Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2000-12-05
2002-04-16
Foelak, Morton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C428S095000, C521S067000, C521S133000, C521S159000
Reexamination Certificate
active
06372810
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to polyurethane foam. This invention particularly relates to polyurethane foam useful with and for preparing carpet underlay and attached cushion carpets.
It is known in the art of preparing textile articles, such as carpets, to use polyurethanes as backings in various forms. For example, U.S. Pat. No. 4,296,159 to Jenkines, et al., discloses preparing a tufted or woven article having a unitary backing prepared by applying a polyurethane forming composition to the underside of the tufted or woven article. A different form of polyurethane backing is disclosed in U.S. Pat. No. 5,102,714 to Mobley, et al. wherein the polyurethane backing is a tacky adhesive. It is also known to use polyurethane foam as a cushioning textile backing, as in, for example, U.S. Pat. No. 4,853,280.
There are several properties of polyurethane foams which are important for determining their usefulness in carpet applications. These properties include but are not limited to resiliency, dimensional stability, and cost. Cost is a very important property because of the highly competitive nature of the carpet industry. However, if a carpet does not properly install or rolls up after installation, or if that carpet is unpleasant to walk on due to poor resilience or dimensional stability of the attached or separate polyurethane pads, the carpet is not desirable to purchasers. Thus, there is a substantial body of art relating to preparing polyurethane foams useful for carpet applications wherein the polyurethane foams have good resiliency and dimensional stability and can be prepared at low cost.
One means of preparing polyurethane foams at a lower cost is to reduce the density of the polyurethane foam. Polyurethane foams are generally prepared by admixing an A component, a polyisocyanate, with a B component, an active hydrogen containing material, wherein a gas is either mechanically introduced or produced chemically forming bubbles which form a cell-like structure in the cured polyurethane. The process of introducing the bubbles is known as blowing the formulation. The greater the amount of gas introduced Into a polyurethane formulation, the lower the density of the resultant foam produced therewith. But with polyurethane foams generally and with polyurethane foams used in carpet applications in particular, reducing foam density can also decrease or reduce the properties of the polyurethane foam which can make it a desirable material for use in carpet applications. Therefore, it would be desirable In the art of preparing polyurethane foam for carpet applications to prepare such foam with a substantially lower density than conventional polyurethane carpet foams and yet retain the desirable properties of conventional polyurethane foams.
SUMMARY OF THE INVENTION
In one aspect, the present invention is, in a process for preparing a polyurethane foam pad for use as either an attached carpet cushion or a detached carpet underlay wherein a polyurethane formulation, including a polyisocyanate, is admixed using a frother, the improvement comprising including in the polyurethane formulation from about 0.5 to about 3 parts water per hundred parts of polyol, from about 0.01 to about 3.5 parts urethane catalyst per hundred parts of polyol, and from 1 to 2 parts surfactant per hundred parts of polyol under reaction conditions such the foam is both frothed and chemically blown.
In another aspect the present invention is a polyurethane foam prepared by a process wherein a polyurethane foam formulation is both frothed and chemically blown.
In still another aspect, the present invention is a polyurethane formulation useful for preparing polyurethane foams comprising a polyisocyanate, a polyol, from about 0.5 to about 3 parts water per hundred parts of polyol, from about 0.01 to about 3.5 parts urethane catalyst per hundred parts of polyol, and from 1 to 2 parts surfactant per hundred parts of polyol.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In one embodiment, the present invention is a polyurethane foam pad integral to a polyurethane backed textile, known as an attached cushion carpet. Preferably the polyurethane backed textile is a carpet or carpet tile having at least one polyurethane foam layer. This application of a polyurethane layer in a carpet is disclosed in, for example, U.S. Pat. No. 4,853,054, to Turner, et al., which is incorporated herein by reference, and U.S. Pat. No. 5,104,693 to Jenkines, et al., also incorporated herein by reference.
In another embodiment, the present invention is a polyurethane foam for use as a detached carpet underlay. Detached carpet underlays are prepared in a manner similar to attached cushion carpet except that the polyurethane foam is applied to a woven polypropylene substrate. After the polyurethane foam has cured, the underlay can be used as supplementary cushioning to attached cushion carpets or as a cushioning support for unpadded carpets.
The polyurethane foams of the present invention are similar to conventionally prepared foams except that they are prepared from formulations having high levels of catalyst, surfactant and water. The high level of water causes a chemical blowing of the foam when the water reacts with a polyisocyanate component of a polyurethane formulation of the present invention. The combination of the mechanical blowing, also called frothing, and chemical blowing from the reaction of a polyisocyanate and water results in polyurethane foam having lower densities than those conventionally used for carpet backings an carpet underlays. The polyurethane foams so produced have sufficiently low densities to be less expensive to produce than conventional polyurethane foams for carpet applications, yet the foams have sufficient resiliency and dimensional stability to be desirable for use in carpet applications.
The low cost polyurethanes foams of the present invention have desirable physical properties for carpet applications. This results from she synergistic combination of mechanical blowing and chemical blowing. This is made possible by the inclusion of high levels of catalyst, water and surfactant in the formulations used to prepare the foams. The foam formulations used to prepare the foams of the present invention have from about 0.5 to about 3 parts water per hundred parts polyol, preferably from about 0.75 to about 2.75 parts water per hundred parts polyol, and more preferably from about 1.5 to about 2.5 parts water per hundred parts polyol. The formulations of the present invention also include from about 0.01 to about 3.5 parts urethane catalyst per hundred parts polyol, and from 1 to 2 parts surfactant per hundred parts polyol.
The resultant polyurethane foams have densities of from about 2 to about 55 pounds per cubic foot, preferably from about 3 to about 30, more preferably from about 8 to about 18, and even more preferably from about 8 to about 14 pounds per cubic foot. Most preferably, the resultant foams have a density of less than about 10 pounds per cubic foot.
An example of the present invention is a polyurethane foam underlay prepared from a formulation such as those disclosed by U.S. Pat. No. 5,104,693 to Jenkines but additionally including from about 0.5 to about 3 parts water per hundred parts of polyol, from about 0.01 to about 3.5 parts urethane catalyst per hundred parts of polyol, and from 1 to 2 part surfactant per hundred parts of polyol. In formulations of this type, the polyol component can be at least one isocyanate reactive material having an average equivalent weight of about 1,000 to about 5,000. The polyisocyanate can be any polyisocyanate in an amount to provide an isocyanate index of about 90 to about 130, wherein at least 30 percent by weight of the polyisocyanate is a soft segment prepolymer which is the reaction product of a stoichiometric excess of MDI or an MDI derivative and an isocyanate reactive organic polymer having an equivalent weight from about 500 to about 5,000, the prepolymer having an isocyanate group content of about 10 to about 30 percent by weight. The underlay
Jenkines Randall C.
Kazmierski Daniel W.
Foelak Morton
The Dow Chemical Company
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