CA2076730A1 - Substrate having a smooth, nonabrasive, nontacky antislip coating - Google Patents

Abstract

Abstract An article of manufacture consisting of a substrate having a smooth, nonabrasive, nontacky antislip coating on part or all of a surface thereof, which coating includes from about 80 to about 90 percent by weight, based on the dry weight of the coating, of cis-polyisoprene and from about 10 to about 20 percentby weight, based on the dry weight of the coating, of thermally expanded micro-beads having particle sizes before expansion in the range of from about 5 to about 30 µm. The substrate can be paper, film, or a woven or nonwoven fabric.

Description

~ ~ 7 fi J~ 3 ~
SUBSTRATE HAV~NG A SMOOI~I, ~ONAB RASIVE, NONTACKY ANTISLIP COA'rING

Cross-Reference ~o Related Application s A smooth nonahrasive antislip coating which utilizes expandable microbeads is described and claimed in Application Serial No. 07/815,206, entitled SUBSTRATE HAVING A SMOOTH NONABRASIVE ANTISLIP
COATING and filed on December 31, 1991 in the names of Frances Josep 10 Kronzer, Theodore John Tyner, and John Patrick Allison.

Background of the Invention - The present invention relates to an article of manufacture cornprising a 15substrate having a smooth nonabrasive antislip coating on part or all of a surface thereof. The antislip property of the coating is obtained through the combination of natural rubber, i.e., cls-polyisoprene, with thermally expandable microbeads.Antislip or non-skid coatings are, of ~ourse known. For example, non-skid surface compositions for paper products are disclosed in U.S. Patent No.
204,418,111 to Carstens. The composition consists of an aqueous suspension of colloidal silica and urea. The silica typically is present at a level of from approximately I to 5 percent by weight and has particle sizes in the range of 10- to 150 millimicrons. A urea/silica weight ratio between 0.10 and slightly greater than 3.00 is most effective. The composition is applied to the paper product by,25for example, spraying.
An antiskid paper with enhanced ~riction retention is desc~ibed in U.S.
Patent No. 4,980,024 to Payne et al. According ~o this re~erence,lsuperiority inretained slide angle of antiskid paper is achieved by spraying or otherwise coa~ing r9, ~3 ~3 the paper with a composition of matter consisting essentially of silica sol.
glycerine~ and an acrylamide homopolymer.
As illustrated by the foregoing two patents, antislip coatings for papers typically employ an inorganic material in the coating binder. Such coatings often S are abrasive and. in ~act, are closely related to such abrasive papers as sandpapers, emery cloths, and the like, as illustrated by the references which follow.
U.S. Patent No. 2,899,288 to Barclay relates to a method of forming an abrasive sheet. Briefly, a cloth backing sheet fabricated of a thermoplastic 10 material is passed through a heated zone in which one face of the sheet is temporarily softened, an abrasive material is applied evenly over the softened face. the abrasive is pressed into the softened sheet by means of a nip roll andsimultaneously cooled.
U.S. Patent No. 3,166,388 to Riegger et al. relates to a sandpaper. The 15 sandpaper comprises a reinforced paper backing, a barrier material, a layer of - making varnish, and a layer of abrasive grits embedded in thc making varnish.
The barrier material may be in the form of a barrier layer of flexible ma~erial which only partly penetrates into one side of the backing, or it may be in the form of flexible rubbery solids which penetrate into and partially fill the voids in 20 the paper backing throughout itS thickness. Backings comprise a web or network of woodpulp fibers and a multiplicity of relatively flexible and tough thermoplas-tic reinforcing members distribu~ed substantially throughout the web in bonding relation with the woodpulp fibers.
The commercial introduction of thermally expandable microspheres a 25 number of years ago has led to a number of different uses, some examples of which are given below.
U.S. Patent No. 4,006,273 relates to washable and dry-cleanable raised prin~ing on fabrics. Raised prints and graphic designs on fabrics which can safely and effectively be dry-cleaned and washed are provided by formulating a cross-7 ~
linkable polymer printing medium comprising an adherent fiim-forming cross-linkable polymer binder in a liquid vehicle therefor about 1 to 45 weight percent thermally expandable microspheres, based on the weight of the binder, applying said medium to a fabric~ heating at a temperature of about 180 to 250F to 5 expand the microspheres and cross-link the polymer, and then curing for about I minute at a temperature of about 300QF. The microspheres can have diameters from about 0.5 ~o about 300 microns (micrometers or ~m), desirably i~rom about 3 to 50 microns, and more desirably from about 5 to 20 microns.
U.S. Patent No. 4,044,176 to Wolinski et al. describes graphic arts media 10 which of~er raised~ three-dimensional effects. A basic medium is formulated of a colorant, film-forming binder, a solvent vehicle, and thermally expandable microspheres. The microspheres are treated to preclude or inhibit solvation in the solvent vehicle by coating with a compound which is a non-solvent for the microspheres but which preferentially wets the surface thereof. Allyl alcohols 15 having about 3 to 5 carbon atoms in the alkyl chain are employed. The medium is selectively applied to a substrate, dried, and heated to expand the microspheres.
Japanese Published Application No. 90/76,735 relates to the manufacture of slightly rough sheets. Such sheets, useful as wall and floor coverings, leather substitutes, packaging sheets, etc., are prepared by coating thermoplastic sheets, 20 completely or in patterns, with resins containing microencapsulated blowing agents (e.g., butane) and simultaneously expanding the microcapsules and softening the resins. In an example, flame-retardant paper was coated in patterns with an acrylic polymer-PVC blend containing microencapsulated blowing agents, coated with a PYC plastisol, and heated at 225 to give a sheet with a sandy 25 appearance.
It may be noted that microspheres which are not thermally expandable also are known. A few applications for such microspheres are described below.
A woven polyester-backed flexible coated abrasive having microballoons in the backsize is described in U.S. Patent No. 4,111~667 to Adams. The 2 ~ 7 r3 ~

backsize is used with heavy-duty flexible coated products, particularly polyester-baclced coated ahrasive for use in making belts. The otherwise conventional backsize coating includes from 2 to lO percent by weight of hollow microspheres.The coating is applied on the reverse or nonabrasive side of a woven polyester backing. The microspheres (or microbeads or microballoons) are hollow spheres of resin or glass having a diameter in the range of between 5 and 125 microns (micrometers) .
U.S. Patent No. 4,543,106 to Parekh relates to a coated abrasive product containing hollow microspheres beneath the abrasive grain. The product comprises a fabric backing, a layer of abrasive grain, and at least one layer ofresin between the backing and the abrasive grain. Hollow microspheres are present and at least partly and usually entirely embedded in the resin layer. Ingeneral, the hollow microspheres comprise hollow spherical bodies which may be of glass or plastic materials such as a phenolic resin, which have diameters from about 5 to about 500 microns (micrometers) and an average diameter of f~om about 25 to about 125 microns. The microspheres generally have a shell thickness which averages from about 5 to about 20 percent of the diameter of themicrospheres. The microspheres usually are incorporated into the resin layer in an amount of from about 5 to about 20 percent by weight of the resin layer.
A reference which does not fit in any of the foregoing categories is included for the sake of completeness. That reference is U.S. Patent No.
5,001,106 to Egashira et al., which relates to an image-receiving sheet. Such sheet comprises a base sheet and a receiving 5ayer, provided on one sur~ace of the base sheet, for receiving a dye or pigment migrating from a heat transfer sheet. The base sheet comprises one or two or more layers, with at least one layer having a porous or foamed structure. A layer having a porous or foamed structure can be obtained by such methods as: (a) stretching a film prepared from a thermoplastic resin and containing fine inorganic or organic particles, (b) extruding an organic solvent solution of a synthetic resin into a coagulating bath, 2~7~7'~

and (c) extruding a resin together with a foaming agent. Under certain circumstances. it iS desireable to roughen at least a part of bath front and back surfaces of the image-receiving sheet, e.g., the non-image portion of the receiving surface or the back surface of ~he image-receiving sheet, by imparting fine unevenness thereto.
References relating to the microbeads themselves include those described below.
U.S. Patent No. 3,615,972 to Morehouse, Jr. et al. describes expansible thermoplastic polymer particles containing volatile fluid foaming agent and a lO method of foaming the sasne. Thermoplastic microspheres are prepared which encapsulate a liquid blowing agent. Heating of the microspheres causes expansion. The microspheres are useful for coatings, rnoldings, piastic ssnoke~
etc.
Polymer foam compositions are described in U.S. Patent No. 3.864,181 15 to Wolinski et al. The patent describes a composition and method for forming foamed polymers. The composition comprises a dispersion of microspheres in a solution of the polymer in a solvent. The compositions are applied to a substrate, dried, and heated to expand the microspheres, thus forming a foamed polymer. The particular surface charactesistics of foamed polymers are stated to20 have been utilized in non-skid coatings for carpets, rugs, bathtub mats, flooring, coat hangers, handles ~or tools asld athletic equipment, and the like.
U.S. Patent No. 4,722,943 to Melber et al. relates to a composition and process for drying and expanding microspheres. Microsphere wet cake is mixed with a processing aid effective to prevent agglomeration asld surface bonding of2~ the microspheres, and thereafter removing water by drying with continuous mixing, optionally also under reduced pressure, i.e., vacuum drying. By the control of the application of heat asld balancing temperature and t4e mixing, and optionally also the reduced pressure, it is possible to also control expansion of the microspheres from substantially none to substantially theoretical limits of 7 ~ ~
~xpansion. Suitable processing aids include, by way of example, dry inorganic pigmen~s or filler materials and the like. and related organic materials. See also U.S. Patent Nos. 4 829,094 to Melber et al. and 4,843,104 to Meiber et al.
Notwithstanding the foregoing, there still is a need for an antislip coating 5 which is smooth and nonabrasive. especially for papers, films, and fabrics.

Summ~ry of the Invention It therefore is an object of the present invention to provide an article of 10 manufacture comprising a substrate having a smooth, nonabrasive, nontacky antislip coating on part or all of a surface thereof.
It also is an object of the present invention to provide an article of mamlfacture which comprises a paper having a first surface and a second surface,- in which said first surface has a smooth, nonabrasive, nontacky antislip coating 15 adjacent to and contiguou~ with said first surface.
These and other objects will be apparent to one having ordinary skill in the art from a consideration of the specification and claims which follow.
Accordingly, the present invention provides an article of manufacture comprising a substrate having a smooth, nonabrasive, nontacky antislip coating 20 on part or all of a surface thereof. which coating consists essentially of from about 80 to about 90 percent by dry weight, based on the dry weight of the coat-ing, of cis-polyisoprene and from about 10 to about 20 percent by dry weight~
based on the dry weight of the coating, of thermally expanded microbeads having particle sizes before expansion in the range of from about S to about 30 ,um, in25 which said substrate is selected from the group consisting of papers~ films, and woven and nonwoven fabrics.
The present invention also provides an article of manufacture which comprises a paper having a first surface and a second surface, in which said first surface has a smooth, nonabrasive~ nontacky antislip coating adjacent to and 2~7~7~ 3 contiguous with said first surface, whicn coating consists essentia~ly of from about 8û to about 90 percent by dry weight, based on the dry weight of the coating, ofcis-polyisoprene and from about 10 to about 20 percent by dry weight, based on the dry weight of the coating, of thermally expanded microbeads having particle S sizes before expansion in the range of from about S to about 30 ~m.

Detailed Description of the InYention As use herein, the term "srnooth" refers to the absence of sharp or angular - 10 particles in the nonabrasive antislip coating of the present invention. Rather, such coating con~ains smooth, e.g., spherical, microbeads. The term also refers to the feel of the surface when touched, i.e., to the tactile characteristics of the coating. That is, the coating feels "smooth" to the touch.
The term "natural rubber" as used herein means cis-polyisoprene.
15 However, for convenience the latter terminology has been used in preference to the term "natural rubber."
The term "nontacky" is used herein to mean the absence of tack. Tack is the quality or state of sticking or adhering. Thus, tacky means barely sticky tothe touch, or havin~ a quality of adhering, clinging, or birlding, all which 20 characteristics are absent in the nontacky coating of the present invention.
In general, the substrate can be any paper, film, or fabric. The fabric can be either woven or nonwoven, although a nonwoven fabric is more desired than a woven fabric. The material from which a film or fabric is made is not known to be critical. The nonwoven webs include any of the known nonwoven webs, 25 including, but not limi~ed to, meltblown webs, spunbonded webs, co~ormed webs, bonded carded webs, laminates of two or more of such webs with or without additional layers, and the like. I
As a practical matter, films and the more desired nonwoven i~abrics are prepared from therrnoplastic polymers. Examples of thermo.plastic polymers 2 ~ r~ (- 7 c~ ~

include, by way of illustration only, end-capped polyacetals, such as po~y(oxy-methylene) or polyformaldehyde. poly(trichloroacetaldehyde), poly(n-valeral-dehyde), poly(acetaldehyde). poly(propionaldehyde), and the like; acrylic polymers, such as polyacrylamide, poly(acrylic acid), poly(methacrylic acid), 5 poly(ethyl acrylate), poly(methyl methacrylate), and the like; fluorocarbon polymers, sueh as poly(tetrafluoroethylene), perfluorinated ethylene-propylene copolymers, ethylene-tetra~uoroethylene copolymers, poly(chlorotrifluoroethyl-ene), ethylene-chlorotrifluoroethylene copolymers, poly(vinylidene fluoride), poly(vinyl fluoride), and the like; polyarnides, such as poly(6-aminocaproic acid) 10 or poly(~-caprolactam), poly(hexamethylene adipamide), poly(hexamethylene sebacamide), poly(l 1-aminoundecanoic acid), and the like; polyaramides, such aspoly(imino- 1 ,3-phenyleneiminoisophthaloyl)orpoly(m-phenyleneisophthalamide), and the like; parylenes, such as poly-~-xylylene, poly(chloro-~-xylylene), and the like; polyaryl ethers, such as poly(oxy-2,6-dimethyl-1 ,4-phenylene) or poly(p-15 phenylene oxide), and the like; polyaryl sulfones, such as poly(oxy- 1,4-phenylenesulfonyl-l ,4-phenyleneoxy-1 ,~phenylene-isopropylidene-1 ,~phenylene),poly(sulfonyl-l ,4-phenyleneoxy-1 ,4-phenylenesulfonyl-4,4'-biphenylene), andthelike; polycarbonates, such as poly(bisphenol A) or poly(carbonyldioxy- I ,4-phenyl-eneisopropylidene-1,4-phenylene), and the like; polyesters, such as poly(ethylene 20 terephthalate), poly(tetramethylene terephthalate), poly(cyclohexylene- 1,4-dimethylene terephthalate) or poly(oxymethylene-1,4-cyclohexylenemethylene-oxyterephthaloyl), and the like; polyaryl sulfides, such as poly(~2-phenylene sulfide) or poly(thio-1,4-phenylene), and the like; polyimides, such as poly-(pyromellitimido-1,4-phenylene), and the like; polyolefins, such as polyethylene, 2S polypropylene, poly(l-butene), poly(2-butene), poly(1-pentene), poly(2-pentene), poly(3-methyl-1-pentene), poly(4-methyl-1-pentene), 1 ,2-poly-1 ,3-bu~adiene. 1,4-poly-1,3-butadiene, polyisoprene, polychloroprene, polyacrylonitrile, poly(vinylacetate), poly(vinylidene chlonde), polystyrene, and the like: copolymers of the 2 ~ 7 f~

foregoing. such as acrylonitr~le-butadiene-styrene (ABS) copolymers, ~nd the like;
and the like.
Thermoplastic polyolefins are more desired and include polyethylene, polypropylene, poly(l-butene), poly~2-butene), poly(l-pentene), poly(2-pentene),poly(3-methyl- 1 -pentene), poly(4-methyl- 1 -pentene), 1 ,2-poly- 1 ,3-butadiene, 1,4-poly-1,3-butadiene, polyisoprene, polychloroprene, polyacrylonitrile, poly(vinylacetate), poly(vinylidene chloride), polystyrene, and the like.
The more desired polyolefins are those which contain only hydrogen and carbon atoms and which are prepared by the addition polymeri7ation of one or more unsaturated monomers. Examples of such polyolefins include, among others, polyethylene, polypropylene, poly(1-butene), poly(2-butene)~ poly(1-pentene), poly(2-pentene), poly(3-methyl-1-pentene), poly(4^rnethyl-1-pentene), 1,2-poly-1,3-butadiene, 1,4-poly-1~3-butadiene,polyisoprene,polystyrene,andthe like. In addition, such term is meant to include blends of two or more polyolefins and random and bloclc copolymers prepared from two or more - different unsaturated monomers. Because of their commercial importance, the most desired polyolefins are polyethylene and polypropylene.
The more desired substrates are papers and nonwoven fabrics prepared from thermoplastic polyolefins, especially meltblown and spunbonded nonwoven webs.
When the substrate is a paper, the nature of the paper is not known to be critical, provided it has sufficient strength for handling, coating, sheeting, and/or other operations associated with its manufacture. In desired embodiments, the base sheet will be a latex-impregnated paper. By way of illustration, a desired paper is a water leaf sheet of wood pulp fibers impregnated with a reactive acrylic polymer latex such as Rhoplex~ B-15 (Rohm and Haas Company, Philadelphia, Pennsylvania~. However, any of a number of other latexes can be used, if desired, some examples of which are summarized in Table I, below.

2~7~3f~
Iable I
Suit3ble Latex_s for B~ se Sheet Polyrner Type _ Product l~dentification_ Polyacrylates Hycar~ 26083, 26084, 26120, 26104, 26106, 26322 B. F. Goodrich Company Clevelarld, Ohio Rhoplex~ HA-81 HA-12, NW-1715 Rohm and Haas Company Philadelphia, Pennsylvania Carboset~ XL-52 B. F. Goodrich Company Cleveland, Ohio Styrene-butadiene copolymers Butofan~ 4262 BASF Corporation Sarnia, Ontario, Canada DL-219, DL-283 Dow Chemical Company Midland, Michigan Ethylene-vinyl acetate copolymers Dur-O-Set~ E-666, E-646, E-669 National Starch & Chemical Co.
Bridgewater, New Jersey Nitrile rubbers Hycar~ 1572, 1577, 1570 x 55 B. F. Goodrich Company Cleveland, Ohio Poly(vinyl chloride) Geon~ 552 B. F. Goodrich Company Cieveland, Ohio Poly(vinyl acetate) Vinac~ XX-210 Air Products and Chemicals. Inc.
Napierville, Illinois ~0~7~

Ethylene-acrylate copolymers Michem~ Prime 4990 Michelman, Inc.
Cincinnati~ Ohio Adcote~ 56220 Morton Thiokol, Inc.
Chicago, Illinois The irnpregnating dispersion typically also will contaun clay and a 10 delustrant such as titanium dioxide. Typical amounts of these two materials are 16 parts and 4 parts, respectively, per 100 parts of polymer on a dry weight basis. An especially desirable base sheet has a basis weight of 13.3 Ibs/1300 ft2 (50 g/m2) before impregnation. The impregnated paper desirably contains 18 parts impregnating solids per 100 parts fiber by weight, and has a basis weight of 15.6 Ibs/13~0 ft2 ~58 g/m2), both on a dry weight basis. A suitable caliper is - 3.8 mils + 0.3 mil (97 ~ 8 micrometers).
Such a paper is readily prepared by methods which are well known to those having ordinary skill in the art. In addition, paper-impregnating techniques also are well known to those having ordinary skill in ~he art. Typically, a paper 0 is exposed to an excess of impregnating dispersion, run through a nip, and dried.
Turning now to the smooth antislip coating, such coating, regardless of the substrate, consists essentially of from about 80 to about 90 percent by weight, based on the dry weight of the coating, of cls-polyisoprene and from about 10 toabout 20 percent by weight, based on the dry weight of the coating, of thermally25 expanded microbeads having particle sizes before expansion in the range of ~rom about 5 to about 30 ~m. In general, the nature of the cis-polyisoprene is not known to be critical. If desired, the coating can include minor amounts of othermaterials, such as dyes, colorants, pigments, plasticizers, flow agents, antistatic agents, extenders, water repellents, surfactants, viscosity control agents, 30 dispersing aids, and the like.

~r rl3~3 Natural rubber, i.e., cis-polyisoprene. tends to be tacky in the uncured or natural state. It was both surprising and unexpected that tack was not observed - in the coating of the present invention. For reasons not fully understood, the presence of the expandable microbeads eliminated the otherwise natural tendency 5 for coatings of cls-polyisoprene to exhibit tack.
The coating also contains from about 10 to about 20 perceni by weight, based on the dry weight of the coating, of thermally expanded microbeads. The amount of such microbeads desirably is in the range of from about 5 to about 15 percent by dry weight, and more desirably is in the range of from about 8 to 10 about 12 percent by dry weight.
In general, the thermally expanded microbeads can be any of the commercially avculable microbeads, such as those sold under the Expancel~
trademark by Nobel Industries Sweden, Sundsvall~ Sweden, and those sold under the Foamcoat~ trademark by Pierce & Stevens Corporation, Buffalo, New York.
15 While any of the various types of thermally expandable microbeads can be employed, the more heat-resistant microbeads are desired.
The level of coating on a given substrate typically can range from about 3.7 to about 38 g/rn~. The level of coating desirably will be in the range of from about 5 to about 20 g/m2. It is neither necessary nor required, though, that the20 coating cover all of a sur~ace of a particular substrate. When the substrate is a paper which will serve as the backing for an abrasive layer, the coating typically will cover all of one surface. When the substrate is a nonwoven web or a laminate of two or more nonwoven webs intended for use as a surgical drape or a shoe cover, the coating typically will be applied only to a portion of the target 25 surface thereof.
The present invention is further illustrated by the example which follows.
Such example, however, is not to be construed as in any way limiting either the spirit or scope of the present invention. In the example, all parts are parts on a dry weight basis, unless stated otherwise.

2~7~7.~) Example A standard latex-impregnatecl paper was employed as the substrate. The basis weight of the paper be~ore impregnation was 52.6 g/m2. The latex saturant S consisted of 100 parts of Hyca~ 26322~ an acrylic polymer (B. F. Goodrich Company, (: leveland, Ohio), 2.3 parts of stabilizers, l .S parts of a water repellant, and 0.8 part of antioxidants. The saturant level in the paper on a dry weight basis was 35 parts per 100 par~s of wood pulp fiber. The basis weight of the impregnated paper was 71 g/m2.
The antislip coating consisted of 100 par~s of a commercially available cis-polyisoprene and 20 parts of Expancel~ 551WU microbeads, both on a dry-weight basis. The ~-polyisoprene was supplied as an aqueous dispersion or latex, to which the microbeads, supplied as a wet cake, were added. Water also was added to provide a final dispersion having about 40 percent by weight solids.
lS One surface of the paper was coated with the resulting dispersion, using a No.
24 Meyer rod. The coated paper was dried for one minute at about 107C and then was heated for 10-lS seconds at 145C to expand the microbeads. Both the drying and expanding steps were carried out in a ~orced air oven. The basis weight of the dried and expanded coating was about 15 ~g/m~. The resulting coating exhibited excellent nonslip characteristics and also was nontacky.
Having thus described the invention, numerous changes and modifications thereof will be readily apparent to those having ordinary skill in ~he art without departing from the spirit or scope of the invention.

Claims (8)

1. An article of manufacture comprising a substrate having a smooth, nonabrasive, nontacky antslip coating on part or all of a surface thereof, whichcoating consists essentially of (a) from about 80 to about 90 percent by weight,based on the dry weight of the coating, of cis-polyisoprene and (b) from about 10 to about 20 percent by weight, based on the dry weight of the coating, of ther-mally expanded microbeads having particle sizes before expansion in the range of from about 5 to about 30 µm, in which said substrate is selected from the group consisting of papers, films, and woven and nonwoven fabrics.

2. The article of claim 1. in which said article is a surgical drape hav-ing said coating on at least a portion of the body-side layer of said drape.

3. The article of claim 2, in which said surgical drape comprises a laminate of two or more layers of nonwoven webs.

4. The article of claim 1, in which said article is a shoe cover having said coating on at least a portion of the outer sole thereof.

5. An article of manufacture which comprises a paper having a first surface and a second surface, in which said first surface has a smooth, non-abrasive, nontacky antislip coating adjacent to and contiguous with said first surface, which coating consists essentially of (a) from about 80 to about 90 percent by weight, based on the dry weight of the coating, of cis-polyisoprene and (b) and from about 10 to about 20 percent by weight, based on the dry weight of the coating, of thermally expanded microbeads having particle sizes before expansion in the range of from about 5 to about 30 µm.

6. The article of claim 5, in which said paper is a latex-impregnated paper.

7. The article of claim 6, in which said second surface has a barrier coating adjacent thereto and contiguous therewith.

8. The article of claim 7, in which said barrier coating has an abrasive coating adjacent thereto and contiguous therewith.