GB1566824A

GB1566824A - Flexible polyacid compositions and process for preparation thereof

Info

Publication number: GB1566824A
Application number: GB20122/77A
Authority: GB
Original assignee: Goodrich Corp; BF Goodrich Corp
Current assignee: Goodrich Corp
Priority date: 1976-05-14
Filing date: 1977-05-13
Publication date: 1980-05-08
Also published as: BE854627A; IT1085889B; JPS52139161A; NL7705310A; FR2351151A1; DE2721147A1

Description

(54) FLEXIBLE POLYACID COMPOSITIONS AND PROCESS FOR PREPARATION THEREOF (71) We, THE B. F. GOODRICH COMPANY, a corporation organized and existing under the laws of the State of New York, United States of America, of 277 Park Avenue, New York, State of New York 10017, United States of America (assignee of DAVID LEE MILENIUS), do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to flexible polyacid compositions and to a process for the preparation thereof.

U.S. Patent 3,387,061, British Patent 879,950, and German Patent 1,100,950 teach preparation of flexible, water-insoluble "association products" by reacting polyacrylic acid and a polyether having a molecular weight above 300, more preferably above 1,000, and even more preferably above 4,000. However, polyethers having a molecular weight between 300 and 4,000 have the disadvantage of producing a reaction product that becomes brittle upon prolonged heat treatment and/or aging and is sensitive to cure conditions.

U.S. Patent 3,236,685 teaches imparting antistatic and soil resistant properties to surfaces of articles using the reaction product of a polymer polybasic acid such as polyacrylic acid and a cross-linking agent selected from the group consisting of polyols and polyepoxides. The reaction mixture is heated to a temperature from about 80"C. to about 220"C. to partially cross-link the polymeric polybasic acid so that after cross-linking from l0C/o to 70 Ó of the acid groups of the polymeric polybasic acid are free acid groups. Such compositions suffer from the disadvantage of gradually becoming less flexible as the free acid groups interact and/or react with the polyol plasticizer's hydroxyl groups, thereby reducing plasticizer effectiveness.Furthermore, compositions containing only 10--70P, free acid groups tend to be very sensitive to cure conditions and become brittle readily.

U.S. Patent 2,692,182 teaches that a "durable, stiff finish" may be imparted to nylon by treating it with polyacrylic acid and polyhydric alcohol and heating. Such a stiff finish is undesirable for many applications. U.S. Patent 2,783,212 teaches cross-linking of polyacrylic acid with alcohols or amines but neither discloses nor suggests mixtures thereof. U.S. Patent 2,838,421 teaches production of an "aggressively tacky," water soluble adhesive by reacting a polyvinyl carboxylic acid such as polyacrylic acid with a "hydroxy-polyalkylene permanent elasticizer".

"Glycerine is too hygroscopic and is unsuitable". (Column 4, line 26-27). Tack is generally undesirable in coatings, films and the like.

New polyacid compositions are desired that can be cast from water solutions and dried to tough, flexible forms which are substantially tack-free and retain their flexibility with aging, thereby avoiding the disadvantages of the prior art. The compositions should be variable through the entire range of water solubility from completely insoluble to completely soluble.

According to the present invention a flexible polyacid composition is provided comprising 100 parts by weight of at least one polyacid containing polymerized therein at least 80% by weight of acrylic acid, methacrylic acid or a mixture thereof, and up to about 20% by weight of at least one other vinylidene monomer having at least one terminal CH2C < group, said polyacid having a molecular weight from 50,000 to 2,000,000 and containing an average from 1.0 to 1.7 free carboxylic acid groups per 100 molecular weight units; (2) from 15 to 100 parts by weight per 100 parts by weight polyacid of at least one polyol plasticizer and (3) from 0.25 part to 25 parts by weight per 100 parts by weight polyacid of a cross-linking agent selected from epoxy resins, polyamines and salts thereof, alkanolamines and hydrogen peroxide wherein at least 85% of the carboxylic acid groups of the polyacid remain free acid groups in the flexible polyacid composition.

The composition optionally contains a polyacid solvent, non-solvent, or mixture thereof. The invention includes a process for preparing the composition by heating the reaction mixture to a temperature within the range from 200 C. to 150"C.

Compositions of this invention can be cast from water solutions and dried to tough, flexible films or coatings which are substantially tack-free and retain their flexibility with aging.

A polyacid suitable for use in this invention comprises a polymer of at least 80% by weight acrylic acid, methacrylic acid or a mixture thereof. Acrylic acid is more preferred. The polyacid may have a molecular weight from 50,000 to 2,000,000 and higher, more preferably from 100,000 to 1,000,000. Excellent results were obtained using polyacrylic acid having a molecular weight of 250,000. The polyacid may contain an average of from 1.0 to 1.7 free carboxylic acid groups per 100 molecular weight units.

The polyacid preferably contains copolymerized therein from up to 109at by weight of at least one other vinylidene comonomer having at least one terminal CH2C < group. Suitable vinylidene comonomers include (a) vinyl aromatics having the formula

wherein R' is hydrogen, halogen or an alkyl radical containing from 1 to 4 carbon atoms, such as styrene, a-methyl styrene, chlorostyrene, vinyl toluene, and the like, particularly styrene; (b) vinyl nitriles having the formula

wherein R2 is hydrogen or an alkyl radical containing 1 to 3 carbon atoms, such as acrylonitrile, methacrylonitrile and the like, particularly acrylonitrile; and (c) amides of "B-olefinically unsaturated carboxylic acids containing 2 to 8 carbon atoms such as acrylamide and the like, particularly acrylamide.

Other suitable vinylidene comonomers having at least one terminal CH2=C < group include (d) acrylates having the formula

wherein R3 is hydrogen or an alkyl radical containing 1 to 3 carbon atoms and R4 is an alkyl radical containing 1 to 18 carbon atoms, more preferably 1 to 8 carbon atoms, or an alkoxyalkyl, alkylthioalkyl, or cyanoalkyl radical containing 2 to 12 carbon atoms, more preferably 2 to 8 carbon atoms. Even more preferably R4 is an alkyl radical containing I to 8 carbon atoms. Examples of suitable acrylates included methyl acrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, 2-ethy!hexyl acrylate, dodecyl acrylate, octadecyl acrylate, methoxyethyl acrylate, butoxyethyl acrylate, hexylthioethyl acrylate, p-cyanoethyl acrylate, cyanooctyl acrylate, methyl methacrylate, ethyl methacrylate, octyl methacrylate and the like, particularly methyl acrylate.

Still other suitable vinylidene comonomers having at least one terminal CH2=C < group include (e) monoolefins containing 2 to 14 carbon atoms, more preferably 2 to 8 carbon atoms, such as ethylene, propylene, isobutylene, 1-butene, l-pentene, I-hexene, I-dodecene and the like; (f) dienes containing 4 to 10 carbon atoms, more preferably 4 to 8 carbon atoms, such as butadiene, isoprene, 2 isopropyl-1,3-butadiene, chloroprene, and the like; (g) vinyl and allyl esters of carboxylic acids containing 2 to 8 carbon atoms such as vinyl acetate, vinyl propionate, allyl acetate, and the like; (h) vinyl and allyl ethers of alkyl radicals containing I to 8 carbon atoms such as vinyl methyl ether, allyl methyl ether, and the like; (i) vinyl halides such as vinyl bromide, vinyl chloride and the like; ( ) divinyl and diacrylates such as divinyl benzene, divinyl ether, diethylene glycol diacrylate, and the like; and (k) allyl alcohol and the like.

More preferred vinylidene comonomers having at least one terminal CH2=C < are the (a) vinyl aromatics, (b) vinyl nitriles, (c) amides of a,-olefinically unsaturated acids, and (d) acrylates described heretofore.

Methods of polymerizing and copolymerizing at least one monomer selected from the group consisting of acrylic acid and methacrylic acid are known to the art.

Such methods include those described by Eisenberg et al, J. Polymer Science, Part A-I, Vol. 7, p. 1718 (1969). Kim et al, J. Colloid and Interface Science, Vol. 47, No.

2, p. 531 (1974); McGaugh et al, Polymer Letters, Vol. 5, p. 817 (1967); Schildknecht, Calvin E., vinyl and Related Polymers, John Wiley & Sons, Inc., N.Y., 1952, pp.

298-301; and Encyclopedia of Polymer Science and Technology, Vol. I, pp. 203-205 (1964).

Suitable polyols plasticizers for use in this invention include diols, triols and higher polyols, and glycol ethers having a mlecular weight from 60 to 4,000.

Preferred diols contain from 2 to 12 carbon atoms and may contain up to two carbon-carbon double bonds. More preferred diols contain from 2 to 8 carbon atoms and are fully saturated. Suitable diols include 1,3-propane diol, 1,3 butanediol, 1 ,4-butanediol, 1,5-pentanediol, 1,6-hexanediol and the like. Preferred triols contain from 3 to 12 carbon atoms and are fully saturated or contain a single carbon-carbon double bond. More preferred triols contain from 3 to 6 carbon atoms and are fully saturated, such as glycerine and the like. Excellent results were obtained with glycerine. Preferred higher polyols contain from 4 to 12 carbon atoms, from 4 to 6 hydroxyl groups and are fully saturated or have a single unsaturated carbon-carbon double bond.More preferred higher polyols contain from 4 to 8 carbon atoms, from 4 to 6 hydroxyl groups and are fully saturated, such as pentaerythritol and the like. Preferred glycol ethers are saturated, contain from 2 to 6 carbon atoms per alkylidene group, and have a molecular weight from about 90 to about 4,000, preferably from about 90 to about 1,000, such as diethylene glycol, triethylene glycol, dipropylene glycol and polyethylene glycol. Excellent results were obtained with triethylene glycol.

Epoxy resins suitable for use as cross-linking agents in this invention contain at least two epoxy groups per molecule and have an epoxy equivalent weight (gram molecular weight per epoxy group) below 1,000, more preferably below 500. The epoxy resins may be saturated or unsaturated, aliphatic, cycloaliphatic, aromatic or heterocyclic. Suitable epoxy resins include polyglycidyl esters of polycarboxylic acids, glycidyl ether resins and epoxidized olefins, with glycidyl ether resins being preferred. Suitable glycidyl ether resins include alkanediol diglycidyl ethers such as ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, butanediol diglycidyl ether and the like; alkanetriol triglycidyl ethers such as glyceryl tri glycidyl ether and the like; di- and polyglycidyl ethers of bis(hydroxyphenyl) alkanes; epoxy Novolac resins; and the like.Examples of suitable epoxidized olefins include bis(2,3-epoxycyclopentyl)ether, vinylcyclohexene dioxide, and the like.

More preferred glycidyl ether resins include alkanediol diglycidyl ethers having the formula

wherein X is an alkylidene group containing from I to 10 carbon atoms, more preferably from 2 to 6 carbon atoms, and n is from 1 to 25, more preferably from I to 15. Suitable alkanediol diglycidyl ethers include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, butanediol diglycidyl ether, and the like.

Excellent results were obtained with propylene glycol diglycidyl ether and butanediol diglycidyl ether.

Other more preferred glycidyl ether resins include alkanetriol triglycidyl ethers wherein the alkane group contains from 2 to 10 carbon atoms, more preferably from 3 to 6 carbon atoms, such as glyceryl triglycidyl ether and the like.

Excellent results were obtained with glyceryl triglycidyl ether. Another more preferred class of glycidyl ether resins is the di- and polyglycidyl ethers of bis(hydroxyphenyl)alkanes, such as the polyglycidyl ethers of Bisphenol A having the formula

wherein n is from 0 to 20.

Polyamines and salts thereof suitable for use as cross-linking agents in this invention includes diamines, triamines, higher amines and salts thereof, more preferably diamines and triamines. Other suitable polyamines include amine polymers and salts thereof. The polyamines may be saturated or unsaturated and may be aliphatic, cycloaliphatic, aromatic or heterocyclic.Preferred aliphatic and cycloaliphatic polyamines may contain from 1 to 20 carbon atoms, more preferably from 1 to 10 carbon atoms, and include alkylene polyamines such as ethylenediamine, trimethylenediamine, isobutylenediamine, 1,6-hexanediamine, triethylene tetraamine, tetraethylene triamine, and the like; and dicyandiamide, N,N'-dimethyl ethylenediamine, 1,2-diaminopropane, 2,3-diaminobutane, N-methyl N,N-bis-(-2-aminoethyl)amine, 1,4-diaminocyclohexane, cis- 1 ,4-diaminomethyl- cyclohexane, and the like. Preferred heterocyclic polyamines may contain from 3 to 25 carbon atoms, more preferably from 3 to 20 carbon atoms, and include piperazine, homopiperazine, aminoethylpiperazine, N,N-bis(3-aminopropyl)piperazine, N,N-dimethylpiperazine, 4-methylaminopyridine, diazabicyclo(2,2,2)octane, hexamethoxymethylmelamine and the like.Preferred aromatic polyamines may contain from 6 to 25 carbon atoms, more preferably from 6 to 20 carbon atoms, and include m-phenylenediamine, o-aminobenzylamine, 4,4'-diaminobiphenyl, 4,4'-diaminodiphenylmethane, and the like. Examples of amine polymers and salts thereof include azetidinium chloride polymers and polyvinyl pyrrolidone.

Polyvinyl pyrrolidone polymers suitable for use as a cross-linking agent in this invention may have a molecular weight (Mn) from 10,000 to 500,000, more preferably about 150,000. Excellent results were obtained with dicyandiamide, hexamethoxymethylmelamine, azetidinium chloride polymers and polyvinyl pyrrolidone.

A wide variety of alkanolamines are suitable for use in this invention.

Preferred alkanolamines contain from 2 to 12 carbon atoms, more preferably from 2 to 8 carbon atoms, such as ethanolamine, diethanolamine, triethanolamine, N,Ndimethylethanolamine, N,N-diethylethanolamine, N-methyldiethanolamine, 4amino-l-butanol, 2-amino-2-ethyl- 1 ,3-propanediol, 2 amino-3-methyl- 1 -butanol, 3 amino-3-methyl- 1 -butanol, 2-amino-2-methyl- 1 -propanol, 5-amino-l-pentanol, 3amino-l-propanol, and the like. Excellent results were obtained with triethanolamine.

Preferably the plasticizer does not comprise alkanolamines.

From 15 to 100 parts by weight of plasticizer may be used per 100 parts by weight of polyacid, more preferably from 25 to 75 parts by weight of plasticizer per 100 parts by weight of polyacid. Larger amounts of plasticizer may cause tackiness.

Generally, from 0.25 to 25 parts by weight of cross-linking agent may be used per 100 parts by weight of polyacid, more preferably from 1 to 15 parts by weight of cross-linking agent per 100 parts by weight of polyacid.

The point at which the plasticizer becomes unsuitable or incompatible with the polyacid may be determined readily by a number of methods. Exudation of the plasticizer may indicate incompatibility. Furthermore, increasing the amount of the plasticizer increases the elongation and decreases the tensile strength of the flexible polyacid; therefore, if a film processing high tensile strength is desired, the amount of plasticizer should be kept near the lower limit. Alternatively, more cross-linking agent may be used to enhance tensile strength without reducing plasticizer amount. Similarly, the maximum suitable amount of cross-linking agent may vary from agent to agent and may be determined readily by the man skilled in the art. For example, compositions containing more than 5 parts dicyandiamide per 100 parts by weight of polyacid tend to be brittle.

The polyacids described heretofore are brittle plastics. Moreover, a mixture of a polyacid and either a cross-linking agent or a plasticizer described heretofore is brittle or tends to become brittle upon heating and/or aging. Surprisingly, however, the cross-linking agents enhance retention of polyacid flexibility when used together with at least one plasticizer described heretofore. The probable explanation for this novel result is that the cross-linking agents do not induce substantial polyacid-plasticizer reaction and therefore leave the plasticizer substantially effective as plasticizer. A total of less than about 15 Ó and typically less than about 10% of polyacid carboxyl groups are reacted. Thus, more than about 85% and typically more than about 90% of polyacid carboxyl groups remain free.

Suitable polyacid solvents include water, dioxane, dimethylformamide, and simple alcohols containing from 1 to 5 carbon atoms such as methanol, ethanol and 2-propanol. Suitable polyacid nonsolvents include acetone; diethyl ether; alkanes and cycloalkanes containing from 5 to 10 carbon atoms, such as pentane, hexane, cyclohexane and the like; and aromatic compounds containing from 6 to 14 carbon atoms, such as benzene, toluene, xylene, mesitylene and the like. An aqueous polyacrylic acid solution typically contains from about 5% to about 30% by weight polyacrylic acid based upon a combined weight of polyacrylic acid and water.

A preferred method of mixing the polyacid with plasticizers and cross-linking agents described heretofore comprises dissolving or dispersing each material separately in a common inert solvent or nonsolvent or two different inert solvents or nonsolvents, which are miscible with each other, followed by mixing the separate solutions or dispersions. Another preferred method of mixing comprises dissolving the polyacid and other materials together in a mutually inert solvent. Still another preferred method comprises mixing the polyacid and other materials together in a mutually inert nonsolvent. In the latter process the polyacid and other materials tend to agglomerate as a single mass and are separated readily from the nonsolvent by methods such as centrifugation and the like.

A more preferred method of mixing the polyacid with plasticizers and crosslinking agents described heretofore is by purely mechanical means in the absence of a solvent using a Beken mixer, Banbury, two-roll mill or the like. Another more preferred alternative is to mix a bulk mass of one of the materials with solution(s) of the others.

Drying or conditioning of the mixture may be performed at a temperature from 20"C. to 1500C., more preferably from 500C. to 1000C. Water solubility may be varied widely from complete insolubility to complete solubility by varying plasticizer type and amount, cross-linking agent type and amount, and curing temperature and time. Water solubility was found to decrease with increasing temperature and time of drying or conditioning. The mixture may be recovered from solution by drying in air or under a vacuum.

The flexible polyacid compositions of this invention may be prepared in the presence of, or may have added to them, substantial, even major amounts, of materials which do not form part of the flexible polyacids. If added during preparation of the flexible polyacids, the materials should be chosen so as not to exert an inhibiting effect thereon. Such additives include solvents for the polyacids and other materials described heretofore. Other useful additives include fillers such as calcium carbonate, the neutral clays, mica, carbon blacks and wood flour; and also dyes, pigments, surfactants dispersants, flatting agents and the like.

The present invention will now be further illustrated by way of the following Examples: EXAMPLES 1-16.

In each of the following examples the polyacid used was an acrylic acid homopolymer having a specific gravity of about 1.4 and a molecular weight of about 250,000. A 15% solution of the polyacrylic acid was prepared by sifting 150 grams of the acid into 850 grams of distilled water agitated by a Premier Type SD Dispersator. The mixture was deaerated by allowing it to stand overnight. Two-mil film was then cast from the mixture onto a poly(methyl methacrylate) substrate using a Gardner knife applicator. The film was dried at 600C. for 4 hours. The film was stored between polyethylene film layers for later testing.

Film flexibility was tested by bending a sample once slowly at one section of the sample and then once rapidly at another fresh section of the same sample.

Samples were rated for flexibility as follows: Flexible - no cracking at all after either slow or rapid flexion; Slightly brittle - no cracking after slow flexion, but minor stress/strain marks appeared after rapid flexion; Brittle - sample broke into two pieces during slow flexion.

Water solubility of each sample was tested by stirring 2 grams of 2-mil film into 25 ml of water at 250C. using a rotator mixer at 24 rpm. The time required to achieve complete solution was measured, with a sample rated insoluble if it did not dissolve in 24 hours. Test results are summarized in Table I.

Parts Parts Cross Plasticizer linking Agent per 100 per 100 parts Water Parts Poly- Polyacrylic Flexi- Solution Example Plasticizer acrylic Acid Cross-linking Agent Acid bility Time (Min.) 1 Glycerine 33 Propylene glycol di- 16 Flexible Insoluble glycidyl ether (epoxide equivalent wt. = 305-335 2 Glycerine 33 Glyceryl triglycidyl 16 Flexible Insoluble ether (epoxide equivalent wt. = 150-170) 3 Glycerine 33 Dicyandiamide 0.33 Flexible < 2 4 Glycerine 33 Dicyandiamide 5.3 Flexible Insoluble 5 Glycerine 33 Hexamethoxymethyl- 0.1 Flexible < 2 melamine 6 Glycerine 33 Hexamethoxymethyl- 1.3 Flexible < 5 melamine 7 Triethylene Glycol 25 hexamethoxymethyl- 10 Slightly Insoluble melamine brittle 8 Triethylene Glycol 43 Hexamethoxymethyl- 11.4 Flexible Insoluble melamine 9 Glycerine 33 Azetidinium chloride 13.3 Flexible Insoluble polymer 10 Glycerine 33 Azetidinium chloride 0.33 Flexible < 3 polymer 11 Glycerine 33 Azetidinium chloride 5.3 Flexible < 3 polymer 12 Glycerine 33 Polyvinyl pyrrolidone 0.5 Flexible > 20 (Mn=150,000) TABLE I cont'd.

Parts Parts Cross Plasticizer linking Agent per 100 per 100 parts Water parts Poly- polyacrylic Flexi- Solution Example Plasticizer acrylic acid Cross-linking Agent Acid bility Time(Min.) 13 Triethylene Glycol 25 Triethanolamine 10 Flexible < 3 14 Glycerine 43 Triethanolamine 14.2 Flexible < 7 15 Glycerine 33 Triethanolamine 13.3 Flexible < 10 16 Triethylene Glycol 25 Hydrogen peroxide 5 Flexible < 5 Examples 1-16 illustrate the utility of a diol and a triol as plasticizers.

Examples 1-16 also illustrate the utility of several epoxy resins, several polyamines, an alkanolamine and hydrogen peroxide as cross-linking agents.

Examples 7 and 8 demonstrate that slight embrittlement at a given level of a given cross-linking agent (Example 7) may be eliminated by increasing plasticizer amount (Example 8). The examples demonstrate a variety of water solubilities attainable with the novel compositions of this invention.

The compositions of this invention are tack-free and generally optically clear and have a combination of toughness, flexibility and variable water solubility.

These properties make the products useful for printing pastes, upholstery and carpet backings and other shaped articles, diaper liners, and films and coatings for foamed products such as polyurethane foam mattresses, garment finishing and the like.

WHAT WE CLAIM IS:1. A flexible polyacid composition comprising (1) 100 parts by weight of at least one polyacid containing polymerized therein at least 80% by weight of acrylic acid, methacrylic acid or a mixture thereof, and up to about 20% by weight of at least one other vinylidene monomer having at least one terminal CH2=C < group, said polyacid having a molecular weight from 50,000 to 2,000,000 and comaining an average from 1.0 to 1.7 free carboxyl acid groups per 100 molecular weight units; (2) from 15 to 100 parts by weight per 100 parts by weight polyacid of at least one polyol plasticizer and (3) from 0.25 part to 25 parts by weight per 100 parts by weight polyacid of a cross-linking agent setlected from epoxy resins, polyamines and

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

TABLE I cont'd.

Parts Parts Cross Plasticizer linking Agent per 100 per 100 parts Water parts Poly- polyacrylic Flexi- Solution Example Plasticizer acrylic acid Cross-linking Agent Acid bility Time(Min.) 13 Triethylene Glycol 25 Triethanolamine 10 Flexible < 3 14 Glycerine 43 Triethanolamine 14.2 Flexible < 7 15 Glycerine 33 Triethanolamine 13.3 Flexible < 10 16 Triethylene Glycol 25 Hydrogen peroxide 5 Flexible < 5 Examples 1-16 illustrate the utility of a diol and a triol as plasticizers.

Examples 1-16 also illustrate the utility of several epoxy resins, several polyamines, an alkanolamine and hydrogen peroxide as cross-linking agents.

Examples 7 and 8 demonstrate that slight embrittlement at a given level of a given cross-linking agent (Example 7) may be eliminated by increasing plasticizer amount (Example 8). The examples demonstrate a variety of water solubilities attainable with the novel compositions of this invention.

The compositions of this invention are tack-free and generally optically clear and have a combination of toughness, flexibility and variable water solubility.

These properties make the products useful for printing pastes, upholstery and carpet backings and other shaped articles, diaper liners, and films and coatings for foamed products such as polyurethane foam mattresses, garment finishing and the like.

WHAT WE CLAIM IS:1. A flexible polyacid composition comprising (1) 100 parts by weight of at least one polyacid containing polymerized therein at least 80% by weight of acrylic acid, methacrylic acid or a mixture thereof, and up to about 20% by weight of at least one other vinylidene monomer having at least one terminal CH2=C < group, said polyacid having a molecular weight from 50,000 to 2,000,000 and comaining an average from 1.0 to 1.7 free carboxyl acid groups per 100 molecular weight units; (2) from 15 to 100 parts by weight per 100 parts by weight polyacid of at least one polyol plasticizer and (3) from 0.25 part to 25 parts by weight per 100 parts by weight polyacid of a cross-linking agent setlected from epoxy resins, polyamines and

salts thereof, alkanolamines and hydrogen peroxide wherein at least 85% of the carboxylic acid groups of the polyacid remain free acid groups in the flexible polyacid composition.
2. A composition as claimed in claim I wherein said polyacid has a molecular weight from 100,000 to 1,000,000.
3. A composition as claimed in claim 1 or 2 wherein said vinylidene comonomer is selected from (A) vinyl aromatics having the formula:

wherein R1 is hydrogen, halogen or an alkyl radical containing from I to 4 carbon atoms; (B) vinyl nitriles having the formula

wberein R2 is hydrogen or an alkyl radical containing 1 to 3 carbon atoms; (C) amides of Ó,ss-olefinically unsaturated carboxylic acids containing 2 to 8 carbon atoms; and (D) acrylates having the formula

wherein R3 is hydrogen or an alkyl radical containing 1 to 3 carbon atoms and R4 is alkyl radical containing 1 to 18 carbon atoms or an alkoxyalkyl, alkylthioalkyl or cyanoalkyl radical containing 2 to 12 carbon atoms.
4. A composition as claimed in Claim 1 wherein said polyacid is polyacrylic acid.
5. A composition as claimed in any of claims I to 4 wherein the polyol is a diol or triol or a glycol ether having a molecular weight from 60 to 4000.
6. A composition as claimed in any one of claims 1 to 5 wherein said at least one plasticizer is selected from diols containing from 2 to 12 carbon atoms and up to two carbon-carbon double atoms, triols containing from 3 to 12 carbon atoms, said triols being fully saturated or containing a single carbon-carbon double bond, higher polyols containing from 4 to 12 carbon atoms and from 4 to 6 hydroxyl groups, said higher polyols being fully saturated or containing a single carboncarbon double bond.
7. A composition as claimed in claim 6 wherein said plasticizer is selected from saturated diols containing from 2 to 8 carbon atoms, saturated triols containing from 3 to 6 carbon atoms, saturated higher polyols containing from 4 to 8 carbon atoms and from 4 to 6 hydroxyl groups, and glycol ethers having a molecular weight from 90 to 4,000.
8. A composition as claimed in claim 7 wherein said plasticizer is glycerine.
9. A composition as claimed in any of one of clajims 1 to 7 wherein said plasticizer is triethylene glycol.
10. A composition as claimed in any one of claims 1 to 9 wherein said crosslinking agent is propylene glycol diglycidyl ether.
11. A composition as claimed any one of claims 1 to 9 wherein said crosslinking agent is glyceryl triglycidyl ether.
12. A composition as claimed in any one of claims 1 to 9 wherein said crosslinking agent is dicyandiamide.
13. A composition as claimed in any one of claims 1 to 9 wherein said crosslinking agent is hexamethoxymethylmelamine.
14. A composition as claimed in any one of claims 1 to 9 wherein said cross- linking agent is an azetidinium chloride polymer.
15. A composition as claimed in any one of claims 1 to 9 wherein said crosslinking agent is polyvinyl pyrrolidone having a molecular weight (Mn) from about 10,000 to 500,000.
16. A composition as claimed in any one of claims 1 to 9 wherein said crosslinking agent is triethanolamine.
17. A composition as claimed in any one of claims 1 to 9 wherein said crosslinking agent is hydrogen peroxide.
18. A composition as claimed in any one of claims 1 to 17 wherein said reaction mixture contains a polyacid solvent, non-solvent or mixture thereof.
19. A composition as claimed in claim 18 wherein said solvent is water.
20. A flexible polyacid composition as claimed in claim 1 substantially as hereinbefore described with reference to any one of the Examples.
21. A process for preparing a flexible polyacid composition as claimed in any one of claims 1 to 20 comprising (A) preparing a reaction mixture of components (1), (2) and (3) and (B) heating the reaction mixture to a temperature within the range from 200C. to 1500 C.
22. A process for preparing a flexible polyacid composition as claimed in claim 21 substantially as hereinbefore described with reference to any one of the Examples.
23. A flexible polyacid composition whenever prepared by a process as claimed in claim 21 or claim 22.