JPH0228269A - Coating composition for freeze-resistant and chipping-resistant treatment - Google Patents

Abstract

PURPOSE:To obtain a chipping-resistant coating composition effective in coating a surface of a metallic article and protecting the article from chipping under cold condition by using a specific styrene-butadiene-acrylate copolymer as a base resin and adding a filler and a pigment to the resin. CONSTITUTION:The objective composition contains (A) a base resin composed of a copolymer of styrene, butadiene and an acrylic monomer, having a glass transition point of <=0 deg.C, containing 5-50 pts.wt. of butadiene per 100 pts.wt. of the base resin and produced in an emulsion system, (B) a filler and (C) a pigment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a chipping-resistant coating composition that coats the surface of a metal product to protect the metal product from chipping in cold weather. The cold-resistant and chipping-resistant coating composition of the present invention includes:
For example, it is used to coat the surface of automobile gasoline tanks.

[Prior Art] Conventionally, chipping-resistant coating compositions have generally used paints in which an acrylic resin emulsion is used as the base mWI and fillers such as talc and calcium carbonate are blended. For example, JP-A No. 62-230868 discloses that a water-dispersible acrylic resin contains 100 parts by weight as a solid content, 10 to 60 parts by weight of a powdery filler, and 1 part by weight of a fibrous filler.
There is disclosed a chipping-resistant coating composition comprising 0 to 100 parts by weight. However, depending on the type of acrylic resin, chipping resistance in cold weather may not be sufficient. Therefore, the above-mentioned JP-A-62-230868 discloses that it is possible to mix and use a butadiene-based rubber latex such as styrene-butadiene rubber latex, acrylonitrile-butadiene rubber latex, etc. in this chipping-resistant coating composition. There is a statement that it is. By mixing the butadiene rubber latex in this manner, flexibility becomes higher and chipping resistance improves. However, the acrylic resin of the base resin and the butadiene rubber have poor compatibility, and the amount of butadiene rubber added to the acrylic resin is limited to a small amount, which limits the improvement in chipping resistance.

Furthermore, it has been discovered that the coating film of the base resin formed by blending the above-mentioned butadiene-based rubber has a problem in that the corrosion resistance of the steel plate is reduced.

[Problems to be Solved by the Invention] As mentioned above, in a coating film formed from a mixed liquid of an acrylic resin emulsion and a butadiene rubber latex, the resin part and the rubber part have poor compatibility, and after drying, The coating film is not a uniform continuous film, and there are defects such as fillers and pigments that are dispersed in the coating film.
Cracks and phase separation are likely to occur, and the adhesive strength with steel plates is insufficient. Therefore, the expected chipping resistance effect could not be obtained, and it is thought that water and the like penetrated into the interior of the coating film, reducing the contact resistance of the steel plate.

In addition, in conventional chipping-resistant coating compositions that use acrylic resin as the base resin, the glass transition temperature of the acrylic resin as the base resin is higher than that of butadiene rubber, resulting in insufficient rubber elasticity at low temperatures. It is also possible that the chipping resistance in cold weather has not been sufficiently improved.

The technical objective of the present invention is to improve chipping resistance in cold weather by changing the structure of the base resin.

[Means for Solving the Problems] The cold-resistant and chipping-resistant coating composition of the present invention is a coating composition containing a base resin, a filler, and a pigment, and the base resin is composed of styrene, butadiene, and acrylic. A copolymer of monomers whose glass transition temperature is 0°C or lower,
The amount of butadiene in 1 part of base resin 100flH is 5 to 50
It is characterized by the fact that the base resin is made of an emulsion type.

The base resin is an emulsion-like copolymer of styrene, butadiene, and acrylic monomer. This copolymer is in the form of an emulsion obtained by, for example, adding an acrylic monomer to styrene-butadiene rubber latex and copolymerizing the mixture.

The reason why this copolymerization is carried out by emulsion polymerization to form a copolymer in the form of an emulsion is to prevent the formation of a homopolymer during copolymerization and to improve the copolymerizability of the obtained copolymer.

Acrylic monomers include acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, lauryl acrylate, and 2-acrylic acid.
- at least hydroxyethyl, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, acrylonitrile, acrylamide, N-methylolacrylamide, methacrylonitrile, glycidyl methacrylate, 2-methoxyethyl acrylate, etc. One type can be used. Further, a crosslinking agent and other copolymerizable components copolymerizable with the above-mentioned hexamer may be added and polymerized.

The method for producing this base resin includes, for example, dropping the above-mentioned mixture of acrylic monomers onto styrene-butadiene rubber latex in the presence of a polymerization initiator and an emulsifier;
Alternatively, it can be easily obtained by adding the above mixture and polymerizing it. Alternatively, a mixture of styrene and acrylic monomer may be added to polybutadiene rubber latex for copolymerization.

It is necessary that this acrylic monomer is bonded to and copolymerized with at least the styrene-butadiene rubber. Therefore, if styrene-butadiene rubber and acrylic resin do not form a copolymer, it means that an emulsion of acrylic resin is simply polymerized in the presence of styrene-butadiene rubber latex, and the dispersion state of both is Although it seems to be better, the coating film is not uniform like when emulsions are mixed together.

Therefore, the chipping resistance in cold weather cannot be improved, and the rust prevention property cannot be improved either.

The amount of butadiene contained in the base resin is 5 to 50 parts. If the amount of butadiene is less than 5 parts by weight, the chipping resistance in cold weather will not be improved, and if it exceeds 50 parts by weight, the adhesion of the coating to the steel plate and rust prevention will decrease, which is undesirable. .

In addition, the suspension of the acrylic material 7 contained in this base resin is as follows:
In order to maintain adhesion to the steel plate, it is preferable that the content is at least 10 parts or more. In particular, it is preferable to include acrylic acid, 2-acrylic acid, droxyethyl, etc. as the acrylic monomer in order to maintain adhesive properties. The amount of styrene is preferably 180 parts by weight or less relative to the amount of butadiene in order to reinforce rubber elasticity.

Further, this base resin needs to have a glass transition temperature of 0° C. or lower in order to form a film that has elasticity in cold weather. If the glass transition temperature is higher than 0° C., the rubber elasticity at low temperatures becomes weak and the chipping resistance at low temperatures decreases, which is not preferable. This glass transition temperature is uniquely determined by the type and composition ratio of monomers constituting the base resin.

As the filler, conventionally used fillers can be used. For example, powdered materials such as talc, calcium carbonate, diatomaceous earth, mica, kaolin, barium sulfate, graphite, alumina, iron oxide, titanium oxide, and silica are used. Other fibrous materials can also be used as fillers.

As pigments, coloring pigments such as carbon black and organic pigments, metal chromates, metal phosphates, metal metaborates, etc. are used.

Furthermore, dispersants, thickeners, organic solvents, etc. can also be added.

In order to coat the surface of a metal product with the cold-resistant and chipping-resistant coating composition of the present invention, it is applied to the surface of the metal product by airless coating or air spray coating.

Thereafter, the coating film is obtained by drying and curing, for example, at a temperature of 80° C. to 120° C. for 10 to 30 minutes.

In addition, if the cold-resistant and chipping-resistant coating composition of the present invention is used, it is not necessary to make the film particularly thick, and even a film thickness of about 70 to 200 μm has sufficient chipping resistance.

[Operations and Effects of the Invention] In the present invention, by using the above-described structure of the base resin, the chipping resistance of the coating film formed by the resulting coating composition in cold weather is improved. In addition, since the base resin is an emulsion-like copolymer, it has good compatibility and has good adhesion to the steel plate to which it is applied, so the coating film that is formed has no coating defects and is more rust-proof than conventional ones. Sexuality further improves.

[Example] The present invention will be explained below with reference to Examples.

(Preparation of base resin) Styrene-butadiene rubber latex copolymerized with 55% by weight of butadiene (solid content 60 parts by weight, particle size 0.1μ
), a mixture of 1110 parts by weight of acrylic, 30 parts by weight of butyl acrylate and 5 parts by weight of 2-hydroxyethyl acrylate was added to 55 parts by weight of polymerization initiator peroxide (potassium persulfate 19) and emulsifier (dodecyl sodium sulfate 2
(J) was added dropwise under a nitrogen stream, and copolymerization was carried out at 75° C. for 3 hours to obtain an emulsion of base tree 11B.

By the same method, styrene containing 50% butadiene was prepared.
201 parts by weight of butadiene rubber latex, 111 parts by weight of acrylic monomer, 11 parts by weight of butyl acrylate, 5 m of 2-hydroxyethyl acrylate.
1 part of the mixture was added and polymerized to obtain a base resin A. In addition, a mixture of acrylic monomers such as 15 parts by weight of acrylic acid, 5 parts by weight of butyl acrylate, and 5 parts by weight of 2-hydroxyethyl acrylate was added to 75 parts by weight of styrene-butadiene rubber latex with a butadiene content of 67%. A base resin C was prepared by polymerization.

The coating films obtained by applying each of these base resin emulsions to a steel plate and drying were uniform and in good condition with no defects observed.

As a comparative example, acrylic resin (acrylic acid 10
Shigemurabe, 55 parts by weight of butyl acrylate, acrylic I! −
2- and 35 parts by weight of droxyethyl), an emulsion of acrylic resin, and styrene-butadiene rubber latex (using Example C with a butadiene content of 67% by weight and a solid content of 60% by weight) H. E, F, and G were mixed in the form of an emulsion in the proportions shown in the table.

(Preparation of coating composition) To the emulsion of these base resins (solid content: 100 parts by weight), 7011 parts of calcium carbonate as additives, 50 parts by weight of talc, 3 parts by weight of carbon black,
A coating composition was prepared by blending 5 parts by weight of barium metaborate, 5 parts by weight of a dispersant, and 150 parts by weight of water.

(Coating film production conditions) A turn sheet plate made of a lead-tin plated steel plate was prepared, and the coating composition obtained above was applied by airless coating, and the coating composition was applied at room temperature for 10 minutes.
After setting for 10 minutes at 80℃, 2 minutes at 120℃
Dry for 0 minutes. In addition, the degree of swelling during drying when the coating was applied to a thick film was investigated, and the coating composition of this example hardly caused any swelling even when the coating was applied to a thickness of 500 μm.

(Cold resistance and chipping resistance test) The test method was to hold a nut (M-6) for 2 m at an angle of 60 degrees to the coating surface of a coated plate with a coating film of 200 μm thick.
Nuts were continuously dropped from a height of 1, and the total number of fallen nuts when the substrate was exposed was evaluated. Note that the atmospheric temperature during the test was -30°C. The results are shown in Table 1.

(Touch resistance) A salt water spray method was used in which 5% salt solution was continuously sprayed at 50° C. onto a steel plate on which a coating film was formed, and the time required for rust to appear on the N-coated plate was examined. The results are shown in Table 1.

(Evaluation results) As shown in Table 1, the chipping resistance at -30°C with a coating film thickness of 200 μm was as follows: Comparative example No. 12 in which latex of styrene-butadiene rubber H and acrylic resin were mixed and blended in emulsion form.
, NO33, No.

In No. 4 and No. 15, the weight was 8 ko and 5 kg, and the base resin of No. 2 was the largest, and as the amount of styrene-butadiene rubber H increased, the chipping resistance decreased.

On the other hand, in the example, chipping resistance was increased to 20% by copolymerizing styrene-butadiene rubber with an acrylic monomer.
kg or more, and the chipping resistance is improved in both cases compared to the comparative example. In particular, in the case of No. 2 of base resin B in which the amount of butadiene is contained in the base resin is 30 weight, the chipping resistance is 30 kg, indicating that it has excellent cold resistance and chipping resistance. .

Regarding corrosion resistance, in the case of Comparative Example No. 1, which was made only of acrylic resin, no rust was observed even after 1000 hours of salt water spray, but in the case of Comparative Example No. 1, Comparative Example No. 2, and No. .

In No. 3, No. 4, and 760 hours, 240 hours, and 120 hours, the number of styrene-butadiene rubber compound layers increased, making it easier for rust to occur.

In the example, N when the content of butadiene is 50%
No. 3 rusted after 760 hours, but No. 1, No. 2, which had a small amount of butadiene, did not rust even after 1000 hours.

Patent applicant: Aisin Kako Co., Ltd. Agent: Patent Attorney Hiroshi Okawa

Claims (1)

[Claims] (1) A coating composition containing a base resin, a filler, and a pigment, the base resin being a copolymer of styrene, butadiene, and an acrylic monomer, and having a glass transition temperature of 0°C or lower. A cold-resistant and chipping-resistant coating composition, characterized in that the amount of butadiene in 100 parts by weight of the base resin is 5 to 50 parts by weight, and the base resin is formed of an emulsion type.