JPH01279982A - Coating material for plastic - Google Patents

Abstract

PURPOSE:To obtain the title coating material which has excellent adhesiveness to base material and gives a film having good physical properties by using a graft polymer which is prepared by the macromonomer method and in which the grafting component is a vinyl polymer segment compatible with a plastic to be coated. CONSTITUTION:The title coating material comprises a graft polymer which is prepared by the macromonomer method and in which the grafting component is a vinyl polymer segment compatible with a plastic to be coated. Said graft polymer is made by copolymerizing a macromonomer with another monomer copolymerizable therewith. Examples of a desirable combination of a base plastic with a macromonomer are as follows: a macromonomer in which the polymer skeleton comprises PS for a PS base; a macromonomer comprising a polystearyl methacrylate for a PE base, a PP base, etc. The polymer which constitutes the backbone of said graft polymer may be a common polymer, such as a vinyl polymer or a polyester.

Description

Detailed Description of the Invention (a) Purpose of the Invention [Field of Industrial Application] The present invention relates to a paint suitable for coating plastic surfaces in buildings, automobiles, railway vehicles, aircraft, ships, electrical appliances, etc. It is something.

[Conventional technology and its problems]

With the development of petrochemistry after the war, the use of plastics has spread to various industries, and these plastic products are now being used to protect them, improve their durability, weather resistance, prevent static electricity, give them electrical conductivity, chemical resistance, and solvent resistance. Painting began to be used as a purpose.

Compared to other materials such as metals, wood, and inorganic substances, plastics have strong hydrophobicity and low intermolecular cohesive force.
Conventionally, when painting plastics, there has been a problem that unless a paint that is well suited to the plastic is used, poor adhesion to the base material tends to occur.

In order to solve this problem, conventional measures have been taken such as surface-treating the base material or using a paint made of a resin that is the same type as the plastic base material or has a similar solubility parameter.

However, although the method of surface treatment of the base material is effective for polyolefin, it is not effective for other plastics, such as styrene resins and acrylic resins - for boat fishing. Note that adhesion was insufficient. In addition, when using a paint made of a resin of the same type or with similar solubility parameters to the plastic base material, the types of paint that can be used are limited by adhesion, so it is necessary to weather resistance, surface hardness, flexibility,
There has been a problem in that paints that can exhibit coating film performance such as heat resistance, chemical resistance, water resistance, lubricity, water repellency, oil repellency, etc. cannot be used in some cases.

Therefore, if a paint for plastics that can exhibit the desired coating performance and has good adhesion to plastics were developed, it would be of great industrial value.

(B) Structure of the invention [Means for solving the problem] As a result of intensive studies to solve the above problem, the present inventors have determined that a vinyl polymer segment having good compatibility with the plastic base material is used as a branch component. The present inventors discovered that a paint film made of a graft polymer produced by the macromonomer method can provide a coating film with excellent adhesion due to the anchoring effect of the branch components on the plastic substrate, leading to the completion of the present invention. .

That is, the present invention is a paint for plastics made of a graft polymer produced by the macromonomer method and having as a branch component a vinyl polymer segment that is compatible with the plastic material to be coated.

In addition, the graft polymer made by the macromonomer method is
For example, Japan Adhesive Association Journal, Vol. 17, N009 (1
981), pages 14 to 20, i.e., a high molecular weight monomer having a polymerizable functional group at one end (referred to as a macromonomer in boat fishing) is combined with other copolymerizable monomers. It refers to a graft polymer produced by a method such as copolymerization with a monomer, and is superior in the following points compared to a graft polymer produced by a method other than the macromonomer method.

i) The proportion of non-grafted polymer mixed is small.

ii) The molecular weight of the branch component and its content in the graft polymer are easily controlled.

ij) Branch components and trunk components having various monomer compositions can be freely combined depending on the purpose.

The present invention will be explained in more detail below.

[Graft polymer] As mentioned above, the graft polymer used in the present invention is a graft polymer obtained by a macromonomer method, in which the branch component is a vinyl polymer segment that is compatible with the plastic of the coated material (hereinafter also referred to as the base material). is a polymer,
Such a graft polymer can be produced by copolymerizing a macromonomer described later and another monomer copolymerizable with the macromonomer, and has the following molecular structure:
It has a vinyl polymer segment derived from a macromonomer as a branch component, and a polymer segment whose main component is a unit formed from another monomer copolymerized with the macromonomer as a trunk component.

Examples of the macromonomer used as a raw material for the graft polymer include macromonomers as detailed in the [Macromonomer] section below. It is necessary to select and use a macromonomer consisting of a vinyl polymer with compatibility. The preferred macromonomer is 1, which has the solubility parameter (SP value) of its vinyl polymer backbone.
(edited by Japan Adhesive Association, "Adhesives Handbook" Base w5 No. 5
This is a macromonomer whose SP value is 1 or less compared to the SP value of the plastic material to be coated.

Specifically, preferred combinations of base plastics and macromonomers are as follows: For example, for plastics such as polystyrene and polyphenylene ether, macromonomers with polystyrene as the polymer skeleton are preferable for ABS resins, acrylic resins, and polychloride resins. Macromonomers consisting of acrylonitrile-styrene copolymer or polymethyl methacrylate are used for plastics such as vinyl, and polystearyl methacrylate is used for polyolefin plastics such as polyethylene, polypropylene, and poly-4-methylpentene. The macromonomer is
For plastics such as polyamide, polybutylene terephthalate, polyethylene terephthalate, epoxy resin, polyacetal, etc., macromotumer consisting of methyl methacrylate-methacrylic acid copolymer or methyl methacrylate-hydroxyethyl methacrylate copolymer is suitable, respectively. It is.

On the other hand, the polymer that constitutes the backbone component of the graft polymer is
Any ordinary polymer such as vinyl polymer, polyester, polyamide, polyurethane or polyether may be used.
The type of polymer used as the main component and the monomer composition are determined according to the desired coating film performance, i.e., film formability, flexibility, surface hardness, stain resistance, water resistance, solvent resistance, chemical resistance, etc. , the molecular weight, degree of crosslinking, etc. may be optimized before use.

The composition of the branch component and the trunk component of the graft polymer is preferably in a weight ratio of 1/99 to 80/20,
More preferably, it is 5/95 to 60/40. If the weight composition of the branch components is less than 1%, the polymer will essentially consist of the trunk component alone, and the grafting effect of the vinyl polymer cannot be expected. If the weight composition of the branch components is 80% or more, the molecular weight of the grafted polymer will decrease. The coating film performance is not improved and practical coating performance cannot be obtained.

Graft polymers can express the desired coating performance,
It can be produced by copolymerizing a macromonomer selected to obtain a polymer structure with another copolymerizable monomer using a known polymerization method.

That is, for example, a graft polymer having a vinyl polymer as a backbone component is prepared by combining the radically polymerizable macromonomer shown in the [Macromonomer] section and the radically polymerizable monomer shown below as a specific example with a known polymerization initiator. It can be produced by radical copolymerization using a solution polymerization method, an emulsion polymerization method, or the like.

Examples of the radically polymerizable monomer include vinyl esters of organic acids such as vinyl acetate, styrene, styrene-substituted products, vinyl aromatic compounds such as vinylpyridine and vinylnaphthalene, (meth)acrylic esters, (
N-vinyl compounds such as meth)acrylonitrile, acrolein, N-vinylpyrrolidone and N-vinylcabrolactam, unsaturated acid anhydrides such as maleic anhydride, N-
Examples include N-substituted maleimides such as phenylmaleimide, and preferably styrene, styrene-substituted products, (meth)
Acrylic acid esters and (meth)acrylonitrile are preferred, and methyl methacrylate, styrene, and acrylonitrile are more preferred. These monomers may be used alone or in combination
More than one type can be used in combination.

In addition, the graft polymer having polyester as a main component may be a known dibasic acid compound such as adipic acid, sebacic acid, terephthalic acid or isophthalic acid, or an alkyl ester thereof, ethylene glycol, 1.4-butanediol or 1.6 It can be produced by polycondensation with a known diol compound such as -hexanediol and a condensed macromonomer described below, that is, a macromonomer having two carboxyl groups, hydroxyl groups, or carboxylic acid alkyl ester groups at one end.

Furthermore, a graft polymer having polyurethane as a main component can be prepared by polycondensing a known diisocyanate compound, a diol compound, and a macromonomer having two hydroxyl groups at one end in the presence of a known catalyst. The manufacturing process is finished.

For the purpose of improving the physical properties of the plastic coating film made of the above-mentioned graft polymer, in order to form a crosslinked structure in the coating film, for example, hydroxyl groups,
A reactive group such as a carboxyl group, an amino group, an isocyanate group or an alkoxysilyl group may be introduced.

The paint for plastics of the present invention has the above-mentioned graft polymer as an essential component, and can be obtained by blending other resin components, solvents, fillers, pigments, reinforcing fibers, additives, etc. as desired, and can be used as a lacquer paint, non-aqueous paint, etc. It can be used as a spray paint or emulsion paint. When used as a thermosetting, photocuring, or moisture-curing coating, various curing agents may be used in combination.

[Macromonomer]

The macromonomer in the present invention has a number average molecular weight of 10
00 to 20,000 as a polymer skeleton, and is a macromonomer having a polymerizable functional group at one end of the vinyl polymer molecule.

Examples of the above-mentioned polymerizable functional groups include radically polymerizable groups such as (meth)acryloyloxy, styryl, vinyl, and allyl groups; polycondensable or Examples include polyaddition groups and ring-opening polymerizable groups such as glycidyl groups.

Vinyl polymerizable monomers that form vinyl polymers that serve as polymer skeletons in macromonomers include vinyl esters of organic acids such as vinyl acetate, styrene, styrene-substituted products, and vinyl aromatic compounds such as vinylpyridine and vinylnaphthalene. , (meth)acrylic acid ester, (
N-vinyl compounds such as meth)acrylonitrile, acrolein, N-vinylpyrrolidone and N-vinylcaprolactam, unsaturated acid anhydrides such as maleic anhydride, N-
N-substituted maleimides such as phenylmaleimide and the like can be used. Suitably styrene, styrene substituted products, (meth)
Acrylic acid esters and (meth)acrylonitrile are used, and more preferably methyl methacrylate, styrene, and acrylonitrile are used.

These monomers can be used alone or in combination of two or more types as a copolymer.

A more preferable molecular weight of the macromonomer is 2,000 to 15,000 in terms of number average molecular weight. Number average molecular weight is 200
If it is less than 0, the physical properties of the macromonomer used as a raw material are difficult to be reflected in the physical properties of the graft polymer;
When it exceeds 0, the polymerizability decreases, which tends to cause problems such as phase separation of the reaction system during production of the graft polymer.

Note that the number average molecular weight of the macromonomer is a polystyrene equivalent molecular weight determined by gel permeation chromatography.

Next, a method for producing the macromonomer will be explained.

The macromonomer can be produced by a known production method, and typical methods include the following method.

i) In the presence of a radical chain transfer agent having a polycondensation or polyaddition functional group, the vinyl polymerizable monomer is transferred into a radical chain transfer agent in the presence of a radical chain transfer agent having a reactive functional group. After polymerizing to obtain a polymer having a reactive functional group at one end, a compound having both a group that reacts with the functional group and a radically polymerizable group is reacted to form a radically polymerizable group at one end. A method for obtaining a macromonomer having

Examples of the radical chain transfer agent used in the method i) above include thiomalic acid, dialkyl ester of thiomalic acid, thioglycerin, and the like. The alkyl group of the dialkyl ester of thiomalic acid has 10 carbon atoms.
The following alkyl groups are preferred, alkyl groups having 4 or less carbon atoms are more preferred, and a methyl group is particularly preferred. If the number of carbon atoms in the alkyl group exceeds 10, it is not preferable because the high-boiling alcohol component tends to remain in the graft polymer even after the polycondensation reaction is completed.

In addition, examples of the radical chain transfer agent having a reactive functional group used in the method ii) include thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, 2-mercaptoethanol, etc. When a vinyl polymerizable monomer is radically polymerized in the presence of a chain transfer agent, a polymer having a carboxyl group or a hydroxyl group at one end of the molecule is obtained. Further, as compounds for reacting with the obtained polymer to introduce a radical polymerizable group to the terminal of the polymer, glycidyl (meth)acrylate, allyl glycidyl ether,
Examples include isocyanate ethyl (meth)acrylate. By reacting a terminal carboxyl group polymer with a glycidyl group-containing compound and a terminal hydroxyl group polymer with an isocyanate group-containing compound, a polymer having a radically polymerizable vinyl group at the terminal end can be obtained.

The polymerization of the vinyl polymerizable monomer in methods i) and ii) can be carried out by a polymerization method such as solution polymerization, bulk polymerization, suspension polymerization or emulsion polymerization under the polymerization conditions adopted in -i. can.

[Covered material]

Plastics to be coated with the plastic paint of the present invention include polymethyl methacrylate, polystyrene, acrylonitrile-styrene copolymer resin, A
Styrenic graft copolymer resins including BS resins, polyvinyl chloride, polyethylene, polypropylene,
Examples include poly-4-methylpentene, polyamide, polybutylene terephthalate, polyethylene terephthalate, polyacetal, polyphenylene oxide, polyphenylene sulfide, polyimide, polyurethane resin, phenol resin, melanin resin, urea resin, epoxy resin, unsaturated polyester resin, and the like.

Preferably, polymethyl methacrylate, ABS resin, polystyrene, polyphenylene oxide, polyvinyl chloride,
Examples include polypropylene.

(C) Effects of the Invention The plastic paint of the present invention has significantly superior adhesion to substrates compared to conventional plastic paints, and has good other coating film properties, so it can be used industrially. Useful.

[Examples and comparative examples]

Hereinafter, the present invention will be explained in more detail by showing Examples and Comparative Examples.

The physical properties of the coating films in Examples and Comparative Examples were evaluated by the following method.

a) Adhesion (survival rate of cross-cut test) Evaluation was made by making a cross-cut of 2 m + a square with a knife and peeling off the cross-cut with cellophane tape.

The results were expressed as residual rate in %.

b) Surface hardness Measured by hardness according to KIS K5400.

Examples 1 to 4 A glass flask equipped with a stirrer, a condenser, a nitrogen introduction tube, and a dropping funnel was charged with 100 parts by weight (hereinafter simply referred to as "parts") of toluene, and degassed by bubbling nitrogen. Next, a solution consisting of monomers and macromonomers having the composition shown in Table 1, 0.5 parts of azobisbutyronitrile, and 50 parts of toluene was placed in a dropping funnel, and the temperature was adjusted to 75°C to 80°C while bubbling with nitrogen. 3.
The mixture was added dropwise over a period of time to effect polymerization. Thereafter, 0.5 part of azobisbutyronitrile was added, and the mixture was further heated at the same temperature for 4 hours to complete the polymerization. 20 parts of toluene and 30 parts of the solvent shown in Table 1 were added to the obtained graft polymer solution to obtain a coating solution with a solid content concentration of 33%. The solution was applied to the plastic substrates shown in Table 1 using a bar coater, and dried with hot air at 60°C for 1 hour to obtain a transparent coating film with a thickness of 30 to 40 microns.

Table 1 shows the results of evaluating the surface hardness and adhesion of the coating film.

Comparative Example 1 After copolymerizing a monomer mixture having the composition shown in Table 1 without using a macromonomer to produce a polymer to be used as a coating vehicle, an organic solvent solution thereof was prepared, thereby forming The physical properties of the coated film were evaluated and the results are shown in Table 1.

Examples 5-6 75 parts of methyl ethyl ketone was charged as a solvent into a glass flask equipped with a stirrer, a condenser, a nitrogen introduction tube, and a dropping funnel, and then 75 parts of methyl ethyl ketone was charged as a solvent, and then 75 parts of methyl ethyl ketone was charged as a solvent, and then 75 parts of methyl ethyl ketone was charged as a solvent. 6) 10 parts (4, On+eq), polyester diol (Kuraray ■Kurapol P-2010 molecular weight 2
000) and 3.2 parts (71.1 meq) of 1,4-butanediol were charged.

Also, add 1 liter of hexamethylene diisocyanate to the dropping funnel.
A mixed solution of 2.6 parts (149.8 meq), 0.1 part of dibutyltin dilaurate, and 75 parts of methyl ethyl ketone was added.

While stirring at room temperature, the contents of the dropping funnel were added dropwise, and the flask was gradually heated to bring the temperature of the internal liquid to 80° C., and the reaction was allowed to proceed for 6 hours. The reaction was carried out in a gentle nitrogen stream. To the obtained polymer solution, 20 parts of methyl ethyl ketone and 30 parts of additional solvent shown in Table 2 were added to obtain a coating solution with a concentration of 33%.

This was applied to the plastic substrates shown in Table 2 using a bar coater, and dried with hot air at 60°C for 1 hour to obtain a transparent coating film with a thickness of 30 to 40 microns.

Table 2 shows the evaluation results of the physical properties of the coating film.

Claims (1)

[Claims] 1. A paint for plastics made of a graft polymer produced by the macromonomer method, whose branch component is a vinyl polymer segment that is compatible with the plastic material to be coated.