AU2008203362A1 - Radiation curable adhesive - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION Standard Patent Applicant: NATIONAL STARCH AND CHEMICAL INVESTMENT HOLDING CORPORATION Invention Title: RADIATION CURABLE ADHESIVE The following statement is a full description of this invention, including the best method for performing it known to us: P48097 AU. POLSOLFilng Appicaton 20087-728 do (M) 00 0 ~N RADIATION CURABLE ADHESIVE 00 I FIELD OF THE INVENTION INO The invention relates to the field of adhesives. More specifically, the invention relates to radiation curable adhesives based on epoxy-functional block copolymers.

00 SBACKGROUND OF THE INVENTION Radiation curable adhesives which cure by free radical mechanisms have gained wide acceptance in a number of product assembly applications. Cationic curing systems enjoy several advantages over free radical systems. First, cure is not instantaneous and thus the possibility exists to irradiate the sample and then make the bond. This feature obviates the need ior one substrate being radiation transparent, which many are not. Secondly, since there is no termination mechanism other than neutralization of the active acid catalyst by impurities, the cure proceeds into the "dark" non-irradiated) regions of the sample. Thus, if impuritios are minimized the entire adhesive sample will eventually cure as long as one part of it is irradiated.

Most cationic systems use cycloaliphatic epoxide monomers or vinyl ethers. Kraton Polymers irecently developed a system based on epoxidized block copolymers, with the epoxy groups residing almost exclusively In the polyisoprene blocks. These systems enabled highly flexible arid even pressure sensitive radiation cured adhesives based on cationic cure chemistry. However, the systems have been hindered by high costs, primarily because of the use ol expensive mono-ol liquids that have been used in place of mineral oils to maximize pressure :3ensitive adhesive properties, and also by the tendency for preferred photoinitiators (which aro present as finely dispersed particles) to settle over time in the liquid or "warm melt" adhesives;.

la- 00 O A need remains for radiation curable adhesives that may be formulated at a lower cost and that avoid certain problems previously encountered in the art. The current invention Saddresses this need.

00 SUMMARY OF THE INVENTION \It has now been discovered that an Improved balance of properties can be obtained Cn by combining epoxidized block copolymers with other saturated block copolymers containing N a hard block and/or by adding lower levels of rosin derived alcohols. Hot melt adhesives with 00 O superior pressure sensitive adhesive properties have been obtained by this method. In these solid adhesives settling of the dispersed photoinitiator particles is effectively eliminated, thus ensuring a long shelf life.

Tho invention provides adhesive formulations based on epoxidized block copolymers and contain a rosin-derived alcohol or a saturated block copolymer which are particularly advantageous for use as a labeling adhesive, for applying a label to a container such as, for example, a bottle, and for use in the manufacture of industrial tapes.

On, aspect of the invention Is directed to a radiation curable adhesive comprising an epoxidized block copolymer, a saturated block copolymer and/or a rosin derived alcohol, and a photoinitintor. Preferred saturated block copolymers are styrenic block copolymers. The adhesives of the invention may optionally comprise a hydrocarbon resin, a rosin and/or rosin ester, and En oil.

Preferred adhesives will typically comprise from about 10 to about 60% by weight of at least one epoxidized block copolymer, from about 3% to about 30% by weight of at least one saturated block copolymer and/or from about 3% to about 20% of a rosin derived monool, from about 20% to about 70% of at least one hydrocarbon resin, up to about 25% of a rosin and/or rosin ester, up to about 0 to about 30% of a mineral oil, and an effective amount of a photoinitiator.

Another aspect of the invention Is directed to an article of manufacture comprising the adhesive of the invention. In one embodiment the article is a labeled container. In another embodiment the article is an adhesive tape.

00 DETAILED DESCRIPTION OF THE INVENTION The disclosures of all references cited herein are incorporated in their entireties by Sreference.

00 NC< The invention is directed to adhesives based on epoxidized block copolymers and containing a rosin-derived alcohol or a saturated block copolymer. In the adhesives of the Invention, settling of the dispersed photoinitiator is surprisingly minimized. The adhesives of m the invention are generally less expensive than prior art formulas, due In part to the raw 00 materials, and exhibit improved properties in terms of tack, peel and shear.

The curable adhesives are radiation curable adhesives. The adhesives may, desirably, be formulated as a "hot melt," a "warm melt" or a liquid adhesive, and formulated to be pressure sensitive or not. "Hot melt" adhesives are defined here as those applied at temperatures from 250PF to 4009F, whereas "warm melt" adhesives are applied at temperature above ambient but below 2509F. "Liquid" adhesive require no heat for their application; they are applied at ambient conditions.

As ised herein, the term "pressure-sensitive adhesive" refers to a viscoelastic material which adheres instantaneously to most substrates with the application of slight pressure ar.d remains permanently tacky. Pressure sensitive adhesives are bondable at ambient conditions indefinitely. Non-pressure sensitive adhesives are used to form bonds while in the molten state, i.e. they are applied hot to the substrate and bonded to the second substrate prior to setting. Once set they have little if any tack or bondability. One cannot coat these types of adhesives onto one substrate and create a bond with them to a second substrate a a later date at ambient conditions as can be done with a true pressure sensitive.

The term "curable" is used herein in its conventional sense as meaning capable of forming covalent cross-links.

Tho term "radiation-curable adhesive" as used herein means an adhesive composition that is curable upon exposure to actinic and/or ionizing radiation. The term "radiation" is used herein to include actinic radiation such as ultraviolet radiation and ionizing radiation created by the emission of electrons or highly accelerated nuclear particles such as neutrons, alpha-particles etc.

00 Prferred radiation curable adhesives comprise, as the base polymer, at least one epoxidized block copolymer capable of UV cationic curing. Epoxidized block copolymers which may be used in the practice of the Invention include those described in U.S. Patent 00 rC Nos. 5,22S,,464, 5,491,193, 5,516,824, 5,686,535, 5,776,998, and 5,837,749, and are commerciELIly available from Kraton Polymers. Both radial and linear epoxidized block NO copolymers may be used in the practice of the invention for use. A preferred epoxidized M block copolymer which may be used in the practice of the Invention Is EKP 207 (Kraton

N

0 Polymers), a diblock copolymer prepared by the sequential polymerization of isoprene and

O

butadiene, followed by hydrogenation and epoxidation. EKP 207 contains about 11 epoxide groups per molecule.

The adhesive of the invention will typically comprise about 10% to about 60% of the epoxidized block copolymer.

Saturated block copolymers consist of materials of the structure or or or wherein X is a multlvalent coupling agent with functionality m n of two or more, and polymer blocks A are non-elastomeric polymer blocks and polymer blocks B are saturated elastomeric blocks, and polymer blocks C are either saturated or unsaturated, preferably :nsaturated elastomeric blocks. Saturated blocks are substantially hydrogenated such that the majority of olefinic groups have been eliminated. Copolymers useful in the present invention may be linear or radial; with radial copolymers the functionality of X is three or more. Some levels of diblock copolymer, A-B, may be present by design or due to Incomplete coupling of the A-B arms to X. Diblock Is beneficial for Increasing tack, peel and open time, but reduces cohesive strength and resistance to cold flow prior to cure.

Examples of multifunctional coupling agents, include dibromoethane with functionality of 2; trisnonylphenyl phosphite and trichloromethyl silane, both with functionality of 3; and tetra chlorosilane with functionality of 4.

The non-elastomeric blocks A may comprise homopolymers or copolymers of vinyl monomers such as vinyl arenes, vinyl halides, and vinyl carboxylates, as well as acrylic monomers such as acrylonitrile, methacrylonitrile, esters of acrylic acids, etc. Monovinyl aromatic h'ydrocarbons include styrene, vinyl toluene, vinyl xylene, ethyl vinyl benzene as well as dicyclic monovinyl compounds such as vinyl naphthalene and the like. Other non- 00 elastomeric: polymer bolcks may be derived from alpha olefins such as vinyl cyclohexane, or Sother rigid olefins such as norbornene, pinene, and the like. Styrene is preferred, In an amount comprising less than 45% by weight of the total copolymer composition, more 00 Spreferably 15 to 25%, however it is most preferred that the least amount of styrene possible is used in order to maximize the softness and flexibility of the final cured adhesive, while still forming hard styrene domains upon cooling to produce a solid adhesive. The elastomeric Sblocks B ar d C are derived from a diene or dlenes (preferably isoprene and/or butadlene).

00The B blocks are substantially hydrogenated (saturated) by means well known in the art. It is preferred that the C blocks, if present, are not hydrogenated, and most preferably are isoprene. Suitable saturated block copolymers Include SEBS (polystryene end blocks with a hydrogenat3d butadiene midblock) and SEPS (polystyrene end blocks with a hydrogenated isoprene midblock). Polymers high in diblock (SEB or SEP) are preferred. High levels are those abov 10%, with levels above 25% preferred, and levels of above 40% most preferred.

Block copolymer molecules with more than one hard (high Tg) A block provide the adhesive with strength and resistance to cold-flow (the resistance to slumping in the unsupported state at ambient conditions) prior to cure. Diblock copolymer molecules improve the pressure sensitivity of the final cured adhesive. Even more preferred are radial block copolymers in which both 'unctions strength and pressure sensitivity are derived from one molecule.

These radial materials contain hard A blocks at the ends of at least two of the arms and one or more amis consisting of C blocks. The latter arms are termed free arms or pendant arms since they are not linked into the hard domains when the adhesive cools (no A block). These pendant amis are derived form diene monomers and may be saturated (via subsequent hydrogenation) or unsaturated. Preferably these pendant arms are derived from isoprene.

An example of such a material is GRP 6919, also referred to as "Tacky a (SEB) 2 2 radial block copolymer available from Kraton Polymers.

Adt-esives of the invention will typically comprise about 3% to about 30%, more preferably from about 5% to about 15%, of the styrenic block copolymer.

Sullable rosin derived alcohols include hydrogenated rosin, available from Hercules under the tradename Abitol E, and chemical derivatives of rosin available from Arakawa Chemical under the tradename Pinecrystal.

00

O

Adhesives of the invention will typically comprise about 3% to about 20%, more preferably up to about 15%, of the rosin derived alcohol. The level will depend on the level of pressure sensitivity needed in the final adhesive and the amount and type of epoxidized block 00 Cl copolymer used. The alcohol acts as a chain transfer agent during cationic polymerization of the epoxy groups. Diols can act as crosslinkers whereas mono-ols will act to reduce the IO crosslink density and improve the adhesion of the crosslinked polymer through pendant rosin M substituents. Diols used in excess (over the amount of epoxy) can also Improve tack and 0 reduce overall crosslink density. Mono-ols are most preferred. It has been discovered that use of a ro.in alcohol produces a cured adhesive with more extensibility as measured by free swell in cyclohexane, which dissolves the saturated polymer and everything else that is not crosslinked. Peel and tack are also improved.

The adhesive compositions of this invention also may include an aliphatic or cycloaliphalic hydrocarbon resin with or without aromatic modification (preferably without), such as those derived from terpene monomers or from petroleum-derived monomers, as tackifier. Preferred are hydrogenated petroleum-derived hydrocarbon resins. Non-limiting examples include aliphatic olefin derived resins such as those available from Goodyear under the Wingtack® tradename and the Escorez 1300 series from ExxonMobil. A common tackifying resin in this class is a diene-olefin copolymer of piperylene and 2-methyl-2-butene having a softening point of about 950C. This resin Is available commercially under the tradename 'Ningtack 95 and is prepared by the cationic polymerization of a mixture containing approximately 60% plperylene, 10% Isoprene, 5% cyclo-pentadlene, 15% 2-methyl-2-butene and about 10% dimer, as taught in U.S. Patent No. 3,577,398. The resins normally have ring and ball softening points as determined by ASTM method E28 between about 200C and 150°C. Also useful are Cs/Cg aromatic/aliphatic olefin-derived resins available from ExxonMobil in the Escorez 2000 series. Hydrogenated hydrocarbon resins are especially useful wher the long term resistance to oxidation and ultraviolet light exposure is required.

These hydrogenated resins include such resins as the Escorez 5000 series of hydrogenated cycloaliphatic resins from ExxonMobil, hydrogenated C, and/or Cs resins such as Arkon® P115, P125 supplied by Arakawa Chemical, hydrogenated aromatic hydrocarbon resins such as Regalrez 1018, 1085 and the Regalite® R series of resins from Hercules Specialty -6- 00 O Chemicals. Other useful resins include hydrogenated polyterpenes such as Clearon® P-105, _P-115 and P-125 from the Yasuhara Yushi Kogyo Company of Japan. Preferred for use are Shydrogenated, cyclic or Cs resins, such as Escorez 5400 (ExxonMobil), a hydrogenated 00 Cl DCPD (dicylopentadiene) tackifer. Mixtures of two or more of the above described resins may be preferred for some formulations.

sO Achesives of the invention will typically contain from about 20% to about 70 of the 0 hydrogenated resin, more preferably from about 30% to about c l The adhesives of the invention may optionally contain a rosin and/or rosin ester.

00 These tacH:ifiers are added to improve the adhesion to various surfaces, especially polar surfaces such as glass, metal, or corona-treated plastics. Representative examples are natural and modified rosins including gum rosin, wood rosin, tall oil rosin, distilled rosin, hydrogenated rosin, dimorized rosin, and polymerized rosin; glycerol and pentaerythritol esters of natural and modified rosins, including the glycerol ester of pale, wood rosin, the glycerol ester of hydrogenated rosin, the glycerol ester of polymerized rosin, the pentaerythritol ester of hydrogenated rosin, and the phenolic-modified pentaerythritol ester of rosin.

The rosin and/or rosin ester will typically be used in amounts of up to about Rosin is preferred over rosin ester for maximum adhesion to polar substrates.

The adhesives of the invention may also comprise up to about 30% by weight of an oil diluent. Suitable oils include olefin oligomers and low molecular weight polymers as well as vegetable and animal oil and their derivatives. The petroleum derived oils which may be employed are relatively high boiling materials containing only a minor proportion of aromatic hydrocarbons (preferably less than 30% and, more particularly, less than 15% by weight of the oil). Alternatively, the oil may be totally non-aromatic. Suitable oligomers include polypropylenes, polybutenes, hydrogenated polylsoprene, hydrogenated polybutadiene, or the like having average molecular weights between about 350 and about 10,000. Preferred are petroloum derived white oils such as Britol 35T, a paraffinic white oil and KAYDOL OIL a napthenic white oil, both of which are available from Witco Corporation.

The cationic photolnitiators are typically employed in concentrations ranging from about by weight to about 10% by weight, preferably in amounts ranging from about 0.05% by weight to about 1% by weight, more preferably from about 0.1% by weight to about 00 by weight. Combinations of two or more photoinitiators may also be used. A preferred photoinitiator, is Sarcat CD1010 (available from Sartomer), a triaryl sulfonium Shexafluoro;antimonate salt also available from Union Carbide under the tradename Cyracure 00 CKl UVI 6974. For liquid adhesives, the less thermally stable iodonlum salt, Sarcat CD1012, is suitable.

NO Photosensitizers may be added to extend the spectral response to higher M wavelengths and thus speed cure and Improve depth of cure. For example phenothlazlne, C perylene, and anthracene are effective sensitizers for both sulfonium and iodonium salts.

00 Combinations of photoinitiators may be used to achieve the best possible cure of adhesive compositions. Photolnltlators are preferably used in the least amount necessary to get initiation of cure at the line speed of the process. Catlonic cure is inhibited by basic species suh as amines or even water, and these must therefore be avoided or adequate photoinitiator added to overcome them.

Antioxidants are typically added to the commercially available compounds in order to protect the ingredients against degradation during preparation and use of the adhesive compositions. Combinations of antioxidants are often more effective due to the different mechanisms of degradation to which various polymers are subject. Certain hindered phenols, organo-metallic compounds, aromatic amines, aromatic phosphites, and sulphur compounds are useful 1or this purpose. Examples of effective types of these materials include phenolic antioxidants, thio compounds, and tris-(nonylated phenyl) phosphites.

Examples of commercially available antioxidants include IRGANOX 1010 (pentaetythrityl-tetrakis[3-(3,5-dl-tert- -butyl-4-hydroxyphenyl)propionate); IONOL (2,6-ditertiary-butyl-4-methyl phenol); IONOX 330 (3,4,6-tris 1,3,5-trimethylbenzene); and POLYGARD HR (tris-(2,4-dl-tertiary-butyl-phenyl) phosphite).

The antioxidant chosen must not interfere with the radiation cure of the final composition.

Irganox 1010 has been found to be suitable in combination with the photoinitiator UVI 6974.

To ensure long-term thermal stability, in general from about 0.1% to about 3% by weight of cne or more antioxidants is included in the adhesive compositions, preferably from about 0.4% by weight to about 1.5% by weight.

00 Acditional materials may be added optionally to the adhesive composition at up to about 15% by weight, preferably from about 5% by weight to about 10% by weight, dependent on the intended end-use of the adhesive. Such additional materials include, without limitation, 00 CK1 unsaturated block copolymers of monovinyl aromatic hydrocarbons and conjugated dienes such as pclystyrene-polybutadiene-polystyrene, polystyrene-polyisoprene-polystyrene, \O poly(alpha.methyl-styrene)-polybutadiene-poly(alpha-methyl-styrne), poly(alpha-methyl- M styrene)-polyisoprene-poly(alpha-methyl-styrene). Other polymers that can be added to 00 modify adhesive properties include hydrogenated radial polyisoprene (for example Kraton 0 G1750 sold by Kraton Polymers). Polylsobutylene, butyl rubber, polyisoprene, polybutadiene, and ethylene propylene random copolymers, and styrene butadiene random copolymers.

In addition to the above-described additional materials, the various compositions of the present invention may include other additives known to those skilled In the art. These additives may include, but are not limited to, pigments, fillers, waxes, fluorescent additives, flow and leveling additives, wetting agents, surfactants, antifoaming agents, rheology modifiers, and stabilizers. Preferred additives are those which do not have appreciable absorption in the wavelengths of Interest and are not basic.

E>amples of waxes include petroleum-derived such as paraffin wax, or synthetic waxes such as those produced by Fischer-Tropsch chemistry. Naturally derived waxes including rion-reactive waxes and reactive waxes such as castor wax (which can react through its hydroxyl groups during cure).

Examples of pigments and filler materials include, but are not limited to, titanium dioxide, hydrophobic amorphous fumed silica, amorphous precipitated silica, carbon black, and polymer powders. Examples of flow and leveling additives, wetting agents, and antifoaming agents Include sillcones, hydrocarbons, fluorine-containing compounds, and nonsilicone polymers and copolymers such as copolyacrylates.

Other materials which may be added optionally to the adhesive composition include endblock resins which are substantially aromatic. Examples of such endblock resins can be prepared from any substantially aromatic monomers having a polymerizable unsaturated group. Typical examples of such aromatic monomers include the styrenic monomers, styrene, alpha-methyl styrene, vinyl toluene, methoxy styrene, tertiary butyl styrene, chloro 00 0 styrene, indene monomers including indene, and methyl indene. The aromatic endblock resin is preferably present In amounts of 5 to 20 weight percent. Preferred is HERCOLITE S240 or KRISTALEX 5140, both of which are alpha methyl styrene resins available from 00 SHercules, Inc.

One embodiment of the invention is directed to an adhesive comprising an epoxidized block copolymer, a saturated block copolymer, and a photoinltlator. The adhesives of the Cinvention may optionally further comprise a hydrocarbon resin, a rosin derived alcohol, a CKl rosin, rosin ester and/or an oil.

00 SAnother embodiment of the Invention is directed to an adhesive comprising an epoxidized block copolymer, a rosin derived alcohol, and a photoinitiator. The adhesives of the invention may optionally further comprise a hydrocarbon resin, a saturated block copolymer, a rosin, rosin ester and/or an oil.

In a preferred embodiment of the present invention the adhesive composition comprises rom about 15% to about 35% by weight of at least one epoxidized block copolymer, from about 5% to about 15% by weight of at least one saturated block copolymer, from about 30% to about 60% by weight of at least one hydrocarbon resin, from about 3 to about 15% of a rosin derived mono-ol, from about 0.02 to about 2.0% of a cationic photoinitlator, from about 0 to about 25% of a rosin and/or.rosin ester, from about 0 to about of a mineral oil, and from about 0 to about 2% of an antioxidant.

The adhesive compositions of the invention are prepared by conventional methods.

As an example, the epoxidized block copolymer and saturated block copolymer or tackifying resin and other desired components may be blended at an elevated temperature, (e.g.

temperature of about 300 0 F) using an extruder, a Z-blade mixer or other conventional mixing device.

The adhesives of the invention find particular use in the tape and label industry.

The adhesives of the present invention may be used to bond labels to plastic, glass or plastic-coated glass, wood, metal, etc. articles, such as containers and bottles soft drink, salad dressing, sauce and condiment bottles, cans, buckets and beakers). Plastic as used herein refers to the material used to make food and other storage containers such as polyethylene, polypropylene, polystyrene, polycarbonate, polyvinylchloride, and polyethylene 00 terephthalate (PET). The labels may be made of paper, coated paper, embossed paper, Smetallized paper, foil laminated paper, or various plastic films (eg. polyvinyl chloride, c- polystyrene, polyethylene terephthlate, polypropylene, polyethylene), and may be opaque or 00 C- transparent. To attach the labels to the article, the adhesive is applied to the surface of the article or to the label. The adhesive may be applied by a variety of methods including coating or spraying in an amount sufficient to cause the substrates to be bonded together to adhere.

M The adhesive coated substrate label or article) may be irradiated before or after bonding. .Since cure begins immediately upon Irradiation, but may not be completed for 00 several da'ys, there is time immediately after Irradiation, but before gelation for bonding to take place. Ideally, the bond is made before irradiation for optimum wet out and adhesion.

For labels iroduced off line from the bottle labeling process, and for tapes, the adhesive is applied to the release paper or the backing, then irradiated and bond to the other surface (release or backing), and finally is wound into a roll of adhesive tape or label stock.

The pressure sensitive adhesives of the invention also may advantageously be used in the manufacture of adhesive articles including, but not limited to, industrial tapes and transfer films. Single and double face tapes, as well as supported and unsupported free films are encompassed by the invention. In one embodiment, the adhesive article comprises an adhesive coated on at least one major surface of a backing having a first and second major surface. Useful backing substrates include, but are not limited to foam, metal, paper, fabric, and variou:s polymers such as polypropylene, polyamide, polyester, polyethylene terephthalate, and mixtures thereof. The adhesive may be present on one or both surfaces of the backing. When the adhesive is coated on both surfaces of the backing, they can be the same or different.

The invention can be Illustrated by the following non-limiting examples.

EXAMPLES

In the Examples that follow, the following tests were used.

Viscosity: Brookfield Viscometer with Thermosel heating unit, spindle 27.

-11 00

O

O

Coating/Bonding/ Conditioning: c, All coatings were 2 mils on a 1.5 mil PET backing. All bonds were made 00 tC automatically using a Chemsultants automated roller (4.51b). All conditioning and testing was done at 731/50% RH unless noted otherwise.

(N

Loop tack:

O

0 Coatings were tested In a TMI loop tack tester against smooth stainless steel panels.

0 Peel: Coatings were bonded to stainless steel panels, given 20 minutes to complete wet out, and then peeled at 12 inches/min.

Shear: Coatings were bonded with a 1 inch x 1 inch overlap to stainless steel panels and then conditioned for 20 minutes. For room temperature shears (73°F) a weight of 2 kg was hung and time to failure was recorded. For elevated temperature shears, the bonded and conditioned samples were transferred to an oven at 2001F and allowed to thermally equilibrate ior 15 minutes, and then a 500 gram weight was hung from the sample.

SAFT (Shear Adhesion Failure Temperature): Shoar samples were prepared as described above. These samples were allowed to equilibrate in an oven for 15 minutes, in most cases starting at 180 9 F-200QF, and then a 500 gram weight was hung. Subsequently the temperature of the oven was increased 1 0F every minutes until failure was noted or 300aF was reached.

Free Swell: Adhesive tapes prepared as described above were weighed and then immersed in cyclohexane. The adhesive coating released from the backing upon swelling and was weighed, as: was the dried backing material. The weight of the swollen adhesive film was -12weighed periodically until its weight had equilibrated. The equilibrium weight of the swollen gelled adhesive network was compared to the initial weight prior to immersion in cyclohexane.

Uncured adhesives are completely soluble in cyclohexane.

Example 1 Various block copolymers that may be used in preparing adhesive formulations of the invention are described in Table 1.

Table 1 Styrene Diblock Linear or Radial MFI EKP 207 0 0 L High SEBPS Septon 4077 30 0 L <1 (SEP)x Kraton G 1780 8 0 R Kraton G 1750 0 0 R SEPEP Kraton G 1730 22 0 L 13

(SEB)

2 -X-1 2 Kraton GRP6919 18 0 R SEBS Kra:on G 1657 13 29 L 8 SEPS Septon 2043 13 43 L 3 PIB Vistanex LM-H-LC 0 Adhesive samples were prepared by melting and mixing until homogeneous componerts listed in Table 2 by weight). Mix temperatures were held at about 300*F.

Where styrenic block copolymers were used, the block copolymer was masticated at high shear with oil and antioxidant and then the tackifiers were slowly added. The remaining oil and epoxidized block copolymer was added at the end of the reaction. Photolnitlator was added during the mastication step if added neat. If already dispersed in epoxidized block copolymer, it was added in the final charge to minimize coalescence of the photolnitiator particles.

-13- Table 2 Sample Sample Sample Sample Sample Sample A B C D E F EKP207 21 21 21 21 21 21 (SEP)x Kraton G 1780 8 10 (EP)x Kraton G 1750 5

(SEB)

2 Kraton G RP6919 8 SEBS Kralon G 1657 8 SEPS Septon 2043 PIB Vistanex LM-H-LC Escorez 5400 55 52 52 50 45 12 15 15 15 15 Irganox 1010 0.5 0.5 0.5 0.5 0.5 UVI 6974 In EKP 207 4 4 4 4 4 4 Viscosity (cP) 2750 F 5250 1790 1208 1785 19950 21500 325 "F 1905 435 463 685 7800 4140 EKP 207 Is an epoxldlzed Isoprene/ethylene butylene dlblock copolymer available from Kraton Polymers and described ab)ve in more detail.

(SEP), Kraton G 1780 is a styrene/ethylene propylene >4 armed radial block copolymer available from Kraton Polymers.

(EP)x Kraton G 1750 is an ethylene propylene >4 armed radial polymer available from Kraton Polymers.

(SEB)-X-l 2 K raton G RP6919 Is a four armed block copolymer available from Kraton Polymers described above.

SEBS Kraton G 1657 is a high diblock linear styrene/ethylene butylene block copolymer available from Kraton Polymers.

SEPS Septon 2043 is a high diblock linear styrene/ethylene propylene block copolymer available from Kurary.

PIB Vistanex LM-H-LC Is a low molecular weight polylsobutylene available from ExxonMobll.

Escorez 5400 Is a highly hydrogenated dicyclopentadlene-based hydrocarbon tackifler available from ExxonMobll.

Britol 35T Is i parafflnic white oil available from Witco.

Irganox 1010 is a hindered phenol antioxidant available from Clba-Gelgy.

UVI 6974 in EKP207 Is a dispersion of a triarylsufonium hexafluroantlmonate (UVI 6974 available from Union Carbide) In EKP 207 obtained from Kraton Polymers.

Adhesive properties of the cured adhesives on stainless steel are shown In Table 3.

These samples were prepared by coating directly onto the 1.5 mil mylar backing using heated rollers, placing the coating on a glass plate at 70QC, thermally equilibrating for 10 minutes, then passing the warm sample under a 300 watt/in Fusion H bulb at 20 ft/mln. Samples were allowed to completely cure for at least 3 days before testing.

-14- Table 3 Sample Sample Sample Sample Sample Sample A B C D E F Loop Tack (oz/in 2 23 ±18 51 15 62 5 44 3 28 8 Peel (Ib/in 12in/min 4.7± 0.1 3.7±0.07 3.5 ±0.1 2.4 ±0.1 2.4 ±0.2 Shear (hrs) at RT, 2 kg >290 (hrs) at 200 2 F, 500g 1 >24 0.1 >24 >24 SaEmples A-F were all compatible In the melt, with no tendency for separation upon stanidng in the molten state. In addition, the adhesives were all solid materials, which did not cold flow upon standing to take the shape of their container. These examples demonstrate that saturated styrenic block copolymers can be used to create solid, melt-applied adhesives using an eooxidized block copolymer as the base. The best PSA property balance was obtained with Kraton GRP 6919 (sample Good peel and tack and excellent shear at elevated temperature were recorded.

The other advantage of adding these saturated block copolymers is that the adhesives have better hot tack and green strength prior to cure. Such properties are especially useful in high speed melt applied applications such as in-line labeling.

Example 2 This example compares a prior art adhesive (Sample G) with an embodiment of the invention (Sample The formulations of these adhesives are described in Table 4.

Table 4 Sample G Sample H EKP-207 18.52 24.8 L-1203 34.4 0 Kraton GRI6919 0 Regalite Ti 140 46.99 0 KR-61 0 0 Escorez 5400 0 42 Abitol E 0 Britol 35T 0 8 irganox 10-10 0.5 UVI-6974 0.08 0.2 Viscosity(cP) 1 509F 20700 1859F 4700 2250F 1330 2759F -1865 3259F L-1 203 Is an ethylene butylene end-functional mono-al with a molecular weight of 4200 g~mol available from Kraton polymers.

Regailte Ti 14) Is a hydrogenated hydrocarbon wth a softening point of 1400 available from Hercules.

KR-610 Is a hy'drogenated rosin available from Arakawa Chemical Co.

These samples were run at either 30 fpm and 25% UV bulb power or 40 fpm and 33 power on an I MC coater using a 450 Watt/In Aetek H bulb (thus each adhesive received roughly an ioquivalent dose of UV light). Adhesive was coated to release paper (Akrosil 132H SC) and transferred to 1.5 mil PET backing (Flexel Inc. item #05907).

Adhesive properties of the cured adhesives on stainless steel are shown in Table -16- Table Speed Thickness Loop Tack Peel (Ibln) SAFT *Shear (hrs) Adhesive (mils) oz/In2 20 min. (2F) 200 9 F, 1 psi Observations Sample G 40 5 109±18 7.41±0.29 >300 all >20 No failure 9-10 108*13 6.96±0.13 0.1,1,4 Adhesive failure Sample H 30 4-5 134±8 7.70±0.21 >300 all >20 No failure 9-10.5 157±10 7.34±0.23 all >20 No failure *Triplicate te.t numbers reported Sample G is an example of a prior art adhesive designed for high peel. Sample H is an example of an adhesive in accordance with the Invention in a form suitable for PSA application:3. Sample H is a solid adhesive that is easier to handle. It is less expensive because it avoids the use of the expensive specialty mono-ol (L1203) recommended in the prior art ref rences from Kraton Polymers Dupont and M. Masse, Adhesives Age, March 2001, p. 18). The invention instead uses inexpensive mineral oil and a more effective monool for develbping PSA properties, rosin alcohol. The formula is less expensive, exhibits better elevated temperature adhesion, better tack, and slightly higher peel.

Example 3 The free swell in cyclohexane of Samples C and H were compared. Sample C exhibited a 77% Increase In weight whereas the Sample H was 180% heavier. The higher swell of sample H indicates a looser crosslinked network, despite the higher polymer content.

This looser network is probably due to chain transfer reactions to the rosin alcohol present in Sample H during radiation cure. A looser crosslinked network is desirable for improved pressure sensitive properties, as are obtained with Sample H versus Sample C.

Many modifications and variations of this Invention can be made without departing from its spirit and scope, as will be apparent to those skilled In the art. The specific embodiments described herein are offered by way of example only, and the invention is to be -17limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

-18- N \Melboume\Cases\Patent\48000-48999\P48697 AU 1\Speas\P48697 AU 1 Specification 2008-7-28.doc 28/07/08

Claims (7)

1. 2. The adhesive of claim 1 comprising a saturated styrenic block copolymer. IC C 3. T7he adhesive of claim 1 comprising a rosin derived alcohol. 00
2. 4. The adhesive of claim 1 wherein the adhesive further comprises a hydrocarbon resin, a Srosin and/or rosin ester, and an oil. The adhesive of claim 1 wherein the photoinitiator is triaryl sulfonium hexafluoroantimonate.
3. 6. "he adhesive of claim 1 which is a pressure sensitive hot melt adhesive.
4. 7. The adhesive of claim 1 wherein the adhesive comprises from about 15% to about by weight of at the epoxidized block copolymer, from about 5% to about 15% by weight of at least one saturated block copolymer and from about 30% to about 60% by weight of at least one hydrocarbon resin and from about 3 to about 15% of a rosin derived mono-ol, up to about 0 to about 25% of a rosin and/or rosin ester, up to about 0 to about 30% of a mineral oil, and up to about 2% of an antioxidant.
5. 8. An article of manufacture comprising the adhesive of claim 1.
6. 9. The article of claim 8 which is a labeled container. The article of claim 8 which is an adhesive tape.
7. 19- N:\Melboume\Cases\Patent\48000-48999\P48697.AU 1\Specs\P48697 AU. 1 Specification 2008-7-28.doc 28/07/08