JPH07116163B2 - Method for producing polyisocyanate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an aliphatic or alicyclic polycyclic polyisocyanate having an isocyanurate ring, which is useful as a curing agent when producing a polyurethane resin such as a polyurethane paint or a casting material. The present invention relates to a method for producing an isocyanate.

(Prior Art) Generally, a diisocyanate monomer is used as a catalyst to form a cyclic 3
It is known to use a polyisocyanate having an isocyanurate ring as a raw material for polyurethane by quantifying it, and various catalysts thereof are known. However, as described in, for example, JP-A-57-47319 and JP-A-55-38380, these known catalysts are not suitable for aromatic diisocyanates such as tolylene diisocyanate (TDI). Aliphatic compounds represented by hexamethylene diisocyanate (hereinafter abbreviated as HDI) and 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (hereinafter abbreviated as IPDI), although they have activity.
The selectivity for alicyclic diisocyanates is high, and the production of aliphatic / alicyclic polyisocyanurates is relatively difficult.

On the other hand, the aliphatic / alicyclic polyisocyanate having an isocyanurate structure has markedly higher performance than the aromatic polyisocyanurate in terms of its weather resistance, and its industrial value is extremely high. Therefore, regarding the production of HDI polyisocyanurate, the above-mentioned JP-A-57-4731 is used.
9, JP-A-55-38380, JP-A-61-42523, JP-A-60-1811
Many patent applications such as 14 have been filed.

The catalysts proposed by these patent applications are Na, K, Zn salts of alkylcarboxylic acids, tetraalkylammonium hydroxide hydroxyalkyl quaternary ammonium salts, and the like.

(Problems to be Solved by the Invention) However, among these catalysts, alkylcarboxylic acid
K, Na, Zn salt compounds, the catalyst does not dissolve in diisocyanate monomers such as HDI, the reaction system becomes a heterogeneous system,
There are many problems in the reproducibility of the reaction, the controllability of the reaction, etc.

On the other hand, in a system using a quaternary ammonium salt compound as a catalyst, a homogeneous system can be achieved. Among these, the hydroxyalkyl quaternary ammonium salt is reactive with the isocyanate group in the alkyl group around the nitrogen atom. Since it has a hydroxyl group having a group, the addition reaction between the diisocyanate monomer or the produced polyisocyanurate and the catalyst occurs during the isocyanurate-forming reaction, and it becomes very difficult to avoid mixing the catalyst residue into the product. .

Further, although tetraalkyl quaternary ammonium hydroxide is an excellent catalyst system, it is not preferable because it has a high self-decomposability and causes coloration and deterioration of catalyst activity due to decomposition and oxidation during storage of the catalyst.

Therefore, in the art, (1) the isocyanurate-forming activity of an aliphatic / alicyclic diisocyanate,
(2) A homogeneous reaction system is achieved, resulting in excellent controllability and reproducibility of the reaction, (3) Easy removal of the deactivated catalyst after completion of the reaction, (4) There has been a long-felt demand for a technique for producing an aliphatic / alicyclic polyisocyanurate that is excellent in storage stability.

(Means for Solving Problems) As a result of intensive studies in view of these points, the present inventors have found that the above problems can be overcome by using a specific quaternary ammonium carboxylate as a catalyst. The present invention has been completed by finding the present invention, and further finding out the production conditions capable of obtaining a product satisfying various physical properties and safety required as a polyurethane resin curing agent.

That is, the present invention is to produce a polyisocyanate having a polyisocyanurate structure by cyclic trimerization of an isocyanate group of an aliphatic / alicyclic diisocyanate or a pre-urethanization reaction product thereof, and a structure represented by the following formula (I) is used as a catalyst. the use 30~800ppm to diisocyanate tetraalkylammonium carboxylate ^{having, R 1 R 2 R 3 R} 4 N + / R 5 COO - (I) ( wherein, R ¹ to R ⁴ is C 1 -C ~ 4 alkyl groups or benzyl groups, which may be the same or different, and the total number of carbon atoms of R ^{1 to} R ⁴ is 4 to 12, and R ⁵ is alkyl of 1 to 18 carbon atoms. Group, a phenyl group or a benzyl group.) At a conversion of diisocyanate to a product of 10 to 60%, deactivate the catalyst by adding an acidic substance to stop the reaction, and precipitate by deactivation. Catalyst residue was removed, further, by removing the excess diisocyanate monomer from the reaction system,
0.7% diisocyanate monomer content in the product
The present invention provides a manufacturing method characterized by the following three points.

The conversion rate here is the weight% of the final product with respect to the charged diisocyanate.

Examples of the aliphatic / alicyclic diisocyanate used in the present invention include HDI, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, dodecamethylene diisocyanate and 2,6-diisocyanatomethylcaproic acid. Ate, 1,3-cyclohexane diisocyanate,
1,4-Cyclohexane diisocyanate, IPDI, 4,4'-
Methylene bis (cyclohexyl isocyanate), methyl-2,4-cyclohexane diisocyanate, methyl-
2,6-Cyclohexane diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, 1,4-bis (isocyanatomethyl) cyclohexane, m- or p-xylylene diisocyanate, 1,3- or 1,4-tetra Methyl xylylene diisocyanate etc. are mentioned. It is also possible to use a mixture of two or more of these diisocyanate monomers.

These diisocyanate monomers are arbitrarily selected according to the intended use of the final product, but HDI is preferably used when the final product having a low viscosity is targeted.

Further, a pre-urethanization reaction product of these diisocyanate monomers and a monofunctional to trifunctional alcohol can also be suitably used as a raw material. Examples of the 1-3 functional alcohol used here include, for example, methanol, ethanol, various butanols, 2-ethyl-hexanol, ethylene glycol, 1,2- or 1,3-propylene glycol, 1,3- Or 1,4- or 2,3-butylene glycol, 1,6-hexanediol, neopentyl glycol, neopentyl glycol hydroxypivalate ester, 2-ethyl-1,3-hexanediol, trimethylolpropane, glycerin, 1 Examples thereof include low molecular weight compounds such as 2,2,6-hexanetriol and polyester polyols and polyether polyols having a molecular weight of about 200 to 10,000.

Among these, preferred from the viewpoint of compatibility between the product and other resins are 1,3- or 2,3-butanediol, neopentyl glycol, neopentyl glycol hydroxypivalic acid ester, and 2-ethyl-1. Examples thereof include diols having a side chain such as 3,3-hexanediol.

NC during preliminary reaction of alcohol and diisocyanate monomer
The O / OH equivalent ratio is selected from a value of about 10 to 100 according to the purpose.

The compound used as the catalyst is a tetraalkylammonium carboxylate represented by the general formula (I) R ¹ R ² R ³ R ⁴ N ⁺ / R ⁵ COO ⁻ (I).

R ^{1 to} R ⁴ are selected from methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl group and benzyl group, and R ¹ to R ⁴ It is necessary that the total carbon number of R ⁴ is 4 to 12. If the total number of carbon atoms exceeds 12, as described later, the deactivated catalyst after stopping the isocyanurate-forming reaction with an acidic compound is dissolved in the reaction system, and removal becomes difficult, which is not preferable. R ⁵ is selected from an alkyl group having 1 to 18 carbon atoms, an optionally substituted phenyl group or a benzyl group.

Examples of such a catalyst include, for example, tetramethylammonium, monoethyltrimethylammonium, diethyldimethylammonium, triethylmonoethylammonium, tetraethylammonium, tetrapropylammonium, monomethyltripropylammonium,
Monoethyltripropylammonium, tetrabutylammonium, monomethyltributylammonium, monoethyltributylammonium, trimethylbenzylammonium acetate, propionate, hexanoate, 2-ethylhexanoate, caprate, naphthenate, respectively. Examples thereof include myristate, stearate, benzoate and the like.

The amount of these catalysts used is 30 to 80 relative to the raw material diisocyanate monomer or its pre-urethane reaction product.
0 ppm is appropriate. If the amount of the catalyst is too small, it is not appropriate because it takes too long to achieve the desired conversion rate, and if the amount of the catalyst is too large, the rate of the isocyanurate-forming reaction is too fast and a large amount of heat is generated. It becomes difficult to control the reaction.

During the reaction, a solvent may or may not be used, but the use of a solvent having no reaction activity with the isocyanate group makes it easier to control the reaction.

Examples of these solvents include ethyl acetate, butyl acetate, ester (ether) such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, benzene, toluene, xylene,
Aromatic hydrocarbons such as ethylbenzene and mesitylene, and phosphoric acid esters such as trimethyl phosphate and triethyl phosphate can be used. Of course, it is also possible to use a mixture of two or more solvents.

Of these solvents, aromatic hydrocarbons are particularly preferable in that they suppress the coloration of the reaction system and that the deactivated catalyst has a shape that easily passes through.

The amount of the solvent used is 1/10 by weight based on the raw material diisocyanate monomer or its pre-urethane reaction product.
About 1/2 is appropriate.

The isocyanurate-forming reaction is usually performed at 30 to 120 ° C, preferably 50 to 100 ° C. The progress of the reaction can be performed by NCO titration of the reaction solution, refractive index, density, IR measurement and the like.

When the reaction reaches a desired conversion rate, the catalyst is inactivated by adding a terminating agent to stop the reaction. This conversion rate is 10 ~
It is appropriate to select within the range of 60%. If the reaction is suppressed at a low conversion rate, it is possible to obtain a product having a lower viscosity, but if the conversion rate is 10% or less, productivity is poor and it is not preferable. On the other hand, when the conversion rate is 60% or more, the viscosity of the final product becomes too high, which is not preferable.

Examples of the reaction terminator include acidic substances such as hydrochloric acid, phosphoric acid, sulfuric acid, dichloroacetic acid, trichloroacetic acid, henzoyl chloride and acetyl chloride.

It is preferable that the catalyst deactivated by these terminating agents becomes insoluble in the reaction system and can be removed due to excess because it is possible to avoid contamination of impurities in the product. From this viewpoint, hydrochloric acid, phosphoric acid, and sulfuric acid are used. It is particularly preferred to use an inorganic acid such as

When a hydroxyalkyl quaternary ammonium salt such as 2-hydroxyethyltrimethylammonium (choline) or 2-hydroxypropyltrimethylammonium hydroxide or carboxylate is used as a catalyst, Precipitation from the reaction system is very difficult and not suitable. ^{Further, R 1 R 2 R 3 R} 4 N + / R 5 COO is the catalyst of the present invention ^- even if the carbon atoms in total of R ¹ to R ⁴ exceeds 12, will also deactivated catalyst is dissolved in the system However, it is not preferable because it cannot be distinguished.

Thus the conversion of diisocyanate monomer to product
After the reaction is completed at 10 to 60%, unreacted diisocyanate monomer and solvent are removed from the reaction solution for purification. As the purification method, there are vacuum distillation, solvent extraction and the like, but in general, a falling film type evaporator is preferably used.

It is necessary to sufficiently remove the diisocyanate monomer from this product and to make the content of the diisocyanate monomer in the product 0.7% by weight or less. If this value exceeds 0.7% by weight, the vapor pressure of the diisocyanate monomer in the product may reach a level at which there is a risk of adversely affecting the human body, which is unfavorable for the safety and health of workers.

(Effects of the Invention) The features of the present invention in terms of manufacturing are summarized as follows.

(1) The catalyst activity is high, and the reaction proceeds with a small amount of the catalyst used.

(2) The leaving stability of the catalyst is excellent.

(3) It is a homogeneous reaction and is excellent in controllability and reproducibility of the reaction.

(4) It is easy to remove the catalyst after deactivation, and it is easy to obtain a product containing no impurities.

(5) It is possible to obtain a low-viscosity product that is practically easy to handle.

(6), the product contains substantially no diisocyanate monomer, and a highly safe product can be obtained.

The aliphatic having an isocyanurate ring thus obtained
Alicyclic polyisocyanates are very useful as a polyurethane raw material having excellent weather resistance and heat resistance, for example, a curing agent for coating materials, a curing agent for casting materials, a thermoplastic resin cross-linking agent, and the like.
In addition, since it does not substantially contain a diisocyanate monomer, which is a problem for workers' hygiene, it is excellent in safety.

(Examples) Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited to the examples.

Example 1 In a four-necked flask equipped with a stirrer, a cooling tube, and a thermometer
HDI of 1000 g, ethylene glycol monoethyl ether acetate (hereinafter abbreviated as cello acetate) of 250 g, and neopentyl glycol of 22 g are charged, and a preliminary urethane reaction is carried out at 60 ° C. for 2 hours with stirring.

Next, 0.2 g of tetramethylammonium acetate as a catalyst is dissolved in 0.2 g of methanol and added, and an isocyanurate-forming reaction is carried out at 60 ° C. for 4 hours. The reaction proceeds in a homogeneous system. 89% phosphoric acid 0.18g was added as a terminator, and after stopping the reaction, heating was continued at 60 ℃ for 1 hour, and then it was cooled to room temperature, then the deactivating catalyst tetramethylammonium phosphate was converted into crystals. To deposit.

After removing this precipitate by filtration, using a falling film evaporator, the first time is 0.8 mmHg / 150 ° C and the second time is 0.1 mmHg / 160 ° C.
The solvent and unreacted HDI are removed and collected under the conditions of.

The product obtained is a pale yellow, transparent liquid with a viscosity of
4500cps / 25 ℃, NCO content is 20.4%, Free HDI content is 0.1%
It was. Product yield 390g, conversion from HDI 39%
It was.

Examples 2 to 8 Polyisocyanates having an isocyanurate ring were obtained in the same manner as in Example 1 under the formulations and conditions shown in Table 1. The physical properties of the obtained product are summarized in the lower column of Table 1.

The contents of the abbreviations used in Table 1 are shown below.

1,3-BG: 1,3-Butanediol NPG: Neopentyl glycol TEA / 2EH: Tetraethylammonium 2-ethylhexanoate TMA / C ₉ : Tetramethylammonium capryate TBA / C ₁ : Tetrabutylammonium Acetate BZTMA / C ₉ : Benzyltrimethylammonium capryate ETMA / C ₁ : Ethyltrimethylammonium acetate Comparative Example 1 When a 50% methanol solution of tetramethylammonium hydroxide was prepared and allowed to stand at room temperature for 2 weeks, it was colored brown and a strong amine odor was observed. HDI isocyanurate using this product was synthesized under the same conditions as in Example 1, but strong coloring was observed in the product.

On the other hand, in a 50% methanol solution of tetramethylammonium acetate, no alteration was observed even after standing at room temperature for 1 month.

Comparative Example 2 When 2-hydroxyethyltrimethylammonium acetate (choline acetate) was used in place of tetramethylammonium acetate and the same reaction as in Example 1 was performed, the deactivated catalyst was precipitated as crystals even after the addition of phosphoric acid. However, the reaction solution was in a cloudy state. When this reaction solution was passed and purified by a falling film evaporator in the same manner as in Example 1, the resulting product was turbid.

Comparative Example 3 The same reaction as in Example 1 was carried out using benzyltriethylammonium acetate instead of tetramethylammonium acetate. Even after the addition of phosphoric acid, the reaction system was uniform and it was impossible to remove the deactivated catalyst by excess.

Comparative Example 4 In the system of Example 7, the amount of catalyst was increased to 0.5 g, and reaction, termination and purification operations were performed. The conversion of HDI to the product was 65%, but the viscosity of the obtained product was 100,000 cps or more at 25 ℃ and it was a very viscous liquid.

Comparative Example 5 When the amount of catalyst in the system of Example 1 was changed to 1 g, the reaction could not be controlled and the temperature of the reaction solution continued to rise. When the temperature of the reaction solution reached 120 ° C., an excessive amount of phosphoric acid was added to interrupt the reaction.

Comparative Example 6 When the catalyst amount was changed to 0.02 g in the system of Example 1, formation of isocyanurate was not recognized.

Claims (2)

[Claims] 1. When a polyisocyanate having a polyisocyanurate structure is produced by cyclic trimerization of an isocyanate group of an aliphatic / alicyclic diisocyanate or a pre-urethanization reaction product thereof, a catalyst of the formula (I) R ¹ R ^{2 is used. R 3 R 4 N + / R} 5 COO - (I) ( wherein, R ¹ to R ⁴ represents an alkyl group or a benzyl group having 1 to 4 carbon atoms which may each be the same or different, and, R ^{1 to} R ⁴ has a total carbon number of 4 to 12 and R ⁵ represents an alkyl group having 1 to 18 carbon atoms, a phenyl group or a benzyl group.) To a diisocyanate. Use 30 ~ 800ppm,
At a conversion rate of diisocyanate to a product of 10 to 60%, the reaction was stopped by deactivating the catalyst by adding an acidic substance, and then the catalyst residue precipitated by the deactivation was removed.
A method for producing a polyisocyanate, characterized in that the excess diisocyanate monomer is removed from the reaction system so that the content of the diisocyanate monomer in the product polyisocyanate is 0.7% or less. 2. The method for producing a polyisocyanate according to claim 1, wherein the diisocyanate is hexamethylene diisocyanate.