CA1251980A

CA1251980A - Composite nonwoven sheet

Info

Publication number: CA1251980A
Application number: CA000510937A
Authority: CA
Inventors: Gregory P. Weeks
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1985-06-07
Filing date: 1986-06-05
Publication date: 1989-04-04
Also published as: DE3660773D1; JPS61284432A; JPH0530380B2; US4647497A; EP0204582A1; EP0204582B1

Abstract

ABSTRACT OF THE DISCLOSURE
A composite nonwoven sheet is provided having a polyolefin synthetic pulp layer, optionally containing woodpulp and adhesive binder, is adhered by adhesive binder to a continuous filament scrim.
The pulp surface of the composite has unexpectedly high abrasion resistance.

Description

1~'r~ ~980 This invention relates to a sheet structure which includes a layer of polyolefin synthetic pulp.
More particularly, the invention concerns a calende~ed composite sheet which includes a ~crim of continuous fila~ent6 adhered to the layer comprising the polyolefin synthetic pulp.
Synthetic pulp5 made from polyolefins, such as polyethylene, polypcopylene and blends theceof, are known in the art. Kirk-Othmer EncYcloDedia of Chemical Technoloqv, volume 19, third edition, John Wiley ~ Sons, p. 420-435 (1982) desceibes synthetic pulps as generally being very fine,highly branched, discontinuou6, water-dispersible fibers made from plastics. Known methods for producing the synthetic pulp8 include solution fla6h-spinning, emulsion flash-spinning, melt extrusion/fibrillation and shear precipitation. The pulps may be blended with woodpulp or glass fibers or other short fibers and made into papers, sheets or boards by conventional wet-lay papermaking techniques. The pulps may include various additives guch as wetting agent~ (e.g., polyvinyl alcohol), inorganic fillers (e.g., kaolin, clay, talc, calcium carbonate), stabilizers and the like. The polyolefin pulp products 80 produced may be heated to fuse the polyolefin pulp, and, as disclosed by Hercules Incorporated, Bulletin LT-109 "Pulpex~
Polyolefin Pulps for Nonwovens" (March 1982), are suited for use as bonding agents for certain nonwoven materials 6uch as dry-laid, Rando-Webber-formed sheets and wet-laid, Fourdrinier-formed sheets. In such nonwoven materials, the polyolefin pulps are blended with pulps of wood fibers or wa~te fibers, the polyolefin being in amount6 that generally range from

2 to 40~ of the total blend. The poro~ity and bondability of such materials can be controlled by ~,C

1~51~

adjusting the temperatuce and pressure of bonding as well as the fraction of polyolefin pulp included.
The present inventoc has found that the utility of the above-described types of synthetic-pulp nonwoven ~atecials is limited. The sheets often lack strength and need considerable imerovement in durability and abrasion resistance of the sheet sucface. Accordingly, an object of the present invention is to provide a sheet stLucture wherein the shortcoming6 a6sociated with polyolefin synthetic pulp sheets are minimized or at least 60mewhat alleviated.
Many type6 of composite nonwoven sheets are known in the art. For example, although not related to synthetic pulps, Research Disclo6ure, 15789 "Reemay~ paper composites" (June 1977) disclo~es that a spunbonded continuous filament polyester nonwoven fabric can be combined with wet-laid wood pulps, staple fibers and re6ins to form composite sheets.
With or without resin6, the composite 6heets are ZO disclosed to have improved properties relative to the paper, e.g., 4 to 7 time6 the tear strength, 3 to time6 the dimensional stability on exposure to moisture, 2 to 4 times the wet strength and improved fold resistance. Also disclosed is the use of adhe6ive resin within the pulp or as a coating on the continuous filament nonwoven ~abric to improve the adhesion of the pulp layer to the nonwoven fabric.
The present invention provides a calendered composite nonwoven sheet which is characterized by a nonwoven 6crim of continuous filaments, prefe~ably of 6ynthetic organic polymer, and an abrasion-resistant pulp layer comprising at least 50~ by weight of polyolefin synthetic pulp, the scrim and the pulp layer being adhered to each other by an adhesive binder. Other materials that may be incorporated in lZ51~

the pulp layer include wood pulp, amounting to no more than 50~, and preferably no more than 30%, and most preferably no more than 10% by total weight of the pulp layer, and adhesive binder amounting to no more than 20% and preferably no more than lo~ by weight of the pulp layer. Preferred compo~ite sheets of ~he invention are particularly suited for use as house aic-infiltration barriers and outdoor signs and banners. The pulp layers of the composite ~heets of the invention exhibit surpeisingly greater resi~tance to surface abrasion than do sheets calendered under the same conditions and made of the same weight and composition of the pulp layer but without the scrim.
The invention will be more readily understood by referring to the drawing, which is a schematic representation of equipment suitable for making composite sheets of the invention, and is described in detail in the Examples 1 and 2 below.
The present invention provides a calendered composite nonwoven sheet which includes (a) a continuous filament nonwoven scrim (b) an abrasion resistant synthetic pulp layer and (c) an adhesive binder which adheres the scrim to pulp layer.
A wide variety of nonwoven scrims is suitable for use in the composite sheets of the invention.
Depending on the strength characteristics desired in the final composite sheet, the scrim may be made of randomly deposited or directionally deposited continuous filaments. The filaments may be of synthetic organic polymer or glass. Synthetic organic polymer filaments, especially of polyester, polypropylene or nylon are preferred. Usually, the material used for the scrim layer is bonded, preferably self-bonded. 80 that a suitable balance of tear and tensile strengths is obtained. Suitable ~251~1~0 scrims are capable of beinq saturated by wate~ sprays but also are capable of permitting water to drain readily through it by gravity and/or suction while on a Fourdrinier wire.
The scrims may be of a wide ~ange of unit weights. A weight in the range of 15 to 85 g/m2 is suitable. ~he heavier weiqhts are usually preferred when very high strengths are desired in the final composite. Filaments in the range of 1 to 10 dtex ace usually useful, though coarsel or finer filaments may be employed. A group of suitable scrim6 is illust~ated in the Example 8.
It is preferced that the scrims contain an adhesive binder, at least on the surface of the lS filaments that become part of the interface with the polyolefin synthetic pulp layer. The adhesive binder usually amounts to no more than 10~ by total weight of the scrim, preferably 3 to 8~. In fabricating the composite sheet, the adhesive binder is preferably added to the scrim before the scrim i8 combined with the pulp layer. This can be accompli6hed by a pre-treatment such as gravure coating, doctoring or spraying an adhesive binder latex on the ~crim surface.
The pulp layer of the composite sheet of the invention may be made entirely of or comprise at least 50% by weight of polyolefin synthetic pulp. Preferred polyolefins include polyethylene, polypropylene or blends thereof. Polyethylene synthetic pulps are paeticula~ly preferred. Generally the synthetic pulp particle6 have diameters of les6 than 10 microns. A
group of suitable polyolefin synthetic pulps is illustrated in Example 9.
The pulp layer in the composite of the invention may be of a wide ~ange of unit weights.
Generally, pulp layecs weighing 15 to 70 g/m are 1251~30 suitable in the composite sheets of the invention.
The pulp layer may contain woodpulp amounting to as much as 50% by weight of the layer. However, to obtain high abrasion resi~tances, woodpulp contents of S no more than 30% by weight of the layer are preferred. Most preferred, are woodpulp contents of no more than 10%. The inclusion of woodpulp along with the polyolefin synthetic pulp significantly improves the printability of the pulp layer surface and in manufacture enhances the formation and uniformity of the pulp layer. A wide variety of woodpulps are suitable for use in the present invention, including soft or hardwood pulps commonly used in the paper industry. Very fine wood pulps, such as eucalyptus pulps or highly refined grades of conventior.al woodpulps are preferred because of ~uperior uniformity of dispersion these provide in the pulp layer. The pulp layer may also contain an adhesive binder amounting to as much as 20% by weight Z0 of pulp layer. ~o obtain high porosities in the composite sheet the adhesive binder in the pulp layer amounts to preferably no more than 10~ by weight of the pulp layer.
A wide variety of adhesive binders can be used in the present inYention. Because the composite sheet~ of the invention are usually made by wet-lay papermaking techniques, preferred adhesive binders are thermoplastic resin adhesives which are available as aqueous latexes that can be precipitated readily. It is also preferred that such binders have an activation temperature in the range of 70 to lOO~C: that is low enough to avoid melting of the scrim fibers but sufficient to activate the binder under typical papermaking calendering conditions. A particularly preferred adhesive binder is an ethylene/vinyl acetate copolymer.

12Sl~

All the compo~ite sheets of the invention are calendered. secause they are calendered the adhe~ive binder forms a strong bond between the pulp layer and the ~crim, the particles of the scrim are more firmly bonded to each other and the surface abrasion resistance of the pulp layer is enhanced.
Surprisingly, the abrasion resiseance of the pulp surface of the composite ~heets of the invention are much superior to that of synthetic pulp papers of the same synthetic pulp weight calendered under the same conditions. This advantage of the composite sheets of the invention is reflected by a Taber abrasion resistance that is many times ~e.g., 7 to 100 times or more) as great as that of comparison synthetic pulp papers. This unexpectedly large abrasion resistance advantage is demonstrated in Examples 6, 7 and 9.
Preferred calendered composite sheets of the invention is illustrated particularly in Examples 1 and 2. The scrim of such preferred sheets is of continuous filaments of ~ynthetic orqanic polymer, weighs in the range of lS to B5 g/m2 and contains an adhesive binder amounting to 3 to ~% by total weight of the scrim. The pulp layer of the preferred sheets weighs in the range of 15 to 70 g/m2 and comprises by total weight of the layer at least 70~ polyolefin synthetic pulp, up to 30% woodpulp and up to 20%
adhesive binder. In preferred calendered composite sheets of the invention particularly suited for use as house air-infiltration barriers, as illustrated in Example 1, the scrim weighs in the range of 25 to 50 g/m , the pulp layer weighs in the range of 15 to 30 g/m and has a woodpulp content in the range of 3 to 10% and the compo~ite sheet has a strip tensile strength of at least 25 Newtons, a grab strength of at least 75 Newtons, a hydrostatic head of at least Z5 cm lZS1~38~

and a moisture vapor transport of at least 400 g/m /day. In preferred calendered composite ~heets of the invention particularly suited for outdoor signs and banners, as illustrated in Example 2. the scrim weighs in the range of 30 ~o 60 g/m2 and has a woodpulp content in the range of 3 to 30% and the composite sheet has grab tensile strength of at least 75 Newtons, an Elmendorf tear strength of at least 5 Newtons and a Mullen bur~t strength of at least 125 kiloPascals.
Preferred proce6ses by which the invention can be carried out are illustrated and described particularly in Examples 1 and 2, with reference to the attached drawing. Briefly, the preferred process employs a conventional Fourdrinier machine. A scrim of continuous filaments, preferably in the form of a roll of spunbonded sheet of continuous filaments of synthetic organic polymer, and optionally precoated with an adhesive binder and/or an adhesive coagulater, is fed onto the forming wire of the ~ourdrinier machine. A furnish slurry is deposited atop the scrim. The slurry includes polyolefin synthetic pulp, an adhesive binder ~optional if adhesive resin is precoated on the scrim) and optionally woodpulp.
Excess water from the furnish slurry is drained by gravity and/or suction through the scrim and forming wire. The thusly formed composite is dewatered further in a press section of the machine and then dried by passage over heated drier cans. The dried composite i~ then calendered under load. The drying and/or calendering conditions are sufficient to activate the adhesive binder. The calendered composite sheet is then wound up into a roll.
The various characteristics and properties of the synthetic pulps and composite sheets referred to 1%Si9~

herein are measured by the methods describe~ below and listed in Table I. ASTM refers to the American Society of Testing Material~, TAPPI to the Technical Association of Pulp and Paper Industry, AATCC to the American Association o Textile Chemists and ColoriRts, and lNDA to International Nonwovens and Disposables Association.

TABLE I
SHEET PROPERTY MEASUREM NTS
Characteristics Test Method Units General Pcoperties Weight ASTM D-3776-79 g/m2 Thickness TAPPI T-411 mm Drapeflex ASTM D-13B8-64 cm Vertical flame AATCC 34-1969 mm Opacity ASTM D-589 % transmission Strength Properties Strip tensile ASTM D-1682-64 Newtons Grab tensile ASTM D-1117 Newtons Elmendor~ tear ASTM 9-132 Newtons Trapezoidal tear Federal Spec. Newtons CCC-T-19lb-5136 Tonque tear ASTM D-2261-64T Newtons Seam tear ASTM D-1683-81 Newtons Pinch tear ASTM 827-47 Newtons Mullen burst ASTM D-1117-74 kiloPascals Barrier Pcoperties Hydrostatic head AATCC 127-77 cm Z Fraziec air permeability ASTM D-737-46 m3~m2/min Gurley-Hill pocosity TAPPI T-460 M-49 sec/100 cm3/
6.45 cm2 Moisture vapor transport TAPPI 448 M-49 g/m2/24hr Mason jar test INDA IST 80.7-70 ~ pass Spray rating AATCC 22-1977 Taber abrasion ASTM D-1175-64T cycles The above-listed abrasion measurement is made with a Ta~er Model 174 abrader having a CS-10 abrader wheel and no weights on the abrader acm (unless otherwise indicated as a 500-gram weight). The end point of the test is judged to occur when the pulp layer is penetrated by the abcader wheel, A small, soft-haired brush is used to remove abraded dust from the sample in lleu of the ASTM-recommended vacuum, 1251~0 The characteristics recorded herein for the polyolefin synthetic pulps include (a) th~ drainage factor, which i8 measured in accordance with TAPPI
T-221-SU-72. modified a~ described in U.S. Patent

3,920.507 (b) fiber retain is the percent of the synthetic polyolefin pulp in a furnish that is retained on a 100 mesh screen, which is measured in accocdance with the Bower-McNett Fiber Length Classification test, TAPPI T-23305-75, (c) surface area, which is measured in m2/g in accordance with the nitrogen gas absorption method of ASTM D-1388-64, and (d) pulp dimensions, which are those reported in ~icrons by the pulp vendors and generally determined in accordance with TAPPI T-233-SU-64.
The examples which follow illustrate the fabrication of a variety of composite sheets of the invention. The composite sheet of Example 1 is suitable for use as a home air-infiltration barrier;
that of Example 2, for use in outdoor signs and banners: that of Examples 3 and g, as commercial mail envelopes; and that of Example 5, a6 medical operating room drapes. Example 6 demonstrates the advantageous surface abrasion resistance of composite sheets of the invention under various calendering conditions.
Example 7 shows the effects on abrasion resistance of woodpulp addition to the synthetic pulp layer.
Examples 8 and 9 respectively illustrate the invention with different types of continuous filament scrim6 and with different types of polyolefin synthetic pulps.
Conventional papermaker6 equipment was used in all examples. The composite sheets of Examples 1-5 were made with a Fourdrinier machine and the sheets of Examples 6-9 were made with a papermakers hand-sheet mold. In the Examples, all percentages, unles6 otheewise stated, are by weight.

1~5~98~

In this example, equipment of the type illustrated in the attached drawing was used to prepare a composite sheet of the invention that was particularly suitable for use in house construction as an air infiltration barrier. The compo~ite ~heet was made from a ~crim and a pulp furni~h. The scrim was in the form of a spunbonded polyester continuous filament web which had been pretreated on one surface with a thecmoplastic resin latex. The pulp furnish included a polyethylene synthetic pulp, woodpulp and a thermopla6tic latex binder.
A continuous filament spunbonded web, Reemay~
2015 (601d by E. I. du Pont de Nemours and Company, Wilmington, Delaware), weighing 37.3 g/m2 (1.1 oz/ydZ) and compo6ed of thermally bonded, polyester filaments was the starting material for the scrim. The web had a thickness of 0.23 mm (0.009 inch) and a Fraziec air permeability of 200 m3/m2/min at 1.27-cm head of water (665 ft3/ft2/min at 0.5 inch of water). The web was provided as a roll wound on a 17.8-cm ~7-inch) diameter core and measuring 3.96-meter (156-inch) wide and 1 meter in diameter. The web was fed on a tenter frame at 40 meters per minute under a uniform fine mist spray of Elvace~ 1875 thermoplastic ethylene/vinyl acetate copolymer aqueou6 latex (sold by Reichhold Chemical Corporation, Dover. Delaware) that had been diluted from a nominal 55% solids to 10%
solid6. The sprayed web was then advanced through a forced air oven operating with an air temperature of 176C (350~F) to dry the web. The web wa6 then wound up. A 5% dry refiin add-on (based on the weight of the polyester filament-6crim was obtained. The resin was concentrated on the surface filaments of the treated 12~1t3B13 surface. The Frazier air permeability of the scrim was substantially the same before and after the resin add-on.
The resin-treated web 2 (numeral designations refer to the drawing) was unwound from roll 1 and advanced under the headbox 15 of a conventional

4.6-meter (180-inch~ wide Pourdrinier machine.
Upstream of the headbox, the sheet passed through water spray 10, which thoroughly wetted the sheet. The wetted 6heet was pas6ed under guide-and-tensioning roller 11 and then under headbox 15 and its outlet 16 onto forming wire 17, which was driven by roll 18 and suction roll 19. The web, with pulp deposited thereon from headbox outlet 16, as described in the next paragraph, was then forwarded, in succession, through the press section of the machine (indicated by rolls 20 to Z5 and belts 27 and 28), under guide roll 26 to the primary dryer section (indicated by cans 30 to 37--felts which hold the web to the cans are not shown), to the size press section (indicated by rolls 40 to 44), to the secondary dryer section (indicated by cans 50 to 53), under roll 54 and through a calender stack (indicated by rolls 60 to 64), to windup as a roll 70 of composite sheet of the invention.
The furnish which was fed through headbox outlet 16 onto web 2 and formed the pulp layer was prepared as follows in a conventional paper-machine beater. Five-hundred kilograms (1100 lbs) of Pulpex~
~-A polyethylene synthetic pulp (sold by Hercules Corporation, Wilmington, Delaware) having a wet lap weight of 1326 kg (2917 lb) including a, 62.3%
moisture content, was added ~o 18.9 kiloliters (5.000 gal) of water in a 37.8 kiloliter (10,000 gal) capacity beater system and blended for 20 minutes.

l~Sl~O

Then, 27.3 kg ~60 lb) of eucalyptus woodpulp was added and the furnish was blended for an additional 20 minutes. The pH of the furnish was then adjusted to 7.5 by adding a small amount of ~oda of silicate. To thi~ blend was added 113.5 kg ~250 lb, 30 gal) of Latiseal~ A7922A an ethylene/vinyl acetate copolymer latex binder (sold by Pierce and Stevens Chemical Corporation, Buffalo, New York) having a solids content of 42~. Agitation and blending were continued for 10 minutes. Then, to ~lowly precipitate and set the latex, 9 kg (20 lb) of papermakers alum, as a 5%
aqueous solution, was added. Another 13.6 kg (30 lb) as a Z0~ solution was added to as6ure complete precipitation of the latex. Then more water was added 80 that the solids content of the furnish was reduced to 2.5S. This furni6h solids consisted of 86.9~
polyethylene synthetic pulp, 4.8% eucalyptus woodpulp and 8.3~ ethylene/vinyl acetate copolymer latex binder resin. This furnish was then transferred to feedchest 13 of the Fourdrinier machine and further diluted to 1~ solids.
The dilute furnish was fed via pipe 14 to headbox 15 through a conventional water recirculation loop (not shown). Flows were adjusted to produce a Z5 0.2~ solids content in headbox 15. A solution of 22.7 kg of Gendriv~ cationic guar derivative, a viscosity enhancer (sold by Henkel Corporation, Minneapolis, Minn.) in 1.89 kiloliters of water (50 lb in 500 gal) wa~ injected ahead of the headbox at a rate of 11.3 liter6/min (3 gal/min) to aid furnish deposition uniformity. Forming wire speed was adjusted to 45.6 meters/min (150 ft/min). Furnish flow through headbox outlet 16 onto web 2 wa~ adjusted to provide a dry solids furni~h coating weight of 20.3 g/m2. Furnish was thus deposited from the headbox onto the upper --- lZS19~

surface of the spunbonded continuous filament scrim.
Excess water was d~ained fir6t by gravity and then by suction as the web and depo~ited material advanced with the forming wire. The thusly formed composite was then fed from the wire through ~he press section to the primary dryer section where the dryer rolls were internally heated by steam, so that each drum was a little hotter than the preceding one. The first roll 30 was heated with steam at 107C (225F) and the last roll 37 at 121C (Z50~) which brought the temperature of the surface of the pulp layer of the composite sheet to about 95C.
The 6urface of the compo6ite wa6 then treated further by pa66age through the 6ize pres6. In the size pce6s, a 601ution made from 45.4 liter6 (12 gal) of Quilon~C, a water repellent (sold by ~. I. du Pont de Nemour6 and Company, Wilmington, Delaware) diluted in 2270 liter6 (600 gal) of water wa6 applied to the composite sheet. The sheet was then redried to a moi6ture content of le66 than 3~ by pas6age over steam-heated roll6 50-53 of the ~econdary drier section.
The compo6ite wa6 then calendered by pa66age through a four-nip calender stack ~represented by rolls 60-64) which operated with a load of 71.5 kg/linear cm (400 lb/in). The composite wa6 finally wound up into a roll 70.
The properties of the thusly fabricated composite sheet were as follows.
Unit weight: 57.6 g/m2 (1.7 oz/yd2) Furni6h solid~: 35S of 6heet weight Thickne66: 0.127 mm (0.005 inch) Strip ten6ile:
Longitudinal (MD) 44,5 N (10 lb.) Tran~ver6e (XD) 35.6 N (8 lb.) ~L2S1~3~30 Grab tensile:
MD 138 N (31 lb.) XD 116 N (26 lb.) Elmendorf tear:
S MD 10.7 N ~2.4 lb.) XD 12.0 N (2.7 lb.) Tonque tear:
MD 18.2 N (4.1 lb) XD 13.8 N (3.1 lb) Hydrostatic head: 36-43 cm Gurley poro6ity: 9-13 sec/100 cm3/
6.45 cm2 Moisture vapor transport: 650 g/mZ/day Taber abrasion: 30 cycles Spray impact rating: 90%
Ultraviolet light stability: - No 1088 in physical properties in two months of outdoor exposure.
ExamDle 2 Thi6 example illustrates fabrication of a composite 6heet of the invention which was useful for outdoor signs and banners.
A 1.52-meter (60-in) wide roll of Reemay~
2016 spunbonded polyester filament web having a thickness of 0.23 mm (0.009 inch), a Frazier permeability of 158 m3/m2/min (525 ft3/ft2/min) and a nominal weight of 44 g/m2 (1.3 oz/yd2) had a 25% solid6 solution of Elvace~
1875 latex re6in applied to one 6urface of the web by mean6 of a direct coating gravure roll having 27.6 line6/cm(70/inch). The polyester web was coated and dried at 50 m/min and achieved a 5% dry resin add-on.
Sub6tantially all the dry re6in was located on the surface filaments of the treated surface of the web.
The treated web was then placed on an unwind stand and passed through a Fourdrinier machine which lZ~ 8~

was operated in the same manner and with the same ingredients of furnish as in Example 1, except that 27.2 g/m of furnish solids was deposited on the scrim and the nip load on the calender was 91 kg/linear cm ~200 lb/in). The resultant product was then further calendered off-line on a 1.22-m (48-inch) wide conventional textile calender in a single pass with the pulp side of the composite against the smooth steel roll and the scrim side against the composition roll of the calender. The calendering temperature was 60C and the calendering load wa6 224 kg/linear cm (1250 lb/in). The properties of the final composite were a6 follows:
Unit weight: 71.3 g/m2 (2.1 oz/yd2) Furnish solids: 37% of sheet weight Thickness: 0.321 mm (0.0052 inch) Grab tensile:
MD 171 N (38.4 lb) XD 125 N (28.0 lb) Elmendorf tear:
MD 12.4 N (2.78 lb) XD 7.3 N (1.64 lb) Seam Tear:
MD 166 N (37.2 lb) XD 127 N (2B.5 lb) Trapezoidal tear:
MD 38.3 N (8.6 lb) XD 24.9 N (5.6 lb) Drapeflex:
MD 8.4 cm XD 6.6 cm Mullen bur6t: 162 kPa (24.6 psi) Opacity: 25~ tran6mission ~519~

Outdoor bannecs measuring 0.91 by 1.82 meters (3x6 feet) were fabricated in a conventional manner by folding over edges and double seaming to cceate a channel thcough which a rope was passed. The copes were used to support the banners between vertical posts. The bannecs made from the compo~ites of this example wece then field tested and were found to be pecforming well aftec more than two months of weathecing and exposure to wind6 of up to 48 km/hc ~30 mile6/hr).
ExamPle 3 This example illustcate6 the fabrication of a composite sheet of the invention which wa6 suitable for use a~ mail envelopes.
A 6crim/pulp compo6ite sheet was made on a conventional Foucdrinier paper machine using the 6ame proce6sing conditions a6 in Example 2 including pre-treatment of the scrim. The composite consisted of a Reemay~ 2014 continuou6 filament scrim having a Z0 weight of 33.9 g/m2 (1.0 oz/yd2), a thickness of 0.203 mm (0.008 inch) and a Frazier air pecmeability of 241 cm /m2/min (800 ft /ft2/min). The fucnish composition was adjusted to consist of 500 kg Heccules Pulpex~ EA, 27.2 kg of eucalyptu6 woodpulp, 54.5 kg of bleached northern softwood pulp, and 113 kg of Latiseal~ A78922A. The head box deposition rate was adjusted to give a pulp coverage weight of 33.9 g/m2(1.0 oz/yd2). The composite wa6 calendered in line through the bottom nip of a conventional calendec stack with nip load of 35.7 kg/linear cm (200 lb/in).
No other po6t calendecing wa6 used.
The propertie6 of the final composite wece as follows:

1251~ 3 Unit weight: 69.5 g/mZ (2.1 oz/yd2) Furni~h solids: 49% of sheet weight Thickness: 0.254 mm (0.010 inch) Strip ten~ile:
MD 41.4 N (9.3 lb) XD 33.4 N (7.5 lb) Grab ten~ile:
MD 128 N (28.8 lb) XD 119 N ~26.7 lb) Elmendorf tear:
MD 5.4 N (1.22 lb) XD 4.1 N (0.92 lb) Mullen burst: 168 kPa (24.4 p8i) Drapeflex:
MD 7.8 cm XD 7.0 cm Taber abrasion: 50 cycles Opacity: 21~ transmission Manual tearing of a folded edge of the composite sheet is a conventional rapid trade test of the 6heet as a reinforced paper envelope. The composite ~heet of this example exhibited excellent resistance to tear initiation. When tear was initiated and continued.
the sheet tore ag an integral composite rather than by delamination of the pulp layer from the scrim.
ExamDle 4 This example also illustrates the fabrication of a composite sheet of the invention that is useful for envelopes. In contrast to the preceding example, the pretreatment of the continuous filament scrim was performed in-line with the papermaking equipment.
Substantially the same proces6 conditions as were used in Example 2 were employed in this example.
The scrim consisted of a 152-cm (60-inch) wide Reemay~
2014 continuou~ polyester filament spunbonded web: the 1~51~
1~
scrim was latex-coated in line as described in the next paragraph; and the fueni~h solid~ were made up of 64% Pulpex~ EA, 18% northern ~oftwood pulp, 9%
eucalyptu~ woodpulp and 9~ La~iseal~ A792ZA. The deposition rate at the head box was adjusted to give a 40 7 q/m2 (l.Z oz/yd2) pulp furnish solids coverage.
The latex precoating of the ~crim was perfo~med as follows. A 3~ paper-makers alum solution was applied, instead of water at the scrim prewetting ~prays (numeral 10 in the drawing) just prior to the headbox to thoroughly prewet the scrim with alum solution. Alum solution was applied at a rate of 54.6 liters/min (14.5 gal/min) with the scrim advancing at a rate of 45.6 m/min (150 ft/min). Between the alum solution prewetting and the headbox a Z~ aqueous solution of Latiseal~ A 7922A was sprayed (designated 12 in the drawing) at a rate of 0.1 liter/m2 onto the scrim. The pH of the latex 601ution wafi adju6ted to be alkaline to ensure that the latex did not coagulate until it contacted the alum-solution-60aked scrim. Upon contacting the 6crim, the latex was rapidly coagulated by the alum. The Reemay~ having been thus treated, then advanced immediately onto the forming wiee of the paper machine where the synthetic pulp, woodpulp and latex of the furnish were deposited on the scrim ~urface and the excess water was drained from the furnish as in preceding example~. The composite was dried, treated with repellent Quilon2 C, redried and calendered through four nips of a calender stack as in preceding examples.
The properties of the resultant composite sheet were a~ follows:
Unit weight: 76.3 g/m2 (2.3 oz/ydZ) Thickness: 0.15 mm (0.006 inch) 1;~519~0 z~
Strip tensile:
MD 45.5 N (10.2 lb) XD 35.6 N (8.0 lb) Grab tensile:
S MD 154 N ( 34 . 5 lb) XD 134 N ( 30 . 0 lb) Elmendorf tear:
MD 19 . 6 N ~4.4 lb) XD 15.1 N (3.4 lb) Mullen burst: 43.4 kPa (6.3 psi) Hydro6tatic head: 60 cm Gurley porosity: 18 seconds/loO cm3/
6.~5 cm2 Moisture vapor transport: 696 g/m2/24 hr.
Taber abrasion: 70 cycles The adhesion between the pulp layer and scrim was 80 strong that the layers could not be separated without destroying the integrity of the individual layeLs .
ExamDle 5 This example illustrates the fabrication of composite sheet6 of the invention which are suitable for use as medical operating room drapes.
A composite sheet of the invention was made under the proces6ing conditions as in Example 2, except for the calendering conditions. However. the ~tarting scrim in this example was Reemay~ 2006 spunbonded polyester continuous filament web having a weight of 20.4 g/m2 (0.6 oz/yd2), a thicknes6 of 0.165 mm (0.0065 inch) and a ~razier permeability of 301 m3/m2/min (1000 ft3/ft2/min). The furnish composition was the same as that of Example 1.
The composite 6heet was in-line calendered under the same conditions a6 were used in Example 3. The composite was further embo6s-calendered by pa6sing the ` 1~5191~0 composite fabeic through a nip formed by a composition roll and a steel roll engraved with a fine linen weave pattern. The pulp layer of the composite sheet contacted the engraved steel roll. Embossing calender nip load was 26.8 kg/cm ~150 lb/in). A linen weave pattern was thereby embo~sed on the pulp ~urface of the compo6ite 6heet without destroying the integrity of the pulp layer.
The properties of the thus produced composite ~heet of the invention were:
Unit weight 48.6 g/m (1.4 oz/yd2 Furnish solid6 56% of sheet weight Thickness 0.152 mm (0.006 inch) Grab tensile MD 69 N (15.6 lb) XD 44 N (9.85 lb) Elmendorf tear MD 8.2 N (1.84 lb) XD 3.9 N (0.88 lb) Seam Strength MD 88 N (19.7 lb) XD 56 N (12.6 lb) Taber Abrasion 40 cycles Drape flex z5 MD 9.75 cm XD 6.72 cm Opacity 12.2% transmission Hydrostatic head 28 cm Mason jar test 100%
Gurley porosity 5 seconds/100 cm3/
6.45 cm2 Vertical flame test MD 71 mm XD 67 mm ExamPle 6 Thi~ example illustrates the unexpectedly large improvement in abrasion resistance provided by composite sheets which include a polyolefin synthetic S pulp layer in acco~dance with the invention over a known type of sheet stcucture made with the same composition and weight polyolefin synthetic pulp for a series of calendering condition~.
Hand-sheet samples of resin-pretreated spunbonded polyester continuous filament having a 33.9 g/m (l.0-oz/yd ) layer of Hercules Pulpex2 EA polyethylene synthetic pulp deposited thereon were prepared in the following manner. Four hundred milliliters of tap watec was placed in a l-liter capacity Waring blender. The quantity of synthetic pulp required to achieve the desired dry add-on weight on a hand sample of 20.3 by 20.3 cm (8 by 8 inch) was calculated from the moisture content of the various pulp samples provided in wet lap form. Thus 3.12 grams of Pulpex~ EA wet lap containing 44.9% solids had to be added in order to achieve 33.9 g/m2 (1 oz/yd ) add-on. The required weight of synthetic pulp wet lap was added to the water in the blender and agitated at full speed for 60 seconds. This provided the required furnish. A sheet of Reemay~ 2014 spunbonded polyester which had been precoated on one side with Elvace~ 1875 by the method of Example 2 and having the scrim properties indicated in Example 3 was placed resin-coated side up on a 16-mesh screen at the base of a 20.3 x 20.3 cm (8x8 inch) hand sheet mold.
The sheet mold was filled to a height of 36 cm with tap water and the furnish from the Waring blender was added at the top of the mold. In the mold, the thusly diluted furnish was agitated by hand with a stirrer until a uniform appearing slurry was achieved, at lZSlg~

which time the slurry was immediately d~ained through the scrim and screen. thereby achieving a uniform laydown of the synthetic pulp furnish on the scrim.
The 6crim/synthetic pulp composite sheet was then removed from the mold and dried in a forced aic oven with 9oC aie for a half hour. The dried sample was then dipped in a 2~ aqueous solution of Quilon~ C
repellent and redried in a forced air oven with B0C
air. Finally, the 6amples were calendered in one pass on a 122-cm (48-cm) wide textile calender, having a smooth steel roll and a composition roll. In the calender the pulp surface of the composite sheet was in contact with the steel roll at the temperature and loads indicated below in Table II.
Control pulp-paper hand sheets weighing 33.9 g/m2 ~1 oz/yd2) were made by the procedures described in the preceding paragraph, except that (1) the pulp furnish of the control6 was deposited on Reemay~ which had not been precoated with Elvace~, (2) the pulp layer of each control was separated from the Reemay~ scrim, after the treatment with 2% Quilon~
C solution, and (3) only the separated pulp layer was calendered. In this way, properties of the calendered scrim/pulp composite hand sheets of the invention could be compared directly with calendered pulp sheet of the same weight and composition as was used in forming the scrim/pulp composite.
The results of Taber abrasion tests on the pulp surface of the composite sheets of the invention and corresponding controls are shown in Table II.

Table II
Test No. 6a6b 6c 6d Calendering Load, kg/cm 112224 224 224 (lb/in) 6251,2501,2501.250 Tempe~ature, oc 6060 80 100 Taber Cycles Sample Composite 81 150 200 1,110 Control Paper 115 8 14 Ratio 7.4 30 25 79 Note that the pulp layers of the composite sheets of the invention in this series of tests possessed Taber abrasion resistances that were about 7 to 80 times as gceat as those possessed by the control pulp papers of the same pulp weight calendered under the 6ame conditions.
Example 7 In this example hand samples oî composite ~heets were made to show the effect of woodpulp content of the pulp layer on the abrasion resistance of the layer. This example also demonstrates the abrasion-~e6istance advantage of the composites of the invention over synthetic pulp control papers.
Composite 6heets were made according to the procedures of Example 6 with a Reemay~ 2014 spunbonded polyester scrim and with pulp layers that were mixtures of Hercules Pulpex2 A-121 polyethylene synthetic pulp and eucalyptus woodpulp. The mixtures were formed by blending the synthetic pulp and woodpulp at the desired ratio~ in the Waring blender. The same drying and finishing steps as in Example 6 were employed. ~he sheets were calendered in one pass between rolls heated to 60~C under a nip load of (a) 224 kg/linear cm (1,250 lb/in) and (b) 112 kg/cm (625 lb/in). Control synthetic pulp/wood pulp sheet6 were made by the same procedures as the controls of Example 6. The controls had the same compofiition and 33 9 g/m2 (1 oz/yd2) weight as the pulp layer of the composite sheets and were calendered under the same conditions. The following table summarize~ the results of Taber ab~asion measurements on the samples and controls.
Table III
Taber Abrasionl~cles to Failure ComPosite Sheet Control Sheet Calendering load, kg/cm224 112 224 112 (lb/in) (1250) (625) 1250 (625) Synthetic pulp to wood pulp ratio 100:0 85 51 15 2 75:25120 26 13 2 50:50 80 20 12 3 25:75 37 14 8 3 0:100 16 9 ~ote that at each nip load and pulp composition the composite sheets exhibit a surprisingly large advantage over the corresponding control pulp 6heets and that the abrasion resistance generally decreases with increases in wood pulp concentration, especially with woodpulp contents of greater than 50%. The data show that for high abrasion resistance, a polyolefin synthetic pulp content of at least 75% is preferred.
ExamDle 8 In this example four different bonded continuous filament 6crims are u~ed for the fabrication of composite sheets of the invention by the procedures of Example 6. Hercules Pulpex~ A-121 polyethylene pulp was used as the synthetic pulp constituent with a total dey furnish add-on to the scrim of about 33.9 g/m2 (1 oz~yd2). The bonded lZSl~O

continuous filament ~ceims were (a) Reemay~ 2014 spunbonded polyester (b) Reemay~ 2214 spunbonded polyester, (c) Typac~ 3121 spunbonded polypropylene (sold by E. 1. du Pont de Nemours and Company) and (d) Cerex~ nylon 66 (sold by Monsanto Company, St. Louis, Missouri). The scrims were precoated on one surface with Elvace 1875 resin by floating a hand sample of the scrim face down for a moment on an aqueous solution containing 10% by weight of Elvace solids to achieve about 50% wet pick-up. After drying in an oven at 80C, the dry add-on of Elvace amounted to about 5~ by weight of the scrim. The final composites were calendered as in Example 1 on a 122-cm (48-inch) wide calender, under a nip load of 224 kg/linear cm (lZ50 lb/in) with roll temperatures at 60C. Table IV summarizes the properties of the scrims and the final composite6.
Table IV
Test No. 8a 8b 8c 8d Scrim ProPerties Type Reemay~ Reemay~ Typara Cerex~
dtex 4.4 2.4 11.1 4.4 Unit Weight, g/m2 33.9 45.854.2 50.9 Thicknes6, mm 0.20 0.23 0.220.19 Strip tensile MD/XD, N 28/20 40/44 35/37120/67 Grab ten6ile MD/XD, N 160/102 200/182 218/245 240/151 Mullen bur6t, kPa 117 234 255 372 Frazier permeability, m3/m2/min 222 134 126 762 ComPosite Unit weight, g/m2 62 92 88 109 % Furnish 45.3 50 50 53 4 Thicknes6, mm 0.12 0.14 0.220.22 Strip tensile MD/XD, N 32/28 58/58 46/42106/79 Grab tensile MD/XD, N 107/80 142/142 182/151 243/142 Finch tear, 12S~98~

MD/XD, N 80/58 213/lS1 98/134 102/111 Mullen burst, kPa 150 178 267 400 Gurley porosity 2930 1010 778 1000 Moisture vapor transport, g/m2/day 559 670 525 670 Taber abrasion, cycles, (500 gm weight) 71 74 130 60 A8 can be seen from the cesults shown in Table III, a wide variety of properties can be obtained in the f~nal composite sheet, depending on the starting scrim material.
ExamDle 9 Thi6 example of various composite sheets of the invention made with different polyolefin synthetic pulps not only illu~trates the advantage of composite sheets over pulp papers in abrasion resistance but also demonstrates that certain synthetic pulps have a several fold advantage in producing high air and water barrier proeerties at light pulp add-ons.
ln the same manner a6 described in Example 6, scrim-pulp composites were formed with Reemay~ spunbonded polyester continuous filament scrim and the following polyolefin synthetic pulps.
Z5 a. Pulpex~ A-121 b. Pulpex~ EA
c. Fybrel~ R-2005/13020F
d. Pulpexæ PAC-C
e. Fybrel~ E-380/13038F
f. Pulpex~ ED
All the Pulpex~ pulps are sold by Hercules Corp. and the Fybrel~ pulp8 are sold by Mitsui Petrochemical lndustries Ltd., Tokyo, Japan. All of these synthetic pulps are of polyethylene except Pulpex~
PAC-C, which is of polypropylene. The properties of ~8 the pulps and of the resultant composite sheets are summarized in Table V.
Table V
Test No. 9a 9b 9c 9d ge 9f SYnthetic PU1P a b c d e f Drainage factor 4.23 1.96 1.59 0.75 0.73 0.57 Fiber retain 91 93 56 87 57 91 Surface area, mZ/g 13.3 10.7 7.4 5.0 3.8 4.B
Mean diameter, micron 5 10 5 Z0 10 40 comPosite (for different pulp add-ons) Gurley porosity 17.0 g/m2 620 25 4.4 0.8 0.5 2.0 33.9 g/m2 2830 396 12B 5 5.8 22.7 67.8 g/m2 ~ 4760 1130 Z9 1190 96 Hydrostatic head, cm 17.0 g/m2 118 48 39 34 25 21 33.9 g/m2 ** 90 56 63 70 45 67.8 g/m2 ** 130 102 104 130 102 Taber abrasion, cycles 33.9 g/m2 500 133 94 21 21 61 PulP Paper Control Taber abrasion, cycles 33.9 g/m2 24 * very high, greater than about 5000 sec/100 cm3/6.45 cm2 **very high, greater than about 130 cm.

Claims

What is claimed is:

1. A calendered composite nonwoven sheet characterized by a nonwoven continuous filament scrim and an abrasion resistant pulp layer comprising at least 50% by weight of polyolefin synthetic pulp, the scrim and the pulp layer being adhered to each other by an adhesive binder.

2. A composite sheet of claim 1 wherein the pulp layer contains woodpulp amounting to no more than 50% by total weight of the pulp layer.

3. A composite sheet of claim 2 wherein the woodpulp amounts to no more than 30% of the pulp layer.

4. A composite sheet of claim 2 wherein the woodpulp amounts to no more than 10% of the pulp layer.

5. A composite sheet of claim 1 wherein the pulp layer contains an adhesive binder amounting to no more than 20% by total weight of the pulp layer.

6. A composite sheet of claim 5 wherein the pulp layer contains an adhesive binder amounting to no more than 10% by weight of the pulp layer.

7. A composite sheet of claim 1 wherein the scrim includes an adhesive binder amounting to no more than 10% by total weight of the scrim.

8. A composite sheet of claim 7 wherein the amount of the adhesive binder is in the range of 3 to 8% by weight of the scrim.

9. A calendered composite nonwoven sheet characterized by a nonwoven scrim of continuous filaments of synthetic organic polymer adhered by an adhesive binder to an abrasion-resistant pulp layer comprising a polyolefin synthetic pulp, the scrim weighing in the range of 15 to 85 g/m2 and containing an adhesive binder in an amount in the range of 3 to 8% by total weight of the scrim, and the pulp layer weighing in the range of 15 to 70 g/m2 and comprising by total weight of the layer at least 70% polyolefin synthetic pulp, no more than 30 woodpulp and no more than 20% adhesive binder.

10. A calendered composite sheet of claim 9 particularly suited for use as a house air infiltration barrier, the scrim weighing in the range of 25 to 50 g/m2, the pulp layer weighing in the range 15 to 30 g/m2 and having a woodpulp content in the range of 3 to 10%, and the composite sheet having a strip tensile strength of at least 25 Newtons, a grab tensile strength of at least 75 Newtons, a hydrostatic head of at least 25 cm, and a moisture vapor transport of at least 400 g/m2/day.

11. A calendered composite sheet of claim 9 particularly suited for outdoor signs and banners, having the scrim weighing in the range 30 to 60 g/m2, the pulp layer weighing in the range of 20 to 40 g/m2 and having a woodpulp content in the range of 3 to 30% and the composite sheet has a grab tensile strength of at least 75 Newtons, an Elmendorf tear strength of at least 5 Newtons and a Mullen burst strength of at least 125 kiloPascals.