JP3324100B2 - Blocked isocyanate curing agent composition and coating composition using the curing agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blocked isocyanate curing agent composition for paints and a paint, and more particularly to a blocked isocyanate curing excellent in smoothness, adhesion, abrasion resistance and impact resistance. The present invention relates to an agent composition and a coating composition using the curing agent composition.

[0002]

2. Description of the Related Art Metal coatings for aircraft, vehicles, various machines, electrical equipment, household goods and the like are usually applied in the order of undercoat, intermediate coat, and top coat, and are baked. Crosslinked alkyd resins and acrylic resins are well known.

[0003]

However, these melamine crosslinked types have poor acid resistance. Therefore, development of a one-pack baking coating using a blocked isocyanate is desired. A block isocyanate sufficient in terms of crosslinkability and various properties has not been proposed.

[0004]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that they have excellent compatibility with various resins, excellent crosslinkability, and excellent smoothness, adhesion, abrasion resistance and impact resistance. The present inventors have found a blocked isocyanate curing agent and a paint and have reached the present invention. That is, the present invention relates to hexamethylene diisocyanate (hereinafter abbreviated as HDI) and a number average molecular weight of 300 to 500.
0 to 80% by weight of an isocyanate group-terminated prepolymer (A), 10 to 30% by weight of a cyclic trimerization oligomer of HDI (B) and 10 to 30% by weight of a blocking agent (C). The present invention relates to a blocked isocyanate curing agent composition and a coating composition comprising the blocked isocyanate curing agent and an active hydrogen-containing resin.

The number average molecular weight used in the present invention is 300 to 50.
As the polyol of 00, polyester polyol,
Polyether polyol, polycarbonate polyol and polyolefin polyol are exemplified. Preferably, the number average molecular weight is 300-3000. Polyester polyols include succinic acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, phthalic anhydride, isophthalic acid, terephthalic acid, maleic acid, tricarboxylic acids such as fumaric acid, trimellitic acid, and pyromellitic acid. And tetracarboxylic acid and ethylene glycol, diethylene glycol, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,9- Polycondensation reaction products with diols such as nonanediol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol, and triols such as trimethylolpropane or cyclic lactones such as ε-caprolactone and δ-valerolactone are used as ethylene glycol. , Diethylene glyco , Neopentyl glycol, glycerin, trimethylolpropane, etc. as an initiator.

As the polyether polyol, a polyether polyol obtained by adding ethylene oxide to a low molecular weight polyol such as ethylene glycol, propylene glycol, bisphenol A, trimethylolpropane, or glycerin, or ethylene oxide is added after adding propylene oxide. Examples of the obtained polyether polyol include polyoxytetramethylene glycol obtained by ring-opening polymerization of tetrahydrofuran.

[0007] Polycarbonate polyols are generally prepared by the decondensation reaction of polyhydric alcohol and diethyl carbonate with ethanol, the dephenol condensation reaction of polyhydric alcohol with diphenyl carbonate, or the ethylene glycol condensation reaction of polyhydric alcohol with ethylene carbonate. The resulting polyhydric alcohol includes 1,6-hexanediol, diethylene glycol, propylene glycol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 1,5-pentanediol, neopentyl glycol, Aliphatic diols such as 1,8-octanediol, 1,9-nonanediol and 1,10-decanediol, or alicyclic diols such as 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol Polycarbonate polyols consisting Lumpur is used. Examples of the polyolefin polyol include a hydroxyl-terminated polybutadiene, a hydrogenated product thereof, and a castor oil-modified polyol. These polyols can be used alone or as a mixture.

[0008] Isocyanate-terminated prepolymer (A)
Can be obtained by reacting these polyols with HDI in an NCO excess, but the production method is not particularly limited, such as a solvent or solventless reaction. Preferred isocyanate group-terminated prepolymers include a reaction product of a polyester polyol obtained by ring opening of a cyclic lactone and HDI from the viewpoint of low viscosity and good adhesion.

As the cyclic trimerization oligomer of HDI (B) in the present invention, HDI may be a known trimerization catalyst, for example, triethylamine, N-methylmorpholine, 2,2
4,6-tris (dimethylaminomethyl) phenol,
Tertiary amines such as 2,4,6-tris (dialkylaminoalkyl) hexahydro-S-triazine; phosphines represented by triethylphosphine; alkali metal salts such as lorium acetate and potassium 2-ethylhexanoate; It is obtained by using and polymerizing. In addition,
To improve the compatibility of the oligomer (B), it is also possible to trimerize using HDI partially urethanized with a polyol in advance. A specific example of the production method is disclosed in JP-A-57-47319.

The polyol for partial urethanization includes ethylene glycol, diethylene glycol, 1,3-butanediol, 1,4-butanediol, propylene glycol, dipropylene glycol, neopentyl glycol, 1,6-hexanediol, and 3-methyldiol. -1,5
-Pentanediol, butylethylpropanediol,
Glycerin, trimethylolethane, trimethylolpropane and the like can be used. In this case, the content of the polyol for partial urethane formation in the oligomer (B) is 20.
% By weight or less is preferred. The NCO content of the oligomer (B) can be used in the range of 17.0 to 23.5% by weight. Examples of the blocking agent (C) that can be used in the present invention include alcohols such as methanol, ethanol, propanol, isopropanol, n-butanol and t-butanol, phenols such as phenol, cresol and xylenol, ε-caprolactam, and δ. Lactams such as valerolactam; oximes such as acetoxime, methyl ethyl ketoxime, methyl isobutyl ketoxime and cyclohexanone oxime; active methylene compounds such as methyl acetoacetate, ethyl acetoacetate and diethyl malonate. Particularly preferred blocking agents from the viewpoint of low-temperature dissociation are oximes and / or active methylene compounds. The weight ratio of (A) :( B) :( C) is 50 to
When the ratio of the component (A) is more than the above ratio and the ratio of the component (B) is too small, the surface smoothness is poor. On the contrary, the component (A) is less than the above ratio. If the ratio of the component (B) is too large, the impact resistance and the scratch resistance are deteriorated. The blocking agent (C) comprises the component (A)
The active hydrogen of the blocking agent and the total NCO groups of the component (B) and the active hydrogen are used in a weight equivalent to 10 to 30% by weight. If the amount is less than 10% by weight, the crosslinking property becomes poor and 3
If the content is more than 0% by weight, the amount of blocks scattered during baking is too large, and a coating film having good appearance cannot be obtained.

The blocked isocyanate curing agent of the present invention can be used as a solventless type or a solvent type. As the solvent, for example, toluene, aromatic solvents such as xylene, methyl ethyl ketone, methyl isobutyl ketone,
Ketone solvents such as cyclohexanone, ester solvents such as ethyl acetate, butyl acetate and isobutyl acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, 3-methyl-3-methoxybutyl acetate, ethyl-3-ethoxypropio One or two or more glycol ether ester solvents such as acrylates and ether solvents such as tetrahydrofuran and dioxane can also be used.

The active hydrogen-containing resin used in the paint of the present invention has a molecular weight of 500 to 100,000. Saturated or unsaturated polyester resin, polycaprolactone resin,
Saturated or unsaturated oil-modified or fatty acid-modified alkyd resin, amino alkyd resin, polycarbonate resin,
Acrylic resin, polyether resin, epoxy resin, polyurethane resin, cellulose acetate butyrate resin,
Fluorinated resins and the like can be mentioned. The amount of the active hydrogen-containing resin used is such that the molar ratio of all isocyanate groups when the blocking agent in the blocked isocyanate curing agent is dissociated to the active hydrogen in the active hydrogen-containing resin is 9: 1 to 1: 9.
Range. Preferably it is 7: 3 to 3: 7.

The coating composition of the present invention may contain various additives such as a dissociation / hardening promoting catalyst antioxidant, an ultraviolet absorber, a plasticizer, a leveling agent, and various pigments, if necessary. A coating compounded with the blocked isocyanate curing agent of the present invention can be applied by a normal coating method,
For example, coating can be performed using an airless spray machine, an electrostatic coating machine, a dip roll coating machine, or the like. The baking conditions are preferably from 120 to 170C for 10 to 30 minutes. Since the coating obtained from the blocked isocyanate curing agent of the present invention is flexible and has excellent impact resistance and scratch resistance, it is particularly suitable as an intermediate coating for aircraft, vehicles and the like, and particularly suitable for metals.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention should not be construed as being limited by these Examples. In the examples and comparative examples, “parts” and “%” indicate “parts by weight” and “% by weight” unless otherwise specified.

Example 1 A reaction vessel was charged with 10.9 parts of HDI, 44.8 parts of polycaprolactone diol having a number average molecular weight of 1,000 using ethylene glycol as a ring-opening initiator, and 10.0 parts of toluene. Allowed to react for hours. The obtained isocyanate group-terminated prepolymer has a solid content of 85% and NCO
The content was 2.5%. To this were added 10.9 parts of coronate HX (manufactured by Nippon Polyurethane Industry, solid content 100%, NCO content 21.2%), which is a cyclic trimerization of HDI, and 15.0 parts of toluene. After uniform mixing, MEK oxime 8. 4
The reaction was conducted at 50 ° C. for 2 hours, and the disappearance of the NCO group was confirmed by infrared absorption spectrum (IR).
The effective NCO of the obtained blocked isocyanate curing agent (A-1) is 4.0%, the solid content is 75%, and the viscosity is 1300.
mPa · s / 25 ° C.

Example 2 In a reaction vessel, 13.9 parts of HDI and a number average molecular weight of 3 obtained by polycondensation of neopentyl glycol and adipic acid were used.
Ε-caprolactam was further added to the polyester diol of No. 00 to obtain 41.4 parts of a polycaprolactone diol having a number average molecular weight of 1,000, and butyl acetate 1
0 parts were charged and reacted at 80 ° C. for 2 hours. The resulting prepolymer had an NCO content of 5.3% and a solids content of 85%. Next, 8.2 parts of Coronate HX was added and mixed uniformly, and then 16.5 parts of ethyl acetoacetate was added and reacted at 80 ° C. for 24 hours, and 10 parts of butyl acetate was added to obtain a blocked isocyanate curing agent (A-2). The effective NCO of the blocked isocyanate curing agent (A-2) was 5.2%, the solid content was 80%, and the viscosity was 2500 mPa · s / 25 ° C.

Example 3 15.5 parts of HDI, 42.7 parts of polycaprolactone diol (same as in Example 1), toluene 10.
0 parts were charged and reacted at 80 ° C. for 2 hours. The solid content of the obtained isocyanate group-terminated prepolymer is 85% and NC
The O content was 6.1%. To this, Coronate HX 5.5
After adding 15.0 parts of toluene and mixing uniformly, 11.3 parts of MEK oxime was added, and the mixture was reacted at 50 ° C. for 2 hours.
It was confirmed at R that the NCO group had disappeared. Effective N of the obtained blocked isocyanate curing agent (A-3)
CO is 5.3%, solid content is 75%, viscosity is 2000mPa.
s / 25 ° C.

Example 4 In a reaction vessel, 11.6 parts of HDI, 34.9 parts of polycaprolactone diol (same as in Example 1), 10 parts of toluene.
0 parts were charged and reacted at 80 ° C. for 2 hours. The obtained isocyanate group-terminated prepolymer has a solid content of 82% and NC
The O content was 5.0%. Add Coronate HX15.
After adding 5 parts and 15.0 parts of toluene and mixing uniformly, MEK
13.0 parts of oxime was added and reacted at 50 ° C. for 2 hours,
It was confirmed by IR that the NCO group had disappeared. The effective NCO of the obtained blocked isocyanate curing agent (A-4) is 6.1%, the solid content is 75%, and the viscosity is 800 mPa ·
s / 25 ° C.

Comparative Example 1 In a reaction vessel, 17.4 parts of HDI, 45.2 parts of polycaprolactone diol (same as in Example 1) and 10.1 parts of toluene.
0 parts were charged and reacted at 80 ° C. for 2 hours. The solid content of the obtained isocyanate group-terminated prepolymer is 86% and NC
The O content was 6.7%. Coronate HX1.4
And 15.0 parts of toluene, and after mixing uniformly, 11.0 parts of MEK oxime was added and reacted at 50 ° C. for 2 hours.
It was confirmed at R that the NCO group had disappeared. Effective N of the obtained blocked isocyanate curing agent (B-1)
CO is 5.1%, solid content is 75%, viscosity is 4000mPa.
s / 25 ° C.

Comparative Example 2 6.0 parts of HDI, 23.8 parts of polycaprolactone diol (same as in Example 1) and 10.0 parts of toluene were placed in a reaction vessel.
The mixture was charged and reacted at 80 ° C. for 2 hours. The obtained isocyanate group-terminated prepolymer has a solid content of 75% and NCO
The content was 2.5%. Coronate HX 29.8
After adding 15.0 parts of toluene and mixing uniformly, 15.4 parts of MEK oxime was added, and the mixture was reacted at 50 ° C. for 2 hours.
It was confirmed at R that the NCO group had disappeared. Effective N of the obtained blocked isocyanate curing agent (B-2)
CO is 7.3%, solid content is 75%, viscosity is 1200mPa.
s / 25 ° C.

Preparation of paint and test of coating Example 5 The blocked isocyanate curing agent (A) obtained in Example 1
-1) 23.6 parts of acrylic polyol (Acrydic A-801, manufactured by Dainippon Ink and Chemicals, hydroxyl value 51)
(mgKOH / g) 24.6 parts, 31.8 parts of toluene, 20.0 parts of titanium oxide, 100 parts of glass beads having a diameter of 2 mm were further mixed, and dispersed for 60 minutes using a paint shaker. . The paint was applied to a bonderite-treated steel sheet by an air sprayer so that the dry film thickness became 50 μm. Then, after standing at 20 ° C. and 60% RH for 30 minutes and baking at 150 ° C. for 20 minutes, adhesion, pencil hardness, impact resistance and gloss were tested. Table 1 shows the results.

Example 6 20.3 parts of the curing agent (A-2) obtained in Example 2, 27.5 parts of acrylic polyol (Acrydic A-801),
A coating material was obtained and tested in the same manner as in Example 5 using 32.2 parts of butyl acetate and 20.0 parts of titanium oxide. Table 1 shows the results.

Example 7 20.8 parts of the curing agent (A-3) obtained in Example 3, 28.8 parts of acrylic polyol (Acrydic A-801),
A coating material was obtained and tested in the same manner as in Example 5 using 30.4 parts of toluene and 20.0 parts of titanium oxide. Table 1 shows the results
Shown in

Example 8 19.4 parts of the curing agent (A-4) obtained in Example 4, 30.9 parts of acrylic polyol (Acridic A-801),
A coating material was obtained and tested in the same manner as in Example 5 using 29.7 parts of toluene and 20.0 parts of titanium oxide. Table 1 shows the results
Shown in

Example 9 30.0 parts of the curing agent (A-1) obtained in Example 1, 7.5 parts of polyester polyol (Nipporan 1100, manufactured by Nippon Polyurethane Industry, hydroxyl value 215 mgKOH / g),
A coating material was obtained and tested in the same manner as in Example 5 using 42.5 parts of toluene and 20.0 parts of titanium oxide. Table 1 shows the results
Shown in

Comparative Example 3 The blocked isocyanate curing agent (B) obtained in Comparative Example 1
-1) 21.2 parts of acrylic polyol (Acrydic A-801, manufactured by Dainippon Ink and Chemicals, hydroxyl value 51)
mgKOH / g) 28.2 parts and toluene 30.6 parts,
20.0 parts of titanium oxide were mixed, and 100 parts of glass beads having a diameter of 2 mm were further mixed and dispersed for 60 minutes using a paint shaker. The paint was applied to a bonderite-treated steel sheet by an air sprayer so that the dry film thickness became 50 μm. Then, after standing at 20 ° C. and 60% RH for 30 minutes and baking at 150 ° C. for 20 minutes, adhesion, pencil hardness, impact resistance and gloss were tested. Table 1 shows the results.

Comparative Example 4 17.6 parts of the curing agent (B-2) obtained in Comparative Example 2, 33.6 parts of acrylic polyol (Acrydic A-801),
Using 28.8 parts of toluene and 20.0 parts of titanium oxide, a coating material was obtained and tested in the same manner as in Comparative Example 3. Table 1 shows the results.

Test Method Adhesion: A grid test was measured according to JIS K5400. Pencil strength: A pencil scratch test was measured according to JIS K5400. Impact resistance: DuPont impact test (1/2 inch, 1k
g) was measured according to JIS K5400. Gloss: Specular gloss (60 degrees) was measured according to JIS K5400.

[0029]

[Table 1]

Claims (2)

(57) [Claims] 1. An isocyanate group-terminated prepolymer (A) formed from hexamethylene diisocyanate and a polyol having a number average molecular weight of 300 to 5,000 (A) 50 to 80% by weight, and a cyclic trimerized oligomer of hexamethylene diisocyanate (B) 5 to 30% by weight % And blocking agent (C) 10
A blocked isocyanate curing agent composition comprising from about 30% by weight to about 30% by weight. 2. An isocyanate group-terminated prepolymer (A) formed from hexamethylene diisocyanate and a polyol having a number average molecular weight of 300 to 5,000 (A), 50 to 80% by weight, and a cyclic trimerized oligomer of hexamethylene diisocyanate (B), 5 to 30% by weight. % And blocking agent (C) 10
A coating composition comprising a blocked isocyanate curing agent comprising 30% by weight and an active hydrogen-containing resin,
The blocking agent in the blocked isocyanate curing agent is released.
The coating composition according to claim 1, wherein the molar ratio of all the isocyanate groups to the active hydrogen in the active hydrogen-containing resin when released is in the range of 9: 1 to 1: 9.