Process for making isocyanate-based rigid foam

Details Process for making isocyanate-based rigid foam Process for making isocyanate-based rigid foam

1999-02-05

2001-07-31

Cooney, Jr., John M. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Cellular products or processes of preparing a cellular...

C521S114000, C521S116000, C521S117000, C521S130000, C521S131000, C521S172000, C521S173000, C521S176000

Reexamination Certificate

active

06268402

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to a process for making isocyanate-based rigid foams from stable polyester polyol compositions comprising a phthalic anhydride-initiated polyester polyol, a C
4
-C
6
hydrocarbon blowing agent, and a compatibilizing agent having an HLB of from about 7 to 12. The compatibilizing agent is a fatty acid or fatty alcohol ethoxylate. The blowing agent is soluble in the polyol composition. The process comprises reacting an organic polyisocyanate with the polyol composition in the presence of the blowing agent and other optional components. The process results in a rigid polyurethanelpolyisocyanurate foam which has improved dimensional stability and thermal insulation properties including improved K factors.
BACKGROUND OF THE INVENTION
Hydrocarbons are gaining wider acceptance as viable alternative blowing agents in the manufacture of rigid polyurethane foams. Due to the non-polar hydrophobic characteristic of hydrocarbons, they are only partially soluble, if not completely insoluble, in many polyols used to manufacture rigid polyurethane foams. The insolubility or poor shelf life of hydrocarbon-polyol mixtures has, to date, limited the ability of storing batches of the mixtures for use at a later time. Due to the poor solubility of hydrocarbons blowing agents in polyols, the blowing agent must be added to the polyol composition under constant agitation immediately before dispensing the foaming ingredients through a mixhead. The poor solubility of hydrocarbons also tends to lead to larger, coarser, or uneven cell structures in a resultant polyurethane foam. As is well known, the thermal conductivity of a foam generally increases with a poor cell structure. Therefore, it is critical that hydrocarbon be uniformly dispersed under constant agitation throughout the polyol mixture immediately prior to foaming in order to obtain a rigid polyurethane foam having the desired thermal insulation values.
In U.S. Pat. No. 5,391,317, Smits sought to manufacture a foam having both good dimensional stability and thermal insulation using hydrocarbons as blowing agents. This reference taught the use of a particular mixture of C
5-6
alicyclic alkanes, isopentane and n-pentane blowing agents in particular molar percents, in combination with a polyol mixture made up of an aromatic initiated polyether polyol, an aromatic polyester polyol, and a different amine-initiated polyether polyol. As the aromatic-initiated polyether polyol, Smits suggested using an alkylene oxide adduct of a phenolformaldehyde resin. The particular mixture of alicyclic and isomeric aliphatic alkane blowing agents is taught by Smits as producing a foam having good thermal insulation values.
The problem of obtaining a closed cell rigid polyurethane foam having both good dimensional stability and thermal insulation at low densities was also discussed in “An Insight Into The Characteristics of a Nucleation Catalyst I HCFC-Free Rigid Foam System” by Yoshimura et al. This publication reported the results of evaluations on a host of catalysts used in a standard polyurethane formulation to test the effects of each catalyst on the thermal insulation and dimensional stability of the foam. The standard formulation used contained 40 parts by weight of a sucrose-based polyether polyol, 30 parts by weight of an aromatic amine-initiated polyether polyol, and 30 parts by weight of an aliphatic amine-initiated polyether polyol, in a 1:1 weight ratio of aromatic to aliphatic amine-initiated polyols. This formulation was selected based upon the findings that sucrose and aromatic amine-based polyether polyols exhibited poor solubilities with cyclopentane, while aliphatic amine-based polyether polyols provided the best solubility for cyclopentane. As a result, 30 parts by weight of the aliphatic amine-initiated polyether polyol was used in the standard formulation.
Others have also tried to modify the polyol components in a polyol composition in an attempt to solubilize a hydrocarbon blowing agent in the polyol composition. In U.S. Pat. No. 5,547,998 (White et al), the level of aliphatic amine-initiated polyether polyols in a polyol composition is limited to solubilize cyclopentane in the polyol composition. When reacted with an organic isocyanate, the polyol composition, comprising an aromatic amine-initiated polyoxyalkylene polyether polyol and an aliphatic amine-initiated polyoxyalkylene polyether polyol in an amount of 10 weight percent or less by weight of the polyol composition produces a dimensionally stable rigid closed cell polyurethane foam having good thermal insulation properties.
In U.S. Pat. No. 5,648,019 (White et al), the level of aromatic polyester polyols in a polyol composition is preferably limited to 18 weight percent or less to improve the solubility of blowing agent in the polyol composition. The polyol composition is preferably reacted with an organic isocyanate to produce a rigid closed cell foam having good thermal insulation and dimensional stability.
Thus, it would be desirable to provide a polyester polyol composition which has a hydrocarbon blowing agent solubilized therein which can be used to produce dimensionally stable rigid polyurethane foam having good thermal insulation properties.
SUMMARY OF THE INVENTION
According to the present invention, a stable polyester polyol composition is provided comprising a phthalic anhydride-initiated polyester polyol, a C
4
-C
6
hydrocarbon blowing agent, and a compatibilizing agent, wherein the blowing agent is soluble in the polyol composition. The compatibilizing agent comprises an oxyethylated fatty acid or fatty alcohol having an HLB of from about 7 to about 12, preferably from about 8 to about 11, most preferably about 10. In a preferred embodiment of the present invention, the compatibilizing agent is an oxyethylated fatty acid of the general formula R
n
—COO(EO)
x
H, wherein R
n
is a C
14
to C
26
alkyl chain, EO represents an ethylene oxide unit, and x is from about 5 to about 12. In one embodiment, the compatibilizing agent comprises a C
18
-C
20
fatty acid-initiated oxyethylate having an average of about 8 ethylene oxide units per molecule. Preferably, the compatibilizing agent is present in an amount of from about 1.0 to about 25.0, more preferably 5.0 to about 15.0, most preferably 7.0 to about 10.0, parts by weight based on 100 parts by weight of the polyester polyol.
The blowing agents employed when used in association with the polyol compositions of the present invention have been found to offer lower densities, improved K factors, improved thermal insulation properties and improved dimensional stabilities over foams produced using other polyol systems. The compatibilizing agent preferably facilitates solubilizing the blowing agent in the polyol composition without sacrificing, and advantageously improving, the thermal insulation and dimensional stability of the resulting polyurethane foam. The blowing agent is preferably selected from the group of C
5
hydrocarbons, including isopentane, normal pentane, neopentane, cyclopentane and mixtures thereof. A preferred blowing agent mixture comprises a blend of isopentane and/or normal pentane and cyclopentane. In another embodiment of the present invention, the blowing agent comprises a blend of cyclopentane and isopentane, preferably in a weight ratio of about 70:30 to about 40:60. The amount of blowing agent present in the polyol composition is preferably at least about 5.0 parts by weight based on 100 parts by weight of the polyester polyol. In preferred embodiments of the invention, the amount of blowing agent in the polyol composition is from about 7 to about 30, more preferably from about 20 to about 30, most preferably from about 24 to about 27 parts by weight, based on 100 parts by weight of the polyester polyol.
There is also provided a polyisocyanate based rigid closed cell foam made by reacting an organic isocyanate with a polyol composition in the presence of a blowing agent, wherein the polyol composition comprises:
a) a phthalic anhydride-initi

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