JP2540634B2 - Process for producing aromatic polyisocyanurate compound - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an aromatic polyisocyanurate compound.

Since the aromatic polyisocyanurate compound has high chemical structure stability, it is known to be a curing agent for polyurethane coatings having excellent curability, heat resistance, and weather resistance.

[Conventional technology]

As a method for producing an aromatic polyisocyanurate compound, there is known a method in which an aromatic polyisocyanate and a predetermined amount of a polyol are subjected to urethane modification, and then a trimerization catalyst is added to perform isocyanurate formation.

For example, JP-A-60-15419 is characterized in that a diol having a number average of 60 to 500 is used as a polyol at the time of urethanization in order to prevent whitening of a coating film with time when used as a paint.

Further, in JP-A-57-2320, a method of using a catalyst is examined for the purpose of suppressing cloudiness of the reaction mixture which occurs with the progress of the trimerization reaction after urethanization.

[Problems to be Solved by the Invention]

Generally, an aromatic isocyanurate compound is known as a fast-drying yellowing type having excellent reactivity with an isocyanate as compared with an aliphatic, alicyclic or aromatic alicyclic isocyanurate compound and having excellent initial drying property. The aromatic isocyanurate compound obtained by the conventional production method is effectively used in a field where a lot of coating work is required, which requires quick drying. However, since the compatibility with the polyol used as the main agent is poor, the types of these polyols are limited and it is not possible to efficiently and economically prepare a variety of urethane paints.

Greatly colored during trimerization reaction.

In order to reduce the polymer which is unfavorable to the compatibility with the main agent, an excessive amount of isocyanate is used and a complicated step of removing unreacted isocyanate such as distillation and extraction is involved.

A large amount of heat is generated in the initial stage of the reaction and heat removal equipment such as an external cooler is required.

When it comes to practical use in painting, bicycles, construction,
When used for each part such as bridges, woodwork products, plywood painting,
In addition to the curability, heat resistance, and weather resistance of paints, a wide variety of coating film physical properties such as hardness, impact resistance, solvent resistance, stain resistance, etc. are required. It has various drawbacks such as not being fully satisfied, and there has not yet been a manufacturing method capable of solving all of these problems.

That is, the problem of the present invention is to solve the above-mentioned problems, in other words, good compatibility with the main agent (polyol), and the degree of coloring is small, unreacted diisocyanate component less coating performance. An improved method for producing an aromatic isocyanurate compound is provided.

[Means for Solving the Invention]

In view of the above problems, the present inventors have conducted extensive studies to solve these problems, and as a result, after using a diol having two or more hydrocarbon substituents in one molecule as a diol and partially urethanizing it, , By improving the compatibility with various main agents (polyols) by converting to isocyanurate, and by adding the catalyst in portions at that time,
It is possible to obtain an aromatic polyisocyanurate compound with low coloration and a small amount of unreacted isocyanate, and the aromatic polyisocyanurate compound obtained by such a method has various conventional physical properties when used as a paint. The present invention has been completed by finding out that it is far superior to.

That is, the present invention relates to a method for producing a urethane prepolymer having an isocyanurate group and an isocyanate group at the end by carrying out a urethanization reaction of an aromatic polyisocyanate and a diol and then carrying out a trimerization reaction in the presence of a catalyst. Further, the diol is an aliphatic diol having two or more hydrocarbon substituents in one molecule, and the catalyst is divided and added to the aromatic polyisocyanurate production method.

 Hereinafter, the present invention will be specifically described.

As the aromatic polyisocyanate used in the method of the present invention, for example, 2,4-tolylene diisocyanate,
2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, 1,4-naphthalene diisocyanate, 1,4-phenylene diisocyanate, 1,3-phenylene diisocyanate, 1-methyl-2, 5-phenylene diisocyanate, 1-methyl-3,5-phenylene diisocyanate,
1-ethyl-2,4-phenylene diisocyanate, 1-
Isopropyl-2,4-phenylene diisocyanate, 1,3
-Dimethyl-4,6-phenylene diisocyanate, 1,4-
Dimethyl-2,5-phenylene diisocyanate, 1-chlorobenzene-2,4-diisocyanate, 1-nitrobenzene-2,4-diisocyanate, 2-nitrobenzene-1,4-diisocyanate, 1-methoxybenzene-2,4
-Diisocyanate, 1-ethoxybenzene-2,4-diisocyanate, biphenyl-2,4'-diisocyanate, 3,3'-dimethylbiphenyl-4,4'-diisocyanate, 3,3'-dimethoxybiphenyl-4,4 ' -Diisocyanate, diphenylmethane-2,2'-diisocyanate, 3,3'-dichlorodiphenylmethane-4,4'-diisocyanate, 3,5-dimethyldiphenylmethane-4,4'-
One or a mixture of two or more of diisocyanate, diphenyl ether-2,4'-diisocyanate, diphenyl ether-4,4'-diisocyanate and the like can be mentioned.

The diol used in the method of the present invention may be any diol having two or more hydrocarbon substituents in one molecule, such as 2,2-diethyl-1,3-propanediol and 2,2. -Dimethyl-1,3-propanediol, 2-n
-Butyl-2-ethyl-1,3-propanediol, 3-
Methyl 1,3-butanediol, 2,2,4-trimethyl-1,3
-Pentanediol, 2-ethyl-1,3-hexanediol, diols such as 2,5-dimethyl-2,5-hexanediol and the like can be mentioned. Among them, 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol are preferable.

The amount of these polyols used is such that the equivalent ratio NCO / OH to isocyanate is in the range of 2-100.

The urethanization reaction can be carried out in the presence or absence of an inert solvent, but it is usually carried out by a method in which the diol component is added dropwise to the aromatic polyisocyanate component mixed with the inert solvent with stirring. It

Examples of the inert solvent used at this time include ethyl acetate, n-butyl acetate, isobutyl acetate, acetone, methyl ethyl ketone, benzene, toluene, xylol, and the like, and one or a mixture of two or more thereof is used. . The amount used is 0.3 to 4 times the weight of the reaction raw material.

The reaction temperature for urethanization is usually 30 to 100 ° C, preferably 5
The reaction time is about 1 to 6 hours.

The trimerization reaction of the present invention can be carried out subsequently to the urethanization reaction.

As the trimerization catalyst used in the method of the present invention, any catalyst can be usually used as long as it is a catalyst used in the trimerization reaction, but a tertiary amine is particularly preferable, and triethylamine and N, N′-dimethyl are preferable. Aniline, tributylamine, N-ethylpiperazine, N, N'-dimethylpiperazine, phenolic Mannich bases, N, N ', N "-
Tris (dimethylaminopropyl) -hexahydro-Sy
Examples thereof include h-triazine. Among them, N, N ', N "-tris (dimethylaminopropyl) -hexahydro-Syh-
Mannich bases of triazines or phenolic compounds are preferred.

The amount of these trimerization catalysts used is 0.01 to 1.0% by weight based on the aromatic polyisocyanate as a raw material.

In the method of the present invention, the trimerization catalyst is added in portions. The number of addition may be 3 to 5 times. If it is less than 3 times, the amount of coloring and residual unreacted isocyanate component is large, and if it is more than 5 times, the effect cannot be further improved, which is disadvantageous in terms of operation. Regarding the addition time, in the first addition, the final one is added at the start of the trimerization reaction about 3 hours before the end of the reaction, and other than that, the addition is performed at about equal intervals.

The reaction time may be 4 to 20 hours, and the reaction temperature may be -5 to 50 ° C, preferably 0 to 30 ° C.

In addition, an antioxidant is added as a coloring inhibitor during the trimerization reaction from the start of the reaction. Examples of the antioxidant include organic phosphorus compounds and phenolic compounds, and phosphorus antioxidants such as triphenyl phosphite and triethyl phosphite are particularly preferable. The amount of the antioxidant used is preferably 0.05 to 1.0% by weight based on the raw material aromatic polyisocyanate.

The trimerization reaction is usually carried out while analyzing the remaining NCO groups in the reaction mixture, and a known terminator is added at a predetermined time point to terminate the trimerization reaction.

Examples of the reaction terminator include acids such as phosphoric acid, sulfuric acid, hydrochloric acid, acetic acid, trifluoroacetic acid, p-toluenesulfonic acid and benzenesulfonic acid, and acid chlorides such as benzoyl chloride and acetyl chloride. The amount used is preferably 1 to 3 times the equivalent amount for neutralizing the tertiary amine.

In the reaction, aromatic polyisocyanate, anti-coloring agent, diol and inert solvent are generally added to a reactor in which the reaction system can be sufficiently agitated, urethanization reaction is carried out under nitrogen atmosphere, and further trimerization catalyst is added in portions. Then, the reaction is allowed to proceed until the NCO% and the unreacted diisocyanate reach predetermined values, at which point a reaction terminator is added to stop the trimerization reaction.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

Example 1 In a four-necked flask equipped with a thermometer, a cooler, a nitrogen introducing tube, and a stirring blade, 99% by weight of 2,4-tolylene diisocyanate,
2,6-Tolylene diisocyanate 1% by weight mixture 81.0
After collecting 1 part by weight and 0.1 part by weight of triphenylphosphite, the reaction system was heated to 60 ° C. in a nitrogen atmosphere. While stirring, the reaction solution was maintained at 60 ° C, 19.0 parts by weight of 2,2,4-trimethyl-1,3-pentanediol and 100 parts by weight of butyl acetate were added, and the reaction solution was heated to 80 ° C to urethanize. The reaction was carried out. The reaction time was 4 hours and the reaction solution was kept at 80 ° C. 3
The reaction was further carried out at 90 ° C. for 1 hour.

After the urethanization reaction, the reaction solution was cooled to 10 ° C., and N, N ′,
0.02 parts by weight of N ″ -tris (dimethylaminopropyl) -hexahydro-Syh-triazine was added every 3 hours in 3 divided portions to carry out an isocyanurate reaction. The reaction time was 7 hours and the reaction solution temperature was always 10 ° C. Finally, 0.08 parts by weight of orthophosphoric acid was added to complete and terminate the reaction.

The progress of the reaction was confirmed by measuring the decreasing NCO content and unreacted diisocyanate. The NCO content was determined by ordinary titration analysis, and the unreacted diisocyanate was determined by gas chromatography.

The NCO% of the obtained product was 8.0% by weight, and the viscosity measured by a Brookfield type rotational viscometer was 55 cps / 25 ° C. As a result of analysis by gas chromatography, the unreacted TDI was 0.30% by weight based on the resin solid content, and the hue was APHA standard solution No. 30 or less.

Example 2 81.0 parts by weight of a mixture of 80% by weight of 2,4-tolylene diisocyanate and 20% by weight of 2,6-tolylene diisocyanate was used as the aromatic polyisocyanate, and the same reaction as in Example 1 was carried out. .

The reaction time for isocyanurate formation was 8 hours.
The obtained product was analyzed to have an NCO content of 8.0% by weight and a viscosity of 57 cp determined by a Brookfield rotational viscometer.
s / 25 ° C. As a result of analysis by gas chromatography, the unreacted TDI was 0.32% by weight based on the resin solid content, and the hue was APHA standard solution No. 30 or less.

Example 3 81.0 parts by weight of a mixture of 65% by weight of 2,4-tolylene diisocyanate and 35% by weight of 2,6-tolylene diisocyanate was used as the aromatic polyisocyanate, and the same reaction as in Example 1 was carried out. .

The reaction time for isocyanurate formation was 9 hours.
The analysis result of the obtained product was NCO content of 8.1% by weight, and the viscosity determined by a Brookfield type rotational viscometer was 60 cps /
25 ° C. As a result of analysis by gas chromatography, the unreacted TDI was 0.36% by weight with respect to the resin solid content, and the hue was APHA standard solution No. 30 or less.

Comparative Example 1 2,4-Tolylene diisocyanate 99 in a four-necked flask
After collecting 81.0 parts by weight of a mixture of 1% by weight of 2,6-tolylene diisocyanate and 0.1 parts by weight of triphenylphosphite, the reaction system was placed in a nitrogen atmosphere and the reaction solution was kept at 60 ° C
The temperature was raised to. While stirring, the reaction solution was maintained at 60 ° C, 19.0 parts by weight of 2,2,4-trimethylpentane-1,3-diol and 100 parts by weight of butyl acetate were added, and the reaction solution was heated to 80 ° C to urethanize. The reaction was carried out.

The reaction time was 4 hours, and the reaction solution was kept at 80 ° C for 3 hours, and further reacted at 90 ° C for 1 hour.

After the urethanization reaction, the reaction solution was cooled to 10 ° C., and N, N ′,
The isocyanurate-forming reaction was carried out by adding 0.02 part by weight of N ″ -tris (dimethylaminopropyl) -hexahydro-Syh-triazine. The reaction time was 5 hours and the reaction solution temperature was always kept at 10 ° C. Finally, ortholine The reaction was completed by adding 0.08 part by weight of acid.

The product obtained was analyzed to have an NCO content of 8.1% by weight, and the viscosity determined by a Brookfield rotational viscometer was 75 cp.
s / 25 ° C. As a result of analysis by gas chromatography, the unreacted TDI was 0.49% by weight with respect to the resin solid content, and the hue was APHA standard solution No.50.

Comparative Example 2 A comparison was made except that a mixture of 80% by weight of 2,4-tolylene diisocyanate and 20% by weight of 2,6-tolylene diisocyanate was used as the aromatic polyisocyanate, and the reaction time for isocyanurate formation was 6 hours. The procedure was as in Example 1.

The obtained product has an NCO content of 8.1% by weight and a viscosity of 90 cp determined by a Brookfield rotational viscometer.
s / 25 ° C. As a result of analysis by gas chromatography, the unreacted TDI was 0.54% by weight with respect to the resin solid content, and the hue was APHA standard solution No. 70.

Comparative Example 3 A comparison was made except that a mixture of 65% by weight of 2,4-tolylene diisocyanate and 35% by weight of 2,6-tolylene diisocyanate was used as the aromatic polyisocyanate, and the reaction time for isocyanurate formation was 7 hours. The procedure was as in Example 1.

The obtained product was analyzed to have an NCO content of 8.0% by weight, and the viscosity determined by a Brookfield rotational viscometer was 110 c.
ps / 25 ° C. As a result of analysis by gas chromatography, unreacted TDI was 0.55% by weight based on the resin solid content,
The hue was APHA standard solution No. 90. The physical properties, coating film properties, and compatibility of the aromatic isocyanurate compounds obtained in Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table-1 and Table-, respectively.
2, shown in Table-3 and Table-4.

[Effects of the Invention] As can be seen from Table-1, Table-2, Table-3 and Table-4, Examples 1 to 3 have less coloration during the trimerization reaction than Comparative Examples 1 to 3 and are unreacted. Low diisocyanate. Further, the compatibility with the polyol is good, and the physical properties of the coating film are also excellent.

Claims (1)

(57) [Claims] 1. A method for producing a urethane prepolymer having an isocyanurate group and an isocyanate group at the end by subjecting an aromatic polyisocyanate and a diol to a urethanization reaction and then performing a trimerization reaction in the presence of a catalyst. The method for producing an aromatic polyisocyanurate, wherein the diol is an aliphatic diol having two or more hydrocarbon substituents in one molecule, and the catalyst is divided and added.