US 3589978 A
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United States Patent PROCESS OF MAKING WATER REPELLENT PAPER USING A FATTY POLYISOCYANATE AND A CATIONIC GUM ETHER AND PRODUCT THEREFROM Marwan R. Kamal, Dhahran, Saudi Arabia, and James L. Then, New Brighton, Minn., assignors to General Mills,
no. No Drawing. Filed Sept. 29, 1967, Ser. No. 671,567 Int. Cl. D21d 3/00 US. Cl. 162-158 8 Claims ABSTRACT OF THE DISCLOSURE In a process of making water repellent paper, including the addition to the aqueous dispersion of cellulosic fibers of (1) an organic polyisocyanate of the formula 'where y is 0 or 1, x is an integer of 2 to about 4 and R is the hydrocarbon group of polymerized fat acids derived from fat acids of 16 to 22 carbon atoms such as dimeryl isocyanate and (2) a quaternary ammonium polygalac tomannan gum ether cationic retention agent, for example quaternary ammonium gum ether.
The present invention relates to a process of preparing paper from cellulosic fibers and to the resulting products. More particularly, it relates to such a process wherein certain organic polyisocyanates and cationic retention aids are added to the cellulosic fibers prior to the formation of sheets from such fibers. The resulting paper has improved properties, especially water repellency and wet strength.
It was recently found that polyisocyanates derived from polymeric fat acids could be used to treat already formed paper and fabrics to give such materials improved water repellency and/ or softness. While this treatment 1s eifective, it does involve a separate and additional step 1n the manufacturing processi.e. the dipping, spraying or the like of a solution or emulsion of the polyisocyanate onto the already formed paper or fabric. Since the polyisocyanates derived from polymeric fat acids are reasonably stable in the presence of water, it was felt that the same could be added to aqueous dispersions of the cellulosic fibers prior to the formation of the same into sheets i.e., paper, non-woven fabrics. However, when this was attempted little, if any, water repellency or sizing was obtained.
We have now discovered that the water repellency and other properties of articles formed from aqueous dispersions of cellulosic fibers can be significantly improved if an organic polyisocyanate derived from polymeric fat acids and a cationic retention aid are added to such dispersions prior to the formation step. Our invention makes it possible to produce paper and other articles having increased water repellency and wet strength Without having to treat the already formed articles in a separate step.
The polyisocyanates useful in our invention have the following idealized structural formula:
where y is 0 or 1, x is an integer of 2 to about 4 and R is the hydrocarbon group of polymerized fat acids derived from fat acids of 16 to 22 carbon atoms. The polyisocyanates of the above formula wherein y is 0 are prepared by converting the polymeric fat acids to the corresponding polymeric fat acid chlorides, reacting the acid chlorides with a metal azide to form the polymeric acyl azides and then heating the acyl azides to produce the polyisocya- 3,589,978 Patented June 29, 1971 nates. This method of preparation can be conveniently illustrated by the following equations (using a dimeric fat acid as an example) The polyisocyanates where y is 1 are prepared by converting the polymeric fat acids to the corresponding polynitriles and then hydrogenating the polynitriles in the presence of ammonia and a catalyst such as Raney nickel to form polyamines. The polyamines are then reacted with phosgene to give the polyisocyanates. This method of preparation can be conveniently illustrated by the following equations (using a dimeric fat acid as an example):
D in the foregoing two series of equations is the divalent hydrocarbon radical of dimerized fat acids and contains 30 to 42 carbon atoms.
The starting polymerized fat acids are prepared by polymerizing ethylenically unsaturated monobasic carboxylic acids having 16 to 22 carbon atoms or the lower alkyl esters thereof. The preferred acids are the mono and polyolefinically unsaturated 18 carbon atom acids. Representative octadecenoic acids are 4-octadecenoic, 5- octadecenoic, 6-octadecenoic (petroselinic), 7-octadecenoic, 8-octadecenoic, cis-9-octadecen0ic (oleic), trans-9- octadecenoic (elaidic), ll-octadecenoic (vaccenic), l2- octadecenoic and the like. Representative octadecadienoic acids are 9,12-octadecadienoic (linoleic), 9,11-octadecadienoic, 10,12-octadecadienoic, 12,15-octadecadienoic and the like. Representative octadecatrienoic acids are 9,12,15- octadecatrienoic (linolenic), 6,9,12-octadecatrienoic, 9,11,13-octadecatrienoic (eleostearic), 10,12,14-octadeca trienoic (pseudoeleostearic) and the like. A representative 18 carbon atom acid having more than three double bonds is moroctic acid which is indicated to be 4,8,12,15-octadecatetraienoic acid. Representative of the less preferred (not as readily available commercially) acids are: 7- hexadecenoic, 9-hexadecenoic (palmitoleic), 9-eicosenoic (gadoleic), 11 eicosenoic, 6,10,14 hexadecatrienoic (hiragonic), 4,8,12,16 eicosatetraenoic, 4,8,12,15,18- eicosapentanoic (timmodonic), 13-docosenoic (erucic), ll-docosenoic (cetoliec), and the like.
The ethylenically unsaturated acids can be polymerized using known catalytic or non-catalytic polymerization techniques. With the use of heat alone, the mono-olefinic acids (or the esters thereof) are polymerized at a very slow rate while the polyolefinic acids (or the esters thereof) are polymerized at a reasonable rate. If the double bonds of the polyolefinic acids are in conjugated positions, the polymerization is more rapid than when they are in the non-conjugated positions. Clay catalysts are commonly used to accelerate the dimerization of the unsaturated acids. Lower temperatures are generally used when a catalyst is employed.
The polymerization of the described ethylenically unsaturated acids yields relatively complex products which usually contain a predominant portion of dimerized acids, a smaller quantity of trimerized and higher polymeric acids and some residual monomers. The 32 to 44 carbon atom dimerized acids can be obtained in reasonably high purity from the polymerization products by vacuum distillation at low pressures, solvent extraction or other known separation procedures. The polymerization product varies somewhat depending on the starting fat acid or mixture thereof and the polymerization technique employed-Le, thermal, catalytic, particular catalyst, conditions of pressure, temperature etc. Likewise, the nature of the dimerized acids separated from the polymerization product also depends somewhat on these factors although such acids are functionally similar.
Attempts have been made to fully delineate the structures of dimerized acids prepared from ethylenically unsaturated acids. These studies have been based largely on the products obtained by polymerizing linoleic acid or the methyl esters thereof or starting materials rich in linoleic acid or methyl linoleate. Paschke and Wheeler, in a study relating principally to the thermal polymerization of normal methyl linoleate, stated that at least two main products had been identified by others as resutling from such polymerization:
Their experimental work then indicated the latter structure predominated in the thermal polymerization product (The Journal of the American Oil Chemists Society, vol. XXVI, No. 6, June 1949, pages 278-83). Moore theorized (using the Diels-Alder mechanism) that the polymerization of linoleic acid would yield a variety of 36 carbon atom acids of high structural similarity (Paint, Oil & Chemical Review, Jan. 4, 1951, pages 13-15, 26-29). Thus it was generalized that a portion of normal linoleic acid having the structure CH -(CH CH= CHCH CH=CH (CH COOH (depicted for convenience as RO=CCC=CR) would be conjugated during the polymerization to the 9,11 acid;
CH (CH CH CH=CHCH=CH(CH COOH (depicted for convenience as ROC=CC=CR') It was then set forth that these acids could polymerize as follows:
Moore further indicated that the 9, 12-linoleic acid could also conjugate to the 10,12 acid and that this acid could self-polymerize or polymerize with the 9,12 or 9,11 acids. It was stated that the polymerizations could be head-ttail as well as head-to-head as depicted above. Moore further stated that in many instances octadecatrienoic acids are present in many of the naturally occurring raw materials rich. in octadecadienoic acids and that the selfpolymerization of said acid could be depicted as follows:
been isolated and that a second reaction probably takes place which could yield a diacid of the structure Ault et al. gave a possible structure for the dimer of methyl a-eleostearate, an ester of an octadecatrienoic acid, as follows:
CH H However, they also postulated that the structure could in fact be more complicated. Thus it was postulated that further cyclic rings were formed due to the high unsaturation giving a compound having the following proposed structure:
CH=CH or \CH(CH2)1C O O OH: on CHCFH(CHZ)7COOCH3 CHa(CHz)aC/ OH CH3(CHz)a-CH (1H (Industrial and Engineering Chemistry, vol. 34, No. 9, September 1942, pages 1120-3.)
Other information obtained is in essential agreement with the above studies. Thus analysis of dimerized acids prepared from linoleic acid rich starting materials using heat alone or heat plus a catalyst, such as an acid or alkaline clay, shows that the product contains structurally similar acids having monocyclic tetrasubstit uted cyclohexene ring structures as Well as acids with two and three rings, such additional rings generally being fused to the six carbon atom ring. Additionally, the clay catalyzed dimerized acids have been shown to contain some aromatic rings according to ultraviolet and infrared spectroscopy. These aromatic rings are believed to be formed by hydrogen transfer (by catalytic action of clay) from the substituted cyclohexene ring to form a substituted benzene ring. Such acids are believed to comprise less than about 20% by weight of the dimerized fat acid. Polymerization of pure oleic acid using a clay catalyst has been shown to yield a mixture of dimerized fat acids of which approximately 25-30% by weight have a tetrasubstituted cyclohexane ring with the remainder being non-cyclic. However, when mixtures of oleic and linoleic acids (such as from tall oil) are polymerized, the resulting dimerized fat acid contains little if any dimer having a non-cyclic structure.
It is thus apparent that the polymerization of the ethylenically unsaturated acids yields complex products. The dimer fraction thereof, generally consisting of a mixture of acids, can be assigned the formula:
where D is a divalent hydrocarbon group containing 30 to 42 carbon atoms. It is also apparent that said divalent hydrocarbon group is complex. However, from the noted studies and other information obtained, it can be seen that a mixture of acids normally results from the polymerization and subsequent fractionation and these acids have structural and functional similarities. Thus such mixture of acids contains a significant proportion of acids having a six carbon atom ring (about 25% or more even when the starting fat acid is a mono-olefinically unsaturated acid such as oleic). The remaining carbon atoms in the divalent hydrocarbon group of such ring containing acids are then divided between divalent and monovalent radicals which may be saturated or ethylenically unsaturated. Such radicals may form one or more additional cyclic structures which are generally fused to the first six membered ring. Such dimeric acids may be considered as having a theoretical idealized, general formula as follows:
R t j-rw-ooon where R and R" are divalent hydrocarbon radicals, R' and R" are monovalent hydrocarbon radicals and the sum of the carbon atoms in R'R"" is 24-36. The ring contains one double bond. It is also understood that the R'R"" radicals may form one or more additional cyclic structures which are generally fused to the first ring. It is further understood that the ring or rings may be saturated such as where the dimer acids are hydrogenated under conditions which convert the unsaturated acids to the corresponding saturated compounds.
As a practical matter, the polymeric fat acids are preferably prepared by the polymerization of mixtures of acids (or the simple aliphatic alcohol estersi.e., the methyl esters) derived from the naturally occurring drying and semi-drying oils orsimilar materials. Suitable drying or semi-drying oils include soybean, linseed, tung, perilla, oiticia, cottonseed, corn, sunflower, dehydrated castor oil and the like. Also, the most readily available acid is linoleic or mixtures of the same with oleic, linolenic and the like. Thus, it is preferred to use as the starting materials, mixtures which are rich in linoleic acid. An especially preferred material is the mixture of acids obtained from tall oil which mixture is composed of approximately 40-45% linoleic and 50-55% oleic. It is also preferred to carry out the polymerization in the presence bf a clay. Partial analysis of a relatively pure dimer fraction (98.5% dimer) obtained from the product prepared by polymerizing the tall oil fatty acids in the presence of by weight of an alkaline montmorillonite clay at a temperature of 230 C. and a pressure of 140 psi. for five hours showed that it was a mixture of C acids, one significant component being HOOC CH2 8-CH I Ho Hydrogenation of such mixture of acids using palladium catalyst yielded the corresponding saturated acids, one significant component thereof being Such mixture of saturated dimerized fat acids was used in the preparation of the dimeryl isocyanate employed in the example of the invention to follow.
The preferred cationic retention aids are that quaternary ammonium polygalactornannan gum ethers which where R R and R are selected from the group consisting of alkyl, substituted alkyl, alkene, aryl and substituted aryl groups, Z is an anion and R is selected from the group consisting of epoxyalkyl and halohydrin groups. Illustrative of the anion Z and Cl-, Br, I and H504". The group R may be further illustrated by the formulae below:
XH C-C-R where X is a halogen atom and R is a divalent alkylene radical having from 1 to 3 carbon atoms. R may be straight or branched chain. Illustrative thereof are If R R and R are the same, they each should preferably contain not more than 4 carbon atoms. If they are not the same and one of such groups contains up to 18 carbon atoms, then the remaining two groups should preferably be methyl or ethyl. If two of such groups are joined to form a ring, then the third group should preferably be methyl or ethyl. Thus, the total number of carbon atoms in R R and R should preferably not exceed 22 carbon atoms and may be as low as 3 carbon atoms.
Quaternary ammonium compounds of the type which may be employed are commercially available. Illustrative of these commercially available compounds are 2,3-epoxypropyl trimethylammonium chloride and 3-chl0ro-2-hydroxypropyl trimethylammonium chloride. The quaternary ammonium compounds may be prepared by reacting a tertiary amine or tertiary amine salt with an epihalohydrin. Tertiary amines having the groups R R and R defined above may be employed. The epihalohydrin employed is one providing the group R defined above. If a tertiary amine is used, R is an epoxyalkyl group. If a tertiary amine salt is employed, R is a halohydrin group as defined above. Illustrative tertiary amine salts are the salts prepared by treating a tertiary amine with hydrochloric acid, sulfuric acid or phosphoric acid.
The preferred tertiary amines are those possessing at least two methyl groups (i.e. R and R attached directly to the nitrogen atom because of their greater reactivity which is maintained even when the third group (i.e. R contains 18 carbon atoms as in dimethylstearyl amine. Other representative tertiary amines are dimethylbenzene amine, dimethyldodecyl amine, dimethyldecyl amine, diethylstearyl amine, diethyldodecyl amine, diethylbenzene amine, triethyl amine, tripropyl amine, tributyl amine, N- ethyl and N-methyl morpholine, N-ethyl and N-methyl piperidine and methyldiallyl amine.
The quaternary ammonium compounds may be prepared by simply mixing equimolar quantities of the epichlorohydrin and tertiary amine (or the salt thereof) in an aqueous system and allowing the reaction to proceed preferably with agitation until formation of the product is complete. When employing the salts, best results are obtained if the pH of the aqueous system is above 8 and preferably between 9 and 10. The resultant addition product is then recovered by vacuum distillation of the unreacted epihalohydrin and amine.
For illustration, the reaction of epichlorohydrin and trimethylamine and also epichlorohydrin and trimethylamine hydrochloride may be shown by the following equations:
(CHON-HCI ClCHgCH-C1E[2 In order to prepare the quaternary ammonium polygalactomannan gum ethers, the above-described quaternary ammonium compounds may be dissolved in a suitable solvent such as water, dioxane or an alcohol and the gum added thereto. Any inert solvent may be employed. Among the suitable alcohols are isopropanol, methanol, ethanol and tertiary butanol. A strongly alkaline catalyst is generally employed to promote the reaction. The reaction occurs at room temperature; however, heat and increased amounts of catalyst increase, the reaction rate. In general, temperatures of at least 30 C. up to 60 C. are preferably employed. The catalyst, when employed, is preferably not used in excess of 0.1 mole per molar weight of anhydroglucose unit. Illustrative of the catalysts which are preferably employed are the alkali metal hy droxides, alkaline earth hydroxides and quaternary ammonium bases, such as sodium hydroxide, lithium hydroxide, potassium hydroxide, calcium hydroxide, ammonium hydroxide and benzyltrimethylammonium hydroxide. After the etherification reaction, the catalyst may be left in the reaction product or neutralized with any suit able acid such as acetic or hydrochloric.
The quaternary ammonium compound is preferably employed in an amount of from 0.02 to 0.1 mole per molar weight of anhydroglucose unit; however, amounts from 0.01 to 0.2 mole are also useful. By varying the amount of quaternary com-pound, varying degrees of substitution (D.S.) are provided.
The preparation of the quaternary ammonium polygalactomannan gum ethers is further described by the following illustrative examples.
EXAMPLE A Into a Readco double-bladed mixer of one quart capacity was added 100 grams of commercial guar flour. To this was added dropwise 100 mls. of water containing 2 grams of sodium hydroxide and 7.6 grams (0.1 equivalent) 2,3-epoxypropyltrimethylammonium chloride. This aqueous solution swelled the guar to give a fluffy product that was easily kept in motion by the Readco Mixer. After the guar and aqueous solution were thoroughly mixed for 5 minutes, the jacket of the Readco was heated with water at 50-55 C. for a period of two hours. The reacted product was then removed, dried and finally ground to pass a 30 mesh screen. One-half of the dried product was washed with methanol in an attempt to remove any unreacted quaternary. Both fractions had the same nitrogen content indicating that the quaternary was attached to the guar by a chemical bond.
EXAMPLES B-G Example A was essentially repeated using the same procedure and varying only the amount of quaternary ammonium compound. A series of products having degrees of substitution (D.S.) of 0.0125, 0.025, 0.05, 0.075, 0.15 and 0.20, respectively, were produced. The D5. of the ether of Example A was 0.10.
8 EXAMPLE H In the same manner as Example A, the product was prepared employing 0.1 equivalent of 3-chloro-2-hydroxypropyl trimethylammonium chloride.
EXAMPLE I Example A was essentially repeated using locust bean gum to yield an ether having a degree of substitution of 0.1.
Another representative cationic retention aid which may be used in the present invention is polyethyleneimine.
As indicated previously, the polyisocyanate and the cationic retention aid are added to the aqueous dispersion of the cellulosic fibers prior to the formation of sheets therefrom. Such addition can take place in the beater or to the already beaten or refined dispersion provided that the dispersion and the additives are reasonably thoroughly mixed. Sheets are then formed from the dispersion using conventional techniques. In this respect the uniform dispersion of the pulp fiber containing the polyisocyanate and cationic retention aid is filtered through a screen which leaves a wet sheet on the screen. This sheet can then be dried to make paper, non-woven fabrics and the like. Any of the commercially available forming machines can be used including the Fourdrinier and cylinder machines. The wet sheets are ordinarily dried at temperatures of 200 F. to 250 F. to a moisture content of less than about 12% and preferably in the range of 6% to 9% by weight. Any conventional drying technique can be used such as steam heated dryers.
The cellulosic fibers can be any of those used in paper making, such as those commonly referred to as sulfite, soda, sulfate, and ground wood stock, or fibers derived from rag, cotton, bast, flax, and stem fibers such as straw, or from repulped broke. The concentration of the fibers in the aqueous dispersion is generally less than about 6% by weight and preferably in the range of 0.5 to 1.0% by weight. The polyisocyanate is added to the aqueous dispersion of cellulose fibers in an amount sufiicient to increase the water repellency of the sheetsformed from such dispersion. Preferably, the polyisocyanate is used in an amount of about 0.05 to 2.5% by weight based on the dry weight of the fiber solids. The cationic retention aid is preferably used in an amount of about 0.05 to 2.5 by weight based on the dry weight of the fiber solids and, in any event, in an amount sufiicient to promote the effectiveness of the polyisocyanate. Both the polyisocyanate and the cationic retention aid can be added as dilute aqueous dispersions. An emulsifying agent should be used with the polyisocyanate to effect a better and more uniform dispersion.
It is to be understood that other conventional additives such as fillers and the like can be added. Representative fillers are talc, CaCO silica and so forth.
The following examples are illustrative of the process and products of the present invention and are not to be considered as limiting. All parts are by weight unless otherwise indicated.
EXAMPLE 1 To a one liter sample of a 0.8% aqueous dispersion of pulp taken from a bleached kraft pulp beaten at 1.6% by weight solids for 30 minutes in a Valley Laboratory Beater were added with mixing 1% dimeryl isocyanate and 1% of the quaternary ammonium guar ether of Example A (D.S. 0.1), the precentages being based on the dry weight of the pulp solids. The dimeryl isocyanate was added as a 1% by weight aqueous emulsion using 0.2% by weight Triton X-ll4 (Rohm & Haas) as an emulsifying agent (Triton X-ll4 is a reaction product of t-octylphenol and 7-8 mols of ethylene oxide). Single handsheets were produced from the resulting mixed dispersion (about 6.5 pH, temperature 25 C.) using a Noble and Wood Handsheet machine. The wet sheets were dried at about 210 F. until dry in appearance. The dried sheets were well sized to water, aqueous alkali and aqueous acid. In contrast, sheets prepared from the aqueous pulp dispersion without additives were not sized at all and with 1% and 2% by weight of the dimeryl isocyanate without the gum ether were only slightly sized.
EXAMPLE 2 To 200 parts room temperature water was added 0.1 part Igepal CO-530 emulsifier (an alkylphenoxypoly (ethyleneoxy)ethanol) and 1 part dimeryl isocyanate. The resulting combination was mixed for about five minutes to disperse the dimeryl isocyanate and then 1 part of the quaternary ammonium guar ether of Example G was added with mixing until the dispersion became viscous (about 15 minutes). This viscous dispersion was added to portions of an aqueous pulp dispersion and handsheets were prepared and dried as in Example I except that the pH and temperature of the aqueous pulp dispersions were varied. The amount of the dimeryl isocyanate and ether retention aid was also varied. The resulting handsheets had the properties as set forth in the following table.
1 Cobb Test T 441 M-Values are grams of water taken up per square meter of paper surface after contact with water 6 inch deep for two (0.125% handsheets) and five-(0.250 and 0.5 handsheets) minutes.
2 The numbers 0.125, 0.250 and 0.5 indicate the percent by weight of each of the dimeryl isocyanate and quaternary ammonium polygalactomannan gum ether used in the various test series, said percent being based on the weight of pulp solids.
3 Water Immersion Test T 491 SM-Values are grams of water taken up by the paper, surface and edges, 6 square inches, after 10 minutes immersiou in water about 3 inches deep.
4 Wet burstValues in pounds after minutes soaking in tap water (average of five tests per handsheet).
The above data show that paper prepared according to the present invention has improved water repellency and wet strength. It also shows that the water repellency is increased somewhat as the pH and temperature of paper manufacture increases (one minute sorption time). The noted improvements are reduced as the amount of dimeryl isocyanate and retention aid are lowered.
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. In the process of preparing paper from an aqueous dispersion of cellulosic fibers, the improvement comprising adding (1) an organic polyisocyanate of the formula:
where y is 0 or 1, x is an integer of 2 to about 4 and R is the hydrocarbon group of polymerized fat acids derived from fat acids of 16 to 22 carbon atoms and (2) a quaternary ammonium polygalactomannan gum ether cationic retention aid to the dispersion before forming the dispersion into sheets, said polyisocyanate being used in an amount sufficient to increase the water repellency of the sheets.
2. The process of claim 1 wherein x is 2 and y is l.
3. The process of claim 2 wherein the quaternary ammonium polygalactomannan gum ether is an ether of a polygalactomannan gum and a quaternary ammonium compound having the formula where Z is an anion, R R and R are radicals containing not more than 18 carbon atoms selected from the group consisting of alkyl, substituted alkyl, alkene, aryl, substituted aryl and cyclic groups formed by joining two of such radicals, and R is selected from the group consisting of H C/CR and XH C-(F-Rqwhere R is a divalent alkylene group having from 1 to 3 carbon atoms and X is a halogen atom.
4. The process of claim 3 wherein R R and R are methyl and the polygalactomannan gum is guar gum.
5. The process of claim 4 wherein R contains 34 carbon atoms and is the divalent hydrocarbon group of the dimerized fat acids derived from the mixture of fat acids obtained from tall oil.
6. The process of claim 5 wherein the diisocyanate is used in an amount of about 0.05 to 2.5% by weight based on the dry weight of the cellulosic fiber solids.
7. The process of claim 6 wherein the quaternary ammonium guar ether is used in an amount of about 0.05 to 2.5 by weight based on the dry weight of the cellulosic fiber solids.
8. The product prepared by the process of claim 1.
References Cited UNITED STATES PATENTS 2,813,093 11/1957 Gordon 162-178 3,058,873 10/1962 Keim 162-178 3,084,092 4/1963 Arlt 162-158 3,236,832 2/ 1966 Opie 162-178 3,448,101 6/1969 Billy 162-175 3,455,883 7/1969 Kamal et a1. 260-453A 3,471,362 10/1969 Kent 162-178 3,499,824 3/ 1970 Strazdins 162-164 S. LEON BASHORE, Primary Examiner R. H. ANDERSON, Assistant Examiner U.S. Cl. X.R. 162-178, 182