JPH0347266B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing isocyanates used as raw materials for isocyanurate foam, and in particular to partial isocyanurate modification of purified, crude diphenylmethane diisocyanate or polymethylene polyphenyl isocyanate (referred to as MDI). Conventionally, isocyanurate foam has been used as a heat insulating material with excellent heat insulating properties, and crude MDI, polymethylene polyphenyl isocyanate, etc. have been used as the raw material isocyanate. However, these isocyanates have aromatic nuclei bonded to each other through methylene groups, and are not sufficient as hard segmenters with heat resistance. As a result of research into raw material isocyanates that have these properties and are likely to thicken during foam foaming, the present inventors have partially converted the isocyanate groups of purified or crude MDI or polymethylene polyphenyl isocyanate into isocyanurates. Isocyanate (referred to as isocyanurate-modified isocyanate or simply modified isocyanate) has a desired isocyanurate content and remains during storage by heating the raw material isocyanate in the presence of a catalyst having a tertiary alkylamine structure. After discovering a method for obtaining a stable isocyanate content that does not change and making various studies, the present invention has been completed. Note that if the isocyanurate foam raw material contains a solvent, it will not form into a foam, so it is necessary that the isocyanate that is the raw material also does not contain a solvent. Therefore, the modified isocyanate for isocyanurate foam raw materials of the present invention is produced without using a solvent. This is different from the production of isocyanates for paint raw materials, which requires a solvent. As a cyclic trimerization catalyst for isocyanate, carboxylic acid salts such as potassium octylate; t-BuoK
Alkoxides such as; triethylenediamine,
2.4.6-(dimethylaminomethyl)phenol,
N, N′, N″-tris(dimethylaminopropyl)
Amines such as hexahydro-S-triazine; phosphines; oxides such as lithium oxide; hydroxides of quaternary salts of N and P; organometallic salts; hydrides such as sodium borohydride; hydrochloric acid , acids such as oxalic acid; composite catalysts such as amine/epoxy compounds; and mixed systems of the above catalysts. Conventionally, methods for obtaining isocyanurate foam using these catalysts or dissolving phenyl isocyanate in an organic solvent and measuring the rate of nurate formation have been carried out.
There is no known technology for converting MDI, crude MDI, or polymethylene polyphenyl isocyanate into isocyanurate in part as a raw material that can be used for forming foams. With conventional catalysts or isocyanurate technology applied to foam formation using conventional catalysts, the raw material isocyanate becomes too reticulated due to isocyanurate formation, and it is difficult to maintain the isocyanate content at a constant level required as a raw material. It's impossible. Among the trimerization catalysts, the present inventors have discovered catalysts having a tertiary alkylamine structure, such as 2.4.6-
By using tri(dimethylaminomethyl)phenol (abbreviated as DMAMP) and adjusting its usage amount and heating conditions, the desired isocyanurate content can be achieved within the range of 3 to 30% of the original isocyanate content. It was possible to obtain a modified isocyanate which has a high residual isocyanate content and whose residual isocyanate content does not change over time or after heating and cooling during subsequent storage. Said
DMAMP to crude MDI with 30.5% NCO content
Add weight% and foam foaming condition temperature e.g. 15
Isocyanurate formation occurs when the mixture is stirred and reacted while being kept at a temperature of wt% added 100
Surprisingly, gelation did not occur when heated and stirred at ℃, and 20% of the original isocyanate
It was found by infrared measurement and titration analysis using reaction with dibutylamine that it has an isocyanurate structure. Furthermore, the isocyanate content of the modified isocyanate treated in this way was measured after being cooled to 15°C and allowed to stand for one day, and the content was the same as above, and no gelation occurred, so it could be used as a raw material for foam. . When the amount of catalyst is the same, the change in isocyanate content becomes smaller by increasing the temperature, and the reaction stops at an early stage at a constant isocyanate content. Furthermore, if the amount of catalyst is increased, the reaction rate will increase and the amount of change in NCO will also increase. Therefore, in order to obtain an isocyanate with a desired isocyanurate modification rate, both the temperature and the amount of catalyst can be controlled. For example, in order to obtain a modified isocyanate raw material with a 10% isocyanurate structure, the reaction temperature can be controlled.
The amount of catalyst may be reduced to 0.6% at 100°C, or the reaction temperature may be increased to 125°C and the reaction may be carried out with vigorous stirring for 10 to 1 hour. In order to stop the reaction at a constant isocyanurate conversion rate at an early stage, the reaction temperature may be increased. This partial isocyanurate modification does not occur with a tertiary amine such as N-dimethylaniline as a catalyst, nor with potassium octylate alone. However, when potassium octylate is added to a catalyst such as N,N',N''-tris(dimethylaminopropyl)hexahydro-S-triazine, the isocyanurate modification rate increases and a additive effect of the catalyst is found. However, due to heating, the isocyanurate conversion rate stops at a certain point, and the reaction no longer progresses even when potassium octoate remains.This isocyanurate modification does not stop because the catalytic function is inhibited by the acid. This is because the acid content in the original raw material isocyanate is
The amount was 0.025% in terms of HCl, and judging from the amount of catalyst used above, it can be seen that this was not due to neutralization by acid. Furthermore, this reaction does not necessarily occur due to an equilibrium between isocyanate and isocyanurate reactions at a certain temperature. Even if the reaction finished liquid is cooled and stirred,
The isocyanurate conversion rate no longer changes, and even if it is further heated, the isocyanate content and isocyanurate conversion rate do not change, and gelation does not occur. Furthermore, the fact that this reaction does not occur due to the volatilization of the catalyst from the reaction solution is due to its molecular structure and molecular weight (for example, 2.4.6-tridimethylaminophenol
MW265) is more obvious. Therefore, blowing inert gas does not volatilize the catalyst and stop the reaction. In other words, it was found that stopping the reaction by heating plays an essential role. In this reaction, the amount of catalyst added varies somewhat depending on the type of catalyst, but when it is added at a concentration of 15% or more, gelation cannot be stopped even if the isocyanate is heated to the maximum, so the amount used naturally increases. The desired modification can usually be effected within an economically advantageous range of catalyst amounts, although there are limitations. The scope of modification of the present invention is also limited by viscosity. When 2/3 or more of the isocyanate is converted into isocyanurate, it is difficult to stir or transport the reaction solution, and the preferred range for practical industrial use is an isocyanurate conversion rate of less than 30%, as shown in the following examples. limited to. Example 1 Raw material crude diphenylmethane diisocyanate (MDI-Cr100 manufactured by Mitsui Nisso) Isocyanate content
31.5%, acid content 0.025%) was placed in a glass reaction vessel and heated to 100°C under nitrogen gas purge. 2.4.6-tri(dimethylaminomethyl) is added as a catalyst while stirring the raw material isocyanate vigorously.
5 c.c. of phenol was added dropwise over 2 minutes. Heat generation started approximately 1 minute after the start of dropping, and after 6 minutes, the liquid temperature rose to 113°C, and then the heat generation gradually subsided and became constant at 102°C after 30 minutes. During that time, sampling was performed to analyze residual Nco% and isocyanurate binding. The relationship is shown in the table below.

[Table] The reaction mass is 1400~ by infrared absorption spectrum.
By tracking the absorption at 1430 cm ^-1 , it was found that the decrease in isocyanate corresponded to the production of isocyanurate. (Figure 1) However, no impurities were found except for a very small amount of what was presumed to be absorption of uretidinedione due to dimerization of isocyanate, and a modified isocyanate in which 15% of the isocyanate was converted to isocyanurate was obtained. It turns out that The reaction mass was rapidly cooled to 40°C and left for one day, but gelation did not occur and the residual Nco% was 26.2%. As a result of measuring the molecular weight distribution of the sample before the reaction, 30 minutes after the reaction, and 1 day after cooling to 40℃ using gel vermi-ation chromatography, it was found that the molecular weight distribution was mainly MDI dinuclear body (4,4' methylene bisphenyl isocyanate).
Because of the decrease in the number of hexanuclear bodies and the increase in the number of hexanuclear bodies or more,
It can be seen that trimerization of MDI has progressed. (Figure 2) Furthermore, the GPC chromatogram after standing for one day was unchanged from that after 30 minutes of reaction. In addition, the isocyanurate conversion rate is the difference between the remaining NCO% at the time of 0 minutes of reaction time and the remaining NCO% after the completion of the reaction (in the case of this example, after 30 minutes of reaction time has passed).
It can be easily calculated by dividing by the remaining NCO% when the reaction time is 0 minutes and converting the value to %. Examples 2 to 5 The same as Example 1 except that the heating temperature was changed. The results are shown on the next page.

[Table] As a result of infrared analysis, it was confirmed that the reaction mass was modified with isocyanurate. Examples 6-7 DMAMP1.5c.c. for 500 grams of MDI-cr100.
was added and reacted for 2 hours with vigorous stirring.
The results are shown in the table below.

[Table] Examples 8 to 11 4,4'-diphenylmethane diisocyanate (MDI-PH manufactured by Mitsui Nisso, isocyanate content 33.3%, acid content 0.01% or less) 1Kg
was added to a two-glass, four-necked reactor and heated to a predetermined temperature under nitrogen gas purge. While stirring vigorously, N,N',N''-tris(dimethylaminopropyl)hexahydro-S-triazine was added dropwise as a catalyst from the dropping funnel over a period of about 3 minutes.The temperature change of the isocyanate was monitored by thermoelectric measurement, with the start of the dropwise addition as the reaction start point. The weight loss of isocyanate was determined by sampling at regular intervals, adding dibutylamine, and titrating with 1/2N hydrochloric acid after heating reaction.Also, a portion of the reaction mass was taken and fixed between two KBr plates. By making a thin film and tracking the process by which isocyanate is modified to isocyanurate, we confirmed that the reaction mass modification was isocyanurate formation and that side reactions such as dimerization were extremely small.Also, some of the samples were made using tetrahydrofuran. Dissolved in and tracked changes in molecular weight distribution by GPC.
It was confirmed that purified MDI decreased and more than six aromatic nuclei were produced. The results are shown in the table below.

【table】

[Table] Examples 12 to 15 A mixture of equal amounts of N,N',N''-tris(dimethylaminopropyl)hexahydro-S-triazine and potassium octylate was used as a catalyst, and MDI-cr200 (Mitsui Nisso) was used as an isocyanate. The procedure was the same as in Example 1, except that 30.5% isocyanate and 200 cps (40°C) viscosity were used.

【table】 [Brief explanation of drawings]

The drawing is an analysis chart for confirming the production of reaction products in Example 1 of the present invention. FIG. 1 is an infrared absorption spectrum, A: isocyanurate absorption, horizontal axis: wave number (1/cm), vertical axis: transmittance.
Figure 2 shows a gluvermeation chromatograph, ...: raw material, -: reaction product, numbers on the graph: molecular weight, horizontal axis: elution time (minutes), vertical axis: elution amount.

Claims (1)

[Claims] 1. Purified diphenylmethane diisocyanate, crude diphenylmethane diisocyanate or polymethylene polyphenyl isocyanate is heated at 30°C in the presence of a catalyst having a tertiary alkylamine structure.
A method for producing a modified isocyanate for use as a raw material for isocyanurate foam, the method comprising converting 3 or more and less than 30% of all isocyanate groups into isocyanurates by heating to 200°C to 200°C.