CA1133001A - Polyurethane catalysts - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Novel compounds of the formula:

wherein:
Q and Q', which may be the same or different, each represent a group of the formula

Description

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1~33V~

This invention relates to catalysts; more particularly, this invention relates to catalysts for the production of polyesters and polyurethanes.
Batch-to-batch variability is a serious problem encountered industrially in polyurethane production. A wide variety of compounds will catalyse or co-catalyse the isocyanate-alcohol reaction; in addition, trace contaminants in the reactants themselves, e.g.
polyesterification catalysts, can also be polyurethane catalysts and thus contribute to this variability. The effect of such contaminants can be minimised by the use of highly active catalysts but this itself gives rises to serious variability problems by causing the polyure- !
thane reaction to commence before the components are completely mixed.
These problems would be minimised if a highly active catalyst `
having a delayed-action effect could be developed~ However, such compounds so far developed with this property are organo-mercury compounds which are extremely expensive and present a severe toxicity hazard.
This invention seeks to provide catalysts having a delayed-action effect which can be produced more economically.
The present inventlon in one a~pelt prnYide~q compol1nd~q of t~ ormllla;
r~

3 Sn t Q - Sn t OOCQ~C00~4 Z

~' 3~0~
wherein:
Q and Q' which may be the same or different, each represent a group of the formula ~CH2~n or an arylene group, preferably a phenylene group, most preferably an ortho-phenylene group; Rl, R2, R3 and R4, which may be the same or different, each represent an unsubstituted al~yl group;
each n, independently representg zero or an integer from 1 to 10, prefera-bly from 1 to 6; and x represents zero or an integer less than 6, prefera-bly less than 4, especlally 1. As noted above, in the above formulae Rl, R2, R3 or R4 represent an unsubstituted alkyl group, for example a Cl to C6 alkyl group, preferably a Cl to C4 alkyl group. Generally, Rl and R2 will be identical and it is particularly preferred that they both represent butyl groups. Suitably, R3 and R4 will be identical. It is preferred that R3 and R4 each represent an ethyl or a butyl group.
It is believed that when x = 1, and possibly when x ~ 1, these compounds exist in an associated form. When x = 1 the structure may be a dimer of the formula:

1~330~1 , ¦ 2 4 R3oocQcooR2Rlsn / SnRlR~oocQlCOOR4 O ~

SnRlR200CQcOoR3 It is not known whether, at the low concentrations encountered in poly-urethane-forming reactions, these compounds are sssociated or not.
The above mentioned compounds of aspects of the invention are catalysts per se for the production of polyurethane. These compounds of aspects of the invention can also react with dihydroxyl compounds, for example glycols and polyetherglycols, under ester interchange conditions . . .

~ - 3 -to produce poly~eric tin-containing es ter~ having hydroxyl groups in the terminal positions. These latter compounds, too, are also found to be catalysts for polyurethane-production. Furthermore, such catalytic poly-meric tin-containing esters also react with isocyanates to produce tin-con-taining polyurethanes which are themselves catalysts for further polyure-thane production.
The first-mentioned class of compounts of aspects of the inven-tion (hereinafter referred to as monomeric or telomeric tin-containing di-esters) may be prepared in accordance with a process of another aspect of the invention, by reacting a compound of the empirical formula:

RlR2Sn with a dicarboxylic acid alkyl ester of the formula:
R300CQCOOH and/or R400CQ'COO~
wherein Rl, R2, R3, R4, Q and Q' are hereinabove defined.
By a variant thereof, the tin oxide is reacted with the acid alkyl ester in a stoichiometric ratio of 1:1 thereby providing a compound wherein x a 1~

: ~ - 4 -~1~330~

By another variant, the process is carried out in an anhydrous hydrocarbon solvent.
By yet another variant, the solvent is sodium-dried.
For example, dibutyl tin oxide may be reacted with adipic acid monoethyl ester of phthalic acid monobutyl ester. The reactants are suitabIy mixed in~the appropriate stoichiometric ratio and reaction is con-veniently carried out in an organic solvent, for example toluene or other hydrocarbon, preferably sodium-dried. The reaction products separate on cooling or after evaporation of the solvent.

. ~

11330~

The class of compound of an aspect of this invention is a catalysts for the production of polyurethanes, the polymeric species giving rise to very smooth rapid reactions. WheLe foam products are pro-duced from them, these are of very fine texture. In additlon to showing catalytic activity the compounds of this invention are non-volatile stabilisers for polyvinylchloride.
This invention in yet another aspect provides a p~lyurethane prepared using a polymeric tin-containing ester and/or tin-containing catalytlc polyurethane of the present invention and/or a catalyst of the formula:

X - Sn ~ - Sn ~ ~ Y
I \ ~
R2 \ R2 ~ ~L
wherein:
R1, R2 and x are herein above defined; and X and Y which may be the same or different, each represent a monoester of a dicarboxylic acid.

,~, il33~
G~l times measured for test-eube scale reactions of polyols with toluene diisocynate (TDI) and with dlphenylmethane diisocyanate (MDI) are given in Tables 1 and 2. The efficiency of the polymeric catalyfits can be seen for the case when such a catslygt was prepared as a master-batch $n the polyol so that the concentration of tin in the mixture would be roughly equivalent to that in similar experiments with the monomeric or telomeric tin-containing diesters: the effect on gel time can be seen in Table 2. Catalysts of this nature will be ~i33(~ .

particularly useful for systems where very short reaction times are required (e.g. short cycle reactions moulding) and where high catalyst concentrations may prove to be uneconomic or undesirable.
When reac~ion ratesare compared in tcrms of 1he respective gel times then it is clear that the monomeric or telomeric tin-containing diesters are a1so efficient catalysts and are indeed faster than conven+ional cat~ly~t~ e.g. Dl)TL. IlOWeVIn` when Ibsolute reaction rates are measuled for dilute s(>lutioll reactioJIs then it become~
apparent that the 1:~ mon<llleric tin ester gives a somewhat slower reaction th~n Dl3TL when equivalent concentrations (either mole %
or wt ~) oL catalyst are used (Table 3). Iiowever tl-is relationship r is reversed when the temperature is increased.
In this case the reaction under invest;gation was that of iso-propanol (0.01 mole) with phenyl isocynnate (0.01 mole) in dry 15 toluene (100 ml) at ambient temperature (22 - 2IJ C) and at an r elevated temperature of 45 C. Re.sidual i~ocyal1ate ill the reaction mixture was monitored during the reactiol1 by taking an aliquot (5 ml) of the mixtuJe and di~esting this in a mixtule of dry alld redistilled toluene (50 m1) and di-n-buty1amine (50 ml 0.2N so1ution in toluene).
This mixture was left to stand for 15 minutes and then residual amine was estimated by adding iso-propanol (225 m1) to the mixture and then titratinl a-lainst O.lN HCl using hromocressol green as indicated.

Examples of results for small scale reactions at 30 C

Catalyst type Wt. of catalyst (mg) Gel time (min.) 1:1 MTE 20 4 Tin-containing ( 40 60 polyester (Example 6) ~ 80 11 Tin-containing ( 40 24 polyurethane (Example 7) ( 80 14 ,_",~

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Summary of results for small scale reactions at 70C

Wt ~ MDl Wt. of polyether Wt. of catalyst Gel ~ine Catalyst type (g) (g) (mg) (min-sec) DBTL 1.48 5-92 0.11 15-00 DBTL 1.49 5.96 18-15 0.5:1 TTE 1.35 5.40 0.09 9-10 0.5:1 TTE 2.00 8.oo 15-00 1:1 MTE 1.48 5.92 0.13 13-10 1:1 MTE 2.06 8.24 15-30

2:1 MTE 1.24 4.96 7~3 2:1 MTE 1.4~ 5.76 0.12 8-30 2:1 MTE 1.96 7.84 10-00 MTE combined 1.81 7.24 2-00 with poly- 0.13 (Example 5) 1.83 7.32 2-30 11;~300~

Summary of results for solution reactions c"3 catalyst (0.1 mole %) C6H NC0 ~ ~ CIIOH
5Cl~3 ~ toluene (100 ml) 0.01 mole 0.01 mole Catalyst type Temperature % conversion 60 min.

m~ e (22 - 2l~C) DBTL amb;ent 5o 1:1 M'l`E ~5 C ~6 DBTL l~5 C 81 113;~00~

The increase in catalytic efficiency of the 1:1 MTE as the temperature increases can be utilised to provide a delayed action effect in larger scale bulk systems. This effect is demonstrated in Figure 1, in which curves showing the build-up in viscosity with time, for polyurethane elastomer formation, are presented. The results obtained with the 1:1 momomeric tin-containing diester (x = 1 in the generic formula) are represented by curves 1c and ld. These may not be obtained in the research laboratory if a small bulk, thermally uninsulated system is used since the initially slow exotherm would not be adequately conserved to raise the temperature sufficiently (typically 45 C) to give the catalyst the required activation after the delay period. Conversely, if too high an initial temperature (75 C, for example) is used the catalyst is immediately activated and no delay period is observed.
Referring now in more detail to Figure 1, there are disclosed four kinetic plots of viccosity (cps) (log scale), as a measure of the amount of polyurethane formed, versus reaction time (min.).
The reactants were polyether glycol and toluene diisocyanate initially maintained at 22 C. Curve (a) is a plot in which the catalyst is 64 ng (lng = 10 9g) of dibutyltin bis(ethyl adipate);
curve (c) in which the catalyst is 6~ ng of bis(ethyl adipatodibutyltin) oxide; and curve (d) in which the catalyst is 32 ng of bis(ethyl adipatodibutyltin) oxide. Curve (b) is a reference plot in which the cata~yst is 128 ng of dibutyltin laurate (DBTL).

The viscosities in each run were measured as follows.
Into a ~iOOml beaker was measured a 250g sample of previously dried poly(oxypropylene) glycol (PPG) of Md. Wt. 1000. The beaker and its content~ were then placed in an insulating block of polyurethane foam. This block measured 22cm x 2Zcm x lOcm and the beaker was placed in a central cut out of 7cm depth.
A dilute solution of the appropriate tin ester in toluene (typically 0.1g in 1 li,tre) was prepared and microlitre guantities were added to the PPG with a syringe. A Brookfield Viscometer (Model HBT) was fitted with spindle No. 1 and the spindle was immersed in the liquid upon the groove on the stem, care being taken to ensure that no air was trapped under the spindle. The viscometer was switched on at a spindle speed of 100 r.p.m.
Toluene diisocyanate (43.54g) was added to the contents of ~' the beaker and timing was commenced. The viscosity of the liquid was measured at one minute intervals throughout the reaction until gelling occurs.
In addition to the desirable delayed action effect noted above, it will be seen that the monomeric tin die~sters of an aspect of the invention are much more reactive than the conventional DBTL catalyst. As i,s genera1 with such systems the presence of a small amor~nt of cata]yst, typically 15 to 20 ng in the above system, was required in order to obtain any catalytic effect.

1133(~0~

sy~T~Esrs OF 2:1 MONOMERIC TIN-CONTAINING DI-ESTER
15g of dibutyltin oxide (0.06mole) and 21g of adipic acid monoethyl ester (0.12mole) were placed in a one litre flask and 750 ml of redistilled sodium-dried toluene were added. On heating to the boil a clear solution was formed and an azeotrope of toluene and water was distilled off as rapidly as possible. Distillation was continued until a volume of about 100ml of solution remained. This solution was placed in a 150ml flask and heated under vacuum (water vacuum pump) over ~5 minutes while the temperature rose to 130 C. The oil vacuum pump was then applied (pressure 1-2mmHg) and the remainder of the solvent was distilled off at 130 C. The reaction product was a clear, amber liquid.

SYNTHESIS OE 1:1 MONOMERIC TIN-CONTAINING DI-ESTER
15g of dibutyltin oxide (0.06mole) and 10.5g of adipic acid monoethyl ester (0.06mole) were placed in a one litre flask and 750ml of re-distilled sodium-dried toluene is added. On heating to the boil, a clear solution was formed and an azeotrope of toluene and water was distilled off. Distillation was continued until a volume of about 100ml of solution remained. This solution was placed in a 150ml flask and heated under vacuum (water vacuum pump) over l~5 minutes while the temperature rose to 130 C. The oil vacuum pump was then appl ied (pressure 1-2mm H~) and the remainder of the solvent was distilled off at 130 C. The reaction product was a clear, amber liquid.

1133S)01 SYNTHESIS OF 0.5:1 TELOMERIC TIN-CONTAINING DI-ESTER
15g of dibutyltin oxide (0.06mole) and 5.259 of adipic acid monoethyl ester (0.03mole) were placed in a one litre flask and 750ml toluene was added. On heating to the boil, a clear solution was formed and an a7eotrope of toluene and water was distilled off. Distillation was continued until a volume of about 100ml of solution remained. On coo]ing a fine white plecipitate of dibutyl tin oxide (0.98g) was forrned and was filtered off. The solution was placed in a 150ml flask and heated under vacuum (water vacuumpump) over 45 minutes while the temperature rose to 130 C. The oil vacuum pump was then~applied (pressure 1-2mm Hg) and the remainder of solvent was distilled off at 130 C. The reaction product was an amber glassy solid which softened at around 150 C
to a clear, amber liquid.
EVIDENCE FOR STRUCTURES OF MONOMERIC TIN-CONTAINING DI-ESTERS
2:1 Monomeric Tin-containing Diester (2:1 MTE) Infrared spectroscopy (Figure 2 of the accompanying drawings) showed the product to be substantially free of either of the two reactants. There was no evidence for the presence of stannoxane group. An absorption characteristic of carboxylate was observed at 6.22~m (1608 cm ).

1133(~

The presence of this absorption band and the fact that none of the reactant ester was distilled out during the reaction lead to the conclusion that the product is probably dibutyltin bis (ethyl adipate):

C2l{500C(CI{2)4C00-Sn-OOC(CH2)4COOC2H5 c4l~9 The results of micro-analysis support this assignment (Found:
C~ 50.0; H, 7.6; 0, 21.5/'o, C24H/l40gSn requires C~ 49-8;
H,7.6; 0, 22.1% ) 1:1 Monomeric Tin-Containing Diester (1:1 MTE) Infrared spectroscopy (Figure 2b of the accompanying drawings) showed the product to be substantially free of either of the two reactants; the spectrum was characterised by a strong absorption of 15.75~m (635 crn ) characteristic of Sn-0-Sn. A 300 MH
~H NMR spectrurn of the product (in CCll) has been obtained (Figure 3 of the accompanying drawings). The assignments shown in the figure are ~5 obtained by reference to the spectrum of adipic acid monoethyl ester:
the integrations are consistent with a 1:1 adduct of this ester and dibutyltin oxide. The spectral evidence is consistent with the reaction product being bis(ethyl adipatodibutyltin) oxide as are the results of micro-analysis (Found: C, 46.4; H, 7.7; 0, 17.7%; C32H6209Sn2 requires C, 46.l~; H, 7.5; 0, 17.4%).

1133~01 The presence of infrared absorption bands at 20.5~m (485 cm ) and around 6-6.5~m suggests that this stannoxane may be associated in some wayt possibly as a cyclic dimer.
The unassociated structure is pr-obably:
ClkH9 ~C4~19 C2H500C(Cll2)4 COO - Sn - O - Sn - OOC(CH2)4COOC2H5 0.5:1 Telomeric Tin-containing diester (0.5:1 TTE) Infrared spectroscopy (Figure 2c of the accompanying drawings) showed the product to be substantially free either of the two reactants; the spectrum was characterised by a strong absorption at around 1~ m characteri~tic of Sn-O-Sn.
In view of the reaction stoichiometry and the polymeric nature of dibutyltin oxide, a polystannoxane structure is suggested (x~ 1 in the generic formula). The results of micro-analysis are consistent with a structure for which the mean value of x is 3 (Fol~nd C, 43.5; H, 7.7; O, 13-5%; C48~g8011Sn4 requires C, 43.5; H, 7./l; o, 13.5%).

SYNTHESIS OF POLYMERIC TIN-coNTAINING ESTER
0.5g (0.33mmole, 1 meq) of dry poly(oxypropylene) triol of MW 1500 and 0.29g (0.50mmole, 1 meq) of 2:1 MTE were placed in a B24 test-tube equipped with a Drechse1hea~1and the mixture was heated for ~ hours using an oil bath at 180 C whilst nitrogen (oxygen-free grade) was passed through the inside of the test-tube.

il;~3001 The product was a viscous liquid which did not flow under its own weight and which had an infrared spectrum possessing only a very weak absorption characteristic of hydroxyl, but showing a strong absorption at 5.78 ~ m, 1730 cm ; characteristic of ester carboxyl.

SYNTHESIS OF POLYMERIC TIN-CONTAINING ESTER
A solution containing 1~1 (1.2mg, 2.1~mole) of 2:1 MTE
in 5ml dichloromethane was added to 70 ml (66g, 44mmole) of dry poly(oxypropylene) triol of MW 1500 and the mixture shaken until visually uniform. The dichloromethane was then removed from this mixture by evaporation under reduced pressure. The reaction mixture was then placed in a 150ml two-necked flask equipped with gas inlet and outlet tubes. The mixture was then heated for 2-3 hours using an oil bath at 175 C whilst nitrogen (oxygen-free grade) wa.s passed through the flask. The product obtained was a clear and colourless free-flowing liquid.

SYNTHESIS OF POLYMERIC TIN-CONTAINING ESTER
37g (20mmole) of poly(tetramethylene adipate) of MW 1830 and 10g (12 mmole) of 1:1 MTE were placed in a 100ml three-necked flask equipped with a thermometer, gas inlet tube and Leibig condenser. Some antibumping granules were added and the mixture was heated for 3-5 hours at 175 C whilst nitrogen (oxygen-free grade) was passed through the flask. The nitrogen flow was stoppeA and the ~8 .o flask was evacuated (rotary oil pump) and the mixture was heated under vacuum for a further 20 minutes. The hot reaction product, a clear viscous liquid, was poured into an aluminium tray to solidify.
EXA~IPLE 7 SY~'THESIS OF TI~-CONTAINING CATALYTIC POLYURETHANE
ln the three-necked flask of capacity 100 ml equipped with a stirrer, reflux condenser, gas inlet tube, thermometer and dropping funnel, 15 9 of the polymeric tin-containing diester was dissolved in 25 ml ethyl acetate at 60 - 70 C. Then temperature was lowered to 40 C and the suspension of 0.5 g diphenylmethane diisocyanate (~1DI) in 5 ml ethyl acetate was added dropwise over 3 minutes with continuous stirring of the reaction mixture. The dropping funnel was then washed with 2.5 ml ethyl acetate and this was also added to the reaction mixture. Immediately after the ~lDI has been added the temperature inside the flask increased to ~3 - ~5 C. After 15 minutes the reaction mixture was heated to 50C and this temperature was maintained over 45 minutes. Then the temperature was raised to 60 C and the reaction mixiure maintained at this temperature over 1 hour~ and finally taken up to the boiling point (approximately 78& ) and boiled ZO for over 1 hour. The reaction mixture (clear yellow liquid) was then evaporated at room temperature and waxy-white-yellowish product was obtained.
EX~1PLE 8 SYNT~ESIS 0~ PO~YU~ET~ANE ELASTO~ER AT 30 C
12.15 ~ (30 mmole, 61 meq.) of dry poly(oxy~ropylene) glycol of ~ 400 and a small amount of catalyst (typicaily 10 - 80 mg3 were 11~3~)0~

mixed in a B24 test-tube (N.B., when polymeric catalysts are used this mixture was heated up to 80 C and mixed until solution occurred and then cooled to room temperature before further reagents were added). 8.10 9 (2.7 mmole, o.1 meq.) of dry poly(oxypropylene) triol of MW 3000 and 5.0 ml (6.1 9, 70 meq.) of toluene diisocyanate (TDI) were added to the reaction mixture. The mixture was placed in a constant témperature bath at 30 C and was stirred for 1 minute.

Equivalent quantïties of poly(oxypropylene) triol (ca. 6 9) of MW 1500 and MDI (ca. 1.5 9) were mixed with a small amount of catalyst (ca. 0.1 mg) in a B24 test-tube. The test-tube was placed in a 70 C oil bath and the mixture was stirred for 1 minute.

SYNTIIESIS OF POLYURETHANE FOAM
The polyether and catalyst were pre-mixed as above. Water (0.5 9) and silicone oil (0.25 9) were added to a mixture of 12 9 of poly(oxy-propylene) triol of MW 3000 and 20 - 80 mg of catalyst 5 ml of TDI
were then added and the mixture was warmed to 30 C and stirred over 20 15 - 20 seconds.

SYNTHESIS OF 1:1 MONOMERIC TIN-CONTAINING DIESTER OF AN AROMATIC ACID
15 9 of dibutyltin oxide (o.o6 mole) and 13.3 g of phthalic acid monobutyl ester (o.o6 mole) were placedinaone litre flask and 750 ml 25 of re-distilled sodium-dried toluene is added. On heating to the boil, the solution began t~ clear and the azeotrope of toluene and water was 1133~0~

distilled off. Distillation was continued until a volume of about 100 ml of solution remained. This solution was placed in a 150 ml flask and heated under vacuum (water vacuum pump) over ~5 minutes while the temperature rose to 130 C. The oil vacuum pump was then applied (pressurel-2 mm Hg) and the remainder of the solvent was distilled off at 130 C. The reaction product was an amber liquid.
The infra-red spectrum was consistent with the product being principally bis(butyl phthalatobutyltin) oxide.

Claims (9)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A compound of the formula:

wherein:
Q and Q', which may be the same or different, each represent a group of the formula or an arylene group R1, R2, R3 and R4, which may be the same or different, each represent an unsubstituted alkyl group each n independently, represent zero or an integer from 1 to 10, and x represents an integer less than 6.

2. A compound according to Claim 1, wherein R1, R2, R3 or R4 represents a C1 to C6 alkyl group.

3. A compound according to Claim 1 wherein R1 and R2 are identi-cal.

4. A compound according to Claim 1 wherein x represents an integer less than 4.

5. A compound according to Claim 5 wherein x represents 1.

6. A process for the preparation of a compound of the formula which process comprises: reacting a tin oxide of the empirical formula:
R1R2SnO

with a dicarboxylic acid alkyl ester of the formula:
R3OOCQCOOH and/or R4OOCQ'COOH
wherein:
R1, R2, R3, R4, Q and Q' are defined in Claim 1.

7. A process according to Claim 6 wherein said tin oxide is reacted with said acid alkyl ester in a stoichiometric ratio of 1:1 thereby providing a compound wherein x = 1.

8. A process according to Claim 6 which is carried out in an anhydrous hydrocarbon solvent.

9. A process according to Claim 8 wherein the solvent is sodium-dried.