JPH10306256A - Polyurethane coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a two-pack polyurethane coating composition having excellent adhesivity to metal and high heat-resistance. SOLUTION: This coating composition is composed of (A) a polyol having a hydroxyl value of 1-300 mgKOH/g and dilutable with an organic solvent as a main agent and (B) a polyisocyanate composition containing 1-300 mmol of phosphorus atom per 100 g of the polyisocyanate composition and consisting of a polyisocyanate derived from an aliphatic or alicyclic diisocyanate and phosphinic acid, phosphonic acid or a phosphonic acid ester bonded to the polyisocyanate. The equivalent ratio of the isocyanate group of the component B to the hydroxyl group of the component A is 0.2-5.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a room temperature crosslinked two-pack polyurethane coating composition comprising a base polyol and a phosphorus-containing polyisocyanate composition, which has excellent adhesion to metals and excellent heat resistance. Therefore, the present invention relates to a cold-crosslinkable two-pack polyurethane coating composition useful mainly as a coating material for automobiles, a coating material for building materials, a coating material for PCM, a household coating material, other coating agents, adhesives, sealing agents, building materials, and plastic materials.

[0002]

2. Description of the Related Art A two-pack polyurethane coating composition comprising a polyisocyanate obtained from an aliphatic or alicyclic diisocyanate and a base polyol is a non-yellowing type and forms a coating film having excellent weather resistance and chemical resistance. be able to. The polyurethane coating composition has excellent adhesion to a substrate, but has slightly poor adhesion to metals, particularly aluminum. Therefore, when coating a metal surface, it is necessary to treat the metal surface with a primer in advance, but this increases the number of steps required for coating by one, and cannot provide a clear coating film. There is.

As another method for increasing the adhesion to metals, an additive such as a phosphate ester is often added to a coating composition. In this method, a phosphate ester or the like which does not participate in crosslinking is used. It may remain in the coating film, causing a decrease in weather resistance and chemical resistance, and may cause the coating film to become brittle. Further, the two-pack polyurethane coating composition generally has heat resistance of about 200 to 250 ° C. In order to improve heat resistance, a method of adding an additive such as a phosphate ester to the coating composition is used. In this method, as described above, a decrease in weather resistance and a decrease in chemical resistance, and May cause vulnerabilities.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a two-part polyurethane coating composition having excellent metal adhesion and excellent heat resistance.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted various studies to solve the above-mentioned problems. As a result, a room temperature crosslinked two-part polyurethane coating composition comprising a base polyol and a polyisocyanate composition containing phosphorus has been developed. The inventors have found that the above-mentioned problems can be solved, and have accomplished the present invention.

That is, the present invention comprises the following components A) and B), wherein the equivalent ratio of the isocyanate groups of the component B) to the hydroxyl groups of the component A) is in the range of 0.2 to 5.0. And a polyurethane coating composition. A) A base polyol having a hydroxyl value of 1 to 300 mgKOH / g. B) A polyisocyanate composition having a phosphinic acid, a phosphonic acid, or a phosphonic acid ester bonded to a polyisocyanate obtained from an aliphatic diisocyanate and / or an alicyclic diisocyanate, wherein one phosphorus atom is contained in 100 g of the polyisocyanate composition. A polyisocyanate composition containing from 300 to 300 mmol.

Hereinafter, the present invention will be described in detail. The base polyol in the present invention is a polyol having two or more hydroxyl groups in one molecule. The base polyol used in the present invention has a hydroxyl value of 1 to 300 mgKOH / g. When the hydroxyl value is less than 1 mgKOH / g, the coating density becomes low and the coating film becomes brittle, which is not preferable. If the hydroxyl value exceeds 300 mgKOH / g, the crosslink density becomes too high, and the smoothness of the surface of the coating film may be impaired.

The main polyols used in the present invention include aliphatic hydrocarbon polyols, fluorine polyols, polyether polyols, polyester polyols, polycarbonate polyols, epoxy resins, acrylic polyols, and alkyd polyols. At least one of the classes or mixtures thereof are suitable.

The above-mentioned base polyol can also be used as a mixture with an organic solvent. The base polyol mixed with an organic solvent has a characteristic of being easy to handle because the viscosity is low. In this case, it is necessary that the organic solvent does not have a functional group that reacts with a hydroxyl group and an isocyanate group. The organic solvent is preferably compatible with the polyol of the present invention.

Examples of such an organic solvent include ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, methoxypropyl acetate, 3-methoxybutyl acetate, 2-ethylbutyl acetate, and 2-ethylhexyl. acetate,
Ester compounds such as cyclohexyl acetate, methyl propionate, butyl propionate, butyl butyrate, dioctyl adipate, and diisopropyl glutarate; ether compounds such as diisopropyl ether, dibutyl ether, dioxane, and diethoxyethane; 2-pentanone;
Ketone compounds such as pentanone, 2-hexanone, methyl isobutyl ketone 2-heptanone, 4-heptanone, diisobutyl ketone, isophorone, cyclohexanone, and methylcyclohexanone, and aromatic compounds such as benzene, toluene, xylene, ethylbenzene, butylbenzene, and p-cymene And polyethylene glycol dialkyl ether-based compounds such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether and triethylene glycol dimethyl ether, and polyethylene glycol dicarboxylate-based compounds such as diethylene glycol diacetate.

The aliphatic and / or alicyclic diisocyanates used in the present invention include, for example, tetramethylene diisocyanate, pentamethylene diisocyanate,
Hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, hydrogenated xylene diisocyanate, 1,4-diisocyanate cyclohexane, norbornene diisocyanate, and the like. Among them, hexamethylene diisocyanate, isophorone diisocyanate and hydrogenated xylene diisocyanate are easily available industrially and are good.

The polyisocyanate obtained from the above diisocyanate in the present invention means at least one of the above diisocyanates and a biuret structure in a molecule derived from at least one of the above diisocyanates.
It has a structure such as an isocyanurate structure, urethane structure, uretdione structure, and allophanate structure.

A method for producing a polyisocyanate having a biuret structure, an isocyanurate structure, a urethane structure, a uretdione structure, and an allophanate structure from diisocyanate is described in, for example, Japanese Patent Publication No. Sho 64.
JP-A-10023, JP-A-58-38713,
JP-B-63-89574, JP-A-6-95041
JP-A-4-306218, U.S. Pat.
Reference can be made to 124,605. Those having a biuret structure have excellent adhesiveness, those having an isocyanurate structure have excellent weather resistance, and those having a urethane structure using an alcohol compound having a long side chain have excellent elasticity and extensibility. Those having a uretdione structure or an allophanate structure have a characteristic of low viscosity.

The phosphinic acid, phosphonic acid and phosphonate ester bonded to the polyisocyanate in the present invention have the following structures.

[0015]

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When x is less than 1, phosphoric acid or a phosphoric ester which does not bind to the polyisocyanate is present.
If y exceeds 2, phosphoric acid or phosphoric acid ester which does not bind to polyisocyanate exists, and if z exceeds 2, phosphoric acid or phosphoric acid ester which does not bind to polyisocyanate exists. Examples of a method for producing a polyisocyanate composition having phosphinic acid, phosphonic acid, and a phosphonate ester bonded to the polyisocyanate include, for example, polyisocyanate obtained from diisocyanate, phosphoric acid, and phosphoric acid ester of 40%.
A method of reacting at a temperature of 160 ° C. for several minutes to several days is exemplified. This reaction can be performed before, during, or after the reaction for obtaining the above biuret structure, isocyanurate structure, urethane structure, allophanate structure, or the like.

In the present invention, the number of phosphorus atoms per 100 g of the polyisocyanate composition is 1 to 300 mmol. If the amount is less than 1 mmol, sufficient adhesion cannot be provided, which is not preferable. If it exceeds 300 mmol, the phosphorus content in the polyisocyanate composition becomes too large, which may cause the coating film to become brittle.

In the present invention, the adhesiveness is determined according to JIS K
It is measured by a 5400 grid tape method. Sufficient adhesion in the present invention means that the evaluation score is 8 points or more. For example, polyisocyanate obtained from hexamethylene diisocyanate and Acridic A-801
(Acrylic polyol, Dainippon Ink Co., Ltd.) two-component polyurethane coating composition
When the coating film applied to 1100P and dried at 20 ° C. and 65% RH for one week was measured by a grid tape method, the evaluation score was 2
Below the point.

Further, 100 g of the polyisocyanate composition
When the number of phosphorus atoms per unit exceeds 10 mmol, the heat resistance of a coating film or the like obtained from the coating composition of the present invention is improved. In the present invention, heat resistance,
Evaluation is made based on the height of the thermal decomposition point measured using a differential thermogravimetric simultaneous measurement device. The thermal decomposition point is a point at which measurement is started at room temperature and the weight is reduced by 5% from the initial weight when the temperature is increased at 3 ° C./min.

The improvement in heat resistance referred to in the present invention means that the thermal decomposition point is improved by 10 ° C. or more. For example, the polyisocyanate obtained from hexamethylene diisocyanate has a thermal decomposition point of about 250 ° C. when it mainly has an isocyanurate structure, and 24 ° C. when it mainly has a urethane structure.
About 0 ° C, 200 ° C when mainly having biuret structure
The temperature is about 150 ° C. when the uretdione structure is mainly contained, and about 180 ° C. when the allophanate group is mainly contained.

In the present invention, the polyisocyanate composition can be used by mixing with an organic solvent. The polyisocyanate composition mixed with an organic solvent has a feature that it is easy to handle because the viscosity is low. In this case, it is necessary that the organic solvent does not have a functional group that reacts with a hydroxyl group and an isocyanate group. The organic solvent is preferably compatible with the polyisocyanate composition. Examples of such an organic solvent include the organic solvents exemplified as the organic solvent to be mixed with the above-mentioned base polyol.

In the present invention, the equivalent ratio of isocyanate group / hydroxyl group of the main component polyol (A) and the polyisocyanate composition (B) is 0.2 to 5.0.
If it is less than 0.2, the number of cross-linking points in the urethane coating composition is reduced, which causes a decrease in the curing speed or a brittleness of a coating such as a coating film. If it exceeds 5.0, the coating becomes hard and brittle, which is not preferable.

In the polyurethane coating composition according to the present invention, depending on the purpose and application, such techniques as catalysts, pigments, leveling agents, antioxidants, ultraviolet absorbers, light stabilizers, plasticizers, surfactants, etc. Various additives used in the field can be mixed and used. Since the polyisocyanate composition used in the present invention contains a phosphorus atom, the coating film obtained from the urethane coating composition of the present invention has excellent adhesion to metals and is also excellent in heat resistance. It has the feature of. Therefore,
Such urethane coating compositions are mainly cold-crosslinkable two-pack polyurethanes useful as automotive coatings, building material coatings, PCM coatings, household coatings, other coatings, adhesives, sealing agents, building materials, and plastic materials. It can be used as a coating composition agent.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to examples and comparative examples. In addition, various characteristics were measured by the following methods. The isocyanate group content was determined by back titration with hydrochloric acid after neutralizing the isocyanate group with an excess of amine. The viscosity is measured using a digital viscometer (Tokyo Keiki DVM-
(Type B) at 25 ° C. and 60 rpm. The heat resistance was determined using a thermogravimetric differential thermometer (TG / DTA200, Seiko Instruments Inc.) at the point where the weight was reduced by 5% from the initial weight as the thermal decomposition point. The temperature was raised from room temperature at 3 ° C./min. Adhesion was measured by applying a polyisocyanate coating composition at a thickness of 50 μm and curing it at 20 ° C. and 65% RH for one week, and then applying the JIS K 5400 cross-cut tape method (interval 1 mm, 100 squares). It was measured.

[0025]

Example 1 Hexamethylene diisocyanate isocyanurate type polyisocyanate (Duranate T
1000 g of PA-100 (manufactured by Asahi Kasei Corporation) and 22 g of dibutyl phosphoric acid were mixed and reacted at 90 ° C. for 4 hours. The obtained polyisocyanate composition was a pale yellow liquid, and contained 10.2 mmol of phosphorus atoms, 22.5% of isocyanate group content and 2200 mPa.s per 100 g of the polyisocyanate composition. s (25 ° C)
The thermal decomposition point was 280 ° C.

Acrylic polyol (Acridic A-
801 from Dai Nippon Ink Co., Ltd.) and the above polyisocyanate composition at an NCO / OH equivalent ratio of 1.0 to obtain a polyurethane coating composition. The adhesion of the obtained coating composition to the aluminum plate P1100 was measured and found to be 10 points.

[0027]

Example 2 Hexamethylene diisocyanate isocyanurate type polyisocyanate (Duranate T
1000 g of PA-100 (manufactured by Asahi Kasei Corporation) and 440 g of dibutyl phosphoric acid were mixed and reacted at 90 ° C. for 4 hours. The obtained polyisocyanate composition was a pale yellow liquid, and contained 145 mmol of phosphorus atoms, an isocyanate group content of 10.1%, and a viscosity of 6000 mPa.s per 100 g of the polyisocyanate composition. s (25 ° C)
The thermal decomposition point was 320 ° C.

Acrylic polyol (Acridic A-
801 from Dai Nippon Ink Co., Ltd.) and the above polyisocyanate composition at an NCO / OH equivalent ratio = 1.0.
A polyurethane coating composition was obtained. The adhesion of the obtained coating composition to the aluminum plate P1100 was measured and found to be 10 points.

[0029]

Since the polyisocyanate composition used in the present invention contains a phosphorus atom, the coating film obtained from the urethane coating composition of the present invention has excellent adhesion to metals, and furthermore has high heat resistance. It has the characteristic that it is also excellent. Therefore, such a urethane coating composition is mainly used as a cold-crosslinkable type paint useful as an automotive paint, a building material paint, a PCM paint, a household paint, other coating agents, adhesives, sealing agents, building materials, and plastic raw materials. It can be used as a liquid polyurethane coating composition.

Claims (1)

[Claims] 1. A polyurethane coating comprising the following components A) and B), wherein the equivalent ratio of the isocyanate groups of component B) to the hydroxyl groups of component A) is in the range from 0.2 to 5.0. Composition. A) A base polyol having a hydroxyl value of 1 to 300 mgKOH / g. B) A polyisocyanate composition having a phosphinic acid, a phosphonic acid, or a phosphonic acid ester bonded to a polyisocyanate obtained from an aliphatic diisocyanate and / or an alicyclic diisocyanate, wherein one phosphorus atom is contained in 100 g of the polyisocyanate composition. A polyisocyanate composition containing from 300 to 300 mmol.