JPH05255637A - Resin for baking coating - Google Patents

Abstract

PURPOSE:To obtain a resin for a baking coating, capable of intactly maintaining or further improving characteristics of solvent and heat resistance, adhesion, flexibility, etc., of conventional urethane coating films and simultaneously improved in surface hardness of the film, toxicity, stability to standing and miscibility with a pigment as the coating. CONSTITUTION:The objective resin for a baking coating comprises a polymer having carbon-carbon bond as a main chain containing masked isocyanate group and hydrolyzable silane group in the side chain. This resin contains the masked isocyanate group in an amount of >=0.5wt.% as isocyanate group based on the total amount of the polymer and the hydrolyzable silane group in an amount of 0.4-7.5wt.% as silicon atom based on the total amount of the polymer. The glass transition temperature of this resin is 0-110 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin for baking coating which has excellent surface hardness, workability (flexibility), solvent resistance, weather resistance, stain resistance and the like, and which has suppressed toxicity due to an isocyanate monomer. Is.

[0002]

2. Description of the Related Art As a coating resin, it has been attempted to improve the physical properties such as the adhesiveness of a coating film by adding an isocyanate group to the side chain of the resin. The technique related to masking is a well-known fact.

A copolymer containing an isocyanate group and a hydrolyzable silane group and a method for producing the same are described in JP-A-63-30512, and a copolymer containing an isocyanate group and a hydrolyzable silane group is a one-component curing type. There is a proposal in Japanese Patent Publication No. 3-23581 for use as a paint.

However, the coating films obtained from these copolymers show improvements in solvent resistance, heat resistance, hardness, etc., as compared with conventional coating films, but the surface hardness, leaving stability, resin concentration, Further improvement is required in terms of compatibility with pigments and toxicity.

For example, a copolymer obtained from an isocyanate group-containing monomer and a hydrolyzable silane group-containing monomer has a problem of leaving stability due to moisture in the air or the like. Further, since this copolymer contains an active isocyanate group, it is restricted by miscibility with a pigment, molecular weight of the copolymer and resin concentration. Furthermore, there are many problems such as the toxicity of the isocyanate group.

[0006]

DISCLOSURE OF THE INVENTION The present invention is directed to a solvent-resistant, heat-resistant, adhesiveness, flexibility, coating film of a polymer coating film containing an isocyanate group and a hydrolyzable silane group as a base polymer of a coating material. Resin for baking paint that can maintain or further improve excellent properties such as hardness, and improve the surface hardness, flexibility, and toxicity of paints, leaving stability, and miscibility with pigments of conventional polymer coatings. For the development of.

[0007]

The present invention relates to a polymer having a main chain of a carbon-carbon bond containing a side chain-masked isocyanate group and a hydrolyzable silane group, and the isocyanate is based on the total amount of the polymer. By developing a resin for a baking coating, which contains 0.5% by weight or more as a group, 0.4 to 7.5% by weight as a silicon atom, and has a glass transition temperature of 0 to 110 ° C. The above objective was achieved.

Further, using the resin, surface hardness, solvent resistance,
We have developed a baking paint with low flexibility and toxicity.

The resin for baking coating of the present invention is a copolymer of a masked unsaturated isocyanate compound containing an isocyanate group and a polymerizable silane compound having a hydrolyzable silane group, and as a main chain component. Is further formed by copolymerizing vinyl monomers.

Specific examples of the unsaturated isocyanate compound containing an isocyanate group used in the copolymer of the present invention include isocyanate ethyl acrylate, isocyanate ethyl methacrylate, isocyanate propyl acrylate, and isocyanate propyl methacrylate. Examples of such derivatives include isocyanate ethyl methacrylate.

As the masking agent for the unsaturated isocyanate compound, those generally used can be used. Typical examples include ethanol, ε-caprolactam, methyl ethyl ketoxime, etc., but the masking agent used may be changed depending on the baking temperature. Methyl ethyl ketoxime is the masking efficiency,
Most preferable including practical baking temperature.

First, the polymerizable silane compound having a hydrolyzable silane group used in the present invention has a general formula R-Si.
(R ′) _a compound represented by X ₃ -a (provided that R is an unsaturated group having a radical-polymerizable double bond, R ′ is a carbon number of 1 to 1)
10 hydrocarbon groups, X; hydrolyzable groups such as alkoxy, aminooxy and acyloxy groups; a; 0, 1 or 2. ), And specific examples thereof include vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, and the like.

Further, as the vinyl-based monomer used as the main chain component, any monomer can be generally used as the vinyl-based monomer of the present invention so long as it is a radically polymerizable monomer. Vinyl esters such as vinyl propionate and vinyl versatate; methyl (meth) acrylate, butyl (meth) acrylate,
(Meth) acrylic acid esters such as 2-ethylhexyl (meth) acrylate and bornyl (meth) acrylate; and aromatic vinyls such as styrene and p-methylstyrene; acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid Etc. are particularly effective, but vinyl ethers such as methyl vinyl ether; halogen-containing vinyl compounds such as vinylidene chloride, vinyl chloride and vinylidene fluoride; olefins such as ethylene; α, β-ethylenically unsaturated acids Examples thereof include maleic acid, itaconic acid, acrylic acid, methacrylic acid, and the like.

The baking coating resin of the present invention is obtained by copolymerizing such monomers by a conventional method.
At the time of this polymerization, it is not necessary to take it out as a resin, and it is convenient to carry out solution polymerization using a solvent for forming a paint.

The solvent used for the baking paint is toluene,
Aromatic hydrocarbons such as xylene, esters such as ethyl acetate and butyl acetate, glycol ether esters containing no hydroxy group such as 1,4-dioxane and 2-methoxyethyl acetate, 1,1,1-trichloroethane A chlorine-containing solvent such as trichlorethylene can be used.

The obtained resin has a glass transition temperature of 0.
The amount of the functional group in the resin is 0.5% by weight or more as an isocyanate group, and the hydrolyzable silane group (based on Si atom) is 0.4 to 7.5.
Those within the range of weight% are effective.

When the content of the isocyanate group in the resin does not reach 0.5% by weight, or when the content of silicon atom in the hydrolyzable silane group does not reach 0.4% by weight, the crosslinking effect is obtained. Is insufficient, and performances such as adhesion to the base material and solvent resistance will not be exhibited. Further, even if the content of the silicon atom exceeds 7.5% by weight, the performance is not improved, and it is merely expensive and economically disadvantageous.

The glass transition temperature affects the surface hardness and flexibility of the coating film, and the glass transition temperature is 0 ° C.
The surface hardness is low for resins that do not reach
Flexibility becomes insufficient for resins with a temperature of ℃ or above.

Of course, the unsaturated isocyanate compound used must be masked with a masking agent.

The resin for baking coating thus obtained is masked with a highly active isocyanate group-containing compound in advance with a masking agent to suppress the activity of the isocyanate group, and a masking isocyanate group-containing monomer component and It contains a monomer component having a hydrolyzable silane group and has a number average molecular weight of 10,000 to
It is as large as 50,000 (M _W / M _N = 2.0 to 3.5) and the resin concentration is 50% or more, so that a high concentration resin composition can be stably obtained.

A pigment is added to such a resin for baking paint to obtain a baking paint, and in order to further enhance the crosslinking effect of the unsaturated isocyanate compound, additives of diamines and diols are used in this paint. Is preferred.

Examples of the diamines used include aliphatic diamines such as ethylenediamine, propylenediamine and hexamethylenediamine, and aromatic diamines such as O-phenylenediamine, m-phenylenediamine and p-phenylenediamine.

The diols to be used are aliphatic diols such as ethylene glycol, propylene glycol, 1,6-hexanediol, 1,8-octanediol, sylopentane-1,2-diol, cyclohexane-1, 2-diol, cyclohexane-1,4
There are aromatic diols such as diols.

The amount of addition is 0.5 to 5.
It is about 0% by weight. If the amount is less than 0.5% by weight, the effect is insufficient, and if the amount is more than 5.0% by weight, precipitation of crystals which are considered to be diamines is observed on the coating film surface.

Alcohols as stabilizers of hydrolyzable silane groups, orthoformate esters represented by the general formula HC (OR ₁ ) ₃ (wherein R ₁ is alkyl having ₁ to 16 carbon atoms, aryl, alkyl halide, It is also a preferable method to use a group consisting of one hydrocarbon group such as allyl halide.

The amount of addition is 0.5 to 5.
It is 0% by weight. In particular, it was confirmed that the addition of the orthoformate ester improved the storage stability even when 1% by weight was added, and that the addition of 5% by weight was sufficiently stable even when stored for 6 months.

[0027]

The resin for baking coating of the present invention is a novel resin having an isocyanate group and a hydrolyzable silane group masked on the side chain of the polymer.

In the resin state, the isocyanate group is masked, so that the toxicity is low and the activity is remarkably lowered. Mixing with various pigments, etc., whose mixing has been a problem due to its reactivity. The sex is greatly improved.

In particular, when a coating material containing this resin is applied to an adherend and baked, the masking agent comes off and the activity of the isocyanate group is restored. Therefore, in addition to the adhesiveness peculiar to the carbon-carbon bond (vinyl-based polymer), this coating also adheres to the urethane-based base material or the silicone-based base material whose adhesiveness is a problem for vinyl-based polymers. Demonstrate good adhesion without choosing.

[0030]

The present invention will be described in more detail with reference to the following examples. (Example 1) 1 liter separable kolben equipped with a stirrer, a dropping funnel (500 ml), and a condenser was used to mask 16.9 g of methyl ethyl ketoxime-masked isocyanate ethyl methacrylate, 39.6 g of butyl acrylate, 39 of methyl methacrylate 9.6 g, methacryloxypropyltriethoxysilane 19.8 g,
2.2 g of maleic anhydride and 211.6 g of toluene are charged. The inside of Kolben is replaced with nitrogen gas. 1.16 g of azoisobutyronitrile was added as a catalyst, and the internal temperature was 80 ° C.
Give up. After starting the reaction, pre-reaction is carried out for 30 minutes, and after completion of the pre-reaction, isocyanate ethyl methacrylate 32.7 masked with methyl ethyl ketoxime is used.
g, 76.8 g of butyl acrylate, 76.8 g of methyl methacrylate, 36.6 g of methacryloxypropyltriethoxysilane, 4.6 g of maleic anhydride, 28.2 g of toluene, 2.08 g of azoisobutyronitrile.
It dripped uniformly in time. After the dropping is completed, the dropping funnel is washed with 28.2 g of toluene and placed in Kolben. One and two hours after the completion of dropping the monomer, 0.48 g of azoisobutyronitrile and 14 g of toluene were added to remove unreacted monomer, and the mixture was aged at 80 ° C. for 1 hour, and after cooling, the resin concentration was 55% and the number average was Molecular weight 22,000, M _W / M _N
= 3.5, a resin having a glass transition temperature of 25 ° C was obtained.

Example 2 In Example 1, the use ratio of butyl acrylate and methyl methacrylate was 50:
Polymerization was carried out under the same conditions except that the ratio was changed from 50 to 35:65, the resin concentration was 55%, the number average molecular weight was 18,000, and M _W
/ M _N = 3.0, and a resin having a glass transition temperature of 44 ° C. was obtained.

(Example 3) 5% by weight of hexamethylenediamine was added to the resin solution of Example 2.

Comparative Example 1 Polymerization was carried out under the same conditions as in Example 2 except that methacryloxypropyltriethoxysilane was omitted. 52% concentration, number average molecular weight 11,000
0, M _W / M _N = 3.4, the glass transition temperature of the resin is 35
A resin of ℃ was obtained.

Comparative Example 2 Polymerization was carried out under the same conditions except that the masked isocyanate ethyl methacrylate and methacryloxypropyltriethoxysilane in Example 2 were removed. Resin concentration 44%, number average molecular weight 8,
A resin having 900, M _W / M _N = 2.3 and a glass transition temperature of 30 ° C. was obtained. Examples 1, 2, 3 and Comparative Example 1,
Steel plate JIS G-3303 (S
It was applied to PTE so that the thickness of the coating film after drying was 40 to 50 μm.

The resulting coating film was baked at a temperature of 100 to 250 ° C. The surface hardness of the baked coating film was determined by the pencil hardness according to JIS K-5652. The weight for the measurement was 1 kg. The workability (adhesion) of the adherend was determined by the JIS K-5400 bendability test. The results are shown in Table 1.

[0036]

[Table 1]

Example 4 To 100 g of the resin solution obtained in Example 2, 51 g of titanium (R-820) and 5 parts of toluene were added.
8 g were mixed using a homomixer to obtain a pigment dispersion coating material.

COMPARATIVE EXAMPLE 3 51 g of titanium (R-820) and 5 g of toluene were added to 100 g of the resin solution obtained in Comparative Example 1.
8 g were mixed using a homomixer to obtain a pigment dispersion coating material. The performance of the pigment coating film was measured using the pigment-dispersed paints obtained in Example 4 and Comparative Example 3. 220 ° C for baking conditions
-30 minutes. The results are shown in Table 2. Measurement conditions are JIS
It carried out according to K-5400.

[0039]

[Table 2]

[0040]

The resin for baking paint obtained by the present invention is soluble in various organic solvents, but the baking treatment of the obtained coating film activates the masked isocyanate group, and Cross-linking is performed, resulting in a strong coating film having high hardness and solvent resistance.

Further, since the hydrolyzable silane group used in combination has a property of excellent adhesion to various adherends, by using the resin of the present invention, the surface hardness can be improved by using the resin of the present invention.
A coating film excellent in flexibility, solvent resistance, weather resistance, and stain resistance could be obtained.

Since the copolymer resin using the masked isocyanate monomer is used, it has low toxicity and can be freely mixed with the pigment. Use of the resin of the present invention is useful as a resin for baking paint.

Claims (3)

[Claims] 1. A polymer having a carbon-carbon bond as a main chain, which comprises an isocyanate group and a hydrolyzable silane group masked in a side chain, and is 0.5% by weight as an isocyanate group based on the total amount of the polymer. As described above, a resin for baking coating containing 0.4 to 7.5% by weight of silicon atom and having a glass transition temperature of 0 to 110 ° C. 2. A baking paint containing the paint resin, pigment and solvent according to claim 1, wherein the amount is 0.5 with respect to the resin.
A baking paint characterized by adding to 5.0% by weight of diamines and / or diols. 3. A baking paint containing the resin for paint, a pigment and a solvent according to claim 1, which is 0.5 to 0.5 with respect to the resin.
A baking paint prepared by blending 5.0% by weight of alcohols and / or orthoformate.