Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Reexamination Certificate
2003-05-05
2004-03-30
Tarazano, D. Lawrence (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
C428S152000, C428S155000, C428S156000, C427S372200, C427S384000
Reexamination Certificate
active
06713156
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an abrasive substrate formed by the application of a polymer composition to the surface of the substrate. The polymer composition is applied to the substrate in a manner producing an uneven, structured coating on the substrate, resulting in a surface having abrasive properties. The invention is especially useful in producing abrasive non-woven materials useful as wet and dry wipes.
BACKGROUND OF THE INVENTION
Abrasive substrates, and especially nonwovens and papers are widely used in wipes for make-up removal, personal cleansing, household cleaning, and industrial scrubbing. Conventional abrasive articles typically consist of a layer of abrasive particles bonded to a substrate. The particles are often bound to the substrate using a polymeric binder.
U.S. application No. 2002/0026752 describes such an abrasive article having precisely shaped particles. U.S. Pat. No. 6,352,567 also describes an air-laid non-woven held together with a phenolic resin and having ceramic aluminum oxide and alumina particles coated onto the surface to add abrasion. U.S. Pat. No. 6,140,388 describes an abrasive non-woven using a cross-linking polymer binder to bind abrasive grains to the non-woven material.
Abrasive non-woven articles have been formed without added abrasive materials. U.S. Pat. No. 4,659,609 discloses a melt-blown process, in which polymeric fibers 25 have their ends exposed to the surface, creating an abrasive surface. These multi-layer composite materials employ a spun-bonded supporting layer carrying an outer layer of melt-blown abrasive fibers, thermally bonded to the supporting web. The disadvantages of non-uniform distribution of the abrasive fibers was improved upon in U.S. Pat. No. 5,786,065 by forming a nonabrasive web of thermoplastic fibers, then heating the fibers to form nodulated fiber remnants.
The problem with these current methods is that they either require thermally-bonded non-woven materials, or abrasive particles in addition to a polymeric binder. These processes require additional manufacturing time and expense. There is a need for an abrasive nonwoven, where the abrasive surface is formed by surface application of a polymer composition, without added abrasive particles.
Surprisingly, it has now been found that an abrasive substrate may be formed by applying a polymer solution or dispersion by a non-homogeneous application of the polymer to a substrate, and processing the polymer coated substrate under conditions to produce an abrasive surface.
SUMMARY OF THE INVENTION
It is an object of the present invention to form an abrasive surface on a substrate solely by application of a polymer composition to the surface.
It is a further object of the invention to produce a nonwoven substrate that can function as both a wet and a dry abrasive.
The present invention is directed to an abrasive substrate comprising a substrate having directly deposited on at least one surface, in a non-homogeneous manner, a cured polymer composition, wherein said polymer composition has an MFFT of greater than −10° C. and said polymer composition comprises one or more polymers having a Tg or greater than 0° C., wherein the cured polymer composition on the substrate surface is abrasive, and wherein say abrasive substrate is free of abrasive particles.
The invention is also directed a process for producing an abrasive substrate comprising:
a) applying a polymer composition in the form of a solution or dispersion to a substrate in a non-homogeneous manner;
b) curing said polymer composition in a manner to form a non-homogeneous polymer surface on the substrate, producing an abrasive surface.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to an abrasive substrate, having a cured polymer composition in a non-homogeneous arrangement on the substrate surface, producing an abrasive surface without the need for embedded abrasive particles.
By “abrasive” as used herein is meant that the substrate having a heterogeneous polymer surface is able to roughen or wear away another surface. The abrasive substrates of the present invention are generally mild abrasives useful on skin, or to remove materials stuck onto hard surfaces, without damaging said surface. The abrasiveness of the substrate is due to the cured polymer composition, and not to any added solid abrasive materials such as mineral particles, curly fibers, or other solid additives.
The abrasive substrate of the invention is formed by properly selecting and combining:
a) a specified polymer composition,
b) a specific means of applying the polymer composition to a substrate in a non-homogeneous manner, and
c) a means of processing the polymer coated substrate to produce an abrasive surface.
The polymer composition useful in the present invention is one having a minimum film-forming temperature (MFFT) above −10° C., and in most room temperature applications an MFFT above 15° C. The polymer composition useful in the present invention is in the form of a liquid solution or dispersion. Preferably the polymer composition is an aqueous solution or dispersion, and most preferably it is in the form of a polymer emulsion. The polymer composition is a combination of a solvent (water, organic solvent or a mixture thereof), a polymer and optional adjuvants. It is known in the art that the MFFT of a polymer composition can be raised or lowered from the Tg of the polymer by the addition of certain adjuvants, such as plasticizers, coalescents, surfactants, and other additives
The polymer composition must be hard enough at the end-use temperature to serve as an abrasive. The Tg of the polymer composition will preferably be above 0° C., and in most room temperature applications is preferably above 15° C. The MFFT of the polymer composition should be below the processing temperature in order to allow for bonding to the substrate. In most applications of the present technology, the MFFT of the polymer composition will be below 105° C.
The polymer useful in the polymer composition may be of any chemistry and architecture. It may be a homopolymer, copolymer, or terpolymer, and may be a blend of two or more different polymers. The polymers may be random, block, star or other known architecture. They may be made by known means, such as emulsion polymerization, dispersion, suspension or solution polymerization. In a preferred embodiment the polymer is formed by emulsion polymerization. The polymers may be non-functional, or may contain functionality designed to optimize the properties of the coating in the specific application. One of skill in the art will be able to adjust monomer content and architecture to improve end-use performance of the polymer composition. The polymer could be a synthetic polymer, or could be a natural polymer such as, for example, a polysaccharide, starch, modified starch, or guar gum. Preferred polymers include homopolymers and copolymers having one or more of the following monomers: (meth)acrylates, maleates, (meth)acrylamides, vinyl esters, itaconates, styrenics, unsaturated hydrocarbons and acrylonitrile, nitrogen functional monomers, vinyl esters, alcohol functional monomers. Particularly preferred monomers include, but are not limited to, vinyl acetate; methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, ethylene, vinyl chloride, and styrene.
Polymer compositions having similar MFFTs may impart different abrasive properties under dry conditions than under wet conditions. Some of the considerations that must be considered in choosing a polymer for use in the polymer composition include water solubility, solvent computability, abrasive duration, level of abrasiveness, level of formaldehyde acceptable in the application, governmental regulations, and other conditions varying with the many possible end-use applications in which an abrasive substrate may be useful.
In one embodiment, the polymer in the composition is a cross-linkable polymer. By “cross-linkable” as used herein is meant a polymer that is capable of undergoing cross- linki
Barcomb Christopher
Farwaha Rajeev
Pauls Steven
Almer Charles W.
National Starch and Chemical Investment Holding Corporation
Roland Thomas F.
Tarazano D. Lawrence
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