Method of Molding Rigid Polyurethane Foams with Enhanced Thermal Conductivity

• US 20080255262A1
• Filed: 11/03/2006
• Published: 10/16/2008
• Est. Priority Date: 11/14/2005
• Status: Active Grant

• Current Assignee: Dow Global Technologies LLC (Dow, Inc.)
• Original Assignee: Dow Global Technologies, Inc. (Dow, Inc.)
• Inventors: Parenti, Vanni, De Vos, Hans A. G.
• Granted Patent: US 7,943,679 B2
• Time in Patent Office: Days
• US Class Current: 521/155
• CPC Class Codes: B29C 44/38 into a closed space, i.e. to make articles of definite length B29C44/365 and B29C44/367 take precedence
• CPC Class Codes: C08G 18/482 Mixtures of polyethers containing at least one polyether containing nitrogen
• CPC Class Codes: C08G 18/4829 Polyethers containing at least three hydroxy groups C08G18/4833 - C08G18/5096 take precedence
• CPC Class Codes: C08G 18/7664 containing alkylene polyphenyl groups
• CPC Class Codes: C08G 2110/0025 rigid
• CPC Class Codes: C08G 2110/005 < 50kg/m3
• CPC Class Codes: C08J 2203/12 Organic compounds only containing carbon, hydrogen and oxygen atoms, e.g. ketone or alcohol
• CPC Class Codes: C08J 2203/14 Saturated hydrocarbons, e.g. butane; Unspecified hydrocarbons
• CPC Class Codes: C08J 2203/142 Halogenated saturated hydrocarbons, e.g. H3C-CF3
• CPC Class Codes: C08J 2205/10 Rigid foams
• CPC Class Codes: C08J 2375/04 Polyurethanes
• CPC Class Codes: C08J 9/14 organic

Abstract

The present invention is to a molded rigid polyurethane foam for application in appliance, having a reduced thermal conductivity at densities between 33 and 38 kg/m³ and a process for the production of such foams. The molded rigid polyurethane foam have a ratio of applied foam density (kg/m3) to lambda (mW/mK), measured at 10° C., 24 hours after foam production from 1.65 and to 2.15 and are obtained by the process of injecting into a closed mold cavity under reduced pressure a reaction mixture at a packing factor of 1.1 to 1.9 and the reaction mixture comprises: A) an organic polyisocyanate; B) a physical blowing agent, C) a polyol composition containing at least one polyol with a functionality of 3 or greater and a hydroxyl number between 200 and 800 and a water content of 0 to 2.5 weight percent of the total polyol composition; D) catalyst and E) auxiliary substances and/or additives.

Claims

1. A molded rigid polyurethane foam having a ratio of molded foam density (kg/m³) to Lambda_(10°

C.) (mW/m.K), measured 24 hours after foam production, from 1.65 to 2.15, obtained by the process of injecting into a closed mold cavity a reaction mixture at a packing factor of 1.03 to 1.9 wherein the mold cavity is under a reduced pressure and the reaction mixture comprises;

A) an organic polyisocyanate;

B) a physical blowing agent,

C) a polyol composition containing at least one polyol with a functionality of 3 or greater and a hydroxyl number between 300 and 800

D) water present at 0 to 2.5 weight percent of the total polyol formulation;

E) catalyst and

F) auxiliary substances and/or additives;

wherein the foam has a molded density of 33 to 38 kg/m³.

2. The foam of claim 1 wherein the mold cavity is at a pressure from 300 to 950 mbar.

3. The foam of claim 2 wherein the mold cavity has an initial pressure of 500 to 850 mbar.

4. The foam of any of the preceding claims wherein the packing factor is from 1.1 to 1.6.

5. The foam of any of the preceding claims wherein the isocyanate index is 105 to 125.

6. The foam of any of the preceding claims wherein the organic polyisocyanate is an aromatic polyisocyanate selected from 4,4′

-, 2,4′

- and 2,2′

-diphenylmethane diisocyanate, polyphenyl-polymethylene polyisocyanates, 2,4- and 2,6-tolylene diisocyanates, or mixtures thereof.

7. The foam of claim 6 wherein the organic polyisocyanate is a mixture of diphenylmethane diisocyanate and polyphenyl-polymethylene polyisocyanate wherein the diphenylmethane diisocyanate isomer content is from 30 to 60 percent by weight of the polyisocyanate.

8. The foam of claim 1 wherein the foam has thermal conductivity of 18 to 21 to 21 mW/m.K measured at 10°

C. average temperature, 24 hours after foam production.

9. The foam of claim 1 wherein the foam has a lambda of 19 to 20 mW/m.K.

10. The foam of claim 1 wherein the physical blowing agent has a boiling point greater than 10°

C.

11. The foam of claim 10 wherein the blowing agent is a hydrocarbon, a hydrofluorocarbon, a hydrochlorofluorocarbon, methyl formate or trans-dichloroethene.

12. The foam of claim 10 wherein the blowing agent is 245fa, 365mfc, 227 or a mixture thereof.

13. The foam of claim 10 wherein the blowing agent is a hydrocarbon selected from n-pentane, iso-pentane, cyclopentane, n-butane, cyclohexane or a mixture thereof.

14. The foam of claim 10 wherein the physical blowing agent is present in an amount from 10 to 30 weight percent of the polyol composition.

15. The foam of claim 1 wherein the demold time is less than 6 minutes.

16. The foam of claim 1 wherein the demold time is less than 5 minutes.

17. The foam of claim 1 wherein the polyol composition has a viscosity of 1000 mPa·

s at 25°

C.

18. The foam of claim 1 wherein the polyol composition contains at least one polyol prepared by anionic polyaddition of at least one alkylene oxide onto at least one aromatic initiator molecule containing an amine.

19. The foam for claim 18 wherein the initiator is selected from aromatic polycarboxylic acids, aromatic hydrocarboxylic acids and aromatic aminocarboxylic acids, aromatic mono- and polyamines, condensates of phenols, formaldehyde and optionally dialkanolamines, or a mixture thereof.

20. The foam of claim 18 wherein the initiator molecule is an aromatic polyamine selected from 1,2-1,3- and 1,4-phenylenediamine, 1,3-, 2,4-, 3,4- and 2,6-tolylenediamines, 4,4′

-, 2,4′

- and 2,2-diaminodiphenylmethane, polyphenyl-polymethylene-polyamines, and mixtures thereof.

21. The foam of claim 20 wherein the aromatic amine initiated polyol comprises from 10 to 60 wt percent of the polyol composition.