US3284276A - Coated cellophane article and process for obtaining the same - Google Patents

Description

United States Patent 3,284 276 COATED CELLOPHANE ARTICLE AND PROCESS FOR OBTAINING THE SAME Morris B. Berenbaum, Levittown, Pa., Rolf F. Foerster, Hamilton Square, N.J., Riad H. Gobran and David C. Goth, Levittown, Pa, Ronald F. Snyder, Bordentown, N.J., and Theodore F. Wells III, Morrisville, and Arthur J. Yu, Lcvittown, Pa., assignors to Thiokol Chemical Corporation, Bristol, Pa., a corporation of Delaware N0 Drawing. Filed Nov. 6, 1962, Ser. No. 235,839 9 Claims. (Cl. 161-184) The present invention relates toa novel composition and process for the coating of cellulosic materials such as cellophane, Wood and paper, including cardboard, cylinder board and paper board. More particularly the present invention relates to a novel solution system containing a polyepoxide and a copolymer of vinylidene chloride and an il-unsaturated carboxlie acid or an anhydride of such acids which may be used to coat cellulosic substrates.

This is a continuation in part, of application S.N. 215,- 290, entitled Cellophane Coating Composition and Process, filed in the name of Morris B. Berenbaum et. on Aug. 17, 1962, now abandoned.

An object of the present invention is to provide a composition with which coatings can be readily and economically imparted to cellulosic substrates, and in particular those cellulosic substrates which are customarily employed as flexible films in the packaging industry such as cellophane or the various types of paper such as lcnaft paper and glassine.

Another object of the present invention is to provide a coating composition which will allow the imparting of coatings to cellulosic substrates which are clear and have excellent heat sealing and solvent and grease resistance as well as good adhesive (to substrate) and vapor impermeability properties.

A further object of this invention is to provide a process whereby cellu'losic substrates may be readily coated with such compositions.

A still further object of the present invention is to provide for the preparation of fire resistant, flexible laminates made of cellulosic substrates.

Cellophane, wood and paper are all cellulosic in nature, wood being a natural product and paper being processed from wood pulp. Cellophane is a form of regenerated (from viscose) cellulose in transparent sheet form. Cellophane and paper are used as packaging materials for many applications, including, the packaging of food items, cigarettes and other tobacco products, items of apparel, etc. For the cellophane to be flexible enough for such applications it should contain a certain quantity of water. This amount of water, moreover, must be sealed in the cellophane by coating the cellophane with a coating having good moisture impermeability properties. The coating also prevents the cellophane, in rolled form from blocking during storage. If the coated cellophane or paper is to come in contact with grease or oil, moreover, such as in various food packaging applications, the coating must also be grease and oil resistant. Polymeric cellophane coating materials of this type include vinylidene chloride/acrylonitrile copolym ers, vinylidene chloride/ alkyl acrylate copolymers and vinylidene a,,8-unsaturated carboxylic acid copolymers such as are disclosed in US.

3,284,276 Patented Nov. 8, 1966 2,334,236; 2,748,027; 2,762,720; 2,805,963; 2,819,984; 3,034,929; 3,037,868; 3,039,986 and Great Britain 889,- 564. In order to coat the cellophane with these type polymers, however, it is usually necessary to first treat the cellophane with an anchoring agent whereby a useful degree of adhesion between the film and the cellophane base sheet may be obtained. Even when these anchoring agents are used with many of the commercially available cellophane coating materials, however, the degree of adhesion obtained between the base sheet and the film coating is inadequate for many applications. The solvent and grease resistant properties of the coating obtained with these polymers, moreover, is limited to that afforded by the polymers themselves and there has been no way known to the art, to date, to vary or improve such properties for cellophane coating applications. There are many applications also which require that wood substrates used therein be protected with coatings which are resistant to penetration or attack by moisture, grease, solvents and the like.

It has now been unexpectedly found, according to the present invention, that cellulosic substrates may be readily coated with a clear coating which has good adhesion to the cellulosic substrate as well as excellent heat sealing and solvent and grease resistant properties and good vapor impermeability properties if the substrate is first coated with a solution containing:

(a) At least one polyepoxide compound, and

(b) At least one copolymer of vinylidene chloride and at least one a,flunsaturated carboxylic acid or an anhydride or such acids and the polyepoxide is then reacted with the copolymer to form a crosslinked reaction product concurrent with and/ or subsequent to the removal of the solvent medium.

To our knowledge, the present invention represents the first successful attempt to those in the art to use an epoxy crosslinked, vinylidene chloride/a,,8-unsaturate-d carboxylic acid copolymer for coating cellulosic substrates and in particular, cellophane, although epoxy crosslinked carboxyl group containing copolymers have been used extensively for other purposes: i.e., US. 2,604,457; 2,604,- 463; 2,604,464; 2,965,602; 2,662,870; 2,759,901; 2,798,- 861; 2,969,602; 2,985,616 and 3,027,357; Canadian 534,- 001; 534,261 and 569,430 1 nd Great Britain 681,031 and 896,821.

The vinylidene chloride copolymers of the present invention are relatively low molecular weight particulate materials which contain about to 95 and preferably about mol percent of vinylidene chloride and about 5 to 25 and preferably about 15 mol percent of at least one unsaturated a,/3-oarboxy'1ic acid such as acrylic, met-h- -acrylic, itaconic and crotonic acids or anhydrides of such acids. They are random copolymers which are soluble in selected solvents such as tetrahydrofuran, ethyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, dimethyl formamide and dioxane and cosolvent systems such as those containing at least 50% by volume of tetrahydrofuran and at least one solvent diluent such as toluene and methylene chloride.

The copolymers are preferably formed by means of a. free radical polymerization reaction using about 0.1 to 4% by weight of a catalyst such as azobisisobutyronitrile or benzoyl peroxide. The reaction is preferably conducted in solution in a solvent such as hexane, methylisobutylketone, methyl ethyl ketone, acetone or 50/50 (by volume) acetone/ toluene. tion may also be conducted using suspension and emulsionpolymerization techniques. The copolymers produced should preferably be freed of heavy metal contaminants, such as iron, for stability purposes.

The polyepoxides which may be used in the novel compositons and processes of the present invention are those which contain an average of more than one epoxide group per molecule and which are soluble in the desired solvent. Generally speaking, all the polyepoxide materials commercially available today may be used in the composition and processes of the present invention, whether they are solid or liquid materials. The polyepoxy materials which can be cured with the above described :copolymers are preferably those materials which have an average epoxy functionally of more than one and preferably they are materials which contain an average of at least approximately two epoxide groups per molecule of the po lyepoxy material. The position of the epoxide groups in the polyepoxy material is not critical. For instance, if the polyepoxy material is essentially linear in structure the epoxide groups maybe in a terminal position or they may be positioned intermediately and/or randomly along the linear structure. Polyepoxy materials which may be cured with the above defined copolyr neirs inolude the following types of materials:

(1) Essentialy linear type such as homopolymers and copolymers of glycidyl acrylate and preferably a copolymer of vinylidene chloride and glycidyl acrylate and the epoxidized polybutadiene materials such as those which have an epoxide functionality of four or more and which are sold by Food Machinery Corporation under the designation Oxiron resins (i.e., Oxiron 2000, Oxiron 2001 and Oxiron 2002).

(2) Bisphenol A/epichlorohydrin type which are aromatic in nature and which include those sold by the Thiokol Chemical Corporation under the trademark designation Tipox (i.e., Tipox A; Tipox B; Tipox C) those sold by the Shell Chemical Company under the designation Epon resins, i.e., Epon 828 and those sold by Union Carbide Chemicals Company under the designation Bakelite ERL resins.

(3) Cycloaliphatic type which includes those sold by Union Carbide Chemicals Company under the designation Unox resins (i.e., Unox 206" which is epoxy ethyl- 3,4-epoxy cyclohexane, Unox 201 which is 3,4-epoxy- 6 methylcyclohexylmethyl 3,4-epoxy-6-rnethylcyclohexanecarboxylate, Unox 221 which is 3,4-epoxy-cyclohexylmethyl-3,4-epoxy cyclohexane carboxylate and Unox 289 which is bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate.

(4) Resorcinol diglycidyl ether type which includes those sold by Koppers Chemical Corporation under the designation Kopoxite resins (i.e., Kopoxite 159).

- (5) Epoxy novolak type (alkyl novolak resins) which is a phenolic/epoxy type system and which includes the resins sold by Dow Chemical Corporation under the designation Dow Epoxy Novolak 438 or DEN 438EK 85 which contains 85% of the resin and 15% methyl ethyl ketone as a solvent and the resins sold by Koppers Chemical Corporation under the designation KER resins (i.e., KER 357A and KER 955A).

The polymerization reac- (6) Epoxidized fatty acid resins including the Epoxol materials sold by Swift and Company such as Epoxol 95 (epoxidized linseed oil) and Epoxol 7-4 (epoxidized soy bean oil); the Flexol resins sold by Union Carbide Chemical Company, such as Flexol EPS (2- ethyl hexyl epoxy tallate). Flexol EPO (epoxidized soy bean oil) and Flexol TPO (epoxidized soy bean oil) and Paraplex G62 (epoxidized soy bean oil) sold by Rohm & Haas.

(7) Epoxidized silicone oil types such as that marketed by Dow Corning under the trade name Epoxy Silicone QZ, e.g., Epoxy Silicone QZ8-0914.

For the purpose of obtaining the approval of the Food and Drug Administration of the Department of Health,

Education, and Welfare for the cellophane coating compositions of the present invention in food packaging applications, the epoxidized fatty acid type polyepoxides are the preferred of such compounds. The Unox resins, and in particular the Unox 201 and Unox 289 type resins are preferred of the polyepoxide compounds for room temperature curing applications. The higher the functionality of the polyepoxide compound, the tighter the cure that is obtained usually, all other factors remaining the same and for some applications such higher functional polyepoxide materials are preferred. The use of glycidyl acrylate copolymers, such as, a copolymer of vinylidene chloride and glycidyl acrylate is preferred in those applications where a less plasticized coating'is desired for better coating surface properties.

Tipox B resin is preferred for those coatings requiring good clarity and heat sealing properties.

The polyepoxide/copolymer solution systems of the present invention offer unique handling and processing advantages to the trade. They are essentially one package curing systems and are stable upon storage for extended periods of time. Their solids content can be readily varied to meet the need for various types of applications. Those in the trade seem to prefer a solution having a solids content of about 15 to 35% by weight. By solids content it is meant, the percent by weight of those components of the solutions which are not solvents, even though one or more of the other components, such as the polyepoxide materials, may be liquid under normal conditions. The solution nature of these systems also provides for a facile incorporation therein of adjuvant materials such as pigments, dyes, delustrants, plasticizers, waxes, fillers, stabilizers, etc., when desired. Solvents which may be used in the preparation of the coating solution of the present invention include methyl ethyl ketone, tetrahydrofuran, methyl isobutyl ketone and solvent mixtures containing no more than about 75% toluene and the remainder tetrahydrofuran, methyl ethyl ketone and/or ethyl acetate. The preferred solvents are methyl ethyl ketone or a mixture of toluene with methyl ethyl ketone or ethyl acetate.

In coating cellulosic substrates according to the present invention, a solution containing the polyepoxide and the copolymer is applied to the substrate on one or more faces or sides thereof as desired, so as to provide each face or side of the substrate being coated with a film which is at least about 0.05 and is preferably about 0.1 to 1 mil thick after the removal of the solvent therefrom. The coatings may be applied by any of the commonly used dipping, brushing, roller coating, etc., techniques known to the art. The viscosity of the coating may be varied to suit the manner of application by adjusting the solids content of the coating solution. The solvent is then removed preferably at elevated temperatures under forced draft conditions. The temperatures employed with cellophane substrates is preferably about to C. and with glassine substrates temperatures as high as about 200 to 210 C. may be used. At these tempeartures the removal of the solvent and the crosslinking of the copolymer and the polyepoxide can be accomplished, simultaneously in a matter of seconds. At 150 C., the removal of the sol- 6 fected. For use under extreme conditions the adherence of the coatings of the present invention to the cellulosic substrate can be supplemented by use of commonly employed anchoring agents such as melamine/formaldehyde room temperature. The crosslinking reaction involves the and urea/formaldehyde resins. reaction of the carboxyl groups of the copolymer with the The carboxylic acid moieties supply the copolymers of epoxy groups of the polyepoxide. About 0.01 to 2.5 and the present invention, for the most part, with its solubility preferably about 0.1 to 110 mol of epoxide moieties properties in addition to supplying the copolymer with the should be provided per mol of carboxyl moieties to incarboxyl groups needed to subsequently anchor the coatsure adequate cross/linking sites. Catalysts such as ter- 10 ing to the cellulosic substrate and crosslink with the epoxy tiary amines, BF and BF complexes may be used to groups of the polyepoxide compounds. The solubility of facilitate the crosslinking reaction when using certain of the copolymers can also be varied, if desired, by varying the polyepoxide materials such as the epichlorohydrin/bisthe molecular weight of the copolymer. The vinylidene phenol A type. Useful products may be obtained with chloride units of the copolymer help to supply the needed these polyepoxides, however, without the use of such catvapor impermeability and grease resistant properties to alysts. The use of increased amounts of the longer the crosslinked coating. The polyepoxide materials supchained (aliphatic/ fatty acid) type polyepoxides tends to ply the epoxide groups needed to crosslink the copolymer produce tacky and self-adhering coatings which are parvia its carboxyl groups. It is the crosslinked and/or chain ticularly useful for some packaging applications. extended nature of the coatings of the present invention The coatings produced according to the present invenwhich provides its excellent solvent resistant properties. tion are normally crosslinked and/ or chain extended into The polyepoxide materials also probably imparts adhesive a very high molecular weight form with the application and plasticized properties to the cured coating which is of heat, yet they retain very excellentheat sealing propparticularly useful in a flexible packaging application. erties. If a coating material does not have heat sealing The liquid polyepoxides also act as cosolvents for the properties, its utility in the field of packaging coatings copolymer. It can be readily seen, therefore, that the would be sharply curtailed since heat scalability of the novel coating compositions of the present invention procoated packaging material is a necessary prerequisite to vide those in the art with a versatile coating system, the its universal utility as a wrapping material. components and/or amounts of the components of which The coatings prepared according to the present invencan be readily changed so as to provide for the needs of a tion have much better solvent, grease and scratch resistant vast variety of end use coating applications. properties and are much more resistant to the passage of The following examples are merely illustrative of the moisture therethrough than the coatings presently availpresent invention and are not intended as a limitation upon able for coating cellulosic substrates largely due to the the scope thereof. crosslinked and/ or chain extended nature of the coatings of the present invention. There are, to our knowledge, no EXAMPLES 1 15 crosslinked plastic based coatings for cellulosic substrates Among the vinylidene chloride copolymers wh1ch may commercially available today, all the cellulosic substrate be used to form part of the curable compositions of the coating materials presently available to the art being Present invention are 111056 vinylidene Chloride z) th l ti i t and acrylic acid (AA). Curable copolymers made from The coatings produced by the present invention also those monomers were prepared by solution polymerization provide a much better adhesion of the coating to the celas illustrated in Tables I and II below. They represent a lulosic substrate than has hitherto been thought possible to Wide g of Compositions, Produced using Several those in the art. The coatings of the present invention n y -8 solvent A=methy1is0bwty1ket0n; may be applied to the substrate and used therewith for a vent B=acetone; solvent C=l :1 vol./ vol. mixture of acenumber of li ti i h ut h i h coating tone and toluene, solvent D=n1et hylethyl ketone andsevh d to h ll l i b t t ith th id of th eral free radical polymerization initiators, e.g., initiator called anchoring agents. These anchoring agents are ap- A=E1Z0-bi$-bl1iYf0I1itfile; initiator Y PCTOXlde, parehfly not d d i th preparation f th hulo ie under various polymerization conditlons of temperature substrates coated according to the present invention for and time, to Provide reactive copolymers at Vanous R use in many applications where anchored coatings were centages of conversion of the monomers. In preparing thought to be indispensible. It is thought that a reaction these copolymers, the respective inltiators were dissolved takes place between some of the pendant carboxyl groups in the solvent used and the monomers were then added to of the copolymers of the present invention and various of the initiator solution. The reactions were conducted unthe reactive groups of the cellulosic substrate whereby this der nitrogen in a sealed reaction vessel under autogenous unusual adherence of the coating to the substrate is afpressure.

Table I Charge Charge Mol Initiator Solvent Ex. Percent, VO12/AA V012 g. AA g. In grams Type In ml. Type 03 25 /35 2 A 150 A 73 17 75/25 2 A 150 A 155 2916 /20 4 A 240 A 78 14 80/20 2 A 150 A 78 14 .4 80/20 2 A 150 A 3, 220 405 83/17 80 A 5, 000 D 151 25 83/17 4 A 300 A 161 24.5 83/17 4 A 300 o 151 24.5 83/17 4 A 300 1) 151 24.5 83/17 5 B 300 o 161 24.5 83/17 6 B 300 D 83 10 .8 85/15 2 A 150 A. 83 10.8 85/15 2 A 150 A 171 17 88 12 4 A 300 A 87 7.2 90/10 2 A A Table II Reaction Resin Product Example Conversion, M01 Percent eq. Time, Hrs. Temp., 0. Percent VClg/AA COOH/lOO g. Resin The resin products obtained were soluble in the pot product mixture. They were separated therefrom by precipitation from solution through the addition of ice and water to the pot products, and. by a subsequent scalable and were about 0.2 to 0.3 mil thick. The formulations use in these examples and water vapor permeability values of the coating thus obtained are shown in the following table.

Table III Example 16 17 18 19 20 21 22 23 24 25 26 27 28 Formulation (parts by weight,

grams):

VClz/AA Copolymer 100 100 100 100 100 100 100 100 100 100 100 Flexol E1 8 epoxy resin.

Flexol EPO epoxy resin- Flcxol JPO epoxy resin Epoxol 7-4 epoxy resin Epoxol 9-5 epoxy resin Unox 201 epoxy resin Unox 289 epoxy resin Paraplex G62 epoxy resin Tipox B epoxy resin. Toluene Ethyl Acetate Methyl Ethyl Ketone- COOH/epoxy ratio Specific permeability of cellophane and coating (milligrams/square inch):

High (of 5 samples)- 373 73.6 163 241 101 Low 167 38 .6 52 .8 108 Average 288 56 .5 90 .0 175 47 Specific permeability of coating only milligrams/square inch):

High 76.5 10.9 25.4 40 0 18 34.2 5.7 8.22 17 9 Average 58.8 8 4 14.1 28 9 filtering, fragmentation, Washing with water, further filtering and a subsequent drying of the solids copolymers under vacuum at about C. The copolymers, when dried, are white, particulate materials. Using osometric techniques it has been found that copolymers produced in this manner have number average molecular Weights of about l0,000i2,000.

EXAMPLES 16-28 Cellophane was coated in thirteen diiferent runs (referred to as Examples 16-28) according to the present invention, with various solutions, each of which having about a 15% solids content and composed. of an 84.5 15.5 VCl /AA copolyrner produced as in Examples 1 to 15 and different polyepoxides and solvents as disclosed below. The cellophane was coated on one side using a reverse roll coater commonly employed for coating flexible substrates. The (cellophane delivery) web roll speed was 7.9 feet/minute. After passing over the metering roll, speed was 20 feet/ minute and the winduproll speed was 7.9 feet/minute. After passing over the metering rool,

the solution coated cellophane was passed through two heating zones (ovens), each of which was 12 feet long. The temperature of the first was 200 F. and that of the second was 250 F. The solvent was removed and the curing of the coating occurred substantially in these heating zones. The coatings thereby obtained were heat Specific permeability (Weight gain in mg) (thickness of film in mils) (exposed area) (ASTM E9653T). Coatings having similar properties may also be prepared using other VCl /AA Copolymers prepared as in Examples 1 to 15.

EXAMPLE 29 A vinylidene chloride/glycidyl acrylate (VCI /GA) copolymer was prepared by polymerizing g. of vinylidene chloride and 38 grams of glycidyl acrylate in 300 ml. of methyl ethyl ketone at 65 C. using 5 grams of azobisisobutyronitrile as a polymerization initiator. The reaction took 2 hours. The copolymer was recovered in 46.5% yield as a white, solid, particulate material by 9 precipitating it from the polymerization solution into two volumes of 80/20 by volume methanol/water and then washing the precipitated copolymer with the same nonsolvent mixture. The copolymer was then dried and clear solutions of it in tetrahydrofuran at 20% solids indicated that very little, if any, crosslinking of the VCl GA copolymer had occurred. The copolymer had a molecular weight of about 10,000i2,000 and contained 88 mol percent vinylidene chloride and 12 v. mol percent glycidyl acrylate.

EXAMPLES 30-32 Cellophane was coated in three different runs (Examples 30-32) according to the present invention with three different solutions, each of which having about a 15% solids content and composed of an 84.5/15.5 VCl /AA copolymer, tetrahydrofuran as the solvent and, as the polyepoxide component, and 88/12 mol percent ratio VCl GA copolymer produced as in Example 29.

The cellophane was hand coated (on one side) with these solutions and the coatings were cured for 20 seconds at 300 F. The resulting coatings were heat sealable and were about 0.2 to 0.3 mil thick. The formulations used for these coatings and the water vapor permeabilities of the resulting coated cellophane materials are shown below.

Formulation (parts by weight, grams):

VCl/AA 5 5 VCI/ GA 3. 45 5.18 6. 9 Tetrahydrofuram 48 -57. 7 67. 5 Epoxide/COOH ratio (by equivalents) 0.5 0.75 1.00 Specific pcrmeabilities (milligrams/square inch), cellophane base sheet and coating:

High 32. 8 20. 4 20. 1 Low 13.1 11.3 11. 4 16.9 15. 1 16. 3

3. 27 3. 33 3. 72 1. 98 1. 85 2. 12 Average 2. 55 2. 46 3. 03

The results indicate that the coatings of the present invention have good, reproducible, water vapor permeability properties even when applied with crude coating techniques.

EXAMPLE 33 Stock polyepoxide solutions 1 to 18 were prepared so as to contain 15% solids using Oxiron 2000 resin in Cellosolve acetate (soution 1); diacetone alcohol (solution '2), and toluene (solution 3); Tipox B resin in methyl isobutyl ketone (solution 4), chloroform (solution 5) and Solvesso 150/Cellosolve acetate (in 9/1 wt./wt. ratio) (solution 6); Unox 221 resin in acetone (solution 7), cyclohexane (solution 8) and methanol (solution 9); Kopoxite 159 resin in butyl Cellosolve acetate (solution 10), trichloroethylene (solution 11) and ethanol (solution 12); KER 357-A resin in dimethyl formamide (solution 13), methylene chloride (solution 14) and xylol (solution 15) and Epoxol 9-5 resin in dioxane (solution 16), benzene (solution 17) and butyl acetate (solution 18).

Further, two stock solution of a VCI /AA copolymer were prepared: Solution I contained 15% solids in tetrahydrofuran and Solution II contained 15% solids in a 1:1 mixture by weight of methyl ethyl ketone and ethyl acetate. The copolymer contained vinylidene chloride and acrylic acid in an 84.5/ 15.5 mol ratio and was made as in Examples 1 to 15.

Coating solutions A to R were then prepared by mixing together various weights of the stock polyepoxide and VCl /AA copolymer solutions according to the schedule in Table IV, below, to produce solutions containing epoxide/carboxyl ratios in equivalents of 2, 1 and 0.5.

Table IV Grams of Ratio Coating Poly- Poly- VClz/AA Grams of Epoxide/ Solution epoxide epoxide Solution VClz/AA Oarboxyl Formed Solution Solution Used Solution Equivalents Used Used Used in the Goating Solutions 1 00 I 2 2 30 I 100 1 3 15 I 100 0.5 4 04 I 100 2 5 32 I 100 1 6 16 I 100 0.5 7 44. 6 I 100 2 8 22. 3 I 100 1 9 11. 2 I 100 0.5 10 43 I 100 2 11 21. 5 II 100 1 12 10. 75 II 100 0. 5 13 66. 6 II 100 2 14 33. 3 II 100 1 15 16. 7 II 100 0. 5 16 5. 9 II 100 2 17 29. 5 I1 100 1 18 15 II 100 0. 5

Various cellulosic substrates, namely 35 lb. unwaxed kraft type paper and uncoated wooden medical-type tongue depressor sticks were dip coated with each of coating solutions A to R and cured at 83 F., for about 16 hours.

Adhesion of the coatings to the substrates was then tested. The coatings were scored with a razor to form a diamond shaped cut. Pressure sensitive type (cellophane-type) was pressed onto the cut areas and surrounding coated surface, and then quickly removed by pulling. No delamination occurred as a result of this test, all coatings were securely bonded to their respective substrates.

EXAMPLE 34 Two stock solutions were prepared: Solution Y being 15% solids of an 845/ rnol ratio VCl /AA copolymer prepared as in Examples 1-15 in tetrahydrofuran, and solution 2 being 45 g. of the epoxidized silicone oil Epoxy Silicone QZ8-0914 in 25 g. of toluene (this oil has an epoxide equivalent of A coating solution was then prepared to contain a 1/1 ratio of equivalents of epoxy/carboxyl by mixing together 31 g. of solution Z with 100 g. of solution Y. Various cellulosic substrates i.e., 35 lb. unwaxed kraft paper and uncoated wooden tongue depressor sticks were then dip coated with this coating solution at room temperature and the resulting coatings were cured in air for about 15 minutes at 78 F. to produce coated objects wherein the adhesion of the cured coating to the substrate was excellent in each case.

EXAMPLE 35 Paper materials are often used as inexpensive gasketing, the useful work-life thereof being determined by the length of time in which these materials retain their flexibility and impermeabilit'y. Wood used in contact with water also has a useful working life dependent upon its resistance to the absorption of water. In this example samples of paper and wood were used as substrates, said substrates being normally highly water absorbent. The paper used was laboratory filter paper, and the wood used was an uncoated medical tongue depressor. One half of the paper and wood were dip coated with a 40% solids coating solution comprising 20 parts by weight (p.b.w.) of a vinylidene chloride/ acrylic acid copolymer having a VCl /AA mol percent of 845/155 and prepared as in Examples 1-15 and 3 p.-b.w. of the polyepoxide resin Epoxol 9-5 in 34.5 p.-b.w. of the solvent system tetrahydrodrofuran/toluene (1/1 wt./wt.). The solution had a ratio in equivalents of epoxide/carboxyl of 0.5/1. The coatings were permitted to air cure for 8-10 hours at about 80 F. to produce thereby cellulosic structures being in part uncoated and in part coated with a cured coating. The coated portion of the paper structure was still quite flexible and when both portions, the coated and uncoated portions, were immersed in a stream of water the uncoated portion quickly became wet and readily absorbed Water whereas the coated portion did not absorb water, the drops of water readily rolling off the coated surface. Similar observations were made with regard to the coated and uncoated portions of the wooden depressor stick.

EXAMPLE 36 Glassine paper, which is a heat and pressure treated nonporous smooth and translucent paper material, is often used in the packaging of food stuffs and other substances. In this example, glassine paper was used as the substrate material and was coated with various polyepoxide-vinylidene chloride (VCl acrylic acid (AA) copolymer coating solutions. The VCl /AA copolymer had a mol ratio of 845/155 VCI /AA and was prepared as in Examples 1-15. Solutions were prepared according to the recipes psi. pressure for 75 min. to produce, in one instance a nine ply laminate designated Laminate A. In another instance another 9 ply laminate, Laminate B, was produced by heating nine coated squares, placed one atop the other, to a temperature of 300 F. under an impressed pressure of 1000 psi. also for 75 min. The laminates obtained showed excellent resistance to attack .by trichloroethylene vapor this being an important property of laminates useful in the making of printed circuit components. The solvent vapor resistance test used involves exposing a 2" x 3" piece of laminate to an atmos phere of trichloroethylene vapors at a pressure of 760 mm. Hg for a 5 minute interval, drying the laminate at ambient temperatures for 24 hours and then inspecting the laminate for leeohout of the laminating resin.

The recipe and laminating conditions used, and the properties obtained for laminates A and B are listed in the table below.

given in the table below to form mixtures having a 25% L min te Lamin te solids content in a 1/1 by weight solvent system of a A a B a methyl ethyl ketone (MEK) /ethyl acetate (EA). The solutions were applied to one surface side of squareso'f Recipe ofvarnish p b vv; glassme paper so as to form wet films 2-3 mils thick C copolymer 100 Tipox A resin.... 80 80 thereon. The coated glassme paper was an dr1ed for BFaMEA 3 3 about 1 min. at about 80 F., and then was subjected to 5?:= 1 1 300 F. temperatures for 5 minutes to produce thereby y g 2 2 cellulosic structures in which the cured organic coating 3g 5% obtained was smooth, bubble-free and found to be strongly 1,000 1, 000 adherent to the glassine paper substrate. The pressure 9 serlilsltive tapehtest was used to determine the qualities of ness, hi ch 0,1028 0. 06:

peci1cgraviy 6 .4 ad eslon of t e cured coating to the paper substrate. In FlexumlstrengthnsJn 19,000 187 500 this test pressure-sensitive cellophane tape was firmly Tensilestrength,p.si 8, 6,300 pressed onto the coated surface of the structure in two gf fg gggf gg g 3 places. The first piece of tape was rapidly delaminated Vapor Resistance 5 111111., Trichloro and the second piece slowly delaminated from the coated ethylene (I) (1) surface. In no instance were any of the cured coatings removed or loosened from the glassine paper substrate. Excellent- Table V Recipe in p.b.w.:

V01 100 100 100 100 100 100 100 100 100 100 100 100 100 100 51 MEiK/EA ago 417 354.5 307.2 389.1 393.6 389.1 345 353.5 332.4 333.6 344.7 345.8 344.7

poxo 9-5 resin 0 5 Epoxol 7-5 resin 39 19.5 Kopoxite 159 resin 21.5 10.8 Unox 221 resin 22.4 11.2 D.E.N.438 resin 29.7 14.9 Tipox A resin 31. 2 15. 6 Oxiron 2000 res 29.7 .9 Ratio of E%uivalcnts,

Epoxide/ arboxyl 1/1 1 1 1/1 1/1 1/1 1/1 1/1 0. 5/1 0. 5/1 0. 5/1 0. 5/1 0. 5/1 0.5/1 0. 5/1 Percent Solids 25 25 25 25 25 25 25 25 25 25 25 25 25 25 EXAMPLE 37 The chemical and solvent resistance of laminates A and Paper laminates having superior resistance to solvent vapors were produced through the use of vinylidene ohloride/ acrylic acid copolymer polyepoxide varnishes as the laminating means.

In this example an impregnating solution, commonly known as varnish in the laminating arts, was prepared by dissolving 100 p.b.w. of an 84.5/ 15.5 mol percent ratio yinylidene chloride/acrylic acid (VCl /AA) copolymer produced as in Example 1-15 80 p.b.w. of the polyepoxide resin Tipox A and 3 p.b.w. of BF -monoethylamine BF MEA) cure catalyst in 123 p.b.w. of methyl ethyl ketone. This varnish was then used to coat 16" x 16" squares of 0.010" cotton linters paper that had previously been treated With Bakelites water soluble phenolic varnish 3913 at a 14.517% resin content; which treatment is a standard precoat or 1st pass treatment in the laminating arts for use with paper and laminating resins. The coated squares of treated paper were then heated to 212 F. for about 1 min. under infra-red radiation to remove the solvent and allow the coating to become dry and tack-free. Nine of the thus coated squares were then placed one atop the other, thence into a laminating press, and there heated to 275 F. under 1000 B was further tested through immersion in 30% H SO carbon tetrachloride and n-heptane for 24 hours at about 73 F. No changes in the laminates were observed, under these test conditions.

We claim:

1. As an article of manufacture a cellophane substrate coated on at least one surface thereof with the reaction product of (A) at least one copolymer essentially consisting of about 75 to 95 mol percent of vinyli-dene chloride and about 5 to 25 mol percent of at least one acid material selected from the group consisting of a,/3-unsaturated, aliphatic caroxylic acid and their anhydrides, and

(B) at least one polyepoxide in an amount such as to provide about 0.01 to 2.5 mols of epoxide groups per mol of carboxyl groups present in said copolymer.

2. An article as in claim 1 in which said polyepoxide contains an average of more than one epoxide group per molecule.

3. An article as in claim 1 in which said acid material is acrylic acid.

4. An article as in claim 1 in which said copoly mer contains about mol percent of vinylidene chloride.

5. A process for coating 2. cellophane substrate comprising applying to at Jeast one surface of said substrate a solution containing (A) at least one copolymer essentially consisting of about 75 to 95 mol percent of vinylidene chloride and about 5 to 25 mol percent of at least one acid material selected from the group consisting of afiunsaturated, aliphatic caroxylic acids and their anhydrides, and

(B) at least one polyepoxide in an amount such as to provide about 0.01 to 2.5 mols of ep-oxide groups per mol of carboxyl groups present in said copolyme-r, removing the solvent medium from said solution, and crosslinking said copolymer with said polyepoxide whereby said crosslinked copoly-mer forms a coating on said substrate.

6. A process as in claim 5 in which the removal of said solvent medium and the crossl-inking of said 00- polyrner occurs substantially simultaneously.

7. A process as in claim 6 in which said solvent medium is removed at elevated temperatures.

8. A process as in claim 5 in which at least one face of References Cited by the Examiner UNITED STATES PATENTS 2,872,427 2/1959 Schroeder 117-145 X 2,909,449 10/1959 Banigan 117-145 2,949,438 8/1960 Hicks 260-23 3,008,914 11/1961 Fry 260-837 X 3,054,428 9/1962 Crawfond 161-184 X 3,207,718 9/1965 Zimmerman et all. 260-296 EARL M. BERGERT, Primary Examiner.

HAROLD ANSHER, Examiner.

Claims (2)

1. AS AN ARTICLE OF MANUFACTURE A CELLOPHANE SUBSTRATE COATED ON AT LEAST ONE SURFACE THEREOF WITH THE REACTION PRODUCT OF (A) AT LEAST ONE COPOLYMER ESSENTIALLY CONSISTING OF ABOUT 75 TO 95 MOL PERCENT OF VINYLIDENE CHLORIDE AND ABOUT 5 TO 25 MOL PEERCENT OF AT LAST ONE ACID MATERIAL SELECTED FROM THE GROUP CONSISTING OF A,B-UNSATURATED, ALIPHATIC CARBOXYLIC ACIDS AND THEIR ANHYDRIDES, AND (B) AT LEAST ONE POLYEPOXIDE IN AN AMOUNT SUCH AS TO PROVIDE ABOUT 0.01 TO 2.5 MOLS OF EPOXIDE GROUPS PER MOL OF CARBOXYL GROUPS PRECENT IN SAID COPOLYMER.

5. A PROCESS FOR COATING A CELLOPHANE SUBSTRATE COMPRISING APPLYING TO AT LEAST ONE SURFACE OF SAID SUBSTRATE A SOLUTION CONTAINING (A) AT LEAST ONE COPOLYMER ESSENTIALLY CONSISTING OF ABOUT 75 TO 95 MOL PERCENT OF VINYLIDENE CHLORIDE AND ABOUT 5 TO 25 MOL PERCENT OF AT LEAST ONE ACID MATERIAL SELECTED FROM THE GROUP CONSISTING OF A,BUNSATURATED, ALIPHATIC CAROXYLIC ACIDS AND THERI ANHYDRIDES, AND (B) AT LEAST ONE POLYEPOXIDE IN AN AMOUNT SUCH AS TO PROVIDE ABOUT 0.01 TO 2.5 MOLS OF EPOXIDE GROUPS PER MOL OF CARBOXYL GROUPS PPRESENT IN SAID COPOLYMER, REMOVING THE SOLVENT MEDIUM FROM SAID SOLUTION, AND CROSSLINKING SAID COPOLYMER WITH SAID POLYEPOXIDE WHEREBY SAID CROSSLINKED COPOLYMER FORMS A COATING ON SAID SUBSTRATE.