(12) United States Patent
`Gehlsen et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 6,864,322 B2
`Mar. 8, 2005
`
`USOO6864322B2
`
`(54)
`
`(75)
`
`(73)
`
`(21)
`(22)
`(65)
`
`(51)
`(52)
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`(58)
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`(56)
`
`LINERLESS DOUBLE-SIDED PRESSURE
`SENSITIVE ADHESIVE TAPE
`
`Inventors: Mark D. Gehlsen, Eagan, MN (US);
`Peter A. Stark, Cottage Grove, MN
`(US); Bradley S. Momchilovich, New
`Richmond, WI (US)
`Assignee: 3M Innovative Properties Company,
`St. Paul, MN (US)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 33 days.
`
`Notice:
`
`Appl. No.: 10/600,983
`Filed:
`Jun. 20, 2003
`Prior Publication Data
`
`US 2004/026.0024A1 Dec. 23, 2004
`Int. Cl................................................. C08L 33/08
`U.S. Cl. ............... 525/227; 428/41.4; 428/355 AC;
`428/355 CN; 428/343
`Field of Search .......................... 525/227; 428/343,
`428/355 CN, 355 AC, 41.5
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`2.884,126 A 4/1959 Ulrich
`
`3,008,850 A 11/1961. Ulrich
`4,181,752 A 1/1980 Martens et al.
`5,753,768 A
`5/1998 Ellis
`5,840,783 A * 11/1998 Momchilovich et al. ... 522/112
`6,294.249 B1
`9/2001 Hamer et al.
`2002/0004130 A1
`1/2002 Lhila
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`WO
`WO
`WO
`
`O121430
`WO 97/23577
`WO 99/42536
`WO 03/011588
`
`10/1984
`7/1997
`8/1999
`2/2003
`
`* cited by examiner
`
`Primary Examiner William K. Cheung
`(74) Attorney, Agent, or Firm-Sean Edman
`(57)
`ABSTRACT
`The present invention relates to a double-sided preSSure
`Sensitive adhesive foam tape. In certain embodiments the
`foam tape does not require the use of a release liner.
`Elimination of the release liner reduces the cost of the tape
`and also avoids problems associated with damage to the
`liner during traditional tape manufacturing from exposure to
`e-beam radiation.
`
`28 Claims, 1 Drawing Sheet
`
`
`
`1 5 O
`
`1 OO
`
`5 O
`
`O
`
`800
`
`200
`
`6OO
`4OO
`ELONGATION (%)
`-A-6% PC
`-o- O% PC
`-- MICROFOAMTM
`-- 2%. PC
`-0- 4% PC
`
`1OOO
`
`EX. 1032
`APPLE INC. / Page 1 of 10
`
`

`

`U.S. Patent
`
`Mar. 8, 2005
`
`US 6,864,322 B2
`
`
`
`1 5 O
`
`100
`
`5 O
`
`O
`O
`
`1 OOO
`
`8OO
`
`200
`
`6OO
`400
`ELONGATION (%)
`-o- 0% PC -A- 6% PC
`-H 2% PC -- MICROFOAMTM
`-- 4% PC
`Fig. 1
`
`EX. 1032
`APPLE INC. / Page 2 of 10
`
`

`

`1
`LINERLESS DOUBLE-SIDED PRESSURE
`SENSITIVE ADHESIVE TAPE
`
`US 6,864,322 B2
`
`2
`preSSure Sensitive adhesives do not Substantially adhere to
`one another, i.e. when the two pressure Sensitive adhesives
`are brought into contact with each other they can be sepa
`rated without causing cohesive failure of the foam or
`delamination of either the first or Second pressure Sensitive
`adhesive from the foam.
`The acidic monomer of the ICPN can be, for example, an
`ethylenically unsaturated carboxylic acid, an ethylenically
`unsaturated Sulfonic acid, an ethylenically unsaturated phos
`phonic acid, and mixtures thereof. In Some implementations
`the basic monomer is Selected from the group consisting of
`N,N-dimethylaminopropyl methacrylamide (DMAPMAm),
`N,N-diethylaminopropyl methacrylamide (DEAPMAm),
`N,N-dimethylaminoethyl acrylate (DMAA), N,N-
`diethylamino ethyl acrylate (DEAEA), N,N-
`dimethylaminopropyl acrylate (DMAPA), N,N-
`diethylaminopropyl acrylate (DEAPA), N,N-
`dimethylaminoethyl methacrylate (DMAEMA), N,N-
`diethylaminoethyl methacrylate (DEAEMA), N,N-
`dimethylaminoethyl acrylamide (DMAEAm), N,N-
`dimethylaminoethyl methacrylamide (DMAEMAm), N,N-
`diethylaminoethyl acrylamide (DEAEAm), N,N-
`diethylaminoethyl methacrylamide (DEAEMAm), 4-(N.N-
`dimethylamino)-styrene (DMAS), 4-(N,N-diethylamino)-
`styrene (DEAS), N,N-dimethylaminoethyl vinyl ether
`(DMAEVE), N,N-diethylaminoethyl vinyl ether
`(DEAEVE), vinylpyridine, vinylimidazole, and mixtures
`thereof.
`Various pressure Sensitive adhesives can be used with the
`invention. In Some implementations the first preSSure Sen
`Sitive adhesive comprises acrylic acid, and the Second pres
`Sure Sensitive adhesive comprises acrylic acid and acryloni
`trile. These two preSSure Sensitive adhesives can be Selected
`Such that they do not adhere to one another; yet readily
`adhere to the ICPN-containing foam core.
`The invention is also directed to a double-sided foam tape
`comprising a foam core having first and Second opposed
`Surfaces in which a first preSSure Sensitive adhesive is
`applied to the first Surface of the foam core, the first pressure
`Sensitive adhesive comprising acrylic acid; and a Second
`preSSure Sensitive adhesive applied to the Second Surface of
`the foam core, the Second pressure Sensitive adhesive com
`prising acrylic acid and acrylonitrile. The first and Second
`preSSure Sensitive adhesives do not Substantially adhere to
`one another; and the foam core is configured to bond to the
`first pressure Sensitive adhesive and to the Second preSSure
`Sensitive adhesive.
`Yet another aspect of the invention is directed to a
`double-sided foam tape, the foam tape comprising a foam
`core having first and Second opposed Surfaces, the foam core
`comprising an acidic copolymer derived from a first group
`of monomers comprising at least one acidic monomer, and
`a basic copolymer derived from a Second group of mono
`mers comprising at least one basic monomer. A first preSSure
`Sensitive adhesive is applied to the first Surface of the foam
`core, the first pressure Sensitive adhesive comprising acrylic
`acid; and a Second pressure Sensitive adhesive is applied to
`the Second Surface of the foam core, the Second preSSure
`Sensitive adhesive comprising acrylic acid and acrylonitrile.
`Again, the first and Second pressure Sensitive adhesives do
`not Substantially adhere to one another.
`Other features and advantages of the invention will be
`apparent from the following detailed description of the
`invention and the claims. The above Summary of principles
`of the disclosure is not intended to describe each illustrated
`embodiment or every implementation of the present disclo
`SUC.
`
`FIELD OF THE INVENTION
`The present invention relates to adhesive tapes, more
`Specifically to pressure Sensitive adhesive tapes. In
`particular, the invention relates to double-sided pressure
`Sensitive adhesive tapes.
`
`BACKGROUND
`Pressure sensitive adhesive (PSA) compositions are used
`in a wide variety of applications. Numerous applications
`require pressure Sensitive adhesives to Support a load at
`elevated temperatures, typically in the range of greater than
`70° C., for which high cohesive strength PSAS are required.
`A Standard method of increasing cohesive Strength at
`elevated temperatures is to chemically crosslink the PSA
`using irradiation processes, Such as thermal radiation, ultra
`violet (UV) radiation, gamma radiation, and electron beam
`(EB) radiation, etc. Although these processes improve cohe
`Sive Strength, they often negatively impact other properties,
`including peel strength of the PSA.
`PSA compositions have been used as tapes, in particular
`as double-sided tapes used to adhere two articles together.
`Such double-sided PSA tapes are useful, for example, in
`automotive manufacturing, numerous consumer products,
`construction, and for maintenance and repair of many items.
`Most conventional double-sided PSA tapes typically require
`that at least one side of the tape be covered with a release
`liner to prevent the two sides from Sticking together.
`Although Such release liners are functional, they have the
`disadvantage of being time consuming to use, as well as
`adding expense to the PSA tape and waste to its application.
`For Some applications, PSAS formed into foams are
`desirable because tapes made of foam can conform better to
`certain Substrates, thereby giving better adhesion and greater
`holding power. Foamed PSA tapes are particularly desirable
`on irregular shaped Surfaces that would not otherwise pro
`vide an adequate surface with which to contact the PSA.
`Therefore, a need exists for an improved PSA tape that
`does not require irradiation, and which advantageously can
`be produced without the use of a release liner on one or both
`major Surfaces, and which includes a foam to improve
`adhesion to irregular Surfaces.
`SUMMARY OF THE INVENTION
`The present invention relates to a double-sided pressure
`Sensitive adhesive foam tape. In certain embodiments the
`foam tape does not require the use of a release liner.
`Elimination of the release liner reduces the cost of the tape
`and also avoids problems associated with damage to the
`liner during traditional tape manufacturing from exposure to
`e-beam radiation. The double-sided pressure Sensitive adhe
`Sive foam tape is produced, in Specific implementations,
`without e-beaming to cure the adhesives, although the tape
`can be e-beamed in alternate implementations.
`In a first aspect of the invention the foam tape comprises
`a foam core comprising an acidic polymer derived from at
`least one acidic monomer and a basic polymer derived from
`at least one basic monomer to form an ionically crosslinked
`polymeric network (ICPN). A first pressure sensitive adhe
`Sive is applied to one Surface of the foam core; and a Second
`preSSure Sensitive adhesive applied to a Second Surface of
`the foam core. In one embodiment, the first and Second
`
`15
`
`25
`
`35
`
`40
`
`45
`
`50
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`55
`
`60
`
`65
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`EX. 1032
`APPLE INC. / Page 3 of 10
`
`

`

`US 6,864,322 B2
`
`3
`BRIEF DESCRIPTION OF THE FIGURES
`Other aspects and advantages of the invention will
`become apparent upon reading the following detailed
`description and upon reference to the drawing in which:
`FIG. 1, is a graph showing the tensile and elongation
`properties of various double-sided preSSure Sensitive tapes.
`In particular, FIG. 1 shows the tensile and elongation
`properties of ICPN foam samples containing 0% (C2), 2%
`(Example 1), 4% (Example 2), and 6% (Example 3) of an
`amine-containing polymer (referred to herein as “PIC"). In
`addition, a sample of 3M Microfoam TM tape is shown as a
`comparison. This plot demonstrates that by controlling the
`level of PIC (i.e., the ratio of the polymers of the ICPN) in
`the foam the properties of the foam can be modified to meet
`the performance requirements of the product.
`While the invention is susceptible to various modifica
`tions and alternative forms, specifics thereof have been
`shown by way of example in the figure and will be described
`in detail. It should be understood, however, that the intention
`is not to limit the invention to the particular embodiments
`described. On the contrary, the intention is to cover all
`modifications, equivalents, and alternatives falling within
`the Spirit and Scope of the invention as defined by the
`appended claims.
`DETAILED DESCRIPTION
`The present invention is directed to a double-sided pres
`Sure Sensitive adhesive foam tape. In certain embodiments
`the foam tape does not require the use of a release liner,
`although a liner may be used if desired. Elimination of the
`liner reduces the cost of the tape, and also avoids problems
`asSociated with e-beaming damage to the liner during tra
`ditional tape manufacturing. The double-sided pressure Sen
`Sitive adhesive foam tape is produced, in Specific
`implementations, without e-beaming to cure the adhesives,
`although the tape can be e-beamed in alternate implemen
`tations.
`Specific components of the double-sided pressure Sensi
`tive adhesive tape will now be described in greater detail,
`including a discussion of the foam core and the adhesives
`used to form the adhesive tape, plus examples of adhesive
`tapes produced in accordance with the invention.
`I. Foam Core
`The foam core of double-sided tapes made in accordance
`with the present invention typically comprises a blend of at
`least one acidic polymer and at least one basic polymer to
`form an ionically crosslinked polymeric network. Thermally
`reversible chemical crosslinks form as part of a network of
`polymeric ionic crosslinks between the acidic polymer and
`the basic polymer, allowing the composition forming the
`foam core to be easily hot-melt processed, but provide
`improved cohesive Strength to foams containing the
`crosslinker after its application and cooling.
`The acidic polymer is generally derived from at least one
`55
`acidic monomer. In Some implementations the acidic mono
`mer is Selected from ethylenically unsaturated carboxylic
`acids, ethylenically unsaturated Sulfonic acids, ethylenically
`unsaturated phosphonic acids, and mixtures thereof. Suit
`able acidic monomers include, for example, ethylenically
`unsaturated carboxylic acids. When even Stronger acids are
`desired, particularly preferred acidic monomers include the
`ethylenically unsaturated Sulfonic acids and ethylenically
`unsaturated phosphonic acids.
`In Some implementations the acidic polymer is an acidic
`(meth)acrylate copolymer in which the acidic (meth)acrylate
`copolymer is derived from at least one acidic monomer and
`
`4
`at least one (meth)acrylate monomer Selected from the group
`consisting of monofunctional unsaturated (meth)acrylate
`esters of non-tertiary alkyl alcohols, and mixtures thereof,
`the alkyl groups of which comprise from about 1 to about 20
`carbon atoms, preferably about 1 to about 18 carbon atoms,
`such as those of Formula (I):
`
`R1 O
`
`Formula (I)
`
`wherein R is H or CH, the latter corresponding to where
`the (meth)acrylate monomer is a methacrylate monomer,
`and R is a linear, branched, aromatic, or cyclic hydrocarbon
`grOup.
`The basic polymer is generally derived from at least one
`basic monomer. Suitable basic monomers include, for
`example non-nucleophilic amine-functional monomers,
`such as those of Formula (II):
`
`Formula (II)
`
`CH=C-C 3. X-Y-Am
`
`wherein
`a is 0 or 1;
`R is selected from H- and CH-,
`X is selected from -O- and -NH-,
`Y is a divalent linking group, preferably comprising
`about 1 to about 5 carbon atoms for ease of avail
`ability; and
`Am is a tertiary amine fragment, Such as the group:
`
`--R R2
`wherein R' and R are selected from alkyl, aryl, cycloalkyl,
`and arenyl groups. R' and R in the above group may also
`form a heterocycle. Alternatively, Am can be pyridinyl or
`imidazolyl, Substituted or unsubstituted. In all embodiments,
`Y, R', and R may also comprise heteroatoms, such as O, S,
`N, etc.
`Exemplary basic monomers include, but are not limited
`to, N,N-dimethylamino propyl methacrylamide
`(DMAPMAm); N,N-diethylaminopropyl methacrylamide
`(DEAPMAm); N,N-dimethylaminoethyl acrylate
`(DMAEA); N,N-diethylaminoethyl acrylate (DEAEA);
`N,N-dimethylaminopropyl acrylate (DMAPA); N,N-
`diethylaminopropyl acrylate (DEAPA); N,N-
`dimethylaminoethyl methacrylate (DMAEMA); N,N-
`diethylaminoethyl methacrylate (DEAEMA); N,N-
`dimethylaminoethyl acrylamide (DMAEAm); N,N-
`dimethylaminoethyl methacrylamide (DMAEMAm); N,N-
`diethylaminoethyl acrylamide (DEAEAm); N,N-
`diethylaminoethyl methacrylamide (DEAEMAm); N.N-
`dimethylaminoethyl vinyl ether (DMAEVE); N,N-
`diethylaminoethyl vinyl ether (DEAEVE); and mixtures
`thereof. Other useful basic monomers include vinylpyridine,
`vinylimidazole, tertiary amino-functionalized styrene (e.g.,
`4-(N,N-dimethylamino)-styrene (DMAS), 4-(N,N-
`diethylamino)-styrene (DEAS)), and mixtures thereof.
`In Some implementations the basic polymer is a copoly
`mer derived from at least one basic monomer and at least
`one non-basic copolymerizable monomer. Other monomers
`
`15
`
`25
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`35
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`40
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`45
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`50
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`60
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`EX. 1032
`APPLE INC. / Page 4 of 10
`
`

`

`US 6,864,322 B2
`
`15
`
`40
`
`45
`
`S
`can be copolymerized with the basic monomers (e.g., acidic
`monomers, vinyl monomers, and (meth) acrylate
`monomers), as long as the basic copolymer retains its
`basicity (i.e., it can still be titrated with an acid). Typically,
`the copolymerizable monomers are essentially free of acidic
`monomers (i.e., the copolymerizable monomers include
`about 5 wt. 76 or less of acidic monomers, but most
`preferably, the copolymerizable monomers are free of acidic
`monomers).
`The basic copolymer can be, for example, a basic (meth)
`acrylate copolymer. In this embodiment, the basic (meth)
`acrylate copolymer is derived from at least one monomer of
`Formula 1. In one embodiment, the foam composition
`comprises a blend of an acidic copolymer derived from a
`first group of monomers comprising at least one acidic
`monomer; and a basic copolymer derived from a Second
`group of monomers comprising at least one basic monomer,
`Such as those described in Formula (II), wherein at least one
`of the first and Second group of monomers comprises greater
`than about 15% by weight of acidic or basic monomers,
`respectively. That is, the acidic copolymer is derived from at
`least 15% by weight of acidic monomers and/or the basic
`copolymer is derived from at least 15% by weight of basic
`monomers, based on total weight of the respective mono
`mers. In certain embodiments at least one of the first and
`25
`Second group of monomers comprises at least about 25% by
`weight, more preferably at least about 35% by weight, even
`more preferably at least about 50% by weight, and most
`preferably at least about 60% by weight of the respective
`acidic or basic monomers. Advantageously each of the
`acidic copolymer and the basic copolymer are derived from
`monomers comprising at least one (meth)acrylate monomer,
`Such as an alkyl (meth)acrylate monomer. Although more
`may be used, in certain embodiments, one of the acidic
`copolymer and the basic copolymer advantageously need
`only comprise up to about 5% by weight of the blend,
`typically about 0.5% to about 5% by weight of the blend.
`In another embodiment, the foam composition comprises
`a blend of an acidic homopolymer and a basic copolymer
`derived from a group of monomers comprising at least one
`basic monomer. In certain variations of this embodiment, the
`group of monomers comprises at least about 15% by weight
`of basic monomers, although lower amounts may also be
`used. Advantageously, although more may be used, the
`acidic homopolymer need only comprise as little as up to
`about 5% by weight of the blend, most typically about 0.5%
`by weight to about 5% by weight of the blend, in order to
`achieve foam cores having cohesive Strengths Suitable for
`intended applications.
`In yet another embodiment, the foam composition com
`50
`prises a blend of an acidic copolymer derived from mono
`mers comprising at least one monomer Selected from the
`group consisting of an ethylenically unsaturated Sulfonic
`acid, an ethylenically unsaturated phosphonic acid, and
`mixtures thereof and at least one non-acidic copolymeriZ
`able monomer, and a basic homopolymer.
`One suitable polymer for the ICPN composition includes
`the copolymer of 40/60 2-ethylhexylacrylate/
`dimethylaminoethylmethacrylate (2EHA/DMAEMA).
`Other suitable ratios include, for example, 30/70 and 20/80
`ratios of 2-ethylhexylacrylate to dimethylaminoethyl
`methacrylate. Other suitable polymers are described in WO
`99/42536, which is herein incorporated by reference.
`The foam core can include a plurality of expanded poly
`meric microSpheres to form the foam. The foam may also
`include one or more non-expandable microSpheres, which
`may be polymeric or non-polymeric microSpheres (e.g.,
`
`35
`
`55
`
`60
`
`65
`
`6
`glass microspheres). The expandable microspheres typically
`feature a flexible, thermoplastic, polymeric shell and a core
`that includes a liquid and/or gas that expands upon heating.
`The core material is generally an organic Substance that has
`a lower boiling point than the Softening temperature of the
`polymeric Shell. Examples of Suitable core materials
`include, but are not limited to, propane, butane, pentane,
`isobutane, neopentane, and combinations thereof. Preferred
`core materials are materials other than air that expand upon
`heating. Microspheres suitable for use with the invention
`usually have an activation temperature below the tempera
`ture needed to melt mix the copolymer and the polyarylene
`oxide polymer. Thus, the activation temperature is generally
`less than 200 C., more typically less than 170° C.
`The choice of thermoplastic resin for the polymeric shell
`of the microSpheres influences the mechanical properties of
`the foam. Accordingly, the properties of the foam may be
`adjusted through appropriate choice of microSpheres, or by
`using mixtures of different types of microSpheres. For
`example, acrylonitrile-containing resins are useful where
`high tensile and cohesive Strength are desired, particularly
`where the acrylonitrile content is at least 50% by weight of
`the resin, more preferably at least 60% by weight, and even
`more preferably at least 70% by weight. In general, both
`tensile and cohesive Strength increase with increasing acry
`lonitrile content. In Some cases, it is possible to prepare
`foams having higher tensile and cohesive Strength than the
`polymer matrix alone, even though the foam has a lower
`density than the matrix. This provides the capability of
`preparing high Strength, low density articles.
`The amount of expandable microSpheres can be Selected
`based upon the desired properties of the foam tape. Higher
`microSphere concentrations generally cause lower density of
`the foam. The amount of microSpheres generally ranges
`from about 0.1 parts by weight to about 50 parts by weight
`(based upon 100 parts of polymer mixture), more typically
`from about 0.5 parts by weight to about 20 parts by weight.
`Alternatively, or in conjunction with expandable
`microSpheres, the pressure Sensitive adhesive tapes of the
`invention may be formed into a foam by use of blowing
`agents, including chemical blowing agents and physical
`blowing agents. Use of blowing agents instead of expand
`able microSpheres to form a foam tends to make the resulting
`foam more Susceptible to irreversible collapse under pres
`Sure. This feature may be desirable in Some applications
`where conformity to irregular Surfaces is desired.
`Physical blowing agents useful in the present invention
`include various naturally occurring atmospheric materials
`that are a vapor at the temperature and pressure at which the
`foam exits the die. The physical blowing agent may be
`introduced into the polymeric material as a gas or liquid,
`preferably as a liquid, and may be introduced in a Super
`critical State. Suitable physical blowing agents include, for
`example, carbon dioxide, nitrogen, SF, nitrous oxide, per
`fluorinated fluids, Such as CF, argon, helium, noble gases,
`Such as xenon, air (nitrogen and oxygen blend), and blends
`of these materials.
`Chemical blowing agents may also be added to the melt
`mixture. Suitable chemical blowing agents include, for
`example, a blend of Sodium bicarbonate and citric acid,
`dinitrosopentamethylene tetramine, p-toluene Sulfonyl
`hydrazide, 4-4'-oxybis(benzenesulfonyl hydrazide, azodi
`carbonamide (1,1'-azobisformamide), p-toluenesulfonyl
`Semicarbazide, 5-phenyltetrazole, 5-phenyltetrazole
`analogues, diisopropylhydraZodicarboxylate, 5-phenyl-3,6-
`dihydro-1,3,4-oxadiazin-2-one, and Sodium borohydride.
`II. Pressure Sensitive Adhesives
`
`EX. 1032
`APPLE INC. / Page 5 of 10
`
`

`

`7
`The double-sided pressure Sensitive tape typically con
`tains a different pressure Sensitive adhesive on each side of
`the tape. The pressure-Sensitive adhesive compositions
`(referred to herein as the first PSA (PSA-1) and second PSA
`(PSA-2)) useful in this invention can be in the form of
`Solutions, emulsions, or dispersions, or as SolventleSS adhe
`Sive compositions. A first PSA includes acrylate and meth
`acrylate polymers or copolymers that do not contain acry
`lonitrile or methacrylonitrile. Such polymers can be formed
`by polymerizing 50 to 100 parts by weight of one or more
`monomeric acrylic or methacrylic esters of non-tertiary
`alkyl alcohols, with the alkyl groups having from 1 to 20
`carbon atoms (e.g. from 3 to 18 carbon atoms). Suitable
`acrylate monomers include, for example, methyl acrylate,
`ethyl acrylate, n-butyl acrylate, lauryl acrylate, 2-ethylhexyl
`acrylate, cyclohexyl acrylate, iso-octyl acrylate, octadecyl
`acrylate, nonyl acrylate, decyl acrylate, isobornyl acrylate,
`and dodecyl acrylate. Also useful are aromatic acrylates,
`e.g., benzyl acrylate and cyclobenzyl acrylate. Optionally,
`one or more monoethylenically unsaturated co-monomers
`may be polymerized with the acrylate or methacrylate
`monomers; the particular amount of co-monomer is Selected
`based upon the desired properties of the polymer. One group
`of useful co-monomers includes those having a homopoly
`mer glass transition temperature greater than the glass
`transition temperature of the acrylate homopolymer.
`Examples of Suitable co-monomerS falling within this group
`include, but are not limited to, acrylic acid, acrylamide,
`methacrylamide, Substituted acrylamides Such as N,N-
`dimethyl acrylamide, itaconic acid, methacrylic acid, Vinyl
`acetate, N-Vinyl pyrrollidone, isobornyl acrylate, cyano ethyl
`acrylate, N-vinylcaprolactam, maleic anhydride,
`hydroxyalkylacrylates, N,N-dimethyl aminoethyl (meth)
`acrylate, N,N-diethylacrylamide, beta-carboxyethyl
`acrylate, Vinyl esters of neodecanoic, neononanoic,
`neopentanoic, 2-ethylhexanoic, or propionic acids (e.g.,
`available from Union Carbide Corp. of Danbury, Conn.
`under the designation “Vynates', vinylidene chloride,
`Styrene, Vinyl toluene, and alkyl vinyl ethers.
`A Second group of monoethylenically unsaturated
`co-monomers which may be polymerized with the acrylate
`or methacrylate monomers includes those having a
`homopolymer glass transition temperature less than the glass
`transition temperature of the acrylate homopolymer.
`Examples of Suitable co-monomerS falling within this class
`include ethyloxyethoxy ethyl acrylate (Tg=-71 C.) and a
`methoxypolyethylene glycol 400 acrylate (Tg=-65 C.;
`available from Shin Nakamura Chemical Co., Ltd. under the
`designation “NK Ester AM-90G”). See, e.g., Ulrich, U.S.
`Pat. No. 2,884,126; Martens U.S. Pat. No. 4,181,752; Hamer
`U.S. Pat. No. 6,294.249; and Ellis U.S. Pat. No. 5,753,768).
`The second PSA can include acrylate and methacrylate
`copolymers that contain acrylonitrile or methacrylonitrile.
`Such polymers can be formed by polymerizing 50 to 100
`parts by weight of one or more monomeric acrylic or
`methacrylic esters of non-tertiary alkyl alcohols, with the
`alkyl groups having from 1 to 20 carbon atoms (e.g. from 3
`to 18 carbon atoms). Suitable acrylate monomers include,
`for example, methyl acrylate, ethyl acrylate, n-butyl
`acrylate, lauryl acrylate, 2-ethylhexyl acrylate, cyclohexyl
`acrylate, iso-octyl acrylate, octadecyl acrylate, nonyl
`acrylate, decyl acrylate, isobornyl acrylate, and dodecyl
`acrylate. Also useful are aromatic acrylates, e.g., benzyl
`acrylate and cyclobenzyl acrylate. Optionally, one or more
`monoethylenically unsaturated comonomers may be poly
`merized with the acrylate or methacrylate monomers, the
`particular amount of co-monomer is Selected based upon the
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`desired properties of the polymer. One group of useful
`co-monomers includes those having a homopolymer glass
`transition temperature greater than the glass transition tem
`perature of the acrylate homopolymer. Examples of Suitable
`co-monomerS falling within this group include, but are not
`limited to, acrylic acid, acrylamide, methacrylamide, Sub
`Stituted acrylamides Such as N,N-dimethyl acrylamide, ita
`conic acid, methacrylic acid, acrylonitrile, methacrylonitrile,
`Vinyl acetate, N-Vinyl pyrrollidone, isobornyl acrylate, cyano
`ethyl acrylate, N-Vinylcaprolactam, maleic anhydride,
`hydroxyalkylacrylates, N,N-dimethyl aminoethyl (meth)
`acrylate, N,N-diethylacrylamide, beta-carboxyethyl
`acrylate, Vinyl esters of neodecanoic, neononanoic,
`neopentanoic, 2-ethylhexanoic, or propionic acids (e.g.,
`available from Union Carbide Corp. of Danbury, Conn.
`under the designation “Vynates', vinylidene chloride,
`Styrene, Vinyl toluene, and alkyl vinyl ethers.
`A Second group of monoethylenically unsaturated
`co-monomers which may be polymerized with the acrylate
`or methacrylate monomers includes those having a
`homopolymer glass transition temperature less than the glass
`transition temperature of the acrylate homopolymer.
`Examples of Suitable co-monomerS falling within this class
`include ethyloxyethoxy ethyl acrylate (Tg=-71 C.) and a
`methoxypolyethylene glycol 400 acrylate (Tg=-65 C.;
`available from Shin Nakamura Chemical Co., Ltd. under the
`designation “NK Ester AM-90G"). See e.g., Ulrich, U.S.
`Pat. No. 3,008,850; Martens U.S. Pat. No. 4,181,752; Hamer
`U.S. Pat. No. 6,294.249; and Ellis U.S. Pat. No. 5,753,768).
`III. Other Additional Ingredients
`Additional ingredients may be added to augment proper
`ties of the pressure-sensitive adhesive foam. These include,
`for example, a relatively high modulus polymer that can
`Stiffen the foam. Suitable polymers include, e.g., Semi
`crystalline polymerS Such as polyamides and polyesters, and
`relatively low modulus polymer compositions that can
`increase the flexibility of the article, e.g., plasticized poly
`vinyl chloride. Relatively immiscible polymer compositions
`can act to form fibrous networks to further reinforce the
`cohesive Strength of the article when the immiscible phases
`are elongated under Stretching forces. Examples of Such
`Structures containing fiber-like reinforcing networks are
`disclosed in WO 97/23577 “Blended Pressure-Sensitive
`Adhesives', which is incorporated herein by reference.
`The foamed pressure Sensitive adhesive may contain
`agents in addition to microSpheres, the choice of which is
`dictated by the properties appropriate for the intended appli
`cation of the article. Examples of Suitable additives include,
`but are not limited to, tackifiers (e.g., rosin esters, terpenes,
`phenols, and aliphatic, aromatic, or mixtures of aliphatic and
`aromatic Synthetic hydrocarbon resins), plasticizers, oils,
`pigments, dyes, non-expandable polymeric or glass
`microSpheres, reinforcing agents, hydrophobic or hydro
`philic Silica, calcium carbonate, toughening agents, fire
`retardants, antioxidants, finely ground polymeric particles
`Such as polyester, nylon, or polypropylene, Stabilizers, and
`combinations thereof. These additives are included in
`amounts Sufficient to obtain the desired end properties.
`The invention will now be more particularly illustrated by
`the following examples, which are not intended to be
`limiting in any way.
`IV. EXAMPLES
`
`A. Test Methods
`Density
`The densities of the foams of the invention were measured
`using the following procedure. Samples of the foam were cut
`into 13 mmx25 mm pieces, weighed on a Mettler high
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`precision balance and then placed underwater. The mass of
`the displaced water was measured. The water temperature
`was approximately 25 C. Using the density of the water as
`1 g/cm, the mass of the displaced water divided by the
`density of the water gives the volume of the sample. The
`mass of the sample is then divided by the volume of the
`Sample to generate the density of the Sample. Two replicates
`were measured and averaged together.
`Static Shear
`The bond strengths (in shear mode) of the tapes of the
`invention to a Standard aluminum panel were measured
`using the following procedure. A 1.3 cm (0.5 in) wide piece
`of tape with a release liner on one Side and exposed adhesive
`on the other Side was adhered to a 1.6 cm wide Strip of a
`0.127 mm thick aluminum foil. The release liner was then
`removed from the non-adhered side and the tape was then
`adhered to a clean rigid anodized aluminum panel using four
`passes of a 2 kg (4.5 lb) hard rubber roller such that a 1.3 cm
`by 2.5 cm portion of the tape was in firm contact with the
`panel. A non-adhered end portion of the tape extended
`beyond the panel. The panel was then hung in a constant
`temperature and humidity chamber (22 C.; 50% relative
`humidity). The panel was positioned 2 degrees from the
`Vertical to prevent a peel mode failure. A 1000 gram weight
`was then hung from the non-adhered end of the tape Sample
`and the time required for the weight to fall off was recorded
`in minutes. If no failure occurred within 10,000 minutes, the
`test was discontinued and results were recorded as 10,000+
`minutes. If the tape fell off in fewer than 10,000 minutes, the
`time was recorded and the mode of failure noted as either
`cohesive failure within the adhesive, or an adhesive failure
`when the adhesive pulled cleanly from the panel. All
`examples exhibited adhesive failure. Three replicates were
`measured and averaged together.
`Adhesive Anchorage
`The bond strength of the pressure s