CA2069172A1

CA2069172A1 - Release liner

Info

Publication number: CA2069172A1
Application number: CA002069172A
Authority: CA
Inventors: Michael A. Johnson; Maurice H. Kuypers
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1991-06-17
Filing date: 1992-05-21
Publication date: 1992-12-18
Also published as: JPH05194919A; ES2106140T3; DE69221782T2; AU645424B2; MX9202913A; EP0519611A3; US5178924A; AU1700892A; DE69221782D1; EP0519611B1; EP0519611A2; KR930000262A; BR9202232A

Abstract

ABSTRACT

A release liner comprising:
(a) a reinforced, non-woven sheet composite comprising two layers, one of the layers being composed of a plurality of substantially randomly orientated fibers and the other layer being composed of substantially lineally aligned fibrous reinforcement material; and (b) a release layer on one or more of the layers of the non-woven sheet composite, the release layer comprising at least one of the following:
an olefinic homopolymer, an olefinic copolymer, or a copolymer of an olefin and a polar comonomer.

Description

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RE~EA~ R

Field of the Invention This invention rela1:es to a release liner and, more particularly, it relates to a ~iber-rein~orced release liner for pressure-sellsitive adhesivesO

Back~round of the Invention Currently, many tapes and ~ther pressure-sensitive adhesive-coated articles have a release liner applied to the adhesive during or following manufacture.
The release liner is typically le~t in place while the article is laminated, converted, packaged, and shipped to 15 ultimate users, and in many instances is left in place until the article is bonded to an adherend with the pressure-sensitive adhesive. Release liners are often used for one or more of a number of purposes, including, for example, preventing contamination of the adhesive 20 layer, facilitating handlin~ of the adhesive-coated article (e.g~, by providing support thereto as well as covering the adhesive), identifying the articles to which they are applied, providing roll stability of articles such as tapes when wound into rvll form, etc.
The state-of-the-art in release liner technology for ultra high performance acrylic pressura-sensitive tapes is polyethylene or polypropylene films.
These films have been successfully used for many years ~-~ because they do not re~uire a release coating (e.g.
30 silicones) and can be formulated to possess sufficient stiffness (secant modulus) to support the tape construction through processing, converting,~ and ~; lamination. Secant modulus has been used for years to predict the processability of a particular liner/tape 35 construction. It relates to the initial stiffness of a film and indicates the ability of a ~ilm to support a pressure-sensitive tape through all aspects of processing.
As applications have evolved, conventional polyolefin-based release liners have not been capable of 5 supporting the tape construction sufficiently to avoid stretching the tape during the manufacturing or lamination processes. Conv~entional liners exhibit a yielding behavior that allo~s the tape to stretch or elongate by as much as 12+% during the lamination phase lO of manufacturing. This amolmt of stretch is a major contributor to liner pop-off in low modulus, pressure-sensitive tape constructions. Strain induced pop-off results from a differential level of stress between the pressure-sensitive tape construction and the polyolefin 15 release liner. In addition to liner modulus, time, temperature, handling, and packaging all contribute to the pop-off problem.
What is needed in the industry is a release liner which greatly minimizes and/or eliminates the pop-20 off problem and which controls the stretch of the tape during manufacturing operations subsequent to the lamination of the tape to the release liner.

Summary o the Invention By the present invention, Applicants have discovered a release liner construct.ion that minimizes or eliminates the pop-off problem during the processing and laminating phases of the tape manufacturing process and which controls the amount of stretch placed on the tape 30 during application.
In one embodiment, the inventive release liner compxises: ~a) a reinforced non-woven sheet composite comprising two layers, one of the layers being composed of a plurality of substantially randomly orientated 35 fibers and the other layer being composed of substantial:Ly lineally-aligned fibrous reinforcement material; and (b) a release layer on one or more of said . .

l3 1 V1 2 layers of said non-woven sheet composite, said release layer comprising at least one oE the ~ollowing: an olefinic homopolymer, an olefinic copolymer, or a copolymer o~ an olefin and a polar comonomer. The sheet 5 composite and release layer are typically substantially co-extensive over at least that portion of the liner which is contacted to the adhesive coated portion o~ the article to which khe release liner is applied.
In another embodiment of the present invention, 10 the reinforced non-woven sheet composite comprising three layers such that one layer o~ ubstantially lineally aligned ~ibrous reinforcement material i5 positioned between two layers of substantially randomly orientated fibers.
As disclosed herein earlier, the inventive release liner exhibits minimal elongation during tape processing and manufacturing. Accordingly, the inventive release liner greatly minimizes and/or eliminates the release liner pop-off problem. Additionally, the release - 20 liners of this invention can provide effective protection against contamination of the underlying adhesive layer.
Other aspects, advantages, and bene~its of the present invention are apparent from the detailed description, examples, and claims.
Detailed Description o~ the Invention The support sheet utilized in the release liner of the present invention is a non-woven, reinforced sheet -composite comprising two fibrous layers. The inventive 30 support sheet may also comprise three layers.
The support sheet typically substantially defines the overall strength characteristics, e.g., secant modulus, tear strength, 1exibility, extensibility, tensile strength, etc., of the relP-ase 35 liner. During fabrication o~ the release liner, the support sheet should be able to with tand the stresses necessary for formation of the release layer thereon.
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2 ~ 2 Further, a typical application o~ release liners o~ the invention is on adhesive tapes and articles wherein release liners may be subjected to substantial stresses, for instance when drawn through processing equipment S during fabrication of an adhesive tape, during storage and shipm~nt o~ the tape, or during application of the tape to a substrate.
In many instances, the support sheet will preferably provide, without breaking, a tensile force o~
10 at least about 1.0, typically more preferably at least about 1.5, pound/inch-width at a strain or elongatisn of about 1 percent. Depending upon the application for which the release liner is being prepared, support sheets which provide lower tensile forces may be useful or 15 support sheets which provide higher tensile ~orces may be desirable.
Typically, a release liner will be subjected to tensile stresses during use and it may be desired for the liner to elongate to some extent. ~owever, in some 20 embodiments of the invention, it will be preferred that the support sheet have an elongation of 5 percent, and most preferably 10 percent, i.e., it can be elongated to that extent without breaking. The maximum desired elongation for a particular embodiment of release liners 25 of the invPntion will be substantially dependent upon the intended application.
It is preferred, however, that the support sheet retain sufficient structural integrity to impart dimensional stability to the release liner and, for 30 example, the adhesive-coated article, when it is elongated. For instance, in applications where release liners of the invention are used on foam-like adhesive tapes such as are used on weather stripping and body side moldings for automobiles, it may be preferred that the 35 support sheet have a tensile force of at least about 7 pounds/inch-width at an elongation of about ~0 percent.

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The support sheet is pre~erably substantially non-yielding such that when the release liner is stretched and the tensile forces released, it will tend to recover at approximately the same rate at which a 5 stretched, highly elastic adhesive-coated article recovers [and cause stretchi]ng of the release layer or adhesive-coated article to which the release liner is attached].
The support sheet utilized in the release liner 10 of the present invention is non-woven, e.g., a non-woven web. An advantage of support sheets having holes and interstitial voids therein is that the polymeric material of the release layer may penetrate into, and in some instances penetrate substantially through and saturate, 15 the web. Such penetration typically results in mechanical, as well as adhesive, fastening of the support ~heet and release layer, providing a firmer bond therebetween than is provided by interfacial adhesion alone. The non-woven fibers axe also bonded integrally 20 within the non-woven matrix. The resultant release liner thus exhibit3 greater resistance to delamination with easier startability of removal typically being provided~
~; Non-woven materials are utilized because they typically tend to be dimensionally deformable to a 25 limited degree, but tend to resist yielding at low loads, such that the release liner will remain securely bonded to the adhesive layer when small stresses are applied ther~to. For instance, non-woven webs pro~iding a force of at least about 7 pounds/inch-width at an elongation of 30 about 20 percent are useful as support sheets in release liners of the invention for many applications.
T~pically, as the basis weight of non-woven webs is increased, the force they provide at a specified strain or elongation increases. Thus, non-woven webs may be 35 easily formulated to provide support sheets for liners of the invention having desired properties. Illustrative examples of non-woven webs which may be used herein , , .

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include spun-bonded, point-bonded, air-laid, dry-laid, wet-laid, thermally-bonded, and resin-bonded webs. The webs are preferably thermally bonded. Web~ can be thermally bonded by applying pressure on the web as ik is 5 pulled through a heated calendar roll nip.
The support sheet is typically between about 2 and about lS mils (50 and 37'i microns~ thick. It will be understood that support sheet:s having thicknesses outside this range may be used, however, those which are 10 excessively thin may tencl ts provide insufficient strength and thus be subject to structural failure, e.g., tearin~ or splitting, whereas those which are excessively thick may tend to be undesirably stiff. The reinforced sheet has a relatively high modulus for the basis weight 15 of the sheet.
One layer of the support sheet is composed of a plurality of substantially randomly orientated fibers, preferably organic fibers. As used herein, the term "substantially randomly orientated layer of fibers"
20 ref~rs to a layer of fibers wherein each fiber lacks directionality to the degree that there is no principle order to the individual fibers in the defined layer. It is a random mix o~ tangled, diverging, convoluted fibers in a three-dimensional shape. Illustrative examples of 25 such organic fibors that support sheets may be made from include one or more of the following: nylon, polypropylene, polyethylene, polyester, acrylic, cellulosic derivative (e.g., cotton fabric, rayon, acetates, or butyrates), etc. Preferably, the fibers are 30 coextruded to create a sheath/core construction that allows the sheath to act as an adhesive to bond the fibers together and ultimately create a smooth back~ace surface on the release liner. The smooth backside is of particular importance when it is desired to attach a tab 35 on the liner for easier removal. Since the non-woven ~ibers are bonded well to each other and the release coating, the tab rerains adhered to the liner when it ie :;
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pulled off, instead of pulling o~f loos~ fibers and leaving the release liner on the adhesive.
The other layer o~ the non-woven reinforced sheet is composed of substantially lineally aligned 5 fibrous reinforcement material, preferably organic reinforcement material. As used herein, the term "substantially lineally aligned fibrous rein~orced layer"
refers to an ordered layer of individual fibers which possess parallel characteristics with respect to 10 neighboring fibers contained in the layer. Examples of such fibrous reinforcement material include, but are not limited to, glass yarns, polyester yarns, polyethylene yarns, polypropylene yarns, glass matts, woven fibers, scrims, etc. Usable fibers are larger in diameter than 15 the fibers used to form the non-woven. Preferred fiber sizes are 50-500 denier and more preferably, 100 to 300 denier.
Preferably, the release liner is free of agents which tend to impair performance of the adhesive coating 20 to which they are applied. For instance, many plasticizers may undesirably affect the adhesion properties of pressure-sensitive adhesives. Also, agent~
such as silicones may interfere with the adhesive coatings or may contaminate substrates, e.g., automobile -- 25 body parts that are to be painted. Accordingly, the support sheet i5 substantially free of migratory plasticizers and silicones to avoid adverse interaction with the pressure-sensitive adhesive layer to which the release liner is contacted.
The release layer imparts to the release liner desired surface adhesion and release characteristics with regard to adhesive coatings to which the liner is to be applied. It also functions to create a coherent surface to which the pressure-sensitive adhesive can be 35 laminated. Preferably, the release layer is substantially continuous such that the support sheet will avoid extensive contact with the adhesive coating to which the release liner is to be applied.
The release layer typically compris~s one or more of the following: an olefinic homopolymer or 5 copolymer, or a copolymer of an olefin and at least one polar comonomer, or blends thereof.
Some illustrative examples o~ homopolymers and copolymers that may be used in the release layer o~ the release liner of the invention include, but are not 10 limited to, butylene; isobuty3ene; high, medium, low, and linear low density polyethylene; ethylene vinyl acetate;
ethylene acrylic acid; ethylene methyl (meth~acrylate;
ethylene butyl acrylate; polypropylene;
ethylene/propylene copolymers; and impact resistant 15 ethylene/propylene copolymers. For applications wherein shock resistance at very low temperatures, e.g., below -20C, is desired, copolymers of ethylene are preferred as they typically exhibit greater shock resistance at low temperature.
In some instances, release liners of the invention may further comprise an optional friction-enhancing agent on the major sur~ace of support sheet opposite the major surface on which the release layer is disposed. In applications where the release liner is ~o 25 be used on an adhesive-~oated article such as dual-functional tape, e.g., coated with a tacky pressure-sensitive adhesive on one side and a tack~free heat-a~tivated adhesive on the other side which is wound into roll form, the back surface of the support sheet will be 30 wound into contact with the heat-activated adhesive-coated side of the tape. If the support sheet and tape exhibit low friction, they may tend to move reely, resulting in poor roll stability. In such instances, it may be desired to select the support sheet from materials 35 as described above which inherently exhibit desired ; friction wit:h the tape, or to treat the support sheet to increase friction to desired levels, e.g., by applying .~ ' .

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the friction-enhancing agent thereto. ~uch agent may be applied in the fnrm of a substantially continuous layer or may be selectively applied in pattern fsrm.
Illustrative examples of such agents include 5 ethylene/acrylic acid mixtures containing tackifiers which provide improved perormance when applied to polyethylene support sheets for use on release liners used with tapes with back sides made o~ olefin-based, very low tack heat-acti~ated adhesives.
The release liner can also be used as a carrier for an adhesive trans~er tape wherein a pessure-sensitive adhesive is coated onto the liner, cured, and rolled up on the liner. The smooth backside serves as a dif~erential release liner so that the tape can be 15 unrolled.
The following non-limiting examples further illustrate the present invention. Unless otherwise indicated, the following test procedures were used in the Examples.
TEST PROCEDURES
~ensile Force A 1.27 cm x 17.5 cm sample of the subject release liner is elongated in an INSTRONTM tensile tester 25 or equivalent extension tester with a jaw separation o~
12.7 cm and a crosshead speed of 1.27 cm per minute. The force at up to 20 percent elongation of the sample is recorded at the specified elongations. The release liner can also be laminated to a tape construction and the 30 composite is tested as describPd above.
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~- Peel Adhesion A sample is prepared by laminating the release side or surface of the subject liner to an adhesive tape 35 and cutting out a 2.5 cm x 17.5 cm strip. The liner is pulled away from the adhesive tape for a distance of about 10 cm on an INSTRONTM tensile tester or equivalent !

~6~2 test~r at an angle of 180 degrees and a crosshead speed of 30 cm/minute. The force required to remove the liner i~s measured in Newtons/decimeter. Samples are tested immediately after lamination of the liner to the adhesive 5 tape; after one and four weeks of aging at room temperature (about 20~C) and at 70C~

Cold Temperature Performance The release surface~ of a 1.27 cm wide strip of 10 the subject liner is adhered to a 1.27 cm wide strip of Y-4234 Weatherstrip Attachment Tape (available from 3~).
The exposed side o~ the tape is then heat-bonded to a flat 2.54 cm wide strip o~ EPDM (ethylene propylene diene monomer) rubber profile extrusion test strip available 15 from Cooper Rubber Company. The strip is cut into 25.4 cm long strips and placed in a -40C chamber for 24 hours. The Stage 1 test is conducted by holding a sample strip at each end and twisting 180 degrees along the axial length of the sample. If no pop-off of thP liner 20 is observed, the Stage 2 test is conducted. In Stage 2, the same strip is rotated for another 180 degrees for a total twist of 360 degrees. If no liner pop-off is observed, the Stage 3 test is conducted. The strip is untwisted and formed into a circular loop with the liner 25 on the inside o~ the loop and observed for liner pop-off~
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Tear Resistance A 5.08 cm by 15~24 cm sample is cut with 30 the 5~08 cm dimension being the minor axis and the 15.24 dimension being the major axis. The major axis is the test direction (down web or crossweb). A 1.9 cm notch is cut from one edge at the middle of the minor axis and parallel to the major axi~ of the sample. The sample is 35 placed in an INSTRONTM tensile tester having a 2.54 cm jaw separation such that the notch is positioned in line with the jaws.

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The jaws are separated at a speed of 12.7 cm per minute and the average force required to tear the sample is recorded. Samples are run in both the downweb direction and the crossweb direction.

Nonwoven Web A
A nonwoven web was dry air laid on a Rando-Webber nonwoven forming machine (obtained from Rando Corp.) using 80 parts of a 1.2 denier x 3.8 cm 10 polyethylene terephthalate fiber (TREVIRATM T-121 fiber from Hoechst Celanese Corp.) ~nd 20 parts of a 2.0 denier x 5.1 cm sheath core polyester ~iber (CELBONDTM K-54 fiber from Hoechst Celanese Corp.) to a basis weight o~ about 17 grams per square meter. Multifilament yarns (220 15 denier Type 68 DACRONTM polyester yarn from DuPont Company), set at 20 ends per inch, were then laminated to the nonwoven web using calender rolls set at 275F. The resulting nonwoven web had a basis weight of about 40 grams per square meter. The nonwoven web had tensile 20 strengths at varying elongations as shown in Table 1.

Nonwoven Webs B and C
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Nonwoven webs were made as Nonwoven Web A
except that Web B had 65 parts of T-121 fibers and 35 25 parts of K-54 fibers. Web C had sn parts of T-121 ~ibers and 50 parts of K-54 fibers.

Nonwoven D
A nonwoven web was made with the same nonwoven 30 composition as Nonwoven C, but 150 denier yarns were laminated to the nonwoven web. The nonwoven web was formed on a standard carding machine made by ~ergeth.
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Nonwoven Æ
A nonwoven web was made as Monwoven D without the 150 denier yarns.

Ten~ile Strenath (Nldm~ at Elonqation (%Ls~own Web ~ 2% 5% 10% 15% 20%

A lO1 195 329 677 663 break B 141 221 357 701 694 break C 137 237 420 834 769 k~k 20 ExamPles 1-3 and Comearatives C1 - C2 The nonwoven webs A, B, and C, described above, - were used to make release liner Examples 1, 2, and 3, respectively. The release liners were made by extruding 25 onto the nonwoven web a 0.076 mm thick layer of resin having 96 parts ethylene vinyl acetate (EVA) and 4 parts of a red pigment (Techmer S-20870E10 pigment from Techmer PM). The FVA was ELVAXrM 265 ethylene vinyl acetate from DuPont Co. The re~in was extruded onto the yarn side of 30 the nonwoven at a melt temperature of about 190C~ The liners were tested for tensile force and the test results are shown in Table 2.
Comparative Cl was made as described above usiny a 34 grams/square meter CEREXTM nylon nonwo~en available 35 from Fiberweb North Amerira.
Comparative C2 was a 0.1 mm thick multi-layer ~; polyethylene construction having a 0.018 mm thick layer of high density polyethylene (CHEMP~EXTM S109 polyethylene 40 from Quantum Chemical Corporation), a 0.07 mm thick layer of medium dlensity polyethylene (60/40 blend of the high and low den~sity polyethylenes respectively), and 0.018 mm - 13 ~
low density polyethylene (MORCHEMTM 353 poly~thylene ~rom Quantum Chemical corp.).
The test results show that the liners of the invention have an increasing tensile strength up to 20%
5 elongation. Tha signi~icance of the increasing tensile strength is that tha liner rer-;ists stretching and that it requires an increasingly higher tensile fsrce to cause the liner to stretch. By comE\arison, Example Cl exhibits increasing tensile force but its resistance force is 10 significantly less than the inventive materials.
Comparative Example C2, without the reinorcing yarns, increases in tensile force up to a certain amount of elongation after which the tensile strength levels of~
and 15 the liner no longer resists stretching. At that point, it requires relatively low tensile force to cause a large amount of stretching in the liner construction.

Ex- Tensile Strenqth (N/dm~ at Elonqation (%)shown am-1% _2~ 5% 10%15% 20%
25 1 143 2~2382 7741172 1384 2 150 246398 8191150 break - 3 162 261431 8791190 break C1 4~ 66 105 15319~ 230 ~2 59 90 131 14714i8 1~5 . ~

The release liners of Examples 1-3 and Comparative C1 and C3 were laminated to Y-4234 Weather-strip Attachment Tape. The composite comprising the tape and 40 the liner were then tested for tensile strengths at various elongations and the data are shown in Table 3.

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Ex- Tensile Strength (N/dm? at Elon~tion (%)shown am-5 ple 1% _~ 5% 10% 15~ 20%
1 148 250 402 764 1166 ~378 ~ 1~3 283 ~55 876 1250 1430 C1 71 98 153 21~ 261 300 ` 15 C3 86 133 196 229 ~38 ~40 : 20 Examples 4-11 Ethylene-containing resins (shown în Table 4) were coated onto Nonwoven Web D at a thickness of 0.1 mm.
25 The ethylene-containing resins had 4 parts of red pigment and were extruded according to the processing conditions described in Example 1. The liners were tested for ~: tensile force at various elongations and results are ~shown in Table 5. The results show that the tensile : 30 strength increases on a positive slope up to 20%
elongation and resists stretching, instead of leveling off at a low elongation, thereby permitting little resistance to extensive stretching as shown by ComparatiYe C3. Comparative C3 was made with Nonwoven 35 Web E.

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Resin Trade Percent Percent Example ~ 9L-tion Vinyl acetate crylic Acid 5 4 ELVAX 265* 28 ---6 E~VAXTM 360 25 ___ 7 ELVAXTM 460 18 ~
8 E~VAX 560 15 ---ELVAXTM 760 9.3 ___ 11 DFDA-1137** 0 ---_ *All ELVAXTM resins are ethylene vinyl acetate resins are from DuPont Company.
~5 **DFDA-1137 polyethylene is a linear low density polyethylene available from Union Carbide Coxporation. No pigment was used in this Example.
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, , Ex- Tensile Stren~th (N/dml ~t El~.Lshown am-5 ~1~ 1% ~ 5% 10% 15~ ~0~

4 ~3 141 20~ 292 3~7 418 77 138 ~ 29~ 36~ 420 15 8 70 12~ 195 268 345 397 9 6~ 123 187 25~ 321 346 C3 30 ~8 74 101 72 73 The liners of Examples 4-11 were laminated to Y-4234 Weather-strip Attachment Tape at room temperature and tested for adhesion and adhesion buildup after heat : 30 aging. The test results in Table 6 show that adhesion does not build excessively over time.

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Ex _ _ Release Force - ~Lams/25 ]mm width __ am- Room Temperat~re 158 4C
ple Initial lweek weeks lweek 4weeks 4 154 163 153 79g 740 490 56~ 595 1802 1244 7 16~ 150 177 277 295 ~ 141 163 182 127 132 336 1~5 168 1~1 222 . ~

The liner~ of Examples 4, 5, 7, 10, and ll were laminated to the Y-4234 Attachment Tape at about 95C.
Test results ~or adhesion are shown in Table 7. The results show that adhesion does not build to excess when 30 the liner is used, i.e., laminated, at elevated temperatures. Example 5 contains acrylic acid in the EVA
formulation which causes the adhesion of the liner to the adhesi~e to build slightly.
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2 ~ 2 Ex Release F~s~ m~/25 mm width am- Room Temp~rat~re 158C
Initiallweek weeks lweek 4weeks 4 ~90 336 5~3 ~4 790 704100~ 1.930 790 2438 10 7 209 204 204 304 31~

11 331 2~6 295 Z45 250 The liners o~ Examples 4-11 were tested for cold temperature adhesion. Results in Table 8 show that the 20 amount of vinyl acetate is preferably above ~2% for keeping the liner adhered to the adhesive at cold temperature extremes.

TAB~E 8 25 Example Staqe 1 Staqe 2 Staqe 3 4 pass pass pass pass pass pass 6 pass pass pass 7 pass pass ~ail 30 8 pass pass fail 9 pass fail :: 10 fail 11 pass fail ----.
Exam~le 12 A release liner was made by extruding a 0.025 mm thick layer of ethylene vinyl acetate (ELVAXI~ 265 ~V~) onto a nonwoven laminated to a polyester scrim. The 40 nonwoven laminate (available from Nylco Corporation, Nashua, NH) was a 12 grams per square meter REEMAYTM
polyester nonwoven (available from Reemay Company) and , ~:

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was l~minated to a ~416 scrim (6x6 polyester scrim ~rom Nylco Corp.). The ~416 scrim had rectangular openings averaging 5mm by 3 mm in dimension.
The sample was tested for tensile force at 5 various elongations and the results are shown in Table 9.
The data shows that there is increasing resistance to elongations up to 20% elongation.

10 Ex- Tensile Strenqth (N/dm) at Elonqation (%! shown am-ple ~% 2% 5% 10% ~ 20~

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Example 12 was compared to Example 4 for tear 20 resistance. The data in Table 10 show that Example 12 had a higher resistance to tearing than Example 4, notably in the downweb direction.

Tear resistance - Newtons Example Downweb Crossweb `~ 4 3 8 . .
Lamination induced stretching was evaluated using a TS-510 taping head (available from 3M). Tape was bonded to a standard rubber cross-~ection using sample Example 4 and Comparative C2 in contact with Y-4234 tape.
35 Example 4 exhibited 200% stretch in comparison to 5%
stretch observed for C2. Stetching was evaluated by measuring 10" increments onto tape, applying the tape, and measuring the length after bonding. % stretch is the difference :in length divided by the original length of 40 tape.

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Reasonable variations and modif ications are possible from the foregoing disclosure without departing from either the spirit or ~cope of the present invention.

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Claims

1. A release liner comprising:
(a) a reinforced, non-woven sheet composite comprising two layers, one of the layers being composed of a plurality of substantially randomly orientated fibers and the other layer being composed of substantially lineally-aligned fibrous reinforcement material; and (b) a release layer on one or more of said layers of said non-woven sheet composite, said release layer comprising at least one of the following: an olefinic homopolymer, an olefinic copolymer, or a copolymer of an olefin and a polar comonomer.

2. A release liner according to Claim 1 wherein said reinforced non-woven sheet composite comprises three layers such that one layer of said substantially lineally aligned fibrous reinforcement material is positioned between two layers of said substantially randomly orientated fibers.

3. A release liner according to Claim 1 wherein said sheet composite has a tensile force of at least about 1 pound per inch-width at an elongation of about 1 percent.

4. A release liner according to Claim 1 wherein said sheet composite has a tensile force of at least about 1.5 pounds per inch-width at an elongation of about 1 percent.

5. A release liner according to Claim 1 wherein said sheet composite has an elongation of at least about 5 percent.

6. A release liner according to Claim 1 wherein said sheet composite has an elongation of at least about 10 percent.

7. A release liner according to Claim 1 wherein said sheet composite has a tensile force of at least about 7 pounds per inch-width at an elongation of about 20 percent.

8. A release liner according to Claim 1 wherein said substantially randomly orientated fibers are organic fibers.

9. A release liner according to Claim 1 wherein said substantially lineally aligned fibrous reinforced layer is comprised of organic fibers.

10. A release liner according to Claim 1 wherein said substantially lineally aligned fibrous reinforced layer is comprised of inorganic fibers.

11. A release liner according to Claim 1 wherein said sheet composite has a thickness between about 2 and about 15 mils.

12. A release liner according to Claim 1 wherein said composite sheet is substantially free of migratory plasticizers and silicones.

13. A release liner according to Claim 1 wherein said release layer is composed of butylene, isobutylene, polyethylene, ethylene vinyl acetate, ethylene acrylic acid, ethylene methyl methacrylate, ethylene butyl acrylate, polypropylene, and ethylene/propylene copolymers.

14. A release liner according to Claim 1 further comprising a friction-enhancing agent on the major surface of said sheet composite opposite the major surface on which said release layer is on.

15. The release liner of Claim 14 applied to a pressure-sensitive adhesive layer of an article.