JPH0689292B2 - Paint for plastics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a coating material for plastics containing a tertiary alcohol having a ketone group or an ester group as a solvent.

[Conventional technology]

In recent years, plastics have been increasingly used in various fields such as automobiles, home appliances, and OA equipment. Most of these plastics are also painted and used.

However, there are two problems when painting on plastic. First, since plastics generally have poor heat resistance, they cannot be dried or cured at high temperatures. The other is that many plastics are attacked by the solvents commonly used for paints.

For such plastic coating, a lacquer type coating that does not require heat curing, a solventless type coating that can be cured at room temperature, or a coating using a special solvent is used.

However, these coating materials have drawbacks such as durability such as heat resistance and solvent resistance and poor adhesion to an object to be coated.

Solvents that are unlikely to attack plastic include n-hexane, which has no polarity, and water and alcohol, which have extremely strong polarity. However, a solvent with weak polarity such as n-hexane does not dissolve a general paint resin. On the other hand, water and alcohol have hardly been used in polyurethane paints because they react with isocyanate groups.

[Problems to be solved by the invention]

As a result of intensive research, the present inventors have found that a special alcohol is effective as a solvent that does not attack plastics, hardly reacts with an isocyanate group, and further dissolves a polyurethane paint, and completes the present invention. I arrived.

[Means for solving problems]

The present invention relates to a polyurethane coating comprising an active hydrogen-containing compound and a polyfunctional isocyanate and / or a polyfunctional blocked isocyanate, in which 60% by weight or more of the solvent used comprises a tertiary alcohol having a ketone group or an ester group. It relates to paints for plastics.

It is well known that tertiary alcohols hardly react with isocyanate groups, but general tertiary alcohols such as ter-butanol hardly dissolve polyurethane coating resins.

Common polyurethane coating resins include acrylic polyols, polyester polyols, epoxy polyols, nitrocellulose, etc., but only nitrocellulose is soluble in common tertiary alcohols.

Therefore, even if a tertiary alcohol is used as a part of the solvent, the limit is about 40% by weight, and if it exceeds this,
The resin as described above will not dissolve. Therefore, since it is used as a mixed system with a general solvent, plastics such as polycarbonate and styrene are easily attacked by the solvent, and few of them can be used as solvent-based paints.

But the ketone group Or ester group The tertiary alcohol having ## STR3 ## does not attack plastics that are easily attacked by solvents such as polycarbonate and styrene, and dissolves the coating resin as described above.

Further, it is of course that it hardly reacts with the isocyanate group.

Further, it was also found that such a tertiary alcohol is less likely to react with an isocyanate group than a general tertiary alcohol such as ter-butanol.

Examples of the tertiary alcohol that can be used in the present invention include ethyl-2-hydroxyisobutyrate, 3-hydroxy-3-methyl-2butanone, methyl-2-hydroxyisobutyrate, 4-hydroxy-4-. Methyl-2
-Pentanone (diacetone alcohol) and the like, but of course, other than this, a tertiary alcohol having a ketone group or an ester group is effective.

Further, it goes without saying that a mixed system of these tertiary alcohols and a solvent usually used can also be used.

However, toluene, xylene, ethyl acetate (hereinafter abbreviated as ethyl acetate), butyl acetate (hereinafter abbreviated as acetic acid butyric acid), methyl ethyl ketone (hereinafter abbreviated as MEK), methyl isobutyl ketone (hereinafter abbreviated as MIBK), cellosolve acetate (hereinafter referred to as celloacetate). Abbreviated), isopropanol (hereinafter abbreviated as IPA), etc., the higher the proportion of ordinary solvent, the more often the plastic to be coated is attacked. Therefore, the proportion of the tertiary alcohol used is preferably 60% by weight or more.

Examples of the polyfunctional isocyanate and / or the polyfunctional blocked isocyanate as a curing agent that can be used in the present invention include tolylene diisocyanate (hereinafter abbreviated as TDI), 4,4′-diphenylmethane diisocyanate (hereinafter abbreviated as MDI) and hexa Examples thereof include diisocyanates such as methylene diisocyanate (hereinafter abbreviated as HDI), isophorone diisocyanate, xylylene diisocyanate, and modified polyisocyanates thereof and / or blocked isocyanates thereof.

Further, as long as it has an isocyanate group at the terminal, any substance may be used, and a substance such as a moisture curable resin may be used.

Further, as a blocking agent for obtaining the block polyisocyanate, phenol-based phenol, lactam-based ε-caprolactam, alcohol-based methanol, mercaptan-based butylmethylcaptan, acid amide-based acetanilide, imide-based succinic acid Imide, amine-based diphenylamine, urea-based thiourea, carbamate-based phenyl N-phenylcarbamate, imine-based ethyleneimine, oxime-based acetoxime, methylethylketoxime, sulfite-based sodium bisulfite, activity Examples thereof include methylene-based diethyl malonate and ethyl acetoacetate.

Examples of the active hydrogen-containing compound that can be used in combination with these polyfunctional isocyanates and / or blocked isocyanates include polyester polyols, polyether polyols, acrylic polyols, vinyl chloride vinyl chloride copolymers, epoxy polyols, nitrocellulose, actives. Examples thereof include hydrogen group-containing polyurethane resins, and all resins usually used for polyurethane paints can be used.

Further, in addition to the curing agent, active hydrogen compound, and solvent, addition of a catalyst, an additive, a pigment, and the like causes no problem.

The present invention will be described in more detail below with reference to examples. "Parts and%" in the examples are "parts by weight and% by weight", respectively.

Example 1. Various plastics were soaked in a solvent at room temperature for 30 minutes, and it was examined whether or not the plastics were corroded. The results are shown in Table.1.

Example 2 In No. 1 to No. 16 solvents of Example 1, as a polyurethane-based curing agent, Coronate L (TDI-trimethylolpropane adduct, manufactured by Nippon Polyurethane Industry Co., Ltd.), Millionate
MR (Polymeric MDI, manufactured by Nippon Polyurethane Industry) and Coronate EH (HDI isocyanurate, manufactured by Nippon Polyurethane Industry) were dissolved to a solid content of 50%.

All were dissolved except 2,3-dimethyl-3-pentanol.

Example 3 The reactivity of Coronate HL with tertiary butanol, isopropanol and diacetone alcohol alone in equivalent amounts was examined by measuring the residual NCO content. Table 2
Shown in.

It was found that the reaction rate of the diacetone alcohol and the isocyanate group was slow and there was no problem in practical use.

Example 4 The solubility of various coating resins in alcoholic solvents was investigated. The test was conducted by mixing the resin and the solvent in a weight ratio of 1: 1. The results are shown in Table.3.

Synthesis Example 1 An acrylic polyol having the following composition was synthesized in xylene and diacetone alcohol. The composition and products are shown in Table 4.

Example 5 The acrylic polyol, polyester polyol (Nipporan 800: Nippon Polyurethane Industry polyester hydroxyl value = 290, acid value = 1.5) synthesized in Synthesis Example 1 and nitrocellulose (Asahi Kasei HIG1 / 2) and Coronate EH (Japan Polyurethane Industry) Table 5 shows the physical properties of the coating film in the case of combining the same amount).

The conditions for measuring the physical properties of the coating film are as follows.

(1) Paint composition: Solid content 50%, titanium white PWC = 4
Pigmented to 0% (2) Drying condition: 25 ° C 50% RH (3) Physical properties of coating film: Measured after curing at 25 ° C for 7 days (4) Solvent resistance: 10% absorbent cotton impregnated with MEK After putting it on for a minute, it was removed and the appearance was observed.

(5) ABS plate erosion: The coating composition was applied on the ABS plate and its appearance was observed.

(6) Nitrocellulose: 100 parts of nitrocellulose was mixed with 10 parts of Coronate EH.

Further, the physical properties of the coating film when the methyl ethyl ketoxime block of Coronate-EH (Coronate 2507 manufactured by Nippon Polyurethane Industry Co., Ltd.) and Nippon 800 are combined are shown in Table 5-5.

The paint composition and test conditions were the same as in the other examples,
The curing condition is 130 ° C. × 30 minutes.

Claims (1)

[Claims] 1. A polyurethane coating comprising an active hydrogen-containing compound and a polyfunctional isocyanate and / or a polyfunctional blocked isocyanate, wherein 60% by weight or more of the solvent comprises a tertiary alcohol having a ketone group or an ester group. Characteristic plastic paint.