JPH0625597A - Interlaminar chipping-resistant paint for automobile - Google Patents

Abstract

PURPOSE:To provide the subject paint containing two specific kinds of urethane resins and a polyol resin, having excellent storage stability and curability and capable of lowering the coating amount without deteriorating the chipping resistance of the coated film and the spray workability. CONSTITUTION:The objective paint contains (A) a urethane resin produced from a methylene diisocyanate (MDI) prepolymer containing >=5wt.% of a prepolymer having three-dimensional structure by blocking the terminal NCO group of the MDI prepolymer with an oxime resin, (B) a urethane resin produced from a toluene diisocyanate (TDI) prepolymer containing >=5wt.% of a prepolymer having three-dimensional structure by blocking the terminal NCO group of the TDI prepolymer with a lactam resin and (C) a polyol resin at a B/A weight ratio of 0.8-1.4. The component A is preferably produced by reacting a part of the NCO groups of MDI with an OH-containing compound such as polyester and blocking and inactivating the remaining NCO groups with acetoxime, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interlayer anti-chipping paint for automobiles, and more specifically, it is applied by colliding small objects such as pebbles and metal fragments on the road surface, which are repelled by wheels during traveling of the automobile, with the vehicle body. The present invention relates to a heat-curable one-component polyurethane resin-based inter-layer chipping resistant coating for automobiles, which is applied to a vehicle body to prevent chipping, which is a phenomenon of peeling of a film, and rusting of the vehicle body caused thereby.

[0002]

2. Description of the Related Art As an interlayer chipping-resistant coating used for forming a chipping-resistant coating layer between a plurality of coating layers applied to an automobile body, for example, a heat-curable one-component polyurethane resin-based coating is used. It is often used because it is easy to use. However, in order to obtain the desired chipping resistance, it is the current situation that the coating film thickness after drying should be about 100 μm. Recently, various paints have been proposed as coating materials for forming excellent coating films. For example, JP-A-62-86060 discloses isocyanates and polyamide polyamines whose ends are blocked with an oxime-based blocking agent. And / or vehicle coatings containing polyoxypolyamines, fillers, solvents.
Further, in JP-A-64-43573, (a) a blocked isocyanate in which a polyurethane prepolymer having a polyisocyanate or a terminal isocyanate group is blocked with an oxime or a lacrham, and (b) an epoxide compound to a polyamine or A polyamine polyether polyester which is a condensation product of a polyamine polyether which is an adduct of tetrahydrofuran and an organic carboxylic acid, or an addition product of a compound having an oxirane ring to a polyamide polyamine which is a condensation product of a polyamine and an organic carboxylic acid. A coating composition comprising a polyamide polyamine polyether is described.

[0003]

In order to secure a film thickness of about 100 μm for the chipping-resistant coating film, it is necessary to apply a large amount of paint, and as a result, the absolute amount of paint solvent used also increases. On the other hand, reducing the amount of the interlayer anti-chipping paint (consisting of the solid content and the solvent) enhances the efficiency of the painting work and is advantageous in cost. Further, since the solvent in the paint deteriorates the working environment at the time of coating, it is preferable that the absolute amount used is small in order to improve the working environment. Therefore, research has been conducted to reduce the amount of the interlayer chipping-resistant paint used and the solvent ratio in the paint, but if the solvent content in the paint is simply reduced, the coating workability, for example, spray workability, is poor. It becomes a paint, and simply reducing the coating amount of the conventional chipping-resistant paint and reducing the absolute amount of the solvent significantly reduces the coating performance. Further, a heat-curable one-component polyurethane resin-based interlayer chipping-resistant coating material for automobiles is required to have a good balance of good storage stability and good curability. However, even if the coating film forming material for vehicles described in JP-A-62-86060 and the coating composition described in JP-A-64-43573 are used, sufficiently satisfactory chipping resistance and No spray workability and good storage stability and curability can be obtained.

The object of the present invention is to reduce the coating amount without lowering the chipping resistance of the resulting coating film and the workability during spray coating, that is, the spray workability, and to obtain good storage stability and curing. An object of the present invention is to provide an interlayer chipping-resistant paint for automobiles having both properties.

In order to solve the above-mentioned problems of the prior art, the inventors of the present invention have earnestly studied and as a result,
MDI (methylene diisocyanate) containing a specific amount of three-dimensional structure prepolymer TDI (toluene diisocyanate) containing a urethane resin obtained by pre-reacting the terminal isocyanate groups of the prepolymer with an oxime resin and a specific amount of three-dimensional structure prepolymer By blending the terminal isocyanate groups of the prepolymer with the urethane resin pre-reacted with the lactam resin in a specified ratio, the spray workability during coating is good, and the resulting coating film shows excellent chipping resistance. It has been found that the coating amount can be reduced and that it has both good storage stability and curability.

[0006]

That is, the interlayer anti-chipping paint for automobiles of the present invention comprises: (1) The terminal isocyanate group of an MDI prepolymer containing 5% by weight or more of a prepolymer having a three-dimensional structure is blocked with an oxime resin. A urethane resin, and (2) a urethane resin in which the terminal isocyanate group of a TDI prepolymer containing 5% by weight or more of a prepolymer having a three-dimensional structure is blocked with a lactam resin, (3)
(2) / (1) in a weight ratio containing a polyol resin and
= 0.8 to 1.4.

In the above-mentioned constitution, when the ratio of the prepolymer having the three-dimensional structure in (1) and / or the ratio of the prepolymer having the three-dimensional structure in (2) is less than 5% by weight, the crosslinking density of the urethane bond is And the strength of the coating film is weakened, so that the chipping resistance of the resulting coating film is reduced. Also, (2) /
If the weight ratio of (1) is less than 0.8, the spray workability is poor and the storage stability of the resulting coating composition is deteriorated. On the contrary, the weight ratio of (2) / (1) is 1 When it exceeds 0.4, the coating material is not sufficiently cured, and the resulting coating film has a drawback that the chipping resistance is lowered. Therefore, the ratio of the prepolymer having a three-dimensional structure in (1) and (2) is 5 in each case.
It is necessary that the content be at least wt%. Also, (2) /
The weight ratio of (1) is 0.8 to 1.4.

The polyol resin used in the coating material of the present invention includes polyester polyol, polyether polyol, polyurethane polyol, acrylic polyol, nitrogen-containing polyol (amine polyol), castor oil derivative, tall oil derivative, polybutadiene polyol, butyral resin, Examples thereof include alkyd resin and epoxy resin. These polyol resins may be used alone or in combination of two or more kinds.

As the polyester polyol, adipic acid, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, trimellitic acid, succinic acid, azelaic acid, pimelic acid, sebacic acid, fumaric acid, hexahydrophthalic acid, methylhexahexyl Compounds having a polybasic acid such as hydrophthalic acid, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, and dimer acid, and a compound having at least two or more hydroxyl groups in one molecule, for example, ethylene glycol, diethylene glycol, polyethylene glycol, polypropylene glycol , Polytetramethylene ether glycol, propylene glycol, butylene glycol, neopentyl glycol, hydrogenated bisphenol A, glycerin, butanediol, 1,3-pentanediol, hexane Ol, trimethyl pentanediol, hexane triol, trimethylol ethane, trimethylol propane, those synthesized by a conventional method from the pentaerythritol.

As the polyether polyol, polyoxyethylene glycol, polyoxypropylene glycol, polyoxybutylene glycol, polyoxypropylene triol, polyoxypropylene quadrol and the like can be used. The hydroxyl-bonded carbon chain synthesized using an amine-based raw material as a starting material is a type of polyol branched from nitrogen, that is, a so-called nitrogen-containing polyol (amine-based polyol) itself has a catalytic action, Particularly preferred as the polyol component of the coating composition of the present invention.

As the polyurethane polyol, a compound having a terminal hydroxy group obtained from a polyhydroxy compound and a polyvalent isocyanate compound is used.

The acrylic polyols include hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, trimethylolpropane acrylic acid monoesters, their corresponding methacrylic acid derivatives, and hydroxyl groups such as polyhydroxyalkyl maleate and fumarate. Contained monomers and acrylic monomers such as acrylic acid or methacrylic acid methyl, ethyl, butyl, propyl, hexyl, 2-ethylhexyl, hydroxyethyl ester, etc., or α, β-ethylenic monomers such as styrene, vinyltoluene, vinyl acetate, etc. Examples thereof include those obtained by copolymerization with a monomer having a saturated double bond.

Castor oil derivatives include triglyceride of ricinoleic acid. As the polybutadiene polyol, a terminal hydroxy type such as 1,2-polybutadiene and 1,4-polybutadiene can be used.

As the block polyisocyanate compound which can be used, polyesters, polyethers having a hydroxyl group in a part of the isocyanate groups of MDI or TDI,
A compound such as MDI, which is obtained by reacting acrylic and epoxy with the remaining isocyanate group having active hydrogen.
In the case of acetoxime, ketoxime, methyl ethyl ketone oxime, methyl isobutyl ketone oxime, etc., and in the case of TDI, by blocking and inactivating with lactams such as ε-caprolactam, β-propiolactam, etc. It can be liquefied.

The prepolymer having a three-dimensional structure is a prepolymer in a state in which a polyol is branched in three directions, the tips of each branch are bonded to a urethane group, and blocked by a blocking agent. In the present invention, it is essential that the prepolymer in such a state contains 5% by weight or more of both the component (1) and the component (2). The type of polyol is not particularly limited as long as it is a polymer in the above state, and the types of polyols exemplified above can be used. Specifically, for example, a urethane resin obtained by previously reacting a terminal urethane group of polyether polyol with methyl ethyl ketone oxime can be mentioned. On the other hand, the two-dimensional structure prepolymer means that the polyol is a linear prepolymer, and the types of polyols that can be used are the same as those for the three-dimensional structure prepolymer.

As the solvent component, in addition to aromatic solvents such as toluene and xylene, hydrocarbons such as solvent naphtha, ketones such as methyl isobutyl ketone and cyclohexanone, acetic acid and ethylene glycol monoethyl ether, or diethylene glycol monoethyl. One or more kinds of esters such as ester with ether, 3-methoxybutyl acetate and dibasic acid ester can be used.

In order to reduce the content of volatile organic compounds (solvent content) without increasing the viscosity, it is advisable to add a filler to the paint. The filler is preferably barium sulfate or the like. If the content of the filler is less than 3% by weight, the resulting coating film has poor chipping resistance, and conversely,
If the content of the filler exceeds 15% by weight, the viscosity of the coating material increases and it becomes difficult to apply the coating material.
It is preferable to add 5% by weight.

In addition to the above-mentioned barium sulfate, the chipping-resistant coating material of the present invention contains, for example, conventional additives such as talc, calcium carbonate, clay, alumina, silica, hiruite, clay and titanium oxide, carbon black, red iron oxide, and oxide. Coloring pigments such as yellow, phthalocyanine blue and phthalocyanine green, repelling agents, leveling improvers, defoamers, surfactants, curing accelerators, antistatic agents, pigment dispersants, anti-sagging agents, thickeners, etc. You may mix.

In order to improve the coating workability in the coating line, one or more solvents can be added to the interlayer chipping-resistant coating composition of the present invention. As such a solvent, for example, an aromatic type, an aliphatic type, an alcohol type,
Examples include ketone-based solvents. The solvent may be selected in consideration of compatibility with the block polyisocyanate compound and the polyol. It is preferable to use the solvent in a small amount as long as it does not deteriorate the spray workability.

In order to prepare the interlayer anti-chipping coating material for automobiles of the present invention, each component together with a solvent is dispersed by three rolls, a ball mill, a pot mill, a steel mill, a pebble mill, an attritor, a sand mill, a sand grinder, a roll mill and a blade. It suffices to charge the mixture in a mixing and dispersing machine such as a high-speed stirrer to uniformly mix and disperse it.

The coating of the coating composition of the present invention on an automobile body is performed on a desired portion of a steel plate surface which has been subjected to a chemical conversion treatment and which has been subjected to electrodeposition coating with a primer. As a painting method, normal air spray,
Spraying methods such as electrostatic air spray, airless spray, and hot airless spray may be used.

In order to cure the chipping-resistant coating material of the present invention sprayed on the car body, baking and drying at a temperature of 100 to 120 ° C. for about 5 to 15 minutes is sufficient. The dry film thickness is preferably about 50 to 200 μm. 50μ
If it is less than m, the chipping resistance required for the coating film cannot be obtained, and if it exceeds 200 μm, problems such as sagging of the coated surface after coating and generation of cracks during baking and drying may occur.

The coating material of the present invention is applied, for example, to the surface of a white body with a sealer and then the coating material of the present invention.
Heat in a sealer furnace at 0 to 120 ° C. for 5 to 20 minutes, then heat in a middle coating furnace at 130 to 150 ° C. for 20 to 30 minutes after intermediate coating, and further heat in a top coating furnace at 130 to 150 ° C. for 20 to 30 minutes after top coating. Useful in cases.

[0024]

Since the specific component (1) and the specific component (2) are contained in the weight ratio of (2) / (1) = 0.8 to 1.4, storage stability and curability are improved. Is well balanced. Further, the spraying workability during coating and the chipping resistance of the resulting coating film are excellent.

[0025]

The present invention will be described in more detail with reference to the following examples and comparative examples. The following examples are for explaining the present invention and do not have any limiting meaning. In the examples and comparative examples, the component (1)
And the total amount of the component (2) are all 32 parts by weight, and the weight ratio (2) / (1) is different.

Example 1 Termination of an MDI prepolymer consisting of 25% by weight of a three-dimensional structure prepolymer (polyether polyol having an average molecular weight of 2000) and 75% by weight of a prepolymer having a two-dimensional structure (polyether polyol having an average molecular weight of 1200). 17 parts by weight of a urethane resin having an isocyanate group pre-reacted with methyl ethyl ketone (MEK) oxime, 35% by weight of a prepolymer having a three-dimensional structure (polyether polyol having an average molecular weight of 2000) and a prepolymer having a two-dimensional structure (polyether having an average molecular weight of 1000) Ether polyol) 65
15 parts by weight of a urethane resin obtained by previously reacting the terminal isocyanate group of TDI prepolymer consisting of 10% by weight with ε-caprolactam, 4 parts by weight of an amine-based polyol (manufactured by Sanyo Kasei Co., Ltd., New Pole NP-300), and barium sulfate 12 Parts by weight, 9 parts by weight of calcium carbonate, 10 parts by weight of talc, 24 parts by weight of an aromatic high-boiling solvent, 8 parts by weight of an ester solvent, and 1 part by weight of a defoaming agent were mixed, and the paint of Example 1 [Paint 1: (2) / (1) = 0.882] was obtained.

Example 2 Termination of MDI prepolymer consisting of 5% by weight of a prepolymer having a three-dimensional structure (polyether polyol having an average molecular weight of 2000) and 95% by weight of a prepolymer having a two-dimensional structure (polyether polyol having an average molecular weight of 1200). 14 parts by weight of a urethane resin obtained by previously reacting an isocyanate group with MEK oxime, 5% by weight of a prepolymer having a three-dimensional structure (a polyether polyol having an average molecular weight of 2000) and a prepolymer having a two-dimensional structure (a polyether polyol having an average molecular weight of 1000) 18 parts by weight of urethane resin obtained by previously reacting terminal isocyanate groups of TDI prepolymer consisting of 95% by weight with ε-caprolactam, amine-based polyol (manufactured by Sanyo Kasei Co., Ltd., trade name New Pole NP-30).
0) 4 parts by weight, barium sulfate 12 parts by weight, calcium carbonate 9 parts by weight, talc 10 parts by weight, aromatic high boiling solvent 2
4 parts by weight, 8 parts by weight of an ester solvent, and 1 part by weight of a defoaming agent were mixed, and the coating material of Example 2 [Paint 2: (2) / (1) =
1.29] was obtained.

Comparative Example 1 Terminal of an MDI prepolymer comprising 25% by weight of a prepolymer having a three-dimensional structure (a polyether polyol having an average molecular weight of 2000) and 75% by weight of a prepolymer having a two-dimensional structure (a polyether polyol having an average molecular weight of 1200). 19 parts by weight of a urethane resin in which an isocyanate group is preliminarily reacted with MEK oxime, 35% by weight of a prepolymer having a three-dimensional structure (a polyether polyol having an average molecular weight of 2000) and a prepolymer having a two-dimensional structure (a polyether polyol having an average molecular weight of 1000) 13 parts by weight of a urethane resin obtained by previously reacting 65% by weight of the terminal isocyanate group of TDI prepolymer with ε-caprolactam, an amine-based polyol (manufactured by Sanyo Kasei Co., Ltd., trade name NEWPOL NP-3
00) 4 parts by weight, barium sulfate 12 parts by weight, calcium carbonate 9 parts by weight, talc 10 parts by weight, aromatic high boiling solvent 24 parts by weight, ester solvent 8 parts by weight, defoamer 1 part by weight, Paint of Comparative Example 1 [Paint 3: (2) / (1) =
0.684] was obtained.

Comparative Example 2 Termination of MDI prepolymer consisting of 10% by weight of a prepolymer having a three-dimensional structure (polyether polyol having an average molecular weight of 2000) and 90% by weight of a prepolymer having a two-dimensional structure (polyether polyol having an average molecular weight of 1200). 13 parts by weight of a urethane resin in which an isocyanate group has been reacted with MEK oxime in advance, 10% by weight of a prepolymer having a three-dimensional structure (a polyether polyol having an average molecular weight of 2000) and a prepolymer having a two-dimensional structure (a polyether polyol having an average molecular weight of 1000) 19 parts by weight of a urethane resin obtained by previously reacting the terminal isocyanate group of 90% by weight of TDI prepolymer with ε-caprolactam, an amine-based polyol (manufactured by Sanyo Chemical Co., Ltd., trade name NEWPOL NP-3
00) 4 parts by weight, barium sulfate 12 parts by weight, calcium carbonate 9 parts by weight, talc 10 parts by weight, aromatic high boiling solvent 24 parts by weight, ester solvent 8 parts by weight, defoamer 1 part by weight, Paint of Comparative Example 2 [Paint 4: (2) / (1) =
1.46] was obtained.

Comparative Example 3 Termination of MDI prepolymer consisting of 3% by weight of a prepolymer having a three-dimensional structure (polyether polyol having an average molecular weight of 2000) and 97% by weight of a prepolymer having a two-dimensional structure (polyether polyol having an average molecular weight of 1200). 17 parts by weight of a urethane resin in which an isocyanate group is preliminarily reacted with MEK oxime, 4% by weight of a prepolymer having a three-dimensional structure (a polyether polyol having an average molecular weight of 2000) and a prepolymer having a two-dimensional structure (a polyether polyol having an average molecular weight of 1000) 15 parts by weight of urethane resin obtained by previously reacting the terminal isocyanate group of 96% by weight of TDI prepolymer with ε-caprolactam, amine polyol (manufactured by Sanyo Chemical Co., Ltd., trade name NEWPOL NP-30
0) 4 parts by weight, barium sulfate 12 parts by weight, calcium carbonate 9 parts by weight, talc 10 parts by weight, aromatic high boiling solvent 2
4 parts by weight, 8 parts by weight of an ester solvent, and 1 part by weight of a defoaming agent were mixed, and the paint of Comparative Example 3 [paint 5: (2) / (1) =
0.882] was obtained.

Performance Evaluation Test 1 Paints 1 to 5 were airlessly coated on an electrodeposition plate, and the temperature was maintained at 110 ° C. for 10
The sample was dried for 1 minute to a film thickness of 50 μm, and after the intermediate coating was applied, it was dried at 140 ° C. for 20 minutes to form an intermediate coating thickness of 30 μm.
A top coating thickness of 0 μm is formed, and then JIS B1131
The three types of M-shaped brass hex nuts specified in 1 above were dropped from a height of 2 m, and the weight of the dropped nut until the scratches on the coating film reached the electrodeposition coated surface was displayed.

Result 1 (Result of Performance Evaluation Test 1) Paints 1 to 5 had nut weights of 8 kg, 7 kg, respectively.
With 10 kg, 4 kg and 4 kg, it was revealed that the paints 1 to 3 have excellent chipping resistance. Paint 4,
No. 5 was inferior to the paints 1 to 3 in chipping resistance.

Performance Evaluation Test 2 4 kg of the paint was filled in a 4 liter container, left for 10 days in a constant temperature bath at 40 ° C., taken out, and gently stirred with a spatula, a glass rod or the like. Then, after cooling to 20 ° C., using an airless pump, coating pressure 100 kg / cm ² , tip 62
1 was used to measure the pattern width from a coating distance of 30 cm and compare with the expected pattern width.

Result 2 (Result of Performance Evaluation Test 2) Paints 1, 2, 4 and 5 had good spraying workability after the storage stability test, and there was almost no change in the pattern width. The paint 3 showed a decrease in the pattern width in the spraying work after the storage stability test.

Summary of Results 1 and 2 From the results 1 and 2, it can be seen that the paints 1 and 2 are excellent in chipping resistance and spray workability.

[0036]

As a result, the interlayer anti-chipping paint for automobiles of the present invention has the above-mentioned constitution and is therefore superior in chipping resistance and spraying workability to the conventional similar paints. Therefore, it is possible to maintain the same chipping resistance even when the film thickness of the chipping-resistant coating film is thin compared to the case of using the same type of conventional coating material, and it is possible to maintain the same coating resistance as compared with the conventional inter-layer chipping-resistant coating material for automobiles. It was possible to reduce the amount used. As a result, it is possible to reduce the absolute amount of the diluent solvent used for the interlayer anti-chipping paint for automobiles, which is also useful in terms of environmental protection during painting.

Furthermore, since the chipping-resistant coating film formed by using the coating composition of the present invention has a better chipping resistance performance (higher hardness) than the conventional chipping-resistant coating film, it is suitable for automobiles subject to chipping. It is possible to prevent rust from occurring for a longer period of time and maintain a smooth coating surface, improving the coating quality of automobiles.

Since the coating composition of the present invention is a heat-curable one-component polyurethane resin-based coating composition having good storage stability and good curability in a well-balanced manner, it is easy to store and cure, and practically easy to handle. .

Claims (1)

[Claims] (1) A urethane resin in which the terminal isocyanate groups of an MDI prepolymer containing 5% by weight or more of a prepolymer having a three-dimensional structure are blocked with an oxime resin.
(2) T containing 5% by weight or more of a prepolymer having a three-dimensional structure
A urethane resin in which the terminal isocyanate group of the DI prepolymer is blocked with a lactam resin and (3) a polyol resin are contained, and the weight ratio is (2) / (1) = 0.8 to
An interlayer anti-chipping paint for automobiles, which is 1.4.