WO2001018099A1

WO2001018099A1 - Use of 1,1,1,3,3-pentafluoropropane as a flame suppressant in c2-c6 hydrocarbon blown polyurethane foam

Info

Publication number: WO2001018099A1
Application number: PCT/US2000/024772
Authority: WO
Inventors: Mary C. Bogdan; John S. Wickham; Leslie B. Bement
Original assignee: Alliedsignal Inc.
Priority date: 1999-09-10
Filing date: 2000-09-08
Publication date: 2001-03-15
Also published as: AU7128900A

Abstract

The invention relates to polyurethane and polyisocyanurate closed-cell foams. More particularly, the invention relates to the use of 1,1,1,3,3-pentafluoropropane (HFC-245fa) to reduce the flammability characteristics of polyurethane and polyisocyanurate closed-cell foams prepared with a blowing agent comprising a C2-C6 hydrocarbon.

Description

USE OF 1,1,1,3,3-PENTAFLUOROPROPANE AS A FLAME SUPPRESSANT IN C₂-C₆ HYDROCARBON BLOWN POLYURETHANE FOAM

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application Serial No. 60/153,187 filed September 10, 1999.

FIELD OF THE INVENTION

The invention relates to polyurethane and polyisocyanurate closed-cell foams. More particularly, the invention relates to the use of 1,1, 1,3,3 -pentafluoropropane (HFC-245fa) to reduce the flammability characteristics of hydrocarbon blown polyurethane and polyisocyanurate closed-cell foams.

BACKGROUND OF THE INVENTION

The class of foams known as low density rigid polyurethane or polyisocyanurate foam has utility in a wide variety of insulation applications including roofing systems, building panels, refrigerators and freezers. A critical factor in the large-scale commercial acceptance of rigid polyurethane foams in the building insulation industry has been their ability to provide a good balance of properties. Rigid polyurethane and polyisocyanurate foams are known to provide outstanding thermal insulation, excellent fire properties and superior structural properties at reasonably low densities.

The methods of producing polyurethane and polyisocyanurate foams are generally known and consist in general of the reaction of an organic polyisocyanurate (including diisocyanate) and a polyol or mixture of polyols in the presence of a volatile blowing agent, which is caused to vaporize by the heat liberated during the reaction of isocyanate and polyol. This reaction can be enhanced through the use of amine and/or other catalysts as well as surfactants. The catalysts ensure adequate curing of the foam, while the surfactants regulate and control cell size. Flame- retardants are traditionally added to rigid polyurethane or polyisocyanurate foam to reduce their flammability.

Historically, polyurethane and polyisocyanurate foams have been made using fluorocarbon blowing agents, for example, trichlorofiuoromethane (CFC-11). Fluorocarbons act not only as blowing agents by virtue of their volatility, but also are encapsulated or entrained in the closed cell structure of the rigid foam and are the major contributor to the low thermal conductivity properties of rigid urethane foams.

The escape of certain fluorocarbons, most notably chloro fluorocarbons, to the atmosphere is now recognized as potentially contributing to the depletion of the stratospheric ozone layer and to global warming. Hydrochloro fluorocarbons

(HCFCs), for example, 1,1-dichloro-l-fluoroethane (HCFC-141b), have provided an interim solution in many applications due to their good thermal insulating properties and low or non-flammability. However, because HCFCs also possess some ozone- depletion potential, there remains a need for substitutes for the HCFCs as well as the CFCs.

Presently, hydrocarbons (HCs) and partially fluorinated hydrocarbons (HFCs) are the two leading classes of alternative blowing agents materials that are being evaluated by the rigid foam industry because they contain no ozone-depleting chlorine. Hydrocarbon blowing agents, particularly five-carbon member hydrocarbons such as n-pentane, isopentane and cyclopentane, are advantageous in that they are inexpensive and do not deplete stratospheric ozone. However, foams produced from hydrocarbon blowing agents require the addition of a flame retardant and often do not meet the fire performance standards of fluorocarbon blown foams notwithstanding the presence of the flame retardant. Although HFC blowing agents are environmentally more acceptable than chlorine containing blowing agents, they, too, are inferior in flammability characteristics to such CFC and HCFC predecessors.

It is convenient in many applications to provide the components for polyurethane or polyisocyanurate foams in pre-blended foam formulations. Most typically, the foam formulation is pre-blended into two components. The isocyanate or polyisocyanate composition comprises the first component, commonly referred to as the "A" component or "A-side". The polyol or polyol mixture, surfactant, catalysts, blowing agents, flame retardant, and other isocyanate reactive components comprise the second component, commonly referred to as the "B" component or "B- side". While the surfactant, catalyst(s) and blowing agent are usually placed on the polyol or B-side, they may be placed on either side, or partly on one side and partly on the other side. Accordingly, polyurethane or polyisocyanurate foams are readily prepared by bringing together the A- and B-side components either by hand mix, for small preparations, or preferably machine mix techniques to form blocks, slabs, laminates, pour-in-place panels and other items, spray applied foams, froths, and the like. Optionally, other ingredients such as fire retardant, colorants, auxiliary blowing agents, water, and even other polyols can be added as a third stream to the mix head or reaction site. Most conveniently, however, they are all incorporated into one B-side.

It is has now unexpectedly been discovered that the addition of HFC-245fa to the foam formulation dramatically improves the flammability characteristics of hydrocarbon blown foam. This result is particularly surprising in view of the fact that HFC-245fa would not be expected to have any flammability suppressant characteristics per se.

SUMMARY OF THE INVENTION

The invention relates to a method of preparing an isocyanate-based foam comprising reacting a mixture comprising:

(a) a polyisocyanate; and

(b) a polyol; in the presence of

(c) a blowing agent comprising at least one C₂-C₆ hydrocarbon; (d) a catalyst;

(e) a flame suppressing amount of 1,1,1,3,3-pentafluoropropane; and

(f) optionally one or more compounds selected from the group consisting of fire retardant, surfactant, colorant, auxiliary blowing agent, dispersing agent and cell stabilizer. The amount of 1,1,1,3,3-pentafluoropropane added is from about 1 to about 50 weight percent, preferably from about 1 to about 19 weight percent, and more preferably from about 1 to about 8 weight percent, based on the total weight of the polyol, blowing agent, catalyst and optional components of the mixture (i.e. the B-side).

The invention further relates to blowing agent compositions comprising a C₂-C₆ hydrocarbon and a flame suppressing amount of 1,1,1,3,3-pentafluoropropane. The amount of 1,1,1,3,3-pentafluoropropane is from about 1 to about 19 weight percent, preferably from about 1 to about 8 weight percent, based on the total weight of blowing agent.

The invention further relates to a closed cell foam composition prepared by foaming a polyisocyanate or polyisocyanurate in the presence of a blowing agent comprising a C₂-C₆ hydrocarbon and a flame suppressing amount of 1,1, 1,3,3 - pentafluoropropane. The amount of 1,1,1,3,3-pentafluoropropane is from about 1 to about 19 weight percent, preferably from about 1 to about 8 weight percent, based on the total weight of blowing agent.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term flame suppressing amount refers to that amount sufficient to reduce the ignitability and/or rate of burning of the foam composition.

With respect to the preparation of rigid or flexible polyurethane or polyisocyanurate foams using hydrocarbons as the blowing agent, any of the methods well known in the art can be employed. See Saunders and Frisch, Volumes I and II Polyurethanes Chemistry and Technology (1962). In general, polyurethane or polyisocyanurate foams are prepared by combining an isocyanate, a polyol or mixture of polyols, a blowing agent or mixture of blowing agents, and other materials such as catalysts, surfactants, and optionally, flame retardants, colorants, or other additives. Any organic polyisocyanate can be employed in polyurethane or polyisocyanurate foam synthesis inclusive of aliphatic and aromatic polyisocyanates. Preferred, as a class is the aromatic polyisocyanates. Preferred polyisocyanates for rigid polyurethane or polyisocyanurate foam synthesis are the polymethylene polyphenyl isocyanates, particularly the mixtures containing from about 30 to about 85 percent by weight of methyl enebis(phenyl isocyanate) with the remainder of the mixture comprising the polymethylene polyphenyl polyisocyanates of functionality higher than 2. Preferred polyisocyanates for flexible polyurethane foam synthesis are toluene diisocyanates including, without limitation, 2,4-toluene diisocyanate, 2,6- toluene diisocyanate, and mixtures thereof.

Typical polyols used in the manufacture of rigid polyurethane foams include, but are not limited to, aromatic amino-based polyether polyols such as those based on mixtures of 2,4- and 2,6-toluenediamine condensed with ethylene oxide and/or propylene oxide. These polyols find utility in pour-in-place molded foams. Another example is aromatic alkylamino-based polyether polyols such as those based on ethoxylated and/or propoxylated aminoethylated nonylphenol derivatives. These polyols generally find utility in spray applied polyurethane foams. Another example is sucrose-based polyols such as those based on sucrose derivatives and/or mixtures of sucrose and glycerine derivatives condensed with ethylene oxide and/or propylene oxide. These polyols generally find utility in pour-in-place molded foams.

Typical polyols used in the manufacture of flexible polyurethane foams include, but are not limited to, those based on glycerol, ethylene glycol, trimethylolpropane, ethylene diamine, pentaerythritol, and the like condensed with ethylene oxide, propylene oxide, butylene oxide, and the like. These are generally referred to as "polyether polyols". Another example is the graft copolymer polyols, which include, but are not limited to, conventional polyether polyols with vinyl polymer grafted to the polyether polyol chain. Yet another example is polyurea modified polyols which consist of conventional polyether polyols with polyurea particles dispersed in the polyol. Examples of polyols used in polyurethane modified polyisocyanurate foams include, but are not limited to, aromatic polyester polyols such as those based on complex mixtures of phthalate-type or terephthalate-type esters formed from polyols such as ethylene glycol, diethylene glycol, or propylene glycol. These polyols are used in rigid laminated boardstock, and may be blended with other types of polyols such as sucrose-based polyols, and used in polyurethane foam applications.

Catalysts used in the manufacture of polyurethane foams are typically tertiary amines including, but not limited to, N-alkylmorpholines, N-alkylalkanolamines, N,N-dialkylcyclohexylamines, and alkylamines where the alkyl groups are methyl, ethyl, propyl, butyl and the like and isomeric forms thereof, as well as heterocyclic amines. Typical, but not limiting, examples are triethylenediamine, tetramethylethylenediamine, bis(2-dimethylaminoethyl)ether, triethylamine, tripropylamine, tributylamine, triamylamine, pyridine, quinoline, dimethylpiperazine, piperazine, N,N-dimethylcyclohexylamine, N-ethylmorpholine, 2-methylpiperazine, N,N-dimethylethanolamine, tetramethylpropanediamine, methyltri ethyl enediamine, and mixtures thereof.

Optionally, non-amine polyurethane catalysts are used. Typical of such catalysts are organometallic compounds of lead, tin, titanium, antimony, cobalt, aluminum, mercury, zinc, nickel, copper, manganese, zirconium, and mixtures thereof. Exemplary catalysts include, without limitation, lead 2-ethylhexoate, lead benzoate, ferric chloride, antimony trichloride, and antimony glycolate. A preferred organo-tin class includes the stannous salts of carboxylic acids such as stannous octoate, stannous 2-ethylhexoate, stannous laurate, and the like, as well as dialkyl tin salts of carboxylic acids such as dibutyl tin diacetate, dibutyl tin dilaurate, dioctyl tin diacetate, and the like.

In the preparation of polyisocyanurate foams, trimerization catalysts are used for the purpose of converting the blends in conjunction with excess A component to polyisocyanurate-polyurethane foams. The trimerization catalysts employed can be any catalyst known to one skilled in the art including, but not limited to, glycine salts and tertiary amine trimerization catalysts, alkali metal carboxylic acid salts, and mixtures thereof. Preferred species within the classes are potassium acetate, potassium octoate, and N-(2-hydroxy-5-nonylphenol)methyl-N-methylglycinate.

Dispersing agents, cell stabilizers, and surfactants may be incorporated into the blowing agent mixture. Surfactants, better known as silicone oils, are added to serve as cell stabilizers. Some representative materials are sold under the names of DC- 193, B-8404, and L-5340 which are, generally, polysiloxane polyoxyalkylene block co- polymers such as those disclosed in U.S. Patent Nos. 2,834,748, 2,917,480, and 2,846,458.

Other optional additives for the blowing agent mixture may include flame retardants such as tris(2-chloroethyl)phosphate, tris(2-chloropropyl)phosphate, tris(2,3-dibromopropyl)phosphate, tris(l ,3-dichloropropyl)phosphate, diammonium phosphate, various halogenated aromatic compounds, antimony oxide, aluminum trihydrate, polyvinyl chloride, and the like.

Also included in the mixture are blowing agents. Generally speaking, the amount of blowing agent present in the blended mixture is dictated by the desired foam densities of the final polyurethane or polyisocyanurate foams products. The polyurethane foams produced can vary in density from about 0.5 pound per cubic foot to about 40 pounds per cubic foot, preferably from about 1.0 to about 20.0 pounds per cubic foot, and most preferably from about 1.5 to about 6.0 pounds per cubic foot for rigid polyurethane foams and from about 1.0 to about 4.0 pounds per cubic foot for flexible foams. The density obtained is a function of how much of the blowing agent, or blowing agent mixture, is present in the A and/or B components, or that is added at the time the foam is prepared.

Hydrocarbons containing from 2 to 6 carbon atoms may be used as blowing agent for rigid polyurethane and polyisocyanurate foams. Suitable hydrocarbons include, but are not limited to propane, butane, isobutane, n-pentane, isopentane, cyclopentane, n-hexane, isohexane and mixtures thereof. Hydrocarbons containing 5 carbon atoms are preferred, e.g., n-pentane, isopentane and cyclopentane. Hydrocarbon blowing agents are known materials that are commercially available and are used in various grades ranging in purity from 75% (nominal) to 99%. For the purposes of the present invention the components defined as n-pentane, isopentane, cyclopentane, n-hexane and isohexane refer to all such commercial grades of material.

Other blowing agents known for the production of rigid polyurethane foam can be used as the minor physical blowing agent. Examples of these include air, nitrogen, carbon dioxide, alkenes, chlorofiuorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons and water. Representative alkenes include 1-pentene. Representative chlorofiuorocarbons include trichlorofluoromethane (CFC-11) and dichlorodifluoromethane (CFC-12). Representative hydrochlorofluorocarbons include chlorodifluoromethane (HCFC-22), 1,1-dichloro-l-fluoroethane (HCFC-141b), l-chloro-l,l-difluoroethane (HCFC-142b) and l-chloro-l,2,2,2-tetrafluoroethane (HCFC-124). Representative hydrofluorocarbons include 1,1-difluoroethane (HFC-152a), 1,1,1 -trifluoroethane (HFC-143a), 1,1,1,2-tetrafluoroethane (HFC-134a), pentafluoroethane (HFC-125), isomers of hexafluoropropane (HFC-236), isomers of heptafluoropropane (HFC-227), 1,1,1,3,3-pentafluorobutane (HFC-365 mfc) and 1,1,1,4,4,4-hexafluorobutane (HFC-356mffm). Water chemically reacts with the isocyanate under foam forming conditions to liberate carbon dioxide, which acts as an auxiliary-blowing agent. Water is generally added in an amount up to about 3 weight percent based on the total weight of the B-side.

The HFC-245fa component of the invention is a known material and can be prepared by methods known in the art such as disclosed in World Patent Publication Nos. WO 94/14736, WO 94/ 29251 and WO 94/29252 and in U.S. Patent No. 5,574,192.

In the method of the invention, the HFC-245fa component is preferably added to the other B-side components in a blend tank and the solution is mixed in any manner known in the art until homogeneous. The HFC-245fa component preferably is added prior to the hydrocarbon to aid its miscibility in the polyols. Alternatively, the HFC-245fa may be added as a third stream at the foaming head in the foam apparatus. EXAMPLES

The invention is further illustrated by the following example, in which parts or percentages are by weight unless otherwise specified. The following materials were used in the example.

Polyol Blend: A commercially available polyester polyol with an OH number of 240.

Isopentane: 2-methylbutane commercially available from Phillips 66 Company as Borger Isopentane.

HFC-245fa: 1,1,1,3,3-pentafluoropropane commercially available from AlliedSignal.

Flame retardant A: An alkyl phosphate solution commercially available from Akzo Nobel Chemicals Inc.

Surfactant A: A polysiloxane polyether copolymer commericially available from Goldschmidt.

Catalyst A: An inorganic potassium based amine commercially available from

Air Products.

Catalyst B: A trimerization catalyst commercially available from Air Products.

Example 1

In this example, rigid polyisocyanurate foams were prepared in a commercial manufacturing facility using the formulation shown in Table 1. Two experiments were conducted. Experiment 1 used isopentane as a blowing agent with a traditional flame retardant. The second experiment was conducted using isopentane as the blowing agent and the addition of 3% 1,1,1,3,3-pentafluoropropane. TABLE 1

This example demonstrates that the addition of 3% 1,1,1,3,3- pentafluoropropane suφrisingly resulted in a near 70% improvement in the flammability characteristics of the foam.

Claims

What is claimed is:

1. A method of preparing a foam composition based on isocyanate which comprises reacting and foaming a mixture comprising:

(a) a polyisocyanate; and (b) a polyol; in the presence of

(c) a blowing agent comprising at least one C₂-C₆ hydrocarbon;

(d) a catalyst;

(e) a flame suppressing amount of 1,1,1,3,3-pentafluoropropane; and

(f) optionally one or more compounds selected from the group consisting of fire retardant, surfactant, colorant, auxiliary blowing agent, dispersing agent and cell stabilizer.

2. The method of claim 1 wherein the 1,1,1,3,3-pentafluoropropane is present in an amount of from about 1 to about 50 weight percent based on the total amount of (b)-(d).

3. The method of claim 1 wherein the 1,1,1,3 ,3-pentafluoropropane is present in an amount of from about 1 to about 19 weight percent based on the total amount of (b)-(d).

4. The method of claim 1 wherein the 1,1,1,3,3-pentafluoropropane is present in an amount of from about 1 to about 8 weight percent based on the total amount of (b)-(d).

5. The method of claim 1 wherein the at least one C₂-C₆ hydrocarbon is selected from the group consisting of n-pentane, isopentane and cyclopentane.

6. The method of claim 5 wherein the at least one C₂-C₆ hydrocarbon is isopentane.

7. The method of claim 2 wherein the at least one C₂-C₆ hydrocarbon is selected from the group consisting of n-pentane, isopentane and cyclopentane.

8. The method of claim 7 wherein the at least one C₂-C₆ hydrocarbon is isopentane.

9. The method of claim 3 wherein the at least one C₂-C₆ hydrocarbon is selected from the group consisting of n-pentane, isopentane and cyclopentane.

10. The method of claim 9 wherein the at least one C₂-C₆ hydrocarbon is isopentane.

11. The method of claim 4 wherein the at least one C₂-C₆ hydrocarbon is selected from the group consisting of n-pentane, isopentane and cyclopentane.

12. The method of claim 11 wherein the at least one C₂-C₆ hydrocarbon is isopentane.

13. A closed cell foam prepared by foaming a polyisocyanate or polyisocyanurate in the presence of a blowing agent comprising a C₂-C₆ hydrocarbon and a flame suppressing amount of 1,1,1,3,3-pentafluoropropane.

14. The closed cell foam of claim 13 wherein the amount of 1,1,1,3,3- pentafluoropropane is from about 1 to about 19 weight percent based on the total amount of blowing agent.

15. The closed cell foam of claim 13 wherein the amount of 1,1,1,3,3- pentafluoropropane is from about 1 to about 8 weight percent based on the total amount of blowing agent.

16. The closed cell foam of claim 13 wherein the C₂-C₆ hydrocarbon is selected from the group consisting of n-pentane, isopentane and cyclopentane.

17. The closed cell foam of claim 14 wherein the C₂-C₆ hydrocarbon is isopentane.

18. A blowing agent composition comprising a C₂-C₆ hydrocarbon and a flame suppressing amount of 1 , 1 , 1 ,3 ,3 -pentafluoropropane.

19. The blowing agent composition of claim 18 wherein the amount of 1,1,1,3,3- pentafluoropropane is from about 1 to about 19 weight percent based on the total amount of blowing agent.

20. The blowing agent composition of claim 18 wherein the amount of 1,1, 1,3,3- pentafluoropropane is from about 1 to about 8 weight percent based on the total amount of blowing agent.

21. The blowing agent composition of claim 18 wherein the C₂-C₆ hydrocarbon is selected from the group consisting of n-pentane, isopentane and cyclopentane.

22. The blowing agent composition of claim 21 wherein the C₂-C₆ hydrocarbon is isopentane.