JP2882732B2 - Aqueous coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous coating composition having excellent water resistance, stain resistance and blocking resistance and capable of forming a tough coating film.

[0002]

2. Description of the Related Art In recent years, needs for water-based paints and inks have been increasing, and various kinds of paints and inks have been developed. However, many of them do not use only water as a solvent,
Most of them require the use of an organic solvent in order to satisfy various performance requirements.

However, due to recent severe environmental problems, a coating composition using only water as a solvent has been desired. To date, various aqueous paints and aqueous ink compositions using only water as a solvent have been developed, but a tough coating film without cracks can be formed without using an organic solvent,
An aqueous coating composition that has good drying properties, a Tg higher than room temperature, excellent stain resistance, excellent blocking resistance and excellent water resistance has not been provided.

[0004] This is a polymer aqueous dispersion (emulsion,
In the (dispersion) system, if the Tg is not lower than room temperature, a tough coating film cannot be formed because the coating film is liable to crack. Conversely, if the Tg is lower than room temperature, the stain resistance and the blocking resistance decrease, In addition, when a drying aid is used in combination, environmental problems occur and drying properties are insufficient.On the other hand, in a polymer aqueous solution, water resistance tends to be insufficient and a tough coating film is difficult to be formed. Met.

In an attempt to solve the above-mentioned problems by combining the advantages of both the aqueous polymer dispersion system and the aqueous polymer solution, emulsion polymerization was carried out in the aqueous polymer solution to obtain an aqueous polymer solution. Hybridization with a polymer aqueous dispersion was studied.

For example, JP-A-60-37135 discloses that an acrylic polymer having a carboxyl group is reacted with 0.5 to 0.05 equivalent of glycidyl (meth) acrylate based on 1 equivalent of the carboxyl group. An aqueous coating composition obtained by emulsion-polymerizing a vinyl monomer in a water-alcohol mixed solvent using an ammonium or amine salt of an acrylic polymer as a dispersion stabilizer is disclosed. Also,
JP-A-63-221105 discloses a method in which a mixture of a vinyl polymer, a vinyl monomer, and a polymerization initiator is polymerized while being added to a hydrophilic organic solvent, and then an aqueous alkali solution is added and dispersed. A method for producing an aqueous dispersion is disclosed.

However, each of these requires the use of a different polymerization method for each type of composition, which is inconvenient for a wide variety of commercial products, and requires a simple method of preparing an aqueous polymer solution and aqueous polymer dispersion. It has been desired to develop a material that can solve the above problems by blending.

For this reason, blends of various aqueous polymer solutions and aqueous polymer dispersions have been studied. However, in conventional aqueous polymer solutions, few are widely compatible with various aqueous polymer dispersions. In many cases, there has been a problem that the water resistance of the polymer aqueous dispersion is significantly impaired, which has hindered practical use.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an aqueous coating composition in which a wide variety of polymer aqueous dispersions can be used.

It is another object of the present invention to provide an aqueous coating composition which can form a tough coating film without cracks without using an organic solvent and has good drying properties.

Still another object of the present invention is to provide an aqueous coating composition capable of forming a coating film having a Tg higher than room temperature, excellent stain resistance, excellent blocking resistance and excellent water resistance. Is to do.

[0012]

That is, the present invention provides:
(A) 30 to 90% by weight of methyl methacrylate, (b)
A secondary transition temperature comprising 0 to 30% by weight of an aromatic vinyl compound, 4 to 20% by weight of (c) an acid group-containing vinyl compound and 0 to 66% by weight of (d) another copolymerizable vinyl monomer. Is 30-110 ° C, and the weight average molecular weight is 6,000-3.
0,000, and an acid value Ri <br/> Ah in. 35 to 110 mg KOH / g, polymerized vinyl polymer by suspension polymerization (I) was neutralized with a base, dissolved in water A vinyl polymer aqueous solution and an aqueous dispersion of the polymer (II) having a secondary transition temperature of 30 to 120 ° C. and a weight average molecular weight of 200,000 to 2,000,000 are prepared by polymer solid content ratio. It is an aqueous coating composition mixed so that polymer (I) / polymer (II) = 5/95 to 60/40.

[0013]

The vinyl polymer (I) used in the present invention comprises:
(A) 30 to 90% by weight of methyl methacrylate, (b)
It is composed of 0 to 30% by weight of an aromatic vinyl compound, (c) 4 to 20% by weight of an acid group-containing vinyl compound, and (d) 0 to 66% by weight of another copolymerizable vinyl monomer.

[0014] Methyl methacrylate (a) is an essential component for imparting hardness to the vinyl polymer.
It is used in a proportion of 90% by weight. If the amount is less than 30% by weight, the hardness decreases, while if it exceeds 90% by weight, the water solubility decreases. Further, when the content is outside the above range, the compatibility with the aqueous dispersion of the polymer (II) is also lacking.

The aromatic vinyl compound (b) has the effect of imparting water resistance to the coating film, and is copolymerized in a range of up to 30% by weight, preferably in a range of 0 to 25% by weight. However, if it exceeds 30% by weight, the water solubility is lowered and the compatibility with the aqueous dispersion of the polymer (II) is also lost, so that it is not suitable. Specific examples of the aromatic vinyl compound include styrene, α-methylstyrene, p-methylstyrene, and benzyl (meth) acrylate, among which styrene is particularly preferred.

The acid group-containing vinyl compound (c) imparts an acid group to the vinyl polymer and is a vinyl compound having an acidic group such as carboxylic acid or sulfonic acid.
The acid value of the vinyl polymer (I) obtained in the range of 4 to 20% by weight is 35 to 110 mgK.
OH / g is used. Specific examples of the acid group-containing vinyl compound include monobasic acids such as acrylic acid, methacrylic acid and crotonic acid; dibasic acids such as fumaric acid, maleic acid and itaconic acid; and partial esters thereof. These can be used as a mixture of two or more kinds. In particular, when a vinyl compound having a carboxylic acid is copolymerized, a compound having good water solubility and compatibility with an aqueous dispersion of the polymer (II) can be obtained. Also,
In particular, when copolymerized with methacrylic acid or acrylic acid, one having extremely good water solubility and compatibility can be obtained.

The other vinyl monomer (d) copolymerizable with the above monomers (a) to (c) is used in an amount of 0 to 66% by weight, and at least one polymerizable monomer is used. It can be arbitrarily selected from those having a suitable vinyl group according to the purpose. Specific examples of the vinyl monomer (d) include ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, cyclohexyl (meth) acrylate, (Meth) having an alkyl group having 1 to 18 carbon atoms, such as 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth) acrylate
Alkyl acrylate; hydroxyalkyl (meth) acrylate such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate; glycol di (meth) acrylate such as ethylene glycol di (meth) acrylate and butylene glycol (meth) acrylate Meth) acrylates; alkylamino (meth) acrylates such as dimethylaminoethyl (meth) acrylate; and dimethylaminoethyl (meth) acrylate methyl chloride salt, cyclohexyl (meth) acrylate, allyl (meth) acrylate, trimethylolpropanetri (meth) acrylate ) Acrylate, glycidyl (meth) acrylate, vinyl acetate, vinyl propionate, (meth) acrylonitrile and the like.

The secondary transition temperature of the vinyl polymer (I) is as follows:
It is necessary to be 30 to 110 ° C, preferably 35 to 105 ° C, as measured by the DSC method. If the temperature is lower than 30 ° C., the stain resistance is insufficient or the blocking resistance is reduced. On the other hand, when the temperature exceeds 110 ° C., the coating film becomes brittle. Regarding the molecular weight of the vinyl polymer, the weight average molecular weight measured by the GPC method needs to be 6,000 to 30,000, and preferably 8,000 to 25,000. 6,
If it is less than 000, the coating film tends to be brittle. Also, 30,
If it exceeds 000, the water solubility tends to decrease, and the polymer (I
It also lacks compatibility with the aqueous dispersion of I). The acid value is determined based on the discoloration point of phenolphthalein by titrating KOH dissolved in ethanol dropwise to an aqueous solution of the vinyl polymer to neutralize 1 g of the vinyl polymer.
When expressed in mg of OH, 35 to 110 mgKOH /
g, preferably 40-110 mg KO
H / g. When the amount is less than 35 mgKOH / g, the water solubility decreases. When the amount exceeds 110 mgKOH / g, the polymer (I
The compatibility with the aqueous dispersion of I) is reduced , and the water resistance tends to be insufficient.

As the polymerization method for producing the vinyl polymer (I), a suspension polymerization method, a solution polymerization method, a bulk polymerization method and the like can be applied. In particular , those produced by the suspension polymerization method are : Excellent water resistance and aqueous dispersion of polymer (II)
Is excellent since it has excellent compatibility with Furthermore , rather than a method in which the monomer is divided into several degrees while the polymerization is proceeding and charged into the system or a polymerization method in which the monomer is dropped into the system over several hours while the polymerization is proceeding, the monomer is used instead of the monomer. It is preferable to use those produced by the batch charging method of monomers, which starts polymerization after being put into the system at once.
No. These are considered to be mainly effects from the viewpoint of copolymerizability. As the dispersant in the suspension polymerization, 70 to 1
Known water-soluble polymers such as polyvinyl alcohol having a saponification degree in the range of 00% and a soda salt of polymethacrylic acid can be used. The solvent in the solution polymerization is not particularly limited as long as it dissolves the monomer and the polymer used in the present invention, but alcohols such as methanol, ethanol, isopropyl alcohol and n-butanol; ethyl cellosolve, cellosolve acetate,
Butyl carbitol; glycols such as propylene glycol methyl ether; acetates such as ethyl acetate and butyl acetate; ketones such as methyl ethyl ketone and methyl isobutyl ketone; As the polymerization catalyst, conventionally known initiators such as an azo initiator such as azobisisobutyronitrile and a peroxide initiator such as benzoyl peroxide can be arbitrarily used according to the purpose.

Further, a chain transfer agent such as n-dodecyl mercaptan or α-methylstyrene dimer may be added to the above vinyl monomer mixture, if necessary, for controlling the molecular weight of the vinyl polymer (I). be able to.

The vinyl polymer (I) thus obtained is imparted with water solubility by neutralizing acid groups in the vinyl polymer (I) with a base to form a salt. And
Dissolved in water. It is not necessary that all the acid groups of the vinyl polymer (I) be neutralized, and usually 30% or more of the acid groups are neutralized.

Examples of the base used for neutralization include ammonia, triethylamine, propylamine, diethylamine, tripropylamine, dibutylamine, amylamine, 1-aminooctane, 2-dimethylaminoethanol, ethylaminoethanol, and 2-diethylaminoethanol. , 1-amino-2-propanol, 2-amino-
1-propanol, 3-amino-1-propanol, 1
-Dimethylamino-2-propanol, 3-dimethylamino-1-propanol, 2-propylaminoethanol, ethoxypropylamine, aminobenzyl alcohol, volatile compounds such as morpholine.

On the other hand, the aqueous dispersion of the polymer (II) has a secondary transition temperature of 30 to 120 ° C. and a weight average molecular weight of 200,
The type of the polymer is not particularly limited as long as it uses a polymer of 2,000 to 2,000,000, and examples thereof include an acrylic resin, an alkyd resin, a urethane resin, an epoxy resin, a polyester resin, Examples include vinyl resins such as polyvinyl chloride and polyvinyl acetate, and cellulose resins such as nitrocellulose and cellulose acetate butyrate.

When the secondary transition temperature of the polymer (II) is less than 30 ° C., the blocking resistance is insufficient, and when it exceeds 120 ° C., the coating film is liable to crack. If the weight average molecular weight is less than 200,000, the toughness of the coating tends to be insufficient, and if it exceeds 2,000,000, the coating tends to crack.

The method for producing the aqueous dispersion of the polymer (II) includes a method by an emulsion polymerization method, a method of dissolving a polymer containing an acid group such as a carboxylic acid in a hydrophilic organic solvent, and a method of dissolving a polymer in a hydrophilic organic solvent. A method of neutralizing a polymer organic solvent solution prepared by solution polymerization with a base with a base and dispersing it in water, dissolving the polymer in a hydrophilic organic solvent, and then applying a high shear force to water containing a surfactant And various methods such as a method of dispersing the particles by applying a pressure. Among them, those produced by the emulsion polymerization method are particularly preferable because of their good water resistance.

The aqueous coating composition of the present invention comprises an aqueous solution of the vinyl polymer (I) and an aqueous dispersion of the polymer (II) in a ratio of polymer solid content of polymer (I) / polymer. Coalescing (II)
= 5/95 to 60/40. If the mixing ratio is less than 5/95, it becomes difficult to form a tough coating film free from cracks without using a film-forming aid. On the other hand, if the mixing ratio exceeds 60/40, the water resistance decreases. The method of mixing the aqueous solution of the vinyl polymer (I) and the aqueous dispersion of the polymer (II) is not particularly limited.
Both solutions may be mixed at room temperature, or both solutions may be mixed after heating. The aqueous solution of the vinyl polymer (I) is usually used at a concentration of 15 to 35% by weight. The aqueous dispersion of the polymer (II) usually has a concentration of the polymer (II) of 25 to 60% by weight.

The aqueous coating composition of the present invention thus obtained contains additives such as an antifoaming agent, a pigment dispersant, and a preservative in order to exhibit high performance as a paint and an ink. It is also possible to use it.

The coating method for forming a coating film on the surface of various materials using the aqueous coating composition of the present invention includes spray coating, roller coating, bar coating, air knife coating, and casting. Method, brushing method, dipping method, etc., are not particularly limited.

When the aqueous coating composition of the present invention is used as a paint, it is usually used at a temperature in the range of room temperature to 60 ° C. for 10 seconds to
After drying for 10 hours, a coating film is formed.

[0030]

The present invention will be described below in detail with reference to examples. In the examples, “parts” and “%” indicate “parts by weight” and “% by weight”, respectively. (1) Production of vinyl polymer I-1 In a polymerization apparatus equipped with a stirrer, a thermometer, and a reflux condenser and capable of both heating and cooling, 200 parts of deionized water was mixed with polyvinyl alcohol (degree of saponification). 80%, degree of polymerization 1,70
0) After adding 0.6 part and stirring to completely dissolve the polyvinyl alcohol, the stirring was stopped once, and 70 parts of methyl methacrylate (hereinafter abbreviated as MMA), 10 parts of styrene (hereinafter abbreviated as St), n-butyl acrylate (hereinafter abbreviated as n-BA) 10 parts, methacrylic acid (hereinafter MA)
A) (10 parts) was added and stirring was started again, and 0.5 parts of azobisisobutyronitrile (hereinafter abbreviated as AIBN) and 4 parts of n-dodecylmercaptan (hereinafter abbreviated as n-DM) were added and added. C., and the reaction was carried out for 3 hours so that the reaction temperature was maintained at 75 to 80.degree. C., and then the temperature was raised to 95.degree. C. and maintained for 1 hour to terminate the reaction. The obtained polymer had a molecular weight of 12,000, an acid value of 65 mgKOH / g, and a secondary transition temperature of 87 ° C. (2) Production of Vinyl Polymers I-2 to I-11 Table 1 was prepared in the same manner as in the method of producing the vinyl polymer I-1.
Are polymerized using the radical initiator and the chain transfer agent shown in Table 1, respectively, and the characteristic values of the obtained polymer are shown in Table 2.

[0031]

[Table 1] Explanation of symbols BPO: benzoyl peroxide n-BMA: n-butyl methacrylate EHA: ethylhexyl acrylate MeSt: α-methylstyrene dimer AA: acrylic acid

[0032]

[Table 2] (3) Production of vinyl polymer I-12 Isopropyl alcohol (hereinafter abbreviated as i-PA) 100 in a polymerization apparatus equipped with a stirrer, a thermometer, and a reflux condenser and capable of both heating and cooling. Part, MMA 65 parts, St
10 parts, 12 parts of n-BA, 13 parts of MAA, 2 parts of AIBN and 3 parts of n-DM were added, stirring was started, the temperature was raised to 80 ° C., polymerization was started, and 0.2 parts of AIBN was added every one hour. The temperature was maintained for a time to complete the polymerization, and the solid content was 51%.
An i-PA solution of a vinyl polymer having a viscosity of 10,000 cps was obtained. Thereafter, the solution was put into a vat, and i-PA was evaporated in a dryer heated to 50 ° C. to obtain a solid content of 99.5.
% Of a vinyl polymer solid. The obtained polymer had a molecular weight of 13,000, an acid value of 85.5 mgKOH / g, and a secondary transition temperature of 84 ° C. (4) Production of vinyl polymer I-13 100 parts of i-PA was added to a polymerization apparatus equipped with a stirrer, a thermometer, and a reflux condenser and capable of both heating and cooling, and stirring was started. ℃ 65, MMA 65 parts, St10
, A mixture of 12 parts of n-BA, 13 parts of MAA and 3 parts of AIBN were added dropwise over 4 hours, and then every other hour, A
The polymerization was terminated by maintaining the temperature for 4 hours while adding 0.1 part of IBN to obtain an i-PA solution of a vinyl polymer having a solid content of 50% and a viscosity of 2,000 cps. Thereafter, the solution was placed in a vat, and dried in a dryer heated to 50 ° C. in an i-PA.
Was evaporated to obtain a vinyl polymer solid having a solid content of 99.5%. The obtained polymer had a molecular weight of 11,000 and an acid value of 8
5.5 mgKOH / g, the secondary transition temperature was 84 ° C. (5) Dissolution of vinyl polymer in water 50 g of vinyl polymer I-1 and deionization in a 300 ml flask equipped with a stirrer, a thermometer, and a reflux condenser and capable of both heating and cooling. 148 g of water was added, stirring was started, and 3.5 g of 28% aqueous ammonia was gradually added. Thereafter, the temperature was raised to 50 ° C., and the temperature was maintained for 2 hours to complete the dissolution. A lysate was obtained. The resulting aqueous melt had a solids content of 25% and a viscosity of 500 cps. For the vinyl polymers I-2 to I-13, the addition amounts of 28% ammonia water and deionized water were calculated according to the following calculation method, and the dissolution operation was performed in the same manner. However, the vinyl polymer I-6 could not be dissolved. Required ammonia water (g) = A ÷ 56.1 ÷ 1000 × 5
0 × 17 ÷ 0.28 (where A represents the acid value (mg KOH / g) of the polymer.) Required deionized water (g) = 150−required ammonia water (g) × 0.72 (6) Production of Polymer Aqueous Dispersion II-1 In a polymerization apparatus equipped with a stirrer, a thermometer, and a reflux condenser and capable of both heating and cooling, 100 parts of deionized water and a polymer having 35 oxyethylene units were prepared. 2 parts of oxyethylene nonyl phenyl ether, sodium lauryl sulfate 1
And 0.5 parts of potassium persulfate were added, stirring was started, the temperature was raised to 70 ° C., and a mixture of 57 parts of MMA, 25 parts of n-butyl methacrylate, 15 parts of n-BA, and 3 parts of MAA was added over 4 hours. After the dropwise addition, the temperature was raised to 80 ° C., and the temperature was maintained for 2 hours to terminate the reaction, thereby obtaining an aqueous polymer dispersion. The resulting polymer had a secondary transition temperature of 52 ° C., a weight average molecular weight of 1,000,000, and this aqueous dispersion had a solid content of 50% and a viscosity of 3,000 cps. (7) Production of Polymer Aqueous Dispersion II-2 A mixture of a vinyl monomer of 85 parts St, 14 parts of ethylhexyl acrylate and 1 part of MAA was polymerized by the same production method as in (6), and the secondary transition temperature was determined. A polymer having a weight average molecular weight of 500,000 at 67 ° C. was obtained, and the aqueous dispersion had a solid content of 50% and a viscosity of 800 cps. (8) Production of Polymer Aqueous Dispersion II-3 25 parts of i-PA, MMA in a polymerization apparatus equipped with a stirrer, thermometer, reflux condenser and capable of both heating and cooling.
42 parts, 23 parts of St, 28 parts of n-BMA, 7 parts of MAA acid and 0.1 part of AIBN are charged, then the temperature is raised to 80 ° C., and the temperature is increased while adding 0.1 part of AIBN every other hour. Hold for 7 hours, then cool to 50 ° C.,
% Ammonia water and 150 parts of deionized water were gradually added, and then the temperature was raised to 95 ° C. over 3 hours.
-PA was distilled off to about 1% of the initial charge to obtain an aqueous dispersion of the polymer. The secondary transition temperature of the obtained polymer was 76 ° C., the weight average molecular weight was 350,000, and the aqueous dispersion had a solid content of 40% and a viscosity of 200 cps. (9) Production of Polymer Aqueous Dispersion II-4 13 parts of dimethylolpropionic acid, 80 parts of N-methyl-2-pyrrolidone, 100 parts of polytetramethylene glycol in a 1000 ml reaction vessel equipped with a thermometer, a stirrer and a condenser. , 5 parts of trimethylolpropane and 90
The mixture was dissolved by heating to ° C. Next, 48 parts of isophorone diisocyanate was added, and after stirring for 10 minutes, 0.1 part of dibutyltin dilaurate was added, the temperature was raised to 95 ° C, and the reaction was carried out for 1 hour.

The thus obtained oligomer having a hydrophilic group is neutralized with 5 parts of triethylamine, and then deionized water 3
Then, the mixture was stirred for 1 hour to obtain an aqueous dispersion. The secondary transition temperature of the obtained polymer was 40 ° C., the weight average molecular weight was 220,000, and the aqueous dispersion had a solid content of 29% and a viscosity of 8,000 cps.

Example 1 A blend solution 1 was prepared by measuring 60 g of a 25% solids aqueous solution of a vinyl polymer I-1 and 120 g of an aqueous polymer dispersion II-1 in a beaker and gently mixing with a stick. . In this case, the vinyl polymer I-1 and the polymer aqueous dispersion II-
The polymer solids ratio of 1 is 20:80. 24 hours after blending, no precipitate was observed, and the compatibility as a solution was confirmed. Also, when the blend liquid 1 was applied to a glass plate so as to have a solid film thickness of 80 μm, and dried under an environment of 15 ° C. and 60% RH, it became tack-free in 2 minutes.
A transparent coating film without cracks was formed. Even when this coating film was rubbed with a nail, no damage such as a scratch was found on the coating film. Further, two coated glass plates were prepared, and the coating films were overlapped in such a manner that they were joined together. After being allowed to stand at 30 ° C. and 70% RH for 2 days, no fusion of the coating film was observed. The coated glass plate was placed in deionized water at 30 ° C for 2 hours.
When the film was held for 0 hour, taken out, and left in a room at 15 ° C. and 60% RH for 1 hour, no change was observed in the coating film.

Examples 2 to 6 and Comparative Examples 1 to 11 Blends were prepared and evaluated in the same manner as in Example 1 and the results are shown in Table 3 below. In addition, the symbol of the result of each evaluation test means the following. [Compatibility] Solution S: No precipitate is observed.

IS: Precipitated. Coating C: The coating is transparent and has good compatibility.

VSH: The coating film is slightly opaque and the compatibility is slightly poor.

SH: The coating film is more opaque than in the VSH stage, and the compatibility is lower than in the VSH stage.

H: The coating film is opaque from the stage of SH,
Compatibility is lower than the SH stage (impractical level). [Film-forming property] The film is coated on a glass plate so as to have a solid film thickness of 80 μm, and dried at 15 ° C. and 60% RH. Good: A good coating film free of cracks. Poor: cracks in the coating film. [Abrasion resistance (toughness of coating film)] A solid film having a thickness of 80 μm is applied to a glass plate, dried at 15 ° C. and 60% RH, and then rubbed with a nail. Good: No damage such as a scratch is observed on the coating film. Bad: The coating film is damaged such as being scratched or cracked. [Blocking resistance] A solid film thickness of 80 μm was applied to each of two glass plates at 15 ° C. and 60% R
After drying under an environment of H, the coatings are layered together and left for 2 days in an environment of 30 ° C. and 70% RH. Good: no fusion of the coating film was observed. Poor: The coating film is fused. [Water resistance] Apply to a glass plate so as to have a solid film thickness of 80 μm, dry in an environment of 15 ° C. and 60% RH.
And left in a room at 60% RH for 1 hour. Good: no change is observed in the coating film. Poor: Some damage such as clouding of the coating film.

[0040]

[Table 3]

[0041]

According to the aqueous coating composition of the present invention, a tough coating film without cracks can be formed without using an organic solvent, and the coating film has a Tg higher than room temperature and has stain resistance. It has excellent blocking resistance and water resistance, and also has good drying properties. Further, since the aqueous solution of the vinyl polymer used in the present invention is widely compatible with various polymer aqueous dispersions, the simple blend of these can be used to hybridize the two, and a wide variety of aqueous coating compositions of various types can be obtained. Product development can be easily implemented.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-275752 (JP, A) JP-A-3-269033 (JP, A) JP-A-3-192172 (JP, A) JP-A-50- 37733 (JP, A) JP-A-51-7033 (JP, A) JP-A-50-122528 (JP, A) JP-A-3-504138 (JP, A) (58) Fields investigated (Int. ⁶ , DB name) C09D 133/04-133/14 C09D 5 / 00,11 / 10 C08L 33/04-33/14

Claims (1)

(57) [Claims] (A) methyl methacrylate 30 to 90
% By weight, (b) 0 to 30% by weight of an aromatic vinyl compound,
(C) 4 to 20% by weight of an acid group-containing vinyl compound and (d) 0 to 66% by weight of another copolymerizable vinyl monomer.
Having a secondary transition temperature of 30 to 110 ° C, a weight average molecular weight of 6,000 to 30,000, and an acid value of 35 to 1
10 mg KOH / g der it is, is polymerized by suspension polymerization
A vinyl polymer aqueous solution obtained by neutralizing the vinyl polymer (I) with a base and dissolving it in water;
20 ° C, weight average molecular weight of 200,000 to 2,000
An aqueous dispersion of the polymer (II) having a molecular weight of 000 was mixed with the polymer (I) / polymer (II) at a polymer solid content ratio of 5/95.
An aqueous coating composition which is mixed so as to be 60 to 40/40.