CA2052867A1

CA2052867A1 - Graft polymers on carboxyl-containing polyurethane graft bases, process for their preparation, and their use

Info

Publication number: CA2052867A1
Application number: CA 2052867
Authority: CA
Inventors: Matthias Kroggel
Original assignee: Individual
Current assignee: Hoechst AG
Priority date: 1990-10-17
Filing date: 1991-10-07
Publication date: 1992-04-18
Also published as: AU645613B2; JPH04272912A; AU8585891A; EP0481408A2; DE4032908A1; EP0481408A3

Abstract

Abstract of the disclosure:

Graft polymers on carboxyl-containing polyurethane graft bases, process for their preparation, and their use.

Carboxyl-containing graft polymers in which vinyl car-boxylates and, if desired, further ethylenically unsatur-ated monomers are grafted polymerically onto carboxyl-containing polyurethane graft bases by means of free radical-initiated graft polymerization, and hydrolysis products and salts of these carboxyl-containing graft polymers, can be obtained by grafting vinyl carboxylates having 3 to 20 carbon atoms and, if desired, further ethylenically unsaturated polymerizable and, where appropriate, copolymerizable monomers onto a carboxyl-containing polyurethane graft base containing at least two urethane groups in the molecule, in amounts of, preferably, from 10 to 95 % by weight, based on the carboxyl-containing graft polymer, by free radical-initiated graft polymerization, and subsequently, if desired, hydrolyzing all or some of the vinyl ester units and any other hydrolyzable monomer units in the grafted-on polymer radicals of the graft polymers using water and/or an alcohol, or converting the carboxyl groups into salts. Preferred vinyl esters to be grafted on are vinyl acetate and/or vinyl propionate and, if desired, vinyl versatate.

The graft polymerization is preferably carried out in solution or without a solvent.

Unhydrolyzed graft polymers are suitable, inter alia, as adhesives, in particular as hot-melt adhesives, and, in their water-soluble or water-dispersible salt forms, as dispersants. Fully or partially hydrolyzed graft polymers are suitable, inter alia, for the production of films.
Depending on the carboxyl group content of the polyur-ethane graft base, the degree of grafting, the degree of hydrolysis and the type of grafted monomers, the graft polymers have significantly improved solubilities in aqueous-alkaline media and reduced melting points com-pared with polyvinyl alcohol, so that they are advantage-ously suitable for the production of pressed and extruded films under mild temperature conditions without the additional use of organic plasticizers. Hydrolyzed graft polymers are furthermore suitable, inter alia, as adhesives, as dispersants in aqueous-alkaline media and as sizes and textile lubricants in textile processing.

Description

20~2867 Graft polymers on carboxyl-contai~ing polyurethane graft bases, process for their preparation, and their use.

The invention relates to graft polymers in which vinyl carboxylates and, if desired, further ethylenically unsaturated monomers are grafted polymerically onto carboxyl-containing polyurethane graft bases by free radical-initiated graft polymeri~ation, and to products of the hydrolysis of the graft polymers, in particular graft polyvinyl alcohols, to a process for their pre-paration, and to their use. The invention also relates,inter alia, to all the subject-matters disclosed and claimed in the patent claims.

As is known, polyvinylcarboxylic acid esters, in par-ticular polyvinyl acetates, and polyvinyl alcohols are used industrially in many ways. Similar possible uses of corresponding polyvinyl carboxylic acid esters and polyvinyl alcohols grafted onto polyurethane graft bases are known.

Thus, for example, polyvinyl acetates are used as ~dhesives, and polyvinyl alcohols, depending on the molecular weight, the degree of hydrolysis and any copolymerized comonomers, are used as adhesives, textile assistants or a raw material for films.

Depending on the area of application, polyvinyl alcohols, for example, frequently have unsatisfactory properties which significantly limit their range of applications and in some cases prevent them from being used at all. Thus, the water-solubility of polyvinyl alcohols is frequently too low, for example when used as sizes, and frequently too high when used as adhesives. A serious disadvantage of conventional polyvinyl alcohols is furthermore their 2 20~2867 low solubility in aqueous alkalis, such as, for example in aqueous sodium hydroxide solution. This disadvantage can be overcome, for example, by using copolymeric graft polyvinyl alcohols on polyurethane graft bases.

Graft polymers on polyurethane graft bases are known and can be prepared, for example, by free radical-initiated polymerization of ethylenically unsaturated monomers in the presence of polyurethanes which contain diisocyanate and diol monomer units and contain at least 2 urethane groups in the molecule. If the monomer employed in the free-radical polymerization is a vinyl ester, graft polyvinyl esters are obtained. EP-A 0, 308, 832 discloses that graft polyvinyl esters of this type can be converted into the corresponding graft polyvinyl alcohols by hydrolysis or transesterification. However, the water solubility, in particular in aqueous-alkaline media, of the graft polymers obtainable in this way is unsatis-factory in some cases. An improvement in the solubility can be achieved, for example, by copolymeric grafting of the polyurethanes with vinyl esters in combination with ethylenically unsaturated carboxylic acids or carboxylic acid derivatives and subsequent conversion into graft polyvinyl alcohols.

It is disadvantageous in this process that the conversion of the unsaturated carboxylic acids or carboxylic acid derivatives during the free-radical copolymerization is not quantitative, and residues of the monomers thus remain in the polymeric reaction product. Therefore, if the monomers are not eliminated from the reaction mixture during work-up, low-molecular-weight starting substances remain in the end product, which can have an adverse effect on the product quality of the graft polymer. If the residual monomers are to be removed by distillation, the monomeric unsaturated carboxylic acids or derivatives thereof can, in particular if the process is carried out on a large scale, accumulate in certain column trays and result, in particular in the case of free acids, in 20~2~67 considerable corrosion at these points.

When caxboxylic acid derivatives, such as, for example, unsaturated carboxylic acid esters, are used, the actual polymerization must be followed by hydrolysis or tran-sesterification in order to liberate the carboxylfunction. Hydrolysis or transesterification of copoly-merized vinyl ester units can also occur here, i.e.
carboxyl-containing polyvinyl esters cannot be obtained to a satisfactory extent by this route. Unfavorable copolymerization parameters andtor the regulating action of unsaturated carboxylic acids on the course of the polymerization also mean that the copolymerization of vinyl esters with unsaturated carboxylic acids or carboxylic acid derivatives is not possible without problems and usually requires special or complex processes.

~he invention thus had the object of obtaining carboxyl-containing graft polyvinyl esters whose preparation is possible without the abovementioned disadvantages and during which, in particular, no undesired or disadvantageous hydrolysis reactions take place at the copolymerized vinyl ester units and the resultant graft polymers have the required carboxyl group content and do not require any complex work-up measures.

It has now been found, surprisingly, that the dis-advantages mentioned can be avoided if the carboxyl groups, which are necessary for improved solubility of the polymers in aqueous-alkaline media, are not incorporated into the grafted-on side chains of the graft polymers by free radical-initiated copolymerization of carboxyl-carrying ethylenically unsaturated monomers, but instead by grafting ethylenically unsaturated carboxyl-free monomer units onto carboxyl-containing polyurethane graft bases, preferably carboxyl-containing polyether-urethane graft bases. If the carboxyl-free monomers used here are vinyl esters, the graft polyvinyl esters having 4 20~2867 the required carboxyl group con~ents are obtained without undesired hydrolysis or transesterification side reactions taking place at the vinyl ester monomer units.
These graft polyvinyl esters can subsequently be hydrolyzed or transesterified to give the corresponding graft polyvinyl alcohols.

The carboxyl-containing polyurethane graft bases should contain at least 2 urethane groups per molecule, where the number of urethane groups per graft base molecule has no particular maximum and can generally adopt values higher than 2. Carboxyl-containing polyurethanes have already been disclosed (c.f., for example US Patent 3,412,054, US Patent 4,408,008, and German Patent 3,641,494) and can be prepared, for example, by reacting diisocyanates with dimethylolcarboxylic acids or poly-methylolcarboxylic acids, preferably dimethylolcarboxylic acids, and if desired with further compounds containing more than one hydrogen which is active toward isocyanate groups. Preference is given to dimethylolcarboxylic acids of the formula I

I

R-C-COOH (I) n which R is (C1-C4)-alkyl or (C6-Cl2)-aryl, preferably (C1-C4)-alkyl, in particular methyl.
A particularly preferred compound of the formula I is 2,2-bis(hydroxymethyl)propionic acid.

The polyurethanes can be synthesized by conventional methods which are known from the literature. However, they are preferably prepared without solvents at temper-atures between 80 and 125C. In some cases, it may be advantageous to use catalysts, as are usually employed in the synthesis of polyurethanes. It is in principle possible here to use tertiary amines as the catalyst, but 20~2~67 it should be noted that the carboxylic acid groups of the dimethylol- or polymethylolcarboxylic acids form salts with the amines, and the amines can thus not become catalytically active. It is therefore necessary to use an excess of amine or to first convert the carboxylic acids into stable salt forms.

The isocyanates employed can be any aromatic, aliphatic or cycloaliphatic di- and of polyisocyanates, as are usually used for synthesis of polyurethanes, but pre-ferably diisocyanates, in particular, for example, 1,5-naphthalene diisocyanate, 4,4'-diphenylmethanedi~
methyl diisocyanate, di- and tetralkyldiphenylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene lS diisocyanate, and m- and p-diisocyanatoxylene. Particular preference is given to the use of aliphatic or cyclo-aliphatic diisocyanates having 2 to 12 carbon atoms in the aliphatic radicall preferably, for example, ethylene diisocyanate, propylene diisocyanate, butylene diisocyan-ate, 2,2,4-trimethylhexamethylene diisocyanate, 1,4-di-isocyanatocyclohexane, 4,4'-methylene-bis(cyclohexyl diisocyanate), 1-methyl-2,4-cyclohexyl diisocyanate, l-methyl-2,6-cyclohexyl diisocyanate, 1,3-bis(iso-cyanatomethyl)cyclohexane and 1,6-hexamethylene diisocyanate.

Particular preference is given to the use of isophorone diisocyanate.

The isocyanates mentioned can be employed individually or in combination or as mixtures.

Suitable components containing hydrogen which is active toward isocyanate groups are monofunctional and polyfunc-tional thiol compounds or, in particular, hydroxyl compounds, preferably alcoholic hydroxyl compounds.

The polyfunctional components containing hydroxyl groups 20~2~67 may be any aromatic, aliphatic or cycloaliphatic polyol which can usually be employed for the synthesis of polyurethanes. Preference is given to polyalkylene oxides of propylene and butylene, copolymers of ethylene oxide, propylene oxide and butylene oxide, preferably their block copolymers; particular preference is given to polyethylene oxides. Preference is given to the use of polyethylene oxides having weight average molecular weights of between 200 and 10,000 g/mol, particular pre-ference being given to polyethylene oxides having mole-cular weight of from 300 to 1,500 g/mol. Preference is furthermore given to cycloaliphatic diols, such as, for example, cyclohexanediols, and aliphatic diols having 2 to 12 carbon atoms, for example 1,3-propanediol, 1,2-lS propanediol, ethylene glycol, diethylene glycol, tri-ethylene glycol, hexylene glycol and others. Particular preference is given to use of diols containing primary OH
groups, such as, for example, 1,4-butanediol. In addition, low-molecular-weight polyfunctional thiols, but in particular dithiols, and polyfunctional hydroxy-mercaptans, in particular bifunctional hydroxymercaptans, such as, for example, 2-mercaptoethanol, can also be employed in the polyurethane synthesis.

The ratio between the number of groups containing hydrogen which is active toward NCO groups and the number of isocyanate groups present is 1 : 1, preferably between l : Q.99 and l : 0.5, but in particular between 1 : 0.98 and 1 : 0.7. If the components mentioned are employed in the stated stoichiometric ratios and if the reactive groups are allowed to react fully, isocyanate-free poly-urethanes are obtained. However, it is in principle also possible to obtain isocyanate-containing polyurethanes, which can likewise be employed in the graft reaction, through incomplete reaction of the reactants or by employing the isocyanate components in a stoichiometric excess. In this way, isocyanate-containing graft polymers are obtained which, due to the isocyanate groups present, can be employed, for example, for crosslinking reactions 7 2052~67 or can be converted further at the isocyanate groups using H-active compounds.

The molar ratio between the dimethylolcarboxylic acids preferably employed according to the invention and the remaining monomer units in the polyurethane graft bases is between 1 : X, where X > 30, and 1 : 1, preferably between 1 : 30 and 1 : 1.8, in particular between 1 : 5.4 and 1 : 2.7.

If chain extenders, such as, for example, low-molecular-weight diols or dithiols (for example 1,4-butanediols) are incorporated into the polymer structure together with polyalkylene glycols, the molar ratio between the chain extenders and the polyalkylene glycol should be between 1 : X, where X 2 8, and 1 : 1, preferably between 1 : 8 and 1 : 1.

The mean molecular weights of the polyurethanes can in principle be within a broad range, depending on the stoichiometry of the reactants employed, and are not crucial. The preparation processes may be limited by the viscosity levels above which further processing of the products can become difficult. For this reason, the molecular weights of the polyurethane graft bases are preferably between 3,000 and 50,000 g/mol, in particular between 5,000 and 30,000 g/mol. The mean molecular weights are computed in a conventional manner based on the stoichiometry.

In addition to polyfunctional hydroxyl components, aromatic, aliphatic or cycloaliphatic monohydroxyl compounds can also be employed in small amounts.
Preference is given here to those having from 1 to 12 carbon atoms, such as, for example, methanol, ethanol, propanol, butanol, cyclohexanol, hexanol, octanol, dodecanol and others, but it is also possible to use partially esterified or partially etherified polyols. In addition, monofunctional isocyanates, preferably those ~52~67 having 2 to 12 carbon atoms, such as, for example, ethyl isocyanate, propyl isocyanate, butyl isocyanate, pentyl isocyanate, hexyl isocyanate, phenyl isocyanate and monofunctional thiols, preferably those having 1 to 1~
carbon atoms, such as, for example, methyl mercaptan and ethyl mercaptan, can also be employed. The molecular weight of the polyurethane can be controlled via the amount of monofunctional compounds employed.

The grafting onto the polyurethane graft base is carried out using ethylenically unsaturated monomers which can be polymerized by means of free radicals, preferably vinyl carboxylic acid esters having 3 to 20 carbon atoms.
Particular preference is given to vinyl acetate and/or vinyl propionate. In addition, mixtures of vinyl-carboxylic acid esters, such as, for example, vinylacetate/vinyl versatate, or mixtures of vinylcarboxylic acid esters with further ethylenically unsaturated and preferably copolymerizable monomers, such as, for example, ethylene, styrene, acrylonitrile, vinyl chloride, vinylidene chloride, maleic acid diesters and/or fumaric acid diesters with (C1-C22)-alcohols, (meth)acrylic acid esters, crotonic acid esters and allyl esters, can be grafted.

The grafting is carried out by free radical-initiated polymerization of the ethylenically unsaturated monomers in the presence of or mixed with the polyurethane graft base using initiators which start free-radical chains, preference being given to free-radical use of formers which are soluble in the ethylenically unsaturated mono-mers or monomer mixtures or monomer solutions. Particularpreference is given to organic peroxides, organic percar-bonates and organic azo compounds. Azobisisobutyronitrile and tert.-butyl 2-ethylhexanoate are preferably employed, and dibenzoyl peroxide is particularly preferred. The grafting reaction is carried out with addition of, preferably from 0.013 to 1.3 mol-%, in particular from 0.026 to 0.27 mol-%, of initiator, based on the total 20~2867 g amount of monomer.

Graft polymers which contain hydrolyzable monomer units can be converted into partially or fully hydrolyzed products by hydrolysis, alcoholysis of transesterific-ation, the degree of hydrolysis being at least 1 mol-%, but preferably from 50 to 99 mol-%, based on the total number of moles of all hydrolyzable monomer units in the graft polymer.

The grafting reaction can be carried out, for example, in emulsion or in suspension. However, it is preferably carried out in solution and particularly preferably in the absence of solvent.

The monomers to be grafted are preferably metered con-tinuously or in portions into the graft base in the reaction vessel; it is advantageous to choose the meter-ing rate and process parameters in such a manner that the formation of homopolymers is substantially or virtually completely avoided and the monomers start on these polymer chains with free radical-initiated addition onto the graft base. The monomers, if they are in liquid form, can be added with or without solvents. The initiator is preferably dissolved in the monomer liquid or monomer solution and metered in together with this. However, it can also be initially introduced, at least in part, into the reaction vessel together with a graft base. The grafting reaction is preferably carried out at temper-atures between 65 and 125C, in particular between 65 and 100C, depending on the catalyst employed and, in par-ticular in the case of solvent-free polymerization, depending on the polyurethane graft base employed and on its viscosity.

Alternatively, batch polymerization is also possible, but this process is more likely to result in mixtures of grant polymers and homopolymers or copolymers of the monomers employed.

2052~6'~

The increase in viscosity of the reaction mixture which occurs during the graft polymerization, in particular in the case of solvent-free polymerization, frequently results in processing problems, which can generally be circumvented, for example, by continuous or batchwise addition of solvents. Suitable solvents are preferably monofunctional alcohols, such as, for example, methanol, ethanol, propanol, isopropanol or butanol. However, it may also be advantageous to employ other organic sol-vents, such as, for example, aliphatic and aromatichydrocarbons, tetrahydrofuran, dioxane, ethyl acetate and acetone.

In the case of solution graft polymerization, the solvent content in the reaction mixture should be less than 20 %
by weight, preferably less than 10 ~ by weight, based on the total amount of reaction mixture.

After removal of residual monomers, preferably by azeo-tropic distillation with methanol, the graft polymers according to the invention can be precipitated by introducing the reaction mixture into water, and separ-ated off. Alternatively, the solvent can be removed by distillation and the graft polymer isolated from the distillation residue.

After dissolution in a solvent, preferably a low-molecular-weight alcohol, for example methanol, ethanol or isopropanol, graft polymers having hydrolyzable structures can be converted into partially or fully hydrolyzed products, in particular graft polyvinyl alcohols, by conventional methods which are known from the literature, by means of acidic catalysts (for example hydrochloric acid, phosphoric acid, sulfuric acid, nitric acid or p-toluolenesulfonic acid), but preferably using alkaline catalysts (for example NaOH, KOH, NaOCH3, ROCH3, or primary, secondary or tertiary amines), if desired with additional use of water.

205~7 If alkali metal hydroxides are used as the hydrolysis catalyst, the amount of alkali metal hydroxide added is preferably from 0.1 to 20 mol-%, in particular from 0.5 to 10 mol-~, based on the total number of moles of grafted-on, hydrolyzable monomer units. It should be noted in this procedure that, if alkaline catalysts are used, the carboxyl groups present in the polymer must first be neutralized using bases before the hydrolysis or transesterification reaction. The hydrolysis or trans-esterification is preferably carried out at temperaturesbetween 20 and 60C.

The unhydrolyzed graft polymers obtained according to the invention are suitable for use as adhesives, their use as hot-melt adhesives, if desired with additional use of crosslinking components, being of particular interest. By varying the molecular weight and composition of the poly-urethane graft base, the degree of grafting and the type of grafted-on monomers, products having greatly different melting points can be obtained. ~eutralization of the carboxyl groups and conversion thereof into salts, preferably alkali metal, ammonium or amine salts, allows graft polymers which are water-dispersible, water-soluble to form colloids or alkali-soluble to be obtained. They are preferably suitable as dispersants in aqueous media.
Salts with polyvalent metals are not very water-soluble and can be used in paint and coating resins. The adhesion of the graft polymers to a wide variety of materials is likewise affected by the type of polyurethane graft base, the degree of grafting and the type of grafted-on monomers. Coatings and films can easily be dissolved by means of aqueous alkalis and removed again.

Fully and partially hydrolyzed graft polymers according to the invention are particularly suitable for the pro-duction of films. The products have the advantage over non-modified polyvinyl alcohols of having significantly reduced melting points, depending on the polyurethane graft base, the degree of grafting, the degree of 2as2~5~7 hydrolysis and depending on the type of grafted monomers, so that pressed and extruded films can be produced under mild temperature conditions. Furthermore, films having different alkali solubility, water solubility, tear strength, extensibility and gas barrier properties, for example to oxygen, can be obtained depending on the relevant parameters.

Due to their high adhesion to metals, the products can advantageously be employed as hot-melt adhesives, prefer-ably with crosslinking components, for the bonding ofmetals or alternatively for the coating of metals.
Uncrosslinked coatings can easily be dissolved again and removed by treatment with aqueous alkalis. Films comprising water-soluble salts of graft polymers, in particular of graft polyvinyl alcohols, can particularly advantageously be used as water-soluble packaging components 88 for chemicals, detergents, pesticides, etc.
The use of the graft polyvinyl alcohols as dispersants in aqueous media, as sizes or as textile lubricants can result in surprisingly advantageous results during textile processing due to the ready alkali-solubility of the products.

The invention is described in greater detail by means of the examples below.

The intrinsic viscosity [q] is determined in all the examples using an Ostwald Viscometer. The concentrations of the measured solutions are selected in such a manner that there is no need to carry out a ~Hagenbach correction~'.

The molecular weights M are weight average molecular weights calculated from the stoichiometry of the components.

The degrees of hydrolysis are determined by methods known from the literature, the polymers being fully hydrolysed 20~28~7 using alkali metal hydroxide solution.

The polymer-bonded carboxyl groups are determined by charge titration in aqueous polymer solutions by the SCD
method using a Mytek PCD 02 instrument.

Example 1 Preparation of a carboxyl-containing polyurethane graft base 2,147.7 g of polyethylene glycol (M = 630), 61.43 g of 1,4-butanediol and 365.82 g of 2,2-bis(hydroxymethyl)-propionic acid are introduced under a nitrogen atmosphere into a reaction vessel with stirrer, and warmed to a temperature of 115C. 1,364.03 g of isophorone diisocyan-ate are subsequently added dropwise over the course of 5 hours at such a rate that the temperature of the reaction mixture does not exceed 130C. In order to complete the reaction, the reaction mixture is stirred at 120 for a further hour.

The completeness of the conversion and thùs the end of the xeaction is determined by analysis of the diisocyan-ate consumption by conventional methods ~IR spectro-scopic, titration).

The polymer obtained has a calculated molecular weight M
of 5,777 g/mol and contains on average 4 mol of carboxyl groups per mole of polyurethane graft base. The intrinsic viscosity [~] is 12.8 ml/g, determined at 25C in meth-anol solution in an Ostwald viscometer.

Example 2 Preparation of a carboxyl-containing polyurethane graft base Reaction procedure as in example 1. 4,413.2 g of poly-ethylene glycol (M = 630), 90.15 g of 1,4-butanediol, 268.2 g of 2,2-bis~hydroxymethyl)propionic acid and 2,000.63 g of isophorone diisocyanate are reacted.

The resultant polymer has a calculated molecular weight M of 6,769 g/mol and contains on average 2 mol of carboxyl groups per mole of polyurethane graft base. The intrinsic viscosity [~] is 12.9 ml/g, determined at 25C
in methanol solution in an Ostwald viscometer.

Example 3 Preparation of a carboxyl-containing polyurethane graft base Reaction procedure as in example 1. 2,100 g of poly-ethylene glycol (M = 630), 60.08 g of 1,4~butanediol, 357.69 g of 2,2-bis(hydroxymethyl)propionic acid and 1,407.83 g of isophorone diisocyanate are reacted.

The resultant polymer has a calculated molecular weight M of 11,777 g/mol and contains on average 8 mol of car~oxyl groups per mole of polyurethane graft base. The intrinsic viscosity [~] is 16.6 ml/g, determined at 25C
in methanol solution in an Ostwald viscometer.

Example 4 Preparation of a carboxyl-containing polyurethane graft base Reaction procedure as in example 1. 2,362.5 g of poly-ethylene glycol (M = 630), 67.59 g of 1,4-butanediol, 402.04 g of 2,2-bis(hydroxymethyl)propionic acid and 1,611.6 g of isophorone diisocyanate are reacted.

The resultant polymer has a calculated molecular weight M of 17,776 g/mol and contains on average 12 mol of carboxyl groups per mole of polyurethane graft base. The intrinsic viscosity [~] is 18.8 ml/g, determined at 25C
in methanol solution in an Ostwald viscometer.

Example 5 Preparation of a graft polyvinyl acetate on a carboxyl-containing polyurethane graft base 350 g of polyurethane graft base from example 1 are introduced into a stirred vessel and warmed to a - 15 - 2 ~ 5 2 g ~ ~
temperature of 85C. A solution of 0.66 g of 75 %
strength by weight dibenzoyl peroxide in 52.5 g of vinyl acetate is subsequently added. When the reaction has commenced, which can be seen from an increase in the internal temperature, a solution of 5.91 g of 75 %
strength by weight dibenzoyl peroxide in 472.5 g of vinyl acetate is added dropwise over the course of 5 hours.
This is followed by a post-reaction phase of 1 hour at a temperature of 98C. The reaction mixture is subsequently diluted with methanol, and unreacted monomer is removed by azeotropic distillation with methanol. The residual monomer content is determined by methods known from the literature. In order to isolate the reaction product, ~he reaction mixture is precipitated in water, and the graft polymer obtained is dried at 50C in vacuo.
Alternatively, the graft polyvinyl acetate can also be obtained by removing all the methanol from the reaction mixture by distillation.

Yield: 92.5 % by weight, based on the vinyl acetate employed.
M (calculated) : 13,794 g/mol Composition of the graft polyvinyl acetate obtained (calculated):
58.12 % by weight of vinyl acetate units 3.89 % by weight of 2,2-bis(hydroxy-methyl)propionic acid units 37.99 ~ by weight of polyurethane graft base [~] = 18.9 ml/g, measured in tetrahydrofuran at 25C.

Example 6 Preparation of a graft polyvinyl acetate on a carbo yl-containing polyurethane graft base 250 g of polyurethane graft base from example 1 are introduced into a stirred vessel and warmed to a temper-ature of 85C. A solution of 0.94 g of 75 % strength by weight dibenzoyl peroxide in 75 g of vinyl acetate is subsequently added. When the reaction has commenced, 2n52~67 which can be seen from an increase in the internal tem-perature, a solution of 8.44 g of 75 % strength by weight dibenzoyl peroxide in 675 g of vinyl acetate is added dropwise over the course of 5 hours. This is followed by a post-reaction phase of 1 hour at a temperature of 98C.
The reaction mixture is subse~uently diluted with methanol, and unreacted monomer is removed by azeotropic distillation with methanol. The residual monomer content is determined by methods known from the literature. In order to isolate the reaction product, the reaction mixture is precipitated in water, and the graft polymer obtained is dried at 50C in vacuo. Alternatively, the graft polyvinyl acetate can be obtained by removing all the methanol from the reaction mixture by distillation.

Yield: 95.3 ~ by weight, based on the vinyl acetate employed.
M (calculated) : 22,238 g/mol Composition of the graft polyvinyl acetate obtained (calculated):
74.08 % by weight of vinyl acetate units 2.41 % by weight of 2,2-bis(hydroxy-methyl)propionic acid units 23.51 ~ by weight of polyurethane graft base [~] = 25.2 ml~g, measured in tetrahydrofuran at 25C.

Example 7 Preparation of a graft polyvinyl acetate on a carboxyl-containing polyurethane graft base 350 g of polyurethane graft base from example 2 are introduced into a stirred vessel and warmed to a temper-ature of 85C. A solution of 0.66 g of 75 % s~rength by weight dibenzoyl peroxide in 52.5 g of vinyl acetate is subsequently added. When the reaction has commenced, which can be seen from an increase in the internal tem-perature, a solution of 5.9 g of 75 % streng~h by weightdibenzoyl peroxide in 472.5 g of vinyl acetate is added dropwise over the course of 5 hours. This is followed by 20~2~3~7 a post-reaction phase of 1 hour at a temperature of 98C.
Th~ reaction mixture is subsequently diluted with methanol, and unreacted monomer is removed by azeotropic distillation with methanol. The residual monomer content is determined by methods known from the literature. In order to isolate the reaction product, the reaction mixture is precipitated in water, and the graft polymer obtained is dried at 50C in vacuo. Alternatively, the graft polyvinyl acetate can be obtained by removing all the methanol from the reaction mixture by distillation.

Yield: 91.4 % by weight, based on the vinyl acetate employed.
M (calculated) : 16,051 g/mol Composition of the graft polyvinyl acetate obtained 15 (calculated~:
57.83 % by weight of vinyl acetate units 1.67 % by weight of 2,2-bis(hydroxy-methyl)propionic acid units 40.50 ~ by weight of polyurethane graft base [~] = 17.2 ml/g, measured in tetrahydrofuran at 25C.

Example 8 Preparation of a graft polyvinyl acetate on a carboxyl-containing polyurethane graft base 300 g of polyurethane graft base from example 2 are introduced into a stirred vessel and warmed to a temper-ature of 85C. A solution of 0.87 g of 75 % strength by weight dibenzoyl peroxide in 69.6 g of vinyl acetate is subsequently added. When the reaction has commenced, which can be seen from an increase in the internal tem-perature, a solution of 7.83 g of 75 % strength by weight dibenzoyl peroxide in 626.4 g of vinyl acetate is added dropwise over the course of 5 hours. This is followed by a post-reaction phase of 1 hour at a temperature of 98C.
The reaction mixture is subsequently diluted with methanol, and unreacted monomer is removed by azeotropic distillation with methanol. The residual monomer content 2~528~7 is determined by methods known from the literature. In order to isolate the reaction product, the reaction mixture iæ precipitated in water, and the graft polymer obtained is dried at 50C in vacuo. Alternatively, the graft polyvinyl acetate can be obtained by removing all the methanol from the reaction mixture by distillation.

Yield: 92.7 % by weight, based on the vinyl acetate employed.
M (calculated) : 21,325 g/mol Composition of the graft polyvinyl acetate obtained (calculated):
68.26 % by weight of vinyl acetate units 1.26 % by weight of 2,2-bis(hydroxy-methyl)propionic acid units 30.48 % by weight of polyurethane graft base [~3 = 19.1 mltg, measured in tetrahydrofuran at 25C.

Example 9 Preparation of a graft polyvinyl acetate on a carboxyl-containing polyurethane graft base 1,736 g of polyurethane graft base from example 3 areintroduced into a stirred vessel and warmed to a temper-ature of 85C. A solution of 3.3 g of 75 % strength by weight dibenzoyl peroxide in 264.5 g of vinyl acetate is subsequently added. When the reaction has commenced, which can be seen from an increase in the internal tem-perature, a solution of 29.75 g of 75 % strength by weight dibenzoyl peroxide in 2,380.5 g of vinyl acetate is added dropwise over the course of 5 hours. This is followed by a post-reaction phase of l hour at a temper-ature of 100C. The reaction mixture is subsequently diluted with methanol, and unreacted monomer is removed by azeotropic distillation with methanol. The residual monomer content is determined by methods known from the literature. In order to isolate the reaction product, the reaction mixture is precipitated in water, and the graft polymer obtained is dried at 50C in vacuo. Alternatively, 2~286 7 the graft polyvinyl acetate can be obtained by removing all the methanol from the reaction mixture by distillation.

Yield: 92.3 % by weight, based on the vinyl acetate employed.
M (calculated) : 28,077 g/mol Composition of the graft polyvinyl acetate obtained (calculated):
58.06 % by weight of vinyl acetate units 3.82 ~ by weight of 2,2-bis(hydroxy-methyl)propionic acid units 38.12 % by weight of polyurethane graft base [~ = 24.4 ml/g, measured in tetrahydrofuran at 2~C.

Example 10 Preparation of a graft polyvinyl acetate on a carboxyl-containi~g polyurethane graft base 1,698 g of polyurethane graft base from example 4 are introduced into a stirred vessel and warmed to a temper-ature of 85C. A solution of 3.18 g of 75 % strength by weight dibenzoyl peroxide in 254.7 g of vinyl acetate is subsequently added. When the reaction has commenced, which can be seen from an increase in the internal temperature, a solution of 28.66 g of 75 % strength by weight dibenzoyl peroxide in 2,292.3 g of vinyl acetate is added dropwise over the course of 5 hours. This is followed by a post-reaction phase of 1 hour at a temperature of 100C. The reaction mixture is subsequently diluted with methanol, and unreacted monomer is removed by azeotropic distillation with methanol. The residual monomer content is determined by methods known from the literature. In order to isolate the reaction product, the reaction mixture is precipitated in water, and the graft polymer obtained is dried at 50C in vacuo.
Alternatively, the graft polyvinyl acetate can be obtained by removing all the methanol from the reaction mixture by distillation.

2052~7 Yield: 93.2 % by weight, based on the vinyl acetate employed.
M (calculated) : 42,614 g/mol Composition of the graft polyvinyl acetate obtained (calculated):
58.3 % by weight of vinyl acetate units 3~8 % by weight of 2,2-bis(hydroxy-methyl)propionic acid units 37.9 % by weight of polyurethane graft base [~] = 29.6 ml/g, measured in tetrahydrofuran at 25C.

Example 11 Preparation of a graft polyvinyl alcohol on a carboxyl-containing polyurethane graft base 796.43 g of the graft polyvinyl acetate from example 5 are dissolved in 796.43 g of methanol, and 133.74 g of a 10 % strength by weight methanolic NaOH solution are added at 22C with stirring. After about 20 minutes, a gel forms, which is mechanically comminuted. After 2 hours, 20 ml of water are added to the resultant gel granules with stirring, and the resultant polymer granules are dried at 50C in vacuo.

The graft polyvinyl alcohol obtained has a degree of hydrolysis of 99.3 mol-%, based on the vinyl acetate unit content in the initial graft poly~inyl acetate.
M (in the COOH form, calculated): 10,442 g/mol Composition of the graft polyvinyl alcohol obtained (calculated):
39.00 % by weight of vinyl alcohol units 55.32 % by weight of polyurethane graft base 5.14 % by weight of 2,2-bis(hydroxymethyl)-propionic acid units Result of charge titration (SCD method): 263 ~mol of COOH/g Dissoiution rate of a 200 ~m thick cast film of the resultant graft polyvinyl alcohol in 10 % strength by 2052~7 weight aqueous sodium hydroxide solution at 60C: 5.5 minutes.

Example 12 Preparation of a graft polyvinyl alcohol on a carboxyl-containing polyurethane graft base 892.76 g of the graft polyvinyl acetate from example 6 are dissolved in 892.76 g of methanol, and 123.01 g of a 10 % strength by weight methanolic NaOH solution are added at 22C with stirring. After about 15 minutes, a gel forms, which is mechanically comminuted. After 2 hours, 20 ml of water are added to the resultant gel granules with stirring, and the resultant polymer granules are dried at 50C in vacuo.

The graft polyvinyl alcohol obtained has a degree of hydrolysis of 98.9 mol-%, based on the vinyl acetate unit content in the initial graft polyvinyl acetate.
M (in the COOH form, calculated): 14,852 g/mol Composition of the graft polyvinyl alcohol obtained (calculated).
56.27 ~ by weight of vinyl alcohol units 38.90 % by weight of polyurethane graft base 3.61 % by weight of 2,2-bis(hydroxymethyl)-propionic acid units Result of charge titration (SCD method): 175 ~mol of COOH/g Dissolution rate of a 200 ~m thick cast film of the resultant graft polyvinyl alcohol in 10 % strength by weight aqueous sodium hydroxide solution at 60C: 6 minutes.

Example 13 Preparation of a graft polyvinyl alcohol on a carboxyl-containing polyurethane graft base 744.98 g of the graft polyvinyl acetate from example 7 are dissolved in 744.98 g of methanol, and 75.74 g of a 10 % strength by weight methanolic NaOH solution are 2~2~67 added at 22C with stirring. After about 25 minutes, a gel forms, which is mechanically comminuted. After 2 hours, 20 ml of water are added to the resultant gel granules with stirring, and the resultant polymer granules are dried at 50C in vacuo.

The graft polyvinyl alcohol obtained has a degree of hydrolysis of 99.2 mol-%, based on the vinyl acetate unit content in the initial graft polyvinyl acetate.
M (in the COOH form, calcula~ed): 11,823 g/mol Composition of the graft polyvinyl alcohol obtained (calculated):
39.85 % by weight of vinyl alcohol units 57.26 % by weight of polyurethane graft base 2.27 % by weight of 2,2-bis(hydroxymethyl)-propionic acid units Result of charge titration (SCD method): 100 ~mol of COOH/g Dissolution rate of a 200 ~m thick cast film of the resultant graft polyvinyl alcohol in 10 % strength by weight aqueous sodium hydroxide solution at 60C: 6 minutes.

Example 14 Preparation of a graft polyvinyl alcohol on a carboxyl-containing polyurethane graft base 890.26 g of the graft polyvinyl acetate from example 8 are dissolved in 890.26 g of methanol, and 87.77 g of a l0 % strength by weight methanolic NaOH solution are added at 22C with stirring. After about 20 minutes, a gel forms, which is mechanically comminuted. After 2 hours, 20 ml of water are added to the resultant gel granules with stirring, and the resultant polymer granules are dried at 50C in vacuo.

The graft polyvinyl alcohol obtained has a degree of hydrolysis of g9.3 mol-%, based on the vinyl acetate unit content in the initial graft 2n~2~67 polyvinyl acetate.
M (in the COOH form, calculated): 14,537 g/mol Composition of the graft polyvinyl alcohol obtained (calculated):
50.89 % by weight of vinyl alcohol units 41.57 % by weight of polyurethane graft base 1.85 % by weight of 2,2-bis(hydroxymethyl)-propionic acid units Result of charge titration (SCD method): 80 ~mol of COOH/g Dissolution rate of a 200 ~m thick cast film of the resultant graft polyvinyl alcohol in 10 % strength by weight aqueous sodium hydroxide solution at 60C: 4.5 minutes.

Example 15 Preparation of a graft polyvinyl alcohol on a carboxyl-containing polyurethane graft base 100 g of the graft polyvinyl acetate from example 9 are dissolved in 100 g of methanol, and 16.6 g of a 10 %
strength by weight methanolic NaOH solution are added at 40C with stirring. After about 20 minutes, a gel forms, which is mechanically comminuted. The gel granules obtained are washed with methanol and dried at 50C in vacuo.

The graft polyvinyl alcohol obtained has a degree of hydrolysis of 84.5 mol-%, based on the vinyl acetate unit content in the initial graft polyvinyl acetate.
M (in the COOH form, calculated): 22,427 g/mol Composition of the graft polyvinyl alcohol obtained tcalculated):
31.4 ~ by weight of vinyl alcohol units 52.5 % by weight of polyurethane graft base 4.8 ~ by weight of 2,2-bis(hydroxymethyl)-propionic acid units 11.3 % by weight of vinyl acetate units Result of charge titration (SCD method): 313 ~mol of 20~2~61~

COOH/g Dissolution rate of a 200 ~m thick cast film of the resultant graft polyvînyl alcohol in 10 % strength by weight aqueous sodium hydroxide solution at 60C: 4.5 minutes.

Exam~le 16 Preparation of a graft polyvinyl alcohol on a carboxyl-containing polyurethane graft base 100 g of the graft polyvinyl acetate from example 10 are dissolved in 100 g of methanol, and 16.6 g of a 10 %
strength by weight methanolic NaOH solution which has been mixed with 4.15 g of water are added at 40C with stirring. After about 20 minutes, a gel forms, which is mechanically comminuted. The gel granules obtained are washed with methanol and dried at 50C in vacuo.

The graft polyvinyl alcohol obtained has a degree of hydrolysis of 91.8 mol-%, based on the virlyl acetate unit content in the initial graft polyvinyl acetate.
M (in the COOH form, calculated): 33,090 g/mol Composition of the graft polyvinyl alcohol obtained (calculated):
35.3 ~ by weight of vinyl alcohol units 53.7 % by weight of polyurethane graft base 4.9 % by weight of 2,2-bis(hydroxymethyl)-propionic acid units 6.1 % by weight of vinyl acetate units Result of charge titration (SCD method): 345 ~mol of COOH/g Dissolution rate of a 200 ~m thick cast film of the resultant graft polyvinyl alcohol in 10 % strength by weight aqueous sodium h~droxide solution at 60C: 3 minutes.

Comparative ExamPle 1 Preparation of a carboxyl-free polyurethane graft base 6,000 g of polyethylene glycol (M = 600), 386.2 g of l,4-2052~,~7 butanediol and 3 ml of N,N-dimethylpiperazine are intro-duced into a reaction vessel with stirrer, and heated to a temperature of 75C. 2,856.4 g of isophorone diisocyan-ate are subsequently added dropwise over the course of 5 hours at such a rate that the temperature of the reaction mixture does not exceed 100C. In order to complete the reaction, the reaction mixture is stirred at 80C for a further hour.

The completeness of the conversion and thus the end of the reaction is determined by analysis of the diisocyan-ate consumption by conventional methods (IR spectroscopy, titration).

The polymer obtained has a calculated molecular weight M
of 6,471 g/mol. The intrinsic velocity [q] is 11.8 ml/g, determined at 25C in methanol solution in an Ostwald viscometer.

Comparative ExamPle 2 Preparation of a carboxyl-free polyurethane graft base Reaction procedure as in Comparative Example 1. 3,000 g of polyethylene glycol (M = 600), 193.1 g of 1,4-butanediol, 1.5 mlofN,N-dimethylpiperazine and 1,534.9 g of isophorone diisocyanate are reacted.

The resultant polymer has a calculated molecular weight M of 19,858 g/mol. The intrinsic velocity [~] is 16.9 ml/g, determined at 25C in methanol solution in an Ostwald viscometer.

Comparative Example 3 Preparation of a graft polyvinyl acetate on a carboxyl-iree polyurethane graft base 2,847 g of polyurethane graft base from Comparative Example 1 are introduced into a stirred vessel and warmed to a temperature of 85C. A solution of 4.95 g of 75 %
strength by weight dibenzoyl peroxide in 660.5 g of vinyl acetate are subsequently added. When the reaction has 2~2~67 commenced, which can be seen from an increase in the internal temperature, a solution of 44.58 g of 75 ~
strength by weight dibenzoyl peroxide in 5,944.5 g of vinyl acetate is added dropwise over the course of 5 hours. This is followed by a post-reaction phase of 1 hour at a temperature of 98C. The reaction mixture is subsequently diluted with methanol, and unreacted monomer is removed by azeotropic distillation with methanol. The residual monomer content is determined by methods known from the literature. In order to isolate the reaction product, the reaction mixture is precipitated in water, and the graft polymer obtained is dried at 50C in vacuo.
Alternatively, graft polyvinyl acetate can also be obtained by removing all of the me~hanol from the reaction mixture by distillation.

Yield: 95.0 % by weight, based on the vinyl acetate employed M (calculated3: 20,727 g/mol Composition of the graft polyvinyl acetate obtained (calculated):
68.8 % by weight of vinyl acetate units 31.2 % by weight of polyurethane graft base Comparative ExamPle 4 Preparation of a graft polyvinyl acetate on a carboxyl-free polyurethane graft base 3,000 g of polyurethane graft base from Comparative Example 1 are introduced into a stirred vessel and warmed to a temperature of 85C~ A solution of 3.38 g of 75 %
strength by weight dibenzoyl peroxide in 450 g of vinyl acetate are subsequently added. When the reaction has commenced, which can be seen from an increase in the internal temperature, a solution of 30.38 g of 75 %
strength by weight dibenzoyl peroxide in 4,050 g of vinyl acetate is added dropwise over the course of 5 hours.
This is followed by a post-reaction phase of 1 hour at a temperature of 98C. The reaction mixture is subsequently diluted with methanol, and unreacted monomer is removed 2 ~ 5 2 ~ ~ r~
_ 27 -by azeotropic distillation with methanol. The residual monomer content is determined by methods known from the literature. In order to isolate the reaction product, the reaction mixture is precipitated in water, and the graft polymer obtained is dried at 50C in vacuo. Alternative-ly, graft polyvinyl acetate can also be obtained by removing all of the methanol from the reaction mixture by distillation.

Yield: 96.7 % by weight, based on the vinyl acetate employed M (calculated): 15,859 g/mol Composition of the graft polyvinyl acetate obtained (calculated):
59.2 % by weight of vinyl acetate units 40.8 ~ by weight of polyurethane graft base ComParative Example 5 Preparation of a graft polyvinyl acetate on a carboxyl-free polyurethane gra~t base 450 g of polyurethane graft base from Comparative Example 1 are introduced into a stirred vessel and warmed to a temperature of 85C. A solution of 0.57 g of 75 %
strength by weight dibenzoyl peroxide in 76.5 g of vinyl acetate are subsequently added. When the reaction has commenced, which can be seen from an increase in the internal temperature, a solution of 5.16 g of 75 ~
strength by weight dibenzoyl peroxide in 688.5 g of vinyl acetate is added dropwise over the course of 5 hours.
This is followed by a post-reaction phase of 1 hour at a temperature of 98C. The reaction mixture is subsequently diluted with methanol, and unreacted monomer is removed by azeotropic distillation with methanol. The residual monomer content is determined by methods known from the literature. In order to isolate the reaction product, the reaction mixture is precipitated in water, and the graft polymer obtained is dried at 50C in vacuo. Alternative-ly, graft polyvinyl acetate can also be obtained by removing all of the methanol from the reaction mixture by - 28 - 2~2~6 ~
distillation.

Yield: 96.8 % by weight, based on the vinyl acetate employed M (calculated): 17,119 g/mol Composition of the graft polyvinyl acetate obtained (calculated):
59.2 % by weight of vinyl acetate units 40.8 ~ by weight of polyurethane graft base Comparative Example 6 Preparation of a graft polyvinyl acetate on a carboxyl-free polyurethar.e graft base 1,500 g of polyurethane graft base from comparative ex-ample 2 are introduced into a stirred vessel and warmed to a temperature of 85C. A solution of 2.61 g of 75 %
strength by weight dibenzoyl peroxide in 348 g of vinyl acetate are subsequently added. When the reaction has commenced, which can be seen from an increase in the internal temperature, a solution of 23.49 g of 75 %
strength by weight dibenzoyl peroxide in 3,132 g of vinyl acetate is added dropwise over the course of 5 hours.
This is followed by a post-reaction phase of 1 hour at a temperature of 98C. The reaction mixture is subsequently diluted with methanol, and unreacted monomer is rempved by azeotropic distillation with methanol. The residual monomer content is determined by methods known from the literature. In order to isolate the reaction product, the reaction mixture is precipitated in water, and the graft polymer obtained is dried at 50C in vacuo.
Alternatively, graft polyvinyl acetate can also be obtained by removing all of the methanol from the reaction mixture by distillation.

Yield: 92.7 ~ by weight, based on the vinyl acetate employed M (calculated): 62,574 g/mol Composition of the graft polyvinyl acetate obtained (calculated):

2~2g~7 68.3 % by weight of vinyl acetate units 31.7 % by weight of polyurethane graft base Comparative ExamPle 7 Preparation of a graft polyvinyl alcohol on a carboxyl-free polyurethane graft base 865.8 g of the graft polyvinyl acetate from ComparativeExample 3 are dissolved in 865.8 g of methanol, and 32.49 g of a 10 % strength by weight methanolic NaOH
solution which has been mixed with 32.49 g of water is added at 22C with stirring. After about 50 minutes, a gel forms, which is mechanically comminuted. The gel granules obtained are washed with methanol and dried at 50C in vacuo.

The graft polyvinyl alcohol obtained has a degree of hydrolysis of 85.5 mol-%, based on the vinyl acetate unit content in the starting graft polyvinyl acetate.
M (calculated) : 14,776 g/mol Composition of the graft polyvinyl alcohol obtained (calculated):
42.2 % by weight of vinyl alcohol units 43.8 % by weight of polyurethane graft base 14.0 % by weight of vinyl acetate units Result of charge titration (SCD method): < 10 ~mol of COOH/g Dissolution rate of a 200 ~m thick cast film of the graft polyvinyl alcohol in 10% strength by weight aqueous sodium hydroxide solution at 60C: 8 minutes.

Comparative Example 8 Preparation of a graft polyvinyl alcohol on a carboxyl-free polyurethane graft base 100 g of the graft polyvinyl acetate from Comparative Example 4 are dissolved in 100 g of methanol, and 6.84 g of a 10 % strength by weight methanolic NaOH solution are added with stirring. After about 16 minutes, a gel forms, 2 ~ 6 '7 which is mechanically comminuted. The gel granules obtained are washed with methanol and dried at 50C in vacuo.

The graft polyvinyl alcohol obtained has a degree of hydrolysis of 95 mol-%, based on the vinyl acetate unit content in the starting graft polyvinyl acetate.
M (calculated) : 12,180 g/mol Composition of the graft polyvinyl alcohol obtained (calculated):
42.5 % by weight of vinyl alcohol units 53.1 % by weight of polyurethane graft base 4.4 % by weight of vinyl acetate units Result of charge titration (SCD method): < 10 ~mol of COOH/g Dissolution rate of a 200 ~m thick cast film of the graft polyvinyl alcohol in 10% strength by weight aqueous sodium hydroxide solution at 60C: 15 minutes.

Comparative Example 9 Preparation of a graft polyvinyl alcohol on a carboxyl-free polyurethane graft base 67.6 g of the graft polyvinyl acetate from Comparative Example 5 are dissolved in 67.6 g of methanol, and 4.29 g of a 10 ~ strength by weight methanolic NaOH solution are added with stirring. After about 14 minutes, a gel forms, which is mechanically comminuted. The gel granules obtained are washed with methanol and dried at 50C in vacuo.

The graft polyvinyl alcohol obtained has a degree of hydrolysis of 98 mol-%, based on the vinyl acetate unit content in the starting graft polyvinyl acetate.
M (calculated) : 11,365 g/mol Composition of the graft polyvinyl alcohol obtained - 31 - 2~52~67 (calculated):
41.4 % by weight of vinyl alcohol units 56.9 % by weight of polyurethane graft base 1.7 % by weight of vinyl acetate units Result of charge titration (SCD method): ~ 10 ~mol of COOH/g Dissolution rate of a 200 ~m thick cast film of the graft polyvinyl alcohol in 10% strength by weight aqueous sodium hydroxide solution at 60C: 8 minutes.
Comparative Example 10 Preparation of a graft polyvinyl alcohol on a carboxyl-free polyurethane gr~ft base 4,375 g of the graft polyvinyl acetate from Comparati~e Example 6 are dissolved in 4,375 g of methanol, and 266.9 g of a 10 % strength by weight methanolic NaOH
solution are added with stirring. After about 11 minutes, a gel forms, which is mechanically comminuted. The gel granules obtained are washed with methanol and dried at 50C in vacuo.

The graft polyvinyl alcohol obtained has a degree of hydrolysis of 98.4 mol-%, based on the vinyl acetate unit content in the starting graft polyvinyl acetate.
M (calculated) s 42,051 g/mol Composition of the graft polyvinyl alcohol obtained (calculated):
51.2 % by weight of vinyl alcohol units 47.2 ~ by weight of polyurethane graft base 1.6 % by weight of vinyl acetate units Result of charge titration (SCD method): < 10 ~mol of COOH/g Dissolution rate of a 200 ~m thick cast fil~ of the graft polyvinyl alcohol in 10% strength by weight aqueous sodium hydroxide solution at 60C: 15 minutes.

Table 1 shows the carboxyl group content of the polymers 20~28~7 and the solubility of 200 ~m thick cast films of un-grafted polyvinyl alcohols and graft polyvinyl alcohols in 10 % strength by weight aqueous sodium hydroxide solution at 60C. The result shows the surprisingly advantageous solubility behavior of the carboxyl-con-taining graft polyvinyl alcohols of Examples 11 to 16 according to the invention, which is significantly better than that of the carboxyl-free graft polyvinyl alcohols of Comparative Examples 7 to 10 and surprisingly better than that of commercially available carboxyl-containing polyvinyl alcohol tGohsenol T 330, manufacturer: Nippon Gohsei, Japan). By contrast, ungrafted commercially available polyvinyl alcohol (~Mowiol 8-88 and 20-98, manufacturer: Hoechst AG) is virtually insoluble in 10 %
strength by weight aqueous sodium hydroxide solution at 60C. The 200 ~m thick cast films used for the solubility tests are produced as follows from the polyvinyl alcohols (PVAL) or graft polyvinyl alcohols (graft PVAL): 15.8 g of a 10 % strength by weight aqueous PVAL or graft PVAL
solution are poured into a horizontal, flat, circular mould having a diameter of 10.7 cm, and dried at 70C.
The resultant cast film has, in the dry state, a thickness of about 200 ym and is used directly as such for the solubility tests in 10 % strength by weight aqueous sodium hydroxide solution at 60C. The time (minutes) from immersion until complete dissolution of the film sample in the aqueous sodium hydroxide solution at 60C is measured.

The carboxyl group content of the polymers is determined in a conventional manner by charge titration in aqueous polymer solutions by the SCD method.

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Claims

1. A carboxyl-containing graft polymer on a polyure-thane graft base, where the graft base contains at least

2 urethane groups in the molecule and contains units of diisocyanates and, if desired, small amounts of mono-functional isocyanates and units of diols and, if desired, small amounts of monohydroxyl compounds, and where polymer radicals comprising units of vinyl carboxy-lates having 3 to 20 carbon atoms and/or hydrolysis products thereof and further ethylenically unsaturated monomers and/or hydrolysis products thereof are polymerized or grafted onto the polyurethane graft base, wherein the polyurethane graft base molecules contain units of carboxyl-containing dimethylol or polymethylol compounds and the graft polymer is in its acid form or a salt form or a partially neutralized form.

2. A graft polymer as claimed in claim 1, wherein the polyurethane graft base molecules contain units of dimethylolcarboxylic acids of the formula I

(I) in which R is (C1-C4)-alkyl or (C8-C12)-aryl.

3. A graft polymer as claimed in claim 1, wherein the molar ratio in the polyurethane graft base molecules between the units of carboxyl-containing diols or polyols and the other monomer units present in the polyurethane graft base molecules is from 1 : X to 1 : 1 where X is ? 30.

4. A graft polymer as claimed in claim 1, wherein the polyurethane graft base molecules have a molecular weight of between 200 and 50,000 g/mol.

5. A graft polymer as claimed in claim 1, wherein the polyurethane graft base molecules contain units of aromatic and/or aliphatic and/or cycloaliphatic diisocyanates.

6. A graft polymer as claimed in claim 1, wherein the polyurethane graft base molecules contain, in the diol component, units of alkylene glycol and/or poly-alkylene glycol.

7. A graft polymer as claimed in claim 1, wherein the polyurethane graft base molecules contain, in the diol component, units of carboxyl-free low-molecular-weight diols, in addition to the units of carboxyl-containing diols.

8. A graft polymer as claimed in claim 1, wherein the polyurethane graft base molecules contain, as end groups, lower alkoxy radicals and/or hydroxyl groups.

9. A graft polymer as claimed in claim 1, wherein the terminal OH groups of the polyurethane graft base molecules are masked or blocked by adducted monoisocyan-ates.

10. A graft polymer as claimed in claim 1, wherein polymer radicals of vinyl acetate and/or vinyl propionate are grafted onto the polyurethane graft base molecules in amounts of from 10 to 95 % by weight, based on the graft polymer and/or the hydrolysis products thereof.

11. A graft polymer as claimed in claim 1, wherein polymer radicals of vinyl acetate and/or vinyl propionate and vinyl versatate and/or hydrolysis products thereof are grafted onto the polyurethane graft base molecules.

12. A graft polymer as claimed in claim 1, wherein polymer radicals of vinyl esters and other ethylenically unsaturated monomers, which can be copolymerized with the vinyl esters, and/or hydrolysis products thereof, are grafted onto the polyurethane graft base molecules.

13. A graft polymer as claimed in claim 1, wherein the vinyl ester units present in the polymer radicals grafted onto the polyurethane graft base molecules, and the other grafted-on and hydrolyzable, ethylenically unsaturated monomer units, are partially to fully hydrolyzed.

14. A process for the preparation of a carboxyl-containing graft polymer as claimed in claim 1 by free radical-initiated graft polymerization of ethylenically unsaturated polymerizable monomers in solution or without a solvent onto a polyurethane graft base and subsequent isolation of the graft polymer or subsequent hydrolysis of hydrolyzable momomer units in the grafted-on polymer radicals and isolation of the hydrolysis products, which comprises using, as the graft base, a carboxyl-containing polyurethane as claimed in claim 1 and employing, as the monomer to be grafted-on, a vinyl carboxylate having 3 to 20 carbon atoms or and the latter further ethylenically unsaturated, polymerizable and, where appropriate, copolymerizable monomers, in amounts of from 10 to 95 % by weight, based on the graft polymer, the monomers being polymerized by means of free radicals with mixing with the graft base and addition of free-radical initiators, and the resultant graft polymers subsequently being isolated or all or some of the vinyl ester units and the other hydrolyzable monomer units in the grafted-on polymer radicals of the resultant graft polymer being hydrolyzed using water and/or an alcohol, and the graft polymer obtained being isolated in its acid form or a salt form or a partially neutralized form.

15. The process as claimed in claim 14, wherein the vinyl ester monomers to be grafted on are vinyl acetate and/or vinyl propionate and vinyl versatate.

16. The process as claimed in claim 14, wherein the monomers to be grafted on are fed to the polymerization mixed with the graft base or are metered into the initially introduced graft base.

17. The process as claimed in claim 14, wherein the graft polymerization is carried out in alcoholic solution.

18. The process as claimed in claim 14, wherein the partial or full hydrolysis of the vinyl ester units in the grafted-on polymer radicals is carried out with addition of lower alcohols or mixtures of lower alcohols with water and with alkaline or acidic catalysis at temperatures below 160°C.

19. The use of an unhydrolyzed graft polymer as claimed in claim 1 or prepared as claimed in claim 14 as a hot-melt adhesive or, in combination with solvents, as a solvent-containing adhesive, if desired with additional use of crosslinking agents, for bonding diverse materials, such as metals, ceramics, plastics, fibers, films, textiles, paper and wood, and furthermore for the production of films by thermoforming or for the produc-tion of coatings.

20. The use of a hydrolyzed and/or partially hydrolyzed graft polymer as claimed in claim 1 or prepared as claimed in claim 14 as an adhesive and as a starting material for cast, pressed or extruded films, as a size or textile lubricant in textile processing, and for the production of water-soluble film packaging bags.