JPH03172368A - Coating composition - Google Patents

Abstract

PURPOSE:To obtain the title composition containing a vehicle as a main ingredient obtained by adding an alkyletherified melamine resin to a mixture of acrylic resin and non-yellowing type polyfunctional block isocyanate and useful as a facing material for car and having excellent acid resistance and economical efficiency. CONSTITUTION:The objective composition obtained by adding a metal foil-like pigment, transparent pigment, high-boiling point solvent to a vehicle obtained by blending (A) an acrylic resin having 1800-8000 number-average molecular weight, 60-120 OH value and 5-20 acid value with (B) a non-yellowing type polyfunctional block isocyanate and adding (C) an alkyletherified melamine resin having 400-1200 number-average molecular weight to the blend. Furthermore, blend ratio of the composition ingredients is preferably 50-80 pts.wt. in the ingredient A, each 50-20 pts.wt. in ingredients B and C and 50/50-90/10 in the ingredient B/ingredient C.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION This invention relates to automotive paints, particularly automotive topcoat compositions.

OBJECTS OF THE INVENTION The object of the present invention is to develop a paint that is highly resistant to acid rain while using a general resin that is excellent in terms of economy and workability.

Conventional technology Acid rain is one of the conditions that deteriorates the top coats of automobiles, and the appearance of acrylic resin paints and polyester resin paints, which are the most commonly used top coats in the past, has become defective such as stains and discoloration. This may lead to further damage to the paint film.

On the other hand, silicone resin-based, fluororesin-based, and polyurethane resin-based paints that are highly resistant to acid rain are expensive and have drawbacks such as difficulty in painting workability.

In JP-A-61-143472, the Tg is below 0°C and the hydroxyl value is 20 to 130. A melamine resin is used as a crosslinking agent for a thermosetting resin acrylic resin with an acid value of 6 to 40, and to this,
It is only stated that a small amount of isocyanate may be used in combination, but does not describe the effects associated with the combined use.

JP-A No. 60-67515 discloses that an acrylic copolymer having a hydroxyl value of 20 to 200 containing ε-caprolactone modification and a nil monomer is heat-cured with aminoadehyde resin and/or isocyanate as a crosslinking agent for polyester resin. However, there is no description of the effects associated with the combined use of melamine resin and isocyanate, and
This is a technology for resin systems that use polyester resin.

JP-A-59-36112 states that when an acrylic copolymer with a T of 950°C or less contains an active hydroxyl group or an active amide group, a crosslinking agent consisting of a polyfunctional isocyanate, an aminoadehyde resin, etc., or a mixture thereof can be used. It does not describe the effects associated with the combined use of a crosslinking agent.

Furthermore, the acid resistance level of the prior art is not sufficient to reach the level targeted by the present invention.

Means for Solving the Problems The present invention provides number average molecular weights i, aoo~a, ooo,
Acrylic resin 5 with hydroxyl value 60-120 and acid value 5-20
A coating material containing 50 to 20 parts by weight of a crosslinking agent consisting of an alkyl etherified alkyl etherified melamine resin and a non-yellowing type polyfunctional block isocyanate based on 0 to 80 parts by weight, the alkyl etherified melamine resin as a crosslinking agent and The ratio of non-yellowing polyfunctional block isocyanate is 501
The object of the present invention is to take measures against acid rain, which is becoming worse, by using a coating composition characterized by a ratio of 50 to 90/10.

Structure of the invention Number average molecular weight used in the present invention 1,800 to 8,000,
An acrylic resin having a hydroxyl value of 60 to 120 and an acid value of 5 to 20 can be polymerized, for example, from the following monomers by a conventional method.

(1) Hydroxyl groups such as droxylmethyl (meth)acrylate, droxylethyl (meth)acrylate, droxylpropyl (meth)acrylate, hydroxylbutyl (meth)acrylate, N-methylolacrylamine, etc. (2) Ethylene monomers having a carboxyl group such as (meth)acrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, etc. (3) Methyl (meth)acrylate, (meth)acrylic acid Ethyl, propyl (meth)acrylate, butyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, n-dodecyl acrylate, etc. ) Ethylenic monomers copolymerizable with the monomers (1) and (2), such as acrylic acid alkyl ester, (meth)acrylonitrile, styrene, etc. are used.

If the number average molecular weight is less than i, aoo, there will be insufficient crosslinking and sufficient coating quality will not be obtained; if it exceeds 8,000, the viscosity will increase and an appearance with excellent smoothness etc. will not be obtained.

The preferred range is 3,000 to 7,000.

When the hydroxyl value is less than 60, both adhesion and curability decrease.

If it exceeds 120, the remaining hydroxyl groups will reduce water resistance and acid resistance, which is not preferable.

The preferred range is 80-110.

If the acid value is less than 5, it will not cure sufficiently, and if it exceeds 20, the stability of the paint during storage will deteriorate, or it will harden too quickly.
This is not preferred because the appearance of the coating film lacks smoothness.

The preferred range is 8-15.

The crosslinking agent added to the acrylic resin consists of the following combinations. First, the alkyl etherified melamine resin used is, for example, methylated melamine resin, n-butylated melamine resin, isobutylated melamine resin, etc., in which the alkoxy group is a methoxy group, ethoxy group, n-butoxy group, i-
Examples include alkoxymethylmelamine resins having butoxy groups and the like.

These resins are usually obtained by subjecting melamine to an addition reaction or addition condensation reaction with an aldehyde such as formaldehyde or paraformaldehyde, and then etherifying the resulting product with a monohydric alcohol having 1 to 4 carbon atoms. These alkyl etherified melamine resins are synthesized by conventional methods and have a number average molecular weight of about 400 to 1,200.

If the number average molecular weight is less than 400, the ratio of low molecular weight resins will increase, resulting in an increase in volatile content, while if it exceeds 1.200, the solid content during coating will decrease and the appearance will also deteriorate, which is not preferable.

The preferred range is 600-1,000. A conventional cured coating film in which an acrylic resin is cured only with an alkyl etherified melamine resin cannot ensure the level of acid resistance targeted by the present invention.

Non-yellowing type polyfunctional block isocyanates include non-yellowing type aliphatic polyfunctional isocyanates such as hexamethylene diisocyanate (hereinafter referred to as MDI), alicyclic polyfunctional isocyanates such as isophorone diisocyanate (hereinafter referred to as IPDI), and other isocyanates such as 801 ,
Part of H12801 (hydrogenated 1401) etc. can be used, and partial blocks, (
complete) block is used.

Blocking agents include acetone oxime, cyclohexanone oxime, acetophenone oxime, benzophenone oxime, and the like.

Among the above, MEk oxime blocked IPDI
is most preferred.

Although conventional cured coatings made of acrylic resins with isocyanate alone have good acid resistance, they cannot achieve the objectives of the present invention in terms of low-temperature curability, economical efficiency, painting workability, etc.

Note that it is also effective for the stability of the paint to mix the acrylic resin and the blocked isocyanate in advance.

When curing an acrylic resin with the crosslinking agent, the ratio is 50 to 80 parts by weight of the acrylic resin to 5 parts by weight of the crosslinking agent.
It is 0 to 20 parts by weight.

If the crosslinking agent is less than 10, a sufficient cured coating film cannot be obtained,
If it exceeds 50, the acid resistance will decrease if the alkyl etherified melamine resin is large, and the coating strength will be insufficient if the non-yellowing type polyfunctional block isocyanate is large.

The preferred range is 25-45.

The present invention is characterized in that an alkyl etherified melamine resin and a non-yellowing polyfunctional block isocyanate are used together as a crosslinking agent, and it is particularly important that the ratio thereof is from 50,150 to 9,515.

When the alkyl etherified melamine resin is less than 50, curing is insufficient and gas hole properties are poor, and when it exceeds 95, acid resistance is not sufficiently improved.

The preferable range of alkyl etherified melamine resin/non-yellowing polyfunctional block isocyanate is 70/30 to 90
/10.

In the present invention, by crosslinking an acrylic resin with a specific ratio of alkyl etherified melamine resin and isocyanate,
This covers the poor acid resistance of melamine resin crosslinked coatings, and the present invention cannot be achieved if a sufficient amount of alkyl etherified melamine resin is present in the formulation to crosslink the acrylic resin.

Other raw materials that can be incorporated into the composition of the present invention include the following raw materials commonly used as paints.

Aluminum foil, bronze foil, tin foil, gold foil, silver foil, copper foil, metallic titanium foil, stainless steel foil, nickel foil, chromium, cobalt sulfide, manganese sulfide, titanium sulfide, alloy foils of these, plastics with a particle size of 10 to 45μ. metal foil coated with, a metal foil-like pigment selected from foil-like phthalocyanine blue, inorganic transparent iron oxide, such as Cicotrans Red L2915D, Cicotrans Yellow L
1915, 1916 (both manufactured by Ciba Geigy) and organic Chromophthal Red^2B (manufactured by Ciba Geigy), and the dyes are deep colors such as red, blue, purple, black, and brown, such as Orazole Black RL, Orazole Red B
, Orazole Yellow 3R (all manufactured by Ciba Geigy)
Pigments such as transparent pigments, titanium dioxide, Shanin blue, Shanin green, quinacridone, indanthrone, isoindolinone, perylene, anthrapyrimidine, carbon black, benzimidacylon, yellow iron oxide, red iron oxide, ethylene glycol mono Alcohol solvents such as butyl ether and ethylene glycol monobutyl ether acetate, hydrocarbon solvents such as Tsurpetz 100 and Tsurpetz 150, ether solvents such as carbitol acetate and butyl carbitol, and high boiling point solvents such as ketone solvents such as isophorone, e.g. , ester solvents such as ethyl acetate and butyl acetate, aromatic solvents such as toluene and xylene, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and acetone, alcohols such as methanol, butanol, isopropanol, and ethylene glycol monomethyl ether. A low boiling point solvent such as a system solvent can be adjusted appropriately and used.

The composition of the present invention is prepared by applying electrodeposition paint and intermediate coating paint to iron parts one to three times in the same manner as in ordinary automobile painting, and then applying the resin component of the composition of the present invention as a vehicle. The composition of the present invention can be used as a topcoat, or as a clear coat to protect the topcoat after a conventional solid or metallic paint has been applied.

In this case, the coating film thickness, coating machine, coating conditions, etc. are the same as those for conventional automobile finishing coatings.

When applying the composition of the present invention as a solid top coat or a clear paint on top of the top coat, it is preferable to use air spray or electrostatic coating, and the viscosity is 20 to 25.
sec/#FC/20℃ Painted to a dry film thickness of 30 to 50μ.

In addition, the curing conditions for baking are not much different from those when using melamine resin or isocyanate alone, and 120 to 1
50° C., W degrees for 15-30 minutes.

The present invention will be explained in more detail below with reference to Examples.

Examples Below Margins Example 1 (Clear paint formulation) (Resin solid content ratio) Book 1 Mitsui Toatsu Co., Ltd. Kneepan 2ON-60 Butyl etherified melamine resin solid 60% Book 2 Dainippon Ink & Chemicals Co., Ltd. Super Beckamine Butyl Ether Melamine resin solid 60% Book 3 Mitsubishi Rayon Co., Ltd. Acrylic resin Dianal H
R-554 Sonolid 60% Number average molecular weight 4,0
00 Hydroxyl value 95 Acid value 5-2012 *4 Acrylic resin ACR-461 manufactured by Nippon Paint Co., Ltd.
Solid 55% Number average molecular fi 8,000 Hydroxyl value 70 Acid value 5-2020 Ne5 Resident Bayer's block isocyanate HDI Zero6 Ne1 Ne2 melamine resin content *7 *5 Blocked isocyanate note Painting solvent is Exxon Tsurpets-15 manufactured by Kagakusha
0 was used.

Below are the margins Acid resistance test results Acid resistance test results Book 11 *13 Book 14 Book 15 Book 16 0.4N Hydrochloric acid spot 85℃, 40 v for 15 minutes
ol sulfuric acid 40℃, 8 hours 40Xwt ['fIi
Spot 60℃, 15 minutes PH21 acid spot 60
℃, 60 minutes PH2 sulfuric acid spot 10℃, 60 minutes P
! 12 Sulfuric acid spot 80℃, 60 minutes or less Note: For spot testing, approximately 0.5 ml of each solution is dropped onto a test piece, and after being left for a predetermined period of time, the depth of corrosion of the coating film by the solution is measured using StlRFCOM (manufactured by Tokyo Seimitsu Co., Ltd.) <Two-dimensional surface Roughness meter).

The closer the value is to 0, the better. Unit Rnax (μ) Grain ratio data A Present invention Example 1 B Acrylic resin/melamine resin curing paint Conventional product C Acrylic polyol/isocyanate two-component curing paint Evaluation method Rice mold workability Acid resistance No gelatinization or lumps are formed at 50°C for 120 hours.The above conditions are met.

Good Sagging and armpits may occur. Sagging and armpits are likely to occur No abnormalities Δ Slightly eroded, but no loss of shine Erosion, loss of gloss Even when baked at a low temperature of 20°C, the film performance remains unchanged. Are better.

Even when baked at a low temperature of 20°C, the film performance is almost the same as the conventional product.The effect of the invention on the film performance when B is cured at 140°C for 30 minutes.The present invention avoids the drawbacks of workability that high-quality polyurethane paints have. At the same time, it has achieved the same ease of handling as conventional acrylic resin/melamine resin, but has improved low-temperature curing properties and acid resistance, resulting in a coating composition that is also highly economical. .

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Claims (1)

[Claims] Number average molecular weight 1,800-8,000, hydroxyl value 60-
120, 50 to 80 parts by weight of an acrylic resin with an acid value of 5 to 20, and 50 to 2 parts of a crosslinking agent consisting of an alkyl etherified melamine resin and a non-yellowing polyfunctional block isocyanate.
1. A coating composition containing 0 parts by weight of alkyl etherified melamine resin as a crosslinking agent and a non-yellowing type polyfunctional block isocyanate in a ratio of 50/50 to 90/10.