JP4093746B2 - Copolymer latex for chipping-resistant water-borne coatings - Google Patents

Description

【００４２】
【発明の効果】
以上のとおり、本発明における特定の共重合体ラテックスを耐チッピング水性塗料用共重合体ラテックスとして使用することにより、耐チッピング性と下地鋼板と塗膜の密着性、耐水性等の塗膜特性および、塗布作業性とのバランスを著しく改良できるものである。[0001]
[Field of the Invention]
The present invention relates to a copolymer latex for chipping-resistant water-borne coatings for coating a metal surface and protecting the metal product from chipping. More specifically, the present invention relates to a copolymer latex for a chipping-resistant water-based paint used for surface coating of a portion where a stone is easily hit during traveling, such as an under-floor portion of a vehicle body such as an automobile.
[0002]
[Prior art]
In recent years, bituminous protective materials have been widely used in automobile floors, side seals, fail tanks, front aprons, and tire house parts because they have anti-rust properties and are inexpensive. The pebbles and stepping stones that are rolled up during driving and the salt and rock salt that have been rapidly spreading in recent years have caused cracks and impact scratches on the coating, and as a result, corrosion from the damaged part has become a problem. . In order to prevent such defects, so-called chipping resistant paints have been developed and put into use. As such chipping-resistant coating materials, emulsion-based, vinyl chloride resin plastisol, urethane or polyester coating materials, bituminous improved products, etc. have been developed (Japanese Patent Laid-Open Nos. 63-10678 and 64-29472). issue).
[0003]
On the other hand, in recent years, in the paint and adhesive fields, switching from so-called solvent-based to water-based systems has progressed due to pollution problems such as environmental pollution in the atmosphere, fire hazards, hygiene problems during work, energy conservation, and various resource problems. Such a tendency is no exception in chipping-resistant paints used for undercoats of automobiles.
[0004]
In order to exhibit the performance of the chipping resistant paint and protect the metal product, in addition to the excellent chipping resistance of the paint, the adhesion between the coating film and the base metal is extremely important. In addition, since the chipping-resistant paint is often used in parts that are susceptible to water splashing, such as the floor of an automobile, the water resistance of the coating film is important as well as the adhesion. However, conventional chipping-resistant water-based paints cannot be said to have sufficient adhesion and water resistance compared to solvent-based paints.
[0005]
Furthermore, chipping-resistant water-based paints have often been problematic in terms of the occurrence of cissing after application to a metal substrate.
[0006]
In order to solve these problems, for example, in JP-A-59-75954, JP-A-2-28269, and JP-A-4-202262, a styrene-butadiene copolymer latex may be used in a paint. Proposed. However, none of these can be said to sufficiently overcome the above-mentioned problems of improving the balance between chipping resistance, coating film properties and painting workability.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to obtain a copolymer latex for chipping-resistant water-borne coatings that can remarkably improve the balance between chipping resistance, adhesion between a base steel sheet and a coating film, coating properties such as water resistance, and coating workability. And
[0008]
[Means for Solving the Problems]
That is, the present invention is 60-80% by weight of conjugated diene monomer, 5-20% by weight of vinyl cyanide monomer, 5-20% by weight of unsaturated carboxylic acid alkyl ester monomer, ethylenically unsaturated. 0.5 to 5% by weight of carboxylic acid monomer, 0.5 to 5% by weight of unsaturated monomer having a hydroxyalkyl group, and 0 to 29% by weight of other vinyl monomers copolymerizable therewith In a ring selected from 6 to 25 parts by weight of cyclopentene, cyclohexene, cycloheptene, 4-methylcyclohexene, and 1-methylcyclohexene with respect to 100 parts by weight of the monomer. The present invention provides a composition for chipping-resistant water-borne coatings comprising a copolymer latex obtained by emulsion polymerization in the presence of a saturated hydrocarbon.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The components constituting the copolymer latex in the present invention are aliphatic conjugated diene monomers, vinyl cyanide monomers, unsaturated carboxylic acid alkyl ester monomers, and ethylenically unsaturated carboxylic acid monomers. , Unsaturated monomers having a hydroxyalkyl group, and other monomers copolymerizable therewith.
[0010]
Examples of the aliphatic conjugated diene monomer in the present invention include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, and 2-chloro-1,3-butadiene. Examples thereof include butadiene, substituted linear conjugated pentadienes, substituted and side chain conjugated hexadienes, and one or more kinds can be used. 1,3-butadiene is particularly preferable.
[0011]
Examples of the vinyl cyanide monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile and the like, and one or more can be used. Particularly preferred is acrylonitrile.
[0012]
Unsaturated carboxylic acid alkyl ester monomers include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, glycidyl methacrylate, dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate, dimethyl itaconate , Monomethyl fumarate, monoethyl fumarate, 2-ethylhexyl acrylate and the like, and one kind or two or more kinds can be used. Particularly preferred is methyl methacrylate.
[0013]
Ethylenically unsaturated carboxylic acid monomers include ethylenically unsaturated monocarboxylic acid monomers such as acrylic acid, methacrylic acid and crotonic acid, and ethylenically unsaturated dicarboxylic acid monomers such as fumaric acid, itaconic acid and maleic acid. A polymer can be mentioned. In particular, an ethylenically unsaturated dicarboxylic acid monomer is preferably included, and among these, itaconic acid is particularly preferably included.
[0014]
Examples of unsaturated monomers containing hydroxyalkyl groups include β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, 3-chloro-2-hydroxy Propyl methacrylate, di- (ethylene glycol) maleate, di- (ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis (2-hydroxyethyl) maleate, 2-hydroxyethyl methyl fumarate and the like. Two or more kinds can be used. In particular, β-hydroxyethyl acrylate is preferable.
[0015]
Examples of other vinyl monomers copolymerizable with these include aromatic vinyl monomers and unsaturated carboxylic acid amide monomers.
[0016]
Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, methyl α-methylstyrene, vinyltoluene, divinylbenzene, and the like, and one or more can be used. Styrene is particularly preferable.
[0017]
Examples of unsaturated carboxylic acid amide monomers include acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, N, N-dimethylacrylamide, and the like, and one or more of them can be used. Particularly preferred is acrylamide.
[0018]
In addition to the above monomers, fatty acid vinyl esters such as vinyl acetate and vinyl propionate, aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, 2-vinylpyridine Basic monomers such as 4-vinylpyridine, vinyl chloride, vinylidene chloride and the like can be used.
[0019]
About said monomer composition, 60-80 weight% of conjugated diene monomers, 5-20 wt% of vinyl cyanide monomers, 5-20 wt% of unsaturated carboxylic acid alkyl ester monomers, 0.5 to 5% by weight of ethylenically unsaturated carboxylic acid monomer, 0.5 to 5% by weight of unsaturated monomer having a hydroxyalkyl group and other vinyl monomers copolymerizable therewith 0 It must be ˜29% by weight.
[0020]
If the amount of the aliphatic conjugated diene monomer is less than 60% by weight, the chipping resistance of the chipping-resistant paint containing the copolymer latex of the present invention is lowered, and if it exceeds 80% by weight, the water resistance of the chipping-resistant paint is lowered. This is not preferable. More preferably, it is 60 to 75% by weight.
[0021]
If the amount of vinyl cyanide monomer is less than 5% by weight, the adhesion of the chipping-resistant paint blended with the copolymer latex of the present invention is lowered, and if it exceeds 20% by weight, the water resistance of the chipping-resistant paint is lowered. It is not preferable. More preferably, it is 7 to 17% by weight.
[0022]
If the unsaturated carboxylic acid alkyl ester monomer is less than 5% by weight, the chipping resistance of the chipping-resistant paint blended with the copolymer latex of the present invention is lowered, and if it exceeds 20% by weight, the water resistance of the chipping-resistant paint is reduced. Is unfavorable because it decreases. More preferably, it is 7 to 17% by weight.
[0023]
If the amount of the ethylenically unsaturated carboxylic acid monomer is less than 0.5% by weight, the mechanical stability of the chipping resistant coating compounded with the copolymer latex of the present invention is lowered, and if it exceeds 5% by weight, the viscosity of the latex is decreased. This is not preferable because it becomes high and causes problems in handling the copolymer latex itself. Preferably it is 1-4 weight%.
[0024]
When the unsaturated monomer having a hydroxyalkyl group is less than 0.5% by weight, the repellency of the chipping-resistant paint blended with the copolymer latex of the present invention is deteriorated, and when it exceeds 5% by weight, the viscosity of the latex is increased. This is not preferable because it may cause a problem in handling the copolymer latex itself. Preferably it is 1-4 weight%.
[0025]
In the present invention, when the monomer is subjected to emulsion polymerization, it is preferably emulsion polymerization in the presence of a cyclic unsaturated hydrocarbon having one unsaturated bond in the ring.
Examples of such a compound include cyclopentene, cyclohexene, cycloheptene, 4-methylcyclohexene, 1-methylcyclohexene and the like, and the use of cyclohexene is particularly preferable.
[0026]
Moreover, there is no restriction | limiting in particular about the usage-amount of this unsaturated hydrocarbon, However, It is 0.1-50 weight part with respect to the said monomer total 100 weight part, Preferably it is 0.5-30 weight part, Furthermore, Preferably it is 6-25 weight part.
[0027]
The addition method of various components in the present invention is not particularly limited, and any of a batch addition method, a divided addition method, and a continuous addition method can be adopted. Also, the emulsion polymerization method is not particularly limited, and any one-stage polymerization, two-stage polymerization, multistage polymerization or the like can be employed. Furthermore, in emulsion polymerization, conventional chain transfer agents, emulsifiers, polymerization initiators, electrolytes, polymerization accelerators, chelating agents and the like can be used.
[0028]
In the present invention, a chain transfer agent can be used as necessary. Such chain transfer agents include alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-stearyl mercaptan, dimethylxanthogen disulfide, diisopropylxanthogen. Xanthogen compounds such as disulfide, α-methylstyrene dimer, terpinolene, thiuram compounds such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetramethylthiuram monosulfide, 2,6-di-t-butyl-4-methylphenol , Phenolic compounds such as styrenated phenol, allyl compounds such as allyl alcohol, halogenated charcoal such as dichloromethane, dibromomethane, carbon tetrabromide Hydrogen compounds, α-benzyloxystyrene, α-benzyloxyacrylonitrile, vinyl ethers such as α-benzyloxyacrylamide, triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, 2-ethylhexylthioglycolate 1 type, or 2 or more types can be used.
[0029]
There is no restriction | limiting about the usage-amount of these chain transfer agents, Although it can adjust suitably according to the performance calculated | required by copolymer latex, Preferably it is 0.05-10 weight with respect to 100 weight part of monomer mixtures. Part.
[0030]
Emulsifiers include higher alcohol sulfates, alkylbenzene sulfonates, aliphatic sulfonates, aliphatic carboxylates, anionic surfactants such as nonionic surfactant sulfates, or polyethylene glycol alkyl esters. Type, alkylphenyl ether type, alkyl ether type and other nonionic surfactants are used alone or in combination of two or more.
[0031]
As the initiator, water-soluble initiators such as potassium persulfate, ammonium persulfate, and sodium persulfate, redox initiators, and oil-soluble initiators such as benzoyl peroxide can be used.
[0032]
The copolymer tex of the present invention is blended and used as a vehicle for chipping-resistant paints, and there are no restrictions on components other than latex of the chipping-resistant paints, but generally talc, calcium carbonate, diatomaceous earth, mica , Fillers such as kaolin, barium sulfate, graphite, alumina, iron oxide, titanium oxide, silica, glass balloon, silica balloon, carbon black, organic pigment, chromic acid metal salt, phosphoric acid metal salt, metaboric acid metal salt, etc. It can be used in combination with a pigment, a crosslinking agent, a vulcanizing agent, a dispersing agent, a thickening agent, an organic solvent, an anti-aging agent, an ultraviolet absorber, an antistatic agent, a heat-sensitive gelling agent and the like.
[0033]
Further, there is no limitation on the method of coating the surface of the metal product with the chipping resistant coating containing the copolymer latex of the present invention as a vehicle. Generally, airless coating, air spray coating, brush coating method, roll coating method, It is possible to paint on the surface of metal products using a spatula coating method.
[0034]
【Example】
Hereinafter, in order to clearly show the excellent effects of the present invention, examples and comparative examples will be given to describe the present invention more specifically. The present invention is not limited at all by these examples unless it exceeds the gist. In addition, the part and% shown in an Example and a comparative example are based on a weight unless there is particular notice.
[0035]
Production of copolymer latex In a 10 liter autoclave, 100 parts of water, 3 parts of α-methylstyrene dimer, 0.3 part of sodium dodecylbenzenesulfonate, 0.3 part of t-dodecyl mercaptan, potassium persulfate 1.2 parts and 10% of the monomer having the composition shown in Table 1 were charged, and the temperature was raised to 70 ° C. with sufficient stirring, followed by reaction for 1 hour. Furthermore, the polymerization was carried out while continuously adding the remaining monomers for the polymerization time shown in Table 1. Next, after aging at the aging temperature and aging time shown in Table 1, these copolymer latexes were adjusted to pH 8 with an aqueous caustic soda solution, unreacted monomers and the like were removed by steam distillation, A polymer latex (a) was obtained. Moreover, except having changed into the content shown in Table 1, the same operation was performed and the copolymer latex (b)-(f) was manufactured.
[0036]
Examples 1-3, Comparative Examples 1-3
To 100 parts of copolymer latex (a), 120 parts of calcium carbonate, 5 parts of carbon black, 5 parts of barium metaborate, 5 parts by weight of dispersant and 150 parts by weight of water were added and mixed in a laboratory mixer. The chipping-resistant water-based paint of Example 1 was used. The obtained chipping-resistant water-based paint was airlessly coated on a turn sheet plate plated with lead-tin so that the dry film thickness was 300 μm, set at room temperature for 10 minutes, then at 80 ° C. for 10 minutes, 120 ° C. And dried for 20 minutes to obtain an evaluation sample. Similarly, samples of Examples 2 to 3 were prepared using the copolymer latexes (b) to (c) described in Table 1. Furthermore, the sample of Comparative Examples 1-3 was created using the copolymer latex (d)-(f) described in Table 1 like the Example. In addition, the said number of parts represents solid content. The samples of Examples 1 to 3 and Comparative Examples 1 to 3 were evaluated by the following method.
[0037]
Repelling property The coating state was visually observed and evaluated. In both Examples and Comparative Examples, one point of paint was applied to 100 turn sheet plates of 10 cm × 15 cm, visually observed, and evaluated according to the following criteria.
◎: No repelling ○: Three or fewer turn sheets with repellency △: Six or fewer turn sheets with cissing ×: Seven or more turn sheets with cissing [0038]
The adhesion was evaluated according to the cross-cut tape method of JIS K5400. That is, using a knife, incisions of 2 mm intervals in length and breadth that are perpendicular to each other and reach the steel plate base are made at the center of the coating film, and then the pressure-sensitive adhesive tape is pressure-bonded to the cutting section and immediately peeled off. The degree of peeling was evaluated according to the following criteria.
◎: No peeling at all ○: The area of the peeling defect is within 5% Δ: The area of the peeling defect is 5-15%
×: The area of the peeling defect is 15% or more.
Chipping resistance The sample was fixed at an angle of 60 degrees with respect to the horizontal plane, and the nut (M-4) was dropped continuously from a height of 2 m on the painted surface, and the base material of the turn sheet steel plate was exposed. The total weight of the nut dropped at the time was evaluated according to the following categories.
◎: The total weight of the nut is 50 kg or more. ○: The total weight of the nut is 40 to 50 kg.
Δ: Total weight of nut is 30-40 kg
×: The total weight of the nut is 30 kg or less.
The state after immersion in water at room temperature for 7 days was examined by the method of water resistance JIS K5400.
◎: No abnormality ○: Slight chalking is observed Δ: Coating film is softened and chalking is severe ×: Softening and chalking are markedly peeled off [0041]
[Table 1]

[0042]
【The invention's effect】
As described above, by using the specific copolymer latex in the present invention as a copolymer latex for chipping-resistant water-borne coatings, coating properties such as chipping resistance and adhesion between a base steel sheet and a coating film, water resistance, and the like The balance with the coating workability can be remarkably improved.

Claims (1)

Conjugated diene monomer 60-80% by weight, vinyl cyanide monomer 5-20% by weight, unsaturated carboxylic acid alkyl ester monomer 5-20% by weight, ethylenically unsaturated carboxylic acid monomer 0.5 to 5% by weight of the product, 0.5 to 5% by weight of the unsaturated monomer having a hydroxyalkyl group and 0 to 29% by weight of other vinyl monomers copolymerizable therewith, 6 to 25 parts by weight of cyclic unsaturated hydrocarbon having one unsaturated bond in the ring selected from cyclopentene, cyclohexene, cycloheptene, 4-methylcyclohexene and 1-methylcyclohexene with respect to 100 parts by weight of the body A composition for chipping-resistant water-borne coatings comprising a copolymer latex obtained by emulsion polymerization under the following conditions.