This invention relates to novel foam modifiers which can be used to prepare flexible foams. These novel foam modifiers provide improved processability and improved properties of the resultant flexible foams. The present invention also relates to the process of preparing these flexible foams and to the resultant foams.
Slabstock foam facilities today need to efficiently produce quality foams of widely varying types, grades and performance characteristics. For a single facility to have this diversity in production, it is typically necessary to use several different polyols, surfactants, catalysts, processing aids, special additives and polyisocyanates. Obviously, each different component requires a separate storage and delivery system, which results in increased equipment cost and complexity. It also increases the possibility of cross contamination between components and of formulating errors.
The preparation of various types and grades of flexible polyurethane foams is often improved or made easier when the isocyanate-reactive mixture comprises minor levels of one or more low molecular weight extenders, crosslinkers or compatibilizers and minor levels of one or more high molecular weight polyols. These constituents can have a favorable effect on foam processing, but often have a detrimental effect on certain foam properties such as reduced porosity and increased compression sets. The reduction in foam porosity becomes particularly disadvantageous for flexible slabstock foams made at isocyanate indexes near 100 and above. A single modifier blend offering improvements in the production and properties of various types and grades of slabstock foam would be a valued addition to the industry.
Compositions containing high and low MW polyols that are resistant to phase separation are known and described in U.S. Pat. No. 3,993,576. These compositions comprise (A) an insoluble mixture that is susceptible to phase separation which comprises (1) from about 50 to about 95% by weight of a high molecular weight polyol, and (2) from about 5 to about 50% by weight of a low molecular weight polyol; and (B) a solubilizer for (A) which corresponds to one of two formulas, that is present in a small but effective quantity such that the entire composition is phase stable. The high molecular weight polyols suitable are those wherein a majority of the oxyalkylene groups are not oxyethylene groups. The solubilizer comprises propylene glycol derivatives and/or butylene glycol derivatives.
U.S. Pat. No. 4,385,133 describes a specific combination of polyols and an extender which results in a homogeneous, single phase blend of the polyols and extender. In particular, the polyol component is a mixture comprising (a) a polyoxypropylene polyoxyethylene polyol having an average functionality of from 2 to 4, a molecular weight of about 3,000 to about 10,000 and containing at least 23% by weight of ethylene oxide residues, and (b) a polyoxypropylene polyoxyethylene polyol having an average functionality of from 2 to 4, a molecular weight of about 750 to about 2,000 and containing at least 45% of ethylene oxide. The proportions by weight of (a) and (b) are adjusted such that the aliphatic glycol extender is completely miscible. This combination is disclosed as being useful for the preparation of polyurethanes, particularly when using a RIM (reaction injection molding) process.
Foam processing aids for the production of conventional polyurethane slabstock foam at low isocyanate indices using the free-rise process are described in U.S. Pat. No. 4,950,694. The foam processing aids assist in avoiding/preventing foam splitting without destroying the open cell structure and high porosity characteristic of conventional, flexible polyurethane foam, and particularly soft, low density foam. These foam processing aids comprise at least one crosslinking/extending agent, and possibly a cell opening agent which is preferably a polyethylene oxide monol and/or polyol. Suitable crosslinking/extending agents have equivalents weights of less than about 200, and suitable monols and polyols for the processing aid have ethylene oxide contents of greater than 50% by weight.
U.S. Pat. Nos. 4,863,976 and 4,929,646 disclose flexible polyurethane foams, a method for making these flexible polyurethane foams and suitable active hydrogen containing compositions. These flexible foams comprise (a) at least one relatively high MW polyester polyol or polyether polyol containing at least 50 wt. % of oxypropylene units, an amine-terminated derivative of such polyester or polyether polyol or mixture thereof, (b) an effective amount of a blowing agent, (c) a high functionality polyether polyol based on an initiator or initiator mixture having at least about 4.0 active hydrogens per molecule, and a molecular weight of at least about 5000 and containing at least about 50 wt. % of oxyethylene units and sufficient oxypropylene units to render it compatible with component (a) at the relative proportions thereof present in the reaction mixture, in an amount sufficient to provide a measurable increase in the proportion of open cells in the foam as compared with a similar foam prepared in the absence of high functionality polyether polyol, and (d) at least one polyisocyanate.
There is a need for a single additive polyol that would be capable of improving the processing and grade latitude of various types of flexible slabstock foams and which would avoid losses in foam properties such as reduced porosity and increased compression sets. A single additive polyol could improve production efficiency by avoiding the need to store and deliver multiple components during the slabstock foam process. The present invention provides a foam modifier for the efficient production of flexible slabstock foams.
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