CN1789241B - Process for preparing liquid, storage-stable, low-color-index organic isocyanates containing carbodiimide and/or uretonimine groups - Google Patents

Abstract

The present invention relates to a kind of method for preparing the isocyanate mixture of liquid state, storage stability, low color index, containing carbodiimide (CD) and/or uretonimine (UI) group, the isocyanate mixture and the isocyanate mixture prepared by this method and Their use in the production of blends with other isocyanates or in the production of prepolymers and polyurethane plastics, preferably polyurethane foams, containing isocyanate groups.

Description

Process for the preparation of liquid, storage-stable, low color index organic isocyanates containing carbodiimide and/or uretonimine groups

technical field

The invention relates to a process for the preparation of liquid, storage-stable, low color index isocyanate mixtures containing carbodiimide (CD) and/or uretone imine (UI) groups, which can be obtained isocyanate mixtures, and their use in the production of blends with other isocyanates or in the production of prepolymers and polyurethane plastics, preferably polyurethane foams, containing isocyanate groups.

Background technique

Isocyanate mixtures containing CD and/or UI groups can be obtained simply by using high-efficiency catalysts of cyclopentenylphosphine (phospholine) series, especially efficient catalysts of cyclopentenylphosphine oxide series, according to US-A-2853473, US-A -6120699 and EP-A-515933 to produce.

On the one hand, the high catalytic activity of cyclopentenylphosphine catalysts, especially cyclopentenylphosphine oxide catalysts, is desired in order to activate the carbodiimidization reaction under mild temperature conditions, but on the other hand, until now, No method is known to ensure that the catalytic action of cyclopentenylphosphine or cyclopentenylphosphine oxide is effectively terminated without restriction. Carbodiimidized isocyanates tend to post-react, i.e., they gasify due to the formation of _CO2 . This will lead, for example, to an increase in pressure in the storage container, especially at high temperatures.

Attempts to find effective means of terminating cyclopentenylphosphine catalysis have been numerous. Such terminators are mentioned, for example, in the specifications of DE-A-2537685, EP-A-515933, EP-A-609698 and US-A-6120699, which include for example acids, acid chlorides, chloroformic acid, formic Silylation acids and halides of main group elements. Catalysis termination with acids, which may also be present in the form of acid chlorides, is less effective.

According to the publication of EP-A-515933, the isocyanate mixture containing CD/UI prepared by the catalysis of cyclopentenylphosphine is at least equimolar with the catalyst used, preferably 1-2 times the molar amount of trimethylformazine Silyl trifluoromethanesulfonate (TMST) to terminate. However, practice has shown that the CD/UI-containing isocyanates produced in this way are not generally suitable for the production of prepolymers, ie reaction products of these CD/UI-containing isocyanates and polyols. The reaction products thus produced from polyols and CD/UI-modified isocyanates tend to vaporize, which can lead to an increase in pressure in the transfer vessel or to foaming during handling of these products.

This problem can be avoided by terminating the cyclopentenylphosphine catalyst with silylation acid in accordance with the high molar equivalence ratios used in EP-A-515933 (eg 5:1 to 10:1 ratio to catalyst). In practice, however, it was subsequently found that the color index of the resulting CD/UI-modified isocyanates was rather poor. So, too, are the prepolymers produced with them.

The same is true if the cyclopentenylphosphine catalyst is terminated with an acid of the trifluoromethanesulfonic acid type according to US-A-6120699. The color index of prepolymers made from these materials increases considerably.

Contents of the invention

The present invention therefore provides a process for the preparation of liquid, storage-stable, lighter isocyanate mixtures containing carbodiimide and/or uretonimine groups which does not have the disadvantages mentioned above and which produces liquid, storage-stable Stable, low color index isocyanate mixture.

These and other advantages and benefits of the invention will be apparent from the detailed description of the invention that follows.

Detailed ways

The invention will now be described for purposes of illustration. Except in the working examples, or unless indicated to the contrary, all numbers in the specification expressing amounts, percentages, OH numbers, functionalities, etc. are to be understood in all cases as modified by the term "about". Equivalent weights and molecular weights given herein in Daltons (Da) are number average equivalent weights and number average molecular weights, respectively, unless indicated to the contrary.

The invention relates to a process for the preparation of organic isocyanates with carbodiimide and/or uretonimine groups, wherein one or more of Hazen (Hazen) color index ≤ 100APHA is used as a catalyst of cyclopentenylphosphine , It is preferred that the organic isocyanate with ≤50 APHA is partially carbodiimidated, and then the carbodiimidated reaction is terminated. The method is characterized in that an alkylating agent is used as a terminator.

The Hazen color index can be measured according to DIN/EN/ISO6271-2 (draft, September 2002) without solvent, with water as reference, and a layer thickness of 5 cm. The measuring device used can be, for example, a Dr. Lange LICO300 photometer.

Preference is given to using strong alkylating agents. Alkylating agents are substances of the general formula R-X, where R represents an organic group and X is a so-called leaving group. In strong alkylating agents, X constitutes a good leaving group, that is, a group with a very low nucleophilicity. In other words, X constitutes a good leaving group if it is derived from a strong acid, HX, and thus is very weakly basic. Trialkyloxonium compounds, trifluoromethanesulfonates, and dialkylsulfates are exemplified as compounds with good leaving groups in Advanced Organic Chemistry by Jerry March, 3rd Edition (1985), published by John Wiley & Sons , p. 135.

The invention also relates to organic isocyanates having carbodiimide and/or uretonimine groups obtainable by the process described above. These organic isocyanates with carbodiimide and/or uretonimine groups are liquid at room temperature and, depending on the CD/UI content and/or the isocyanate used, also liquid at low temperatures (e.g. 0 °C) .

The invention also provides the use of an organic isocyanate according to the invention having carbodiimide and/or uretonimine groups in the production of blends with other isocyanates, or in the production of isocyanate group-containing compounds with an improved color index. application of prepolymers.

Finally, the invention also provides the organic isocyanates according to the invention having carbodiimide and/or uretonimine groups and the isocyanate blends produced therefrom and/or prepolymers with improved color index in polyurethane plastics application in production.

Surprisingly, liquid, storage-stable isocyanate mixtures with a low color index can be obtained by the process according to the invention, in contrast to the teaching of DE-A-2504334, in which, for example, with alkane Catalyst deactivation by baselating agents was found to be insufficient.

Alkylating agents are also disclosed in US-A-4424288 for deactivating catalysts, wherein crude polyphenylpolymethylene polyisocyanate is used as starting material which can be prepared by aniline-formaldehyde condensation followed by phosgenation This yields ('crude MDI') which contains at most 70% by weight of isomers of methylene diphenyl diisocyanate. However, the raw material itself has a dark color, so a light-colored product cannot be obtained by this method.

Any organic isocyanate having a Hazen color index ≤ 100 APHA, preferably ≤ 50 APHA can be used as starting material for the process of the present invention. However, the method according to the invention is preferably used to carry out the carbodiimidization of organic diisocyanates, which are used in polyurethane chemistry.

The following are particularly suitable:

Aromatic diisocyanates, such as toluene-2,4- and/or toluene-2,6-diisocyanate (TDI), 2,2'-, 2,4'- and/or 4,4'-methylene diisocyanate Phenyl diisocyanate (MDI) or any mixture of such aromatic diisocyanates,

Polyisocyanate mixtures of the methylene diphenyl series containing 80% to 100% by weight of monomeric methylene diphenyl diisocyanate isomers and 0 to 20% by weight of higher than difunctional methylene Diphenyl series polyisocyanate, wherein methylene diphenyl diisocyanate isomer is 0 to 100% by weight of 4,4'-methylene diphenyl diisocyanate, 100% by weight to 0 of 2,4 '-methylene diphenyl diisocyanate and 0 to 8% by weight of 2,2'-methylene diphenyl diisocyanate, and the sum of the percentages given is 100%.

Organic isocyanates preferably used as starting materials are especially aromatic diisocyanates, such as toluene-2,4- and/or toluene-2,6-diisocyanate (TDI), 2,2'-, 2,4'- and/or 4,4'-methylene diphenyl diisocyanate (MDI) or any mixture of such aromatic diisocyanates. For 2,2'-, 2,4'- and/or 4,4'-methylene diphenyl diisocyanate (MDI) or any mixture of such aromatic diisocyanates, in the raw material (organic isocyanate) 2, The total amount of 2'-, 2,4'- and/or 4,4'-methylene diphenyl diisocyanate is at least 85% by weight, and the methylene diphenyl diisocyanate isomer is 0 to 100% by weight % of 4,4'-methylene diphenyl diisocyanate, 100 to 0% by weight of 2,4'-methylene diphenyl diisocyanate and 0 to 8% by weight of 2,2'-methylene Diphenyl diisocyanate, and the percentages given add up to 100%, are particularly preferred. For 2,2'-, 2,4'- and/or 4,4'-methylene diphenyl diisocyanate (MDI) or any mixture of such aromatic diisocyanates, in the raw material (organic isocyanate) 2, The total amount of 2'-, 2,4'- and/or 4,4'-methylene diphenyl diisocyanate is at least 90% by weight, and the isomers of methylene diphenyl diisocyanate are 0 to 100% by weight % of 4,4'-methylene diphenyl diisocyanate, 100% to 0% by weight of 2,4'-methylene diphenyl diisocyanate and 0 to 8% by weight of 2,2'-methylene Diphenyl diisocyanate, and the sum of the stated percentages to 100%, is very particularly preferred. In particular, for 2,2'-, 2,4'- and/or 4,4'-methylene diphenyl diisocyanate (MDI) or any mixture of such aromatic diisocyanates, raw materials (organic isocyanates) The total amount of 2,2'-, 2,4'- and/or 4,4'-methylene diphenyl diisocyanate is at least 99% by weight, and the isomer of methylene diphenyl diisocyanate is 0 to 100% by weight of 4,4'-methylene diphenyl diisocyanate, 100 to 0% by weight of 2,4'-methylene diphenyl diisocyanate and 0 to 8% by weight of 2,2'- Methylene diphenyl diisocyanate, and the sum of the stated percentages to 100%, is most particularly preferred.

The process according to the invention is carried out in the presence of catalysts of the cyclopentenylphosphine class. Catalysts of the cyclopentenylphosphine class are known, for example from EP-A-515933 and US-A-6120699. Typical examples of these catalysts are eg known in the art mixtures of cyclopentenylphosphine oxides of the general formula.

和

and

The amount of catalyst used depends on the quality of the raw material isocyanate. The easiest way to determine the amount of catalyst in each case is to perform a preliminary test.

The carbodiimidization reaction is conventionally carried out at a temperature of 50°C to 150°C, preferably at a temperature of 60°C to 100°C. However, obviously higher reaction temperatures are also possible (up to 280° C.). The optimum reaction temperature depends on the starting isocyanate and/or catalyst used and can be determined in simple preliminary tests.

Carbodiimidization generally occurs at a degree of carbodiimidization (the degree of carbodiimidization is the percentage of carbodiimidized isocyanate groups relative to the total amount of isocyanate groups present in the raw isocyanate) reaching 3 % to 50%, preferably 5% to 30%.

The degree of carbodiimidation can be determined by determining the NCO value during the performance of the process according to the invention, for example by titration or in situ analysis methods known to those skilled in the art. Suitable in situ analysis methods are eg near-infrared analysis or mid-infrared analysis.

The degree of carbodiimidation can also be determined, for example, by the amount of carbon dioxide which escapes from the reaction mixture during the performance of the process according to the invention. Thus, volumetric measurements of carbon dioxide provide information on the degree of carbodiimidization achieved at any point in time.

Furthermore, other suitable ex-situ or in-situ process monitoring methods known to those skilled in the art can in principle also be used.

In order to terminate the carbodiimidization reaction, an alkylating agent or various alkylating agents or various alkylating agents are used in at least an equimolar amount with the catalyst, preferably in a molar excess of 1-20 times, and most preferably in a molar excess of 1-10 times A mixture of agents was used as a terminator. An alkylating agent or a mixture of alkylating agents is preferably used as the sole terminator.

Alkylating agents are presumed to be capable of hydrocarbylating and thus deactivating cyclopentenylphosphine oxide catalysts. All alkylating agents which are capable of deactivating the cyclopentenylphosphine oxide catalysts by alkylation and thus terminating the carbodiimidation reaction are therefore suitable terminators according to the invention. Suitable alkylating agents can be readily determined by those skilled in the art by simple testing.

Preferred alkylating agents are esters of trifluoromethanesulfonic acid, esters of mineral acids, preferably strong mineral acids, or trialkyloxonium compounds.

Suitable esters of trifluoromethanesulfonic acid are in particular compounds of the structure CF ₃ -SO ₃ -R ¹ , wherein R ¹ is (cyclo)aliphatic or araliphatic, and R ¹ may optionally contain carbon and hydrogen Elements. R ¹ may have a branched or linear carbon chain and may optionally also have one or more carbon-carbon multiple bonds. Preference is given to aliphatic esters of triflate, particularly preferred are methyl triflate, ethyl triflate, propyl triflate, butyl triflate and triflate Phenyl fluoromethanesulfonate.

Suitable esters of strong mineral acids are, for example, esters of sulfuric acid or phosphoric acid, i.e. compounds of the structure SO ₂ (OR ³ ) ₂ or OP(OR ³ ) ₃ , wherein R ³ is (cyclo)aliphatic or araliphatic, R ³ may also optionally contain elements other than carbon and hydrogen. ^R3 may have a branched or linear carbon chain and may optionally also have one or more carbon-carbon multiple bonds. Preferred are aliphatic esters of sulfuric acid, particularly preferred are dimethyl sulfate and diethyl sulfate.

Suitable trialkyloxonium compounds are, for example, compounds of the structure R ⁴ ₃ OY, wherein R ⁴ is methyl or ethyl. Y represents a non-nucleophilic anion such as tetrafluoroborate, hexafluorophosphate or hexafluoroantimonate.

An alternative to the exclusive use of alkylating agents as terminators is the use of alkylating agents and acids and/or acid chlorides and/or sulfonates as additional stabilizers according to the invention. By also using an additional stabilizer, the amount of alkylating agent used can be reduced. This stabilizer can be added at the same time as the terminator, or in a subsequent step.

Optionally halogenated, aliphatic and/or cycloaliphatic and/or aromatic mono-, di- and/or polycarboxylic acids such as acetic acid, adipic acid, cyclohexanedicarboxylic acid, alpha-chloropropionic acid, benzene Formic acid, phthalic acid, isophthalic acid, etc., as well as sulfonic acid, HCl, sulfuric acid and/or phosphoric acid or their monobasic and/or dibasic esters, such as dibutyl phosphate, can be used as acids. Acid chlorides and carbamoyl chlorides derived from optionally halogenated, aliphatic and/or cycloaliphatic and/or aromatic monohydric, dihydric and/or polycarboxylic acids or sulfonic acids such as n-butylcarbamoyl chloride can be used as acid chloride. Methyl p-toluenesulfonate, ethyl p-toluenesulfonate can be used as sulfonate, for example.

Corresponding to organic isocyanates having carbodiimide and/or uretonimine groups, the total amount of added additional stabilizers is 10 ppm to 1000 ppm (1 ppm is 1 part by weight/1000000 parts by weight), preferably 10 ppm to 500ppm, more preferably 50ppm to 250ppm.

The carbodiimidized reaction product may contain color stabilizers conventionally added to the isocyanate. The timing of adding these stabilizers is not critical. The color stabilizer can be added to the raw isocyanate before the carbodiimidization or to the reaction product once the reaction is complete. It is also possible to add a color stabilizer to both the raw material and the reaction product. Such stabilizers are generally known to those skilled in the art and may include, for example, substances selected from sterically hindered phenols, phosphites and tertiary amines. The color stabilizers can each be used alone or in admixture with other representatives of the same and different substance groups. The color stabilizer is used in an order of magnitude known to those skilled in the art, relative to the raw material isocyanate or carbodiimidized reaction product, the single substance or the mixture is usually 100 ppm to 10000 ppm.

It has been found that the addition of an alkylating agent alone or in combination with an acid and/or acid chloride and/or sulfonate as an additional stabilizer is effective in terminating cyclopentenylphosphine by the process according to the invention. At the same time, the isocyanate product and the prepolymer obtained from it have a lower color index. When using silylation acid as a terminator according to the prior art (EP-A-515933), the catalytic effect of cyclopentenylphosphine is effectively terminated only by adding a large amount of silylation acid, but this leads to The color index of the isocyanate mixtures thus produced and of the prepolymers produced therefrom is increased.

The prepolymers containing isocyanate groups are produced by reacting organic isocyanates carrying carbodiimide and/or uretonimine groups prepared according to the process of the invention with polyols customary in polyurethane chemistry. Suitable polyols are monovalent and polyvalent alcohols such as ethylene glycol, trimethylolpropane, propylene glycol, having a molecular weight of 62 g/mol to 599 g/mol, preferably 62 g/mol to 300 g/mol -1,2, butanediol-1,2 or butanediol-2,3, hexanediol, octanediol, dodecyldiol and/or octadecyldiol, but especially polyurethane chemistry Among known high molecular weight polyether polyols and/or polyester polyols with a molecular weight of 600 g/mol to 8000 g/mol, preferably 800 g/mol to 4000 g/mol, at least two, usually is 2 to 8, preferably 2 to 4 primary and/or secondary hydroxyl groups. Examples of such polyols are disclosed in US-PS4218543, column 7, line 29 to column 9, line 32.

The advantage of the process according to the invention is obvious to the person skilled in the art that isocyanates containing carbodiimide and/or uretonimine groups and the prepolymers produced therefrom are storage-stable and relatively colored. shallow.

These organic isocyanates with carbodiimide and/uretonimine groups and the prepolymers produced by their reaction with polyols are valuable raw materials for the production of polyurethane plastics, which are produced by combining with Polyols are realized via polyaddition reactions (for example, with polyether polyols and polyester polyols).

Example

The present invention is further illustrated by the following examples, but not limited thereto.

raw material:

Isocyanate 4,4-methylene diphenyl diisocyanate, NCO content: 33.6% by weight (DESMODUR44M, Bayer AG)

Cyclopentenyl phosphine oxide catalysts 1-methyl-1-oxo-1-phosphole-2-ene and 1-methyl-1-oxo-1-phosphole-3-ene industry Grade mixture, the concentration in toluene is 10%.

Polyol Polyether of propylene and ethylene oxide units, 80%-90% primary OH groups, functionality 3, OH value 28 mgKOH/g and viscosity 1200 mPas at 25°C (MULTRANOL3901Bayer Corp .)

Production steps of organic isocyanates having carbodiimide and/or uretonimine groups:

Heat 10 kg of technical grade 4,4'-MDI (DESMODUR44M) with Hasson color index <15 APHA and 750 ppm of 3,5-di-tert-butyl-4-hydroxytoluene to 60°C under N ₂ /stirring, add 250 mg catalyst solution (2.5 ppm; 0.2 mmol). The reaction mixture was heated to about 95°C under _N2 /stirring for 240 minutes. The relevant terminator was added to terminate the carbodiimidation reaction, and stirring was continued for 1 hour. In the examples according to the present invention, methyl trifluoromethanesulfonate (TFMSME) or ethyl trifluoromethanesulfonate (TFMSEE) and optional isophthaloyl dichloride (IPDC) are used according to the amounts in the table. Trifluoromethylsilyl trifluoromethanesulfonic acid (TMST) is used in reference examples 1 and 2, trifluoromethanesulfonic acid (TFMSS) is used in reference example 3, and the respective usage amounts are as shown in the table . The results are summarized in the table below.

Production steps of prepolymers of organic isocyanates and polyols having carbodiimide and/or uretonimine groups:

To 500 g of each isocyanate prepared according to the above procedure was added 167 g of MULTRANOL 3901 at 50°C under _N2 /stirring and the mixture was maintained at 80°C under _N2 /stirring for a further 2 hours. Analysis of the prepolymer was performed the next day. In order to determine the stability of the prepolymer, an isothermal pressure test (12 hours/90° C.) was carried out. The results are summarized in the table below.

The Hasson color index is measured according to DIN/EN/ISO 6271-2 (draft, September 2002) without solvent, with water as reference, at a layer thickness of 5 cm. The measuring device used can be, for example, a Dr. Lange LICO300 photometer.

Reference examples 1 and 2 clearly show that increasing the TMST stop dose has a positive effect on stability, although this is detrimental to the color (Hasson). Reference Example 3 again demonstrates the less favorable effect of the terminator trifluoromethanesulfonic acid (TFMSS) on color. In the inventive examples, the stability was improved compared to Reference Example 1 while maintaining a better color index (Hasson).

Although the present invention has been described in detail above for the purpose of illustration, it should be understood that these detailed descriptions are only for this purpose, and those skilled in the art can make modifications to it without departing from the spirit and scope of the present invention , except as limited by the claims.

Claims (7)

1. A method for producing an organic isocyanate having a carbodiimide group and/or a uretonimine group, wherein one or more organic isocyanates with a Hazen color index≤100APHA are carried out with a catalyst of the cyclopentenylphosphine class Partial carbodiimidation and termination of the carbodiimidation reaction, the improvement comprising terminating the carbodiimidation reaction with an alkylating agent selected from the group consisting of CF ₃ -SO ₃ - Esters of trifluoromethanesulfonic acid for R ¹ , wherein R ¹ represents an aliphatic, cycloaliphatic or araliphatic group. 2. The method of claim 1, wherein the alkylating agent comprises an aliphatic ester of trifluoromethanesulfonic acid. 3. The method of claim 1, wherein the alkylating agent comprises methyl trifluoromethanesulfonate, ethyl trifluoromethanesulfonate, propyl trifluoromethanesulfonate, trifluoromethanesulfonate butyl triflate or amyl triflate. 4. The method according to claim 1, further comprising adding acid and/or acid chloride and/or sulfonate in the step of terminating the carbodiimidization reaction. 5. An organic isocyanate having a carbodiimide group and/or a uretonimine group prepared by the method according to any one of claims 1-4. 6. A process for the production of isocyanate blends, the improvement comprising the introduction of an organic isocyanate having carbodiimide groups and/or uretonimine groups as claimed in claim 5. 7. A process for the production of polyurethane or isocyanate-terminated prepolymers, the improvement comprising the introduction of an organic isocyanate having carbodiimide groups and/or uretonimine groups as claimed in claim 5.