Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-07-26
2002-04-09
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
active
06369154
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to polymer latex compositions useful in making elastomeric articles of manufacture, and more particularly composition useful in making an article of manufacture from a crosslinkable film having improved aging and ozone resistance properties, and other advantages over natural rubber.
Articles of manufacture 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, especially for medical applications. Latex gloves are preferred since they can be made light, thin, flexible, tight-fitting, and substantially impermeable to a variety of li uids and gases. It is often desirable that the gloves possess ade uate physical properties such as tensile strength and elongation, and are comfortable to the wearer.
It is also desirable that the gloves possess ade uate aesthetic properties with respect to drape, softness, etc., provide a good barrier to microbial penetration, and be substantially odorless. A combination of high tensile strength and elongation combined with a low modulus is typically preferred. In addition to the above, it is desirable that the glove have sufficient snap or elastic recovery.
Conventional latex gloves have typically been formed of natural rubber primarily due to their resiliency, softness, ade uate physical properties, and good elastic recovery. 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 do not possess a soft and rubbery feel. 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. Additionally, these gloves tend to display inade uate elastic recovery (snap) properties and poor softness.
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 are claimed to possess ade uate 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 re uire superior properties such as solvent and puncture resistance.
Another alternative is proposed in U.S. Pat. No. 5,910,533 to Ghosal et al. The Ghosal et al. patent proposes a latex composition for gloves having a relatively high (i.e. 80 to 99 percent by weight) amount of a conjugated diene monomer, and in addition includes an unsaturated acid monomer and an additional unsaturated monomer.
Although these various lattices provide articles of manufacture having high tensile strength and elongation properties, there continues to be a need for articles of manufacture having improved aging and resistance to ozone properties. There are also applications where the use of synthetic elastomers are desirable, but where the properties conferred by styrene, acrylonitrile or chloroprene or derivatives thereof are unnecessary or undesirable or both.
SUMMARY OF THE INVENTION
To these ends and other objects and advantages, the present invention provides a polymer latex composition. The latex composition comprises from about 35 to about 80 weight percent of aliphatic conjugated diene monomer; from about 10 to about 65 weight percent of unsaturated ester or amide monomer and, above 0 to about 15 weight percent of unsaturated acid monomer. By lowering the amount of the aliphatic conjugated diene monomer as compared to, for example, the amount proposed by Ghosal et al., improved aging and ozone resistance properties can result.
The latex in one embodiment is devoid of styrene, acrylonitrile and chloroprene and derivatives thereof. The latex can be formed into a crosslinked film, and utilized to manufacture a number of so-called “dipped goods” such as articles including gloves, condoms, bags and the like. For example, the polymer latex can be contacted with a mold in the shape of the article and then cured to form the article. It is believed that high levels of conjugated diene monomers lead to high levels of residual unsaturation in the polymer chain which can result in undesirable properties such as poor aging and poor ozone resistance.
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 latex composition comprises from about 35 to 80 weight percent, preferably from about 45 to about 70 weight percent of aliphatic conjugated diene monomer, from about 10 to about 65 weight percent, preferably from about 20 to about 40 weight percent of unsaturated ester or amide monomer, and above 0 to about 15 weight percent, preferably about 2 to 7 weight percent of unsaturated acid monomer. Blends or copolymers of the monomers may be used.
Suitable conjugated diene monomers that may be used include, but are not limited to C
4
to C
9
dienes such as, for example, butadiene monomers such as 1,3-butadiene, 2-methyl-1,3-butadiene, and the like. Blends or copolymers of the diene monomers can also be used. A particularly preferred conjugated diene is 1,3-butadiene.
The unsaturated ester or amide monomers which may be used are well known and include, for example, acrylates, methacrylates, acrylamides and methacrylamides and derivatives thereof. The acrylic and methacrylic acid derivatives may include functional groups such as amino groups, hydroxy groups, epoxy groups and the like. Exemplary acrylates and methacrylates include, but are not limited to, various (meth)acrylate derivatives including, methyl methacrylate, ethyl methacrylate, butyl methacrylate, glycidyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, 3-chloro-2-hydroxybutyl methacrylate, 2-ethylhexl(meth)acrylate, dimethylaminoethyl(meth)acrylate and their salts, diethylaminoethyl(meth)acrylate and their salts, acetoacetoxyethyl(meth)acrylate, 2-sulfoethyl(meth)acrylate and their salts, methoxy polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, tertiarybutyl aminoethyl (meth)acrylate and their salts, benzyl(meth)acrylate, 2-phenoxyethyl(meth)acrylate, gamma-methacryloxypropyltrimethoxysilane, propyl(meth)acrylate, isopropyl(meth)acrylate, isobutyl (meth)acrylate, tertiarybutyl (meth)acrylate, isobornyl (meth)acrylate, isodecyl(meth)acrylate, cyclohexyl(meth)acrylate, lauryl(meth)acrylate, methoxyethyl (meth)acrylate, hexyl (meth)acrylate, stearyl(meth)acrylate, tetrahydrofufuryl(meth)acrylate, 2(2-ethoxyethoxy), ethyl(meth)acrylate, tridecyl(meth)acrylate, caprolactone(meth)acrylate,
Michl Paul R.
Myers Bigel Sibley & Sajovec P.A.
Reichhold Inc.
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