Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2000-12-01
2002-09-24
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...
C521S155000, C521S170000, C521S174000, C524S762000, C524S765000, C524S773000
Reexamination Certificate
active
06455603
ABSTRACT:
The resent invention relates to polymer polyols and a process for the preparation thereof.
Polymer polyols suitable for the preparation of polyurethane foams and elastomers are well known and are widely used on a commercial scale. Polyurethane foams made from polymer polyols have a wide variety of uses. The two major types of polyurethane foams are slabstock and molded foam. Polyurethane slabstock foams are used in carpet, furniture and bedding applications. Molded polyurethane foams are used in the automotive industry for a variety of applications.
Polymer polyols are produced by polymerizing one or more ethylenically unsaturated monomers dissolved or dispersed in a polyol in the presence of a free radical catalyst to form; stable dispersion of polymer particles in the polyol. Initially, polymer polyols producing polyurethane foams having higher load-bearing properties than those produced from unmodified polyols were prepared using acrylonitrile monomer; however, many of these polymer polyols had undesirably high viscosity.
Presently, polyurethane foams having high load-bearing properties are predominantly produced using polymer polyols which are prepared using a high styrene content monomer mixture (for example, 65 to 75 percent styrene). However, polymer polyols produce from such high styrene monomer mixture often do not satisfy the ever-increasing industry needs, including acceptable viscosity, strict stability requirements and increased load-bearing properties.
Stability and low viscosity of polymer polyols are of increasing importance to polyurethane form manufacturers due to the development of sophisticated, high speed and large volume equipment and systems for handling, mixing and reacting polyurethane-forming ingredients. Polymer polyols must meet certain minimum polymer particle size requirements to avoid filters, pumps and other parts of such foam processing equipment becoming plugged or fouled in relatively short periods of time.
Numerous attempts have been made to produce polymer polyols which will meet foam processing and load-bearing properties required by the polyurethane foam industry.
International application PCT/EP95/04149 (Fogg) describes stable, relatively low viscosity polymer polyols prepared by free radical polymerization of a composition comprising a polyol; a preformed stabilizer which is the reaction production of a polyol, a precursor stabilizer obtainable by reacting a silicon compound with a polyether polyol, at least one ethylenically unsaturated monomer and a free radical polymerization initiator; at least one ethylenically unsaturated monomer; a free radical polymerization initiator; and, optionally, a chain transfer agent.
U.S. Pat. No. 5,196,476 (Simroth) describes: (a) a high potency preformed stabilizer; (b) the use of same in the manufacture of polymer polyols having high solids content, lower viscosity and excellent product stability; and (c) a polyurethane made using such polymer polyol. The preformed stabilizer is the free radical polymerization product of at least one free radically polymerizable ethylenically unsaturated monomer and at least one polyhydric alcohol adduct comprising a polyhydric alcohol residue and a residue of a compound having fumaric or maleic type unsaturation.
U.S. Pat. No. 5,364,906 (Critchfield et al.) describes a method for producing a stable, low viscosity polymer polyol via a modified seed method by the steps of (1) producing a first reaction product by polymerizing a first feed in a first continuous reactor in the presence of a initiator, the first feed comprising less than 50 weight percent of a total monomer proportion in at least 50 weight percent of a total base polyol proportion, optionally in the present of a precursor stabilizer which is prepared by reacting a polyol with maleic anhydride; and (2) producing a second reaction product by polymerizing a second feed in a continuous reactor in the presence of an initiator, the second feed comprising (a) the first reaction product, (b) at least 50 weight percent of the total monomer proportion, and (c) any balance of the base polyol proportion.
European Patent No. 0 162 589 B1 (Cloetens et al.) describes a nonaqueous dispersion stabilizer which is the reaction product of a polyether polyol having an average molecular weight greater than 400 and a hydroxyl number in the range of 20 to 280 with silicon atom containing compound having at least one olefinically unsaturated functional group and at least one functional group attached to the silicon atom which is reactable with the hydroxyl groups on the polyether polyol.
U.S. Pat. No. 4,661,531 (Davis et al.) describes a process for preparing a polymer polyol in a continuous process wherein the use of a chain transfer agent contributes to products having uniform viscosity.
Additional prior art of interest include U.S. Pat. No. Re. 32,733 (Simroth et al.); U.S. Pat. No. 3,931,092 (Ramlow et al.); U.S. Pat. No. 4,014,846 (Ramlow et al.); U.S. Pat. No. 4,093,573 (Ramlow et al.); U.S. Pat. No. 4,148,840 (Shah); U.S. Pat. No. 4,172,825 (Sho k et al.); U.S. Pat. No. 4,342,840 (Kozawa et al.); U.S. Pat. No. 4,390,645 (Hoffman et al.); U.S. Pat. No. 5,394,491 (Hoffman); U.S. Pat. No. 4,454,255 (Ramlow et al.); U.S. Pat. No. 4,458,038 (Ramlow et al); and U.S. Pat. No. 4,745,153 (Hoffman).
Although there has been progress in reduction of viscosity and increase in solids content of polymer polyols, there is still a need for polymer polyols having improved processing and load-bearing properties and for alternate methods for making such polymer polyols.
The present invention is directed to a low fouling process for the production of polymer polyol having a Brookfield Viscosity that is equal to or less than (a e
[(0.051)(b)]
) where “a” is the viscosity of the carrier polyol and “b” is the [(weight fraction of solids)(100)]. Such a process comprises the use of a free radical initiator comprising at least a first active peroxide either alone or in conjunction with additional initiators which may be a different active peroxide or it may be an azo compound. When such additional initiators are also active peroxide, such additional initiators have a half life greater than that of the first active peroxide. By half life is meant the time necessary to reduce the initiator concentration by one half. The level of the first active peroxide is equal to or less than 0.6 weight percent (based on the total monomer content). When the first active peroxide is used in conjunction with additional initiators, the total weight percent (based on total monomer content) of the initiators is not greater than 1.0 weight percent with the proviso that, in any event, the level of the first active peroxide is equal to or less than 0.6 weight percent (based on the total monomer content). The invention is also directed to polymer polyols produced by such process and to their use in the production of foams and the foams produced thereby. The polymer polyols so produced have desirable properties including a high polymer content and product stability.
In one aspect, the present invention concerns a process for the preparation of a polymer polyol which comprises providing (a) a polyol; (b) a preformed stabilizer; (c) at least one ethylenically unsaturated monomer; (d) a free radical polymerization initiator comprising at least a first active peroxide at a level equal to or less than 0.6 weight percent based on total monomer content; and (e) a chain transfer agent to a reaction zone maintained at a temperature, preferably 120° C. to 140° C., sufficient to initiate a free radical polymerization, and under sufficient pressure to maintain only liquid phases in the reaction zone, for a period of time sufficient to react a major portion of the ethylenically unsaturated monomer to form a heterogenous mixture containing the polymer polyol and recovering same from this heterogenous mixture.
In another aspect, the present invention concerns a polymer polyol composition which has a polymer content of 30 to 60 weight percent, based on total weight, a
Cooney Jr. John M.
Dow Global Technologies Inc.
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