Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Reexamination Certificate
1998-08-04
2003-09-30
Pyon, Harold (Department: 1772)
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
C526S317100, C526S318600, C526S342000, C428S035700
Reexamination Certificate
active
06627325
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to polymer latex compositions useful in making rubber articles. More specifically, the invention relates to polymer latex compositions which are capable of forming materials possessing a combination of physical properties.
BACKGROUND OF THE INVENTION
Rubber articles such as gloves, condoms, bags, and the like are formed of latex polymeric materials and are useful in a wide variety of applications relating to, for example, medical, industrial, and household uses. These polymeric materials are generally water-based polymers which are readily formed using commercially-known processes. In such processes, it is important that the latex material be able to form a film on the surface of a mold. An example of such use relates to the making of latex gloves. These gloves are generally desirable since they can be made light, thin, flexible, tight-fitting, and substantially impermeable to liquids and gases. It is often desirable that the gloves possess adequate physical properties such as tensile strength and elongation.
It is desirable that the gloves be soft and comfortable to wear, and also provide a barrier to microbial penetration. A combination of high tensile strength and elongation combined with a low modulus is typically preferred. A lower modulus and a high elongation usually translate to a more flexible and comfortable glove. Additionally, the glove must have sufficient snap or elastic recovery.
Conventional latex gloves have typically been formed of natural rubber due to their resiliency and adequate physical properties. Nonetheless, many wearers of such gloves are allergic to proteins found in natural rubber. These individuals often experience difficulty when wearing the gloves. As a result, there have been efforts to develop gloves made from synthetic materials which are comparable to the natural rubber gloves in terms of comfort and physical properties. One synthetic alternative focuses on using poly(vinylchloride) (PVC). PVC is typically plasticized in order to be pliable enough to use in glove applications. Gloves formed from PVC are undesirable in many respects. For example, the gloves are usually very stiff and uncomfortable to the wearer. Furthermore, the plasticizer may migrate through the PVC and leach out when in contact with solvents. Also, it is believed that synthetic gloves formed from vinyl materials may provide an insufficient barrier to microbes due to imperfections in the film.
Another possible alternative to gloves made of natural rubber is described in U.S. Pat. No. 5,014,362 to Tillotson et al. The Tillotson et al. patent proposes gloves made with elastomeric material which allegedly possess adequate physical properties relating to fluid permeability, strength, and resilience. The gloves are taught to be formed from a nitrile-containing rubber, more particularly a carboxylated nitrile containing butadiene rubber. Nitrile-containing rubber gloves are typically desirable in demanding end use applications, such as those which often require superior properties such as solvent and puncture resistance. Nonetheless, for more general, less demanding applications, it is often not necessary for the gloves to exhibit such properties.
Latex polymers formed of styrene and butadiene have been utilized in attempting to make synthetic gloves. Nonetheless, these materials have largely been unsuccessful in that they typically are unable to “dip” effectively, i.e., coagulate to form a thin, uniform, defect-free film. Furthermore, the thin film usually does not possess sufficient physical properties to be used alone as a glove. For the most part, it is desirable to provide a thin film glove which is comfortable to use and provide sufficient barrier to microbes and chemicals. Accordingly, the glove should have a high tensile strength, high elongation, and low modulus. This combination of properties is typically difficult to achieve since films with high tensile strength tend to have a low elongation and a high modulus.
A need in the art remains for a synthetic latex material suitable in forming rubber articles which is free of natural rubber proteins and which can provide a wide range of desirable physical properties relating to strength, elongation, and modulus, as well as providing adequate comfort properties to the user. It is also desirable to produce a glove from materials which are cost competitive with natural rubber for general purpose applications.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the present invention to provide a polymer latex suitable in forming rubber articles which is free of natural rubber and imparts desirable physical properties to articles made therefrom.
To this end and others, in one aspect, the present invention provides a polymer latex composition suitable for making rubber articles. The composition comprises from about 5 to about 65 weight percent of an aromatic vinyl monomer from about 35 to about 90 weight percent of a conjugated diene monomer, and about 0.5 to about 10 weight percent of a component selected from the group consisting of an unsaturated acid monomer, a partial ester of an unsaturated polycarboxylic acid monomer, and mixtures thereof. The weight percents are based on the total weight of the monomers. A preferred aryl vinyl monomer is styrene. A preferred conjugated diene monomer is 1,3-butadiene. A preferred component is an unsaturated mono- or dicarboxylic acid monomer.
In another aspect, the invention provides a crosslinked film formed from a polymer latex composition. Preferably, the crosslinked film has a tensile strength of at least about 1000 psi, an elongation of at least about 400 percent, and a modulus at 100 percent elongation of no more than about 500 psi.
In yet another aspect, the invention provides a glove formed from the polymer latex composition of the invention. Preferably, the glove has a tensile strength of at least about 1000 psi, an elongation of at least about 400 percent, and a modulus at 100 percent elongation of no more than about 500 psi.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will now be described more fully hereinafter, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
The invention relates to a polymer latex composition suitable for making rubber articles. The polymer latex composition comprises from about 5 to about 65 weight percent of an aromatic vinyl monomer, from about 35 to about 90 weight percent of a conjugated diene monomer, and about 0.5 to about 10 weight percent of a component selected from the group consisting of an unsaturated acid monomer, a partial ester of an unsaturated polycarboxylic acid, and mixtures thereof. The weight percents are based on the total weight of the monomers.
For the purposes of the invention, the term “aromatic vinyl monomer” is to be broadly interpreted and include, for example, aryl and heterocyclic monomers. Exemplary aromatic vinyl monomers which may be employed in the polymer latex composition include, for example, styrene and styrene derivatives such as alpha-methyl styrene, p-methyl styrene, vinyl toluene, ethylstyrene, tert-butyl styrene, monochlorostyrene, dichlorostyrene, vinyl benzyl chloride, vinyl pyridine, fluorostyrene, alkoxystyrenes (e.g., paramethoxystyrene), and the like, along with blends and mixtures thereof. In addition to the composition range stated herein, the aromatic vinyl monomer may be used in an amount, based on the total weight of the monomers, preferably from about 5 to about 50 percent by weight, and most preferably from about 10 to about 40 percent by weight. A particularly preferred aromatic vinyl monomer is styrene.
Suitable conjugated diene monomers that may be used include, but are not limited to, C
4
to C
9
dienes such as
Ghosal Kanchan
Krishnan Venkataram
Dow Reichhold Specialty Latex LLC
Myers Bigel & Sibley Sajovec, PA
Pyon Harold
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