GB1604224A

GB1604224A - Polyurethane catalysts

Info

Publication number: GB1604224A
Application number: GB20491/77A
Authority: GB
Original assignee: Rubber and Plastics Research Association of Great Britain
Current assignee: Rubber and Plastics Research Association of Great Britain
Priority date: 1977-05-16
Filing date: 1977-05-16
Publication date: 1981-12-02
Also published as: FR2390995A1; DE2821306A1; JPS5416431A; CA1133001A

Description

(54) IMPROVEMENTS RELATING TO POLYURETHANE CATALYSTS (71) We, RUBBER AND PLASTICS RESEARCH ASSOCIATION, of Great Britain, a British company, of Shawbury, Shrewsbury S74 4NR, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: 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, such as 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 polyurethane reaction to commence before the components are completely mixed.

These problemsc would be minimised if a highly active catalyst having a delayedaction 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.

an associated form. When x= 1 the structure may be a dimer of the formula:

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.

R1, R2, R3 and R.1, which may be the same or different, each represent a substituted or unsubstituted alkyl group; n represents zero or an integer from 1 to 10, preferably from 1 to 6; and x represents an integer less than 6, preferably less than 4, especially 1.

In the above formulae Ra, Ra, Ra or R4 suitably represents an unsubstituted alkyl group, for example a C1 to CR alkyl group, preferably a C1 to C4 alkyl group.

Generally, Ra and Ra will be identical and it is particularly preferred that they both represent butyl groups. Suitably, Ra and R4 will be identical. It is preferred that Ra and R4 both 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:

It is not known, whether, at the low concentrations encountered in polyurethaneforming reactions, these compounds are associated or not The above-mentioned compounds of the invention are catalysts per se for the production of polyurethane. The compounds of the invention can also react with dihydroxyl compounds, for example glycols and polyetherglycols, under ester interchange conditions to produce polymeric tin-containing esters having hydroxyl groups in the terminal positions. These are also found to be catalysts for polyurethane production. Furthermore, such catalytic polymeric tin-containing esters also react with isocyanates to produce tin-containing polyurethanes which are themselves catalysts for further polyurethane production.

The compounds of the invention (hereinafter referred to as monomeric or telomeric tin-containing diesters and abbreviated as MTE and TTE, respectively) may be prepared in accordance with a process of the invention, which process comprises reacting a compound of the empirical formula: R1R,SnO with a dicarboxylic acid alkyl ester of the formula: R300CQCOOH and/or D4OOCQCOOH wherein Ra, Ra, Ra, Ra, Q and Q' are hereinabove defined. For example, dibutyltin oxide may be reacted with adipic acid monoethyl ester or phthalic acid monobutyl ester. The reactants are suitably mixed in the appropriate stoichiometric ratio and reaction is conveniently 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 Such compounds are catalysts for the production of polyurethanes; and where foam products are produced from them these are of very fine texture. In addition to showing catalytic activity the compounds of this invention are non-volatile stabilisers for poivvinvlchloride.

This invention Drovides a polyurethane prepared using a catalyst of the invention as herein defined. The polvurethane may be an elastomer; it may be a foam.

Gel times measured for test-tube scale reactions of Dolvols with toluene diisocyanate (TDI) and with diphenylmethane diisocyanate (MDI) are given in Tables 1 and 2.

When reaction rates are compared in terms of the respective gel times, then it is clear that the monomeric or telomeric tin-containing diesters are efficient catalysts and are indeed faster than conventional catalysts such as dibutyltin dilaurate (DBTL).

However when absolute reaction rates are measured for dilute solution reactions, then it becomes apparent that the 1:1 monomeric tin ester gives a somewhat slower reaction than DBTL when equivalent concentrations (either mole% or wt%) of catalyst are used (Table 3). However this relationship is reversed when the temperature is increased.

In this case the reaction under investigation was that of iso-propanol (0.01 mole) with phenyl isocyanate (0.01 mole) in dry toluene (100 ml) at ambient temperature (220-240C) and at an elevated temperature of 45 C. Residual isocyanate in the reaction mixture was monitored during the reaction by taking an aliquot (5 ml) of the mixture and digesting this in a mixture of dry and redistilled toluene (50 ml) and di-n-butylamine (50 ml, 0.2N solution in toluene). This mixture was left to stand for 15 minutes and then residual amine was estimated by adding iso-propanol (225 ml) to the mixture and then titrating against 0.1N HCI using bromocresol green as indicator.

TABLE 1 Examples of results for small scale reactions at 300C.

Catalyst type Wt. of catalyst (Ens) Gel time (min.) DBTL 20 9 1:1 MTE 20 4

(As noted earlier, MTE and TTE refer, respectively, to the monomeric or telomeric tin-containing diester of the invention; the prefixed ratio refers to the stoichiometry of the reactant half ester and tin oxides, respectively, used in their preparation.) TABLE 2 Summary of results for'small scale reaction at 700C.

Wt. of MDI Wt. of polyether Wt. of catalyst Gel time Catalyst type ~ (g) (g) (mg) Gnin-6ec) DBTL 1.48 5.92 15-00 0.11 DBTL 1.49 5.96 18-15 O.5:1 TTE 1.35 5.40 9-10 0.09 0.S:1 TTE 2.00 8.00 15-00 1:1 MTE 1.48 5.92 13--10 0.13 1:1 MTE 2.06 8.24 15-30 TABLE 3 Summary of results for solution reactions

CH3 catalyst (0.1 mole %) C6H5NCO + CHOH - > toluene (100 mr) CH, toluene (100 ml) 0.01 mole 0.01 mole % conversion of NCO after Catalyst type Temperature 60 min.

1:1 MTE ambient 38 (22 - 240C) DBTL ambient 50 (22 - 240C) 1:1 MTE 450C 86 DBTL 450C 81 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 monomeric tin-containing diester (x=l in the generic formula) are represented by curves Ic 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 viscosity (cps) (log scale), as a measure of the amount of polyurethane formed1 versus reaction time (min.). The reactants were polyether glycol and toluene diisocyanate intially maintained at 220 C. Curve (a) is a plot in which the catalyst is 64 ng (Ing=l0-8) of dibutyltin bis(ethyl adipate); curve (c) in which the catalyst is 64 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 catalyst is 128 ng of dibutyltin dilaurate (DBTL).

The viscosities in each run were measured as follows.

Into a 400 beaker was measured a 250 g sample of previously dried poly (oxypropylene glycol (PPG) of Mol Wt. 1000. The beaker and its contents were then placed in an insulating block of polyurethane foam. This block measured 22cm X 22cm X 10cm and the beaker was placed in a central cut out of 7cm depth. A dilute solution of the appropriate tin ester in toluene (typically 0.1 g in 1 litre) was prepared and microlitre quantities 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 up to 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 (43.54 g) 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 occurred.

In addition to the desirable delayed action effect noted above, it will be seen that the monomeric tin diesters of the invention are much more reactive than the conventional DBTL catalyst As is general with such systems the presence of a small amount of catalyst, typically 15 to 20 ng in the above system, was required in order to obtain any catalytic effect.

EXAMPLE 1.

Synthesis of 1:1 Monomeric Tin-containing Di-Ester.

15 g of dibutyltin oxide (0.06 mole) and 10.5 g of adipic acid monoethyl ester (0.06 mole) were placed in a one litre flask and 750 ml of re-distilled 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. 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 45 minutes while the temperature rose to 130"C. The oil vacuum pump was then applied (pressure 1-2 mm Hg) and the remainder of the solvent was distilled off at 130"C. The reaction product was a clear, amber liquid.

EXAMPLE 2.

Synthesis of 0.5:l1 Telomeric Tin-containing Di-Ester.

15 g of dibutyltin oxide (0.06 mole) and 5.25 g of adipic acid monoethyl ester (0.03 mole) were placed in a one litre flask and 750 ml toluene were 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 100 ml of solution remained. On cooling a fine white precipitate of dibutyl tin oxide (0.98 g) was formed and was filtered off. The solution was placed in a 150 ml flask and heated under vacuum (water vacuum pump) over 45 minutes while the temperature rose to 130"C. The oil vacuum pump was then applied (pressure 1-2 mm Hg) and the remainder of the solvent was distilled off at 1300 C. The reaction product was an amber glassy solid which softened at around 1500C to a clear, amber liquid.

EVIDENCE FOR STRUCTURES OF MONOMERIC AND TELOMERIC TIN-CONTAINING DI-ESTERS.

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 at 15.75 fiam (635 cm-1) characteristic of Sn O-Sn. A 300 MH 'H NMR spectrum of the product (in CC14) has been obtained (Figure 3 of the accompanying drawings). The assignments shown in the figure are 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%; C,2H2OSn1 requires C, 46.4; H, 7.5; 0, 17.4%).

The presence of infrared absorption bands at 20.5 ,am (485 cm-l) and around 6-6.5 am suggests that this stannoxane may be associated in some way, possibly as a cyclic dimer.

The unassociated structure is probably:

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 from either of the two reactants; the spectrum was characterised by a strong absorption at around 16,um characteristic of Sn-O-Sn.

In view of the reaction stoichiometrv and the polymeric nature of dibutvltin oxide, a polystannoxane structure is suggested (x > l in the generic formula). The results of m;cro-analvsis are consistent with a structure for which the mean value of x is 3 (Found: C, 43.5; H, 7.5; 0, 13.5%; C48H98OllSn4 requires C, 43.5; H, 7.4; O, 13.5%).

EXAMPLE 3.

Synthesis of Polyurethane Elastomer at 300 C.

12.15 g (30 mmole, 61 meq.) of dry poly(oxypropylene) glycol of MW 400 and a small amount of catalyst (typically 10-80 mg) were mixed in a B24 test-tube.

8.10 g (2.7 mmole, 8.1 meq.) of dry poly(oxypropylene) triol of MW 3000 and 5.0 ml (6.1 g, 70 meq.) of toluene diisocyanate (TDI) were added to the reaction mixture. The mixture was placed in a constant temperature bath at 300C and was stirred for 1 minute.

EXAMPLE 4.

Synthesis of Polyurethane Elastomer at 70"C.

Equivalent quantities of poly(oxypropylene) triol (ca. 6 g) of MW 1500 and MDI (ca. 1.5 g) were mixed with a small amount of catalyst (ca. 0.1 mg) in a B24 test-tube. The test-tube was placed in a 700C oil bath and the mixture was stirred for 1 minute.

EXAMPLE 5.

Synthesis of Polyurethane Foam.

The polyether and catalyst were pre-mixed as above. Water (0.5 g) and sil;rone (0.25 g) were added to a mixture of 12 g of poly(oxypropylene) triol of MW 3000 and 20-80 mg of catalyst. Five ml of TDI were then added and the mixture was warmed to 300C and stirred over 15-20 seconds.

EXAMPLE 6.

Synthesis of 1:1 Monomeric Tin-Containing Diester of an Aromatic Acid.

15 g of dibutyltin oxide (0.06 mole) and 13.3 g of phthalic acid monobutyl ester (0.06 mole) were placed in a one litre flask and 750 ml of re-distilled sodiumdried toluene were added. On heating to the boil, the solution began to clear and the azeotrope of toluene and water was 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 45 minutes while the temperature rose to 1300C. The oil vacuum pump was then applied (pressure 1-2 mm Hg) and the remainder of the solvent was distilled off at 1300C. The reaction product was an amber liquid. The infra-red spectrum was consistent with the product being principally bis(butyl phthalatobutyltin) oxide.

WHAT WE CLAIM IS: 1. A compound of the formula:

wherein: Q and Q' which may be the same or different, each represent a group of the formula $CH2+n or an arylene group; Ra, R,, Ra and Ra, which may be the same or different, each represent a substituted or unsubstituted alkyl group; n represents zero or an integer from 1 to 10, and x represents an integer less than 6.

2. A compound according to Claim 1 wherein Ra, R,, R, or R4 represents an unsubstituted alkyl group.

3. A compound according to Claim 1 or 2, wherein Ra, Ra, Ra or R4 represents a C1 to C" alkyl group.

4. A compound according to Claim 3 wherein Ra, R,, Ra or R4 represents a C1 to C4 alkyl group.

5. A compound according to any preceding claim wherein Ra and Ra are identical.

6. A compound according to Claim 5 wherein Rl and Ra represent butyl groups.

7. A compound according to any preceding claim wherein Ra and Ra are identical.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. EXAMPLE 3. Synthesis of Polyurethane Elastomer at 300 C. 12.15 g (30 mmole, 61 meq.) of dry poly(oxypropylene) glycol of MW 400 and a small amount of catalyst (typically 10-80 mg) were mixed in a B24 test-tube. 8.10 g (2.7 mmole, 8.1 meq.) of dry poly(oxypropylene) triol of MW 3000 and 5.0 ml (6.1 g, 70 meq.) of toluene diisocyanate (TDI) were added to the reaction mixture. The mixture was placed in a constant temperature bath at 300C and was stirred for 1 minute. EXAMPLE 4. Synthesis of Polyurethane Elastomer at 70"C. Equivalent quantities of poly(oxypropylene) triol (ca. 6 g) of MW 1500 and MDI (ca. 1.5 g) were mixed with a small amount of catalyst (ca. 0.1 mg) in a B24 test-tube. The test-tube was placed in a 700C oil bath and the mixture was stirred for 1 minute. EXAMPLE 5. Synthesis of Polyurethane Foam. The polyether and catalyst were pre-mixed as above. Water (0.5 g) and sil;rone (0.25 g) were added to a mixture of 12 g of poly(oxypropylene) triol of MW 3000 and 20-80 mg of catalyst. Five ml of TDI were then added and the mixture was warmed to 300C and stirred over 15-20 seconds. EXAMPLE 6. Synthesis of 1:1 Monomeric Tin-Containing Diester of an Aromatic Acid. 15 g of dibutyltin oxide (0.06 mole) and 13.3 g of phthalic acid monobutyl ester (0.06 mole) were placed in a one litre flask and 750 ml of re-distilled sodiumdried toluene were added. On heating to the boil, the solution began to clear and the azeotrope of toluene and water was 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 45 minutes while the temperature rose to 1300C. The oil vacuum pump was then applied (pressure 1-2 mm Hg) and the remainder of the solvent was distilled off at 1300C. The reaction product was an amber liquid. The infra-red spectrum was consistent with the product being principally bis(butyl phthalatobutyltin) oxide. WHAT WE CLAIM IS:

1. A compound of the formula:

5. A compound according to any preceding claim wherein Ra and Ra are identical.

6. A compound according to Claim 5 wherein Rl and Ra represent butyl groups.

7. A compound according to any preceding claim wherein Ra and Ra are identical.

8. A compound according to Claim 7 wherein Ra and Rl represent ethyl or butyl

groups.

9. A compound according to any preceding claim wherein x represents an integer less than 4.

10. A compound according to Claim 9 wherein x represents 1.

11. A compound according to any preceding claim wherein Q and Q1 are identical.

12. A compound according to any preceding claim wherein n represents an integer from 1 to 6.

13. A compound according to any of Claims 1 to 11 wherein Q and Q1 represent phenylene groups.

14. A compound according to Claim 1 substantially as hereinbefore described with reference to any one of Examples 1, 2, or 6.

15. A process for the preparation of a compound according to any preceding claim, which process comprises reacting a compound of the empirical formula: RARE SO with a dicarboxylic acid alkyl ester of the formula: R4OOCQCOOH and/or 00CQ'COOH wherein: Ra, Ra, Ra, Rs, Q and Q' are defined in any of Claims 1 to 8, 11, 12 and 13.

16. A process according to Claim 15 wherein the tin oxide is reacted with the acid ester in a stoichiometric ratio of 1:1 thereby affording a compound as defined in Claim 10.

17. A process according to Claim 15 or 16 which is carried out in an anhydrous hydrocarbon solvent.

18. A process according to Claim 17 wherein the solvent is sodium-dried.

19. A process according to Claim 15 substantially as hereinbefore described with reference to any one of Examples 1, 2, or 6.

20. A compound according to Claim 1 whenever prepared by the process of any of Claims 15 to 19.

21. A polyurethane prepared using a catalyst according to any of Claims 1 to 14 or 20.

22. A polyurethane according to Claim 21 which is an elastomer.

23. A polyurethane according to Claim 21 or 22 which is foamed.