JP3073543B2 - Aqueous coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to an aqueous coating composition which provides a film exhibiting gloss, durability, water resistance and excellent adhesion to a substrate. The aqueous coating composition of the present invention includes a gloss paint which is a paint for a building where gloss and water resistance are required, a sealer where substrate adhesion is required and a one-coat finish paint where both properties are required, elasticity It is useful for one-coat paints.

[0002]

2. Description of the Related Art Conventionally, as an aqueous coating composition, for example, an aqueous resin dispersion of a low molecular weight using a chain transfer agent has been proposed. This composition gives a film having excellent gloss due to its low molecular weight, but has a problem that the film has poor water resistance and durability. On the other hand, when a high-molecular-weight aqueous resin dispersion is used to provide a film having improved water resistance, there arises a problem that the gloss of the film is deteriorated.

[0003] Therefore, as an aqueous coating composition which gives a film having excellent gloss without lowering water resistance, a coating composition comprising two kinds of resin emulsion components produced under specific conditions and having a specific molecular weight distribution. An article has been proposed (Japanese Patent Publication No. 63-18632). This composition can provide a film having satisfactory gloss and water resistance, but does not always have sufficient adhesion to a substrate.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an aqueous coating composition which provides a film having excellent gloss, durability, water resistance and substrate adhesion.

[0005]

According to the present invention, the following A
There is provided an aqueous coating composition comprising a component and a component B, wherein the component A and the component B are mixed at a ratio of 1: 5 to 5: 1 in terms of solid part by weight. Component A: Monomer 1 having a polymerizable unsaturated double bond
An aqueous resin dispersion obtained by emulsion polymerization of a mixture containing 0.03 to less than 0.4 part by weight of a chain transfer agent with respect to 00 parts by weight. Component B: 0.1 to 10% by weight of a crosslinkable monomer and 99.9 to 90 of a monomer having a polymerizable unsaturated double bond.
Chain transfer agent 0.4 per 100 parts by weight of the mixture by weight
An aqueous resin dispersion obtained by emulsion polymerization of a mixture containing up to 5 parts by weight.

(Specific description of the invention) 1. Aqueous resin dispersion: A component An aqueous resin dispersion of the A component constituting the composition of the present invention is composed of 100% by weight of a monomer having a polymerizable unsaturated double bond. The mixture is obtained by emulsion polymerization of a mixture containing 0.03 to less than 0.4 part by weight of a chain transfer agent per part by weight.

(Chain transfer agent) The chain transfer agent used in the present invention may be any one which is usually used for polymerization and copolymerization of vinyl monomers. For example, mercaptans such as methyl mercaptan, t-butyl mercaptan, decyl mercaptan, benzyl mercaptan, lauryl mercaptan, stearyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, mercaptoacetic acid, mercaptopropionic acid; methanol, propanol, butanol, isopropanol Butanol, t-butanol, hexanol,
Alcohols such as benzyl alcohol and allyl alcohol; and halogenated hydrocarbons such as chloroethane, fluoroethane, and trichlorethylene.

[0008] By using these chain transfer agents, a monomer can be emulsion-polymerized to an appropriate and arbitrary molecular weight. The amount of the chain transfer agent used is 0.03 to less than 0.4 part by weight of the monomer, since the dispersion of the component A is for increasing the gloss without lowering the water resistance. If the amount is less than the above, the resin becomes too high in polymer, so that the gloss becomes poor when formed into a coating. On the other hand, if it exceeds this range, the water resistance decreases.

(Monomer Containing Unsaturated Double Bond) As the monomer used in the present invention, a monomer having a glass transition temperature of -80 to + 70 ° C. of the copolymer in the resulting aqueous resin dispersion is used. One kind or two or more kinds of monomers are used. For example, the following can be mentioned.

(A) methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate,
Lower alkyl esters of acrylic acid such as t-butyl acrylate and 2-ethylhexyl acrylate; lower alkyl esters of methacrylic acid such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate and butyl methacrylate; styrene; α-methylstyrene; Acrylonitrile; methacrylonitrile; 80 to 99.5 parts by weight of a monomer selected from vinyl acetate, vinyl propionate, ethylene, vinyl chloride, and vinylidene chloride

(B) acrylamide; methacrylamide;
N-methylol acrylamide, N-methylol methacrylamide; monomers having an amide group such as glycidyl methacrylate and derivatives thereof; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid; hydroxyethyl acrylate, hydroxyethyl methacrylate,
Monomers having a hydroxyl group such as hydroxypropyl methacrylate, hydroxybutyl acrylate and hydroxybutyl methacrylate; N-phenylmaleimide, N-
(Methyl) phenylmaleimide, N- (hydroxy) phenylmaleimide, N- (methoxy) phenylmaleimide, N-benzoic maleimide, N-methylmaleimide,
N-ethylmaleimide, Nn-propylmaleimide,
It is a mixture with 20 to 0.5 parts by weight of a functional monomer selected from N-isopropylmaleimide, Nn-butylmaleimide, N-isobutylmaleimide, Nt-butylmaleimide and the like.

(Polymerization method) A resin aqueous dispersion of the component A can be obtained by emulsion polymerization of a mixture containing the above-described chain transfer agent and monomer. Emulsion polymerization can be performed by a usual method. That is, the above mixture is added to water containing an emulsifier and a protective colloid, and the mixture is heated to 90 to 95 ° C. in the presence of a polymerization initiator such as potassium persulfate, or redox polymerized in the presence of a reducing agent. Coalescence is obtained. The obtained polymer dispersion generally has a polymer concentration of about 40 to 60% by weight, but if necessary, it can be used after further diluting it with water. The resin particle size in the dispersion is generally between 0.03 and 1 micron.

Examples of emulsifiers include anionic surfactants such as sodium dialkylsulfone succinate, alkali salts of alkylsulfonic acids, alkali metal salts of oxyalkylated alcohols or alkylphenols, alkali salts of fatty acids, etc., and nonionic surfactants. Can be used. Further, a reactive emulsifier having an unsaturated double bond in the molecule may be used. The amount used is usually 0.2 to 10% by weight based on the resin content. Depending on the purpose, the cationic surfactant may be used alone or in combination with a nonionic surfactant.

2. Aqueous resin dispersion: Component B The aqueous resin dispersion of the component B constituting the composition of the present invention comprises 0.1 to 10% by weight of a crosslinkable monomer and a monomer having a polymerizable unsaturated double bond. It is obtained by emulsion polymerization of a mixture containing 0.4 to 5 parts by weight of a chain transfer agent per 100 parts by weight of a mixture of 99.9 to 90% by weight of a monomer.

The chain transfer agent and unsaturated monomer used in the production of component B can be selected from those described for component A above, and may be the same as or different from those used in production of component A. . However, the amount of the chain transfer agent used is 0.4 to 5 parts by weight of the monomer mixture because the resin dispersion of the component B is for improving the gloss and the adhesion to the substrate. When the amount is less than this range, the resin becomes too high in polymer, so that the adhesion to the base material is not sufficient when the film is formed. When the amount exceeds this range, the water resistance of the film decreases.

(Crosslinkable Monomer) Examples of the crosslinkable monomer used in the present invention include butanediol diacrylate, divinylbenzene, ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, and trimethylolpropane trimethacrylate. Is a monomer having two or more reactive double bonds in one molecule, and glycidyl methacrylate, N-methylol acrylamide, N-methylol methacrylamide, etc. may also be used. The amount of these crosslinkable monomers used is 0.1 to 10% by weight of the monomer mixture. If the amount is less than this range, the water resistance of the resulting film cannot be improved. Material adhesion is reduced.

(Polymerization method) A resin dispersion of the component B can be obtained by emulsion polymerization of the above-mentioned chain transfer agent, unsaturated monomer and crosslinkable monomer. The polymerization method is the same as that of the above-mentioned component A. is there.

3. Aqueous coating composition The aqueous coating composition of the present invention is a mixture of the above components A and B. The mixing ratio of both components is 1: 5 to 5: 1 for A component: B component in terms of the solid component weight. When the amount of the component A is more than 5 with respect to the component B, the resulting coating has good water resistance, but the gloss and the adhesion to the base material are deteriorated. In addition, the gloss component and substrate adhesion are excellent, but the water resistance is reduced.

As a method of mixing the component A and the component B, the two components may be separately prepared and mixed, or after preparing the aqueous resin dispersion of the component A, the monomer mixture of the component B may be added. A multi-stage polymerization method in which polymerization is performed by using

The aqueous coating composition of the present invention basically comprises the above two components A and B, but further according to the purpose, a dispersant, a wetting agent, an antifoaming agent, a solvent, a film forming aid, a plasticizer. Various additives such as antifreezing agents, thickeners, AE agents, water reducing agents, quick setting agents, hardening accelerators, setting retarders and the like can also be blended.

[0021]

Next, the present invention will be described in detail with reference to examples and comparative examples. Parts and% in the examples are parts by weight and% by weight unless otherwise specified. Production Example of Resin Aqueous Dispersion 100 parts of the monomer mixture shown in Table 1, 2 parts of polyoxyethylene nonylphenyl ether sulfate as anionic surfactant and 2 parts of polyoxyethylene nonylphenyl ether as nonionic surfactant 90 parts of a mixture of 1.0 part of potassium persulfate and 100 parts of ion-exchanged water.
Emulsion polymerization at 4.5 ° C. for 4.5 hours, the solid content concentration is 50%,
An emulsion having an average resin particle size of 0.3 micron was obtained.

The obtained resin aqueous dispersion has a solid resin content of 10%.
0 parts by weight, 3 parts by weight of a thickener, 0.8 parts by weight of a wetting agent, 2 parts by weight of an antifoaming agent, 14 parts by weight of a film-forming aid, and a pigment volume concentration (PVC) of about 21%. Was mixed with a pigment to prepare a paint. Using this paint, glossiness, water resistance, substrate adhesion, weather resistance, and a heating / cooling cycle test were evaluated by the following methods. Table 1 shows the results.

[Evaluation Method of Paint] Gloss Painted glass plate was coated at 150 μ / wet thickness at 20 ° C and 65%
After drying at RH for 48 hours, the 60 ° specular gloss was measured (J
IS K-5660).

A water-resistant paint was applied twice to a flexible plate (150 × 70 mm) with a brush, and dried at 20 ° C. and 65% humidity for 7 days to obtain test pieces. Then, the state of the coating film after 7 days of water immersion was observed. The state of the coating film was determined according to the coating standards of the Japan Paint Inspection Association. [Evaluation]: 10 without blistering. For those with blisters, the total area of the blisters and the size of the blisters (average diameter) are indicated by a grade symbol in comparison with the standard judgment photograph.
When blisters of different sizes are mixed, evaluation is made according to the size. The grade symbol of the standard judgment photograph is configured as shown in the following table by a combination of the total area and size of the blistered portion.

[0025]

[Table 1]

Substrate Adhesion A test piece prepared in the same manner as in the case of the water resistance evaluation was cut into a 2 mm wide cut with a cutter knife to make 25 gobangs, and a peeling test using an adhesive tape was performed. The remaining number of Goban is displayed.

Weather resistance A test piece prepared in the same manner as in the case of the water resistance evaluation was used as a weather resistance tester Super Long Sunshine W of Suga Test Instruments Co., Ltd.
The gloss retention of the coating film after irradiation with -OM (trade name) for 250 hours was measured. Gloss retention of coating film (%) = [(gloss value after 250 hours irradiation) ÷
(Gloss value at the time of blank before irradiation)] × 100 The gloss value was obtained by measuring a 60 ° reflection gloss.

Hot-Cooling Cycle Test A test piece prepared in the same manner as in the water resistance evaluation was subjected to (2
(Immersion in water at 0 ° C. ± 3 ° C. for 16 hours → dipping in water at −20 ° C. ± 3 ° C. for 4 hours → dipping in water at 50 ° C. ± 3 ° C. for 4 hours) as one cycle, and the state of the coating film after 10 cycles was observed. When there is no abnormality, it is indicated by １, when a part of the crack occurs, it is indicated by △, and when the entire crack occurs, it is indicated by ×.

Production Examples of Aqueous Coating Compositions Examples 1 to 6 and Comparative Examples 1 to 8 Using the aqueous resin dispersions obtained in the above production examples, aqueous coating compositions having the compositions shown in Table 2 were produced. . Using the obtained composition, glossiness, water resistance, substrate adhesion, weather resistance, and a heating / cooling cycle test were evaluated. The results are shown in Table 2.

[0030]

As is clear from the results shown in Table 2, the aqueous coating composition of the present invention is excellent in glossiness, water resistance and substrate adhesion.

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

[Table 4]

[0034]

[Table 5]

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI C09D 201/00 C09D 201/00 (56) References JP-A-54-54164 (JP, A) JP-A-52-51484 (JP) JP-A-62-236810 (JP, A) JP-A-60-53552 (JP, A) JP-A-53-28687 (JP, A) JP-A-56-152802 (JP, A) 63-113008 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C09D 5/02 C09D 125/08-125/14 C09D 127/06 C09D 133/06-133/12 C09D 133 / 20 C09D 201/00-201/10

Claims (1)

(57) [Claims] 1. An aqueous coating composition comprising the following components A and B, wherein the components A and B are mixed in a ratio of 1: 5 to 5: 1 by weight on a solid basis. Component A: Monomer 1 having a polymerizable unsaturated double bond
An aqueous resin dispersion obtained by emulsion polymerization of a mixture containing 0.03 to less than 0.4 part by weight of a chain transfer agent with respect to 00 parts by weight. Component B: 0.1 to 10% by weight of a crosslinkable monomer and 99.9 to 90 of a monomer having a polymerizable unsaturated double bond.
Chain transfer agent 0.4 per 100 parts by weight of the mixture by weight
An aqueous resin dispersion obtained by emulsion polymerization of a mixture containing up to 5 parts by weight.