Flexible polyurethane foam containing copper

Details Flexible polyurethane foam containing copper Flexible polyurethane foam containing copper

1999-10-19

2002-05-14

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...

C156S078000, C156S079000, C428S423100, C521S155000, C521S170000, C521S174000

Reexamination Certificate

active

06387973

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to flexible polyurethane foam containing copper, to methods of incorporating the copper into the foam and to the use of the foam in articles for alleviating discomfort experienced by people who suffer from an ailment associated with joints, limbs and muscles, such as arthritis and rheumatism.
BACKGROUND OF THE INVENTION
It is known that copper has antifungal properties. Thus, GB-A-1581586 discloses a sock having, adhered to its inner surface, a composition comprising a water-insoluble resin binder and, dispersed in the binder, a metal powder. The metal may be copper and the binder may be a polyurethane. The composition may additionally contain what is referred to as a “foaming agent” to allow foaming of the composition after its application to the sock so as to improve softness and air and moisture permeability. However, the only example given of such a foaming agent is of capsules of a vinylidine chloride/acrylonitrile copolymer which expand on heating. This will not cause the binder to foam. It is suggested that sweat fat and other substances release the metal from the resin and convert it to soluble ionic substances.
GB-A-2133287 discloses an adhesive plaster having a surface, for contact with the skin, provided with strips of adhesive and between the strips of adhesive a metal or metal alloy, e.g. copper. The copper apparently relaxes muscle spasms caused by a wide variety of diseases, including rheumatism; sweat, formed by application of the plaster, serves as an electrolyte between grains of the metallic substance and generates an electrolyte current which intrudes under the skin surface or into the muscles lying underneath.
It is known to incorporate very small amounts of copper dust, cupric oxide, cuprous oxide or copper sulphate solution into a polyurethane foam to serve as a flame retardant, as described by B. C. Levin et al in Plastics Compounding (January/February 1990), 13(1), 58-62. In particular, cuprous oxide is added to the polyol from which the polyurethane foam is prepared in an amount of 0.072%.
It is also known to incorporate, into polyurethane foam, small amounts of copper in the form of copper salts and complexes thereof to achieve certain effects, e.g. as a catalyst during the production of polyurethane and as a smoke suppressant in flame retardant foams; see U.S. Pat. No. 4,263,411, which recommends the incorporation, in-situ, into the foam of the copper salt or complex so as to provide about 0.05 to about 3 parts (based on metallic copper) per 100 parts by weight of the polyol used to prepare the foam.
However, copper and its compounds display amphoteric properties. Thus, in conventional flexible polyurethane foams, the addition of copper powder can lead to retardation of foam cure, even at relatively low levels, and especially in low density high water formulations can lead to excessive scorching and, possibly, runaway exothermic conditions which could result in spontaneous combustion of the foam.
Moreover, we have found that even if attempts are made to introduce copper into the foam by impregnation with a slurry of copper, at higher levels of copper, there is a serious degradation in the heat ageing properties of the foam, for example, on drying the foam.
SUMMARY OF THE INVENTION
We find surprisingly that a particular useful application of flexible polyurethane foam, containing copper or copper oxide particles, but especially foam containing relatively large amounts of copper or copper oxide particles lies in the alleviation of discomfort of people suffering from various joint, limb and muscle ailments such as arthritis and rheumatism.
We also find surprisingly that such relatively larger amounts of copper or copper oxide particles can be incorporated into a flexible polyurethane foam if the polyol used to prepare the polyurethane is of a high reactivity and high molecular weight, as hereinafter defined, so that the resultant flexible foam may be of the “high resilience” or “cold cure” type.
DESCRIPTION OF PREFERRED EMBODIMENTS
Thus, according to one aspect of the invention, there is provided a flexible polyurethane foam having, incorporated therein, particles of copper or copper oxide in an amount, based on metallic copper, of at least 1% by weight of the total weight of the metallized foam.
More preferably, the amount of copper or copper oxide particles, on the above weight basis, is at least 2%, still more preferably at least 3.5% and especially at least 4%.
The particles may be in the form of a powder or flake and are preferably of copper. Typically, the particle size may be from 10-100, preferably 30-60 microns, e.g. 40-50 microns.
The polyurethane is preferably derived from a polyol having a molecular weight of at least 3,500, more preferably at least 4,000, still more preferably from 4,000-8,000, especially from 4,500-7,000, more especially 4,800-6,000.
The hydroxyl value is preferably 20-60, more preferably 22-45, still more preferably 24-38, mg KOH/g.
It is also preferred that the polyol has an equivalent weight of from 1,000-3,000, more preferably from 1,500-2,000. This provides improved foam stability, flexibility and resilience.
It is especially preferred that the primary hydroxyl content, as a % of total hydroxyl content, hereinafter sometimes referred to as the primary:secondary hydroxyl ratio, provided by the hydroxyl groups in the foam be at least 20%, more preferably at least 50%, still more preferably at least 70%, most especially preferably at least 80%.
It is also especially preferred to use polyether polyols (or mixtures thereof) or polyester polyols (or mixtures thereof), particularly a polyether polyol which is an adduct of at least one low molecular weight polyol having at least 3 hydroxyl groups, such as glycerol, sorbitol, trimethylol propane or pentaerythritol, as polyol starter, with a mixture of propylene and ethylene oxides, which form polyether chains.
Tipping with ethylene oxide provides primary sites and the greater the proportion of such sites, the greater the reactivity of the polyol.
Thus, in order to provide an especially preferred, highly reactive polyether, either propylene oxide alone (required in any event at least to provide sufficient insolubility in water) or a mixture thereof with ethylene oxide are first reacted with the polyol starter to form polymerized chains which are then end-capped by reaction with further ethylene oxide to increase the reactivity considerably.
Particularly preferred polyether polyols are so-called “modified polyether polyols”, which contain organic fillers formed by the in-situ polymerization of suitable monomers and which fall into three classes, namely,
(1) polymer polyols;
(2) PHD polyols; and
(3) PIPA polyols.
In such polyols, in addition to the polyether polyol itself, the polyol contains at least one other polymer dispersed therein. Thus, a polymer polyol additionally includes a vinyl polymer dispersion, formed in situ in the polyol, as well as the reaction product of a polyol and a vinyl monomer. A PHD polyol contains a dispersion of a polyurea in the polyether polyol, formed in situ by polymerization of a diamine and an isocyanate, while a PIPA (polyisocyanate polyaddition) polyol contains a polymer dispersion formed by reaction of an alkanolamine with an isocyanate.
Such modified polymers are described more fully in “Telechelic Polymers: Synthesis and Applications”, Ed. E. J. Goethals, CRC Press Inc., Florida, 1989.
We find surprisingly that the polyurethane foams prepared from highly reactive polyols having a high primary:secondary hydroxyl ratio as described above are less susceptible to retardation of foam cure during their preparation and less susceptible to degradation in the heat ageing properties of the final foam.
Typical commercially available polyols for use in the incorporation, in situ, of copper into a polyurethane foam during its preparation are
1. DESMOPHEN 7653—a PHD (polyurea dispersion) polyol, which is a 10% dispersion of polyurea particles in a 6000 M.Wt.polyol, with a hydroxyl number 28 and a primary:sec

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