Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2001-06-28
2003-05-06
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...
C521S170000, C521S172000, C521S173000
Reexamination Certificate
active
06559196
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to polyurethane foams. More particularly, this invention relates to tough, fire resistant, temperature resistant polyurethane foams with low fogging and low outgassing.
2. Brief Description of the Prior Art
Fire resistant polyurethane foams are useful materials for a wide variety of applications, particularly in the automotive and electronic industries. Such foams preferably have densities in the range from about 10 to about 50 pounds per cubic feet (pcf). It is also important that the foams have acceptable compression set, abrasion resistance, flex resistance, and tear strength. Another important characteristic is low fogging and outgassing, which is especially desirable in automotive applications. While a number of prior art foams meet the above requirements, such as the PORON® polyurethane foams sold by Rogers Corp., Rogers, Conn., it has heretofore been difficult to impart good or excellent toughness, temperature resistance, and flame resistance to such foams, without also increasing fogging and outgassing.
One flame resistance standard often specified for automotive applications is FMVSS (Federal Motor Vehicle Safety Standard) 302.
It is known in the prior art that the fire resistance of polyurethane foams can be increased by chemical incorporation of phosphorus compounds into the foams. Thus, for example, U.S. Pat. No. 3,986,990 discloses polymerizing polyalkylene glycol alkyl polyphosphites with or without additional polyols, with selected isocyanates, thereby producing polyurethane foams in which these polyphosphites are chemically incorporated into the polyurethane network. U.S. Pat. No. 3,989,652 discloses the preparation and subsequent incorporation of polyalkylene glycol alkyl or halo-alkyl polyphosphonates into the polyurethane polymer chain by chemical bonds.
In the above prior art, the attachment is chemical via a reaction between the isocyanate and an active hydrogen which is part of the phosphorus-containing molecule. This results in incorporation of the phosphorus atom into the main polymer backbone, which leads to loss of commercially attractive properties, such as softness and resilience in flexible foams, and lack of friability in rigid foams. Susceptibility to hydrolysis is also increased for both rigid and flexible foams. These problems are so acute for flexible foams that present commercial practice is to introduce the phosphorus in a non-reactive form, e.g., as tris-(2-chloroethyl phosphate). This results in a small degree of plasticizing, but disadvantageously, the fire retardant is simply dissolved in the foam polymer, where it contributes to fogging and/or outgassing. It may also diffuse out, in which case fire retardance is lost.
The preparation of low density, flexible polyurethane flame-retardant foam compositions is also described in U.S. Pat. No. 4,022,718, which teaches the preparation of high resilience cold-cured polyurethane foams incorporating 2,3-dibromo-1,4-butenediol as a chain extender and flame-retardant component. U.S. Pat. No. 4,147,847 teaches a method of preparing flexible, flame-retardant, polyurethane foams by employing specific foam stabilizers, which reduce the required amount of normal flame-retardant additives. U.S. Pat. No. 4,162,353 teaches the preparation of flexible polyurethane foams incorporating therein a halo-substituted alkyl phosphate such as tris(2-chloroethyl)-phosphate and an unsubstituted trialkylphosphate such as triethylphosphate. U.S. Pat. No. 4,849,459 describes a flame retardant flexible polyurethane foam comprising the reaction product of a polyether polyol and a toluene diisocyanate and incorporating melamine and another flame retardant. Each of the foregoing is incorporated herein by reference.
While suitable for their intended purposes, the above-described flexible polyurethane foams do not have the requisite combinations of high temperature resistance and toughness, as reflected by tensile strength, elongation, tear strength, abrasion resistance, and/or flex resistance, in combination with flame retardance and low fogging and low outgassing. Because of these deficiencies, these prior art foams are not suitable for use in the automotive industry for example, as interior gaskets, seals, and cup holders. Consequently, there remains a need for low fogging, low outgassing polyurethane foam compositions that are flame retardant, i.e., which pass FMVSS 302 burn testing, and yet which are also temperature resistant and tough.
SUMMARY OF THE INVENTION
The above-discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by compositions for the formation of temperature resistant, tough, flame retardant polyurethane foams, comprising
a low VOC polyisocyanate component wherein the isocyanate is a low functionality isocyanate;
a low VOC active-hydrogen containing component substantially reactive with the low functionality isocyanate to form a polyurethane;
a surfactant composition; and
a catalyst component, wherein the total mass loss of the foam is less than 1% by weight as measured by ASTM E595.
The composition may furthermore optionally comprise a low VOC antioxidant composition to improve temperature resistance. Preferably, the composition further comprises a flame retardant filler, even more preferably a non-halogenated, low VOC flame retardant filler. Preferably, each of the foregoing components is low VOC, (i.e., has a low concentration of volatile organic components), and the formed foam is overprinted with a low VOC, nonfogging, UV-curable acrylic composition. Such foams pass FMVSS 302 burn testing, even in the absence of known halogenated or phosphorus-based flame retarding agents. The foams have excellent physical properties, in addition to temperature resistance, flame retardance, low fogging, and low outgassing. In particular, the foams are tough, as reflected by high tensile strengths and high elongations relative to the CFD (compressive force deflection, or “modulus”).
Because of the foregoing numerous features and advantages, the materials described herein are especially suitable for use as interior gaskets, seals, and cup holders for automotive and other electronic applications. The above discussed and other features and advantages will be appreciated and understood by those skilled in the art from the following detailed description.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A composition for the formation of a flame retardant, yet tough polyurethane foam having low outgassing and low fogging consists essentially of
a low VOC organic polyisocyanate component, wherein the polyisocyanate component is a low functionality polyisocyanate,
a low VOC active-hydrogen containing component substantially reactive with the low functionality isocyanate to form a polyurethane,
a surfactant composition for structurally stabilizing the froth produced according to step (2) below, during the period that said froth is in the liquid phase and until said froth is cured; and
a catalyst having substantial catalytic activity in the curing of said mixture.
The process of forming the foam comprises forming the above-described composition; substantially uniformly dispersing inert gas throughout the mixture by mechanical beating of the mixture to form a heat curable froth which is substantially structurally and chemically stable, but workable at ambient conditions; and curing said froth to form a cured foam.
As may be seen by reference to the related art discussed above, it has been heretofore difficult to obtain low outgassing foams that are also tough. It has furthermore been thought that high levels of flame resistance could be imparted to polyurethane foams only by use of known halogenated and phosphorus-based flame retarding agents, which contribute to fogging and outgassing problems. The inventors hereof have unexpectedly discovered that tough, low outgassing foams may be achieved by the combination of a low functionality isocyanate and low VOC components; and that such foams may be rendered highly flam
Narayan Sujatha
Simpson Scott S.
Cantor & Colburn LLP
Cooney Jr. John M.
World Properties, Inc.
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