CA2305890C

CA2305890C - Synthetic, water-based cohesive products

Info

Publication number: CA2305890C
Application number: CA 2305890
Authority: CA
Inventors: Paul Taylor
Original assignee: Andover Healthcare Inc
Current assignee: Andover Healthcare Inc
Priority date: 1997-10-31
Filing date: 1998-10-30
Publication date: 2008-01-15
Anticipated expiration: 2018-10-30
Also published as: EP1027084B1; DE69804988T2; TW396198B; ATE216268T1; DE69804988D1; WO1999022778A3; AU1290899A; EP1027084A2; AU744853B2; ES2177086T3; US6156424A; WO1999022778A2; CA2305890A1

Abstract

A cohesive product that has one or more layers of a substrate and a synthetic water-based cohesive polymer that is applied to the substrate and defines an outer surface of the product. The synthetic water-based cohesive polymer is an inherently crystalline elastomer whose polycrystalline structure has been disrupted such that the elastomer possesses a cohesive property.

Description

SYNTHETIC, WATER-BASED COHESIVE PRODUCTS

Thiti inventictn is ciirectecl tu cohesive prnclucts. and mor-c particularly to cohesive tapcs and handages, in which the cohesive material is a synthetic I U clastcrmcr rathcr than natural ruhhcr latex.

BACKGROUND OF THE INVENTION

Natural ruhhcr latcx is widely uscd in thc hcalthcarc inclustry, Crom surcical 15 <<loves to handa!-,cs. Because o1 the unique combination ol' stren2th, llexihility. and clasticity ul natural rilhber. il is t_ypicallv the matcrial o1"choicc l'or a varietv ol' nledreal pr()duct5. In particular, all known available cuhesive bandages are composed at lcast partly of' natural ntbhcr latex. Natural ruhhcr latex is inhcrcntlv cohesive, nicaninL, that it sticks tn it<Se11' rather than to other materials.
The 20 available adhesive handa7es that are entirely free of' natural rubber usc pressurc-sentiitive adhesivcs and are not cohesive.
A small hut signilicant sei-vment ol the population develops immediate or cielayed aller~~ic reactions to natural rubber. Recently. lhe United States Food and Dru:., Administration rulcd that all medical dcvices containinL, natural rubber latex 25 must hc labeled with warnings that the latcx can cause allergic rcactions.
This regulation was issucd amid morc than 1,700 rcports of' 5evcrc allergic reactions to lalex in medical devices that the FDA lias receivecl over the past decadc.
Proteins of' natural rubber latcx cause Is-,E-mcdiated sensitization in 30/t to 1817c ol health carc wor-kcrti and in up to 50'-7, crl' paticnts with spina biCicia. Scc Grillcr, M., Latcx 30 AllerLy, Lippincutts Primary Carc Practice 1(2):142-151 (1 y97 ;, It is bclieved that plant protcins remi:ininc in products made ol' natural ruhbcr latcx arc pOtential sensitizers. See Posch. A. et aL, Charactcrizatiun and idcntificatic~n of' latex allerLIenS by two-climensional clcctrophoresis and protein microseyuencinL,. J. Aller2)' Clin. Immunol.
99(3):385-395 (1997), A funhcr ciisadvantar~c rrf usinc natural ruhhcr latex instead etl svnthctic latcx alternatives is that natural ruhhcr latcx clci-,raclcS. particularly whcn exposed tu pctrOlcuni cicrivativc products such as pcuOlatum. ancJ animal lats. Synthetic latcxcs.
such as polychloropr-cnc, cxhihit an cnhancccJ chcmic.al resi.titancc. which natural ruhher 1O based Prcrclucts dtr ncrt possess.
Therc thus is a real and lunL-Stanciin~., nced tnr a cohcsivc.handaec 01-other product that is (rcc ol' and ttius avcridti lhe allcr2y-causinL protcins founcl in and Lhc petroleum-causccl dc(yradalions ol' natural ruhhcr latcx. yct still possesses the desirable ccthcsivc properticti ul natural ruhhcr. There is a particular necd lor I5 such.hantiages which cmplttv a svmthctiC clatitumcric cuhcai_vcthat_-like natural rubhcr latcx. is water-hased and can he cmploycd using procedures similar tO
those now widelv used in conncctictn with the manul"acturc oC natural nrbhcr latcx cohesivc handaLes.

Applicant has COund that there is a corrclation hctwecn the lcvcl ol' cohesion and the physical and chcmical Slruc;turc ol' an clastomcric pcrlymcr_ and that Lhc desirccl cohesive propenics lound in natural rubhcr arc largely due to Lhc 25 lact that natural nahher latex has a polycrystatlinc structurc.
Although motit synthctic elastomers and latcxcs cannol bC compoundcd to producc thc samc types of cohesion as natural ruhhcr, i.e.. compounding most synthetic latexes produces a pressure sentiitivc: adhesive. applicant has further discovered that similar cohcsivc propenics may he obtaincd hy compcrundin2 30 synthetic watcr-ha5ed claStomcrs lhat have perlycrystallinc structures similar tcr those ul natural rubber.

Accordingly, it is a primary object of the present invention to produce a cohesivc tape, bandage or other product that is free from natural rubber by utilizing the crystallization properties oi synthetic elastomers to produce synthetic water-based cohesivc polymers.

In one aspect, the invention provides a cohesive product comprising one or more layers of a substrate and a cohesive material in which the cohesive material is a synthetic water-based elastomer rather than natural rubber latex. The synthetic water-based cohesive polymer defines at least one outer surface of the product, and is usually applied to the substrate in such a way as to provide a cohesive surface on both the opposite sides of thc product.

In one embodiment of this aspect, this invention provides a product in which the synthetic water-based cohesive is an inherently crystalline elastomer to which at least one tackifying a=ent has been added in an amount effective to disrupt the crystalline structure of the elastomer and to maintain the elastomer in a partial crystalline state such that the elastomer possesses a cohesive property.
In preferred embodiments of this aspect, a tape/bandage or other substrate is coated or impregnated through the thickness of the substrate with a dispersion/emutsion of the elastomeric matrix before the water is evaporated (e.g., before drying), the cohesiveness of the synthetic elastomer is controlled by the addition of two tackifying agents with different melting points, or molecular weights, and the tape substrate material(s) is one or more of a woven or knitted fabric, a warp-knitted weft-insertion fabric, a non-woven material, paper, and a surface-treated polymeric.
Yet another aspect of the invention provides a method of modifying the cohesivencss of a synthetic water-based elastomer that is inherently capable of crystallization by :

(t) combining the synthetic water-based elastomer with at least one tackifying agent to produce a dispersion/emulsion ot the elastomer and tackifying SUBSTITUTE SHEET (RULE 26) agent(s). the tackifying agent(s) being present in the dispersion/emulsion in an amount effective to disrupt the crystalline structure of the elastomer and to maintain the elastomer in a partial polycrystalline state; and (2) evaporating the water from the dispersion/emulsion (typically by heat-treating the dispersion/emulsion) to produce a cohesive clastomeric solid.
Other objects, features and advantages of this invention will be apparent to those of ordinary skill in the art in view of the following Detailed Description, taken together with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a cross-sectional view of a first embodiment ol' the invention. in which a multi-layered substrate has been impregnated with a synthetic cohesive, water-based elastomer.

Figure 2 is a top view of the embodiment of Figure 1.
Figure 3 is a cross-sectional view of a second embodiment comprising a knitted substrate and a synthetic cohesive, water-based elastomer that is deposited on the opposite sides of a single laver of knitted substrate, such as by spraying or coating.

Figure 4 depicts the crystalline structure of an elastomer inherently capable of crystallization. Long chains of the elastomer come together to develop ordered structures in an otherwise amorphous mass of elastomer.

Figure 5 depicts the partial crystalline structure of an elastomer to which one or more tackitying agent has been added. Shorter chains of the tackifiers are shown interspersed with longer chains of the elastomer, disrupting the crystalline-like structures present in the elastomer by spreading the elastomeric chains farther apart. Although not as structured as the elastomer depicted in Figure 4, the matrix of elastomer and tackifier displays a level of structured, partial polycrystallinity.

SUBSTITUTE SHEET (RULE 26) 5 FiLurc 6 dcpictS an clasu>mcr whose crystallinc structurc has heen ctrmplctely disrupted hV thc presence ola rclativclv l;rrLc amrrunt trltackil-icr(s) resultinL' in an unordcrcd. anrotPhcrus masti with pressure-sensitivc prcrpertics.

DETAILEI) DESCRIPTION OF THE INVENTION

Relerrino niore particularly to thc drawin(-,s, Figure I is a cross-scctional view uC a tape/handaLe. *cnerally designated IQ, in which a substrate 20 has bccn impregnated through ttlc thickncss ot the substrate with a synthetic, cohesive, water-hascd clastorrrcr 30. The substratc 20 is ()l thc typc sold hy Andovct-Coatcd Products Inc. ol Salisbury. Massachusetts undcr thc tradcmark "POWERFLEX" and dcscrihcd in cupcndin L, U.S. Patent No. 5, 762 , 623 , f iled July 19, 1995. As described in this prior patent application, the suhstrate includes a plurality ol' longitudinally-extending elastic threads or yarns sandwiched hctween a laver oC a warp-knit (wclt-inscrtion) (abric and a laver ol' a non-woven iabric. In the prescnt embodiment. lhe cohesivc clastumcr 30 honds thc thrct;.lavers to2ethcr. The clastomer 30 also cxtends lully lhrough thc thickncss u( the suhstrate, so that thc top and bou.om surl'accs of the ovcrall tape-handa2c 10 are defined by the svnthetic clastomer 30. Figure 2 is a top vicw ot thc tapc bandage 20 ol Figure 1, cut away so as to better show each oC
the three layers ot the substrate 20.
Fi(-Turc ') is a cross-sectional view of a second tapc/banda~=e, generally dcsWmated 40_ in which a svnthetic. cohesivc, watcr-hascd clastomcr 50 has been coated or sprayed onto the: opposite sides ol a sin-le laver ol' a woven or knitted suhsu-atc 00. As with thc cmhndiment ol Fip-c I. it will hc reco2nizcd that ttic top and hottom surl'aces -12. 44 oC lhe overall tape/handa ge 40. are det'lncd by tlic synthetic clastomer. Since the substratc is only a tiin!~lc layer. however, the elastorncr is not reyuircd to bond a multi-laycr su-ucturc to!-,ether and nccd not cxtenci throui-,h the thickncss ol the suhstratc.

Because the synthetic elastomers 30. 50 of Figures 1 and 3, respectively, are cohesive, it will be recognized that the outer surfaces ot' the tapes 10, 40 of Figures 1 and 3, respectively, will stick to each other, e.g., the top surface 12 of tape 10 will stick to bottom surface 14 when the tape is wrapped around, for example, a user's ankle: and thc top surface 42 of tape 40 will similarly stick to bottom surface 44. However, because the synthetic elastomers are cohesive, rather than pressure sensitive, the surfaces of tapes 10, 40 will not stick (at least to any significant degree) to other surfaces or materials.
It will be recognized that substrates 20, 60 may hc made of any of a wide rangc of materials, and may have a wide range ol' structures. For example, any of the one or more layers of a substrate may be, for cxamplc. a wovcn, knitted, warp-knit (weft-insertion) or non-woven fabric, or paper. It may also be a surlacc-treated polymcric, such as a sheet of linear, low-density polyethylene ("LLDPE") or linear, low-density polypropylene ("LLDPP"), one or more surface ot' which has been treated to insure adhesion to the elastomeric cohesive. Similarly, the substrate structure may be elasticized, either as described above with reference to Figure 1, by knitting or weaving elastic threads into one or more of the layers, or by knitting or sewinr elastomeric threads through a single or multi-layer substrate.
In embodiments in which the cohesive product of the present invention is a tape or bandage, the substrate typically will comprise a woven, knitted, or warp-knit (weft insertion) fabric, or a non-woven fabric such as a non-woven scrim, of either natural or synthetic fiber. In one embodiment in this aspect, the substrate comprises a sinvle layer of a non-woven fabric wherein threads are knitted through the fabric and a synthetic cohesive, water-based elastomer is deposited on opposite sides oi' the fabric by, for instance, sprayina or coating. In a preferred tape/bandage, the substrates 20, 60 comprise nylon or polyester.
In anothcr embodiment of this aspect, the substrate of the tape/bandage comprises a first and a second layer of non-woven fabric and a third layer which is elastic in a direction extending longitudinally of the tape/bandage, said third layer being in between the first and second layers of non-woven fabric.

SUBSTITUTE SHEET (RULE 26) In a further embodiment, the substrate of the tape/bandage comprises: a first layer of warp-knitted (weft insertion) fabric oriented with the knit yams extending longitudinally of the tape/bandage: a second layer of a non-woven fabric: and a third layer which is elastic in a direction extending longitudinally of the tape/bandage, the third layer being between said first and second layers.
As discussed above, it is well known to make tapes/bandages similar to those shown in Figures 1 and 3 in which the cohesive material is natural rubber latex. In gen -cral, such tapes/bandages are made from a water-based emulsion of a natural rubber latex to which a tackifier has been added. The resulting iatex/tackitier structure is applied to the substrate (typically by saturating the substrate with the emulsion or coating the emulsion onto the opposite sides ol' the substrate), and the structure is then dried to produce the desired end product.
The tapes/bandages and other products of the present invention are preferably made using the same general manufacturing techniques, except that, as discussed below in more detail, the elastomer is a synthetic water-based elastomer rather than natural rubber latex, and different tackifiers and/or tackifier quantities are employed to enhance the cohesive property of the elastomer by disruption of the crystalline structure and to maintain the cohesive material in the desired partial polycrystalline state. More specifically, in the practice of the present invention. the synthetic cohesive end product is typically made by:
(1) combining a synthetic, inherently crystalline elastomer with at least one tackifying agent to produce a dispersion/emulsion of the elastomer and tackifying agent(s);
(2) providing a substrate of a desired structure;

(3) treating the substrate with the dispersion/emulsion such that the dispersion/emulsion defines at least one outer surface of the product: and (4) evaporating water from the dispersion/emulsion so that the dispersion/emulsion to produce a cohesive elastomeric solid.
As previously mentioned, it is well known that natural rubber latex can be cohesive. It has also been recognized that polyisoprene (natural rubber) is SUBSTITUTE SHEET (RULE 26) ~ inhcrently capahlc l)1 c1'VSLaIII%atJU11. Sct'_ Chcrcmisinclll. Nicholas P..
ed..
Handbook of' Pcrlvmer Science ancl TcchnolvLv 2:61-98 (19K9) ~

The crysLallinc 'u-ucturc of ccrtain pctlvmcric clatitOmerti is not a su-ucturc a,ti om,anized as a sin2lc crystal ctl*, fctr cxamplc. sodium chloride. huL rathcr is a plurality trC orcicr-ed SLrucLures in a mass ut amorphous pulymcr. As appiiccl Lu polymers. Lhe LerrnS cryStallinc, micrnerystalline. and polycrystalline reCer Lcl ordcrcd structures which dcvclup within a mass of' otherwisc amorphutrs polymeric material. CcrLain pOlvmers such as itiutactic polypropylene develop a highly urmnizcd micr-ocrvstallinc su-ucturc duc Lo thc inherent structurC rfC thc polypropylene. The tcrm microcrvstallinc. as used hcrcin, rcierti to ordcrcd strucLures that can he observed under magnilicatittn ol' thin lilnis of' pctlymer. Ttze term pctlycrystalline. as used hercin. means that many microcrystalliLCti are pretient in a mass of' Polymcr. As uscd herein, "inhercntly crystalline" or "inherently capable oi crystallization" mcans tttat a material exhibiLS a microcrystailinc, pctlycrystallinc. or crystallinc-likc structurc in a stablc. natural 1'orm.
In the case oC clastctmers such as natural rubhcr latcx. poly-cis 1. 4, 2-methyl butadicnc ( Poly cis- l_ 4 isoprcne). crystallinc structures develop in the othcrwisc amctrphcttrs mass of' natural ruhhcr. Thesc structurcti can hc cnvitiittncd tct develop where molcculcs in the mass ali2n them5clveS in a detinitc order as shown in Fioure 4. Re2ionti ol' order 5 amont, chains of clastomer 6 are hcld togclhcr by sccondary valencc lorccs producing a stren~nhenin2 of the ovcrall structure.
It has been knuwn ttlat thcsc structures can he disruptcd to agt'eatcr or ]csser extent by utic ol hcat. or a cumhinatictn of' hcat and tttc addition ol lowcr -molccular weiLht and/or lowcr meltin2 puint materials, oCLen relerred Lcl as "tackificrs" etr "tackilvin~~ aiTentti." These include l'or example. esters ol ahietic acid (rosin esters), ccrtain low-molccular weight hydrocarbon resinti usually rctcrred to as C;-Cõ pcllvmcrs, polymcrs with low Llass transitiun tcmpcratur-cs such as sonlc acrvlic polymers ancl sonie hutaeliene-stvrcne copolymerS, ancl cerLain nlonclmcric plasticizers. The structurc Ol thc natural r-uhher may bc disrupted hy blending cmc or more of the lower molecular wei~~ht and/or lower melting point materials listed above with the rubber polymcr, and then drying at room temperature or common drying temperature, i.c. at or above the boilint- point of the water carrier.
This disruption of the polycrystalline structures is illustrated by Figure 5, wherein the polymeric elastomer (natural rubber) chains I are represented by long lines and the tackifying resins 2 are represented by short lines.
As the result of extensive experimentation, applicant found that cohesiveness and crystallinity are related, i.e., that the cohesive property of natural rubber latex (and also of other inherently crystalline synthetic polymers as discussed below) depends on the natural rubber latex being in a stable crystalline-like state. Although the exact reason 1'or this relationship between crystallinity and cohesiveness has not previously been determined, it appears that the interaction of tackifiers and plasticizers with the natural rubber latex (and, as discussed below, also with inherently crystalline, synthetic elastomers such as polychloroprene) partially disrupts the polycrystalline-like structures, making them first cohesive and with increasing amount of tackitiers, pressure-sensitive. This disruption of the crystalline structure of the natural rubber latex by the tackifying a=ents causes the aligned structures to spread out, maintaining the latex in a partiallypolycrystalline state but without destroying the aligned structures entirely. Il' the amount of tackifier added to the rubber is such that the crystalline structures in the natural rubber are completely disrupted, the mass becomes amorphous and pressure sensitive, as shown in Figure 6. Long chains of the elastomer I and relatively shorter chains of tackifiers 2 are shown to exist as an amorphous mass lacking an ordered structure. If, on the other hand, there is a high level of ordered crystalline structuring in the natural rubber, the rubber becomes non-cohesive. These two extremes define a "window," within which the rubber has cohesive properties.
Applicant evaluated many synthetic polymeric materials which are not inherently crystalline, such as noncrystallizing polyurethanes, polyacrylates, butadiene styrene, acrylonitrile copolymer. carboxylated butadiene styrene, vinyl acetate acrylate copolymer, styrene acrylic copolymers, and acrylic polyurethanes.

SUBSTITUTE SHEET (RULE 26) lU
ancl touncl that none resulted in a cc~hcsivc watcr-basccl Product. Applicanl thcn locuscrl on Iinclin P polvmcrs which possess urVstallulc propcrtics similar tO
natural rubber. Tliis led to Lhe identitication ol two classes ul e:r-vslallii.in L, polvmerS, namcly watcr-hasecl polvchloroprcnc cmulsions such as polv-2 -chloro, 1-4 hutadicnc and certain watcr based pulvurethanes. that arc inhcrently capable of crystallization, i.c.. polyester pulyurethane ancl polycaprolactone polvurethane.
Applyin~, the knuwled-c gaincd in producin," cohesive clastomeric matcrials Crom nalural ruhher. applicant determined that one could ineleeel disrupt the crystallinity ol' thesc inhcrcntly ci-vstalline clastomeric pclymers and lhus hrin'~ them to, and arrest them in. a structure that haci a desired lcvCl 01 partial polyc:rystallinitv (c.(-,., throu<_,h thc use ul tackiNing resins): and that. likc natural ruhhcr latcx, thcsc synthctic inhercntly crystalline materials exhibit a cohesive property when Lhe degree ol' partial polvcrystallinity is maintainccl in a range (typically dctcrmincd empirically) bctwccn a completely amorphous statc and a highly crystallinc state.
The tackiCicrs used to produce cohcsivc Corms aC thcsc synthctic elastomeric matetials arc of the samc type uscd in connection with natural rttbbcr, althouLh Lhe amount(s) ol' any particular tackilicr(s) used to lorm a stahle cohcsivc will vary within empirically dclincci limits. Applicant lound that ttic window ()I' cohesiveness lor polychloroprenc is narrower than that ot' natural rubber latcx. As Lhe examplcs discussed bclow dcmonstratc, exceeding the limits produccs cithcr a non-cohesive or an amorphous pressure-scnsitive aclhesivc, ncither ol" which is usetu] Cur the present invention. Applicant also detcrmined that partially crystalline polychloroprcne was more stabic in a cohcsive statc than wcre inherently urvstallinc pulvurcthancs.
In prc(en-ed practiccs ol thc invcntion. thc inhcrcntly crystalline, watcr-based. synthctic elastomer is preierahly polvchloroprene, such as DuPont NEOPRENE'LTX-65=1, and thc tackiCvinL, resins uscd to arrest it in Lhe desired polvcrvstallinc statc are one or more ol' a rosin ester dcrivativc, a petrolcum derivative. a hvdrocarhon resin. an acrylic polymer, a hutadiene-hased polvmer or a comhination oC onc or more types such as rosin estcr/hvdroc:arhon resin.
*Trade-mark WO 99/22778 PCT/[JS98/23066 As used in the present invention, the terms "tackifier" and "tackifying agent" herein refer to a class of thermoplastic polymers used to affect the characteristics of a finished polymeric product and includcs the tackifying resins listed above, naturally occurring rosins, rosin esters, and plasticizers. As used in the present invention, the tcrm "rosin" as used herein refers to a naturally occurring material extracted from stumps of pine trees whose principal component is abietic acid. The term "rosin ester" as used herein, refers to the carboxyl group of abietic acid which has been esterified with aromatic and aliphatic alcohols. The term "hydrocarbon resins" as used hercin refers to lower-molecular-weight thermoplastic polymers derived from cracked petroleum distillates, tcrpcne fractions, coal tar, and a variety of pure monomers. Although a singlc tackifying resin can be used, blends of two or more with different melting points (and molecular wcights) have been found to produce cohesive products with better final properties. In some circumstances, plasticizers may be used in lieu of one or more tackifier resins.
Synthetic elastomers such as NEOPRENE LTX-654 and tackifying agents are commercially available in dispersion and emulsion forms.
When compounding the elastomer and tackifiers, there exists for each elastomer a "window" of compounding in which the structure of the polychloroprene or other elastomer is crystalline, and within which the deirree of crystallinity can be modified so that the material has cohesive properties.
The extent of the "window" varies depending on the particular elastomer, and is determined empirically. At one extreme of the "window," the elastomer becomes non-cohesive, and at the other extreme, it becomes pressure-sensitive. The state of the material within its "window" depends on the extent to which the polycrystalline structure of the polychloroprene or other elastomer is disrupted, and can be varied using different amounts and types of tackifying agents. For any particularly water-based inherently crystalline, synthetic elastomer, the amount and type of tackifier required to arrest the elastomer in a partially crystalline, cohesive state is SUBSTITUTE SHEET (RULE 26) i?
empirically tlctcrmincci. usin!_~ tackifiers and Ilrcltocc~ls sinlilar Lo thosc long employed in the Ilruductiun ol cohesive natural ruhhcr latcx materials ancl known to one ot skill in thc art.
When allplicd to a substrate so that it dclincs the Outcr surlaccs ol a product, awatcr-hased. svnthetic inhcrcntlv crystalline clastomer to which an lO ellectivc amount ul tackil-er has hcen added produces a cohesive llroduct which will adhere to itsclC, hut not (at least to any significant de~!rcc) to cnhcr suhstrates.
Thc tlllowin-, Examples will l'urthcr illustrate the invention. The Examples are not intended. and should not he interprcted, to limit the sct>pe uf the inventicln which is more fullv delincd in the claims which l'ullow.
IS
Example I
Prcnaratirm nl' Svnthctic Watcr-Bascd Elastomcric Products Elastomcrs. specitlcally llulychloroprene elastomers produced by DuPont under the namcs NEOPRENE LTX-654 and NEOPRENE*LTX-4()() sold in 20 dispcrsion or cmulsicln 1'orni. wcrc diluted with water Lo obtain apllroxinlatcly 5067c total solids pcr liquid wcight clatiwmcr mixturc. AL least one tackit'vini-, a!!ctlL UI' a2ents werc added Lo each elastomer mixturc and the mixture was suCYicientlv asntate.d at rrlclm tcmpcraturc Inr aPllrtlximatcly 15 minutcs Lo Ilrcuiucc a homtt'icneouti emulsion of' clastumcr. waLcr. and tackilyino a'*cnt(s). The 25 tackifyint avent(s) used were ro5in esLCr resins nr' a comhination ol' rosin cstcr and hydrocarbon resin. sold in dispersion or emulsion lotin as the Collnwint-,: 1-ierculeti TACOLYN107O (a rosin csLer resin), Hcrcules TACOLYN5OO1 (a rrtsin cstcr resin), Eka Nohcl'SNOTAK 78OG (a rc>sin cstcr resin). Eka Nohcl 342-B (a rttsin ~
cstcr rctiin'). and Neville Alliance PERMATAK H712 (a cttmhi.natian ol rclsin cstcr 30 resin and hvdrocancon resin). The TACOLYN 5001 and SNOTAK 78UG resins have hi~_her molecular wciOhls and mctting points (i.c.. melting point not lcss than about 80 C) than thc 342-B ancl PERMATAK*H712 resins (i.c. mclting point no mctrc Lhan ah0ut 70"C). A thickcninL aLcnt. c. i. ammclniunl IltllyacrVlatc sulutiun ur suclium polvacrylatc tiululion. was acidccl tcl thc humoLcncous enlulsicm and *Trade-mark agitated to produce an elastomeric material that has a viscosity of approximately 1000-150O centipoisc (cps).
It was found that the cohesive properties of polychloroprene were improved when two tackifying resins with melting points highcr and lower relative to one another were added to the polychloroprene. The best result.s using polychloroprene DuPont NEOPRENE LTX-654 were obtained with a higher melting point resin (approximately 85 C), Eka Nobel SNOTAK 780 (rosin ester resin), in an amount between 8 and 25% total liquid weight, preferably 18.6%, and a lower melting point resin (approximately 70 C), Neville Alliance PERMATAK H712 (a combination rosin ester resin/hydrocarbon resin derivative), in an amount between 4 and 10I7. total liquid weight, prcl'erably 7.9%.
The cohesive properties of the polychloroprenes were tested on a fabric, preferably a cotton cloth sheet laid on a flat surface, on which a bead of elastomeric material prepared as above was placed. A blade applicator, e.g.
UNIVERSAL blade applicator was calibrated to approximately 8-12 mm. The blade of the blade applicator was drawn across the surface of the fabric, smoothing and spreading the elastomeric material uniformly across the surface of the fabric at a thickness of approximately 8-12 mm. The fabric containing the elastomeric material was then dried at 117 C for approximately 2-5 minutes to produce the finished clastomeric product.
Determining Cohesive Bond Strength The cohesive bond strength of a tinished elastomeric product was determined by two methods: T-Peel test and shear bond test.

1) T-Peel Test:
Two strips oC the finished clastomeric product measuring l inch in width and of equal Iength, were placed face to face and a cylindrical weight was rolled across the surface of the superimposed strips. The two non-superimposed ends were clamped in the jaws of a tensile testing apparatus and pulled linearly in opposite directions pulling the two strips apart. The resistance of the superimposed strips to the movement of the clamps was measured in ounces/inch of width.
SUBSTITUTE SHEET (RULE 26) 2) Shear Bond Test:
Two strips of the finished elastomeric product measuring 1 inch in width and of equal length, were placed linearly so the end of one strip overlapped the end of another strip by 1 inch lengthwise. A cylindrical weight was rolled across the surface of the superimposed cnd of the two strips. The non-superimposed end of the two strips were clamped in the jaws of a tensile testing apparatus and pulled linearly in opposite directions. The strength of the shear bond of the superimposed ends was measured in lbs/sq. in.
The results of the T-Peel and the shear bond tests for DuPont NEOPRENE
LTX-654 with Eka Nobel SNOTAK 78()t', as the higher melting point tackifying resin and Nevillc Alliancc PERMATAK H712 as the lower meltin~* point resin, at'c given in Table I as follows:

Table 1 T-Peel: >25 ounces/linear inch of finished elastomeric material Shear bond: >25 pounds/square inch of finished elastomeric material Table 2 shows the cohesive property of tinished synthctic elastomeric materials using DuPont NEOPRENE LTX-654, for three different formulation ratios of Eka Nobel SNOTAK 780G, a rosin ester tackifying resin, as the higher melting point tackifying resin, and Neville Alliance PERMATAK H712, a combination rosin ester/hydrocarbon cesin derivative, as the lower melting point tackifying resin. The amount of elastomer and tackifier is measured as a percentage of total liquid weight of the clastomcr and tackifiers combined.
Table 2 Non- Lightly Very Cohesive. Ed ~t,e ~t:
Cohesive oh csive Cohesive Pressure Sensitivity SUBSTITUTE SHEET (RULE 26) 5 (Liquid Weight Parts per Hundred) Polychloroprcnc Latex:
DuPont NEOPRENE 100 88 73.5 65 Higher mclting point 10 tackifier: SNOTAK 780G 8 18.6 25 Lower melting point tackiCicr: PERMATAK 4 7.9 10 15 As summarized by Table 2, polychloroprcnc latex itscll', i.c., without any tackifier or plasticizer, is non-cohesive: a cohesive matcrial can he produced by adding one or more tackitiers, and the cohesive properties depend on the amount and type of tackiticr used. To produce a cohesive elastomer using DuPont NEOPRENE LTX-654, the amount of the higher melting point tackifier, Eka Nobel SNOTAK 780G, is preferably between 8 and 25 percent of total liquid weight and the amount of the lower melting point tackil'ier, Neville Alliance PERMATAK H712, is preferably between 4 and 10 percent of total liquid weight.

Example II
The cohesiveness of synthetic elastomers was modified by the addition of one or more tackitiers. The stable form of the elastomer is less crystalline than it would be without the addition ol' tackifiers. The addition of the tackificrs arrests the elastomer in a partial crystalline state that is Iess crystalline than its most favored crystallinc torm by virtue of the tackifiers spreading the crystallites present in the elast-omeric matrix farther apart.
Two examples of polychloroprenc were chosen for study. These were NEOPRENE LTX-40U and NEOPRENE LTX-654 from DuPont-Dow Elastomers.
LTX-40O is a fast crystallizing polymer and LTX-654 is a medium crystallizing SUBSTITUTE SHEET (RULE 26) polymer. The higher total solids contained in LTX-654 and the ease of tackifying it to achieve cohesive properties made LTX-654 the material of choice.
Various formulations of tackifiers and tackifier blends were analyzed with DuPont NEOPRENE LTX-654 and DuPont NEOPRENE LTX-400 as the synthetic elastomcr. The results of the series of experiments utilizing different kinds of tackifying resins with NEOPRENE LTX-654 and NEOPRENE LTX-4()0. and the cohesive property associated with each formulation is given below in Tables 3 and 4 for LTX-654 and LTX-400, respectively. Applicant determined that the window of cohesive properties available with the polychloroprenc is nari-ower than with natural rubber latcx. As shown in Tables 3 and 4, below, when properly compounded, the polychloroprenc latexes LTX-654 and LTX-40(} can be shown to exhibit one of the following cohesive qualities, depending on the amount of tackit7er used:
(1) Non-cohesive, that is, it does not stick to itself;
(2) Lightly cohesive, wherein it barely sticks to itself;
(3) Very cohesive, where it has aggressive self-adhesion without adhering to other substrates; and (4) Cohesive but bordering on the edge of pressure-sensitivity, wherein the material has aggressive self-adhesion and also adheres slightly to other substrates.
(5) Pressure-sensitive, wherein the material aggressively adheres to other substrates.
Good cohesion was achicved for formulations comprising LTX-654 and the tackifying resins, Eka Nobel SNOTAK 780G and Neville Alliance PERMATAK
H712, as measured by touch-testing. T-Peel and shear bond test results are also given where available.

Table 3:
Trial 1:
NEOPRENE LTX-654: 92.6%
Tackifier SNOTAK 780G: 7.4%
SUBSTITUTE SHEET (RULE 26) Cohesiveness: Non-cohesive Trial 2:
NEOPRENE LTX-654: 74.0%
Higher m.p. tackitier SNOTAK 780G: 17.0%
Lower m.p. tackitier PERMATAK H712: 9.0%
Cohesiveness: Cohesive. on the edge of pressure-sensitivity Trial 3:
NEOPRENE LTX-654: 73.5%r' Highcr m.p. tackifier SNOTAK 780G: 18.6%
Lower m.p. tackit'ier PERMATAK H712: 7.9%
Cohesiveness: Very cohesive Trial 4:
NEOPRENE LTX-654: 76.0%
Higher m.p. tackit'ier TACOLYN 1070: 16.0%
Lower m.p. tackitier PERMATAK H712: 8.0%
Cohesiveness: Cohesive, on the edge of pressure-sensitivity Trial 5:
NEOPRENE LTX-654: 79.4%
Higher m.p. tackiticr TACOLYN 1070: 13.7%
Lower m.p. tackiticr PERMATAK H712: 6.9%
T-Peel: 18 ozJlinear inch Shear Bond: 40 lbs/sq. inch Cohesiveness: Very cohesive Trial 6:
NEOPRENE LTX-654: 74.0%
Tackifier TACOLYN 5001: 26.0%
T-Peel: 56 orJlinear inch Shear Bond: 61 lbs/sq. inch Cohesiveness: Very cohesive Trial 7:
NEOPRENE LTX-654: 74.0%
Tackil'ier Eka Nobel 342-B: 26.0%
Cohesiveness: Pressure- Sensitive SUBSTITUTE SHEET (RULE 26) It is well-known that tackifying agents increase the level of adhesive strength of a polymer, or "tack," hence the name. and that increasing the amount of tackifying agent generally increases the adhesiveness. It is not well-known, however, how combinations of more than one tackifying agent may affect the overall property of a particular polymer or clastomer. Extensive research by applicant with natural rubber latex and polychloroprene has shown that good cohesion occurs when the tackifying agent(s) comprise roughly 20-30% total liquid weight. Using this range estimate of tackifying agent as a guide, applicant has identified the borderline between cohesion and pressure- sensitivity for various formulations ot' LTX-654 and LTX-4(H) and tackifying resins. Applicant was also able to determine that the cross-over from cohesion to pressure-sensitivity occurs rapidly, and that stable, cohesive properties were maintained successfully when tackifying resins compriscd about 20-25% of total liquid weight.
As shown by Trials 4 and 5, adding 13.7~'~ total liquid weight of Hercules TACOLYN 1070 and 6.9% total liquid weight of Neville Alliance PERMATAK
H712 (totalling 20.6% per total liquid weight of tackifiers) to LTX-654 resulted in an elastomeric product having good cohesion, whereas a formulation using 24%
total tackifier resins resulted in a cohesive product bordering on the edge ot' pressure-sensitivity. Similarly, as shown by Trials 6 and 7, adding 26.0% per total liquid weight of the resins Hercules TACOLYN 5001 and Eka Nobel 342-B to LTX-654 produced cohesive and pressure-sensitive elastomers, respectively.
Applicant was able to determine from these trials that the cross-over point between cohcsiveness and pressure- sensitivity was in this weight range.
Applicant also determined, howevcr, that simply increasing the total amount of tackifier does not necessarily result in an increase in cohesive strength.
As shown by Trial 2 ol' Table 3, adding 18.6% of Eka Nobel SNOTAK 780G and 7.9% Neville Alliance PERMATAK H712 (total amount of tackifying resins comprising 26.5% total liquid weight) resulted in a product exhibiting good, stable cohesion. As shown by Trial 3 of Table 3, when the amount of the higher melting point tackifying resin was reduced to 16% and the amount of lower melting point SUBSTITUTE SHEET (RULE 26) tackifier resin increased to 8.0% (total amount of tackifying resins comprising 24.0%), however, the resulting product was cohesive but at the edge of pressure-sensitivity. Thus. although a smaller amount of total tackifying resins was used, an increase in adhesive strength was observed.
This result can be explained by the fact that Lackifying agents with lower melting points ("lower m.p.") generally have a lower average molecular weight than tackifying agents with higher melting points ("higher m.p."). Thus, although the total amount of tackifying resins used in Trial 2 of Table 3 was greater than that used in Trial 3 of Table 3, there was also a lesser amount of lower melting point resin in Trial 2 for increasing the overall cohesive strength. On a molar basis, lower molecular weight resins are typically more el'tective in increasing the adhesive strength of a polymer than higher molecular weight ones.
Applicant's finding of the cross-over threshold between cohesiveness and pressure-sensitivity allowed applicant to produce for the first time, a synthetic water-based elastomeric cohesive. Applicant also determined that a formulation with substantially less than 20% total liquid weight of tackifying resins will produce a non-cohesive product. As shown in Trial 1 of Table 3, a formulation comprising only LTX-654 or LTX-400, or less than roughly 20% total liquid weight of tackifying resin resulted in a non-cohesive product.

Table 4:

NEOPRENE LTX-400: 80.0%
Tackitier TACOLYN 5001: 20.0%
Cohesiveness: Non-cohesive NEOPRENE LTX-400: 77.3%
Tackitier TACOLYN 5001: 22.7%
Cohesiveness: Cohesive; became lightly cohesive after 24 hours SUBSTITUTE SHEET (RULE 26) WO 99l22778 PCTlUS98/23066 5 NEOPRENE LTX-400: 72.5%
Higher m.p. tackifier TACOLYN 500 1: 23.5%
Lower m.p. tackifier PERMATAK H712: 4.0~'~
Cohesiveness: Cohesive: became lightly cohesive after 24 hours Experiments with LTX-400, a high chlorine content polychloroprene that readily and rapidly crystallizes in its stable form, demonstrated that cohesion is readily obtainable but that sustained cohesion is more difficult to achieve.
This is due to the strong tendency of LTX-4(H), by virtue of its many chlorine bonds, to revert to a highly crystalline state. It is believed that a stabie, cohesive product may readily be obtained by increasing the amount ol' total tackifying resins used.
Experiments directed to such are currently underway.
The various technical and scientific terms used herein have meanings that are commonly understood by one of ordinary skill in the art to which the present invention pertains. As is apparent from the foregoing, a wide range of suitable materials and/or methods known to those of skill in the art can be utilized in carrying out the present invention: however, preferred materials and/or methods have been described. Materials, substrates, and the like to which reference is made in the foregoing description and examples are obtainable from commercial sources, unless otherwise noted. Further, although the foregoing invention has been described in detail by way of illustration and example for purposes of clarity and understanding, these illustrations are merely illustrative and not limiting of the scope of the invention. Other embodiments, changes and modifications, including those obvious to persons skilled in the art, will be within the scope of the following claims.

SUBSTITUTE SHEET (RULE 26)

Claims

CLAIMS:

1. A cohesive product comprising a substrate and a synthetic water-based cohesive defining at least one outer surface of the product, wherein the synthetic water-based cohesive comprises an inherently crystalline elastomer and at least one tackifying agent in an amount effective to disrupt the crystalline structure of the elastomer and maintain the elastomer in a partial polycrystalline state such that the elastomer possesses a cohesive property.

2. The product of claim 1, wherein the product comprises a tape/bandage.

3. The product of claim 2, wherein said elastomer defines top and bottom surfaces of said tape/bandage.

4. The product of claim 2, wherein said elastomer impregnates through the thickness of said substrate.

5. The product of claim 2, wherein the substrate comprises one or more layers each of which is a woven or knitted fabric, a warp-knitted (weft-insertion) fabric, a non-woven material, paper, or a polymeric sheet.

6. The product of claim 5, wherein the non-woven material is selected from the group consisting of nylon and polyester.

7. The product of claim 5, wherein the woven or knitted fabric comprises an elasticized fabric wherein elastic threads are woven or knitted into the fabric.

8. The product of claim 5, wherein the polymeric sheet is surface-treated.

9. The product of claim 5, wherein the polymeric sheet comprises polypropylene.

10. The product of claim 2, wherein the substrate comprises a single layer of an elasticized fabric wherein elastic threads are woven or knitted into the fabric.

11. The product of claim 1, wherein said elastomer defines top and bottom surfaces of said substrate.

12. The product of claim 1, wherein said elastomer impregnates through the thickness of said substrate.

13. The product of claim 1, wherein the substrate comprises one or more layers each of which is a woven or knitted fabric, a warp-knitted (weft-insertion) fabric, a non-woven material, paper, or a polymeric sheet.

14. The product of claim 13, wherein the non-woven fabric is selected from the group consisting of nylon and polyester.

15. The product of claim 13, wherein the woven or knitted fabric comprises an elasticized fabric wherein elastic threads are woven or knitted into the fabric.

16. The product of claim 13, wherein the polymeric sheet is surface-treated.

17. The product of claim 13, wherein the polymeric sheet comprises polypropylene.

18. The product of claim 1, wherein the substrate comprises a first and a second layer of non-woven material and a third layer which is elastic in a direction extending longitudinally of the product, the third layer being in between the first and second layers of non-woven material.

19. The product of claim 1, wherein the substrate comprises:

1) ~a first layer of warp-knitted (weft-insertion) fabric oriented with knitted threads or yarns extending longitudinally of the product;

2) ~a second layer of a non-woven material; and 3) ~a third layer which is elastic in a direction extending longitudinally of the product, the third layer being between the first and second layers.

20. The product of claim 1, wherein threads or yarns are knitted through the substrate to form a knitted substrate, and the synthetic cohesive water-based elastomer is deposited on opposite sides of the knitted substrate.

21. The product of claim 1, wherein the synthetic water-based cohesive comprises an inherently crystalline elastomer to which two tackifying resins with melting points higher and lower relative to one another have been added in an amount effective to disrupt the crystalline structure of the elastomer, maintaining the elastomer in a partial polycrystalline state such that the elastomer possesses a cohesive property.

22. The product of claim 1, wherein two tackifying agents with average molecular weights higher and lower relative to one another are present in an amount effective to disrupt the crystalline structure of the elastomer and to maintain the elastomer in a partial polycrystalline state such that the elastomer possesses a cohesive property.

23. A synthetic water-based cohesive composition comprising an inherently crystalline elastomer to which at least one tackifying agent has been added in an amount effective to disrupt the polycrystalline structure of the elastomer and to enhance the cohesive property of the elastomer.

24. The composition of claim 23, wherein the inherently crystalline elastomer comprises polychloroprene.

25. The composition of claim 23, wherein the tackifying resins comprise one or more of a rosin ester derivative, petroleum derivative, hydrocarbon derivative, rosin ester/hydrocarbon derivative, a coal tar derivative, an acrylic polymer, or a butadiene-based polymer.

26. A method of modifying cohesiveness of a synthetic water-based inherently crystalline elastomer by:

(1) ~combining the synthetic water-based elastomer with at least one tackifying agent to produce a dispersion/emulsion of the elastomer and tackifying agent(s), the tackifying agents being present in the dispersion/emulsion in an amount effective to disrupt the crystalline structure of the elastomer and maintain the elastomer in a partial polycrystalline state; and (2) ~evaporating the water from the dispersion/emulsion to produce a cohesive elastomeric solid.

27. The method of claim 26, wherein the water is evaporated by heat-treating the dispersion/emulsion.

28. The method of claim 26, wherein the tackifying agents are two tackifying resins with melting points higher and lower relative to one another.

29. The method of claim 28, wherein the higher melting point resin is a rosin ester resin, and the lower melting point resin is a rosin ester/hydrocarbon resin.

30. The method of claim 28, wherein the amount of the higher melting point resin is between 8 and 25 percent of total liquid weight of elastomer and tackifying resins.

31. The method of claim 28, wherein the amount of the lower melting point resin is between 4 and 10 percent of total liquid weight of elastomer and tackifying resins.

32. The method of claim 26, wherein two tackifying agents with average molecular weights higher and lower relative to one another are added to the elastomer.

33. A method of making a synthetic cohesive product comprising the steps of:

(1) ~combining a synthetic water-based elastomer with at least one tackifying agent to produce an emulsion/dispersion of the elastomer and tackifying agent (s) ;

(2) ~providing a substrate of a desired structure;

(3) ~treating the substrate with the dispersion/emulsion such that the dispersion/emulsion defines at least one outer surface of the product; and (4) ~evaporating water from the dispersion/emulsion to produce a cohesive elastomeric solid.

34. The method of claim 33, wherein said substrate is a woven fabric, a knitted fabric, a non-woven material, paper, or a polymeric sheet.