JP3076622B2 - Water-based block isocyanate composition having isocyanurate structure and coating composition using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates also relates to a non-yellowing type aqueous block isocyanate composition, more particularly, weather resistance,
The present invention relates to a block isocyanate composition which can provide a coating film having excellent chemical resistance, chipping resistance and the like, and is extremely useful as a coating material for automobiles, buildings, electric appliances and the like, and a coating composition using the same.

[0002]

2. Description of the Related Art Aqueous block isocyanates are widely used as crosslinking agents and modifiers. There are roughly two types of such block isocyanates,
In the art, it is called a yellowing type polyisocyanate compound or a non-yellowing type polyisocyanate compound. The yellowing-type polyisocyanate compound is obtained by using toluene diisocyanate, diphenyl metadiisocyanate or the like as a raw material, and has a drawback that yellowing is caused by heat, light, or the like. On the other hand, those using a non-yellowing type polyisocyanate compound as a raw material have significantly less yellowing due to heat, light and the like. However, in order to further improve the stability against heat, light, and the like, the structure of the isocyanate must be considered. That is, in the non-yellowing type block isocyanate, generally, the blocking agent is dissociated at a high temperature, the active isocyanate group is regenerated, and the active isocyanate is bonded to form a crosslink. Therefore, isocyanates must withstand this high temperature. The thermal stability of the various bonds associated with the isocyanate group is said to be isocyanurate>urea>urethane>buret> allophanate. Therefore, it is preferable that the polyisocyanate compound has an isocyanurate structure, and JP-A-2-620 discloses a block isocyanate having an isocyanurate structure. In addition, some techniques for making aqueous block isocyanates having an isocyanurate structure have been proposed. JP-A-62-151419 proposes making block isocyanate aqueous by imparting water dispersing ability to a part of the polyisocyanate group.
However, this method consumes a significant proportion of the isocyanate groups, resulting in a significant reduction in the cross-linking capacity of the polyisocyanate. Further, JP-A-1-135 discloses that an ionic group having a crosslinking ability is introduced into an isocyanate compound.
760 publication. However, in this technique, urethane bonds showing good physical properties are finally reduced.

[0003]

Accordingly, realization of an aqueous block isocyanate having an isocyanurate structure in the molecule and sufficient cross-linking ability without reducing the finally formed urethane bond. Was waiting.

[0004]

The present invention solves the above-mentioned problems by making a specific block isocyanate aqueous under specific conditions. That is, the present invention is a block isocyanate completely blocked isocyanate group of hexamethylene diisocyanate polyisocyanate containing isocyanurate structure in the molecule,
A protective colloid agent as an aqueous-forming aid, an aqueous-based block isocyanate composition containing water as a main component as a medium ,
And resin hydroxyl value 10 to 300, number average molecular weight 20
Water-friendly polyol of 00 to 50,000, as curing agent
The aqueous block isocyanate composition described above
It is intended to provide a coating composition characterized by being a component .

The aqueous block isocyanate group of the present invention
The composition is a block aqueous hydrate of polyisocyanate having an isocyanurate structure. The polyisocyanate having an isocyanurate structure used here is hexamethylene diisocyanate (hereinafter referred to as HMDI).
Is synthesized from the raw materials. When synthesizing a polyisocyanate having an isocyanurate structure, the polyisocyanate may be modified with a hydroxyl compound.

Examples of the hydroxyl compound include monohydroxy compounds such as methanol, ethanol, isopropanol and phenol, ethylene glycol, propylene glycol, 1,3-butanediol, pentanediol, hexanediol, cyclohexanediol, and the like.
Neopentyl glycol, 2,2,4-trimethyl 1,
There are dihydroxyl compounds such as 3-pentanediol. These may be used alone or in combination of two or more.

A catalyst is usually used for the isocyanuration reaction. The catalyst used here is generally preferably basic, and examples thereof include quaternary ammonium salts, their weak organic salts, alkyl metal salts of alkyl carboxylic acids, metal alcoholates, and compounds containing an aminosilyl group. The catalyst concentration is usually selected from the range of 10 ppm to 1.0% based on the isocyanate compound.

The reaction may or may not use a solvent. If a solvent is used, a solvent inert to the isocyanate group should be used. The reaction temperature is usually 20 to
160 ° C., preferably 40 to 120 ° C. When the reaction reaches the target conversion, the reaction is stopped by deactivating the catalyst with, for example, sulfonic acid, phosphoric acid, or the like.

The unreacted substances and the solvent are removed to obtain a polyisocyanate compound having an isocyanurate structure. The polyisocyanate having an isocyanurate structure thus obtained becomes a blocked isocyanate by blocking the isocyanate group with a blocking agent. Examples of the blocking agent include phenol-based, alcohol-based, active methylene-based, mercaptan-based, acid amide-based, acid imide-based, imidazole-based, urea-based, oxime-based, amine-based imine-based, and the like. You may mix and use. More specific blocking agents are shown below. (1) phenol type; phenol, cresol, ethyl phenol, butyl phenol, etc., (2) alcohol type: ethylene glycol, benzyl alcohol, methanol, ethanol, etc., (3) active methylene type: dimethyl malonate, diethyl malonate, acetoacetic acid Methyl, ethyl acetoacetate, acetylacetone, etc. (4) mercaptan type; butyl mercaptan, dodecyl mercaptan etc. (5) acid amide type: acetanilide, acetate amide, ε-
Caprolactam, δ-valerolactam, γ-butyrolactam, etc. (6) acid imides; succinimide, maleic imide, etc .; (7) imidazoles; imidazole, 2-methylimidazole, etc .; (8) oxime type; formaldoxime, acetoaldoxime, methyl ethyl ketoxime, cyclohexanone oxime, etc. (10) carbamic acid type; phenyl N-phenylcarbamate, etc .; (11) amine type; diphenylamine Aniline, carbazole, etc .; (12) imine series; ethyleneimine, polyethyleneimine, etc., dimethyl malonate, diethyl malonate,
Active methylene systems such as methyl acetoacetate, ethyl acetoacetate, and acetylacetone, and oxime systems such as methyl ethyl ketoxime are preferred.

The blocking reaction can be performed with or without a solvent. When a solvent is used, it is necessary to use a solvent inert to the isocyanate group. At the time of the blocking reaction, an organic metal salt such as tin, zinc, or lead and a tertiary amine may be used as a catalyst. The reaction can be generally carried out at -20 to 150 ° C, but preferably at 0 to 100 ° C. If the temperature is higher than 100 ° C., a side reaction may occur. On the other hand, if the temperature is too low, the reaction rate is reduced, which is disadvantageous. Preferably, substantially all of the isocyanate groups are blocked. The isocyanate group that is not blocked reacts with water or the like during storage and cannot participate in crosslinking at the time of forming a coating film.

In the present invention, a protective colloid is used to make the block isocyanate aqueous. Examples of protective colloids include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, block partially saponified polyvinyl alcohol, polyvinylpyrrolidone, methylcellulose, hydroxyethylcellulose or hydroxypropylcellulose, methylhydroxycellulose, carboxymethylcellulose, gelatin, starch paste, acrylic acid Polymers, methacrylic acid polymers, etc., among which polyvinyl alcohol is particularly preferred. In particular, partially saponified and block partially saponified polyvinyl alcohols are preferable, and further, the number average molecular weight is from 5,000 to
Polyvinyl alcohol of 300,000 and a saponification rate of 90% or less is preferred.

These protective colloid agents may be used alone or in combination of two or more. The amount of the protective colloid used is 0.1 to 30%, preferably 0.5 to 20%, based on the block isocyanate compound. The aqueous conversion of the block isocyanate is adjusted by emulsifying or dispersing the block isocyanate in water using a protective colloid agent as an aqueous conversion aid.

In this case, the supply form of the block isocyanate may be such that the organic solvent used in the reaction may be removed, or the block isocyanate may be dissolved in the organic solvent. Further, an organic solvent may be added. The aqueous block isocyanate composition of the present invention is adjusted by a usual emulsifying method, a dispersing method, or the like, and the apparatus is, for example, a homomixer or a homogenizer. The solid content concentration of the aqueous block isocyanate composition thus adjusted is usually from 10 to 80.
%.

The aqueous block isocyanate composition thus adjusted is mixed with a water-affinity polyol to form a coating composition. The water-affinity polyol used in the present invention can be used without any particular limitation as long as it is usually used for water-based paints, and anionic, cationic, amphoteric, and also have no ionicity. It may be something. There are alkyd type, polyester type, epoxy type, fluorine type, acrylic type and the like. The resin hydroxyl value is 10 to 300, and the number average molecular weight is 2,000 to 50,000.
Which is dissolved or dispersed in a dispersion medium containing water as a main component. If the resin hydroxyl value is less than 10, the urethane crosslink density due to the reaction with the isocyanate component decreases, and the physical properties of the present invention cannot be achieved. If the resin hydroxyl value exceeds 300, on the contrary, The crosslinking density increases, and the mechanical properties of the coating film decrease, which is not preferable. Examples of the soluble polyol include JP-A-63-295680.
JP-A-63-175059, JP-A-63-175059
JP-A-216671, JP-A-2-191692, and the like disclose a manufacturing method thereof. JP-A-56-157358 discloses a method for producing a dispersion type polyol. As a fluorine polyol which is a fluorine copolymer having a hydroxyl group, JP-A 57-3
No. 4,107, JP-A-61-231044, JP-A-3-37252, and the like disclose the manufacturing method. In the present invention, preferred water-affinity polyols are disclosed in JP-A-63-295680 and JP-A-63-1.
An acrylic resin disclosed in, for example, Japanese Patent No. 75059, Japanese Patent Application Laid-Open No. 56-157358, and the like.

[0015] In the coating composition of the present invention, the molar ratio of the resin component hydroxyl latent isocyanate groups with water affinity polyol aqueous block isocyanate composition used as the curing agent is usually 0.5 to 2.5 Is set. As the curing agent, a melamine-based curing agent can be used in combination. In this case, the ratio is usually 0.1 to 1.5.
Representative examples of the melamine-based curing agent include hexamethoxymethylolmelamine, methyl-butylated melamine, and the like.

If necessary, an antioxidant, an ultraviolet absorber, a pigment, a metal powder pigment, a crosslinking accelerator, a leveling agent,
Water, a solvent and the like may be added. The coating composition adjusted in this way is applied to metal, plastic, etc. by a method such as spray coating, roll coating, shower coating, electrodeposition coating, dip coating, and is also useful as a chipping-resistant coating, a coating for pre-coated metal, and the like. is there.

[0017]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples. In addition, evaluation was performed as follows. (Gel fraction) The value of the weight of the undissolved portion when the cured coating film was immersed in acetone at 20 ° C. for 24 hours was 50% of that before immersion.
Less than x was evaluated, 50 or more and less than 85% was evaluated as Δ, and 85% or more was evaluated as ○. (Adhesion) Cross cut test Based on JIS5400, evaluation was shown as follows.

×: 0 to 25/100 Δ: 2
6 to 75/100 ○: 76 to 100/100 (impact resistance) JIS3141 (SPCC-SB) 0.8
A coating film having a thickness of 30 μm applied to a steel plate of × 70 × 150 mm (manufactured by Nippon Test Panel Co., Ltd.) is JIS 5 under the conditions of DuPont type 1/2 inch × 500 g × 50 cm.
400. The evaluation was as follows: No crack: O, slight crack generation: Δ, crack generation: X. (Haze Value of Coating Film) A coating film having a thickness of 30 μm applied to a transparent glass plate having a thickness of 1 m / m was measured by a direct reading haze computer HGM-2DP of Suga Test Instruments Co., Ltd. to have a value of 1.0. Less than was evaluated as ○, and 1.0 or more was evaluated as x. (Boiling water resistance) A 30 μm-thick coated film applied on a transparent glass plate having a thickness of 1 m / m is immersed in boiling water for 2 hours,
The blister of the coating film was visually observed. No blistering was evaluated as ○, and blistering was evaluated as x. (Chemical resistance) A coating film having a thickness of 30 μm applied to a white tile board was immersed in 40% sulfuric acid at 40 ° C. for 3 hours, and then dried.
0: The gloss retention was evaluated as x when it was less than 50%, Δ when it was 50% or more and less than 90%, and ○ when it was 90% or more.

[0019]

Example 1 (Production of aqueous block isocyanate composition ) In a four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, a polyisocyanate compound having an isocyanurate structure using HMDI as a raw material (Asahi Kasei Kogyo Co., Ltd. Was dissolved in 37 parts of ethyl acetate, and then 48 parts of butanone oxime was added to 40 to 50 parts of the mixture.
In the range of ° C., it was added dropwise over 2 hours. It was confirmed by infrared spectrum that the absorption of the isocyanate group had disappeared.

Using a homomixer (M type, manufactured by Tokushu Kika Kogyo Co., Ltd.), 100 parts of the obtained product was subjected to rotation at 3000 rpm.
While stirring at rpm, partially saponified polyvinyl alcohol (trade name PVA-420 of Kuraray Co., Ltd., saponification degree 79.
5 mol%, polymerization degree 2000)
Add over minutes and stir for 10 minutes. Then water 88
Was added over 10 minutes and stirring was continued for 10 minutes. As a result, an aqueous block isocyanate composition having a solid content of 30% and a viscosity of 40 cp (20 ° C.) was obtained. This dispersion was stable without phase separation and the like even after one month of production.

[0021]

Example 2 (Production of aqueous block isocyanate composition ) A urethane-modified polyisocyanate compound having an isocyanurate ring structure using HMDI as a raw material (trade name of Asahi Chemical Industry Co., Ltd.) in the same apparatus as in Example 1 Duranate TH
A) After dissolving 100 parts of ethyl acetate in 36 parts of ethyl acetate, 44 parts of butanone oxime was added dropwise at 40 to 50 ° C over 2 hours. It was confirmed by infrared spectrum that the absorption of the isocyanate group had disappeared.

Using a homomixer (M type manufactured by Tokushu Kika Kogyo Co., Ltd.), 100 parts of the obtained product was rotated at 3000 rpm.
5% aqueous solution of partially saponified polyvinyl alcohol (trade name: PVA-420 of Kuraray Co., Ltd.) 8 while stirring at rpm
Add 0 parts over 10 minutes and stir for 10 minutes. Thereafter, 88 parts of water was added over 10 minutes, and stirring was continued for 10 minutes. As a result, the solid content was 30% and the viscosity was 40 cp (20
C) of the aqueous block isocyanate composition . This dispersion was stable without phase separation and the like even after one month of production.

[0023]

Example 3 (Production of aqueous block isocyanate composition ) In the same apparatus as in Example 1, a polyisocyanate compound having an isocyanurate structure using HMDI as a raw material (Duranate TPA, trade name of Asahi Chemical Industry Co., Ltd.) After dissolving 100 parts in 37 parts of ethyl acetate, butanone oxime 4
Eight parts were added dropwise in the range of 40 to 50 ° C. over 2 hours.
It was confirmed by infrared spectrum that the absorption of the isocyanate group had disappeared.

Using a homomixer (M type, manufactured by Tokushu Kika Kogyo Co., Ltd.), 100 parts of the obtained product was rotated at 3000 rpm.
While stirring at rpm, partially saponified polyvinyl alcohol (Kuraray Co., Ltd. PVA-205, saponification degree 88 mol%,
80 parts of a 5% aqueous solution is added over 10 minutes and stirred for 10 minutes. Thereafter, 88 parts of water was added over 10 minutes, and stirring was continued for 10 minutes. As a result, an aqueous block isocyanate composition having a solid content of 30% and a viscosity of 30 cp (20 ° C.) was obtained. This dispersion was stable without phase separation and the like even after one month of production.

[0025]

Examples 4 to 6 (Evaluation by Coating Film) Water-affinity acrylic polyol neutralized with dimethylethanolamine (trade name: Almatex WA911, Mitsui Toatsu Co., Ltd., number average molecular weight: 6000, resin hydroxyl value: 4)
0 mgKOH / g) and the aqueous block isocyanate compositions obtained in Examples 1 to 3 in a solid content ratio of 100: 15.
And mixed so that Further, water was added, and the viscosity of the paint was changed to Ford Cup No. 4 was adjusted to 30 seconds.
This paint was applied by an applicator and cured at 160 ° C. for 20 minutes. Table 1 shows the results of the coating film evaluation.

[0026]

Example 7 Aqueous block isocyanate composition obtained in Example 1 using water-affinity acrylic polyol neutralized with diethanolamine (trade name “Almatex WA911” of Mitsui Toatsu Co., Ltd.) The product is 1 in solid content ratio
00: 7.5, melamine resin (trade name: Cymel 350, trade name of Mitsui Toatsu Co., Ltd.) was mixed at a solid content ratio of 100: 13. Water was further added, and the viscosity of the paint was Ford Cup No. 4. The coating was applied by an applicator and cured for 20 minutes at 160 ° C. The coating film evaluation results are shown in Table 1.

[0027]

[Comparative Example 1] (Production of aqueous block isocyanate composition and evaluation by coating film) In the same apparatus as in Example 1, a urethane-modified polyisocyanate compound having an isocyanurate ring structure using HMDI as a raw material (Asahi Kasei Kogyo Co., Ltd.) ) Brand name duranate TH
A) After dissolving 100 parts in 33 parts of ethyl acetate, 33 parts of butanone oxime was added dropwise at 40 to 50 ° C over 2 hours. Then, the temperature in the flask was raised to 65 ° C., 8.4 parts of dimethylolpropionic acid was added, and the mixture was maintained for 10 hours. Thereafter, 6 parts of triethylamine was added, and
Hold for 0 minutes. Further, 32 parts of n-methylpyrrolidone was added and mixed well. 50 parts of water was added to 50 parts of the obtained aqueous block isocyanate composition , and the pH was adjusted to 8.3 with triethylamine. The water-soluble block isocyanate composition thus obtained and a water-affinity acrylic polyol neutralized with dimethylethanolamine (trade name: Almatex WA911, manufactured by Mitsui Toatsu Co., Ltd.) were used at a solid content ratio of 22 to 100. Mixed. Add more water and paint viscosity
Ford Cup No. 4 was adjusted to 30 seconds. This paint was applied by an applicator and cured at 160 ° C. for 20 minutes. Table 1 shows the results of the coating film evaluation.

[0028]

Comparative Example 2 Water-affinity acrylic polyol neutralized with dimethylethanolamine as in Example 4 (trade name "Almatex WA-911" of Mitsui Toatsu Chemicals, Inc.)
And a melamine resin (trade name “Cymel 350” of Mitsui Toatsu Chemicals, Inc.) were mixed at a solid content ratio of 100: 25. Further add water and paint viscosity is Ford Cup N
o. 4 was adjusted to 30 seconds. This paint was applied by an applicator and cured at 160 ° C. for 20 minutes.
Table 1 shows the results of the coating film evaluation.

[0029]

[Application example] (Application example as a metallic paint) 100 parts of a water-affinity acrylic polyol (trade name "Almatex WA911" of Mitsui Toatsu Co., Ltd.) neutralized with dimethylethanolamine, 4.3 parts of aluminum paste (Trade name of Asahi Kasei Metals Corporation "AW-500B")
And the aqueous block isocyanate set obtained in Example 1
The product was mixed to a solids ratio of 100: 15.
Further, water was added, and the viscosity of the paint was changed to Ford Cup No. 4 was adjusted to 30 seconds. This paint was spray-coated, preheated at 80 ° C. for 2 minutes, and then an acrylic melamine clear coat was further applied thereon. For the clear coat, Acrydic 44-179 (trade name of Dai Nippon Ink Co., Ltd.) and Super Beckamine J-820 (trade name of Dai Nippon Ink Co., Ltd.) are mixed at a weight ratio of 4: 1 and diluted with xylene. The paint viscosity is Ford Cup No. 4 in 3
It was adjusted to 0 seconds and spray painted. Room temperature 30
After the minute setting, the composition was cured at 160 ° C. for 20 minutes.
A flopping property measured by a gonio colorimeter VC-1 manufactured by Suga Test Instruments Co., Ltd. was 1.35, and a metallic coating film having a 60-degree specular gloss of 99% was obtained.

[0030]

[Table 1]

[0031]

According to the present invention, there is provided an aqueous block isocyanate composition which is stable to heat, light and the like, has good urethane bond function, has sufficient crosslinking ability, and a coating composition using the same. In the industrial fields such as automobiles, construction, and electrical products, it only exhibits excellent weather resistance, chemical resistance, in other words, acid rain resistance, impact resistance, etc. as a normal transparent or colored water-based paint. In addition, it has outstanding performance as a chipping-resistant paint, a paint for pre-coated metal, particularly a so-called water-based metallic paint to which metal powder is added.

Claims (2)

(57) [Claims] 1. A block isocyanate obtained by completely blocking an isocyanate group of a hexamethylene diisocyanate-based polyisocyanate containing an isocyanurate structure in a molecule, a protective colloid agent as an aqueous-forming aid, and water as a medium. Aqueous block isocyanate as a component
Composition . 2. A water-soluble block isocyanate composition according to claim 1 as a curing agent, wherein the water-soluble polyol having a resin hydroxyl value of 10 to 300 and a number average molecular weight of 2,000 to 50,000 is used as a main component. Paint composition.