JPH0132264B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an aqueous coating composition that provides a coating film with excellent water resistance, adhesion, and gloss. Most coating compositions currently in use can be broadly classified into solvent-based and aqueous-based, and aqueous-based ones can be further subdivided into emulsion-type and water-soluble types. (Prior art) Conventionally, solvent-based products have been mainly used, but
Solvent-based products pose a risk of fire and explosion, and are toxic, which can adversely affect occupational safety and health.
There are many problems such as air pollution. On the other hand, conventional water-based products have less of these problems, but emulsion-based products contain a large amount of emulsifier, resulting in poor water resistance and adhesion of the coating, and it is difficult to obtain a glossy coating. It was difficult. In addition, the molecular weight of the resin in the water-soluble type is lower than that of the emulsion type, and the water resistance and weather resistance of the coating film are inferior.Furthermore, when the resin concentration in the system is increased, the viscosity of the system increases significantly, and the coating Since the work was extremely difficult, it was not easy to obtain a coating film with a feeling of longevity. (Problems to be Solved by the Invention) As a result of intensive studies to solve these drawbacks, the present inventors have found the advantages of water-soluble coating compositions and emulsion-type coating compositions, namely: , the coating composition has a high solids concentration and a moderate viscosity, and the coating film has excellent gloss, smoothness, and adhesion, and is also water resistant. Eliminate low molecular weight substances in the resin that forms the coating film by dispersing a monomer () containing a vinyl aromatic compound in water and polymerizing the resulting emulsion, crosslinking it with a hydrophilic epoxy compound. The present invention was completed based on the discovery that the present invention can be obtained by the following method. (Structure of the Invention) That is, the present invention provides: (A); a hydrophilic epoxy compound having two or more epoxy groups per molecule; (B); in the presence of a polymeric dispersion stabilizer consisting of the following (C): An emulsion obtained by polymerizing in water a monomer () containing at least one vinyl aromatic compound, the emulsion having a functional group that reacts with the epoxy group of (A): (C ); A polymeric dispersion stabilizer containing a lipophilic polymer part and a hydrophilic polymer part in the same molecule, the lipophilic polymer part being derived from the monomer () of (B). Polymer dispersion stabilizer with good compatibility with the polymer: The above (A) and (B) are divided by the equivalent of the epoxy group in the epoxy compound of (A)/the epoxy group in the emulsion composition of (B). This is an aqueous coating composition characterized in that the equivalents of reactive functional groups are blended at a ratio of 0.05/2.5. The particles of the emulsion (B) of the present invention are polymers with extremely high molecular weights, which surround the inside and surroundings of the particles and prevent particle agglomeration.Compared to the polymer inside the particles, the polymer has a low molecular weight and is stable in dispersion. It consists of a drug part. This polymer dispersion stabilizer has a relatively lipophilic polymer portion that is highly compatible with the polymer forming the inside of the emulsion particles, so the molecules are entangled with the polymer inside the emulsion particles, making it strong. is fixed inside the particles, forming an emulsion with excellent stability. When only the emulsion (B) is made into a paint film, the paint film resembles a tiled floor. That is, the tile portion is a high molecular weight polymer inside the emulsion particles, and the binder portion is a polymeric dispersion stabilizer in the outer layer of the emulsion particles. This polymeric dispersion stabilizer has a large number of hydrophilic groups and has a relatively low molecular weight, so it has a high affinity for water, and is therefore the primary cause of negative effects on various physical properties such as water resistance of paint films. It is becoming. In the present invention, by crosslinking this polymer dispersion stabilizer using a hydrophilic epoxy compound that reacts at a relatively low temperature, the molecular weight substantially increases and the affinity for water decreases. The composition exhibits excellent water resistance in its coating film,
A coating film having desirable properties can be obtained. (A) used in the present invention; as a hydrophilic compound having two or more epoxy groups per molecule, when 1 g of the compound is dissolved in 10 g of water, 50
% or more, but any polyepoxy compound that can be substantially dispersed in water may be used, such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and glycerol. These include, but are not limited to, compounds such as polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerin polydiglycidyl ether, sorbitol polyglycidyl ether, or ortho-cresol novolac type epoxy resin which is an aqueous dispersion. do not have. Examples of vinyl aromatic compounds used in the production of the emulsion (B) used in the present invention include the following. 1 Vinyl aromatic compound general formula

[Formula], R ₃ is hydrogen or a methyl group, and X is hydrogen, a methyl group,
Ethyl group, halogen, -NO ₂ , -NH ₂ , -N
(CH ₃ ) ₂ , ―N(C ₂ H ₅ ) ₂ , ―SO ₃ H, ―SO ₃ Na,
SO ₃ NH ₄ , -CH ₂ Cl, -OH, etc. The following monomers may also be used in combination. Vinyl acetate, acrylic acid, methacrylic acid and their salts, or their esters N-vinyl-2-
These include pyrrolidone, vinyl chloride, ethylene, butadiene, acrylonitrile, carboxylic acid vinyl ester, and divinylbenzene. At least one of these monomers may be selected and used, and together with these monomers (),
-28188, Patent Application No. 1983-3508, Patent Application No. 1983-93647
It is also within the scope of the present invention to use polymers such as cellulose derivatives in the manner presented in this issue. The polymeric dispersion stabilizer used as a dispersion stabilizer in the production of the emulsion (B) consists of: a relatively lipophilic polymer portion that has good compatibility with the polymer from the monomer (); and a hydrophilic polymer. The polymer moiety is a graft polymer or block polymer that is bonded in the same molecule and has a functional group that is reactive with the epoxy group of (A). Here, the functional group reactive with the epoxy group of (A) is, for example, a carboxyl group, an acid anhydride, a carboxylic acid base, an alcoholic hydroxyl group, a phenolic hydroxyl group, an N-methylol group, a primary amino group, These include secondary amino groups, tertiary amino groups, amide groups, sulfonic acid groups, mercaptan groups, urethane groups, and the like. Usually, these functional groups are often present in the hydrophilic polymer portion of the polymeric dispersion stabilizer used for producing the aqueous masking composition of the present invention, as described in detail, and when they are not present, For example, a polymerizable monomer having the functional group may be copolymerized when synthesizing a polymer dispersion stabilizer, or acrylic acid, maleic anhydride, etc. may be copolymerized using a radical-generating compound such as benzoyl peroxide. The functional group may be introduced into the polymer dispersion stabilizer by a method such as the method described in which the functional group is added to the polymer dispersion stabilizer. The molecular weight of the polymer dispersion stabilizer is 300 to 200,000, preferably 300,000 in terms of the number average molecular weight of the polymer portion.
~20,000, and the polymer portion of is from 300 to 100,000, preferably from 500 to 30,000. Low molecular weight polymers with a number average molecular weight of less than 300 have little dispersion stabilizing effect, and
If it is larger than 100,000, the viscosity of the system becomes extremely high when used as a dispersion stabilizer, making it difficult to handle. It is important that the further polymeric portion has good compatibility with the oily substance, especially as in the present invention.
When the oily substance is a radically polymerizable unsaturated monomer, the dispersion stabilizer is fixed to the dispersion particles by having compatibility with the monomer as well as with the polymer produced from it, and the dispersion stabilizer is It is believed that the hydrophilic portion, ie, the polymer portion, is present in the aqueous phase and prevents coalescence and aggregation of the dispersion particles. In order for this part of the polymer to have good compatibility with the polymer from said monomer () used in the preparation of the emulsion of (B), it is necessary to SP (Solubility Pala
meter) value must be within ±1.0,
Preferably, the compositions of both polymers are the same. Therefore, as the monomers constituting the polymer part, in addition to the above monomers (2), all derivatives of acrylic acid or methacrylic acid are suitable, and the emulsion particles (B) are composed of these monomers. The monomers may be selected and used so that the difference in SP value between the polymer and the polymer is within ±1.0, and preferably the monomers are selected so that they are exactly the same. It is better to manufacture a combined part. Further, the polymer constituting the portion may be any hydrophilic polymer, and examples thereof include the following. (i) Water-soluble natural polymers For example, gelatin, alginic acid, alginates, starch paste, etc. (ii) Cellulose-modified water-soluble resin, such as methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, etc. (iii) Polyalkylene glycol and its derivatives Examples include polyethylene glycol, polypropylene glycol, ethylene glycol propylene glycol copolymer, and polyethylene glycol methacrylate monoester. (iv) Polymers from hydrophilic radically polymerizable unsaturated monomers For example, α,β-ethylenically unsaturated carboxylic acids (acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, salts of α,β-ethylenically unsaturated carboxylic acids, styrene sulfonic acid, styrene sulfonates, vinyl sulfonic acid, methacrylic acid or (poly)alkylene glycol esters of methacrylic acid, acrylamide, methacrylic acid amide, Vinylpyridine, N-vinyl-
A homopolymer or copolymer comprising at least one of 2-pyrrolidone, chloromethylstyrene/amine adduct, etc. (v) Copolymer of hydrophilic radically polymerizable unsaturated monomer and other radically polymerizable unsaturated monomer For example, at least one of the monomers constituting the polymer (iv) and A copolymer of a monomer other than the monomer and at least one radically polymerizable unsaturated monomer capable of radical copolymerization. (vi) Others Hydrolysates of vinyl acetate, acrylic esters, methacrylic esters, etc., or hydrolysates of copolymers consisting of vinyl acetate, acrylic esters, methacrylic esters, etc. and other monomers, anhydrous Maleic acid-modified polyethylene wax, etc. The method for producing the polymeric dispersion stabilizer used in the aqueous coating composition of the present invention is not particularly limited, but may be a method commonly known for obtaining graft polymers or block polymers, such as the method described in "Polymer" Vol. 28, March issue, P.192-P.193 (Published in 1979), published by the Society of Polymer Science and Technology Editorial Committee, "Experimental Polymer Science, Vol. 6, Polymer Reactions" ” (Published by Kyoritsu Shuppan in 1978) P.148-P.192, book,
The method described in "Graft Polymerization and Its Applications" by Fumio Ide (Kobunshi Publishing Co., Ltd., 1977), pages 5 to 148; Use of radical attack on polymers, use of polymeric polymerization initiators such as polymeric peroxides, polymeric azobis compounds, combinations of polymers with hydroxyl groups and cerium salt (iv), or use of light to polymers or polymerization systems. A method based on a radical mechanism, such as the use of radicals in polymer molecules generated by irradiation with radiation, etc., or radicals generated in polymer molecules cut by mechanical treatment. Mechanistic method using ion radicals α-
A method that utilizes a condensation reaction or ring-opening reaction between a monomer and a functional group in a polymer, such as reacting an epoxide to obtain a graft polymer. Methods for copolymerizing other monomers Examples include, but are not limited to, methods for obtaining graft products by reacting polymers with active functional groups, living polymers, etc. between polymers, etc. , at least one of the above-mentioned polymer and a monomer constituting the polymer,
The polymer dispersion stabilizer used in the present invention may be produced using the polymer and at least one monomer constituting the polymer. The polymer dispersion stabilizer produced in this way is subjected to a neutralization reaction with acrylic metal hydroxide, amines, ammonia, etc., or carboxylic acid, etc., as necessary, to make the hydrophilic polymer part water-soluble. can do. To obtain the emulsion (B) used in the production of the aqueous coating composition of the present invention, the monomer () is dispersed in water in the presence of the polymeric dispersion stabilizer described above. Emulsion polymerization is carried out. As the emulsion polymerization method, generally known emulsion polymerization methods may be used, and known radical polymerization initiators, chain transfer agents, etc. may be used.
Further, if necessary, ordinary additives for emulsion polymerization such as a solvent and a plasticizer as film-forming aids may be added. The emulsion (B) obtained in this way may contain a film-forming agent, a plasticizer, a dye/pigment, an antifoaming agent, if necessary.
Rust preventive agents, antifungal agents, etc. can be mixed and used. The epoxy compound (A) and the emulsion (B) may be mixed at a compounding ratio of 0.05 to 2.5, preferably 0.2 to 1.2, as shown by the following formula. Blending ratio = equivalent weight of epoxy groups in epoxy compound (A)/(
Equivalent of the functional group that reacts with the epoxy group of (A) in the emulsion composition of B) If this ratio is less than 0.05, the crosslinking effect of the epoxy compound (A) will be small, and if it exceeds 2.5, the reaction will not be completed. This is because the epoxy compound (A) that does not exist exists in the coating film for a relatively long time, significantly reducing the water resistance of the coating film and further reducing the hardness of the coating film. The aqueous coating composition of the present invention thus obtained can be applied to an object by a conventional coating method, and the coating film is cured by heating at room temperature or a relatively low temperature. (Effects of the Invention) The aqueous coating composition of the present invention has the following industrial advantages. a) Because it is water-based, it is advantageous in terms of resource saving, environmental issues, fire prevention, and occupational safety and health. b Cures at room temperature, saving energy and resources. c. Since it hardens at room temperature, it does not require energy sources (equipment) such as heat sources and radiation, which is advantageous industrially. d) It is also possible to significantly increase the curing rate and increase work efficiency by heating using a simple heat source. e The aqueous coating composition obtained by the present invention has water resistance, solvent resistance, chemical resistance, weather resistance, adhesion,
It is highly economical and is suitable for various paints, especially metal paints and paints for objects that cannot be heated and dried at high temperatures. Next, the present invention will be explained by examples. In the Examples and Comparative Examples, parts and % indicate parts by weight and % by weight unless otherwise specified. Example 1 [Described on page 8, line 17 of the specification; Polymerization of hydrophilic polymer moiety] In a reactor equipped with a stirrer, a reflux condenser, a thermometer, and a dropping device, 29.3 parts of 2-butoxyethanol was added. Prepare and heat to 100℃. To this, acrylic acid 10.5 under nitrogen atmosphere
parts, ethyl acrylate 7.5 parts, methyl methacrylate 16.9 parts, 2-ethylhexyl methacrylate 15.0 parts
parts, 1.0 parts of 2-hydroxyethyl methacrylate,
1.1 parts of N-methylolacrylic acid amide and α,
A mixture of 3.7 parts of α'-azobisisobutyronitrile is added dropwise over a period of 2 hours. One hour after the completion of the dropwise addition, 0.4 parts of α,α'-azobisisobutyronitrile and 3.5 parts of 2-butoxyethanol were further added, and polymerization was carried out at 100°C for 6 hours. [As described in the claims and lines 14 to 15 on page 8 of the specification; a monomer consisting of at least one vinyl aromatic compound or α,β-ethylenically unsaturated carboxylic acid or a salt thereof] Polymerization of a relatively lipophilic polymer portion with good compatibility with the polymer from the body ()] Then, the temperature in the system was lowered to 70°C, and 1.9 parts of butyl acrylate and 2-hydroxyethyl methacrylate were added.
1.5 parts, 6.8 parts of styrene, glycidyl methacrylate
0.2 parts, α,α′-azobisisobutyronitrile 0.5
and 0.2 parts of n-dodecylmetalcaptan are added dropwise over a period of 2 hours. Thereafter, the temperature was maintained at 70°C and a polymerization reaction was carried out for 8 hours. [Claim (C) in which the above and are reacted]
[Production method of polymer dispersion stabilizer]] Then, the temperature of the system was raised to 140°C, and a reaction was carried out for 2 hours. In this way, a polymer dispersion stabilizer solution with a solid content of 61.7% and an oxidation of 84% is obtained. The lipophilic polymer portion of this polymeric dispersant
SP value is about 9.1, SP of polymer in emulsion particles
The value (calculated value) was also approximately 9.1. [Polymerization of emulsion reacted with epoxy compound (A) described in claims] The above polymer dispersion stabilizer solution is placed in a reactor equipped with a separate stirrer, reflux condenser, thermometer, and dropping device.
Charge 18.5 parts, 28% aqueous ammonia, 1.5 parts, butyl acrylate, 5.7 parts, 2-hydroxyethyl methacrylate, 4.3 parts, 18.5 parts of styrene, 0.3 parts of acrylic acid, and 44.2 parts of water, and disperse while stirring thoroughly. . An aqueous solution of 0.1 part of potassium persulfate dissolved in 6.9 parts of water was added to the resulting aqueous dispersion under a nitrogen atmosphere to give 80%
The polymerization reaction is carried out at ℃ for 3 hours. [Reaction between (B) and (A) described in the claims] Solid content 40.3% and viscosity 510 cps thus obtained
Add 4.8 parts of the hydrophilic epoxy compound Denacol EX-313 (manufactured by Nagase Sangyo Co., Ltd. = glycerol polyglycidyl ether) to 100 parts of the emulsion (at 30°C), mix, and apply the mixture to a mild steel plate using a No. 30 bar coater. Table 1 shows the performance of the coating film obtained after coating and drying at room temperature for 3 days. Example 2 [Polymerization of the lipophilic polymer moiety described in lines 14 to 15 on page 8 of the specification] 71.9 parts of xylene was placed in a reactor equipped with a stirrer, a reflux condenser, a thermometer, and a dropping device. Prepare and heat to 100℃
Heat to. Methyl methacrylate under nitrogen atmosphere
13.4 parts, 2-ethylhexyl acrylate 5.8 parts,
1.5 parts of thioglycolic acid and 1.4 parts of α,α'-azobisisobutyronitrile are added dropwise over 2 hours. 3 hours after the completion of dropping, add 0.3 parts of α, α′-azobisisobutyronitrile and 3.3 parts of xylene,
The polymerization reaction is carried out at ℃ for 6 hours. Next, the temperature inside the system was raised to 140℃, and 1.5% of hydroquinone was added.
% of glycidyl methacrylate was added dropwise over 30 minutes, and the mixture was further reacted at 140°C for 4 hours. Thereafter, a portion of the xylene was removed by vacuum distillation to obtain a polymer xylene solution with a solid content of 67.4%. [Polymer dispersant obtained by copolymerizing a polymer having a polymerizable functional group at the molecular end described on page 14, line 18 of the specification with another monomer] Another same type as above In a reactor, 17.1 parts of 2-butoxyethanol was charged and heated to 100°C, and under a nitrogen atmosphere, 23.5 parts of the above polymer xylene solution, 11.8 parts of methyl methacrylate, 8.7 parts of 2-ethylhexyl acrylate, 7.1 parts of acrylic acid, and α were added. , 1.9 parts of α'-azobisisobutyronitrile were added dropwise over 2 hours. One hour after the completion of the dropwise addition, 0.3 parts of α,α'-azobisisobutyronitrile and 2.9 parts of 2-butoxyethanol were added, and the reaction was carried out at 100°C for 7 hours. After that, 26.7 parts of water was added, and part of the water and part of the organic solvent were removed by distillation, resulting in a solid content of 50.4% and an acid value.
64 polymer dispersion stabilizer-containing liquid was obtained. The lipophilic polymer portion (branch portion) of this polymer dispersion stabilizer had an SP value of about 8.6, and the SP value of the polymer in the emulsion particles was also 8.6. [Polymerization of an emulsion having a functional group that reacts with the epoxy compound (A) described in the claims] 21.1 parts of the polymer dispersion stabilizer-containing solution and 48.0 parts of water
parts, 0.4 parts of 28% ammonia water, 10.0 parts of styrene,
17.0 parts of 2-ethylhexyl methacrylate and 2.0 parts of acrylonitrile were added and dispersed with thorough stirring. Add 0.1 part of potassium persulfate to the resulting aqueous dispersion.
Add 1.4 parts of an aqueous solution to 80% under nitrogen atmosphere.
The polymerization reaction is carried out at ℃ for 3 hours. [Reaction between (B) and (A) described in the claims] Solid content 39.9% and viscosity 280 cps thus obtained
Add 4.0 parts of the hydrophilic epoxy compound Denacol EX-811 (manufactured by Nagase Sangyo Co., Ltd. = ethylene glycol diglycidyl ether) to 100 parts of emulsion (30°C) and mix. Table 1 shows the performance of the coating film obtained by coating and drying at 60°C for 100 minutes.

【table】

Claims (1)

[Scope of Claims] 1 (A) A hydrophilic epoxy compound having two or more epoxy groups per molecule (B) At least one vinyl aromatic compound in the presence of a polymeric dispersion stabilizer consisting of (C) below. An emulsion obtained by polymerizing a monomer () containing a group compound in water, the emulsion comprising:
It has a functional group that reacts with the epoxy group of (A). (C) a polymer dispersion stabilizer containing a lipophilic polymer part and a hydrophilic polymer part in the same molecule,
A polymeric dispersion stabilizer whose lipophilic polymer portion has good compatibility with the polymer from monomer (B). Equivalent weight of epoxy group/(B)
An aqueous coating composition characterized in that the equivalent of functional groups that react with epoxy groups in the emulsion composition is blended in a ratio of 0.05 to 2.5.