JPH01146965A - Primer composition for fluorocarbon resin paint - Google Patents

Abstract

PURPOSE:To obtain the title composition having an ability to adhere to a metallic base and to a fluorocarbon resin paint film and an ability to form a paint film continuous to a fluorocarbon resin paint film, by mixing a polyol resin with a blocked polyisocyanate compound and a thermoplastic acrylic resin. CONSTITUTION:The title composition comprises a polyol resin (A) of a number- average MW>=900 (e.g., polyphenol polyglycidyl ether), a blocked polyisocyanate compound (B) (e.g., phenol-blocked 2,4- or 2,6-tolylene diisocyanate) and a thermoplastic acrylic resin (C) (e.g., methyl methacrylate homopolymer) as essential components. This composition has an ability to adhere to a metallic base and to a fluorocarbon resin paint film and an ability to form a film continuous to a fluorocarbon resin paint film, and does not injure the excellent mechanical properties and chemical properties of a fluorocarbon resin paint film.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a primer composition that improves the adhesion between a fluororesin paint and a metal substrate.

Originally, fluororesins have excellent hardness, impact resistance, chemical resistance, solvent resistance, and weather resistance, and have extremely desirable properties as coating materials.

In addition, it has unique properties such as low coefficient of friction, non-adhesiveness, and high dielectric constant, so its applications are wide-ranging. However, when used as a coating material for coating metal substrates, since it is itself non-polar, its adhesion to metal substrates is extremely poor.

Primers are generally used to improve the adhesion of paints that have poor adhesion. A fluororesin paint is a dispersion paint in which a polymeric fluororesin with a particle size of 10 g or less (average 0.5 g) is dispersed in a solvent together with a colored pigment.

After coating, the coating film is formed by heating the substrate to a temperature higher than the melting point of the fluororesin. Therefore, primers for fluororesin paints must also be durable against solvents at high temperatures, and primers that are not durable will heat up and flow when the fluororesin paint is baked, making it impossible to form a continuous coating of fluororesin paints. .

The present invention is a primer that has adhesion to metal substrates, adhesion to fluororesin coatings, and ability to form a continuous coating of fluororesin coatings, and does not impair the mechanical and chemical properties of fluororesin coatings. As a result of research aimed at obtaining a composition, a composition containing a polyol resin (A) having a number average molecular weight of 900 or more, a blocked polyisocyanate compound (B), and a thermoplastic acrylic resin (C) as essential components was found. He discovered that this product was an excellent primer for fluororesin paints, and completed his invention.

The polyol resin (A) used in the composition of the present invention is a resin containing a hydroxyl group in the molecule and having a number average molecular weight of 900 or more, preferably 2000 or more, and is obtained, for example, by a condensation reaction of acid and alcohol components. polyester;
A silicone resin-modified polyester obtained by modifying the above polyester resin with an alkyd resin or a silicone resin; obtained by polymerizing a hydroxyl group-containing vinyl monomer as an essential component and further with other radically polymerizable monomers. Examples include isopolymers or copolymers and epoxy resins. Among them, it is preferable to use an epoxy resin because it has excellent adhesion to metal substrates and forms a tough primer film.

As the above-mentioned epoxy resin, conventionally known epoxy resins can be used, and include, for example, polyglycidyl ether of polyphenol which can be produced by reacting polyphenol with epichlorohydrin or methylepichlorohydrin in the presence of an alkali. Typical examples of resins include, for example, trade names such as Epicor 152 and Epicor 154 manufactured by Shell Chemical Co., Ltd.
, Epicote 1001, Epicote 1003, Epicote 1055, Epicote 1004, Epicote 10
07, Epicote 1009, Epicote 101O, Ciba Geigy Araldite 6071, Araldite 6
084, Araldite 6097, Araldite 6099
, Araldite 7004, Ebicuron N-730, Epicuron N-740 manufactured by Dainippon Ink Co., Ltd., and the like. In addition, in addition to the above, epoxy resins that do not contain hydroxyl groups (for example, polyglycidyl ethers of polyphenols such as Epicoat 1002, alicyclic epoxy resins, triglycidyl isocyanurate, and phenolic novolak resins) can be used with fatty acids, benzoic acid, amber, etc. acid, terephthalic acid,
Those added with acids such as dimerized phosphoric acid, or those added with amines such as diethylamine, jetanolamine, and polymethylenediamine can also be used as polyols.

Among these, it is preferable to use polyglycidyl ether of polyphenol because it has excellent adhesion to metal substrates and forms a primer film with excellent chemical resistance, water resistance, and mechanical properties. .

By setting the number average molecular weight of the polyol resin (A) to 900 or more, it is possible to form a primer film that has excellent adhesion to metal substrates and fluororesin coatings, water resistance, mechanical properties, and When high performance is required, by setting the number average molecular weight to 2000 or more, a primer film with even better performance can be formed.

As the blocked polyisocyanate compound (B) used as a crosslinking agent component in the composition of the present invention, a polyisocyanate compound having two or more blocked incyanate groups in one molecule can be used. Polyisocyanates used for this include m- or p-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 2,4- or 2,6-tolylene diisocyanate, and methylcyclohexane2. , 4
(2,6) Aromatic or aliphatic (cycloaliphatic) diisocyanates, such as m- or p-xylylene diisocyanate, 1,3-(incyanate methyl)cyclohexane, hexamethylene diisocyanate, dimer acid diisocyanate, isophorone diisocyanate Diisocyanates and adducts of one or more of these diisocyanates with polyols such as ethylene glycol, propylene glycol, glycerin, trimethylolpropane, and pentaerythritol, and polyisocyanate compounds such as trimers of the above diisocyanate compounds. etc.

Volatile low-molecular active hydrogen compounds are used as blocking agents for polyisocyanates, examples of which include methanol, ethanol/butyl, butanol, hexanol, cyclohexanol, benzyl alcohol, and ethylene glycol monoethyl. ether (hereinafter abbreviated as cellosolve), aliphatic or aromatic monoalcohols such as ethylene glycol monobutyl ether (hereinafter abbreviated as butyl cellosolve), hydroxy tertiary amines such as dimethyl- or diethylaminoethanol, acetoxime, methyl ethyl ketone oxime. Examples include oximes such as acetylacetone, active methylene compounds such as acetoacetate and malonic acid ester, lactams such as ε-caprolactam, and phenol.

The blending ratio of the polyol resin (A) and the blocked polyisocyanate compound (B) is such that the ratio of the number of moles of hydroxyl groups in component (A) to the number of moles of incyanate groups in component CB is such that hydroxyl groups 0.2 to 3 per mole. 0 can be preferably used in the range of 0.5 to 1.5.
If the molar ratio deviates from the above-mentioned range, the mechanical properties, solvent resistance, adhesion to the fluororesin coating film and metal substrate, etc. of the primer film will be deteriorated, which is not preferable.

Thermoplastic acrylic resin (C) used in the composition of the present invention
is a homopolymer of methyl methacrylate or a copolymer obtained by radical polymerization reaction with methyl methacrylate as an essential monomer and other radically polymerizable monomers. As the thermoplastic acrylic resin (C), those produced by conventionally known manufacturing methods, such as solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc., can be used.

Examples of other radically polymerizable monomers used for copolymerization with the above-mentioned methyl methacrylate include methyl acrylate.

Non-functional products such as ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, styrene, vinyltoluene, (meth)acrylonitrile, etc. Polymer monomers can be used.

It is preferable that the thermoplastic acrylic resin (C) does not contain any functional groups in the resin because it forms a primer coating III with excellent adhesion to the fluororesin coating, but the purpose is to improve the strength of the primer coating. It is also possible to use those having functional groups within a range that does not deteriorate the adhesion of the fluororesin coating. Examples of methods for introducing functional groups into the thermoplastic acrylic resin (C) include droxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, (meth)acrylamide, N-methylol (
This can be carried out by copolymerization using a functional group-containing monomer such as meth)acrylamide, N-butoxymethyl(meth)acrylamide, or (meth)acrylic acid.

Further, the thermoplastic acrylic resin (C) contains methyl methacrylate as an essential monomer component, and preferably 50 wt.
More preferably, the content can be 70% by weight or more, and if the content is less than 50% by weight, the adhesion between the primer coating and the fluororesin coating will be poor.

Furthermore, the thermoplastic acrylic resin (C) can have a number average molecular weight of about 30,000 to 150,000, preferably about 40,000 to 100,000. If the molecular weight is less than 30,000, it will cause problems during baking of the fluororesin paint. , the organic solvent in the paint dissolves the primer film and makes it easier to flow, improving smoothness and
A fluororesin coating film with excellent cosmetic properties cannot be obtained, and on the other hand, if the molecular weight is greater than 150,000, the compatibility with the resin (A) and the polyisocyanate compound (C) component will decrease.
This is not preferred since the components may settle and separate in the container, resulting in a primer composition with poor solution stability, or a primer film with poor smoothness, mechanical properties, and adhesion to fluororesin coatings. do not have.

The blending ratio of the thermoplastic acrylic resin (C) is the proportion of the polyol resin (A) and the polyincyanate compound (C).
) can be used in a range of 5 to 100 parts by weight based on a total of 100 parts by weight. If the blending ratio is less than 5 parts by weight, a primer film with excellent adhesion to the fluororesin coating will not be formed, while if the blending ratio is more than 100 parts by weight, the solvent resistance of the primer film will be poor and As a result, the primer film tends to dissolve and flow during baking of the fluororesin paint, making it impossible to form a fluororesin paint film with excellent smoothness and cosmetic properties.

Coloring pigments such as titanium oxide, iron oxide, and carbon, extender pigments such as calcium carbonate, barium sulfate, silica, and clay, and antirust pigments such as strontium chromate, zinc chromate, and calcium chromate are added to the composition of the present invention to further mechanically improve the composition. Strength, corrosion resistance, and adhesion can be improved, and curability can be further improved by adding metal ions, organometallic compounds, dissociation catalysts for blocked isocyanates such as tertiary amines, and the like.

The composition of the present invention is applied to a metal substrate (iron, aluminum, etc.).
A primer film for use in fluororesin paints can be obtained by applying a coating by spray coating, dipping, dipping, electrostatic coating, roll coater coating, or the like and then heating. The coating film thickness is 30w or less in dry film thickness, especially 1 to 1
Baking of the coating, preferably in the range of 5 liters, is achieved by heating the substrate to a peak temperature of 200-250°C, and the baking temperature can be further lowered using the dissociation catalysts described above. By painting and baking a fluororesin paint on the thus obtained brimer, a fluororesin coating film with excellent adhesion to metal substrates and coating film appearance can be obtained.

The reason why the composition of the present invention exhibits an excellent effect as a brimer composition for fluororesin paints is not clear, but is presumed to be as follows. In other words, the primer coating that is applied onto the surface of the metal substrate and further baked and cured has a cured coating layer with a high polyol resin component as the lower layer (on the surface side of the metal substrate) and a thermoplastic layer as the upper layer (on the side where the fluororesin paint is applied). A thermoplastic film layer containing a large amount of acrylic resin is formed. When a fluororesin paint is applied onto this thermoplastic primer coating layer and baked, as the temperature rises, the fluororesin, which is the dispersigon particles in the paint, swells and dissolves in the organic solvent, and begins to flow. At this stage, compatibility and fusion occur between the fluid fluororesin paint and the thermoplasticized brimer coating layer, and as a result, it is thought that the adhesion of both films improves. Furthermore, in the present invention, the polyol resin and polyisocyanate compound used together with the thermoplastic acrylic system have the property of separating into two layers and easily migrating toward the metal surface as described above, and are also susceptible to external factors such as corrosive substances on the metal base material. Since it is a thermosetting composition that has the property of retaining its properties, it can exhibit the effects aimed at by the present invention.

Next, the present invention will be described in more detail by showing examples and comparative examples. Note that "1%" in Examples and Comparative Examples indicates "wt%".

Examples and Comparative Examples Primer compositions of Examples 1 to 9 and Comparative Examples 1 to 7 were obtained by uniformly mixing the components shown in Table 1. The components used here are as shown in (21).

Performance test results A steel plate (100 x 300 x 0.7 mm, 5 pcc) was coated with the primer composition shown in Table 1 using a bar coater #22 to a dry film thickness of 8 l, and was coated at 250°C for 2 hours.
It was baked for minutes (material peak temperature 230°C) to obtain a cured film of the primer. The test results of the obtained primer cured film are shown in Table 1.Next, the components shown in Table 2 were mixed and dispersed on the steel plate coated with this primer and baked, and then the fluororesin paint obtained was coated with a bar coater. #5゜coat to a dry film thickness of 30 l and 240゜O-'C'2
Baked for minutes (material peak temperature 220'C). Table 1 shows the test results of the overall coating film obtained.

In Table 1.

(1st) Formulation: Components (1) to (10) are as follows.

(1) 36% Araldite 6099 solution: Araldite 6099 (molecular weight 4800-8000, hydroxyl equivalent 2)
96 g/eq, (manufactured by IBA-GEIGY) 3
6g of ethylene glycol monoethyl ether acetate
)/MIBK=2/li solution obtained by dissolving in 64 g of a mixed solvent.

(2) 60% AP stable solution: AP stable M (
Phenol block form of TDI, effective NGO = 12%,
A solution obtained by dissolving 60 g of Nippon Polyurethane (manufactured by Nippon Polyurethane) in 40 g of ethylene glycol monoethyl ether acetate.

(3) 60% B87ON solution: Manufactured by Takeda Pharmaceutical Co., Ltd., IP
DI oxime block body dissolution axillary, effective NGO = 12.6
%.

(4) 60% B1370 solution: Manufactured by Huls, IPDI oxime block solution, effective NGO = 8%.

(5) 25% acrylic resin A solution: number average molecular weight 40.
000 methyl methacrylate/methyl acrylate (80
720% by weight) copolymer (25% by weight carpitol acetate solution).

(6) 25% acrylic resin B solution: number average molecular weight 40.
000 methyl methacrylate/methyl acrylate (50
150% by weight) copolymer (25% by weight carpitol acetate solution).

(7) 25% acrylic resin C solution number average molecular weight 100
．． 000 methyl methacrylate/methyl acrylate (8
0720 weight ratio) copolymer (25% by weight carpitol acetate solution).

(8) 25% acrylic resin solution: number average molecular weight 40.
000 methyl methacrylate/n-butyl methacrylate (40/60 weight ratio) copolymer (25% by weight carpitol acetate solution).

(Book 2) Appearance of the coating (coating) Observe the appearance of the test piece obtained by the above method, and check if the coating has formed a smooth continuous coating without any coating defects such as cracks, scratches, wrinkles, or dents. It was judged as good.

(Part 3) Adhesiveness to metal materials: When 100 pieces of 1 m + O square material were cut into squares and peeled off with cellophane tape, the number of remaining pieces was expressed as x/l OO.

(Book 4) Flexibility: The appearance of the coating was evaluated after it was bent 180 degrees around an iron core of 10a+mφ with the coating on the outside. Those with cracking or peeling were considered poor, and those with no abnormalities were considered good.

(Book 5) Solvent resistance: The paint film was vigorously wiped back and forth 10 times with gauze soaked in methyl ethyl ketone, and those with no abnormality were marked as O, and those with no dissolution and significant gloss and pixelation were marked as defective.

(Y8) Adhesion to fluororesin coating film: Expressed as x/l OO in the same manner as in (Zero 3). All showed interlayer adhesion between the primer and the fluororesin coating.

In addition, coatings with poor appearance were not evaluated as overall coatings.

Table 2 (11) Polyfluorinated vinyl resin manufactured by du Pont,
Product name procedural amendment (self-imposed January 22, 1988)

Claims (1)

[Claims] 1. Polyol resin (A) having a number average molecular weight of 900 or more,
A primer composition for a fluororesin paint, comprising a blocked polyisocyanate compound (B) and a thermoplastic acrylic resin (C) as essential components.