JPH10306136A - Production of active methylene type blocked isocyanate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an active methylene type blocked isocyanate composition excellent in color tone and useful as e.g. a top-coating material. SOLUTION: An alicyclic polyisocyanate (e.g. isophorone diisocyanate) is mixed with 1-1.5 equivalents, per equivalent of the isocyanate groups of the aliphatic polyisocyanate, of an acetoacetic acid ester compound, 0.01-5 wt.%, based on the alicyclic polyisocyanate, basic compound (e.g. sodium methylate) is added to the mixture, and the resulting mixture is reacted at 20-150 deg.C. The reaction is stopped by using 1-5 equivalents, per equivalent of the basic compound, of an acid compound (e.g. dibutyl phosphate).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an active methylene-based blocked polyisocyanate composition having an excellent color tone, which is suitable for applications such as topcoat paints where appearance is important.

[0002]

2. Description of the Related Art As a low-temperature baking type blocked polyisocyanate, a block polyisocyanate using an active methylene compound such as acetoacetate has been studied. For example, JP-A-52-116420 describes a blocked isocyanate obtained by blocking a burette-type polyisocyanate derived from hexamethylene diisocyanate with an acetoacetate ester. DE 3001060 describes a blocked isocyanate obtained by blocking an alicyclic polyisocyanate with an active methylene compound such as acetoacetate or malonate.

[0003] However, although these curing agent compositions containing active methylene polyisocyanates are excellent in low-temperature curability, they have a yellowish color tone, and are mainly used for applications such as top-coating paints, which emphasize appearance. The improvement was eagerly desired.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing an active methylene block polyisocyanate composition having excellent color tone.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor added an acidic compound when producing an acetoacetic ester block of an alicyclic polyisocyanate. As a result, they have found that the above problems can be solved, and have reached the present invention. That is, the present invention provides a method of mixing an alicyclic polyisocyanate and an acetoacetate-based compound in an amount of 1 to 1.5 equivalents based on the isocyanate group in the alicyclic polyisocyanate. After adding 0.01 to 5% by weight of a basic compound with respect to the isocyanate and reacting at 20 ° C to 150 ° C, 1 equivalent to 5% by weight of the basic compound is added.
The present invention relates to a method for producing an active methylene-based blocked isocyanate composition, wherein the reaction is stopped by using an acidic compound having an equivalent amount or less.

Hereinafter, the present invention will be described in more detail. The alicyclic polyisocyanate used in the present invention is derived from an alicyclic diisocyanate. As the alicyclic diisocyanate, isophorone diisocyanate (hereinafter, referred to as
IPDI), 1,3-bis (isocyanatomethyl) -cyclohexane, 4,4-dicyclohexylmethane diisocyanate, and the like. Examples of the polyisocyanate derived from these diisocyanates include isocyanurate-type polyisocyanate, burette-type polyisocyanate, and urethane-type polyisocyanate. These polyisocyanates can be used in combination with aliphatic polyisocyanates.

The acetoacetate compound used in the present invention includes, for example, methyl acetoacetate, ethyl acetoacetate, isopropyl acetoacetate, n-propyl acetoacetate, t-butyl acetoacetate, n-butyl acetoacetate, There are benzyl acetate, phenyl acetoacetate and the like, which may be used alone or in combination. In the present invention, the acetoacetic ester compound is used in an amount of 1 equivalent to 1.5 equivalents to isocyanate groups in the alicyclic polyisocyanate. If it is less than 1 equivalent, the isocyanate group in the alicyclic polyisocyanate remains, and when a one-pack coating is used, the viscosity increases and the storage stability is impaired. Further, even when used in an amount of more than 1.5 equivalents, the color tone deteriorates, and furthermore, yellowing is caused during baking and curing.

The basic compound used in the present invention is a reaction catalyst between an alicyclic polyisocyanate and an acetoacetate compound. Specifically, for example, metal alcoholates such as sodium methylate, sodium ethylate, sodium phenolate, and potassium methylate; tetramethylammonium, tetraethylammonium, tetraalkylammonium hydroxides such as tetrabutylammonium, and acetates thereof , Octylate, myristate, organic weak acid salts such as benzoate, acetic acid, caproic acid, octylic acid, alkali metal salts of alkyl carboxylic acids such as myristic acid, and tin, zinc, lead of the above alkyl carboxylic acids And the like, a metal salt containing an aminoacyl group such as hexamethylenedisilane, and a hydroxide of an alkali metal such as lithium, sodium and potassium.

The amount of the basic compound added is in the range of 0.01 to 5% by weight, preferably 0.05 to 3% by weight, based on the alicyclic polyisocyanate. 0.0
If the amount is less than 1% by weight, the reaction rate becomes low, which is disadvantageous. If it exceeds 5% by weight, the color tone of the active methylene-based blocked isocyanate composition obtained in the present invention is adversely affected.

The reaction between the alicyclic polyisocyanate and the acetoacetic ester compound can be carried out at a temperature of from 20 ° C. to 150 ° C. Preferably 40 ° C. or higher and 100
It is below ° C. If the temperature is higher than 150 ° C., a side reaction may occur, while if the temperature is lower than 20 ° C., the reaction rate is disadvantageously reduced. Examples of the acidic compound used in the present invention include inorganic acids such as hydrochloric acid, phosphorous acid, and phosphoric acid, methanesulfonic acid, p-toluenesulfonic acid, methyl p-toluenesulfonic acid, and ethyl p-toluenesulfonic acid. Sulfonic acid or a derivative thereof, ethyl phosphate, diethyl phosphate, isopropyl phosphate, diisopropyl phosphate, butyl phosphate, dibutyl phosphate, 2-ethylhexyl phosphate, di-2-ethylhexyl phosphate, isodecyl phosphate, diisodecyl phosphate, Examples thereof include acid esters of phosphoric acid or phosphorous acid such as butyl pyrophosphate and dibutyl phosphite. These may be used alone or in combination.
The amount of the acidic compound to be added is 1 equivalent or more and 5 equivalents or less with respect to the basic compound. Preferably 1.5 equivalents to 3
Is equivalent. If the amount is less than 1 equivalent, the reaction solution becomes turbid, and the effect of improving color tone is not sufficiently exhibited. If the amount exceeds 5 equivalents, the reaction solution becomes acidic, which undesirably has an effect of corroding the substrate and the like.

In the present invention, an appropriate solvent can be used as necessary for the reaction between the alicyclic polyisocyanate and the acetoacetic ester compound. As the solvent, for example, benzene, toluene, xylene, cyclohexane, mineral spirits, hydrocarbons such as naphtha, acetone, methyl ethyl ketone, ketones such as methyl isobutyl ketone, ethyl acetate, n-butyl acetate,
It can be appropriately selected from the group of esters such as cellosolve acetate and the like according to the purpose and use, and used.

When the color tone of the active methylene block isocyanate composition of the present invention is represented by the difference between the UV absorbance at a wavelength of 430 nm and the UV absorbance at a wavelength of 550 nm, if the value exceeds 0.1, the composition becomes yellow. It is not always satisfactory for applications that take on the appearance, such as topcoat paints. Therefore, this value is preferably 0.1 or less,
More preferably, it is 0.05 or less.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples. “Parts” in Examples and Comparative Examples are based on weight. The measuring method is as follows. (Color tone of active methylene-based blocked isocyanate composition)
cm was placed in a quartz cell, and the absorbance was measured using a spectroscope UV-160 manufactured by Shimadzu Corporation. The color tone of the composition was indicated by the difference between the absorbance at 430 nm and the absorbance at 550 nm. When this value exceeds 0.1, the color tone becomes yellowish.

[0014]

Example 1 IPDI isocyanurate type polyisocyanate (manufactured by Huls, T-1890L: isocyanate group content 12.0 wt%, solid content 70 wt%)) 1
Then, 00 parts, 39.0 parts of ethyl acetoacetate, and Solvesso # 10025.8 parts as a solvent were charged, and 0.18 part of a 28% methanol solution of sodium methylate was added at room temperature, followed by reaction at 80 ° C.

After confirming the disappearance of the isocyanate group by an infrared spectrophotometer (FT-IR),
The reaction was stopped by adding 7 parts. At this time, the color tone is 0.1.
03, which was good.

[0016]

Example 2 IPDI isocyanurate type polyisocyanate (T-1890L, manufactured by Huls: isocyanate group content: 12.0 wt%, solid content: 70 wt%) 1
00 parts, 39.0 parts of ethyl acetoacetate and 39.6 parts of xylene as a solvent were charged, and sodium methylate 28%
0.13 parts of a methanol solution was added at room temperature, and reacted at 80 ° C.

After confirming the disappearance of the isocyanate group by an infrared spectrophotometer (FT-IR), 0.45 parts of di-2-ethylhexyl phosphate was added to stop the reaction. At this time,
The color tone was as good as 0.04.

[0018]

Example 3 IPDI isocyanurate type polyisocyanate (manufactured by Huls, T-1890L: isocyanate group content: 12.0 wt%, solid content: 70 wt%) 1
00 parts, 39.0 parts of ethyl acetoacetate, and 39.6 parts of xylene as a solvent were charged, and zinc acetylacetonate was added to 0.1 part.
04 parts were added at room temperature and reacted at 97 ° C.

After confirming the disappearance of the isocyanate group by infrared spectrophotometer (FT-IR),
9 parts were added to stop the reaction. At this time, the color tone is 0.1.
04, which was good.

[0020]

Comparative Example 1 IPDI isocyanurate type polyisocyanate (manufactured by Huls, T-1890L: isocyanate group content: 12.0 wt%, solid content: 70 wt%) 1
00 parts, 39.0 parts of ethyl acetoacetate and 39.6 parts of xylene as a solvent were charged, and sodium methylate 28%
0.13 parts of a methanol solution was added at room temperature, and reacted at 80 ° C.

After confirming the disappearance of the isocyanate group by an infrared spectrophotometer (FT-IR), the temperature was lowered to stop the reaction. At this time, the color tone was 0.11.5, which was yellowish.

[0022]

According to the present invention, an active methylene block polyisocyanate excellent in color tone can be produced by adding an acidic compound when producing an acetoacetic ester block of an alicyclic polyisocyanate. It can be suitably used for applications such as topcoat paints where the appearance is important.

Claims (1)

[Claims] 1. An alicyclic polyisocyanate and one to an isocyanate group in the alicyclic polyisocyanate.
An acetoacetate compound of not less than 1.5 equivalents and not more than 1.5 equivalents is mixed with respect to the alicyclic polyisocyanate.
Add 1 to 5% by weight of a basic compound, and add
A method for producing an active methylene-based blocked isocyanate composition, comprising reacting at 50 ° C. or lower, and terminating the reaction with 1 to 5 equivalents of an acidic compound based on a basic compound.