Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2002-04-26
2003-11-25
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...
C521S112000, C521S130000, C521S131000, C521S174000
Reexamination Certificate
active
06653359
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to silicone surfactants for use in inert gas blown polyurethane foams. More particularly, the present invention relates to silicone surfactants having dimethyl siloxane backbones with attached polyalkylene oxide polyether pendant groups that preferably are designed to have flame-retardant characteristics for use in flame retardant (FR) foam compositions.
2. Description of Relited Art
Historically, numerous grades of polyurethane foams were blown with chlorofluorocarbon (CFC) based blowing agents to reduce foam density, control foam firmness, and cool the foams to minimize discoloration, degradation, and possible foam ignition problems. Worldwide issues regarding ozone depletion in connection with certain CFCs has led to the Montreal Protocol, which phases out the use of CFCs.
Thus, the polyurethane foam industry has tried to achieve the same foam grades and quality produced using alternate blowing agents (ABAs). Many different ABAs have been evaluated, including HCFC-141b, HFC-134a, HFC-22, alkyl carbonates, and pentane. In flexible slabstock foams, in particular, other approaches have been taken, including the use of acetone, methylene chloride, carbon tetrachloride, trichloroethane, and pentanes as ABAs. While functional, these approaches also have problems, including flammability, volatile organic compound (VOC) limitations, and toxicity (for the chlorocarbons).
More recently, technology has been developed that entails the use of supplemental added inert gases, e.g., CO
2
, as part of the blowing agent for flexible polyurethane foams, which is described in European Patent Publication No. 0 645 226 A2 (see also U.S. Pat. Nos. 5,620,710; 5,629,027; and 5,639,483; and U.S. Pat. Nos. Re. 37,012; 37,075; and 37115); U.S. Pat. No. 6,005,014; U.S. Pat. No. 6,147,133; and U.S. Pat. No. 6,326,413. This technology will hereinafter be referred to as “Dissolved Gas Technology”. Auxiliary gas is added to the system as a blowing agent and is used in conjunction with the CO
2
generated from the reaction of isocyanate with water. More particularly, these patents disclose a process and a system for the continuous manufacture of polymeric foams. Reactive chemical components and additives comprising a low boiling blowing agent are mixed under pressure; the mixture is then frothed before chemical reaction takes place by feeding the mixture through a pressure equalizing and frothing device having a pressure-drop zone, of varying design, with eventual discharge of the froth onto a moving substrate.
U.S. Pat. Nos. 4,814,409 and 4,855,329 disclose certain polysiloxane-polyoxyalkylene compositions and their use as stabilizers in the manufacture of polyether polyurethane foam. These compositions have a polysiloxane chain substituted with at least two types of polyoxyalkylene polymers as pendants from the silicon atoms of the polysiloxane. The distinctive feature of these compositions is the specific selection of polyoxyalkylene polymers. Preferably, the polyoxyalkylene polymer pendants are provided as at least three different polyoxyalkylene polymers. One of these polyoxyalkylene polymers is composed of only oxypropylene units. This polyoxypropylene has an average molecular weight from about 130 to about 1200 excluding link and endcap. The other polyoxyalkylene polymers are composed of both oxyethylene and oxypropylene units. These references teach that silicone surfactants with lower ratios of unmodified polydimethylsiloxane groups to branched siloxane groups are preferred in flame retardant foam applications. This teaching is reinforced by Weier et al. in
Proceedings of the Polyurethane
1994
Conference
, 202 (1994).
U.S. Pat. No. 5,145,879 discloses silicone surfactants having a siloxane backbone and a mixture of high and low atomic mass oxyalkylene pendant groups, these polyether pendants having average atomic masses of 1500-6000 and 300-750 respectively. The surfactants operate in polyurethane foam compositions to provide stable foams over a range of surfactant concentrations while still producing product foams having relatively constant breathability. Also disclosed are polyurethane foam compositions which include the surfactants, a method of making polyurethane foam using the surfactants, and polyurethane foam made by the method.
U.S. Pat. No. 5,525,640 discloses that the use of inert gases as an auxiliary blowing agent in flexible polyurethane foams places unexpected requirements on the composition of the silicone surfactants used in such foams and typical silicone polyalkylene oxide polyether copolymer comb-type surfactants containing greater than about 37% ethylene oxide in the polyoxyalkylene-polysiloxane copolymer cause large cells when added inert gas is used as the blowing agent.
U.S. Pat. No. 5,789,454 discloses a method of using inert gas as an auxiliary blowing agent in the production of flexible polyurethane foams, in the presence of a blend of a silicone surfactant stabilizer and a second silicone compound. The disclosed method provides better stabilization of the foams made by such processes. Also disclosed are foam formulations containing such blends.
The disclosures of the foregoing are incorporated herein by reference in their entirety.
SUMMARY OF THE INVENTION
Previously, it was expected that all silicone surfactants currently used in the preparation of conventional slabstock foams would function well in stabilizing Dissolved Gas Technology foams. This would thus lead to fine cell structure foam prepared via all inert gas blowing. U.S. Pat. Nos. 5,525,640 and 5,789,454 taught that specific classes of surfactant structures are more applicable to Dissolved Gas Technology foaming.
It has now been discovered that other specific classes of silicone surfactants are efficient at yielding uniform low density Dissolved Gas Technology foams that exhibit good to excellent bulk foam stability and fine cell structure, particularly when lower use levels of surfactants are employed. Lower use levels of surfactants are economically desirable, but are known to exaggerate or stress any existing foam processing issues.
The present invention is directed to certain low to moderate molecular weight (hereinafter “MW”) surfactants that are comb-type FR silicone copolymers possessing no high ethylene oxide (“EO”) content branches that yield Dissolved Gas Technology foams having improved consistency as compared to other surfactant compositions.
More particularly, the present invention is directed to a method of producing a polyurethane foam comprising:
A) preparing a mixture comprising:
(1) a polyether polyol containing an average of more than two hydroxyl groups per molecule,
(2) an organic polyisocyanate,
(3) at least one catalyst for the production of polyurethane foams,
(4) water, and
(5) a surfactant;
wherein the surfactant comprises a silicone/polyether composition of the formula:
R—Si(CH
3
)
2
O—{Si(CH
3
)
2
O—}
x
—{SiCH
3
R
1
O—}
a
—{SiCH
3
R
2
O—}
b
—{SiCH
3
R
3
O—}
c
—{SiCH
3
R
4
O—}
d
—Si(CH
3
)
2
—R;
or the formula:
R—Si(CH
3
)
2
O—{SiCH
3
RO}
m
—(SiCH
3
{O—(SCH
3
RO)
m
—Si(CH
3
)
2
R}O)
n
—{SiCH
3
RO}
m
—Si(CH
3
)
2
—R
wherein:
R
1
, R
2
, and R
3
are polyalkylene oxide polyethers of the formula
—B—C
n
H
2n
O—(C
2
H
4
O)
e
—(C
3
H
6
O)
f(C
4
H
8
O)
g
Z,
where
R
1
has a blend average molecular weight in the range of from about 3000 to about 6000 grams/mole and ethylene oxide is from about 20 to about 60 weight percent of the alkylene oxide content of the polyether;
R
2
has a blend average molecular weight in the range of from about 800 to about 2900 and ethylene oxide is from about 20 to about 60 weight percent of the alkylene oxide content of the polyether;
R
3
has a blend average molecular weight in the range of from about 130 to about 800 grams/mole and ethylene oxide is from 0 to about 75 weight percent of the alkylene oxide content of the polyether;
R
4
is an substituted or unsubstituted alk
Hilker Brian L.
Lawler Lee F.
McVey Susan B.
Cooney Jr. John M.
Dilworth Michael P.
LandOfFree
Fire retardant silicone surfactants for use in inert gas... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fire retardant silicone surfactants for use in inert gas..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fire retardant silicone surfactants for use in inert gas... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3117129