Stock material or miscellaneous articles – Composite – Of polyamidoester
Patent
1999-01-25
2000-11-07
Gorr, Rachel
Stock material or miscellaneous articles
Composite
Of polyamidoester
4284233, 4273855, 21618, 2167, A41D 19015
Patent
active
061434167
DESCRIPTION:
BRIEF SUMMARY
This invention relates to polyurethane articles, particularly to thin-walled articles made by dipping, and especially (but not exclusively) to gloves of the sort used by surgeons.
For many years past, it has been known to make surgeon's gloves from natural rubber latex. The gloves so made have a number of very satisfactory properties and are very widely used. However, natural rubber contains small amounts of protein and accelerators and it is believed that this may possibly give rise to allergies in users of the gloves. For this and other reasons, attention has passed to the possibility of using elastomers other than natural rubber.
One alternative material is polyurethane. Polyurethanes are available which have a higher modulus than natural rubber and these materials can be used to make gloves which are thinner than natural rubber gloves and have a higher tensile strength. However, these stiffer polyurethanes are too hard to give a good surface grip. They tend to-have a shiny surface which, particularly in moist or wet conditions, is slippery. It is, of course, very important that articles such as surgeons' gloves should have good grip surfaces, especially in moist and wet conditions.
It is known to improve the grip of surgeons' gloves by providing a roughened outer surface to the gloves. This technique is described, for example, in U.S. Pat. No. 3,255,492. Here, a matt surface is provided on the outer surface of a glove by using a dipping former whose surface has been roughened such as by caustic etching, vapour blasting, sand blasting, anodizing or the like. The U.S. specification is principally concerned with polyvinylchloride gloves, but it also refers to the possibility of making certain polyurethane gloves in this way.
We have investigated the use of roughened formers to provide roughened outer surfaces on polyurethane gloves, but we have found that in practice, there is a serious practical problem with this technique as applied to organic solutions of high modulus polyurethanes. In particular, the roughened surface of the former promotes the formation of bubbles in the polyurethane coating on the former. These bubbles tend to remain in the coating and to give rise to various problems, including problems in the integrity of the coating.
We have now found a way of overcoming this, whereby a roughened outer grip surface can be provided on polyurethane dipped articles by using a roughened former.
According to a first aspect of the present invention there is provided a method of forming a thin-walled article, which method comprises coating a roughened former with a first elastomer, which first elastomer substantially does not retain any bubbles that may be formed; coating a high modulus polyurethane to the coated former to form the main body of the article; drying and/or curing the composite article; and stripping the composite article from the former, whereby the surface of the first elastomer has a rough surface to provide surface grip.
In this way, the polyurethane glove (or other article) has a roughened grip surface derived from the effect of the roughened former, without the problem of bubble formation in the polyurethane.
In the preferred embodiment, the first elastomer is coated on the former by dipping the former into the first elastomer. Similarly, the high modulus polyurethane is preferably coated on the former by dipping the former into said polyurethane.
According to a second aspect of the present invention, there is provided a thin-walled article comprising a grip coating of a first elastomer on a high modulus polyurethane substrate, wherein the coating has a rough surface to provide surface grip.
The polyurethane will normally be a thermoplastic polyurethane (although curable polyurethanes can be used) and will normally have a modulus (i.e. a modulus at 100%) extension of at least about 2 MPa, but usually no greater than about 5 MPa. There are many commercially available polyurethanes which may be used, including for example polyether polyurethanes (e.g. Avalon 80 AT), polyester polyureth
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Brindle Philip Wayne
Williams Thomas Haydn
Gorr Rachel
LRC Products Limited
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