RIGID POLYURETHANE FOAM MADE WITH A HYDROCARBON BLOWING AGENT AND 1,1,1,4,4,4-HEXAFLUOROBUT-2-ENE

Abstract

Polyurethane thermal insulating foam is made in the presence of a small amount of cis- and/or trans-1,1,1,4,4,4-hexafluorobut-2-ene and a hydrocarbon blowing agent. Very low lambda values are obtained.

Claims

1. A method of making a polyurethane foam, comprising forming a reaction system and curing the reaction system to produce the polyurethane foam, wherein the reaction system comprises: a) at least one polyisocyanate; b) at least one polyol; c) at least one urethane catalyst; d) at least one foam-stabilizing surfactant; e) 0 to 3 weight-percent water, based on the combined weights of components b), c), d) and e); f) 1 to 6 parts by weight, per 100 parts by weight of components b), c), d) and e), of cis- and/or trans- 1,1,1,4,4,4-tetrafluorobut-2-ene; and g) 8 to 30 parts by weight, per 100 parts by weight of components b), c), d) and e), of one or more hydrocarbons having 4 to 6 carbon atoms.

2. The method of claim 1 wherein the reaction system contains 2 to 4 parts by weight, per 100 parts by weight of components b), c), d) and e), of cis- and/or trans-1,1,1,4,4,4-tetrafluorobut-2-ene.

3. The method of claim 1 wherein the reaction system contains 12 to 20 parts by weight, per 100 parts by weight of components b), c), d) and e), of one or more hydrocarbons having 4 to 6 carbon atoms.

4. The method of claim 1 wherein the reaction system contains no more than 30 weight percent of an alkoxylated o-toluene diamine polyol, based on the combined weights of components b), c), d) and e).

5. The method of claim 1 wherein the reaction system is introduced into a cavity and cured in the cavity, and a pressure of 700 to 950 millibars actual is maintained in the cavity as the reaction system is introduced into the cavity.

6. A polyurethane foam made in the method of claim 1.

7. The foam of claim 6 which exhibits a lambda value of at most 18.5 mw/m-° K as measured according to EN 12667 at an average plate temperature of 10° C.

8. The foam of claim 6 which exhibits a lambda value of at most 18.25 mw/m-° K as measured according to EN 12667 at an average plate temperature of 10° C.

9. The foam of claim 6 which has a density of 28 to 40 kg/m.sup.3 as measured according to ASTM 1622-88.

10. A method of manufacturing a thermally insulated cabinet, comprising A) positioning an outer shell member and an inner liner member so as to define a cavity therebetween; B) introducing the reaction system into the cavity; and C) curing the reaction system such that it expands and reacts to produce a polyurethane foam that fills the cavity and adheres to the outer shell member and to the inner liner member, wherein the reaction system comprises: a) at least one polyisocyanate; b) at least one polyol; c) at least one urethane catalyst; d) at least one foam-stabilizing surfactant; e) 0 to 3 weight-percent water, based on the combined weights of components b), c), d) and e); f) 1 to 6 parts by weight, per 100 parts by weight of components b), c), d) and e), of cis- and/or trans- 1, 1,1,4,4,4-tetrafluorobut-2-ene; and g) 8 to 30 parts by weight, per 100 parts by weight of components b), c), d) and e), of one or more hydrocarbons having 4 to 6 carbon atoms.

11. The method of claim 10 wherein the reaction system contains 2 to 4 parts by weight, per 100 parts by weight of components b), c), d) and e), of cis- and/or trans-1,1,1,4,4,4-tetrafluorobut-2-ene and 12 to 20 parts by weight, per 100 parts by weight of components b), c), d) and e), of one or more hydrocarbons having 4 to 6 carbon atoms.

12. The method of claim 10 wherein the reaction system contains no more than 65 weight percent of an alkoxylated o-toluene diamine polyol, based on the combined weights of components b), c), d) and e).

13. The method of claim 10 wherein the reaction system contains no more than 30 weight percent of an alkoxylated o-toluene diamine polyol, based on the combined weights of components b), c), d) and e).

14. The method of claim 10 wherein a subatmospheric pressure is maintained in the cavity during at least step B).

15. The method of claim 14 wherein the subatmospheric pressure is 700 to 950 millibars actual.

Description

Example 1 and Comparative Sample A

[0053] To make Example 1, 100 parts by weight of Formulated Polyol A is combined at about 23° C. with 3 parts by weight trans-1,1,1,4,4,4-hexafluorobut-2-ene, 13.2 parts by weight cyclopentane and then with 140 parts of the PMDI (122 index) to form a reaction mixture. A portion of the reaction mixture is immediately injected into a rectangular “Brett” mold having dimensions of 200 cm×20 cm×5 cm (˜6′6″×8″×2″). The Brett mold is oriented with the 200 cm direction oriented vertically and preheated to 45±5° C. The Brett mold is at atmospheric pressure. The composition is permitted to expand against its own weight and cure inside the mold. The amount of polyurethane-forming composition is selected such that the resulting foam just fills the mold. The density of the resulting foam is then measured and reported as the minimum fill density (MFD). The foam is demolded and the experiment repeated, except that the mold is overpacked by 10%. The lambda value of the resulting foam is determined according to EN 12667 using an average plate temperature of 10° C.

[0054] Another portion of the reaction mixture is poured into a 20 cm×20 cm×20 cm box and evaluated visually for cream time. A spatula is pressed to the surface of the curing reaction mixture to evaluate for gel time (the time after mixing at which strings of polymer stick to the spatula) and tack-free time (the time after mixing at which the polymer no longer sticks to the spatula).

[0055] The foregoing experiments are repeated using the Example 1 formulation except that a partial vacuum (−0.2 atmosphere gauge, 80 kPa actual) is drawn on the Brett mold during filling and foam expansion until the reaction system has gelled.

[0056] Comparative Sample A is made in an analogous manner by combining 100 parts by weight of Formulated Polyol A with 14.5 parts of cyclopentane and 140 parts of the PMDI (1.22 index). Cream time, gel time and tack-free time are measured as before. Minimum fill density and lambda value are determined for foams made in the Brett mold at ambient pressure and the reduced pressure as described with regard to Example 1.

[0057] Results of the foregoing testing are as indicated in Table 1.

TABLE-US-00001 TABLE 1 Comp. Sample A Example 1 Trans-1,1,1,4,4,4- 0 3 hexafluorobut-2-ene Cyclopentane 14.5 13.2 Cream time, seconds 3 4 Gel time, seconds 27 26 Tack-free time, seconds 34 31 Atmospheric Pressure Brett Mold Results MFD, g/L 35.4 33.7 Lambda, mW/m-° K 18.9 18.3 % Lambda Reduction — 3.2% Vacuum-Assisted Brett Mold Results MFD, g/L 29.3 29.0 Lambda, mW/m-° K 18.9 18.3 % Lambda Reduction — 3.1%

[0058] As the data in Table 1 shows, a significant reduction in lambda is obtained by adding 3 parts by weight of 1,1,1,4,4,4-hexafluorobut-2-ene to the formulation and reducing the amount of cyclopentane by about 10%. The lambda value obtained with Example 1 is very low, particularly considering that the foam formulations contain rather low proportions of o-TDA-initiated polyols. No significant change in cream, gel or tack-free times is seen.

Examples 2 and 3 and Comparative Sample B

[0059] Foam Examples 2 and 3 are made by combining 100 parts of Formulated Polyol B with 3 parts either trans- or cis-1,1,1,4,4,4-hexafluorobut-2-ene, 14.8 parts of cyclopentane and PMDI (119 index) in the same general manner as described in the previous examples. Comparative Sample B is made by combining 100 parts of Formulated Polyol B with 16 parts cyclopentane and the PMDA (121 index) and foaming the resulting reaction mixture in an analogous way. Cream, gel and tack-free times are measured in each case, as are minimum fill density and lambda for foams produced in the Brett mold at each of ambient and reduced pressure. The results of the foam testing are as indicated in Table 2.

TABLE-US-00002 TABLE 2 Comp. Sample B Ex. 2 Ex. 3 Cis-1,1,1,4,4,4- 0 0 3 hexafluorobut-2-ene Trans-1,1,1,4,4,4- 0 3 0 hexafluorobut-2-ene Cyclopentane 16 14.8 14.8 Cream time, seconds 3 3 3 Gel time, seconds 21 21 20 Tack-free time, seconds 24 24 22 Atmospheric Pressure Brett Mold Results MFD, g/L 35.9 35.3 36.5 Lambda, mW/m-° K 18.65 18.1 18.1 % Lambda Reduction — 3.1 2.9 Vacuum-Assisted Brett Mold Results MFD, g/L 30.9 30.5 31.05 Lambda, mW/m-° K 18.4 18.2 18.05 % Lambda Reduction — 1.3 2.0

[0060] The data in Table 2 demonstrates that significant reductions in lambda value are achieved with the invention using either the cis- or trans-isomer of 1,1,1,4,4,4-hexafluorobut-2-ene. In this case, the improvements in insulation capacity are achieved even in a foam formulation that contains a large proportion of o-TDA-initiated polyols. Such foams are previously known to have very low lambda values; a further significant reduction is unexpected and quite beneficial.

Example 4 and Comparative Samples C and D

[0061] Comparative Sample C is prepared by combining 100 parts by weight of Formulated Polyol A with 14.5 parts of cyclopentane and PMDI (112 index) and processing the resulting reaction mixture into foam in the same general manner as described in the previous examples, using a reduced mold pressure and 10% overpacking. Comparative Sample D is prepared in like manner by combining 100 parts by weight of Formulated Polyol A with 6.6 parts of cyclopentane, 18 parts of cis-1,1,1,4,4,4-hexafluorobut-2-ene and PMDI (112 index).

[0062] Example 4 is made in the same general way, by combining 100 parts Formulated Polyol B, 3 parts of cis-1,1,1,4,4,4-hexafluorobut-2-ene, 14.8 parts of cyclopentane and PMDI (112 index).

[0063] Lambda is measured. Foam densities are about 35 g/L in each case. The ingredients in each case and the results of the foam testing are as indicated in Table 3.

TABLE-US-00003 TABLE 3 Comp. Comp. Sample C Sample D Ex. 1 Ex. 4 Formulated Polyol A 100 100 100 0 Formulated Polyol B 0 0 0 100 Cis-1,1,1,4,4,4- 0 18 0 3 hexafluorobut-2-ene Trans-1,1,1,4,4,4- 0 0 3 0 hexafluorobut-2-ene Cyclopentane 14.5 6.6 14.8 14.8 Lambda, mW/m-° K 18.9 17.8 18.3 18.1 % Lambda Reduction — 5.8 3.1 4.2

[0064] As can be seen by comparing Comparative Samples C and D, a lambda reduction of 5.8% (relative to Comp. Sample C) is obtained by including 18 parts of cis-1,1,1,4,4-hexafluorobut-2-ene, and reducing the amount of cyclopentane to 6.6 parts. This result requires a large amount of the expensive 1,1,1,4,4,4-hexafluorobut-2-ene material, which results in a large cost disadvantage; 18 parts of cis-1,1,1,4,4,4-hexafluorobut-2-ene are needed to produce a 1.1 mW/m-° K reduction in lambda. Examples 1 and 4 show that, in two different polyol systems, over half to almost 75% of that benefit can be obtained with this invention, by instead adding only one-sixth (3 parts) of the amount of 1,1,1,4,4,4-hexafluorobut-2-ene. In Example 1, a reduction of 0.6 mW/m-° K is obtained using only 3 parts of 1,1,1,4,4,4-hexafluorobut-2-ene; in Example 4, a 0.8 mW/m-° K is obtained while using 3 parts of 1,1,1,4,4,4-hexafluorobut-2-ene. With this invention, most of the advantage of using the 1,1,1,4,4,4-hexafluorobut-2-ene is obtained at only a fraction of the usage level and only a fraction of the cost.