WO2003044087A2

WO2003044087A2 - Pressure sensitive adhesive based on hydrogenated styrene block copolymer

Info

Publication number: WO2003044087A2
Application number: PCT/US2002/037006
Authority: WO
Inventors: Thomas Carrig
Original assignee: Adhesives Research, Inc.
Priority date: 2001-11-19
Filing date: 2002-11-19
Publication date: 2003-05-30
Also published as: WO2003044087A3; AU2002365973A1; AU2002365973A8

Abstract

An adhesive composition is provided comprising: (a) an A-B-A block copolymer with an A block that is non-elastomeric comprised of homopolymers and copolymers of vinyl monomers, and a B block that is elastomeric and is substantially hydrogenated, (b) a tackifying resin, and (c) optionally, a plasticizer in an amount of 20 % by weight or less, the A-B-A block copolymer being present in the composition in an amount ranging from 15-60 % by weight, and the tackifying resin being present in the composition in an amount ranging from 40-85 % by weight, each being based on the total weight of the composition, the block copolymer including a graft moiety in an amount within the range of from 0.5 to 5.0 % by weight, wherein the graft moiety is selected from the group consisting of ethylenically unsaturated carboxylic acids, ethylenically unsaturated carboxylic acid anhydrides, and derivatives thereof.

Description

"Pressure Sensitive Adhesive Based on Hydrogenated Styrene Block Copolymer"

Background of the Present Invention The present invention is directed to a novel adhesive composition which

exhibits highly desirable properties.

A number of adhesive compositions are known based on rubber polymer-

containing compositions, optionally together with one or more of a tackifier or

plasticizer. See, for example, U.S. Patent Nos. 5,093,422; 5,591,792; 5,703,162

5,719,226; 5,741,840; 5,912,295; 5,932,648; 5,939,483; 6,025,071; 6,103,814

6,162,868; 6,172,156; 6,232,391; 6,274,666; 6,277,488; 6,197,419; 4,136,699

5,459,193; 5,863,977; RE 36,757; 5,618,883; 4,286,077; and 5,656,687.

The disclosed compositions are primarily hot-melt type adhesive

compositions, which are formulated to enable the composition to be used as a hot-

melt. However, the formulations required to permit the satisfactory use of the

compositions as a hot-melt also serve to diminish the adhesive properties of the

compositions. For example, significant amounts of plasticizers are generally

present in hot-melt compositions in amounts (i.e., at least 10% by weight) which

serve to diminish the adhesive properties of the composition. As a result, the high

performance properties of the adhesive suffer.

It is thus desirable to provide an adhesive composition based on rubber

polymers which exhibits high performance properties including temperature

resistance as well as high shear and peel. It has now been found that rubber polymer-based adhesive compositions

can be provided which need not be used in the form of a hot-melt. In this case, hot

melt application is considered to be two independent steps of compounding the

adhesive in one step, followed by application of the compounded adhesive to

release liners or substrates in a second step. Each step utilizes different process

equipment. Typically, these two step operations impose limitations on adhesive

melt rheology to facilitate efficient flow in the application step. In the absence of

melt rheology limitations, formulation latitude is expanded which results in

enhanced physical properties being attained.

The benefits of the present invention are many. As opposed to typical "high

bond" adhesives, the present invention exhibits high peel adhesion values when

used on adherands with such varied surface energy as stainless steel, aluminum,

glass, PNC, high density polyethylene, polypropylene and wood. In connection

with higher surface energy substrates such as glass and stainless steel, the adhesion

exhibited is so great that the backing of the adhesive tape comprised of the

adhesive of the present invention will fail prior to the adhesive. Peel adhesion

values are measured in the range from 3 #/in up to in excess of 60 #/in, depending

upon ingredients. Peel adhesion values in excess of 15#/in are extremely unusual

in the art, even in cases where the adhesive exhibits poor cohesive strength as seen

through low holding power or shear resistance. In conjunction with the high peel

values of the present invention, the adhesive has also been shown to exhibit high

shear strength on the order of 10,000 minutes static shear with a ^XA x ^XA inch

sample under 500 gm and 1000 gm loads when bonded to stainless steel. This balance of properties makes this adhesive composition useful for some

applications that previously required a liquid "structural" adhesive.

Common to the prior art hot melt adhesive compositions based on block

copolymers with substantially hydrogenated midblock is a focus on maintaining

low melt viscosity for easy application. The benefits provided by these materials

include high cohesive strength imparted at low levels (<20% wt.) and stability

against degradation under melt processing relative to adhesive compositions based

on block copolymers with unsaturated midblocks (isoprene or butadiene).

The present invention is not driven by low melt viscosity and therefore

allows for wider formulation windows. In contrast to the teachings of the prior art,

the present invention provides extremely high peel adhesion in conjunction with

high cohesive strength using relative high levels of block copolymers of

substantially hydrogenated midblock.

Another advantage of the present invention is the ability to formulate a

thick adhesive composition that is substantially hydrogenated. This feature

provides a system that is resistant to degradation by thermal, oxidative or

ultraviolet radiation exposure. It is therefore of benefit for applications that must

survive such exposures. U.S. Patent No. 4,286,077 discloses weather resistant

adhesive compositions based on block copolymers with a substantially

hydrogenated midblock. Specific to that invention is such a block copolymer with

monoalkenyl arene end blocks at levels of 7-22% by weight of the multiblock

polymer. Further, the invention teaches that multiblock polymers with higher

monoalkenyl arene endblock content requires a level of plasticizer to impart good adhesive properties with the result that cohesive properties are lost. U.S. Patent

No. 6,197,419 discloses the weather resistant attributes of the block copolymers of

substantially hydrogenated midblock. The disclosed invention uses such polymers

in conjunction with block copolymers of unsaturated midblocks. The unsaturated

block copolymer is employed to impart good adhesive properties while the

substantially hydrogenated block copolymer is used to provide enhanced holding

power and weather resistance. By contrast, the present invention uses primarily or

exclusively substantially hydrogenated block copolymers and places no limitation

upon monoalkenyl arene content of such block copolymers.

It is well known to those skilled in the art that adhesive thickness (or

coating weight) plays a critical role in adhesion values obtained. As thickness

increases, the peel adhesion value also increases. In contrast, the holding power

will decrease as a function of increasing adhesive thickness. The effects of

increasing thickness upon peel adhesion typically plateau at a maximum peel

adhesion when thickness is in the range of 0.010"-0.015" thickness. The adhesive

of the present invention follows these same trends, and shows outstanding

adhesion values at thickness of less than .005". However the level of adhesion

obtained in combination with good holding power are novel to the art at a

thickness greater than 0.005".

Advantageously, while the adhesive of the present invention may be cured,

the adhesive functions effectively even in the absence of curing. Typically, prior

art adhesives require a curing or activation step to achieve high strength

"structural" adhesion. Such activation generally comprises thermal or radiation activation (UN or electron beam activation). This is generally found to be a

disadvantage as the backing material must be selected to be compatible with the

activating energy which limits the applicability of these products.

The adhesive of the present invention desirably finds application in the

areas of construction, automotive, marine and other areas where strong adhesive

bonds or gap filling features are desired.

Summary of the Present Invention

The present invention is directed to an adhesive composition comprising:

(a) an A-B-A block copolymer with an A block that is non-elastomeric

comprised of homopolymers and copolymers of vinyl monomers, and a B

block that is elastomeric and is substantially hydrogenated,

(b) a tackifying resin, and

(c) optionally, a plasticizer in an amount of 20 % by weight or less,

said A-B-A block copolymer being present in said composition in an amount

ranging from 15-60% by weight and preferably containing said A block in an

amount of at least 25 % by weight, and said tackifying resin being present in said

composition in an amount ranging from 40-85 % by weight, each being based on

the total weight of the composition, said block copolymer comprising a graft

moiety selected from the group consisting of ethylenically unsaturated carboxylic

acids, ethylenically unsaturated carboxylic acid anhydrides, and derivatives

thereof. In yet another embodiment of the present invention, the adhesive

composition is in the form of an extrudate which may be used to adhere two

surfaces together by placing the extrudate between and in contact with both

surfaces to be bonded together, optionally with application of elevated temperature

and/or pressure.

Detailed Description of the Present Invention

The block copolymer used in the adhesive of the present invention may be

selected from a variety of A-B-A block copolymers. In the block copolymer, the A

block is a non-elastomeric block comprised of homopolymers or copolymers of

vinyl monomers such as vinyl arenes, vinyl pyridines, vinyl halides and vinyl

carboxylates, as well as acrylic monomers such as acrylonitrile, methacrylonitrile,

esters of acrylic acids, etc. The A block may also comprise monovinyl aromatic

hydrocarbons including styrene, vinyl toluene, vinyl xylene, ethyl vinyl benzene as

well as dicyclic monovinyl compounds such as vinyl naphthalenes and the like.

Other non-elastomeric polymer A blocks may be derived from alpha olef ns,

alkylene oxides, acetals, urethanes, etc.

Polystyrene and its analogs and homologs are preferred as the A block of

the block copolymer. Exemplary analogs and homologs include alpha-methyl

styrene, t-butyl styrene, 3-methyl styrene, 4-n-propylstyrene, 4-p-propylstyrene, 1-

vinylnaphthalene, 2-vinylnaphthalene and mixtures thereof.

The B block is an elastomeric block component which is preferably at least

partially and most preferably at least substantially hydrogenated. Exemplary B blocks include but are not limited to polybutadiene, poly(ethylene-butylene),

polyisoprene, poly(ethylene/propylene), etc.

The preferred block copolymer for use in the present invention is an

styrene-ethylene/butylene-styrene (SEBS) block copolymer.

The content of the A block in the block copolymer generally ranges from

about 10 to 45% by weight based on the total weight of the block copolymer, and

preferably at least 25 % by weight, while the content of the B block in the block

copolymer generally ranges from about 55 to 90% by weight.

The block copolymer includes a graft moiety selected from the group

consisting of ethylenically unsaturated carboxylic acids, ethylenically unsaturated

carboxylic acid anhydrides, and derivatives thereof. Exemplary unsaturated

carboxylic acid and anhydrides thereof include but are not limited to mono-, di- or

polycarboxylic acids such as (meth)acrylic acid, maleic acid, fumaric acid, itaconic

acid, crotonic acid, itaconic anhydride, maleic anhydride and substituted maleic

anhydride, such as dimethyl maleic anhydride or citrontonic anhydride, nadic

anhydride, nadic methyl anhydride, tetrahydrophthalic anhydride, etc. Maleic

anhydride is particularly preferred as the graft moiety. Exemplary derivatives of

the above include but are not limited to salts, imides, amides, and esters of the

unsaturated carboxylic acids. Examples of such derivatives include mono- or

disodium maleate, acrylamide, maleimide, glycidyl methacrylate and dimethyl

fumarate.

Further exemplary derivatives of maleic anhydride include but are not

limited to mono-esters of maleic anhydride or maleic acid with alcohols (i.e., monomaleates), corresponding diesters (dimaleates), amides obtained by

amidation of maleic anhydride or maleic acid with ammonia or an amine

(maleamides) and the corresponding imides (maleimides). The preferred graft

moiety is maleic anhydride.

The amount of graft moiety which may be present on the block copolymer

is not critical. It is believed that the presence of the graft moiety in an amount

ranging from about 0.5 to 5.0 wt. % based on the weight of the block copolymer is

satisfactory. However, it may be advisable to employ higher amounts of the graft

moiety if deemed desirable.

Maleic anhydride grafted styrene-ethylene-butylene-styrene triblock

polymers are disclosed in U.S. Patent No. 5,656,687 and 6,093,768, herein

incorporated by reference. Such graft block copolymers are also commercially

available under the trademark KRATON from KRATON Polymers LLC as

KRATON FG1901X and KRATON FG1924X. Grafted polyisoprene polymers

are disclosed in U.S. Patent No. 4,204,046. Grafted polyolefin polymers are

disclosed in U.S. Patent No. 6,228,948. U.S. Patent No. 5,618,883 discloses

maleated ethyl ene-propylene diene polymers.

The block copolymer is generally present in the adhesive composition of

the present invention in an amount of about 15 to 60 wt. %, based on the total

weight of the composition. A combination of block copolymers may be employed

to tailor the adhesive composition properties for specific attributes, the total

amount of which is also about 15 to 60% wt. %. Preferably, the block copolymer is present in an amount of greater than 20% by wt., and more preferably from 25-

60 % by wt.

A variety of tackifiers may be employed, with the tackifier being chosen for

suitability depending upon whether it is deemed desirable for the tackifier to be

compatible with the end blocks of the block copolymer or the midblocks, or

whether a balance of compatibility properties is desired. Also, it may be useful for

the tackifier to be hydrogenated in the event that the block copolymer is

substantially hydrogenated in order to enhance the compatibility of the tackifier

with the block copolymer. That is, it is preferred for at least 50% , and most

preferably at least 80% of the unsaturated groups in the tackifier to be

hydrogenated.

More specifically, exemplary tackifiers include but are not limited to natural

and modified rosins (such as gum rosin, wood rosin, tall oil rosin, distilled rosin,

hydrogenated rosin, dimerized rosin and polymerized rosin), glycerol and

pentaerythritol esters of natural and modified rosins (such as glycerol ester of

wood rosin, glycerol ester of hydrogenated rosin, glycerol ester of polymerized

rosin, pentaerythritol ester of hydrogenated rosin, and phenolic modified

pentaerythritol ester of rosin), hydrocarbon tackifier resins, aromatic hydrocarbon

resins, aliphatic hydrocarbon resins (such as polymerization product of monomers

comprised mainly of olefins and diolefins and hydrogenated aliphatic petroleum

hydrocarbon resins), polyterpene resins (based on alpha pinene, beta pinene or d-

limonene), modified terpenes (such as styrene/terpene, alpha methyl

styrene/terpene, bicyclic monoteφene, hydrogenated polyteφenes, product of bicyclic teφene and phenol), alicyclic hydrocarbon resins, coumarone-indene

resins, etc.

Desirably, the tackifier which is employed exhibits a softening point within

the range of from about 60 to 150 °C. as determined by ASTM method E28-58 T.

The tackifier is generally present in the adhesive composition in an amount

ranging from about 40 to 85 wt. % based on the weight of the adhesive

composition. Of course, the tackifier is ultimately present in an amount effective

to enable the composition to exhibit the desired pressure sensitive adhesive

properties. The use of a tackifier which is substantially saturated will reduce the

possibility that the combination of the tackifier with the block copolymer will be

detrimental to the melt viscosity of the composition. Mixtures of the above

tackifiers may also be employed as found desirable or advantageous. In particular,

it is found that the use of at least two tackifier resins, the first with softening point

below about 85°C and the second with softening point of greater than about 85°C,

is of benefit. The two different tackifiers may be of the same or different

chemistry, provided that they are compatible.

The adhesive composition may contain additional components including but

not limited to plasticizers, fillers, antioxidants, crosslinkers, wood or cellulose

fibers, thermoplastic polymers (such as hydroxypropyl cellulose, polyamides, etc.),

fillers (such as thermal or electrical conductive fillers, clays, talc, solid spheres,

silica, carbon, synthetic or natural fibers, dyes, pigments, etc.), stabilizers (thermal,

oxidative, UN, hydrolytic, etc.), etc. Exemplary stabilizers or antioxidants include those known to one of

ordinary skill in the art such as hindered phenols either alone or in combination

with a secondary antioxidant such as phosphite antioxidants.

Exemplary crosslinking agents include those known to one of ordinary skill

in the art including but not limited to metallic, amine-type, epoxy-type, glycol-

type, silane-type and isocyanate-type crosslinking agents. For example, in a paper

titled "Crosslinking of Acid-Funtional Styrenic Block Polymers with Aluminum

Acetylacetonate" by St. Clair of Kraton Polymers (TAPPI Hot melt Conference,

Hilton head, SC; June 2001) the author demonstrates the relative efficacy of

various metal chelates in crosslinking the base polymers of the present invention.

In terms of processing and performance, the aluminum acetylacetonate was found

to be the most useful. Relative to the present invention, it is noted that the

maximum peel adhesion cited in this paper (including uncrosslinked adhesives) is

about 5.3 #/in, and static shear values of less than 60 minutes (25mm x 25 mm; 1

Kg). However the same crosslinking approach, in which SAFT increased 20-30°C

as a result of crosslinking, can be employed to the present invention.

As an alternative to crosslinking as a means to increase the heat resistance

of the present invention, one can also use additives that chemically associate with

the styrenic end blocks of the base polymer. Examples of such additives are

tackifiers based on styrene monomer (Endex 150 sold by Hercules, Inc.), styrene

modified teφenes (Sylvares TP-2040 sold by Arizona Chemical or SP-553 sold by

Schenectady International), and polyphenylene ethers (SA-120 sold by General

Electric Plastics). These end block associating resins are known in the art as means to increase heat resistance (see US Patent No. 6,277,488), but they are also

known to have a detrimental effect on peel adhesion and tack of a pressure

sensitive adhesive. The adhesive composition of the present invention

demonstrates the same effect. However, the peel adhesion of the composition

prior to adding the end block reinforcing resin is so high that any decrease of peel

adhesion is compensated for and a high performance product is still obtained.

Plasticizers which may be employed are those which are conventionally

employed in conjunction with polymeric compositions. Such plasticizers are

typically fluid so as to provide additional fluidity to the adhesive composition as

well as to enhance the adhesive tack of the adhesive composition. Exemplary

plasticizers include but are not limited to oil and liquid elastomers which flow at

ambient temperature and are compatible with the block copolymer, such as mineral

and petroleum based hydrocarbon oils, polybutene, liquid elastomers,

functionalized oils such as glyceryl trihydroxyoleate or other fatty oils. The

contemplated plasticizers are desirably low in aromatic content and are paraffinic

or napthenic in character. Compatible tackifier chemistries that are liquid at room

temperature also are considered useful plasticizers. Examples include but are not

limited to C₅ petroleum hydrocarbons, methyl ester of rosin, hydrogenated

hydrocarbons and polyteφenes.

The plasticizer, if present, will generally be present in an amount of up to

about 20 % by weight, based on the total weight of the adhesive composition, more

preferably less than 10 % by weight, such that a balance of properties of the

invention is maintained. The adhesive composition of the present invention may also include

blowing agents or hollow expandable or non-expandable microspheres to decrease

the density of the extruded adhesive composition either by action of the blowing

agents or by the presence of the hollow microspheres.

The block copolymer described above may also be combined with one or

more compatible homo-, co- or block polymers compatible with the block

copolymer. For example, it may be an advantage to incoφorate a polystyrene

block copolymer (grafted or non-grafted) which block copolymer does not have an

elastomeric midblock. The presence of elastomeric A-B diblocks is also

appropriate, with such diblocks being present in an amount of up to 30% by wt.

Such diblocks enhance adhesion while inhibiting shear strength. The presence of

increased amounts of styrene in the adhesive composition will increase shear

strength while inhibiting adhesion. Preferably, the block copolymer having the

elastomeric midblock portion will comprise from about 25 to 100% by weight of

the total block copolymers present in the composition. However, the ratio of such

block copolymers is not critical, and may be modified in a manner sufficient to

attain the desired balance of, for example, shear and adhesion.

The respective components can be combined by any conventional means.

Provided that all components of a particular formulation are soluble in the same

solvent or solvent blend, the adhesive composition can be prepared as a solution,

and then coated and dried by means known to those skilled in the art. A practical

limitation of this method is the ability to attain a dried adhesive deposition of

0.005" or more due to solvent evaporation at the surface of the coating prior to bulk evaporation. This method typically will yield a coating with high residual

solvent content as well as entrapped solvent bubbles.

The preferred method of preparation is melt processing as 100% solids. For

example, the components can be combined by continuous blending of the

components in the melt at a suitable temperature in a twin screw extruder whereby

a homogeneous blend is obtained. Alternatively, batch mixing of the components

as a melt in a heated vessel such as a sigma blade mixer is also appropriate. Once

the components are melt mixed to a uniform adhesive composition, the discharged

mix can be immediately applied to a substrate (including release liners) to the

desired shape and thickness. Coating techniques are known to those skilled in the

art such as a heat die, heated rolls, etc., which apply the adhesive composition to a

release liner or backing substrate, typically in the form of roll. Melt processing is

preferred as it is shown that relatively thick coatings (greater than 0.005" and

preferably from 0.005-0.080" thickness) of the adhesive composition can be

prepared without the need for evaporating solvents and thereby providing a coating

free of defects.

The adhesive composition provides novel utility as a strong adhesive that

can fill gaps, dampen vibration, act as a barrier, etc., in applications that

traditionally apply a cure-in-place sealant or caulk. As stated previously, the

adhesive of the present invention requires no cure time. Therefore assemblies

bonded with the adhesive composition of the present invention can be handled and

further processed within minutes of forming the bond. It is well known that caulks

and sealants require a much longer time to cure from a liquid or semi-solid before the assembled part can be handled. Such prior art cure times are typically

recommended as hours, or even days.

The present invention will be further described in conjunction with the

following Examples.

Examples

The following examples demonstrate the high performance features of the

present invention. Examples 1-9 and 12-15 illustrate the effect of the presence of

styrene, maleic anhydride graft and diblock content on the various properties of the

adhesive composition. Examples 10-12 additionally demonstrate the benefit of

utilizing the high styrene content containing hydrogenated block copolymer.

Three block copolymers are employed at various ratios in these examples as shown

in Table 1. KRATON FG1924X (KRATON Polymers, LLC) is a maleic

anhydride SEBS copolymer having about 13 wt. % of styrene, about 30 wt. %

styrene-ethylene/butylene diblock, and about 1 wt. % maleic anhydride graft.

KRATON FG1901X is also a maleic anhydride grafted SEBS block copolymer

with about 30% wt. styrene, no diblock content, and about 2% wt. maleic

anhydride. KRATON G1652 is a SEBS block copolymer with no maleic

anhydride graft, 30% styrene content and no diblock.

The tackifiers represent a variety of chemistry. Resin H (Resinas

Sinteticas) is a hydrogenated rosin with a softening point of about 70 °C and a

minimum acid number of 158. Foral 105 (Hercules, Inc.) is a pentaerithrytol ester

of hydrogenated rosin with a softening point of about 105°C and an acid number in

the range of 6-10. Sylvares TR-1085 (Arizona Chemical) is a polyteφene resin based on β-pinene with a softening point of about 85°C and an acid number of less

than 1. Sylavrez TR-1100 (Arizona Chemical) is a polyteφene resin based on β-

pinene with a softening point of about 100°C and an acid number of less than 1.

Escorez 5380 (Exxon Mobil) is a hydrogenated hydrocarbon resin with a softening

point of about 80°C and an acid number of less than 1. Wingtack 10 (Goodyear

Tire & Rubber) is an aliphatic C₅ petroleum hydrocarbon that is liquid at room

temperature. Indopol H-1900 is a polybutene (BP Amoco). Hercolyn D (Pinova

division of Hercules, Inc.) is a methyl ester of rosin, also a liquid at room

temperature. Cellolyn 21 (Pinova division of Hercules, Inc.) is a phthalate ester of

technical hydroabletyl alcohol with a softening point of 60-70 °C and an acid

number of at least 10. Escorez 1580 (ExxonMobil Chemical) is an aliphatic

hydrocarbon resin with a softening point of about 80 °C.

Table 1

The adhesive compositions of Examples 1-15 were processed with a 19 mm

diameter co-rotating, intermeshing twin screw extruder (B&P Process Equipment

MP19-TC) without the use of a slot die, with the extruded mixture coated between

two release liners on a simple two roll coater gapped to provide a coating thickness

of 0.040". The respective components were fed by gravimetric or volumetric

feeders into various sequential feed ports of the extruder. The length/diameter

ratio in each instance was 40: 1. The polymers with the highest melt viscosity were

fed into the extruder first, with the additives being fed downstream after

mastication of the base polymer. In some cases, it was advisable to feed a portion

of the tackifier with the base polymer to assist in mastication. The temperature

within various zones of the respective extruders ranged from 60 to 240 °C,

depending upon the function of the respective zone and the barrel diameter of the

extruder. Upon discharge from the barrel of the extruder, the resulting

homogeneous mixture was coated onto a desired substrate or backing material.

The preferred substrate is a release material in roll form. The Examples 1-15 were

tested for properties as shown in Table 2.

Table 2

Note. All peel adhesions are 180° peels based on PSTC-1. The backing substrate for all examples was 0 005" aluminum as plastic films typically failed during the pee testing pnor to adhesive failure. Vaπous substrate peel panels were used as indicated, with dwell time of the adhesive on the panels also noted

Static shear test was on V." x V." adhesive overlap to stainless steel with vaπous weights, as noted, suspended from the free end of the tape sample. Failure tune i minutes was recorded

Shear Adhesion Failure Temperature (SAFT) was obtained by bonding a l"xl" adhesive overlap to stainless steel panel and allowing the bond to dwell for 24 hours The panel was placed in apparatus similar to that for static testing that is in oven after programmed temperature control. A 500 gram weight was suspended from the sample an the oven was set for 40 °C After 10 minutes, the temperature was mcreased at a rate of 5°C/mιn to 45°C, 10 minute dwell The 5°C increment with 10 minute dwell every 5°C i continued until the adhesive fails The temperature at failure is recorded

Peel adhesions m #/ιn, Shears in minutes

• * denotes backing substrate failure before adhesive failure

• ** Shear failure for Example 13 was not cohesive failure, but rather a slow creep failure. Shear failure for Examples 5-9 were adhesive failure

Claims

WHAT IS CLAIMED IS:

1. An adhesive composition comprising:

(a) an A-B-A block copolymer with an A block that is non-elastomeric

comprised of homopolymers and copolymers of vinyl monomers, and a

B block that is elastomeric and is substantially hydrogenated,

(b) a tackifying resin, and

(c) optionally, a plasticizer in an amount of 20 % by weight or less,

said A-B-A block copolymer being present in said composition in an

amount ranging from 15-60 % by weight, and said tackifying resin being present in

said composition in an amount ranging from 40-85 % by weight, each being based

on the total weight of the composition,

said block copolymer including a graft moiety in an amount within the

range of from 0.5 to 5.0 % by weight, wherein said graft moiety is selected from

the group consisting of ethylenically unsaturated carboxylic acids, ethylenically

unsaturated carboxylic acid anhydrides, and derivatives thereof.

2. The composition of claim 1, wherein said A-B-A block copolymer is present

in an amount greater than 20 % by weight, based on the total weight of the

composition.

3. The composition of claim 1, wherein said A-B-A block copolymer is present in

an amount of from 25-60% by weight, based on the total weight of the

composition.

4. The composition of claim 1, wherein said A-B-A block copolymer is a styrene-

ethylene/butylene-styrene block polymer.

5. The composition of claim 1 , wherein the A-B-A block copolymer is a styrene-

ethylene/propylene- styrene block polymer.

6. The composition of claim 1, wherein said tackifying resin is a hydrogenated

rosin ester.

7. The composition of claim 1, wherein said tackifying resin is a polyteφene

derived from α-pinene, β-pinene or d-limonene.

8. The composition of claim 1, where the tackifying resin is a hydrogenated

hydrocarbon.

9. The composition of claim 1, further containing a polyphenylene ether resin in

an amount ranging from 1-8% by weight, based on the total weight of the

composition.

10. The composition of claim 1, further containing a plasticizer in an amount of up

to 20% by weight.

11. The composition of claim 1 , further containing an inert material selected from

the group consisting of pigments, fibers, solid and hollow spheres, clays, silica,

and talc.

12. The composition of claim 6, further containing a crosslinking agent capable of

reacting with the grafted functional groups on the block copolymer.

13. The composition of claim 1, comprising multiple tackifier resins, one of said

tackifier resins having a softening point of less than 85°C while another of said

tackifier resins having a softening point of greater than 85°C.

14. The composition of claim 1, comprising at least two block copolymers, with

one of said block copolymer containing less than or equal to 25% by weight

monoalkenyl arene, with said second block copolymer containing greater than

25% by weight monoalkenyl arene.

15. The composition of claim 1, further comprising a compatible thermoplastic

polymer in an amount of up to 25% by weight.

16. The composition of claim 1, further comprising an incompatible thermoplastic

polymer in an amount of up to 25% by weight.

17. The composition of claim 1, wherein said A block is present in said

composition in an amount of at least 25 % by weight, based on the total weight

of the composition.

18. An adhesive extrudate comprised of the composition of claim 1.