aramid fibers, nylon fibers, polyethylene terephthalate fibas, cotton fibers, plied version thereof, and mixtures thereof.
The diameter of the preformed core is preferably at least about 0.01 mm, more preferably ranging from about 0.1 mm to about 0.7 mm, although there is actually no upper limit to the diameter other than that imposed by 25 currently known methods of making composite abrasive filaments.

Abrasive Particles Abrasive particles are preferably dispersed throughout and adhered within the hardened TPE coating. Abrasive particles useful in the composite 30 abrasive filaments of the present invention may be individual ~brasive grains or agglomerates of individual abrasive particles. Suitable agglomerated abrasive , ~ .

~-. WO 93/18890 rCr/US93/01246 - 23 - 2~8~9;~
particles are described in U.S. Pat. Nos. 4,652,275 and 4,799,939. The abrasive particles may be of any known abrasive material commonly used in the abrasives art. Preferably, the abrasive particles have a hardness of greater than about 7 Mohs, most preferably greater than about 9 Mohs. Examples of 5 suitable abrasive par~cles include individual silicon carbide abrasive particles (including refractory coated silicon carbide abrasive particles), fused aluminumoxide, heat treated fused aluminum oxide, alumina zirconia, cubic boron nitride, garnet, pumice, sand, emery, mica, corundum, quartz, diamond, boron carbide, fused a1umina, sintered alumina, alpha alumina-based ceramic material.
The abrasive particles are preferably present in the hardened TPE
coating at a weight percent (per total weight of TPE and abrasive particles) ranging from abo~ut 0.1 to~about 65 weight percent, more preferably from about ,~
3 to about 60 weight percent.
The size of the abrasive ~articles incorporated into the hardened TPE
-~ 15 coating~dependsonthe~intendeduseofthecompositefilaments. For appliattions requiring~cutting or rough fimshing, larger abrasive parhdes are - preferred, ~while ab:sive particles having smaller size are prefe red for finishing applications. PreferaUy,~ the average diameter of the abrasive particles is no more than about 1!2 the diameter of the composite abrasive 20~ filament, more preferably no more than about 1/3 of the diameter of the composite abrasive filament.
~ The surface of the abrasive particles (or a portion of their surface, or a portion of the particles but their whole surface) may be treated with coupling agents to enhance adhesion to and dispersibility in the molten TPE. Examples 25 of suitable coupling agents include silane, zirco-aluminate, and titanate coupling agents.
~ i ~
Abrasive Articles Composite abrasive filaments of the invention may be incorporated into 30 a wide va~iety of b~ushes, either assembled to form an open, lofty abrasive pad, or attached to various~substrates. FIG. 5 shows one embodiment of a wheel ., ~

, . . .

WO 93/18890 PCl`/US93/01%~

Z~ -- 24 -brush 50 within the invention having a plurality of composite abrasive filaments51 glued or otherwise attached to a hub 52. A construction of such a brush is described in "Test Brush Construction IIn, below.
The composite abrasive filaments of the invention can be incorporated S into brushes of many types and for myriad uses, such as cleaning, deburring, radiusing, imparting decorative finishes onto metal, plastic, and glass substrates, and like uses. Brush types include wheel brushes, cylinder brushes (such as printed circuit cleaning brushes), mini-grinder brushes, floor scrubbing brushes, cup brushes, end brushes, flared cup end brushes, circular flared end 10 cup bNshes, coated cup and variable trim end brushes, encapsulated end brushes, pilot bonding brushes, tube brushes of various shapes, coil spring brushes, flue cleaning brushes, chimney and duct brushes, and the like. The filaments in any one brush can of course be the same or different.

Method of Making Composite Abrasive Filaments Composite abrasive filaments in accordance with the present invention can be made by any of a variety of processes, including passing one or more preformed cores through a die in which molten, abrasive-filled TPE is coated onto the preformed cores as they move through the die, spray coating abrasive-20 filled, molten TPE onto a preformed core, or by passing a preformed corethrough a bath of molten TPE~ followed by applying abrasive particles to Ihe molten TPE coating. (Alternatively, the abrasive particles could be in the bath of molten TPE.) Abrasive particles may be applied to a TPE-coated core by projecting the abrasive grains toward the TPE-coated preformed core by force, 25 such as electrostatic force. However, the preferred method is the first mentioned one, wherein one or more preformed cores are passed through a die ,, , ~ I j , which at least partially coats the preformed cores with molten, abrasive-filled TPE, and the molten TPE cooled to form the hardened composition.
In one preferred method in accordance with the invention, a die 60 such 30 as that shown in FIG. 6 is attached to the exit of an extruder, an extruder being one preferred technique of rendenng the TPE molten and mixing the abrasive ~ W~ 93/18890 PCl`/US93/01246 - 25 - 2~28(:~9~
particles into the molten TPE. The apparatus and method of Nungesser et al., U.S. Pat. No. 3,522,342, is one preferred method. FIG. 6 shows molten, abrasive-filled TPE (or abrasive-filled TPEJthermoplastic polymer blend, as desired) in phantom at 62, and a single preformed core 61, also in phantom, it S being recognized by those skilled in the art that the polymer melt and preformed core flow from left to right as shown. The abrasive-filled, TPE-coated preformed core 63 exits die 60 as shown. Shown at 64 is a screw attachment for attaching the die to an extruder (not shown). Suitable modifications to die 60 may be made to pass a plurality of preformed cores, 10 these modifications being within the skill of the artisan.
For each TPE the zone temperatures of the extNder and die temperature are preferably set at the tempesatures commercially recommended for each TPE
(see Table A), the main limitation being the melting or dissociation temperatureof the hard domains or bnic dusters of the TPE. Preferred extruder zone and lS die temperatures are listed in Table A. The extruder (or other TPE melt rendering means, such as a heated vessel and the like) preferably heats the TPE ~-above t~e hard domain or ionic cluster melting or dissociation temperature (which may have a range that can change with type and grade of the TPE) and pushes mdten TPE through a heated die.
Abrasive panicles may be added to the molten TPE through a feed port in the extruder into the molten TPE mass, preferably at point early enoug~ to afford adequate dispersal of abrasive particles throughout the molten TPE.
Alternatively, abrasive particles may be distributed in the molten TPE coating via a second step (i.e. after the pre~ormed core has been coated with rnolten 25 TPE), such as by electrostatic coating.

WO 93/1X890 PCI~US93/017.~

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.~ wo 93/18890 231 ~8(~92 Pcr/uss3/01246 A cold water quench is located immediately downstream of the die through which the molten TPE-coated preformed core passes to achieve rapid -cooling of the molten TPE to form a hardened composition comprising TPE and abrasive particles on the preformed core prior to windup of the coated -5 preformed core onto a windup roll. A process wherein multiple preformed cores are coated simultaneously may be preferably from the standpoint of mass ``-producing composite abrasive filaments, which may be accomplished using a manifold arrangement. In this case, more than one wind up roll may be ~`
required.
Conventional dies may require a pulley mechanism having vertical and horizontal adjustments placed immediately downstream of the cold water quench to provide means for centering the preformed core in the die and provide concentric coatings. of late, cornmercially available dies provide this centering function without the use of a separate mechanism. A die known under the trade 15 ~ name LOVOL-, available from Genca Die, Ciear~val~r, Florida, having four hdicoid fixed center arrangelnent, gives acceptable abrasive particle dispersionin the~molten TPE, substandally concentric coatings, and is easier to rethread with prefonned core material when prefonned core material is changed.
The abrasive-filled TPE coadng thickness may be changed using 20 mechanical inserts into the die. Thickness of the coating may also be adjusted - ~ somewhat by the speed that the preformed core passes through the die, higher `~ speeds yielding somewhat thimler TPE coatings. A preformed core speed of ranging from about 30 ~o about l00 re/min has proved preferable, more preferably from about 30 to about 45 relmin, ~or pilot scale operations, while 25 production speeds may be considerably higher, such as 300 re/min in large scale operations.
The hardened, abrasive-filled TP~-coated preformed core may be cut to individual composite abrasive filaments having the desired length. There is no need to orient the filaments to increase their tensile strength prior to use.
More detailed descriptions of the method of fabricatin~.composite abrashe ~filaments and methods~ of zbrading flat plate and flat screen wo 93/18890 pcr/us93/ol?~6 Z~28~92 - 28 -workI~ieces, along with performance test results, are given in the Examples which follow.

EXAMPLES
S The following examples are given as illustrations of the invention and are not intended as limitations thereof. In all examples, all parts and percentages are by weight unless otherwise stated. "P" refers to heat treated abrasive particles where used in conjunction with an abrasive particle designation, while the "grade" of abrasive particles refers to that used by the 10 Grinding Wheel Institute (ANSI ASC B74.18-1984). "CRS" refers to "cold rolled steeln.

TEST METHODS
Fatigue Failure Resistance This test was used to evaluate fatigue failure of composite abrasive fi1aments, t}le results of which can be used to predict relative usable life of a brush made from the composite abrasive filaments of the invention. The test procedure used was published and descAbed in Technical Bulletin No. 6, "Fatigue Resistance and Some of the Factors That Affect Flex Life of Brush 20 Filling Materials", February, 1978, by du Pont, Plastic Products and Resins Department, Code # E-19743. The test procedure was followed exa~tly, yvith the exc~ption that the filament holding device on the tester was changed to fourchucks, each of which could be adjusted to firmly grasp one composite abrasive filament. In this test, the four chucks were affixed to a drive sha~t, each of 25 which was used to secure an individual composite abrasive filament or controlfilament. The chucks were mounted 90 apart with each being spaced 50 mm from the center of the drive shaft. The drive shaft was operated at 500 rpm.
As per the test procedure, the interference between the filaments and the impactbar was adjusted, depending upon the filament diameter. For a 1.02 mm 30 diameter filament, the interference was 12.22 mm; for 1.14 mm filament, the interfennce was 13.21 mm; for a 1.27 mm filament, the interference was o 93/18X90 2~ 9~ PCI/US93/01246 16.51; and for a 1.40 mm filament, the interference was adjusted to 18.16 mm.
After securing four identical test filaments to the drive shaft, the drive shaftwas rotated and the time required to cause 50% of the filaments to break was recorded. This value is reported in Table 4 for Examples 1-27 and 5 Comparative Examples A-F. ~ -Test Brush Construction I
Composite abrasive filaments were used to form abrasive brushes by attaching one end of the composite abrasive filaments to a cast aluminum, 10 machined, two-part hub. The first part of the cast aluminum, machined hub consisted of a 5 mm thick aluminum disc having a 32 mm center holet a 102 mm outside diameter, and had a raised square cross-sectional surface at the periphery that was raised 4 mm. The second part of the cast aluminum hub was machined from a 19 mm thick cast aluminum disc, also having a 32 mm 15 center hole with a 102 mm outside diameter. The second part of the east aluminum hub was machined to be S mm thick, with the exception of three circular raised surfaces on one side of the disc, each concentric with the center hole: an outer, an intermediate, and an inner circular raised surface, all threeraised circular surfaces parallel to the disc major surfaces. The outer circular20 raised surface had a squa~e cross-section of 4 mm by 4 mm and an outside edgediameter of 102 mm. The intermediate circular raised surface had an out~ide edge diameter of 73 mm and an inside edge diameter of 68 mm, and was raised 13 mm above the disc major surface. The annulus formed by one of the disc major surface and the intermediate raised surface was rnachined to produce 25 eight equally si~ed and spaced bores extending radially through the annulus, each bore being 9 mm in diameter with the spacing between adjacent bores being about 3 mm. These bores defined holes into which composite abrasive filaments were subsequently placed. The inner circular, raised surface had an inside edge diameter of 32 rnm which, when the two hub parts were mated, 30 defined the center hole of the hub. The inner raised surface outer edge had adiameter (measured from the hub center) of 44 mm and was raised 13 mm ~' wo 93/18890 PC~/US93/01~?~6 2~Z8C~92 - 30 above the disc major surface. The inner raised surface and intermediate raised surface of the second hub disc defined the plane against which the first hub part was placed. The raised square cross sections of the first and second hub parts opposed each other.
One end of approximately 125 to 150 composite abrasive filaments, each 83 mm long, were placed into each of the eight bores. Sufficient number of filaments were placed in each bore to essentially fill each bore. A two-part epoxy adhesive liquid resin composition (combination of the epoxy "~pi-Rez"
WD-510, from Rhone-Poulenc? and the amine "Jeffamine" D-230, available 10 from Texaco Chemical Company, Bellaire, Texas) was placed over the filament end which protruded into the bore. The first part of the machined aluminum hub was secured to the second part using four screws, 4 mm in diameter, through four holes equally spaced 42 mm from the center of the machined aluminum hub. This caused the composite abrasive filaments to slightly fan out 15 with a resultant filarnent trim length of about 50 mm. After being held for approximately 24 hours at room temperature (about 25C, to allow the epoxy resin to harden), followed by a post cure at about 60C for about 1 hour, the composite abrasive filament brushes were ready for subsequent evaluations.
The brushes had a 32 mm center hole and approximately 200 mm outside 20 diameter.

Test Brush Construction II
A mold was fabricated so that composite abrasive filaments of the invention could be used to form abrasive brushes as shown in FIG. 5. A round 25 base plate was fabricated with a 3.18 cm diameter center through hole which was adapted to accept a solid, cylindrical core piece having outer diameter slightly less than 3.18 cm. Slots were machined into one surface of the base plate to create a radial pattern so that thin metal spacers could be inserted therein. The slots extended radially, starting from a point about 5 cm from the 30 center through hole and extending to the periphery of the plate. A right cylinder (200 mm I.D.) was then fastened to the surface of the base plate ~: .

,-- wo 93/1X890 2~28~92 rcr/uss3/0l246 having the slots so that the hole in the base plate and the cylinder were concentric.
The spacers were then put in the slots, the solid, cylindrical core piece inserted in the through hole, and a multiplicity of composite abrasive filaments5 having length equal to the slot length plus about 5 cm were then aligned within the spaces left between the spacers. T~.e spacers provided a method to uniform1y and closely distribute the composite abrasive filaments radially with a predetermined length which could then be held firmly with a clamp ring, which fitted over the end of the filaments pointing toward the center through hole.
A polymeric cast hub was then formed by pouring a liquid, two-part `~
epoxy resin (trade designation "DP-420", from 3M) into the center cavity formed between the solid, cylindrical center core piece and the clamp ring, at about 50C. When the res-n was fully cured, the brush was removed from the device and then tested in Examples 25-27 and Comparative Example F.

Flat Plate Abrasion Tests Composite abrasive filament-containing brushes were weighed and ~rately mounted on a shaft connected to a 2.24 Kw (3hp) motor which operated at 1750 rpm. 1018 CRS steel plates, 100 mm square by 20 approximately 6 mm thick, were weighed and then brought in contact with each brush with a force of 13.3 Pa. At 15 minute inten~als, the test brushes ~d steel plates were again weighed to determine the weight loss of the steel platesand weight loss of the test brushes. After 8 test periods of 15 minutes each (120 minutes total) the tests were concluded and the total cut (steel plate weight 25 loss) was calculated. This value was divided by 2 to give average gr~ms cut per hour by each brush. The efficiency (~7) of the brushes was calculated by dividing the total plate weight loss by~the total composite abrasive filament weight loss. Results are reported in Table 4.

:' .

wo 93/18890 - 32 - PCr/uSs3/01 X~ 2809Z
Perforated Screen Abrasion Tests Brushes were tested for abrasion of perforated steel. In this eest, 50 X
150 mm pieces of 16 gauge 1008 CRS steel perforated screen having approximately 4 mm diameter staggered holes with 46% open and having stock S pattern number 401, commercially available from Harrington and King Perforating Company, Inc., Chicago, Illinois, were abraded, a double layer of the screen used in each test. Results are reported in Table 4.

Composite Abrasive Filament Tensile Stren~th Composite abrasive filaments of the invention were evaluated for their tensile strongth by measuring the force required to break a 100 mm long composite abrasive filament grasped at each end by one of two jaws of a standard tensile tester (known under the trade designation "Instron" Modd TM), where the jaws were initiaily spaced 25 mm apart and then separated at 15 the rate of 50 mm a minute. The force required to break each filament was noted and~recorded as kilograms force required.

Composite Abrasive Filament Extrusion ~ ~ Vanous composite abrasive in accordance with this invention were 20 prepared by the melt extrusion process. A twin screw extruder fitted with two30 mm diameter co-rotating screws having an LID ratio of 30:1 ~model ZSK-30, from Werner-Pfleiderer), was employed in each case. The thermoplastic elastomers employed were first rendered molten by the extruder (using zone and die temperatures in Table A above for each TPE), whereupon abrasive 25 particles were controllably added through a feed port of the extruder barrel.Preformed cores of stainless steel, aramid fiber yarn, glass fiber yarn, depending on the Example, were pulled through an extrusion die which allowed the molten abrasive-containing TPE to be coated on the preformed cores. The extrusion die used was commercially available under the trade designation 3Q "LOVOL", from Genca Die, Clearwater, Florida. After exiting the extrusion die, the molten TPE was hardened by cooling the coated preformed core in a ,:

,-~ wo 93/18890 pcr/l IS93/01246 water stream placed about 150 mm from the face of the extrusion die, after which the abrasive-filled, TPE coated preformed core was wound onto a separate roll for each preformed coretTPE combination. Composite abrasive filarnents were subsequently cut from each roll. It is important to note that S none of the coated preformed cores produced by the above method required orienting prior to being accumu1ated on the roll, subsequent cutting into filaments, and fabncation into brush devices.
The TPEs employed, including some of their physical properties, are listed in Table 1. Table 2 lists the various preformed cores used, while Table 310 lists the example composite abrasive filaments (Examples 1-27). Table 4 listsComparative Examples A-F, where TPE, abrasive particle type, size, etc., are tabulated. The abrasive particle content was determined by using a standard thermal burnoff technique.
Five abrasive-filled nylon control filaments A-E were used to compare 15 with l~xamp!es 1-24, which used Test Brush Construction I, above. The composition of Comparative Example filaments A-E is indicated in Table 4.
All Comparabvè Example filaments A-E were commercially available (under the trade designation "TYNEXn) from du Pont except for Comparative Example B filament, which was commercially available from Asahi Chemical Company, 20 Japan.
Three brushes were made using Test Brush construction II, and employing composite abrasive filaments comprising blends of polyurethane TPE
and ABS terpolymer (Examples 25-27). A "control" Example F was used to verify the abrasion testing. Example F used composite abrasive filaments 25 similar to Example 8A, differing only by employing Test Brush Construction II.
The composition of Example F is listed in Table 4, although this filament is within the invention.
The results of the abrasion tests described above are presented in Table 5 for the composite abrasive filaments (Examples 1-27) made in accordance 30 with this invention, while Table 6 lists abrasion results for Comparative ~xample filaments A-F.

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2~28092 - 42 -Discussion of Results FIG. 8 shows, in bar graph form, the results of workpiece rem~ved as a function of time tests for comparative Examples A and B and Examples 1-3 of the present invention. It is clear that abrasive filament Example A (abrasive-S filled nylon, known under the trade name "TYNEXn) starts cutting well, butdulls rapidly to less than 5% of its original cutting ability within 1 hour under these test conditions. Comparative Example B (abrasive-filled nylon, known under the trade name "ASAHI") performed better, but not as well as the composite abrasive filaments of Examples 1-3, which started at a higher level 10 (grams) of cut and retained their cutting abilities significantly better than the comparative Examples. This is apparent ~on flat 1018 CRS plate abrasion tests (FIG. 8) and perforated screen 1008 CRS abrasion tests (FIG. 9). The polyester TPE composite abrasive filaments employing TPEs with higher Shore D dorom showed more aggressive abrasive cutting action on both plate and 15 screen.~
~ Fatigue r~istance test;results (Table 4) showed that abrasive-filled nylon filaments ~(Ex=mple A) ~exceeded their limits in 10-15 minutes. The softer, TPE coate~ composite abrasive filaments (Examples I and 4) remained usable greater than 2 hours, while the hardest polyester-coated 20 composite abrasive filaments (Examples 3, 7-9) were usable only for very short dmes. The best balance of fatigue resistance and abrasive cut on both ste~l ;
plate and~screen using polyester TPE-coated composite abrasive filaments was obtained with the polyester TPE having Shore D durometer of 63.
FIG. 10 shows that cutting ability of the composite abrasive filament of 25 Example 4 (334 abrasiYe) is less than Example S (S0% abrasive) on both 1018 CRS plate (+) and 1008 CRS screen ~*~. lt appears that the composite abrasive filaments allow higher abrasive loading and hence greater amount of workpiece removed.
FIGS. 11 and 12 compare the results of cutting vs. time for Examples 30 A, 4, and S, on both 1018 CRS plate and 1008 CRS screen, showing that the , :

wOs3/l88sl) 2~8Q92 Pcr~US93/01246 composite abrasive filaments significantly out perform the abrasive-filled nylonabrasive filament to a greater degree with higher percent abrasive loading.
FIGS. 13 and 14 compare cutting performance OI abrasive filaments A, C, 2 and 6 of Table 3. With abrasive-filled polyester TPE-coated, stainless 5 steel preformed core composite abrasive filaments, aluminum oxide abrasive-containing composite abrasive filaments of the invention were more aggressive than silicon carbide abrasive-containing composite abrasive filaments on both 1018 CRS plate and 1008 CRS screen. A second set of composite filaments were prepared with fused aluminum oxide abrasive grains, heat treated 10 aluminum oxide abrasive grains, and ceramic aluminum abrasive grains ~e latter known under the trade designation "Cubitron") in Examples A, 7-9.
FIGS. 15 and 16 show the results of abrasion tests on simila~r steel plate and screen, respectively In Bxamples 7-9, glass plied yarn preformed cores were coated with abrasive-filled 72 Shore D durometer polyester TPE known under 15~ ; th;e tradé designation ~"Hytrd 7246". Prom e~aiments with abrasive-filled :
nylon~filaments, ~it was not expected~that there would be any significant difference in abrasive cut between aluminum oxide or silicon carbide-filled ~liermoplastic dastomas coated composte abrasive filaments of the invention.
However,~ quite surprisingly, the aluminum oxide and silicon caioide abrasive-20 filled composite ab~asive filaments~ gave two to four times better cut than aluminum oxide-filled nylon abrasive filaments on flat plate (compare FIGS. 13 ~and IS)~,~ and the heat treated aluminum oxide-filled composite abrasive filaments of the invention performed significantly better on screen (FIGS. 14, 16). FIGS. 15 and 16 show that abrasive acdon can be significantly increased 25 using the somposite abrasive filaments of the invention when belter grades of abrasives are employed.
FIGS. 17-20 present, in bar graph form, comparative abrasion tests using filament Examples D, E, and 10-13 to compare the performance of filaments employing P320 and P220 aluminum oxide and silicon carbide 30 abrasive particles. In each of Examples 10-13 the segmented polyester TPE
known under the trade name "Hytrel 6356n~ was coated over gl~ss yarn known , .
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2~L28(~92 44 under the product code "OCF G75 PY" available from Owens Corning. FlG.
17 prescnts test results for the filaments abrading copper plate, while FIGS. 18-20 present test results for filaments abrading titanium, 304 stainless steel, and -aluminum 6061 T6, respectively.
These data show that marked differences in abrasive performance resulted when a variety of workpieces were abraded. Composite abrasive filaments employing 320 grade silicon carbide exhibited low cut whereas both grades of aluminum oxide showed much higher cut on copper.
Titanium proved to be an unusual metal workpiece. Silicon carbide and 10 aluminum oxide abrasive particles employed in the control abrasive-filled nylon filaments exhibited the greatest cut values on this metal.
On 304 stainless steel workpieces, the results were remarkably different.
The commercially available abrasive-filled nylon filaments were relatively ineffective, whereas composite abrasive filaments of the inven~ion employing 15 the same abrasive particles in Ihe segmented polyester TPE known under the trade designation Hytrel 6356" were much more effective.
Finally, a very unexpected result was obtained when T6061 aluminum workpieces were abraded. Composite abrasive filaments containing altemately silicon carbide and aluminum oxide abrasive particles, in both 220 and 320 20 grades, remarkably outperformed commercially available abrasive-filled nylon filaments.
FIGS. 21-22 represent, in bar graph form, the results of abrasion tests on 1018 CRS steel plate (FIG. 21) and 1008 CRS steel screen (FIG. 22), respectively, for ~xample composite abrasive filaments 14-16. These examples 25 utilized P120 aluminum oxide abrasive-filled polyamide TPE coatings on glass plied yarn preformed cores. FIG. 21 shows that these filaments were not as aggressive on steel plate, but were quite aggressive on steel screen (FIG. 22).
FIGs. 23 and 24 are similar to FIGS. 21-22 in that Example filaments 17-22 performed well on 1008 CRS steel screen (FIG. 24) but were not as 30 aggressive on 1018 CPcS steel plate (FIG. 23).

wo 93/18890 ~ 9Z PCr/US93/01246 FIGS. 25-28 represent, in bar graph form, the results of abrasion testing using cylindrical brushes (10.2 cm OD) with very dense filament packing on the hubs. Filaments E and 10-13 were compared using a printed circuit board brushing apparatus known under the trade designation "Chemcut". The 5 cylindrical brusbes were turned at 2500 rpm against substrates of 1018 steel, 304 stainless steel, copper, and 6061 T6 aluminum (FIGS. 25-28, respectively) at different power levels as indicated. Composite abrasive filaments of the present invention performed substantially better than abrasive-filled nylon abrasive filaments on 1018 CRS steel, 304 stainless steel, and performed 10 comparatively well on copper and T6061 aluminum.

Claims

CLAIMS:

1. A composite abrasive filament characterized by the feature that at least one preformed core is at least partially coated with a thermoplastic elastomer having abrasive particles dispersed and adhered therein, said thermoplastic elastomer and abrasive particles together comprising a hardened composition.

2. A composite abrasive filament in accordance with claim 1 further characterized by the feature that said preformed core is at least one wire or fiber materials selected from the group consisting of metal wire, glass fiber, ceramic fiber, natural fiber, organic synthetic fiber, inorganic synthetic fiber, and combinations thereof.

3. A composite abrasive filament in accordance with claim I further characterized by the feature that said thermoplastic elastomer is selected from the group consisting of segmented thermoplastic elastomers, ionomeric thermoplastic elastomers, blends of thermoplastic elastomers and thermoplastic polymers, and mixtures thereof.

4. A composite abrasive filament in accordance with claim 1, further characterized by the feature that said preformed core is a plied yarn of fibers selected from the group consisting of glass fibers, ceramic fibers, natural fibers, organic synthetic fibers, inorganic synthetic fibers, and combinations thereof.

5. A composite abrasive filament in accordance with claim 3, further characterized by the feature that said thermoplastic elastomer has a Shore D
durometer hardness ranging from about 30 to about 90.

6. An abrasive article including at least one composite abrasive filament, the composite abrasive filament characterized by the feature that it has at least one preformed core at least partially coated with a thermoplastic elastomer having abrasive particles dispersed and adhered therein, the thermoplastic elastomer and abrasive particles together comprising a hardened composition, with the proviso that if there is more than one composite abrasive filament, the composite abrasive filaments can be the same or different.

7. An abrasive article in accordance with claim 6, further characterized by the feature that said preformed core is at least one wire or fiber of materials selected from the group consisting of metal wire, glass fiber, ceramic fiber, natural fiber, synthetic fiber, and combinations thereof.

8. An abrasive article in accordance with claim 6 further characterized by the feature that said thermoplastic elastomer is selected from the group consisting of segmented thermoplastic elastomers, ionomeric thermoplastic elastomers, blends of thermoplastic elastomers and thermoplastic polymers, and mixtures thereof.

9. A method of making a composite abrasive filament, the composite abrasive filament including at least one preformed core at least partially coated with a thermoplastic elastomer having abrasive particles dispersed and adhered therein, the thermoplastic elastomer and abrasive particles together comprising a hardened composition, said method characterized by the steps of:
(a) rendering a thermoplastic elastomer molten and combining abrasive particles therewith;
(b) coating at least a portion of a preformed core with a coating comprising the molten thermoplastic elastomer and abrasive particles; and (c) cooling the coating to a temperature sufficient to harden the molten thermoplastic elastomer and thus form the hardened composition.

10. A method in accordance with claim 9, further characterized by the feature that step (a) comprises passing the preformed core and molten thermoplastic elastomer simultaneously through a die.