CA1334849C

CA1334849C - Process for the production of polyisocyanates which contain isocyanurate groups

Info

Publication number: CA1334849C
Application number: CA000607712A
Authority: CA
Inventors: William E. Slack
Original assignee: Miles Inc
Current assignee: Bayer Corp
Priority date: 1988-08-24
Filing date: 1989-08-08
Publication date: 1995-03-21
Anticipated expiration: 2012-03-21
Also published as: GB2222161A; GB8919150D0

Abstract

The present invention is directed to a process for the preparation of a polyisocyanate having an isocyanurate structure which comprises heating an organic diisocyanate to a temperature of from 100 to 275°C in the presence of a catalytic amount of a co-catalyst mixture comprising (i) a tertiary amine selected from the group consisting of 3-azabicyclo[3,2,2]nonane, 1,4-diazabicyclo[2,2,2]octane, 1-azabicyclo [2,2,2]octane, 1,8-diazabicyclo[5,4,0]undec-7-ene, C1 to C4 substituted homologues thereof and mixtures thereof, and (ii) a low molecular weight organic hydroxy group containing compound and/or a carbamic acid ester thereof, for a period of from about 0.1 minute to about 360 minutes.

Description

PROCESS FOR THE PRODUCTION OF POLYISOCYANATES
WHICH CONTAIN ISOCYANURATE GROUPS
BACKGROUND OF THE INVENTION
Numerous processes for the production of 5 isocyanurate-containing polyisocyanates are known. The use of tertiary amines to produce such polyisocyanates is also known. Typical of the tertiary amines and co-catalyst mixtures containing such amines described in the prior art are (i) co-catalyst mixtures of aryl 10 urethanes and tertiary amines such as N-methyl-morpholine, pyridine, dimethylaniline, diethylaniline, N-methyl-piperidine, and diethylcyclohexylamine (U.S. Patent No. 2,838,511); (ii) mixtures of mono-hydroxy compounds and tertiary amines such as dimethyl-15 aniline, hexahydrodimethylaniline, methyl morpholine,ethyl morpholine, permethylated diethylene triamine or triethylene tetramine, urethanes, diurethanes, N-diethyl piperazine and N,N'-dimethylethanolamine (U.S. Patent No. 2,952,665); (iii) mixtures of carbamic acid esters 20 and tertiary amines such as those described in U.S.
- Patent No. 2,952,665 (U.S. Patent No. 2,954,365);
(iv) mixtures of 1,4-diazabicyclo(2,2,2)-octane (DABCO) and alkylene oxides (U.S. Patent No. 3,168,483);
(v) mixtures of DABCO and aldehydes (U.S. Patent No.
25 3,179,626); (vi) mixtures of an organic epoxide and a strong base, such as DABCO (U.S. Patent Nos. 3,206,352 and 3,211,704); (vii) mixtures of specific pyrazines and phenol (U.S. Patent No. 3,759,916).
Additionally, the use of a mixture of furfuryl 30 alcohol and a tertiary amine such as DABCO to form a carbodiimide-isocyanurate foam is also known (U.S. Patent No. 3,894,972).

133~8~9 ~ DESCRIPTION OF THE INVENTION
The present invention is directed to a process for the preparation of a polyisocyanate having an isocyanurate structure which comprises heating an 5 organic diisocyanate to a temperature of from 100 to 275C in the presence of a catalytic amount of a co-catalyst mixture comprising (i) a tertiary amine selected from the group consisting of 3-azabicyclo[3,2,2]nonane, 1,4-diazabicyclo[2,2,2]octane, l-azabicyclo-[2,2,2]octane, 1,8-diazabicyclo[5,4,0]-undec-7-ene, Cl to C4 substituted homologues thereof and mixtures thereof, and (ii) a low molecular weight organic hydroxy group containing compound and/or a carbamic acid ester thereof, for a period of from about 0.1 minute to about 360 minutes.
Starting isocyanates suitable for use in the 20 present invention include substantially any aromatic aliphatic and cycloaliphatic diisocyanate. In general, such diisocyanates are represented by the formula R(NCO)2 in which R represents an organic group obtainable by removal of the isocyanate groups from an organic diiso-cyanate having a molecular weight of from about 112 to 1000, and preferably from about 140 to 400. Preferred 30 diisocyanates are those in which R represents a divalent aliphatic hydrocarbon group having from 4 to 18 carbon atoms, a divalent cycloaliphatic hydrocarbon group having from 5 to 15 carbon atoms, or a divalent arali-phatic hydrocarbon group having from 7 to 15 carbon 35 atoms. Examples of the organic diisocyanates which are ~ particularly suitable for the process include tetra-methylene diisocyanate; l,6-hexamethylene diisocyanate, dodecamethylene diisocyanate; cyclo-hexane-1,3- and -1,4-diisocyanate; 1-isocyanato-3-isocyanatomethyl-5 3,5,5,-trimethyl-cyclohexane (isophorone diisocyanate or IPDI); bis-(4-isocyanato-cyclohexyl)-methane; 1,3- and 1,4-bis-(isocyanato-methyl)cyclohexane; bis-(4-iso-cyanto-3-methyl-cyclohexyl)-methane; and ~
tetramethylxylene diisocyanate. Mixtures of 10 diisocyanates can, of course, be used. Preferred diisocyanates are l,6-hexamethylene diisocyanate, isophorone diisocyanate and bis(4-isocyanatocyclo-hexyl)-methane. In addition to the organic diiso-cyanates containing aliphatically- and/or cycloali-15 phatically-bound isocyanate groups previously set forth, it is also possible in accordance with the present invention to use aromatic diisocyanates wherein R
represents a difunctional aromatic hydrocarbon radical having from 6 to 15 carbon atoms. Suitable aromatic 20 diisocyanates include 2,4-diisocyanato toluene, 2,6-diisocyanato toluene, and mixtures of these isomers;
4,4'-diisocyanato diphenyl methane and its isomeric mixtures with 2,4'- and optionally 2,2'-diisocyanato diphenyl methane; and 1,5-diisocyanato naphthalene. In 25 addition it is possible according to the present invention to use mixtures of aromatic and aliphatic isocyanates.
The catalysts of the present invention are mixtures of specific amines and hydroxy compounds. The 30 amines useful herein are 3-azabicyclo[3,2,2] nonane, 1,4-diazabicyclo[2,2,2] octane (i.e. triethylene diamine or DABCO), l-azabicyclo[2,2,2] octane (i.e. quinucli-dine), 1,8-diazabicyclo[5,4,0]undec-7-ene, the Cl to C4 substituted homologues thereof (such as, e.g, 2-methyl-- ` 133~849 triethylene diamine, 2,3-dimethyltriethylene diamine, 2,5-diethyl- and 2,6-diisopropyltriethylene diamine), and mixtures thereof. The presently preferred tertiary amines are DABC0 and quinuclidine.
The hydroxy compounds useful in the present invention include substantially any relatively low molecular weight alcohol, diol, triol or the like, or a carbamic acid ester thereof. The hydroxy compound should generally have a molecular weight of less than 500 and preferably less than 250. It is preferred that such materials contain no more than 2 hydroxy groups per molecule. Specific useful hydroxy compounds include 1,5-pentanediol, n-butylalcohol; 1,3-butanediol;
1,3-propane diol; l-pentanol; and the like. Where a carbamic acid ester is used, the low molecular hydroxy compound is first reacted with an isocyanate and then the resultant carbamic acid ester (a urethane) is then used with the amine as the catalyst. The carbamic acid ester preparation is known and is described, e.g., in U.S.
Patent Nos. 2,838,511 and 2,954,365.
The amount of the amine and the hydroxyl compounds can vary over a wide range. The amine and hydroxyl compounds should generally be present in an amount relative to each other such that the equivalent ratio of amine fraction to hydroxyl fraction is from 0.01:1 to 10:1. However, both must be present for trimerization to take place. When carrying out the process of the invention the total amount of catalyst used is generally less than 1 percent by weight (based on the combined weight of the isocyanate and catalyst) and is preferably used in an amount of from about 0.1 to about 0.9 percent by weight and most preferably from about 0.3 to about 0.7 percent by weight.

133~8~9 ~ The reaction in accordance with the present invention is carried out at a temperature of from 100C
to 275C, preferably at a temperature of from 150C to 250C. The reaction is carried out for a period of from 5 about 0.1 minutes to about 360 minutes, preferably for from about 3 to about 180 minutes. (These times exclude the heatup and cooldown periods). In general, the higher the temperature, the shorter the reaction time.
It is also preferred that the reaction be carried out in 10 the absence of oxygen because the product thus formed is substantially improved with respect to color.
In the practice of the present invention, the diisocyanate is introduced into a reaction vessel and the catalyst is added thereto. Appropriate reaction 15 vessels are known in the art. It is preferred, however, that a hot tube plug flow reactor be used.
In order to prepare a trimer-modified isocyanate which is storage stable at 25C, the addition of an acidic stopper such as hydrogen chloride (one 20 equivalent of acidic compound per equivalent of tertiary amine group) may be required.
Several observations have been made when following the present invention:
1. There is an induction period which varies with the temperature used with no induction period being observed at reaction temperatures of 220C
or higher. In general, the higher the reaction temperature, the shorter the induction times.
2. All of the components must be present during the heating stage.

3. The catalyst package appears to have a memory.
Thus, if the reaction mixture is heated at a given temperature for a portion of the normal induction period, is then cooled to room temper-1~34849 ~ ature, and is later reheated to the given temperature, the trimerization reaction will begin when the total time totals the induction period.
The invention is further illustrated but is not intended to be limited by the following examples in which all parts and percentages are by weight unless otherwise specified.
EXAMPLES
10 Example 1 To a 250 ml 3-neck flask were added 100 parts of hexamethylene diisocyanate (HX), 0.4 parts of 1,5-pentane diol and 0.4 parts of 1,4-diazabicyclo[2,2,2]-octane (DABCO). The stirred reaction mixture while 15 being purged with dry nitrogen, was heated over a 4 minute period to 250C, held for 2 minutes, and then cooled to less than 50C over a 5 minute period. The resulting clear liquid had an isocyanate content of 28.0%. An IR scan of the reaction mixture gave strong 20 absorption at 1692 cm~l and 1466 cm~l, indicative of the presence of trimer.
Examples 2-11 Following the same procedure as was used in Example 1, the formulations listed in Table 1 were 25 heated at 250C for 2 minutes to afford the partially trimerized isocyanates.

Example Formulation (pbw) % NCO
2 100 HX 49.0 0.4 DABCO

3 100 HX 40.6 0.25 DABCO
0.6 n-butyl alcohol 13348~9 TABLE 1 (Cont) Example Formulation (pbw) % NCO
4 100 HX 40.9 0.25 DABCO
0.35 1,3-butanediol 100 HX 38.1 0.25 DABCO
0.35 1,3-propanediol 6 100 HX 40.6 0.25 DABCO
0.6 l-pentanol 7 100 methylenebis(phenyl-isocyanate) (MDI) 26.9 0.25 DABCO
0.35 1,3-propanediol 8 100 methylenebis(phenyl-isocyanate) (MDI) 24.8 0.25 DABCO
0.35 1,3-butanediol 20 9 100 HX 48.4 0.5 Quinuclidine 100 HX 37.9 0.1 Quinuclidine 0.6 n-butylalcohol 25 11 100 MDI 25.9 0.5 1,8-diazabicyclo[5,4,0]
- undec-7-ene 0.3 1,3-butanediol Example 12 To a 250 ml 3-neck flask were added 100 parts of hexamethylene diisocyanate, 0.35 parts of 1,3-butane-diol and 0.25 parts of 1,4-diazabicyclo[2,2,2]octane 5 (DABCO). The stirred reaction mixture was purged with dry nitrogen and heated over a 5 minute period to 140C.
After 3.5 hours at 140C, the reaction mixture had a % NCO of 48.7. A slight exotherm was observed to begin after an additional 0.25 hours at 140C (total induction 10 period of 3.75 hours). The reaction was maintained at 140C, with slight cooling, for 5 minutes then quench cooled to 25C. The resulting clear almost colorless liquid (APHA 35) had a 40.0% NCO content. An IR scan of the mixture gave strong absorptions at 1692 cml and 15 1466 cm 1, indicative of trimer.
Examples 13-18 Following the same procedure and formulations as were used in Example 12, the induction period at various temperatures was determined. The results are 20 listed in Table 2.
Table 2 Reaction Induction Example TemperatureCTime (min) % NCO
13 150 95 38.2 25 14 160 55 30.2 170 26 33.8 16 180 15 31.7 17 190 8 31.8 18 200 4 34.0 30 Examples 19-32 Following the same procedure as was used in Example 12, the induction period was determined at various temperatures for the formulations listed in Table 3.

133~849 Reac- Induc- Reac-Formu- tion tion tion Exam- lation Temp. Period Time 5 ~ (pbw) C (Min) (Min) % NCO

19 100 HX 150 103 8 31.4 0.25 DABCO
0.6 n-butyl alcohol 100 HX 150 198 5 40.5 0.1 Quinuclidine 0.2 n-butyl alcohol 21 100 HX 150 115 5 40.4 0.25 DABCO
0.6 l-pentanol 22 100 HX 160 184 5 37.9 0.1 Quinuclidine 0.2 n-butyl alcohol 23 100 MDI 150 28 3 24.1 0.1 Quinuclidine 0.6 n-butyl alcohol 24 100 MDI 170 13 1.5 24.5 0.1 Quinuclidine 0.6 n-butyl alcohol 100 MDI 140 40 4.5 25.3 0.2 DABCO
0.6 n-butyl alcohol TABLE 3 (Cont) Reac- Induc- Reac-Formu- tion tion tion Exam- lation Temp. Period Time 5 ~ (pbw) C (Min) (Min) % NCO

26 100 MDI 150 26 1 30.1 0.2 DABCO
0.6 n-butyl alcohol 10 27 100 MDI 160 15 1 28.5 0.2 DABCO
0.6 n-butyl alcohol 28 100 MDI 170 9 2 23.7 0.2 DABCO
0.6 n-butyl alcohol 29 100 HX 150 100 5 45.5 0.2 DABCO
0.6 n-butyl alcohol 100 HX 170 32 5 45.6 0.2 DABCO
0.6 n-butyl alcohol 31 100 HX 150 93 5 44.5 0.4 DABCO
0.6 n-butyl alcohol 32 100 HX 170 30 5 44.7 0.4 DABCO
0.6 n-butyl alcohol 1~34849 ~ Example 33 To a 250 ml 3-neck flask were added 100 parts of hexamethylene diisocyanate, 0.6 parts l-butanol, and 0.2 parts Quinuclidine. The stirred reaction mixture, 5 while being purged with dry nitrogen, was heated over a 5 minute period to 160C. After 70 minutes at 160C the reaction mixture had an NCO content of 48.0%. A slight exotherm was observed to start after an additional 5 minutes at 160C. The reaction was maintained at 10 160C, with slight cooling and after 2 minutes had an NCO content of 34.0% and after an additional 5 minutes the reaction mixture had set up into a solid mass.
The above reaction was repeated twice except in the first repeat, after 5 minutes of trimerization at 15 160C, 0.3 parts of benzoyl chloride was added (% NCO at the time was 28.1%) and the reaction mixture was heated at 160C for an additional 20 minutes with no change in the % NCO. The second repeat used a 2.7 parts of a 2.8%
HCl/HX solution as the stopper with the same result.
20 Example 34 To a 500 ml 3-neck flask were added 200 parts of hexamethylene diisocyanate, 0.7 parts of 1,3-butane-diol and 0.5 parts DABCO. The stirred reaction mixture, while being purged with dry nitrogen, was heated over a 25 5 minute period to 150C. After 85 minutes, a 100 part sample was withdrawn from the reaction mixture and quench cooled and stored at 25C under dry nitrogen.
The remainder of the reaction mixture was maintained at 150C and after an additional 20 minutes a slight 30 exotherm was observed to start (total induction period of 105 minutes). The reaction mixture was maintained at 150C, with slight cooling, for an additional 5 minutes, then quench cooled to 25C affording a 30.3% NCO
content.

The above 100 parts sample which was withdrawn after 85 minutes at 150C was found to have an NCO
content of 48.0%. After three days at 25C it had an NCO of 47.8%. At this time it was again heated to 150C
5 and after 26 minutes a slight exotherm was observed to start (total induction period of 111 minutes). The reaction mixture was maintained at 150C, with slight cooling, for an additional 5 minutes then quench cooled to 25C affording a 30.3% NCO.
10 Example 35 To a 250 ml 3-neck flask were added 50.2 parts of hexamethylene diisocyanate, 49.8 parts of 4,4'-diiso-cyanate diphenylmethane, 0.25 parts DABCO and 0.35 parts of 1,3-butanediol. The stirred reaction mixture was 15 purged with dry nitrogen and heated over a 4.5 minute period to 250C. After 10 minutes at 250C the reaction mixture was cooled over a 3 minute period to 50C. The resulting clear yellow liquid had a 28.1% NCO content.
Upon HPLC analysis, the polymeric trimer product was 20 found to have an aliphatic component of about 38%.
Example 36 To a 250 ml 3-neck flask were added 67.5 parts of hexamethylene diisocyanate, 32.5 parts of 2,4-toluene diisocyanate, 0.25 parts of DABCO and 0.35 parts of 25 1,3-butanediol. The stirred reaction mixture was purged with dry nitrogen and heated over a 4.5 minute period to 248C. After 2 minutes at 248C the reaction mixture was cooled over a 2 minute period to 50C. The resulting clear yellow liquid had a 36.8% NCO content.
30 Upon HPLC analysis, the polymeric trimer product was found to have an aliphatic component of about 46%.

13~4819 ~ 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 variations can be made therein by 5 those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.

Claims

1. A process for the preparation of a polyisocyanate having an isocyanurate structure which comprises heating an organic diisocyanate to a tempera-ture of from 100 to 275°C in the presence of a catalytic amount of a co-catalyst mixture comprising (i) a tertiary amine selected from the group consisting of 3-azabicyclo[3,2,2]nonane, 1,4-diazabicyclo[2,2,2]octane, 1-azabicyclo

[2,2,2]octane, 1,8-diazabicyclo[5,4,0]undec-7-ene, C1 to C4 substituted homologues thereof and mixtures thereof, and (ii) a low molecular weight organic hydroxy group containing compound and/or a carbamic acid ester thereof, for a period of from about 0.1 minute to about 360 minutes.
2. The process of Claim 1 wherein said organic diisocyanate is selected from the group consisting of 1,6-hexamethylene diisocyanate, isophorone diisocyanate and bis(4-isocyanato cyclohexyl)methane.

3. The process of Claim 1 wherein said tertiary amine is 1,4-diazabicyclo[2,2,2]octane.

4. The process of Claim 1 wherein said tertiary amine is 1-azabicyclo[2,2,2]octane.

5. The process of Claim 1 wherein component (ii) is an organic hydroxy group containing compound having a molecular weight of less than 500.

6. The process of Claim 5 wherein the molecular weight of said hydroxy group containing compound is less than 250.

7. The process of Claim 5 wherein said hydroxy group containing compounds contain no more than two hydroxy groups.

8. The process of Claim 1 wherein the amount of component i) relative to the amount of component ii) is such that the equivalent ratio of amine function to hydroxy function is from 0.01:1 to 10:1.

9. The process of Claim 8 wherein said co-catalyst mixture is used in an amount of from about 0.1 to about 0.9 percent by weight based on the amount of organic diisocyanate.

10. The process of Claim 9 wherein said co-catalyst mixture is used in an amount of from about 0.3 to about 0.9 percent by weight.

11. The process of Claim 1 wherein said temperature is from 150°C to 250°C.

12. The process of Claim 1 wherein said time is from about 3 to about 180 minutes.