JPS63113087A - Composition for thermosetting acrylic paint - Google Patents

Abstract

PURPOSE:To provide a thermosetting acrylic paint containing two specific kinds of acrylic copolymer and a curing agent composed of an amino resin, applicable by spray coating at normal solid concentration and having excellent low- temperature hardenability, water-resistance and weather-resistance. CONSTITUTION:The objective composition can be produced by compounding (A) a mixture produced by mixing (i) an acrylic copolymer containing a polymerizable monomer having glycidyl group, etc., (e.g. alpha,beta-unsaturated carboxylic acid glycidyl ester) and free from polymerizable unsaturated carboxylic acid and (ii) an acrylic copolymer containing a polymerizable unsaturated carboxylic acid and free from a polymerizable monomer having glycidyl group, etc., at a molar ratio of the glycidyl group in the component (i) to the carboxyl group in the component (ii) of 1/9-9/1 and (B) a curing agent composed of an amino resin.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a thermosetting acrylic coating composition, particularly one that can be spray coated with a normal solid content, has low temperature curability,
The present invention relates to a thermosetting acrylic paint composition with good water resistance and weather resistance.

[Prior Art] Conventionally, thermosetting acrylic paint compositions with low temperature curability and storage stability have been known (Japanese Patent Publication No. 47-373
4). This coating composition comprises (1) a polymerizable unsaturated carboxylic acid, (2) a mixture of α,β-unsaturated carboxylic acid glycidyl ester and α,β-unsaturated carboxylic acid hydroxyalkyl ester in a predetermined molar ratio; (3) Compositions containing polymers obtained by polymerizing monomer mixtures such as acrylic esters are known.

[Problem to be Solved by the Invention 1] In the above-mentioned conventional composition, when the above-mentioned monomers are copolymerized, the carboxyl group of the unsaturated carboxylic acid and the glycidyl group of the unsaturated glycidyl ester react during the polymerization, A polymer composition with a high viscosity and a relatively wide molecular fi1 distribution is produced. Therefore, this composition is unsuitable for spray coating or crushed N coating that is actually used on a line. In addition, when the molecular weight is adjusted using a polymerization inhibitor such as lauryl mercaptan, it is undesirable because it generates a bad odor and deteriorates weather resistance. Furthermore, increasing the amount of polymerization initiator also causes the opening of low molecules, which also reduces weather resistance.

The present invention overcomes the above-mentioned drawbacks, and aims to provide a thermosetting acrylic paint composition that can be spray coated with a normal solid content and has good low-temperature curability, water resistance, and weather resistance. do.

[Means for Solving the Problems] The thermosetting acrylic coating composition of the present invention comprises an acrylic copolymer A containing at least a polymerizable monomer having a glycidyl group and no polymerizable unsaturated carboxylic acid; an acrylic copolymer B containing a polyunsaturated carboxylic acid and not containing a polymerizable heptamer having at least a glycidyl group, and a curing agent made of an amino resin; The blending ratio with B is such that the molar ratio of the glycidyl group in the acrylic copolymer A to the carboxyl group in the acrylic copolymer B (glycidyl group/carboxyl group) is 1/9 to 9/1. It is characterized by

The acrylic copolymer A is a copolymer containing at least a polymerizable monomer having a glycidyl group and containing no polymerizable unsaturated carboxylic acid. The polymerizable monomer having at least a glycidyl group may be an α,β-unsaturated carboxylic acid glycidyl ester. Glycidyl acrylate and glycidyl methacrylate are useful as this ester. There is almost no difference in thermosetting properties, stability, etc. between the two, and glycidyl acrylate gives slightly more flexibility to the resulting film. Further, glycidyl methacrylate and glycidyl acrylate may be used in combination or alone.

Examples of the polymerizable unsaturated carboxylic acid include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid. Although these acids were found to have an effect of accelerating curing upon heating, no significant difference in curing accelerating effect was observed between these acids. However, since substances other than acrylic acid and methacrylic acid may cause a decrease in physical properties such as a decrease in gloss of the In coating, it is preferable to use acrylic acid or methacrylic acid except in special cases.

The acrylic copolymer B is a copolymer containing the above-mentioned polymerizable unsaturated carboxylic acid and not containing at least the above-mentioned polymerizable monomer containing the glycidyl group.

Other monomers constituting these copolymers in acrylic copolymer A or acrylic copolymer B include hydroxy group-containing monomers, such as human O-oxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, acrylic Hydroxyethyl methacrylate, etc., styrene, α-methylstyrene, methacrylic acid monomers such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, etc., and acrylic acids Monomers such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, and lauryl acrylate can be used.

In the composition of the present invention, the blending ratio of the acrylic copolymer A and the acrylic copolymer B is such that the glycidyl group in the acrylic copolymer A and the carboxyl group in the acrylic copolymer are The molar ratio (glycidyl group/carboxyl group) is 1/9 to 9/1. If this molar ratio is less than 1/9, the elimination of carboxyl groups will not be sufficient and the effect of improving water resistance will not be observed, which is undesirable. If this value exceeds 9/1, the elimination of carboxyl groups will be This is not preferable because the amount decreases and the curability decreases.

The curing agent is made of an amino resin.

As this amino resin, melamine resin, benzoguanamine resin, urea resin, etc. can be used alone or as a mixture thereof. As this curing agent, alkyl etherified amino formaldehyde tree IF! (For example, butyl etherified methylol melamine, methyl etherified methylol melamine, butyl etherified methylol benzoguanamine, methyl etherified methylol urea, etc.) are preferably used. The mixing ratio of these curing agents is usually 10:90 to 40:60 by weight with respect to the copolymer A used in the present invention, and the copolymer composition or copolymer A and The optimum amount varies depending on the ratio with copolymer B and other factors. This alkyl etherified amino formaldehyde resin is usually used as a solution in butanol, isopropanol, or a butanol-xylene mixture.

The coating composition of the present invention may contain pigments, plasticizers, thickeners, ultraviolet absorbers, and other various additives.

[Effects of the Invention] The coating composition of the present invention comprises an acrylic copolymer A containing at least a polymerizable monomer having a glycidyl group, an acrylic copolymer A containing a polymerizable unsaturated carboxylic acid, and a predetermined curing agent. including. These copolymers A and B are both resins in the range normally used in ordinary synthesis methods (for clear paints and solid paints, the weight average molecular weight (hereinafter MW
That's what it means.

) is 10,000 to 30,000, number average molecular weight (hereinafter Mn
That's what it means. ) is 5000-150oo, MW/Mn is 1.
5-4.0, MW for metallic base paint is 3
0000~70000. Mw/Mn is 1.5 to 5.0)
is obtained. Since these copolymers A and B do not polymerize at least a polymerizable monomer having a glycidyl group and a polymerizable unsaturated carboxylic acid at the 7-mer stage,
There is no possibility that this will polymerize and the polymer composition will have a high viscosity or a wide polymerization degree distribution. Therefore, the present coating composition is suitable for general spray coating and electrostatic coating.

In this case, no valves, no ffi regulators, and no excess polymerization initiator are required. Therefore, in the present composition, disadvantages such as deep R and low molecular weight do not occur.

However, for the purpose of obtaining a high solids resin, a molecular weight regulator and a polymerization initiator can be used, but the amounts used can be kept to the minimum necessary.

This paint composition has a higher solids content compared to conventional paints, has good workability, and has effective ring-opening of glycidyl groups during baking, which improves the properties of the paint film and improves storage. The stability is better than the conventional one.

From the above, this paint composition can increase the application solids content of the paint, provide a resin suitable for paints with a narrow molecular weight distribution, and have good coating suitability for spray painting, electrostatic painting, etc. Since the reaction efficiency during curing is high, weather resistance, water resistance, and various physical properties can be improved.

In particular, when this composition is baked at a low temperature of about 120° C., it exhibits better performance than when conventional compositions are baked at the same temperature.

In addition, when the acrylic copolymer A containing a large amount of glycidyl groups is used in the present coating composition, the carboxyl groups after baking hardening can be reduced by the reaction between the carboxyl groups and the glycidyl groups. Therefore, this composition can improve water resistance and adhesion to substrates.

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

(Composition of acrylic copolymer A and acrylic copolymer B and their physical properties) Table 1 shows acrylic copolymer A (denoted as A in this table) used in this example, and acrylic copolymer 8 used in this example. The monomer composition (denoted as 8 in this table) and the properties of this copolymer are shown.

In this table, A-1 and A-2 are polymerizable unsaturated carboxylic acids (
Contains no acrylic acid. Similarly, in the acrylic copolymer ThB of 8-1 and B-2, α,β-unsaturated carboxylic acid glycidyl ester (methacrylic acid glycidyl ester)
Does not include GMA)).

Note that C-1 and C-2 are α,β-unsaturated carboxylic acid glycidyl ester and polymerizable unsaturated carboxylic acid 1
This is a conventional copolymer C containing both surface acids. According to this table, copolymer A and copolymer B have a higher M than conventional copolymer C.
Since w is small, the ratio of Mw/Mn is historically small.

As a method for producing these copolymers, the above-mentioned 7-mers are expressed in the proportions indicated (each number indicates part by weight).

), add AlBN double ω portion, and heat at 120°C in “thinner Tulpetz 100J/n-butanol-8/2”.
Synthesized with. The heating residue was 50% by weight.

(Painting conditions) (1) Base paint This base paint is “Acridic 47-712
J (manufactured by Dainippon Ink & Chemicals Co., Ltd.), 31.5 parts by weight (all numbers below indicate parts by weight), "Super Beckamine G-821-60J (Dainippon Ink & Chemicals Co., Ltd.)
Co., Ltd.) 11.25, [Alpaste 713ONJ
(manufactured by Toyo Aluminum Co., Ltd.) 2.5, butyl acetate 27
．． 5, Dorol 27.25 was used.

(2) Clear paint copolymer A and copolymer B, rU-VAN20SE-6
0J (manufactured by Mitsui Toatsu Chemical Industry Co., Ltd.), [Chinupin 3
28J (manufactured by Ciba Geigy Co., Ltd.), rsano l
18-292J (manufactured by Sankyo Pharmaceutical Co., Ltd.) each constitutes a clear paint with a solid content ratio of 70:30:1:1,
As the dilution solvent, "Turupetz 100J" (manufactured by Esso Chemical Co., Ltd.) was used.

(3) Solid paint copolymer A and copolymer B1 rU-VAN208E-
60J (manufactured by Mitsui Toatsu Chemical Industry Co., Ltd.), titanium oxide (rCR-90J (manufactured by 6hara Sangyo Co., Ltd.)), rLJ
-VAN20SEJ (manufactured by Mitsui Toatsu Chemical Industry Co., Ltd.)
, “Tinupin 328J (manufactured by Ciba Geigy Co., Ltd.), r
Sanol 18-292J (manufactured by Sankyo Pharmaceutical Co., Ltd.)
The solid content weight ratio is 42:18:40:0.6:0.
6 was used, and the diluting solvent was "Tsurupets 100".
J (manufactured by Esso Chemical Co., Ltd.)/cellulose acetate 7
/3 (gravity/l ratio) was used.

(Metallic Coating) In this example, each of the copolymers listed in Table 1 was mixed as shown in Table 2 and used as a clear coating. In Example 1, A-1/B-1=30/70 (weight ratio,
The same applies below. ), and in Example 2, A-2/B
-2=40/60. As shown in Table 2, the composition of the clear paint of the comparative example includes C-1, C-2, and B-
Each resin No. 1 or B-2 was used.

The above base paint was applied by air spray painting, and then a clear paint was applied in the same manner while this was wet.
Baked at 40°C for 30 minutes. The performance of each coating film, including appearance, gloss, pencil hardness, adhesion, water resistance, and weather resistance (SWOM) using a weatherometer, was evaluated after drying.

The water resistance and weather resistance were also evaluated after baking at 120°C for 30 minutes. These results are shown in Table 2.

Table 2 also shows the storage stability, solid content heavy chain % during coating, and coating properties such as stringiness of these coating compositions. The storage stability was determined at 40° C. after 30 days. The solid content during coating was measured using a 25 second/N0.4 Ford cup at 20°C.

The coating properties were evaluated using a NO12 Process G Minibell electrostatic coating device (manufactured by Nippon Ransburg Co., Ltd.), and judged based on the presence or absence of stringiness. Gloss was determined by 60°/600 specular reflectance. Adherence was determined by suicide. Water resistance was measured at 4oC for 1000 hours. For weather resistance, conditions of 3000 hours using a sunshine weather meter were used.

(Solid coating) In Example 3, A-1/B- was used as a solid coating.
1-30/70, 4tA-2/B as that of Example 4
-2-40/60 (7) also (7)l['7. :.

Regarding Comparative Examples 5 to 8, the resin composition was C-
1, C-2, B-1, and B-2, and a solid coating composition was prepared in the same manner as in Example 3, except for the copolymer.

Table 3 shows the results of the coating properties of this coating composition, such as solid content weight % and stringiness during coating.

Painted appearance after painting by air spray painting using this paint composition and then heating and curing at 140°C for 30 minutes,
Table 3 shows the performance results for gloss, pencil hardness, adhesion, water resistance, and weather resistance measured by weatherometer (SWOM).As with clear, water resistance and weather resistance are 120.
The evaluation was performed after baking at ℃ for 30 minutes. The solid content during coating and each performance were determined in the same manner as above.

(Evaluation) In Examples 1 to 4, the paintability was excellent even when the solid content concentration at the time of coating was high, while in Comparative Example 1, 2, 5, and 6, the coating with a small solid content concentration had poor performance in terms of paintability. Unfortunately, there are some bends and cracks.

Comparative example 3.4.7 of solid content concentration during coating same as this example
．． In Example 8, the paintability was good, but fading, cracking, or chalking occurred in water resistance and weather resistance, but in Examples 1 to 4, no such defects occurred.

In Examples 1 to 4, the coating, coating appearance, gloss, pencil hardness, adhesion, water resistance, and weather resistance were all good.

Patent applicant Aisin Kako Co., Ltd. agent
Patent Attorney Hirodo Okawa Patent Attorney Akio Maruyama

Claims (2)

[Claims] (1) Acrylic copolymer A containing at least a polymerizable monomer having a glycidyl group and not containing a polymerizable unsaturated carboxylic acid, and acrylic copolymer A containing a polymerizable unsaturated carboxylic acid and not containing a polymerizable monomer having at least a glycidyl group. It contains a polymer B and a curing agent made of an amino resin, and the blending ratio of the acrylic copolymer A and the acrylic copolymer B is such that the glycidyl group in the acrylic copolymer A and the acrylic copolymer are 1. A thermosetting acrylic coating composition characterized in that the molar ratio (glycidyl group/carboxyl group) to the carboxyl group in Product B is 1/9 to 9/1. (2) Polymerizable monomers having glycidyl groups include α, β
-The thermosetting acrylic coating composition according to claim 1, which is an unsaturated carboxylic acid glycidyl ester.