JP3293034B2 - Polyisocyanate curing agent, resin composition for polyurethane coating 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 polyisocyanate curing agent and a resin composition for polyurethane coatings, and more particularly to a resin composition for polyurethane coatings useful for any object to be coated such as metals, plastics and woods. is there.

[0002]

2. Description of the Related Art It is well known that polyurethanes derived from hexamethylene diisocyanate (hereinafter referred to as HDI) have excellent weather resistance due to their properties. Therefore, a polyol adduct of HDI or a modified product by burette bonding is used as a polyisocyanate curing agent for coating. However, both the polyol adduct and the modified product due to the burette bond are liable to be decomposed and deteriorated by heating, and there is a limit to the weather resistance. Also, the HDI-based compound reacts slowly with the active hydrogen compound, and has to rely on baking and drying to increase the crosslink density and obtain excellent durability. On the other hand, aromatic diisocyanates are superior to aliphatic diisocyanates such as HDI in degradation by heating, but are yellowed by light, so that aromatic diisocyanates are not suitable as weather-resistant paints. However, the reactivity is faster than that of the HDI system, and there is no limitation under baking conditions as seen in the HDI system. Therefore, an isocyanate having weather resistance, heat resistance, and curability has been demanded.

[0003]

SUMMARY OF THE INVENTION The present inventors have conducted intensive studies and studies to improve the conventional problems, and as a result,
The present invention has been found to be able to be improved by using a modified product (A) which has been converted to an isocyanurate and an NCO group-terminated prepolymer (B) after partially converting the NCO group of I into a polyol adduct. .

[0004]

That is, the present invention relates to an isocyanurate-modified HDI obtained by converting a part of the NCO group of HDI into a polyol adduct and then isocyanurating it.
A polyisocyanate curing agent comprising a CO group-terminated prepolymer, a polyol having a molecular weight of 500 or more, and an HD obtained by forming a part of the NCO group of HDI into a polyol adduct as a curing agent and then isocyanurating it.
The present invention relates to a resin composition for a polyurethane coating, comprising a modified isocyanurate of I and an NCO group-terminated prepolymer.

[0005] The polyisocyanate curing agent of the present invention comprises H
A modified product (A) (hereinafter, referred to as a modified product of HDI (A)) in which a part of the NCO group of DI is converted into a polyol adduct and then isocyanurated, and an NCO group-terminated prepolymer (B). is there. Modified form of HDI (A)
Is a product obtained by converting a part (15% by weight or less) of all NCO groups of HDI into a polyol adduct and then isocyanurating the polyol.

As a polyol for obtaining a polyol adduct, a bifunctional or trifunctional polyol having a molecular weight of 3000 or less is used. Examples of the bifunctional polyol include ethylene glycol, diethylene glycol, 1,3-butanediol (1,3-BD), 1,4-butanediol, propylene glycol, dipropylene glycol,
Examples thereof include diols such as neopentyl glycol and 1,6-hexanediol (1,6-HD), divalent polyester polyols, and polyether polyols.

[0007] Examples of the trifunctional polyol include triols such as glycerin, trimethylolethane, and trimethylolpropane, and trivalent polyether polyols. Furthermore, a bifunctional or more functional polyester polyol is mentioned. These polyols can be used alone or as a mixture of two or more.

The urethanization ratio is preferably 15% by weight or less based on all isocyanates. If the content is 15% by weight or more, the characteristics of the isocyanurated bond formed thereafter cannot be sufficiently exhibited.

The thus obtained HDI polyol adduct is used alone or in combination with a potassium or sodium salt of an organic acid represented by the general formula Cn H _{2n + 1} COOH, and if necessary, a cocatalyst may be used. The reaction can be carried out at 100 ° C. or lower. Catalysts that can be used include propionic acid, butyric acid, valeric acid, caproic acid, heptanoic acid,
Examples include caprylic acid, pelargonic acid, capric acid, undecylic acid and the potassium or sodium salts of these branched fatty acids.

When a phenolic hydroxy compound, an alcoholic hydroxy compound, or a tertiary amine is used as a co-catalyst simultaneously with these catalysts, the reaction proceeds more easily. Such an HDI isocyanuration reaction can be performed by the method described in JP-A-57-47321. NC of modified form of HDI (A)
The O content is 16.5-23.5% by weight.

The polyisocyanate for obtaining the NCO-terminated prepolymer of the present invention includes aromatic, aliphatic and
An alicyclic group or the like is used. Examples of the aromatic polyisocyanate include 2,4- or 2,6-toluylene diisocyanate, naphthylene-1,5-diisocyanate,
4,4 ', 4 "-triisocyanatotriphenylmethane, 2,4,6-triisocyanatotoluene, or polyphenylpolymethylene polyisocyanate (Polymeric MDI) as prepared by aniline-formaldehyde condensation and subsequent phosgenation ), Diphenylmethane diisocyanate (MDI) and the like. Examples of the aliphatic or alicyclic polyisocyanate include tetramethylene diisocyanate, decamethylene diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3- and -1, 4-diisocyanate,
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI), perhydro-2,4- and / or -2,6-diisocyanatotoluene or perhydro 2,4'- and / or -4,4'-
And diisocyanatodiphenylmethane.

Preferred NCO-terminated prepolymers are prepolymers using aromatic polyisocyanates, particularly preferably 2,2'-MDI, 2,4'-M
DI, 4,4'-MDI, polymeric MDI or the like, or a mixture thereof, or a compound obtained by modifying a part of these isocyanates with biuret, allophanate, carbodiimide, oxazolidone, amide, imide, etc., and an active hydrogen group-containing compound. It is obtained by reacting with an excess of isocyanate groups. The NCO content of such a prepolymer is preferably from 16.0 to 30.0% by weight.

Compounds having an active hydrogen group for obtaining an NCO group-terminated prepolymer include low molecular polyols,
Polyether-based polyols, polyester-based polyols, castor oil-based polyols and the like can be mentioned. These can be used alone or as a mixture of two or more. As the low-molecular polyol, divalent ones such as ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, hydrogenated bisphenol A, etc. Trivalent to octavalent), for example, glycerin, trimethylolpropane, hexanetriol, pentaerythritol, sorbitol,
Shoe close and the like. The low molecular weight polyol has a molecular weight of 62 to 500, and the other polyols have a molecular weight of 300 to 50.
00 is preferred.

The polyisocyanate curing agent of the present invention comprises H
Modified DI (A) and NCO-terminated prepolymer (B)
And 10 to 90% by weight: 90 to 10% by weight.

A molecular weight of 500 which can be used in the present invention
As the above polyol, polyester polyol,
Polyether polyols, polycarbonate polyols, acrylic polyols and the like, and polyester polyols having a molecular weight of 500 to 9000, for example, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, trimethylene glycol, 1,3 -Or one or more of monomolecular compounds having two or more hydroxyl groups such as 1,4-butanediol, 1,6-hexanediol, decamethylene glycol, glycerin, trimethylolpropane, pentaerythritol, and sorbitol; And adipic acid, succinic acid, malonic acid, maleic acid, tartaric acid, sebacic acid, phthalic acid, terephthalic acid, isophthalic acid,
Monomolecular compounds having two carboxyl groups such as trimellitic acid, or those obtained by a condensation reaction with one or more kinds of castor oil fatty acids or the like, and ring-opening polymerization of ε-caprolactone, methyl-δ-valerolactone, etc. Lactone ester and the like.

The polyether polyol has a molecular weight
Of 500 to 5000, for example, ethylene glycol, diethylene glycol, propylene glycol, glycols such as dipropylene glycol, glycerin, trimethylolethane, trimethylolpropane, polyols such as pentaerythritol ethylene oxide, alkylene oxides such as propylene oxide And hydroxyl group-containing polyether polyols obtained by addition polymerization.

The polycarbonate polyols having a molecular weight of 500 to 3,000, for example, a dealcoholization reaction of a glycol with a dialkyl carbonate such as dimethyl or diethyl, a dephenol condensation reaction of a glycol with a diphenyl carbonate, or a glycol with ethylene. Examples include those obtained by the ethylene glycol condensation reaction of carbonate. Examples of the glycols include 1,6-hexanediol, diethylene glycol, propylene glycol, 1,4-butanediol, 3-methyl-1,5-pentanediol,
Examples thereof include aliphatic diols such as neopentyl glycol, and alicyclic diols such as 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol.

The acrylic polyol has a molecular weight of 500
For example, hydroxyalkyl acrylate is used as a hydroxyl group source, and alkyl acrylate and a compound copolymerizable therewith are obtained by combination copolymerization. Examples of the hydroxyalkyl alkylate include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and hydroxybutyl methacrylate. Those having a number of 2 to 16, for example, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate and the like. Examples of the copolymerizable compound include styrene, dibutyl fumarate, dibutyl malate, and allyl alcohol. If the molecular weight of the polyol is less than 500, the coating film is extremely hard and brittle, and is not suitable as a coating. If the molecular weight exceeds 100,000, the viscosity increases and the workability deteriorates, and the coating film becomes too soft and unsuitable as a paint.

The resin composition for coatings of the present invention comprises the above-mentioned HD
The modified isocyanurate and the NCO group-terminated prepolymer and the polyol are obtained by blending with an NCO / OH ratio of 0.8 to 1.2, and a solvent commonly used in this field can be used. It is. That is, toluene, xylene, ethyl acetate, butyl acetate, cello acetate, methyl ethyl ketone and the like can be mentioned. To paint,
If necessary, other components such as pigments, plasticizers, leveling agents, surfactants and other fillers and additives can be used in combination. To use the oil after denaturation, use a drying oil such as castor oil. In addition, as usual, various catalysts such as amines and organic metal salts, extenders, flow improvers, drying regulators, matting agents, etc. Paint aids can be used.

Since the composition according to the present invention is excellent in heat resistance and weather resistance, it can sufficiently exhibit the performance as a weather resistant paint without adding an antioxidant, an ultraviolet absorber or the like. The coating composition formulated as described above,
For example, any of the commonly used coating methods such as spraying, brushing, dipping, flow coating, roll, knife coating, etc. can be applied, and curing conditions are different depending on the base material,
What is necessary is just to harden by normal temperature or heating. Curing can be promoted by adding a catalyst if necessary. Since the paint obtained by the present invention has excellent heat resistance and weather resistance, it can be widely applied to all kinds of substrates such as various metals, plastics, leathers, glasses, and woods. In addition, the polyisocyanate curing agent of the present invention promotes curing by applying as a curing agent for not only paints, but also resins for adhesives, resins for synthetic leather, resins for fibers, and resins for magnetic recording media, Further, all physical properties such as heat resistance, abrasion resistance and chemical resistance of the obtained cured product can be improved and improved.

[0021]

The present invention will be described more specifically below with reference to examples and comparative examples. However, the present invention is not limited to these. “Parts” and “%” in Examples and Comparative Examples are “parts by weight” and “% by weight” unless otherwise specified.

Preparation of Modified Form of HDI (A) Preparation of A-1 300 parts of HDI in a 500 ml separable flask equipped with a thermometer, a stirrer and a nitrogen sealed tube, and 1,3-polyol as a polyol.
Put 2.4 parts of BD, replace the air in the flask with nitrogen,
The mixture was heated to a reaction temperature of 80 ° C. with stirring and reacted at the same temperature for 2 hours. The NCO content was measured to be 48.8%. Next, 0.06 part of potassium caprate as a catalyst and 0.3 part of phenol as a cocatalyst were added, and an isocyanurate-forming reaction was performed at 60 ° C. for 4.5 hours. 0.042 parts of phosphoric acid was added to this reaction solution as a terminator, and after stirring at the reaction temperature for 1 hour, free HDI was removed by a molecular distillation apparatus. The obtained liquid is a pale yellow transparent liquid having an NCO content of 21.0% and a viscosity of 2200 mPa · s / 25 ° C.
The free HDI content was 0.4%. (A) This modified product is
-1.

Production of A-2 300 parts of HDI, 1,3-B
The reaction was carried out in the same manner as in A-1 by using 10.2 parts of D, 0.06 part of potassium propionate as a catalyst, 0.3 part of phenol, and 0.072 part of phosphoric acid. After reacting the polyol with HDI, the NCO content was 45.3%. After distillation, the NCO content was 19.2%, the viscosity was 2800 mPa · s / 25 ° C., and the free HDI content was 0.3%.
This modified product is designated as A-2.

Production of A-3 300 parts of HDI, 1,6-H
DI 3.3 parts, sodium undecylate 0.03 parts, phosphoric acid
The reaction was carried out in the same manner as in A-1 using 0.198 parts. HDI
After the reaction with the polyol, the NCO content was 48.6%. After distillation, the NCO content was 20.5%, the viscosity was 3000 mPa · s / 25 ° C, and the free HDI content was 0.4%. This modified product is designated as A-3.

Using a device similar to A-3, 300 parts of HDI and 80 parts of trimethylolpropane were reacted at 80 ° C. for 5 hours to obtain a prepolymer having an NCO content of 19.4% and a viscosity of 80,000 mPa · s / 25 ° C. Was. This prepolymer is designated as A-4.

Production of NCO-terminated prepolymer (B) Production of B-1 Production of modified product Using the same equipment as in (A), 318 parts of MDI (Millionate MT, manufactured by Nippon Polyurethane Industry) and 15 parts of diethylene glycol Was reacted at 80 ° C. for 4 hours to obtain a prepolymer having an NCO content of 28.0% and a viscosity of 80 mPa · s. This prepolymer is designated as B-1.

Production of B-2 Carbodiimide-modified MDI using an apparatus similar to B-1
(Millionate MT, manufactured by Nippon Polyurethane Industry
L) 233 parts and PPG-2000 (Asahi Denka Kogyo polyether) 1
15 parts was reacted at 80 ° C. for 4 hours to obtain a prepolymer having an NCO content of 18.0% and a viscosity of 800 mPa · s / 25 ° C. This prepolymer is referred to as B-2.

Examples 1 to 8, Comparative Examples 1 to 4 Preparation of paint resin composition and coating film test Paints were prepared at the ratios shown in Table 1. The heat resistance, weather resistance and curability of the coating composition thus obtained were measured by the following test methods. Table 2 shows the results. Heat resistance ... Apply this coating composition on release paper,
Leave for 1 week in an environment of 65 ° C and 65% RH, and dry film thickness 100μ
Was obtained. And the film is JIS K 6301
A test piece was punched out using a No. 4 dumbbell in accordance with the above standard. The properties of the film, the tensile strength (T _B ), and the elongation (E _B ) retention (%) were measured at 50 ° C. and 150 ° C. for each elapsed time.

Weather resistance: A steel plate (JIS G3141 <SPCC-SB>) obtained by degreasing the above coating composition with trichloroethylene.
Specifications: PF-1077, manufactured by Nippon Test Panel Kogyo; Bonde steel plate) and left for 1 week in an environment of 20 ° C. and 65% RH to form a coating film having a dry film thickness of 40 to 50 μm. And
Using a sunshine weatherometer (manufactured by Suga Test Instruments), the gloss retention (%) after 2,000 hours according to JIS K 5400 under the conditions of black panel temperature = 63 ± 3 ° C., spraying time = 120 minutes and 18 minutes, The degree of discoloration (ΔE) was measured. Curability: A film prepared in the same manner as in the heat resistance test was cut into small pieces, placed in a Soxhlet extraction apparatus, and acetone was used as an extraction solvent, and extraction was performed with acetone at the boiling point (56 ° C) for 4 hours under reflux. Operation was performed. Then, the gel fraction value (%) was determined by the following equation.

[0030]

[Table 1]

[0031]

[Table 2]

Examples 9 to 16 and Comparative Examples 5 to 7 In the same manner as in Example 1, resin compositions for coatings were prepared and subjected to a coating film test. Table 3 shows the resin compositions for coatings. Table 4 shows the results of the coating film test.

[0033]

[Table 3]

[0034]

[Table 4]

Examples 17 to 21, Comparative Examples 8 and 9 Preparation of paint resin composition and coating film test Paints were prepared at the ratios shown in Table 5. Then, it was applied to a PVC flooring material using a bar coater so as to have a dry film thickness of 100 μm, forcibly dried at 80 ° C. for 20 minutes, and then cured at room temperature for 15 hours to conduct a coating film test. Table 5 shows the results. Adhesion test: According to JIS K 5400. Stain resistance: Magic ink was applied to the surface of the coating film, and after 5 minutes, ease of wiping with a cloth impregnated with butanol was observed.
○ ───Good △ ───Poor × ───Poor Abrasion resistance: According to Taber test method.

[0036]

[Table 5]

Notes of Table 5 1) Esterification of castor oil-based polyester polyol, acid value 2, hydroxyl value 74, molecular weight 2350, (castor oil 500 parts, diethylene glycol 132 parts, 1,4-butanediol 157 parts, adipic acid 438 parts) The coating was prepared by diluting with a solvent in the same manner as in Example 1 to reduce the resin content to 35%.

As a curing agent, after a part of the NCO group of HDI is converted into a polyol adduct, a component composed of a modified isocyanurated HDI and an NCO-terminated prepolymer is used to obtain heat resistance. , Weatherability, curability, etc., show good performance with good mutual balance. It also has excellent physical properties such as adhesion, stain resistance, and wear resistance.

Claims (1)

(57) [Claims] 1. A polyol having a molecular weight of 500 or more, an isocyanurate-modified isocyanurate-modified hexamethylene diisocyanate obtained by converting a part of the NCO group of hexamethylene diisocyanate into a polyol adduct as a curing agent, and an NCO group-terminated prepolymer And a resin composition for a polyurethane paint.