JPH04335074A - Low-temperature curing one-pack coating composition having flexibility and weatherability - Google Patents

Abstract

PURPOSE:To obtain a one-pack coating composition that has reduced crosslinking temperature and gives excellent film properties at low temperature by using as constituents a blocked isocyanate comprising a polyisocyanate which is derived from a non-yellowing diisocyanate and whose isocyanate groups are masked, and a cure accelerator comprising a specified organometallic compound. CONSTITUTION:A one-pack coating composition which consists mainly of a diol and/or triol having a number-average molecular weight of 500 to 1600; a blocked polyisocyanate comprising an aliphatic or alicyclic diisocyanate having the isocyanate groups blocked with a blocking agent such as an oxime compound; a polyol, such as acrylic polyol, having a hydroxyl number of the resin of 10-300mg KOH/g; at least one organotin compound; and a cure accelerator comprising at least one metal compound selected from a metal salt of an organic acid and a diketone metal complex.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to extensible, low-temperature crosslinkable, one-component polyurethane thermosetting coating compositions.

0002

[Prior Art] Conventionally, polyurethane resin paints have excellent abrasion resistance, chemical resistance, and stain resistance.
Polyurethane resin paints derived from non-yellowing polyisocyanates made from aliphatic and alicyclic diisocyanates have even better weather resistance, and the demand for them is on the rise.

However, since polyurethane resin paints are generally two-component, their use has been extremely inconvenient. That is, ordinary urethane resin paints consist of two components, polyol and polyisocyanate, which must be stored separately and mixed at the time of coating. Furthermore, once mixed, the current situation is that the paint gels in a short period of time and becomes unusable. This makes it extremely difficult to perform automatic painting in the field of line painting such as automobiles or weak electric painting.

Furthermore, since it is necessary to thoroughly clean the coating machine and coating tank at the end of the work, the work efficiency is significantly reduced. In order to improve the above-mentioned drawbacks, it has been proposed to use blocked isocyanates in which all active isocyanate groups are blocked with blocking agents. This blocked isocyanate does not react with the polyol at room temperature, but at high temperatures it dissociates the blocking agent and regenerates the active isocyanate group, which reacts with the polyol and causes a crosslinking reaction, thus improving the above-mentioned drawbacks. I can do it.

However, the above-mentioned crosslinking reaction requires a high baking temperature. High baking temperatures not only increase energy costs but also increase air pollution associated with them, and are a fatal drawback when coating materials that are sensitive to heat such as plastics. In addition, automobiles, architectural exteriors, etc. are exposed to various environments and must withstand them. In particular, excellent physical properties of the coating film are required in terms of flexibility, impact resistance, and adhesion even at low temperatures below zero degrees.

Therefore, in the field of polyurethane resin paints, there has been a demand for a one-component polyurethane resin paint that has excellent weather resistance, a low crosslinking temperature, and excellent low-temperature physical properties. Several proposals have been made to lower the crosslinking temperature. In Japanese Patent Publications No. 44-18877, No. 53-138434, No. 56-84714, and No. 57-8217, a specific organic tin compound is added as a catalyst to accelerate curing. Unexamined Japanese Patent Publication 1986-
In JP 199609, a lead compound and an inorganic zinc compound are added as catalysts for accelerating curing.

However, even when the above-mentioned curing accelerator is added to a blocked isocyanate in which the isocyanate groups of a polyisocyanate derived from a non-yellowing diisocyanate are masked, the crosslinking temperature of the paint does not decrease much. ,
Moreover, excellent physical properties of the coating film at low temperatures could not be obtained, and its uses were limited.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a coating composition that has excellent weather resistance, has a low coating crosslinking temperature, and can provide excellent coating film properties at low temperatures. be.

[Means for Solving the Problem] As a result of intensive studies by the present inventors, the above object can be achieved by combining a curing accelerator consisting of a specific block polyisocyanate, a specific polyol, and a specific organometallic compound. We succeeded in achieving this and arrived at the present invention.

That is, the present invention provides (A) a number average molecular weight of 500
A block polyisocyanate in which the isocyanate groups of a polyisocyanate consisting of a diisocyanate which is a diisocyanate which is a diol or triol of 1,600 to 1,600 and an aliphatic or alicyclic diisocyanate are blocked with a blocking agent, (B) Resin hydroxyl value 10-300m
gKOH/g of polyol, and (C) at least one or more organic tin compounds represented by the following formulas (1) and (2), and an organic acid metal salt and diketone metal represented by the following formula (3). This is a low-temperature curable one-component coating composition having flexibility and weather resistance, the main component of which is a curing accelerator made of at least one metal compound selected from complexes.

0010

[C4]

[0011]

[C5]

0012

[C6]

Diols and triols, which are one of the raw materials for the polyisocyanate of the present invention, have an average number of hydroxyl groups in one molecule of 2 and 3, and a number average molecular weight of 500 to 160.
Must be in the range 0. When a diol or triol having a number average molecular weight of less than 500 is used as a component of the crude raw material, the elongation of the formed coating film at low temperatures is insufficient. Furthermore, when a diol or triol having a number average molecular weight exceeding 1,600 is used as a component of the raw material, the resulting polyisocyanate has a low isocyanate content and has low solubility in solvents, making it impractical. Diols like this,
Triols include aliphatic hydrocarbon polyols, polyether polyols, polyester polyols,
Examples include epoxy resins and polycarbonate polyols.

Specific examples of aliphatic hydrocarbon polyols include hydroxyl-terminated polybutadiene and hydrogenated products thereof. Examples of polyether polyols include polyether polyols obtained by adding alkylene oxides such as ethylene oxide and propylene oxide alone or as a mixture to polyhydric alcohols such as glycerin and propylene glycol, and polytetra There are polyether polyols obtained by reacting methylene glycols and alkylene oxides with polyfunctional compounds such as ethylenediamine and ethanolamines.

Examples of polyester polyols include dibasic acids selected from the group of carboxylic acids such as succinic acid, adipic acid, sebacic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, and terephthalic acid. or polyester polyol resins and e.g. Examples include polycaprolactones obtained by ring-opening polymerization of caprolactone using a polyhydric alcohol.

In addition, as polycarbonate polyols, aromatic polyhydric alcohols such as bisphenol A and
, 6-hexanediol and other aliphatic and alicyclic polyhydric alcohols as raw materials by conventional methods. Examples of epoxy resins include novolac type,
β-methylepicro type, cyclic oxirane type, glycidyl ether type, glycol ether type, epoxy type of aliphatic unsaturated compound, epoxidized fatty acid ester type, polyvalent carboxylic acid ester type, aminoglycidyl type, halogenated type, resorcin type, etc. Examples include epoxy resins.

Particularly preferred are polytetramethylene glycol and polycaprolactone polyol. For example, in the case of polytetramethylene glycol, PTG is a commercially available product.
650, PTG1000, PTG1500, PTG18
00 (both manufactured by Hodogaya Chemical Industry Co., Ltd., product name),
For polycaprolactone polyol, Plaxel 3
03, Plaxel 305, Plaxel 308, Plaxel 312, Plaxel 205, and Plaxel 212 (all manufactured by Daicel Chemical Industries, Ltd., trade names). These may be used alone or in combination of two or more.

The diisocyanates of the present invention which are reacted with such diols and triols are aliphatic and alicyclic diisocyanates. The aliphatic diisocyanate preferably has 4 to 30 carbon atoms, and the alicyclic diisocyanate preferably has 8 to 30 carbon atoms, for example,
1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4-trimethyl-1,6
-Hexamethylene diisocyanate, lysine isocyanate, 3-isocyanatomethyl-3,3,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate), 1,3-bis(isocyanatomethyl)
-cyclohexane, 4,4'-dicyclohexylmethane diisocyanate, and the like. Among them,
1,6-hexamethylene diisocyanate (hereinafter referred to as HMDI) is preferred in terms of weather resistance and industrial availability.

[0019] The reaction between the diol or triol and the diisocyanate is carried out at room temperature to 200°C, preferably at 80°C to 200°C.
It is carried out at 140°C. If the reaction temperature is low, it will take too long for the reaction to complete; if the reaction temperature is high, on the other hand, undesirable side reactions will occur, resulting in increased viscosity or coloration of the reaction product, which is impractical. A solvent may be used during the reaction. Examples of solvents that can be used include toluene,
Those inert to isocyanates such as xylene, ethyl acetate, and butyl acetate are preferred. Also, if necessary,
Organic tin compounds, tertiary amine compounds, etc. may be used to promote the reaction between isocyanate groups and hydroxyl groups. Furthermore, an isocyanurate reaction may be performed. The reaction temperature in this case is 40 to 120°C, and a catalyst is usually used.

Examples of the catalyst include tetraalkylammonium hydroxides and organic weak acid salts such as tetramethylammonium, tetraethylammonium, and tetrabutylammonium, trimethylhydroxypropylammonium, trimethylhydroxyethylammonium, triethylhydroxypropylammonium, and triethylhydroxyethyl. Hydroxylkyl ammonium hydroxides such as ammonium, organic weak acid salts, alkali alkylcarboxylic acids such as acetic acid, caproic acid, octylic acid, myristic acid, metal salts such as tin, zinc, lead, etc., aminosilyl groups such as hexamethyldisilazane Containing compounds etc. can be mentioned. When stopping the isocyanurate reaction, sulfuric acid, phosphoric acid, sulfonic acid, etc. are added to deactivate the catalyst. Once the reaction is completed, unreacted diisocyanate and solvent in the reaction mixture can be removed to obtain the desired polyisocyanate. As such polyisocyanates, for example, Japanese Patent Publication No. 64-10023
No., JP-A-2-1718, etc.

The isocyanate groups of the polyisocyanate thus obtained are blocked with a blocking agent. The blocking agent of the present invention is, for example, an active methylene oxime compound. Blocking agents other than those mentioned above are ineffective or have a small effect. Examples of active methylene compounds include acetylacetone, methyl acetoacetate, ethyl acetoacetate, dimethyl malonate, diethyl malonate, and the like. As oxime compounds,
Examples include formaldoxime, acetaldoxime, acetone oxime, methyl ethyl ketoxime, and cyclohexanone oxime, and two or more of them may be used in combination. Particularly preferred are acetone oxime and methyl ethyl ketoxime. A coating film using such a blocked isocyanate as a crosslinking agent has extensibility.

[0022] The polyols used in the present invention include aliphatic hydrocarbon polyols, polyether polyols,
Examples include polyester polyols, epoxy resins, fluorine polyols, and acrylic polyols. Specific examples of aliphatic hydrocarbon polyols include hydroxyl-terminated polybutadiene and hydrogenated products thereof. Examples of polyether polyols include polyether polyols obtained by adding alkylene oxides such as ethylene oxide and propylene oxide alone or as a mixture to polyhydric alcohols such as glycerin and propylene glycol, and polytetra Polyether polyols obtained by reacting methylene glycols and alkylene oxides with polyfunctional compounds such as ethylenediamine and ethanolamine, and so-called polymer polyols obtained by polymerizing acrylamide etc. using these polyethers as a medium. etc. are included.

Examples of polyester polyols include dibasic acids selected from the group of carboxylic acids such as succinic acid, adipic acid, sebacic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, and terephthalic acid. or polyester polyol resins and e.g. Examples include polycaprolactones obtained by ring-opening polymerization of caprolactone using a polyhydric alcohol.

Examples of epoxy resins include novolak type, β-methylepicro type, cyclic oxirane type, glycidyl ether type, glycol ether type, epoxy type of aliphatic unsaturated compounds, epoxidized fatty acid ester type,
Epoxy resins such as polyvalent carboxylic acid ester type, aminoglycidyl type, halogenated type, and resorcin type are mentioned. As fluorine polyols, for example, JP-A-57-
Examples include copolymers of fluoroolefins, cyclohexyl vinyl ethers, hydroxyalkyl vinyl ethers, monocarboxylic acid vinyl esters, etc., which are disclosed in No. 34107, JP-A No. 61-275311, and the like.

Examples of the acrylic polyol include acrylic esters having active hydrogen such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxybutyl acrylate, or acrylic monoester of glycerin. Alternatively, methacrylic acid monoester, trimethylolpropane acrylic acid monoester is used singly or in combination with methacrylic acid monoester, methyl acrylate, ethyl acrylate, isopropyl acrylate, acrylic acid-n-
Acrylic esters such as butyl, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, and methacrylate such as lauryl methacrylate. The essential component is a single or a mixture of acid esters, and unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid, and unsaturated amides such as acrylamide, N-methylolacrylamide, and diacetone acrylamide. , and other polymerizable monomers such as glycidyl methacrylate, styrene, vinyltoluene, vinyl acetate, acrylonitrile, and dibutyl fumarate. Examples include acrylic polyol resins obtained by copolymerizing polyol resins and polymerizable ultraviolet stable monomers exemplified in JP-A-1-261409, JP-A-3-6273, and the like. Particularly preferred among these polyols are the above-mentioned acrylic polyols.

The polyol of the present invention has a resin hydroxyl value of 1
It is 0 to 300 mgKOH/g. Resin hydroxyl value is 1
If it is less than 0, the crosslinking density of the urethane due to the reaction with the isocyanate component decreases, and the function of the urethane bond cannot be exerted, and if the resin hydroxyl value exceeds 300, the crosslinking density increases, This is undesirable because the mechanical properties of the coating film deteriorate, and in some cases, the hydroxyl groups and isocyanate groups do not react completely.

In the thus obtained blocked isocyanate and polyol, the molar ratio of the blocked isocyanate groups in the blocked isocyanate to the hydroxyl groups in the polyol is in the range of 0.4:1 to 2:1. is suitable. Furthermore, various blocked polysocyanates and melamine curing agents can be used in combination depending on the purpose. The block polyisocyanate may be a block of bullet type polyisocyanate (for example, JP-A-55
-144021), isocyanurate-type polyisocyanate blocks (for example, JP-A-55-383
80), urethane-modified isocyanurate-modified isocyanurate-type polyisocyanurate blocks (for example, JP-A-60-149572), and the like. Typical examples of the melamine curing agent include hexamethoxymethylol melamine, methyl butylated melamine, and the like.

The curing accelerator used in the present invention will be described. R of the organotin compound represented by formulas (1) and (2)
1 and R3 are an alkyl group or an aryl group having 1 to 12 carbon atoms, such as a methyl group, a butyl group, an octyl group, a lauryl group, a phenyl group, and the like. Particularly preferred are butyl group and octyl group. R2 is a hydrogen atom or an alkyl group, alkenyl group, aralkyl group, cycloalkyl group, alkoxyalkyl group, or aryl group having 1 to 21 carbon atoms, and -OCOR2 group is a carbon number 2 to 22 carbon group having these R2 groups. It is an acid residue, and its carboxylic acids include, for example, formic acid, acetic acid, caproic acid,
Octylic acid, lauric acid, myristic acid, palmitic acid, behenic acid, neopentanoic acid, neodecanoic acid, acrylic acid, crotonic acid, isocrotonic acid, undecylenic acid, oleic acid, erucic acid, sorbic acid, linoleic acid, linolenic acid, phenylacetic acid , phenylbutyric acid, phenylpropionic acid, cyclopentanecarboxylic acid, acetoacetic acid, benzoic acid, methoxybenzoic acid, tert-butylbenzoic acid,
Examples include hydroxybenzoic acid, acetic acid, octylic acid,
Lauric acid and benzoic acid are preferred.

Examples of the halogens of X and Y include:
Examples include chlorine. As the divalent carboxylic acid residue of Z,
Examples include residues of divalent aliphatic and aromatic carboxylic acids such as adipic acid, maleic acid, and phthalic acid, and sulfur-containing divalent aliphatic carboxylic acids such as thiodipropionic acid. Particularly preferred are bis(dibutyltin monoacetate) oxide, bis(dibutyltin monooctylate) oxide,
Bis(dibutyltin monolaurate) oxide, bis(dibutyltin monobenzoate) oxide, bis(dioctyltin monoacetate) oxide, bis(dioctyltin monooctylate) oxide, bis(dioctyltin monolaurate) oxide, bis(dioctyltin monobenzoate) oxide.

To explain in detail the organic metal salt represented by formula (3) used in the present invention, R4 is a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, an alkenyl group, an aralkyl group, a cycloalkyl group, It is an alkoxyalkyl group or an aryl group, and the -OCOR4 group is a carboxylic acid group having 2 to 22 carbon atoms and having these R4 groups, and examples of the carboxylic acid include formic acid, acetic acid, caproic acid, and octylic acid. , lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, neopentanoic acid, neoheptanoic acid, neodecanoic acid, acrylic acid, crotonic acid, isocrotonic acid, undecylenic acid, oleic acid, erucic acid, sorbic acid, linoleic acid, linolenic acid. acids, phenylacetic acid, phenylbutyric acid, phenylpropionic acid, cyclopentanecarboxylic acid, acetoacetic acid, benzoic acid, methoxybenzoic acid, tert-butylbenzoic acid, hydroxybenzoic acid, etc., preferably acetic acid, octylic acid, lauric acid, benzoic acid. Examples include acids, particularly preferably bis(cobalt monoacetate) oxide, bis(cobalt monooctylate) oxide, bis(cobalt monolaurate) oxide, bis(cobalt benzoate) oxide, and bis(nickel monoacetate) oxide. acetate) oxide, bis(nickel monooctylate) oxide, bis(nickel monolaurate) oxide, bis(nickel monobenzoate) oxide, bis(zinc monoacetate) oxide, bis(zinc monooctylate) oxide, bis(zinc monolaurate) oxide, and bis(zinc monobenzoate) oxide.

The diketone metal complex used in the present invention is
Diketone and cobalt having two >C=O groups in the molecule,
It forms a complex compound with nickel and zinc, and the diketone is represented by the following formula (4).

[0032]

[C7]

Examples of the alkyl groups represented by R5, R6 and R7 in formula (4) include methyl group, ethyl group,
Propyl group, isopropyl group, butyl group, isobutyl group, secondary butyl group, acyl group, neopentyl group,
Isoamyl group, hexyl group, isohexyl group, heptyl group, octyl group, isooctyl group, 2-ethylhexyl group, decyl group, isodecyl group, lauryl group, tridecyl group, stearyl group, cyclopentyl group, cyclohexyl group, cyclooctyl group, cyclododecyl group group, 4-methylcyclohexyl group, and the like. Examples of the aryl group include phenyl group and naphthyl group. Examples of the arylalkyl group include benzyl group, β-
Examples include phenylethyl group and γ-phenylpropyl group. Examples of the alkylaryl group include tolyl group, xylyl group, ethylphenyl group, butylphenyl group,
Examples include tert-butylphenyl group, octylphenyl group, isooctylphenyl group, tert-aryoctylphenyl group, nonylphenyl group, dinonylphenyl group, 2,4-di-tert-butylphenyl group.

Examples of the cycloalkyl group represented by R6 and R7 include a cyclohexyl group and a cyclooctyl group, and examples of the alkoxyaryl group include a methoxyphenyl group, a propoxyphenyl group, and a butoxyphenyl group. β expressed by the preferable formula (4)
-Diketones include cobalt stearoyl benzoylmethane, cobalt dibenzoylmethane, cobalt diacetylmethane, nickel stearoyl benzoylmethane, nickel diacetylmethane, nickel butanoyl methane,
These are acetylmethane, zinc stearoyl benzoylmethane, zinc dibenzoylmethane, zinc diacetylmethane, and zinc butanoyl acetylmethane.

In the present invention, a metal compound of cobalt, nickel and zinc selected from organic metal salts and diketone metal complexes of the formula (3), which are used in combination with the organic compounds of the formulas (1) and (2), and The combined use ratio is 9:1 to 9:1 by weight.
The ratio is 1:9, preferably 1:1 to 2:8. If it is outside this range, excellent catalytic effects will not be exhibited. The amount of cobalt, nickel and zinc metal compounds selected from the organotin compound used in the present invention and the organometallic salts and diketone metal complexes used in combination is not particularly limited, but is usually based on the resin solid content. 0.01 to 10% by weight,
Preferably it is 0.5 to 5% by weight.

In addition, in the composition of the present invention, when mixing the components, a suitable solvent such as benzene, toluene, xylene, cyclohexane, mineral spirits, hydrocarbons such as naphtha, acetone, methyl ethyl ketone, It can be appropriately selected and used depending on the purpose and use from the group of ketones such as methyl isobutyl ketone, and esters such as ethyl acetate, n-butyl acetate, and cellosolve acetate. These solvents may be used alone or in combination of two or more. Further, antioxidants, ultraviolet absorbers, pigments, metal powder pigments, rheology control agents, etc. may be added as necessary.

[0037]

EXAMPLES The present invention will be explained in more detail below based on examples, but the present invention is not limited to the following examples. In addition, in the examples, the blending of blocked isocyanate and polyol is shown in parts by weight. Further, the curing accelerator is expressed in weight % based on the solid content of these blocked isocyanates and polyols. Evaluation was performed according to the following. In addition, the physical properties of the coating film were measured and evaluated using the following method.

(Gel fraction) The gel fraction is defined as the weight of the undissolved portion when the baked and hardened coating is immersed in acetone at 20° C. for 24 hours compared to before immersion. This value was used as an index of coating film forming ability. If this value is less than 50%, it cannot be used as a paint, if it is less than 50 to 85%, it is unsatisfactory as a paint, and if it is 85% or more, it is fully satisfactory. . (Low temperature impact resistance) JIS3141 (SPCC-SB)
DuPont type 1/2 inch x 500g coating film with a film thickness of 30μ applied to a steel plate of 0.8 x 70 x 150 mm
The test was carried out in accordance with JIS 5400 under the conditions of x50 cm (-10°C). The evaluation was rated as ◯ if there were no cracks, △ if there were slight cracks, and × if cracks were generated.

[0039]

[Reference Example 1] (Production of blocked isocyanate) Create a nitrogen atmosphere in a 4-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen blowing tube, and add 1008 g of 1,6-hexamethylene diisocyanate (HMDI). , number average molecular weight 100
PTG100, which is polytetramethylene glycol with
0 (manufactured by Hodogaya Chemical Industry Co., Ltd.) was charged and reacted for 1 hour at a reaction temperature of 100° C. with stirring. The reaction solution thus obtained was heated to a temperature of 160°C using a thin film distillation apparatus.
Distillation was performed at a vacuum degree of 0.2 mmHg to remove unreacted HMDI to obtain polyisocyanate. After creating a nitrogen atmosphere in a 4-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen blowing tube, the obtained polyisocyanate 10
00g, 284g of ethyl acetate was charged, and 135g of butanone oxime was added while stirring and controlling the reaction temperature to below 50°C.
was dripped. It was confirmed that the absorption of isocyanate groups in the infrared spectrum had disappeared.

[0040]

[Reference Example 2] (Production of Blocked Isocyanate) Using the same equipment as in Reference Example 1, after creating a nitrogen atmosphere in the flask, HMDI
792 g of polycaprolactone polyol Plaxel 305 (manufactured by Daicel Chemical Industries, Ltd., trade name, number average molecular weight 550) were charged and reacted at 100° C. for 1 hour with stirring. The reaction solution thus obtained was distilled using a thin film distillation apparatus at a temperature of 160° C. and a degree of vacuum of 0.2 mmHg to remove unreacted HMDI to obtain polyisocyanate. After creating a nitrogen atmosphere in a 4-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen blowing tube, 1000 g of the obtained polyisocyanate and 314 g of ethyl acetate were charged, and the reaction temperature was lowered to 50°C or less while stirring. 254 g of butanone oxime was added dropwise in a controlled manner. It was confirmed that the absorption of isocyanate groups in the infrared spectrum had disappeared.

[0041]

[Reference Example 3] (Production of Blocked Isocyanate) Using the same equipment as in Reference Example 1, after creating a nitrogen atmosphere in the flask, HMDI
300 g of polycaprolactone polyol Plaxel 205 (manufactured by Daicel Chemical Industries, Ltd., trade name, number average molecular weight 550) were charged and reacted at 100° C. for 1 hour with stirring. The reaction solution thus obtained was distilled using a thin film distillation apparatus at a temperature of 160° C. and a degree of vacuum of 0.2 mmHg to remove unreacted HMDI to obtain polyisocyanate. After creating a nitrogen atmosphere in a 4-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen blowing tube, 1000 g of the obtained polyisocyanate and 300 g of ethyl acetate were charged, and while stirring, the reaction temperature was lowered to 50°C or less. 205 g of butanone oxime was added dropwise in a controlled manner. It was confirmed that the absorption of isocyanate groups in the infrared spectrum had disappeared.

[0042]

[Reference Example 4] (Production of Blocked Isocyanate) Using the same equipment as in Reference Example-1, after creating a nitrogen atmosphere in the flask, HMD
1000 g of Duranate 24A (trade name of Asahi Kasei Kogyo Co., Ltd.), which is a polyisocyanate made from I, and 380 g of ethyl acetate were charged, and 511 g of butanone oxime was added dropwise while stirring and controlling the reaction temperature to 50° C. or less. It was confirmed that the absorption of isocyanate groups in the infrared spectrum had disappeared.

[0043]

[Examples 1 to 6] The blocked isocyanate synthesized in the reference example was used, and the polyol was acrylic polyol manufactured by Dainippon Chemical Co., Ltd., non-volatile content 50%, hydroxyl value 50 mgKO.
The compositions of the present invention were obtained by blending as shown in Table 1 using H/g. Applicator coating was performed using this composition. After setting at room temperature for 30 minutes, baking was performed at 120°C for 30 minutes. Table 1 shows the results of the above evaluation method.

[0044]

[Comparative Examples 1 to 5] Using the block isocyanate synthesized in the reference example, Comparative Examples 1 to 3 and 5 are acrylic polyols manufactured by Dainippon Chemical Co., Ltd. with non-volatile content of 50% and hydroxyl group price of 50 mgKOH/g. 4 is Asahi Denka Co., Ltd.
Polyether polyol hydroxyl group price 450mgKOH/
g was blended as shown in Table 2 to obtain a composition. Applicator coating was performed using this composition. After setting at room temperature for 30 minutes, baking was performed at 120°C for 30 minutes. Table 2 shows the results of the above evaluation method.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

Effects of the Invention According to the present invention, compared to conventional non-yellowing one-component polyurethane paints mainly composed of polyols and blocked isocyanates, it is possible to By combining metal compounds, the crosslinking temperature of the paint can be lowered. That is, not only low-temperature curing becomes possible, but also coating film properties particularly excellent in flexibility, impact resistance, and adhesion at low temperatures can be obtained.

Claims (1)

[Claims] [Claim 1] (A) Blocking the isocyanate groups of a polyisocyanate consisting of a diisocyanate that is a diisocyanate or a mixture of a diol and/or triol having a number average molecular weight of 500 to 1,600 and an aliphatic or alicyclic diisocyanate. (B) a polyol with a resin hydroxyl value of 10 to 300 mgKOH/g, and (C) the following formula (1), and the following (2)
) at least one type of organotin compound represented by the formula;
A low-temperature curable film having flexibility and weather resistance, the main component of which is a curing accelerator consisting of at least one metal compound selected from organic acid metal salts and diketone metal complexes represented by the following formula (3). Liquid paint composition. [Chemical formula 1] [Chemical formula 2] [Chemical formula 3]