JPH037227B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Object of the Invention The present invention relates to an aqueous copolymer dispersion composition that provides a film (such as a coating film) having excellent physical properties, particularly good water resistance and chemical resistance. (Field of Application of the Invention) The copolymer aqueous dispersion composition of the present invention is used as a coating agent (paint, etc.), a repair agent for old paint films, an adhesive, etc. in various fields. (Prior art) An aqueous copolymer dispersion in which a water-soluble low molecular weight hydrazine derivative is contained in an aqueous dispersion of a carbonyl group-containing copolymer has already been proposed (Japanese Patent Laid-Open No. 1983-1972).
110248, Japanese Unexamined Patent Publication No. 144432/1983). Such a copolymer dispersion easily forms a coating film at a film-forming temperature of 5 to 25°C, and provides a coating film with excellent adhesion to adherends such as cloth and metal, but the water resistance of the coating film is ,
Chemical resistance, blocking resistance, and adhesive strength to various adherends were insufficient. The present inventors first discovered that by incorporating a water-soluble polymeric hydrazine derivative having at least two carboxylic acid hydrazide groups in the molecule into an aqueous dispersion of a carbonyl group-containing copolymer, various properties of the coating film can be obtained. proposed that the characteristics could be improved (JP-A-Sho).
58-96643). However, even those containing such water-soluble polymeric hydrazine derivatives still have drawbacks such as insufficient water resistance, chemical resistance, and rust prevention properties. (Problems to be Solved by the Invention) The present invention aims to provide an aqueous copolymer dispersion that provides a coating film with extremely excellent water resistance, chemical resistance, rust prevention, and the like. (b) Structure of the Invention (Means for Solving the Problems) As a result of various studies to solve the above problems, the present inventors have developed an aqueous copolymer containing an aldehyde group or a ketone group. This purpose could be easily accomplished by incorporating a poorly water-soluble polymeric hydrazine derivative into the dispersion. That is, the copolymer aqueous dispersion composition of the present invention contains a poorly water-soluble polymeric hydrazine having at least two carboxylic acid hydrazide groups per molecule in an aqueous copolymer dispersion containing an aldehyde group or a ketone group. The derivative has a carboxylic acid hydrazide group of 0.02 based on the total amount of aldehyde groups and ketone groups.
It is contained in a proportion of ~5 moles. The aqueous copolymer dispersion containing aldehyde groups or ketone groups used in the present invention usually has
A method of dispersion copolymerizing a polymerizable monomer having an aldehyde group or a ketone group with another polymerizable monomer in the presence of a dispersant, or a method of copolymerizing a water-soluble copolymer having an aldehyde group or a ketone group with a dispersant. It can be easily produced by a method of polymerizing one or more types of polymerizable monomers. Monomers used in the above method include (a) n-alkyl esters of acrylic acid having 1 to 8 carbon atoms, n-alkyl esters of methacrylic acid having 2 to 8 carbon atoms, vinyl esters of saturated carboxylic acids;
A monomer selected from the group consisting of 1,3-dienes
99.4 to 25% by weight, (b) 0.1 to 20% by weight of a polymerizable carbonyl group-containing monomer having at least one aldehyde or ketone group in the molecule, (c) 3 to 5 carbon atoms. monoolefinic unsaturated carboxylic acids, unsaturated carboxylic acid amides, N-alkyl and/or N-alkylol derivatives of the unsaturated carboxylic acid amides, and monoolefinic unsaturated carboxylic acids. quantity from 0.5 to 10
% by weight, and (d) a monomer selected from the group consisting of methyl methacrylate, vinyl aromatic compounds, tertiary butyl acrylate, vinyl halides, ethylene, acrylonitrile, and methacrylonitrile.
It is preferred to use a monomer mixture containing ~74.4% by weight. As the monomer (b), a carbonyl group-containing monomer having at least one aldehyde group or ketone group and one polymerizable double bond in the molecule is used. Compounds having only an ester bond [formula] or a carboxyl group [formula] are not included in this monomer (b). Specific examples of monomer (b) include acrolein, diacetone acrylamide, formylstyrene, vinyl alkyl ketones having 4 to 7 carbon atoms (e.g. vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone, etc.), general formula (In the formula, R ¹ is H or CH ₃ , R ² is H or an alkyl group having 1 to 3 carbon atoms, R ³ is an alkyl group having 1 to 3 carbon atoms, R ⁴ is 1 to 4 Acrylic (or methacrylic)oxyalkylpropanal, diacetone acrylate, diacetone methacrylate, acetonitrile acrylate, 2-hydroxypropyl acrylate-acetylacetate, butanediol-
Examples include 1,4-acrylate-acetylacetate. Particularly preferred are diacetone acrylamide, acrolein and vinyl methyl ketone. A preferred copolymer for use in the present invention obtained by copolymerizing a monomer mixture consisting of the above monomers (a), (b), (c) and (d) in the presence of a dispersant. The resulting copolymer contained in the aqueous dispersion constitutes the copolymer in substantially the same proportion as each of the monomers (a) to (d) used. To explain the effects of each of these monomer units (a) to (d), monomer unit (a) imparts flexibility to the coating film of the composition of the present invention. The monomer unit (b) reacts with the carboxylic acid hydrazide group of the polymeric hydrazine derivative to provide a crosslinked structure and improve the physical properties of the coating film. Monomer unit (c) is a hydrophilic unit and improves dispersion stability during polymerization. The monomer unit (d) functions to adjust the hardness of the coating film. Examples of the dispersant used in the above method include anionic surfactants such as higher alcohol sulfate salts, alkylbenzene sulfonate salts, polyoxyethylene alkyl sulfate salts, polyoxyethylene alkyl phenol ether sulfate salts, and polyoxyethylene alkyl sulfate salts. Nonionic surfactants such as ethers, polyoxyethylene alkyl phenol ethers, ethylene oxide propylene oxide block polymers, sorbitan derivatives, etc. are used. Examples of the polymerization initiator in the above method include persulfates such as potassium persulfate and ammonium persulfate, hydrogen peroxide, peroxides such as benzoyl peroxide, cumene hydroperoxide, and tertiary butyl hydroperoxide. , azobisisobutyronitrile, etc. are used. Particularly preferred are water-soluble initiators and resox-type initiators. In the above method, one type of polymerizable monomer or a mixture of two or more types of polymerizable monomers is dispersed in an aqueous medium using a water-soluble copolymer having an aldehyde group or a ketone group as a dispersant. polymerize, but
Preferred water-soluble copolymers as such dispersants are:
(i) 0.5 to 99.5% by weight of carbonyl group-containing monomer units having at least one aldehyde group or ketone group and one polymerizable double bond in the molecule; (ii) 3 to 99.5% by weight;
Monoolefinic unsaturated carboxylic acid units having 5 carbon atoms, unsaturated carboxylic amide units, N-alkyl and/or N-alkylol derivative units of the unsaturated carboxylic amide, amino group-containing monomers (iii ) C1-8 alkyl ester unit of acrylic acid or methacrylic acid, vinyl aromatic monomer unit, vinyl halide unit, ethylene unit, acrylonitrile unit, methacrylonitrile unit, saturated carboxylic acid vinyl ester unit, hydroxyl group A water-soluble carbonyl group-containing copolymer containing 0 to 70% by weight of units selected from the group consisting of monomer units (e.g., hydroxyethyl acrylate units, hydroxyethyl methacrylate units) and 1,3-diene units. . Such a water-soluble copolymer dispersant having an aldehyde group or a ketone group can be obtained by mixing the respective monomer units (i) to (iii) in substantially the same ratio as the content ratio of the monomer units (i) to (iii). It can be easily obtained by polymerizing the obtained monomer mixture in an aqueous medium. Monomers used in the homopolymerization or copolymerization reaction in the above method include hard monomers such as methyl methacrylate, styrene, and t-butyl acrylate, or alcohols having 2 to 8 carbon atoms and acrylic acid or methacrylic acid. esters, soft monomers such as methyl acrylate alone or in mixtures of two or more, and if necessary, these are further blended with functional monomers such as acrylic acid and acrylamide, and crosslinking monomers such as acrolein and diacetone acrylamide. is used. Further, as the polymerization initiator in the above method, the same one as in the above method is used. In the present invention, a poorly water-soluble polymeric hydrazine derivative having at least two carboxylic acid hydrazide groups in the molecule is added to the above-mentioned aqueous dispersion of a copolymer containing an aldehyde group or a ketone group. "Poorly soluble in water" means that the solubility of the polymeric hydrazine derivative in water is 5.0 g/100 ml (water) or less at room temperature. The molecular weight of such poorly water-soluble polymeric hydrazine derivatives is usually 1,000 to 500,000, preferably 3,000 to 200,000 in terms of number average molecular weight. The poorly water-soluble polymeric hydrazine derivative used in the present invention can be easily produced, for example, by reacting a polymer having a carboxylic acid ester group with hydrazine or hydrazine hydrate (i.e., hydrazine hydrate) (Japanese Patent Publication No. 52
(See Publication No. 22878). The above polymer having a carboxylic acid ester group is
Esters of unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid and lower alcohols,
It is obtained by copolymerizing unsaturated monomers such as styrene, divinylbenzene, and isobutylene. In the present invention, the blending ratio of the copolymer aqueous dispersion containing an aldehyde group or ketone group and the poorly water-soluble polymer hydrazine derivative is The proportion of the carboxylic acid hydrazide group of the polymeric hydrazine derivative is 0.02 to 5 mol, preferably 0.1 to 2 mol, per 1 mol of the total amount. Various methods can be used to blend the copolymer aqueous dispersion and the polymeric hydrazine derivative in the present invention. The typical blending method is
A method of adding and mixing a polymer hydrazine derivative solvent solution in which a polymer hydrazine derivative is dissolved in a suitable solvent (for example, isopropyl alcohol, etc.) to an aqueous copolymer dispersion, and production of an aqueous copolymer dispersion. Sometimes, there are two methods of dissolving a polymeric hydrazine derivative in the monomer mixture. The copolymer aqueous dispersion composition of the present invention may be prepared by using a combination of two or more of the copolymer aqueous dispersion and the poorly water-soluble polymeric hydrazine derivative, or both. There is no problem. The copolymer aqueous dispersion composition of the present invention may optionally contain a poorly water-soluble polymeric hydrazine derivative and another hydrazine derivative, such as a water-soluble one having two or more carboxylic acid hydrazide groups in one molecule. It is also possible to incorporate a high molecular weight hydrazine derivative or a low molecular weight hydrazine derivative (for example, adipic acid hydrazide, sebacic acid hydrazide, etc.). However, it is desirable that such other hydrazine derivatives be used in a relatively small amount so as not to impair the effects of the present invention. Additionally, the copolymer aqueous dispersion composition of the present invention may contain pigments commonly known in the paint formulation art, extender pigments such as calcium carbonate, talc, clay, mica powder, pallite, hexametaphosphoric acid, etc. Contain potassium, sodium or ammonium salts of condensed phosphoric acid, ordinary anionic or nonionic surfactants, dispersants such as methylcellulose, ethylcellulose, propylcellulose, carboxymethylcellulose, polyvinyl alcohol, thickeners, etc. Can be done. The copolymer aqueous dispersion composition of the present invention is coated onto a suitable base material and dried, whereby the aldehyde group or ketone group in the copolymer and the carboxylic acid hydrazide group in the polymeric hydrazine derivative are combined. Because it easily reacts to form a crosslinked structure, the coating film has excellent properties such as water resistance, solubility resistance, durability, blocking resistance, and yellowing resistance, and is compatible with vinyl chloride resin, alkyd resin, etc. Good adhesion to. In particular, in the present invention, since a poorly water-soluble polymeric hydrazine derivative is blended, water resistance, chemical resistance (for example, resistance to efflorescence), and
A coating film with excellent rust prevention properties can be obtained. Therefore, the copolymer aqueous dispersion composition of the present invention is excellent as a coating agent for gloss paints, mastic top top coating materials, soft mastic top coating materials, slate materials, and the like. It is also useful as a repair agent for old paint films. (Examples, etc.) The following will be further described in detail by giving production examples, examples, and comparative examples of polymeric hydrazine derivatives. Parts and percentages in these examples are by weight unless otherwise stated. Production Example 1 of Polymeric Hydrazine Derivatives This example is an example of producing a poorly water-soluble polymeric hydrazine derivative. 86 g of methyl acrylate, 0.24 g of benzoyl peroxide, and 200 g of dioxane were placed in a reaction vessel equipped with a temperature controller, an anchor stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, and the mixture was heated to 80°C with stirring. The polymerization reaction was carried out for a period of time. Next, 50 g of hydrazine hydrate (80% aqueous solution) was added to this to form a homogeneous liquid phase, and the mixture was reacted at 80° C. for 2 hours. The obtained homogeneous liquid-phase reaction product was poured into hexane, and the formed precipitate was separated to obtain a poorly water-soluble polymeric hydrazine derivative. This derivative has a hydrazidation rate (ratio of formed carboxylic acid hydrazide groups to the total amount of carboxylic acid ester groups before reaction. The same applies to the following examples).
was 30%. Further, this derivative had a solubility in water of 0.3 g/100 ml (water) and a number average molecular weight of about 20,000. Production Example 2 of Polymeric Hydrazine Derivative This example is also an example of producing a poorly water-soluble polymeric hydrazine derivative. 50 g of methyl methacrylate, 40 g of butyl methacrylate, 0.4 g of t-butylbenzoyl peroxide, and 300 g of ethyl cellosolve were placed in the same reaction vessel as in Production Example 1, and a polymerization reaction was carried out at 90°C for 6 hours with stirring. Ta. This is then added to hydrazine hydrate (100%)
20g of was added to form a homogeneous liquid phase, and the mixture was reacted at 85°C for 4 hours. The obtained homogeneous liquid phase reaction product was treated as in Production Example 1 to obtain a poorly water-soluble polymeric hydrazine derivative. The hydrazidation rate of this derivative was 30%, the solubility in water was 0.1 g/100 mg (water), and the number average molecular weight was about 15,000. Production Example 3 of Polymeric Hydrazine Derivative This example is also an example of producing a poorly water-soluble polymeric hydrazine derivative. In a reaction vessel similar to Production Example 1, 20 g of acrylamide, 100 g of butyl acrylate, 3 g of azobisisobutyronitrile, and 300 g of ethyl cellosolve were placed, and a polymerization reaction was carried out at 70° C. for 3 hours with stirring. This is then added to hydrazine hydrate (100%)
40g of was added to form a homogeneous liquid phase and reacted at 90°C for 5 hours. The obtained homogeneous liquid phase reaction product was treated as in Production Example 1 to obtain a poorly water-soluble polymeric hydrazine derivative. The hydrazidation rate of this derivative was 15%, the solubility in water was 0.6 g/100 ml (water), and the number average molecular weight was about 10,000. Production Example 4 of Polymeric Hydrazine Derivative This example is an example of producing a water-soluble polymeric hydrazine derivative. In the same reaction vessel as in Production Example 1, a polyacrylic acid amide aqueous solution (molecular weight 30,000~
40,000, 20% aqueous solution) and 300 g of hydrazine hydrate (80% aqueous solution) were added, and the mixture was reacted at 70°C for about 10 hours with stirring. The reaction product was poured into methanol and the precipitate formed was separated to obtain a water-soluble polymeric hydrazine derivative. This hydrazine derivative has a hydrazidation rate of 70% and a water solubility of 40g/100%.
ml (water). Example 1 The following items were placed in a reaction vessel equipped with a temperature controller, anchor stirrer, reflux condenser, supply container, thermometer, and nitrogen inlet tube. 200 parts water 35% aqueous solution of sodium salt of sulfuric acid half ester of p-nonylphenol (anionic emulsifier) reacted with 20 moles ethylene oxide 5 parts p-nonylphenol reacted with 25 moles ethylene oxide (nonionic emulsifier) ) 20 parts of a 20% aqueous solution Separately, the following mixtures and aqueous solutions were prepared as supplies and supplies. Supplies Water 200 parts of the above anionic emulsifier aqueous solution (35% aqueous solution)
25 parts Styrene 242 parts n-butyl acrylate 227 parts Acrolein 11 parts Acrylic acid 10 parts Acrylamide 10 parts Feed Water 85 parts Potassium persulfate 2.5 parts A reaction vessel containing the above water and emulsifier was charged with 1/2 part of the feed. After charging 10 amounts and heating to 90° C., 1/10 amount of the feed was charged. Then add the remaining feed and the feed in small portions at the same time.
It was fed into the reaction vessel over a period of 3.5 hours. After the supply was completed, the reaction was continued at 90° C. for 1.5 hours. Then, the reaction vessel was cooled to room temperature, and aqueous ammonia was added to adjust the pH of the reaction product to 7-8. The concentration of the obtained copolymer aqueous dispersion, the total amount of copolymer, and the monomer composition of the copolymer are as shown in Table 1 below, and the monomer composition ratio is The mass ratio was almost completely consistent. To the obtained copolymer aqueous dispersion, 50 parts of a 40% isopropyl alcohol solution of the poorly water-soluble polymeric hydrazine derivative obtained in Production Example 1 was added, and the mixture was stirred for 1 hour to obtain the desired copolymer aqueous dispersion. A dispersion composition was obtained. Example 2 Instead of 227 parts of n-butyl acrylate supplied in Example 1, 40 parts of a 40% isopropyl alcohol solution of the poorly water-soluble polymeric hydrazine derivative obtained in Production Example 1 was added to n-butyl acrylate.
A polymer hydrazine derivative-containing copolymer was prepared in the same manner as in Example 1, except that 227 parts of the polymer was dissolved in 227 parts, and the poorly water-soluble polymer hydrazine derivative solution was not added to the resulting copolymer aqueous dispersion. An aqueous dispersion composition was obtained. Example 3 Using the same reaction apparatus as in Example 1, the inside of the reaction vessel was replaced with nitrogen, and then 150 parts of water was charged. Separately, the following compositions were prepared as feed materials and feed materials, respectively. Feed: 100 parts of water, 40 parts of acrylic acid, 40 parts of acrylamide, 20 parts of diacetone acrylamide. was continuously supplied. After the supply was completed, the temperature inside the reactor was raised to 90°C and maintained for 2 hours to complete the polymerization. The polymerization product is cooled and is called an aqueous copolymer solution containing 25% of the carbonyl group-containing copolymer ("Liquid A"). ) was obtained. Next, using this liquid A as a dispersant, an aqueous copolymer dispersion was produced by the method described below. That is, instead of the water and dispersant charged in the reaction vessel in Example 1, A
80 parts of liquid and 200 parts of water were charged, and polymerization was carried out in the same manner as in Example 1 except for the above, to obtain an aqueous copolymer dispersion. To this copolymer aqueous dispersion, 50 parts of a 40% isopropyl alcohol solution of the poorly water-soluble polymer hydrazine derivative obtained in Production Example 1 above was added and stirred for 1 hour to form a copolymer aqueous dispersion composition. I got it. Comparative Examples 1 and 2 10 parts of sebacic acid hydrazide (Comparative Example 1) or the aqueous solution obtained in Production Example 4 above was added to an aqueous copolymer dispersion obtained by polymerization in the same manner as in Example 1. Comparative Example 2) (10 parts of a polymeric hydrazine derivative) was added to each mixture and stirred to obtain an aqueous copolymer dispersion composition. Comparative Examples 3 and 4 10 parts of sebacic acid hydrazide (Comparative Example 3) or the aqueous solution obtained in Production Example 4 above was added to each copolymer dispersion obtained by polymerization in the same manner as in Example 3. 10 parts of a polymeric hydrazine derivative (Comparative Example 4) were added to each and stirred to obtain respective copolymer aqueous dispersion compositions. Examples 4 and 5 Polymerization was carried out in the same manner as in Example 1 except that the types of monomers and their usage ratios in the feed in Example 1 were changed as shown in Table 1. An aqueous copolymer dispersion was obtained. To each of the obtained copolymer aqueous dispersions was added 40 parts of a 40% isopropanol solution of the poorly water-soluble polymer hydrazine derivative obtained in Production Example 1 (Example 4), or 27 parts of the same isopropanol solution and phthalate. Two parts of acid dihydrazide (Example 5) were added and stirred to obtain respective copolymer aqueous dispersion compositions. The outline of the compositions obtained in each of the above Examples and Comparative Examples is as shown in Table 1. [Table] *3...Hydrazine derivative obtained in Production Example 4 Next, using each copolymer aqueous dispersion composition obtained in Examples 1 to 5 and Comparative Examples 1 to 4 above, the following method was performed. Accordingly, pigments, thickeners, wetting agents, antifoaming agents, and the like were added to each of these compositions to prepare paints having a pigment volume concentration of approximately 21%. That is, first, the following composition was prepared as a mill base. Water 14.0 parts Sodium polyphosphate 1.0 parts Emulan OC ^*1 (20%) 5.0 parts Titanium oxide 50.0 parts Antifoaming agent 0.6 parts Natrosol250HR ^*2 2.0 parts Total 72.6 parts Notes: *1...Product name of BASF, West Germany *2...Hercules Next, using this millbase, paints having the composition ratios shown below were prepared. The above mill base 72.6 parts Copolymer dispersion composition obtained in each example or comparative example 104.0 parts Texanol ^*1 /benzyl alcohol mixed solution (weight ratio 1/1) 6.0 parts Aqueous ammonia (28%) 0.5 parts Foaming agent 0.3 parts Polyoxyethylene nonyl phenol ether (20%) 5.0 parts Total 188.4 Notes: *1...Trade name of Eastman Co., Ltd. Next, the coating film physical properties of each of the obtained paints were tested in the following manner. The results were as shown in Table 2. Paint film physical property test method: (1) Water resistance test Flexible board (7.5 cm x 15 cm x thickness 0.5 cm) where the paint is specified in JIS A5403 (asbestos slate)
Apply it on the top to a thickness of 50μ and heat it at 20℃.
A test piece was prepared after drying for a week. This test piece was immersed in water at 40°C for one week, and the appearance of the coating film and the presence or absence of blisters were evaluated. (2) Efflorescence resistance test The paint was applied to a thickness of 50μ on the same flexible board as in (1) above, and dried at 20°C for one week to prepare a test piece. This test piece was immersed diagonally in water at 40°C, half immersed in the water, and left for one week. ) The elution status was evaluated visually. (3) Rust prevention test A coating film was applied to a thickness of 50μ on a mild steel plate and dried at 20°C for one week to prepare a test piece. This test piece was immersed in a 3% saline solution for 2 days, and the occurrence of rust was evaluated visually. (4) Adhesion test Apply the paint to a thickness of 50μ on the alkyd resin coating and vinyl chloride resin coating.
It was dried at 20°C for one week. The obtained coating film was subjected to a peel test using cellophane tape, and the adhesive strength at that time was evaluated. (5) Evaluation criteria Evaluation was based on the following criteria. A...Very good B...Good C...fair D...poor [Table] As is clear from the results in Table 2, the copolymer aqueous dispersion composition of the example was compared with the dispersion of the comparative example. The various substances in the coating film are extremely superior. Example 6 To an aqueous copolymer dispersion obtained by polymerization in the same manner as in Example 1, 50 parts of a 40% toluene solution of the poorly water-soluble polymeric hydrazine derivative obtained in Production Example 2 was added, and 1 The mixture was stirred for a period of time to obtain a copolymer aqueous dispersion composition (molar ratio of carboxylic acid hydrazide group/aldehyde group or ketone group was 0.36). Example 7 To an aqueous copolymer dispersion obtained by polymerization in the same manner as in Example 1, 50 parts of a 50% isopropanol solution of the poorly water-soluble polymeric hydrazine derivative obtained in Production Example 3 was added, and 1 The copolymer aqueous dispersion composition (carboxylic acid hydrazide group/aldehyde group or ketone group molar ratio is 0.23) is stirred for a period of time.
I got it. (c) Effects of the Invention The copolymer dispersion composition of the present invention has excellent physical properties of the coating film, particularly water resistance, chemical resistance (for example, efflorescence resistance), rust prevention, and adhesiveness of the coating film. They are average and excellent.

Claims (1)

[Scope of Claims] 1 A poorly water-soluble polymeric hydrazine derivative having at least two carboxylic acid hydrazide groups per molecule is added to an aqueous dispersion of a copolymer containing an aldehyde group or a ketone group. is from 0.02 to the total amount of aldehyde groups and ketone groups.
An aqueous copolymer dispersion composition containing a copolymer in a proportion of 5 moles. 2 An aqueous copolymer dispersion containing an aldehyde group or a ketone group is obtained by dispersion copolymerizing a polymerizable monomer having an aldehyde group or a ketone group with another polymerizable monomer using a dispersant. 2. The composition according to claim 1, which is a composition according to claim 1. 3. An aqueous copolymer dispersion containing an aldehyde group or a ketone group is obtained by dispersion polymerizing a polymerizable monomer using a water-soluble copolymer containing an aldehyde group or a ketone group as a dispersant. A composition according to claim 1.