JPH02110123A - Preparation of polyisocyanate - Google Patents

Abstract

PURPOSE:To prepare a polyisocyanate having an isocyanurate structure with very low degree of discoloration by using a catalyst deactivating agent with a specified structure when cyclic trimerization of an aliph. or alicyclic diisocyanate is performed by using a catalyst. CONSTITUTION:When a polyisocyanate having an isocyanurate structure is prepd. by performing cyclic trimerization of an aliph. or alicyclic diisocyanate (e.g., hexamethylene diisocyanate or isophorone diisocyanate) with a catalyst (e.g., tetraalkylammonium hydroxide), a compd. having a structure of formula I or II in its molecule (e.g., urea, thiourea, phenyl carbamate, etc.) is used as a deactivating agent for said catalyst. The polyisocyanate having an isocyanurate structure obtd. by said procedure exhibits a very low degree of discoloration and is extremely useful as a curing agent for polyurethane resins for coatings, adhesives, coating materials, casting materials, elastomers, foaming materials, etc.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is directed to
This invention relates to a method for producing group polyisocyanates.

[Conventional technology]

Hexamethylene diisocyanate (hereinafter referred to as MDI)
, isophorone diisocyanate (hereinafter referred to as IPDI)
Polyisocyanates made from aliphatic and alicyclic diisocyanates, such as these, are widely used in the fields of paints, coatings, casting materials, foaming materials, etc. due to their non-yellowing property. .

Among them, polyisocyanates having an isocyanurate structure (for example, Japanese Patent Publication No. 45-27982, Japanese Unexamined Patent Publication No. 55
-38380, JP 57-150677, JP 57-47321, JP 61-111
No. 371) has attracted attention in recent years due to its excellent weather resistance.

[Problem that the invention seeks to solve]

However, this catalytic cyclic trimerization reaction of diisocyanate has the disadvantage that the resulting polyisocyanate tends to be colored, and it is currently unavoidable that the product will be slightly colored.

Therefore, the industry has been eagerly awaiting the emergence of a method for producing polyisocyanates having an isocyanurate structure and a low degree of coloration.

[Means for solving problems]

In view of these points, the present inventors have conducted extensive research, and as a result, have discovered that the above-mentioned drawbacks can be overcome by deactivating the catalyst for the cyclic trimerization reaction with a specific compound, and have completed the present invention. It has arrived.

That is, in the present invention, when producing a polyisocyanate having an isocyanate group by cyclic trimerization of an aliphatic or alicyclic diisocyanate with a catalyst, the deactivator of the catalyst has the following structure in the molecule. This is a method for producing a polyisocyanate characterized by having the following characteristics.

Alternatively, as the aliphatic and alicyclic diisocyanates used in the present invention, in addition to the above-mentioned MDI and IPDI, for example, 2.4
．． 4- or 2.2.4-trimethylhexamethylene diisocyanate, dodecamethylene diisocyanate, 2
, 6-dicyanatomethylcabroate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), Methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, m- or ■ )-xylylene diisocyanate (XDI), 1,3- or 1,4-tetramethylxylylene diisocyanate, and the like. It is also possible to use a mixture of two or more of these diisocyanate monomers. These diisocyanate monomers are arbitrarily selected depending on the purpose of use of the final product, but in particular HID,
IPDI and XDI are preferably used.

Catalysts used in the present invention include (1) tetraalkylammonium hydroxides and organic weak acid salts such as tetramethylammonium, tetraethylammonium, and tetrabutylammonium; (2) trimethylhydroxypropylammonium, trimethylhydroxyethylammonium, and triethylhydroxypropylammonium; , hydroxyalkyl ammonium hydroxides such as triethylhydroxyethylammonium, and acid salts.

The catalyst concentration varies depending on the catalyst used and reaction temperature, but
It is usually selected from the range of lppm to 1.0% based on the diisocyanate.

For example, methanol, ethanol, butanol, ethylene glycol, 1゜3-butanediol, neopentyl glycol, 2-ethyl-1,3 can be used as a cocatalyst during the reaction.
-Alcohols such as hexanediol, trimethylolpropane, polypropylene glycol, and phenol may also be used.

These alcohols can be added at the same time as the isocyanurate-forming catalyst, or they can be reacted with diisocyanate in advance to form urethane bonds before proceeding to the isocyanurate-forming step.

In particular, ethylene glycol, 1,3-butanediol,
Polyhydric alcohols such as neopentyl glycol, 2-ethyl-1°3-hexanediol, 2.2.4-)limethyl-1°3-bentanediol, and trimethylolpropane are disclosed in, for example, JP-A-57-47321; Tokukai 1986
It is also possible to use polyisocyanurate as a modifier, as seen in Japanese Patent No. 181114.

The reaction may be carried out with or without a solvent. Naturally, when using a solvent, one should be selected that does not have reactive activity toward isocyanate groups.

The reaction temperature is 20-160°C, preferably 40-1
Selected from the range of 20”C.

The progress of the reaction can be tracked by NCOI measurement, infrared spectrometry, refractive index measurement, etc. of the reaction solution.

The conversion rate of diisocyanate to isocyanurate is usually about 5 to 70%.

(Conversion rate = amount of product polyisocyanate / weight % of amount of charged diisocyanate) When the reaction reaches the target conversion rate, the reaction is stopped.
When strongly acidic substances commonly used in the past, such as phosphoric acid, sulfuric acid, hydrochloric acid, benzoyl chloride, and monochloroacetic acid, were used as a terminator, the product was significantly discolored; For example, it becomes possible to significantly suppress the degree of coloration of the product.

The terminator used in the present invention has a structure in its molecule, preferably "';
N-), specifically, urea, urea derivatives such as methylurea, 1,1 dimethyl urea, thiourea derivatives such as thiourea, methyl thiourea, 1,1 dimethyl thiourea, etc. , phenyl carbamate, ethyl carbamate, butyl carbamate, and other carbamate esters.

After stopping the reaction and removing the deactivated catalyst if necessary, excess diisocyanate and solvent are removed to obtain a product. Removal of the diisocyanate and solvent is carried out, for example, by a thin evaporator or a solvent extraction method.

(Effects of the Invention) The polyisocyanate having an isocyanurate structure obtained by the method of the present invention has a very low degree of coloring, and is used for example in paints, adhesives, coating materials, casting materials, etc.
It is extremely useful as a curing agent for polyurethane resins such as elastomers and foam materials.

〔Example〕

Hereinafter, the present invention will be further explained with reference to Examples, but the present invention is not limited to the Examples in any way.

In addition, A P used in the evaluation of product coloring degree in Examples.
The HA index was based on ASTM D-1209.

Example 1 1000 g of HDI and 300 g of xylene were placed in a four-L flask equipped with a stirrer, a temperature controller, and a reflux condenser, and while stirring at 60°C under nitrogen, 0.0% of tetramethylammonium caprieto was added as a catalyst. 3g was added in 11 portions every 30 minutes.

The reaction was continued at 60°C, and after 4 hours, when the conversion rate of HDI to isocyanurate reached 21% according to NCO content titration and refractive index measurement, 1. The reaction was stopped by adding 5 g (0.3 g as urea). Deactivated catalyst precipitated simultaneously with the addition of urea.

After removing this precipitate by filtration, using a falling thin film evaporator, the first 0.8 mm 11 g/160 ” C2
2nd time 0. The solvent and unreacted I-(DI) were removed and collected under the conditions of lmmHg/160°C. The viscosity of the obtained product at 25°C was 1,300 mPa-5
, the N GO content was 23.5%.

The obtained polyisocyanate having an isocyanurate structure was a mostly colorless transparent liquid, and its coloring degree was APHA30.

Example 2 The reaction and purification were carried out in the same manner as in Example 1, except that 1.42 g of phenyl carbamate was used instead of 1.5 g of a 20% methanol solution of urea.

The physical properties of the obtained product were the same as those of Example 1, and the degree of coloration was also APHA30.

Example 3 20% methanol of urea? The reaction and purification were carried out in the same manner as in Example 1, except that 2.0 g of a 20% methanol solution of thiourea was used instead of 1.5 g.

The physical properties of the obtained product were the same as those of Example 1, and the degree of coloration was also APHA30.

Comparative Example 1 0 phosphoric acid instead of 1.5 g of 20% methanol solution of urea
．． The reaction and purification were carried out in the same manner as in Example 1, except that 2 g was used.

The physical properties of the obtained product were similar to those of Example 1, but the degree of coloration was APHA200, which was strongly yellowish.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] When producing a polyisocyanate having an isocyanurate structure by catalytic cyclic trimerization of an aliphatic or alicyclic diisocyanate, a deactivator for the catalyst has the following structure in the molecule. A method for manufacturing polyisocyanate characterized by having [a] ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or [b] ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼