Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2000-01-12
2001-02-13
Foelak, Morton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S065000
Reexamination Certificate
active
06187829
ABSTRACT:
FIELD OF INVENTION
The present invention relates generally to curable latex compositions, and, more specifically, to heat-gellable latex compositions that are stable in the absence of heat for a relatively long period of time.
BACKGROUND OF THE INVENTION
Natural and synthetic rubbery cellular products have many applications. One significant use for such products is the application of a layer of foam to carpet backing to provide an integral cushion. Synthetic latex foam is now used widely in the textile industry.
It is customary in compounding latex dispersions to add all the compounding ingredients except the activator prior to the foaming step. A commonly used activator is zinc oxide. However, if this procedure is followed, the zinc oxide present would induce premature coagulation during the foaming step. Therefore, zinc oxide is frequently added prior to the foaming step.
U.S. Pat. No. 3,969,289 discloses a one-part storable foamable latex composition. The composition comprises a natural or synthetic elastomeric latex that is subject to cure. A curing system is provided comprising an ammonia-retarded dibenzyl dithiocarbamate accelerating agent that is inhibited in accelerating function in the presence of a base, such as ammonia. The composition includes an amount of ammonia sufficient to inhibit the cure of the latex and a foaming agent. Most importantly, the composition includes a siloxane heat-sensitizing agent to lower the coagulation temperature of the latex to about 90 degrees F., or above. The latex composition disclosed in the '289 patent is disadvantageous because it requires the use of a specific heat sensitizing agent.
Thus, a one-part foamable latex composition that is stable against gellation for extended periods of time prior to or after foaming has long been sought in the art.
SUMMARY OF THE INVENTION
The present invention satisfies the above-described needs by providing an improved storage stable, embossable, one-part, foamable latex composition. The improved latex composition of the present invention comprise a vulcanizable latex rubber dispersion, an amount of a vulcanizing agent sufficient to vulcanize the latex rubber, an amount of ammonia sufficient to prevent gellation of the latex rubber, an amount of a gelling agent sufficient to gell the latex rubber, the gelling agent comprising the reaction product of zinc chloride and an ammonium-containing compound, and an amount of an accelerator sufficient to accelerate vulcanization of the latex rubber, the accelerator comprising zinc dithiocarbamate.
In an alternate embodiment, the present invention comprises a one-part foamable latex composition which may be stored for extended periods of time prior to foaming without deterioration of physical properties. The composition comprises a natural or synthetic elastomeric latex subject to cure. A curing system is provided which comprises an ammonia-retarded dithiocarbamate accelerating agent, which agent is inhibited in accelerating function in the presence of ammonia. Ammonia is provided in an amount sufficient to inhibit the cure of the latex. A gelling agent comprising zinc ammonium chloride is present in an amount sufficient to gell the latex upon removal of a sufficient amount of ammonia from the composition. And, a frothing agent is provided in an amount sufficient to permit mechanical frothing of the composition into a foam.
The present invention also comprises a method comprising heating a composition for a time sufficient to cause gellation. The composition comprises a natural and/or synthetic elastomeric latex subject to cure. A curing system is provided which comprises an ammonia-retarded dithiocarbamate accelerating agent, which agent is inhibited in accelerating function in the presence of ammonia. Ammonia is provided in an amount sufficient to inhibit the cure of the latex. A gelling agent comprising zinc ammonium chloride is present in an amount sufficient to gell the latex upon removal of a sufficient amount of ammonia from the composition. And, a frothing agent is provided in an amount sufficient to permit mechanical frothing of the composition into a foam.
In an alternate embodiment, the present invention comprises a method of forming an embossed latex foam product comprising forming a foam by mechanically frothing a composition comprising a natural or synthetic elastomeric latex subject to cure. A curing system is provided which comprises an ammonia-retarded dithiocarbamate accelerating agent, which agent is inhibited in accelerating function in the presence of ammonia. Ammonia is provided in an amount sufficient to inhibit the cure of the latex. A gelling agent comprising zinc ammonium chloride is present in an amount sufficient to gell the latex upon removal of a sufficient amount of ammonia from the composition. And, a frothing agent is provided in an amount sufficient to permit mechanical frothing of the composition into a foam. The frothed composition is then formed into a layer. The layer is heated for a time sufficient to cause coagulation of the latex. Then, the layer is embossed after it has coagulated, but before it has cured.
Accordingly, it is an object of the present invention to provide an improved foamable latex composition and an improved method for forming a foamed latex composition.
Another object of the present invention is to provide an improved one-part foamable latex composition that may be stored for extended periods of time prior to foaming without deterioration of physical properties.
A further object of the present invention is to provide an embossable latex foam composition and a method for embossing a latex foam composition.
These and other objects, features and advantages of the present invention will become apparent after a review of the following detailed description of the disclosed embodiments and the appended claims.
DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS
The present invention relates to a one-part foamable latex composition that can be stored for extended periods of time prior to foaming. The latex foam of the present invention is also heat-gellable and embossable. The latex compositions of the present invention may be used for the production of foam rubber-backed fabrics, particularly carpets, in addition to the manufacture of unattached foam rubber sheeting and molded foam articles.
The latex composition of the present invention comprises a natural or synthetic elastomeric latex dispersion that is subject to cure, a curing system which comprises a curing agent and an ammonia-retarded accelerating agent, ammonia, and a gelling agent comprising zinc ammonium chloride. The latex composition may also optionally include a frothing agent, fillers, pigments, antioxidants, thickeners, and the like.
The latex composition of the present invention comprises a natural or synthetic elastomeric latex dispersion that is subject to cure or vulcanization. The specific nature of the elastomeric latex is not critical to the present invention and all elastomeric polymers commercially available in latex form may be used. Examples of elastomeric latex dispersions that are useful in the present invention include acrylonitrile, chloroprene, isoprene, butadiene-styrene, butadiene-acrylonitrile, polyacrylonitrile, polyisoprene, polystyrene, polyvinylidene chloride, polyvinyl chloride, polyvinyl acetate, polymethyl methacrylate, co-polymers of the monomers of these resinous polymers and resinous copolymers of these monomers with other copolymerizable monomers, such as C
4
-C
10
conjugated dienes. Other suitable latices are disclosed in U.S. Pat. Nos. 3,904,558; 3,969,289, 4,240,860; 4,888,134; 3,737,488 and 2,845,659, all of which are incorporated herein by reference. For best results, the starting latices should contain at least 15% by weight total solids before compounding; preferably, about 40%-75% by weight total solids.
The latex composition of the present invention also comprises a curing agent or vulcanizing agent. Many curing agents or vulcanizing agents for the elastomeric latices identified above are known to
Foelak Morton
Kilpatrick & Stockton LLP
Textile Rubber & Chemical Company, Inc.
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