JPS6311946B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for improving the interlayer adhesion between paint films, and particularly relates to a method for improving the adhesion of a two-component urethane paint to a thermosetting resin paint film whose surface has not yet been polished. It is something. Traditionally, two-component urethane paints, such as acrylic urethane paints and polyester urethane paints, have been used for a wide range of purposes because they can be dried at room temperature or forced drying. One of the problems is that the adhesion to the paint film of the thermosetting paint whose surface has not yet been polished is very unstable and insufficient, and to some extent the adhesion to the coating film of the urethane paint is likely to occur in the early stage of curing. However, as curing progresses, the adhesion usually decreases, and in rare cases, it may not even adhere at all from the beginning. For this reason, it can be a major hindrance when repairing defective parts in an industrial-scale painting line for automobiles or home appliances, or small-scale refinishing or marking coats for automobiles, etc. has come,
Therefore, there is a strong need for a method for improving the so-called interlayer adhesion between coating films, which is simple and can provide excellent adhesion. Therefore, the inventors of the present invention have conducted extensive research into ways to improve the interlayer adhesion, particularly the adhesion of two-component urethane paints to unpolished surfaces coated with thermosetting paints. As a result, as a so-called primer solution,
The present invention was completed by discovering that the above-mentioned defects can be completely overcome by simply using a solvent solution of a specific phosphoric acid group-containing compound. That is, the present invention mainly relates to the general formula (HO) _3-o PO(OR ₁ ) _o [] (However, R ₁ in the formula represents an alkyl group of C ₁ to C ₁₈ , and n is 1 or 2. ) Phosphate esters (a-1) represented by (However, R ₂ in the formula represents a hydrogen atom or a C ₁ to C ₁₈ alkyl group.) a-2),
and At least one phosphoric acid group-containing compound (A) selected from the group consisting of an adduct (a-3) of an epoxy compound and a phosphoric acid or an acidic phosphate ester, and this compound (A) can be dissolved. A solution consisting of a solvent (B) is applied onto a thermosetting resin paint film, dried, and then a two-component urethane paint is applied and cured to improve interlayer adhesion between the paint films. This provides a method to do this. Here, the above phosphoric esters (a-
Representative examples of 1) include monoesters such as monomethyl phosphate, monoethyl phosphate, monobutyl phosphate, monooctyl phosphate, or monostearyl phosphate; dimethyl phosphate, diethyl phosphate, dibutyl phosphate, Diesters such as dioctyl phosphate or distearyl phosphate, or any mixture thereof, are prepared by reacting phosphorus pentoxide (P ₂ O ₅ ) with an alcohol, and then reacting this as necessary. It is obtained by hydrolysis. Next, as the phosphoric acid ester group-containing polymer (a-2), for example, a homopolymer or copolymer of a glycidyl group-containing polymerizable monomer is prepared in advance, and then these polymers are Phosphoric acid or the addition of acidic phosphate esters such as monobutyl phosphate, or mono(β-hydroxyethyl (meth)acrylate) acid phosphate or mono(β-hydroxypropyl (meth)acrylate)
Homopolymers or copolymers obtained by (co)polymerizing a polymerizable monomer having a phosphoric acid group such as acid phosphate alone or with a polymerizable monomer having copolymerizability. . In the case of such a copolymer, interlayer adhesion cannot be improved unless the content of phosphate ester groups is at least 1%, preferably 3% or more, in terms of polymerizable monomers. In addition, as the polymerizable monomer having copolymerizability with the above-mentioned phosphoric acid group-containing polymerizable monomer, any known and commonly used polymerizable monomer can be used, but typical examples include styrene, vinyltoluene, etc. Aromatic vinyl compounds such as, (meth)acrylic acid esters, acrylic ester monomers such as (meth)acrylic acid 2-hydroxyalkyl esters,
These include acid monomers such as (meth)acrylic acid and fumaric acid, and specific examples of (meth)acrylic acid esters include methyl (meth)acrylate,
Ethyl (meth)acrylate, propyl (meth)
Acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate or 2-ethylhexyl (meth)acrylate, and (meth)acrylic acid 2-hydroxyalkyl ester Specific examples include β-hydroxyethyl (meth)acrylate, β-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate, as well as “Carduura E” (synthetic fatty acid manufactured by Ciel Chemical Co., Ltd.). glycidyl ester) or ``Chitsonox'' (Chitso Co., Ltd.)
Examples include esterification reaction products of monoepoxy compounds such as alicyclic epoxides and (meth)acrylic acid. Furthermore, as the adduct (a-3) of the above-mentioned epoxy compound and phosphoric acid or acidic phosphoric acid ester, monoepoxy compounds such as propylene oxide and "Cardyura E" (glycidyl ester of synthetic fatty acids manufactured by Schiel Chemical Co., Ltd.) can be used. , diepoxy compounds such as "Epiclon 1050" (diglycidyl ether of bisphenol A manufactured by Dainippon Ink & Chemicals Co., Ltd.), or acrylic copolymers containing monomers having glycidyl groups as an essential component. It is obtained by adding phosphoric acid or an acidic phosphoric acid ester such as monobutyl phosphate to a compound having the following. The solvent (B) component that can dissolve the phosphoric acid group-containing compound (A) component listed above is alcohol-based,
A relatively hydrophilic ketone or ester solvent is selected as the main solvent, and if necessary, a small amount of a poor solvent such as toluene or xylene may be used in combination as a diluting solvent. The solution of the phosphoric acid group-containing compound (A) thus obtained is applied onto the thermosetting resin paint film by spray painting, or by impregnating cloth with the solution and applying it. However, in this case, the solution of Compound A can be applied without polishing the coated film of the thermosetting resin paint. In the past, the adhesion of two-component urethane paint to the thermosetting resin coating layer was extremely poor, so the urethane paint could not be applied until the surface of the coating film had been sufficiently polished. Although this step was indispensable, the method of the present invention has the great advantage of eliminating the need to add such an extra step of polishing. However, this does not mean that the method of the present invention cannot be applied at all to materials that have been subjected to a polishing process, and it goes without saying that the method of the present invention can also be applied to such cases. Next, the present invention will be specifically explained with reference to Examples, and unless otherwise specified, all parts and percentages are based on weight. Reference example 1 Synthesis example of phosphoric acid esters 52 parts of n-butanol was charged into a reaction vessel and 40 parts of
After raising the temperature to ℃, a suspension of 28 parts of phosphorus pentoxide in 20 parts of toluene was gradually added at the same temperature, being careful not to generate heat, and after the addition was completed, the mixture was left at the same temperature until it became transparent. Butyl phosphate was obtained. Hereinafter, this will be abbreviated as phosphoric acid ester (a-1-1). Reference Example 2 Synthesis example of phosphate group-containing polymer 20 parts of styrene, 30 parts of methyl methacrylate, 33 parts of butyl acrylate, 10 parts of β-acid phosphoxyethyl methacrylate, 5 parts of β-hydroxyethyl methacrylate, and 2 parts of methacrylic acid In a mixed solvent consisting of 60 parts of n-butanol and 30 parts of ethyl cellosolve, 100 parts of a monomer mixture consisting of Gardner) Z-Z ₁ copolymer solution was obtained. Hereinafter, this will be abbreviated as polymer (a-2-1). Reference example 3 Synthesis example of phosphoric acid adduct of epoxy compound “Epiclon 1050” (Dainippon Ink Chemical Co., Ltd.)
Diglycidyl ether of bisphenol A)
Dissolve 100 parts in 150 parts of methyl ethyl ketone, 85
After adding 26.5 parts of % phosphoric acid while being careful not to generate heat, the reaction was completed by heating at reflux temperature for 1 hour. Next, after cooling this reaction product, 30 parts of acetone was added to obtain a resin solution with a nonvolatile content of 40.3%. Hereinafter, this will be described as a phosphoric acid adduct (a-3-
It is abbreviated as 1). Examples 1 to 12 and Comparative Examples 1 to 4 The solutions of various phosphoric acid group-containing compounds (A) obtained in Reference Examples 1 to 3 were applied as a primer solution, air-dried, and then a two-component urethane paint was applied. A coating film was obtained. As a comparative example, a case where only a two-component urethane paint was applied without using the above primer solution was also conducted. The experimental results are shown in Table 1.

[Table] The two-component urethane paint in Table 1 is "Acrydik A-809" (acrylic polyol manufactured by Dainippon Ink & Chemicals Co., Ltd.; non-volatile content 50%,
hydroxyl value 20) and “Burnock DN-950” (isocyanate prepolymer made by the same company; NCO 12.5%)
acrylic urethane-based paint consisting of a reaction product with
A polyester urethane paint consisting of a reaction product of 170) and ``Bernok DN-950'' was used.
712 (acrylic resin manufactured by the same company; non-volatile content 50%) and ``Supervetsukamine J-820'' (butylated melamine resin manufactured by the same company; non-volatile content 60%), and PWC is made of titanium oxide. 40%, and a mixture of "Betsukosol EZ-3506-60" (short oil alkyd resin manufactured by the same company; non-volatile content 60%) and "Super Betsucomin J-820". An alkyd resin paint made of titanium oxide with a PWC of 40% was used. The test plates used were unpolished steel plates that had been spray-painted with the above-mentioned thermosetting resin paints on Bonde #144 treated steel plates and baked at 140°C for 30 minutes.

Claims (1)

[Claims] 1 Mainly the general formula (HO) _3-o PO(OR ₁ ) _o [] (However, R ₁ in the formula represents an alkyl group of C ₁ to C ₁₈ , and n is 1 or an integer equal to 2.) Phosphate esters (a-1) represented by (However, R ₂ in the formula represents a hydrogen atom or a C ₁ to C ₁₈ alkyl group.) a-2),
and at least one phosphoric acid group-containing compound (A) selected from the group consisting of an adduct (a-3) of an epoxy compound and a phosphoric acid or an acidic phosphate ester, and capable of dissolving the above compound (A). A solution consisting of a solvent (B) is applied onto a thermosetting resin paint film, and after drying, a two-component urethane paint is applied and cured to improve the interlayer adhesion of the paint film. How to improve.