CA2034622A1

CA2034622A1 - Trimerization catalysts, a process for their preparation and their use for the preparation of polyisocyanates containing isocyanurate groups

Info

Publication number: CA2034622A1
Application number: CA002034622A
Authority: CA
Inventors: Hans-Joachim Scholl
Original assignee: Bayer AG
Current assignee: Bayer AG
Priority date: 1990-02-23
Filing date: 1991-01-21
Publication date: 1991-08-24
Also published as: EP0443167A1; JPH04211673A; DE4005762A1

Abstract

TRIMERIZATION CATALYSTS, A PROCESS FOR THEIR
PREPARATION AND THEIR USE FOR THE PREPARATION OF
POLYISOCYANATES CONTAINING ISOCYANURATE GROUPS
ABSTRACT OF THE DISCLOSURE
The present invention relates to trimerization catalysts which are suitable for heterogeneous catalysis and are based on quaternary ammonium or phosphonium fluorides adsorbed on porous carrier materials, characterized in that the carrier material is an adsorbent having a particle size (90%) of 0.1 to 10 mm, a pore volume of 0.4 to 1.4 ml/g, an average pore diameter of 7 to 50 nm and a specific surface area (BET) of 100 to 700 m2/g.
The present invention also relates to a process for the preparation of these catalysts by stirring together an alkali metal fluoride and a quaternary ammonium or phosphonium salt in the presence of an alcoholic solvent, removing any precipitate formed by filtration and adsorbing the resulting homogeneous catalyst solution onto the previously described carrier material, optionally after further dilution of the solution with an alkaline solvent.
Finally, the present invention relates to the use of the catalysts for the preparation of polyisocyanates containing isocyanurate groups by trimerizing at least a portion of the isocyanate groups of organic diisocyanates.

Description

;~034~2Z
Mo3529 LeA 27,528 TRIMERIZATION CATALYSTS, A PROCESS FOR THEIR
PREPARA~ION AND THEIR USE FOR ~HE PREPARATIOM OF
POLYISOCYANA~ES CONTAINING ISOCYANURATE 6ROUPS
BACKGROUND OF THE INVNTION
Field of the Invention The present invention relates to new trimerization catalysts for organi~ isocyanates, which catalysts are suitable for heterogeneous catalysis, in particular as solid bed catalysts, to a process for their preparation and to their use for the preparaticn of polyisocyanates containing isocyanurate groups.
Description of_the Prior Art Catalysts for the trimerization of organic isocyanates are known (J.H. Saunders and K.C. Frisch, Polyurethanes, Chemistry and Technology, pages 94 et seq. (1962)). Strong organic bases are suitable as catalysts for trimerization, e.g., the metal salts of carboxylic acids which are alkaline in reaction, metal alcoholates, metal phenolates, alkali metal carbonates, tertiary amines, tertiary phosphines and the "onium" compounds of nitrogen and phosphorus and the basic heterocyclic compounds of these elements.
These catalysts are generally for use in a homogeneous phase, are often required to be added in considerable quantities to the diisocyanates used as starting materials and must subsequently be removed from the end products of the process.
Processes are known (e.g. DE-OS 3,814,167 and DE-OS
3,827,595) in which quaternary ammonium or phosphonium fluorides are used as trimerization catalysts. These catalysts remain in the resulting product (after they have been "neutralized" with a catalyst poison to terminate the trimerization reaction) without causing cloudiness in the isocyanurate polyisocyanates obtained. However, the presence of these "neutralized" trimerization catalysts in the product 35376TwRl056 . .. . , . ., -- . ~.
.
. .
:
-. - - : ,: , . : , . - ~ . . .
- :. . - -. .
.: . ; . .
:-, . :

;~U34622 is a disadvantage since they constitute a foreign body which causes cloudiness during prolonged storage of the initially clear products.
It was therefore an object of the present invention to provide new trimerization catalysts for organic isocyanates, which catalysts are suitable for heterogeneous catalysis, in particular as solid bed catalysts, so that isocyanurate group-containing polyisocyanates prepared in the presence of these catalysts would be completely free from trimerization catalysts or secondary products of these catalysts and would not have the disadvantages mentioned above.
This object may be achieved in accordance with the present invention by using the trimerization catalysts described hereinafter. The new catalysts are based on the quaternary ammonium or phosphonium fluorides disclosed in the above publications, but are adsorbed on specific, selected carrier materials.
Although these publications disclose that the quaternary ammonium and phosphonium fluorides described therein may be adsorbed on carrier materials, the carrier materials specifically described in the examples of these publications are fundamentally different from the carrier materials used according to the present invention, are unsuitable for achieving the objectives stated above and, in particular, are unsuitable for solid bed catalysis.
SUMMARY OF THE INYENTION
The present invention relates to trimerization catalysts which are suitable for heterogeneous catalysis and are based on ~uaternary ammonium or phosphonium fluorides adsorbed on porous carrier materials, characterized in that the carrier material is an adsorbent having a particle size (90%) of 0.1 to 10 mm, a pore volume of 0.4 to 1.4 ml/g, an average pore diameter of 7 to 50 nm and a specific surface area (BET) of 100 to 700 m2/g.
The present invention also relates to a process for the preparation of these catalysts by stirring together an alkali Mo3529 , 3 ;~034622 metal fluoride and a quaternary anuTonium or phosphon;um salt in the presence of an alcoholic solvent, removing any precipitate formed by filtration and adsorbing the resulting homogeneous catalyst solution onto the previously described carrier 5 material, optionally after fùrther dilution of the solution wi th an al kal i ne sol vent .
Finally, the present invention relates to the use of the catalysts for the preparation of polyisocyanates containing isocyanurate groups by trimerizing at least a portion of the 10 isocyanate groups of organic diisocyanates.
DETAILED DESCRIPTION OF THE INVENTION
The carrier materials which are an essential feature of the present invention are organic or inorganic, porous, spherical adsorbent particles having the characteristics 15 previously described. The adsorbents used as carrier materials preferably have a particle size (90%J of 0.2 to 5 mm, a pore volume of 0.6 to 1.2 ml/g, an average pore diameter of 9 to 30 nm and a specific surface area of 110 to 600 m2/g.
Suitable carrier materials include the commercially 20 available spherical carrier materials which conform to these specifications and are based on silicon dioxide as supplied by Grace GmbH, D 6520 Worms, under the name of "GRACE Bead Type Silica Catalyst Supports C 10, C lS and C 30" and the spherical adsorber materials conforming to the above specifications and 25 based on polymeric divinyl benzene as supplied by Bayer AG, Leverkusen under the name of -LEWATIT VP OC 1062. Because of their spherical shape the absorbent particles differ essentially from amorphous matenals such æ
silica gel materials as, for example. "}~iese]gel 60" of E.Merck, Darrnstadt, Germa~y.
A~uTonium or phosphonium fluorides suitable for the preparation of the catalysts according to the invention include compounds corresponding to the formula _ _ ~

Rl Z - R3 F

Mo3529 . ~
. .~
. , .. :- . - . .
~ - .

Z()34~X2 wherein z represents nitrogen or phosphorus, Rl, R2, R3 and R4 may be the same or different and represent alkyl groups having 1 to 18, preferably 1 to 10 and more preferably 1 to 4 carbon atoms, provided that one of the groups may be an araliphatic group having 7 to 15 carbon atoms; the sum of the number of carbon atoms in the four groups is preferably 10 to 40; and when Z represents nitrogen, the groups Rl and R2 together with the nitrogen atom and optionally at the same time the groups R3 and R4 together with the nitrogen atom may form rings, preferably six membered rings, optionally containing additional hetero atoms.
The preferred fluorides include ammonium compounds corresponding to the above formula wherein z represents nitrogen, Rl, R2 and R3 may be the same or different and represent alkyl groups having I to 18, preferably 1 to 4 carbon atoms, more preferably methyl groups, and R4 represents a benzyl group.
Suitable fluorides include tetramethyl ammonium fluoride, tetraethyl ammonium fluoride, tetra-n-propyl ammonium fluoride, tetra-n-butyl ammonium fluoride, N-methyl-N,N,N-trialkyl ammonium fluorides containing C8-C10 alkyl groups, N,N,N-~rimethyl-N-cyclohexyl ammonium fluoride, N,N,N-trimethyl-N-benzyl ammonium fluoride, N,N,N-triethyl-N-benzyl ammonium fluoride, N,N,N-trimethyl-N-phenyl ammonium fluoride, N,N,N-trimethyl-N-stearyl ammonium fluoride, N,N'-dimethyl-triethylene diamine difluoride, N-methyltriethylene diamine monofluoride and mixtures thereof.
N-methyl-N,N,N-trialkyl ammonium fluorides containing C8-C1O alkyl groups, N,N,N7N-tetra-n-butyl ammonium fluoride and N,N,N-trimethyl-N-benzyl ammonium fluoride are especially preferred.

Mo3529 . ... . . .

20;~622 Suitable phosphonium fluorides, which are generally less preferred than the ammonium fluorides, include the corresponding phosphonium compounds, i.e., compounds corresponding to the above formula but wherein the central nitrogen atom is replaced by a phosphorus atom and the groups Rl to R4 having the meanings previously set forth. Examples include tetramethyl phosphonium fluoride, tetraethyl phosphonium fluoride and tetra-n-butyl phosphonium fluoride.
The fluorides used for the process may be prepared by the reacting a) alkali metal fluorides, preferably sod;um or potassium fluoride, more preferably potassium fluoride, with b) quaternary ammonium or phosphonium salts of any acid except for hydrofluoric acid, preferably strong mineral acids, more preferably hydrochloric or hydrobromic acid, the reaction being preferably carried out in an alcoholic `!
reaction medium.
Quaternary ammonium and phosphonium salts suitable for the reaction include, for example, those corresponding to the following formula L ~ ]

wherein Z, Rl, R2, R3 and R4 have the meanings or preferred meanings previously set forth and A( ) represents the anion of a strong mineral acid, except for hydrofluoric acid, preferably a chloride or bromide ion.
Typical examples of suitable starting materials bJ include the quaternary ammonium chlorides and bromides corresponding to Mo3529 . ~ .. . . . .
'' : . ., .. ,.. ,.. ~.
. , : .
' ' ~3~622 the quaternary fluorides pr~viously described as examples as well as phosphonium salts corresponding to these ammonium salts; the phosphonium salts are less preferred.
The quaternary ammonium or phosphonium chlorides may be prepared by dissolving or suspending the alkali metal fluoride a) in alcohols which preferdbly boil at temperatures below 120-C at normal pressure, such as methanol or ethanol, and then adding a preferably equimolar quantity of ammonium or phosphon~um salt b) with stirring, optionally in alcoholic solution. The quantities of a) and b) may be less than or greater than equivalent, for example by up to 50 mole percent in each case. The temperature and the stirring time are not critical. The process is generally carried out in a lO to 30%
by weight solution with stirring for 20 to 60 minutes. The resulting solution is then filtered to remove any precipitates formed.
The catalysts according to the invention may be prepared from ammonium or phosphonium fluorides which may have been prepared by any desired method. These fluorides are generally adsorbed on the carrier material in the form of alcoholic solutions (e.g., in methanol or ethanol). This adsorption is preferably carried out by the process according to the invention, i.e., the alcoholic solutions prepared as described above from alkali metal fluorides and quaternary ammonium or phosphonium salts are used, optionally after dilution with a further quantity of alcohol. The quaternary ammonium or phosphonium fluorides are generally used as 5 to 20% by weight solutions for the process according to the invention.
The ~adsorption" of the alcoholic solution of quaternary ammonium or phosphonium fluorides on the carrier materials is carried out by intimate stirring, preferably at room temperature, followed by separation of the alcoholic solvent, for example under vacuum. ~hen this method of preparing the catalysts according to the invention is employed, any water previously adsorbed in the adsorbents is for the most part Mo3529 ~' ,' ' ,. : ' I

~034622 removed so that the risk of an isocyanate/water reaction is virtually eliminated when the catalysts are subsequently used for trimerizing isocyanates. The quantities of alcoholic fluoride solution and carrier material are generally calculated to result in catalysts having a fluoride content of 0.05 to 5 mmol of F-, preferably 0.1 to 2 mmol of F-, per g of carrier material.
~he trimerization catalysts obtained by this method are eminently suitable for heterogeneous catalys~s, i.e. in particular as solid bed catalysts for the catalytic preparation ' !
of polyisocyanates containing isocyanurate groups from monomeric organic diisocyanates, in particular those having aliphat~cally or cycloaliphatically bound isocyanate groups.
Preferred starting diisocyanates for the catalytic trimerization reaction include aliphatic and cycloaliphatic diisocyanates having a molecular weight above 139, more preferably from 140 to 250, e.g., tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), dodecamethylene diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3- and/or -1,4-diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (IPDI), perhydro-2,4- and/or -2,6-diisocyanato-toluene, perhydro-2,4'- and/or -4,4'-diisocayantodiphenyl-methane and mixtures of these diisocyanates.
1,6-diisocyantohexane (HDI~ is a particularly preferred starting diisocyanate.
The catalysts according to the invention may be used in several embodiments for the preparation of polyisocyanates containing isocyanurate groups. The trimerization catalysts according to the invention may be added to the starting diisocyanate which is to be trimerized and when the desired degree of trimerization has been reached, they may be removed from the reaction mixture by filtration. The trimerization catalysts according to the invention are also eminently suitable as solid bed catalysts. In this process the starting diisocyanates, which are to be subjected to partial Mo3529 ~ . .
: ~

. ~ .
... . ~ ~ . .

~ 03d~62Z

trimerization, are passed through, for example, a reaction column filled with catalyst and heated to the reaction temperature.
~hen one of these embodiments according to the invention is used, the quantity of catalyst put into the process depends upon the degree of pur~ty of the organic starting diisocyanate.
The quantity of catalyst required may therefore most simply be determined by a preliminary test. ~hen the heterogeneous catalyst is added to the starting diisocyanate which is to be trimerized, the quantity of catalyst generally corresponds to 0.05 to 1 mmol of F /mole of starting diisocyanate; however, larger quantities may also be used since the reaction may be stopped at any time by removal of the catalyst by filtration.
It is in many cases advisable to assist the catalytic action of the catalysts according to the invention by means of a small quantity of co-catalytic urethane groups. Such co-catalysis is achieved, for example, by the addition of a small quantity of an alcohol (for example, from 0.01 to 1% by weight, based on the weight of the starting diisocyanate). The 20 alcohols added immediately react with the starting diisocyanate to form urethane groups. Methanol, ethanol, ethylene glycol and 2-ethylhexane-1,3-diol are examples of suitable alcohols for preparing the co-catalysts. The alcohols may be added together with or before the catalysts according to the present 25 i nvention.
According to a preferred embodiment for the preparation of isocyanurate polyisocyanates in the presence of the catalysts according to the invention, acid impurities present in the starting diisocyanate, which would prevent spontaneous trimerization and would eventually inactivate the catalysts according to the invention, are first "neutralized" by the addition of a small quantity of a component which is alkaline in reaction so that the trimerization reaction will take place spontaneously when the catalyst is added to the starting diisocyanate and will proceed smoothly under the usual reaction Mo3529 ''. ' . --~03~i2Z
g conditions. The quantity of such ~neutralizing additives~ can easily be determined by a preliminary test. The ~neutralizing agents~ used may advantageously be the solutions of quaternary ammonium or phosphonium fluorides which are also adsorbed on S the catalysts according to the invention, so that no additional foreign substances are added to the reaction mixture.
~he trimerization reaction preferably takes place in an inert gas atmosphere and is preferably carried out solvent free at temperatures of 0 to 100-C, in particular 20 to 80-C. The trimerization reaction may also be carried out ~n the presence of inert solvents, e.g., hydrocarbons such as toluene or xylene and esters such as butyl acetate.
The trimerization reaction is preferably carried out within the above mentioned temperature ranges until a degree of lS trimerization of 5 to 40%, preferably 10 to 3~/~, has been achieved. By "degree of trimerization" is meant the percentage of isocyanate groups in the starting diisocyanate which are converted into isocyanurate groups. The degree of trimerization may be monitored during the trimerization reaction, for example, by continuous determination of the refractive index or the isocyanate content of the reaction mixture. The heterogeneously catalyzed trimerization reaction is terminated, as already indicated, by removal of the heterogeneous catalyst.
~he resulting polyisocyanates containing isocyanurate groups may, if desired, be stabilized by the addition of small quantities of additives which are acid in reaction. These additives counteract the above mentioned spontaneous readiness of trimerization which was caused by the neutralization of the acid impurities. For this purpose, it is quite sufficient to add the acidic substances in quantities from p.01 mmol to less than 0.1 mmol per mole of isocyanate groups. The stabilizers include any organic acids or acid chlorides, e.g, sulphonic acids such as benzene or toluene sulphonic acid, or their chlorides; and acid esters of phosphorous acid or of phosphoric Mo3529 . .

.:

..

~03~622 -lo-acid such as dibutyl phosphite, dibutyl phosphate or di-(2-ethylhexyl)-phosphate.
The partially trimerized polyisocyanates may be freed by conventional methods from volatile constituents such as excess starting diisocyanate and any auxiliary solvents used. High quality lacquer polyisocyanates containing isocyanurate groups and having aliphatically and/or cycloaliphatically bound isocyanate groups may thus be obtained substantially free from monomers. These lacquer polyisocyanates may be used for the production of high quality po1yurethane coatings, in particular two component polyurethane coatings, optionally in a blocked form with blocking agents for isocyanate groups. These polyisocyanates are reacted with compounds having at least two isocyanate-reactive groups, preferably hydroxyl groups.
In the following examples, all parts and percentages are by weight unless otherwise indicated.
EXAMPLES
Startinq Materials Ouaternarv ammonium salt I
20 . A commercial quaternary ammonium chloride substantially consisting of N-methyl-N,N,N-trialkyl ammonium chloride containing C8-C10 alkyl groups (Aliquat 336 of Fluka GmbH, D
7910 Neu-Ulm).
Adsorbent I:
A commercial, spherical catalyst support based on silicon dioxide and having a particle size (90%) of about 2 to 3 mm, a pore volume of 1.05 ml/g, a pore diameter of 15 nm and a specific surface area of about 185 m /9 (GRACE Bead Type Silica Catalyst Support C 15, manufacturer: GRACE GmbH, D 6520, ~orms).
Adsorbent II:
A commercial, spherical catalyst support based on silicon dioxide and having a particle size (90%) of about 2 to 3 mm, a pore volume of 1.05 ml/g, apore diameterof30nm andaspecific Mo3529 .
. .

- - ~ ~. .

X0;~6Z~
"
surface area of about 110 m2/9 (GRACE Bead Type Silica Catalyst Support C 30).
Adsorbent III:
A commercial, spherical catalyst support based on silicon dioxide and having a particle size (90%) of about 2 to 3 mm, a pore volume of 1.05 ml/g, a porevo1umeof1.05 mVg~aporedi~ne~rof10 nm and a specific surface area of about 280 m2/g (GRACE Bead Type Silica Catalyst Support C 10).
Adsorbent IV:
A commercial, spherical catalyst support based on a divinyl benzene polymer having a particle size (90%) of 0.2 to 0.8 mm, a pore volume of about 0.6to O.65 m~g,apore diameter of 11 nm and a specific surface area of about 500 to 600 m /9 (LEWATIT VP OC 1062 of ~ayer AG, Leverkusen).
Example 1 ~Preparation of a heterogeneous catalyst) A solution of 80 9 of quaternary ammonium salt I in 100 9 of ethanol was added to 11.5 9 of potassium fluoride in 200 9 of ethanol at room temperature with stirring. The insoluble constituents were filtered off after 60 minutes. 600 9 of 98%
ethanol (about 2% water) were then added to the filtrate and the solution was stirred together with 600 9 of adsorbent I.
After 60 minutes stirring, the low boiling constituents were removed under vacuum at 50-C. A free flowing heterogeneous catalyst according to the invention having a fluoride content of 0.21 mmol/g was obtained.
Example 2 (Preparation of a heterogeneous catalyst) Example 1 was repeated except that 600 9 of adsorbent II
were used instead of adsorbent I. A free flowing heterogeneous catalyst according to the invention was again obtained, this time with a fluoride ion content of 0.21 mmol/g.
ExamDle 3 (Preparation of a heterogeneous catalyst) Example 1 was repeated except that 360 9 of adsorbent III
were used instead of the 600 9 of adsorbent I used in Example 1. A free flowing heterogeneous catalyst according to Mo3529 -, : . ... -:
'- .:. .
.

;~0~3~6 X 2 the invention having a fluoride content of 0.37 mmol/g was obtained.
ExamDle 4 (Preparation of a heterogeneous catalyst) A solution of 40 9 of quaternary ammonium salt I in 100 9 of ethanol was added to 5.8 9 of potassium fluoride in 100 9 of ethanol at room temperature with stirring. The insoluble constituents were filtered off after 60 minutes. 500 9 of ethanol were then added.
600 9 of adsorbent IV were suspended in 600 9 of ethanol.
The mixture was filtered under strong suction and the residue was stirred together with the previously described ethanolic solution. After removal of the low boiling constituents under vacuum at 50~C, a free flowing heterogeneous catalyst according to the invention having a fluoride content of 0.32 mmol/g was obtained.
ExamDle 5 (Use according to the invention) a) A solution of 16 9 of quaternary ammonium salt I in 60 9 of ethanol was added to 2.3 9 of potassium fluoride in 50 g of ethanol at room temperature with stirring. The insoluble constituents were filtered off after 60 minutes.
150 9 of 2-ethylhexane-1,3-diol were added to the filtrate and the ethanol was removed under vacuum. A solution of a quaternary ammonium fluoride in ethylhexane-1,3-diol having a fluoride content of 0.21 mmol/g was obtained.
2~ This solution may be used for ~neutralizing" acid impurities in the starting diisocyanate.
b) The solution described under 5a) was diluted to a fluoride content of 0.1 mmol/g by the addition of a further quantity of 2-ethylhexane-1,3-diol.
c) 2 9 of the solution described under b) were added to 3360 9 (20 molesJ of 1,6-diisocyanatohexane (HDI) in a nitrogen atmosphere with stirring. The mixture was then heated to 50-C and 15 9 of the catalyst described in Example 1 were added. The reaction mixture was then stirred at 62 to 64-C and the progress of the reaction was continuously Mo3529 :

- . .':.. ~ .
.
"
.

~0~46ZZ

monitored by the increasing refractive index. The reaction began about 10 minutes after the addition of the heterogeneous catalyst. A refractive index (23-C) of 1.4660 (initial value: 1.4522), corresponding to an isocyanate value of 42%, was obtained after 7 hours at 62 to 64-C. The catalyst was filtered off and the filtrate was stabilized by the addition of 0.2 9 of dibùtyl phosphate. The product was subsequently freed from excess HDI to a content of 0.1% by thin layer distillation at 120-C/0.1 mbar. A clear, colorless polyisocyanate containing isocyanurate groups and having an isocyanate content of 22.7% and a viscosity (23-C) of 1700 mPa.s was obtained. The yield, based on the HDI used as starting material, was 28.6%.
Example 6 (Use according to the invention) Example 5c) was repeated. ~hen a refractive index (23'C) of 1.4622 was obtained, which corresponded to an isocyanate content of 45% (5 hours at 63-65-C), the product was worked up as in Example 5.
Yield: 21.3%
NC0 content: 23.1%
Viscosity (23-C): 1200 mPa.s.
Example 7 (Use according to the invention) Example 5c) was repeated using 2 9 of the quaternary ammonium fluoride solution described in Example 5a) instead of the 2 9 of solution described in Example 5b). ~hen the refractive index was 1.4706 (23-C), which was reached after a reaction time of 8 hours at 63 to 64-C, the product was worked up as in Example 5c).
Yield: 37%
NC0 content: 22.3%
Viscosity (23-C): 3000 mPa.s.
Example 8 (Use according to the invention) 2 g of the solution described in Example 5b) were added to 3360 9 (20 molesJ of HDI with stirring under a nitrogen Mo3529 ::. ~ . . .
: . - .: , , . ~- ' .

- . .

;~03~6Z2 atmosphere. The solution was heated to 50-C, 15 9 of the heterogeneous catalyst described in Example 2 were added and the procedure described in Example 5c) was carried out. A
refractive index (23-C) of 1.4651 was reached after 9 hours.
After the product had been worked up as in Example 5c), a polyisocyanate containing isocyanurate groups and having the following data was obtained:
Yield: 29.1%
NC0 content: 22.8~o Viscosity (23-C): 1900 mPa.s.
ExamDle 9 2 9 of 2-ethylhexane-1,3-dio1 were added to 3,360 9 (20 mol) of HDI with stirring under a nitrogen atmosphere and the mixture was then heated to 60-C. After the addition of 15 9 of the heterogeneous catalyst described in Example 3, the reaction mixture was heated to 60-62-C for 7 hours. At the end of this time, the refractive index of the reaction mixture (23-C) was 1.4638. After the product had been worked up as in Example 5c), a polyisocyanate containing isocyanurate groups having the following data was obtained:
Yield: 24.1%
NC0 content: 22.1%
30 Viscosity (23-C): 1600 mPa.s.
Example 10 1 9 of the solution described in Example 5b) was added to 1680 9 (lO moles) of HDI with stirring in a nitrogen atmosphere. The reaction mixture was heated to 60-C, lO g of the heterogeneous catalyst of Example 4 were added and the mixture was stirred at 61 to 63-C for 6-5 hours. When a refractive index (23-C) of 1.4602 was reached, the catalyst was filtered off and the filtrate was stabilized with 0.1 9 of dibutyl phosphate and then worked up as ~n Example 5c). A
polyisocyanate containing isocyanurate groups and having the following data was obtained:

Mo3529 .

:

.
.
: , ~03~6Z2 Yield: 17.3%
NCO content: 23.7 Yiscosity (23-C): 1000 mPa.s.
Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variat;ons can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.

Mo3529 :~ . . . ,, ~ .
: , , . . .: : ' - , , ' . ~ . - . : ' ~ :

: .............. .. ~.................. .
., .~ - . .

Claims

1. A trimerization catalyst which is suitable for the heterogeneous catalysis of an organic isocyanate and comprises a quaternary ammonium or phosphonium fluoride adsorbed on an adsorbent, porous spherical support material having a particle size (90%) of 0.1 to 10 mm, a pore volume of 0.4 to 1.4 ml/g, an average pore diameter of 7 to 50 nm and a specific surface area (BET) of 100 to 700 m2/g.

2. The trimerization catalyst of Claim 1 wherein said quaternary ammonium or phosphonium fluoride corresponds to the formula wherein Z represents nitrogen or phosphorus and R1, R2, R3 and R4 may be the same or different and represent alkyl groups having 1 to 18, provided that one of the groups may be an araliphatic group having 7 to 15 carbon atoms; the sum of the number of carbon atoms in the four groups is 10 to 40; and when Z represents nitrogen, the groups R1 and R2 together with the nitrogen atom and optionally at the same time the groups R3 and R4 together with the nitrogen atom may form six membered rings, optionally containing additional hetero atoms.

3. A process for the preparation of a trimerization catalyst which comprises stirring an alkali metal fluoride and a quaternary ammonium or phosphonium salt together in the presence of an alcoholic solvent, filtering off the precipitate formed and adsorbing the resulting homogeneous catalyst solution, optionally diluted with a further quantity of alcoholic solvent, on an adsorbent porous spherical support material having a particle size (90%) of 0.1 to 10 mm, a pore volume of 0.4 to 1.4 ml/g, an average pore diameter of 7 to 50 nm and a specific surface area (BET) of 100 to 700 m2/g.

4. The process of Claim 3 wherein said quaternary ammonium or phosphonium salt corresponds to the formula wherein Z represents nitrogen or phosphorus, R1, R2, R3 and R4 may be the same or different and represent alkyl groups having 1 to 18, provided that one of the groups may be an araliphatic group having 7 to 15 carbon atoms; the sum of the number of carbon atoms in the four groups is 10 to 40; and when Z represents nitrogen, the groups R1 and R2 together with the nitrogen atom and optionally at the same time the groups R3 and R4 together with the nitrogen atom may form six membered rings, optionally containing additional hetero atoms and A- represents the anion of a strong mineral acid except for hydrofluoric acid.

5. In a process for the preparation of polyisocyanates containing isocyanurate groups by the catalytic trimerization of an organic diisocyanate, the improvement wherein the catalyst comprises the trimerization catalyst of Claim 1.

6. The process of Claim 5 wherein said organic diisocyanate contains aliphatically and/or cycloaliphatically bound isocyanate groups.