JP4093745B2 - Copolymer latex for chipping-resistant water-borne coatings - Google Patents

Description

【００４０】
【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、金属下地への密着性、耐冷熱サイクル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, regarding the above-mentioned adhesion, it is necessary for the coating film to stably protect the metal substrate in a repetitive environment of cold and warm, and sufficient cold and heat cycle resistance is required.
[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, adhesion to a metal substrate, water resistance, and cold cycle resistance.
[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 of chipping resistance, adhesion to a metal substrate, water resistance, and cold-heat cycle resistance.
[0008]
[Means for Solving the Problems]
That is, the present invention relates to 20 to 80% by weight of a conjugated diene monomer, 0.5 to 15% by weight of an ethylenically unsaturated carboxylic acid monomer, and other vinyl monomers 5 copolymerizable therewith. ˜79.5% by weight obtained by emulsion polymerization in the presence of 6-24 parts by weight of a cyclic unsaturated hydrocarbon having one unsaturated bond in the ring with respect to 100 parts by weight of the monomer. An object of the present invention is to provide a chipping-resistant water-borne coating composition comprising a copolymer latex having a gel content represented by toluene insolubles of 60 to 100% by weight.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The component constituting the copolymer latex in the present invention is an aliphatic conjugated diene monomer, an ethylenically unsaturated carboxylic acid monomer, and other monomers copolymerizable therewith.
[0010]
Examples of the aliphatic 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. , Substituted linear conjugated pentadienes, substituted and side chain conjugated hexadienes, and the like, and one or more can be used. 1,3-butadiene is particularly preferable.
[0011]
Examples of the ethylenically unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, fumaric acid, itaconic acid, maleic acid and the like, and one or more of them can be used.
[0012]
Other vinyl monomers copolymerizable with these include aromatic vinyl monomers, vinyl cyanide monomers, unsaturated carboxylic acid alkyl ester monomers, and unsaturated carboxylic acid amide monomers. And unsaturated monomers containing a hydroxyalkyl group.
[0013]
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.
[0014]
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.
[0015]
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.
[0016]
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.
[0017]
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.
[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, 20-80 weight% of conjugated diene monomers, 0.5-15 weight% of ethylenically unsaturated carboxylic acid-type monomers, and other vinyl-type monomer copolymerizable with these The body should be 5 to 79.5% by weight.
[0020]
When the amount of the aliphatic conjugated diene monomer is less than 20% by weight, the chipping resistance of the chipping-resistant paint blended with the copolymer latex of the present invention is lowered, and when it exceeds 80% by weight, the water resistance of the chipping-resistant paint is lowered. Therefore, it is not preferable. Preferably it is 30 to 70 weight%, More preferably, it is 50 to 70 weight%.
[0021]
The ethylenically unsaturated carboxylic acid-based monomer has an action of imparting stability to the copolymer latex itself and a paint blended with the copolymer latex, and the total amount of these is 0.5 wt. % Or more is necessary. If the total amount exceeds 15% by weight, the viscosity of the latex becomes high, which may cause problems in handling the copolymer latex itself, which is not preferable. Preferably it is 1-7 weight%, More preferably, it is 1-5 weight%.
[0022]
In the present invention, it is necessary to emulsion-polymerize the above monomer 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.
[0023]
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 100 weight part of said monomers total. If the amount is less than 0.1 part by weight, the effect of the present invention is insufficient. If the amount exceeds 50 parts by weight, the amount of the compound remaining as an unreacted substance also increases relatively, and the energy required for the recovery is greatly increased. Therefore, it is not preferable. Preferably it is 0.5-30 weight part, More preferably, it is 6-24 weight part.
[0024]
The copolymer latex of the present invention preferably has a gel content indicated by its toluene insoluble content within a specific range. The gel content of the copolymer latex is 60 to 100% by weight. If the gel content is less than 60% by weight, the water resistance of the chipping-resistant paint blended with the copolymer latex of the present invention is not preferable. Preferably it is 65 to 98 weight%, More preferably, it is 70 to 95 weight.
[0025]
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.
[0026]
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.
[0027]
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.
[0028]
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.
[0029]
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.
[0030]
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.
[0031]
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.
[0032]
【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.
[0033]
Preparation of copolymer latex In a 10 liter autoclave, 100 parts of water, 0.3 part of sodium dodecylbenzenesulfonate, 1.0 part of potassium persulfate, 0.2 part of t-dodecyl mercaptan and Table 1 10% of the monomer having the composition shown was charged, heated to 65 ° C. with sufficient stirring, and allowed to react 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.
[0034]
Examples 1-3, Comparative Examples 1-3
To 100 parts of copolymer latex (a), 70 parts of calcium carbonate, 50 parts of talc, 3 parts of carbon black, 5 parts of barium metaborate, 5 parts by weight of dispersant, and 150 parts by weight of water were added in a laboratory mixer. By mixing, the chipping-resistant water-based paint of Example 1 was obtained. 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. Moreover, the samples of Examples 1 to 3 and Comparative Examples 1 to 3 were evaluated by the following methods.
[0035]
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 part 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.
A: The total weight of the nut is 50 kg or more. O: 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 ×: Coating film is severely softened and chalked; [0038]
Cooling and heat cycle resistance Each sample was subjected to 60 cycles of a heat cycle test of 60 ° C for 3 hours to -20 ° C for 3 hours, and the heat cycle resistance was evaluated based on the adhesion after the test.
◎: 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.
[Table 1]

[0040]
【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, the balance between chipping resistance, adhesion to a metal substrate, and cold cycle resistance is remarkably improved. It can be done.

Claims (2)

20-80% by weight of conjugated diene monomer, 0.5-15% by weight of ethylenically unsaturated carboxylic acid monomer, and 5-79.5% by weight of other vinyl monomers copolymerizable therewith Is insoluble in toluene obtained by emulsion polymerization in the presence of 6 to 24 parts by weight of a cyclic unsaturated hydrocarbon having one unsaturated bond in the ring with respect to 100 parts by weight of the monomer. A chipping-resistant water-borne coating composition comprising a copolymer latex having a gel content of 60 to 100% by weight. The copolymer latex according to claim 1, wherein the cyclic unsaturated hydrocarbon having one unsaturated bond in the ring is a compound selected from cyclopentene, cyclohexene, cycloheptene, 4-methylcyclohexene, and 1-methylcyclohexene. A composition for chipping-resistant water-borne coatings .