CA2109826C - Radial block copolymers, hot melt adhesive compositions, and articles produced therefrom - Google Patents

Abstract

Radial block copolymers characterized by the formulae: (1) (pS-pI)n X and (2) (pS-pI-pB)n X where pS is polystyrene, pI
is polyisoprene, pB is butadiene, X is a residue of a multifunctional coupling agent used in the production of the radial block copolymer, and n is a number greater than 2 representative of the number of branches appended to X; hot-melt adhe-sive compositions constituted of said radial block copolymers, and articles of manufacture produced therefrom. These com-polymers possess blocks of high average molecular weight polystyrene (10,000 to 25,000) and an overall average molecular weight (90,000 to 380,000) such that when blended in requisite proportions with a compatible tackifier resin, preferably also a secondary tackifying resin or plasticizing oil, and stabilizer, superior hot-melt adhesive compositions can be formed. The hot-melt adhesive compositions possess, inter alia, superior heat resistance, superior static time to failure with low viscosity, good peel adhesion, good tack, and high ability to bond to a polyethylene or polypropylene substrate at temperatures below that which may damage the substrate.

Description

&DIAL $I,C1CY ~:OP~L. H~"JC ~.T ADHESIV$S
COI~POSI"TIOI~S, AsND ART3:C'L,ES P~DU~ED T$'~EF1Et021 1 1. Piald of the lavaatioa This ~.avaat~.oa relates to radial black 3~ copoly:ars, hot-salt adhesive cos~positioas, aad articles foraad or coastrnctad tharafroa. Xa parti-__. cular, it relates to rad.~.a1 block c~opolymars consti-6 toted of xasiaous ~aolystyraaa block sa~ssats aad rasiaous polydiaaa block s~a~a~aats, :pacifically a 8 polyisopraaa black ox a pradomiaaatly polyisopraae 9 black coataiaia~ polybutadiaaa, and to inprovad hot-ll) relt adhesive co~apasitioas fora~ad fror sand 'block 1.1 copoly:ars, especially asdhasi~was of a typo ~nsatnl is 1:2 the assasbly of d~.xpoaabla arti,clas, particx~larly 1:3 disposable articles ~rhirai.a the hot-halt adhesive 1.4 cos~position is amp".~oyad i.a the coastructioa to boad a 15 poly ethylaaa or po:lypxopyl.aaa substrata to a i:issaa, 16 noa-vovaa fabric or absorbent laff.
I7 2. $ackt~ronnd 18 Lt is kaa~rn to prepare hot-salt adhesive 19 coxpositioas from polystyraaa-polyisopraaa-20 polystyraaa aad pa:Ly:tyrant-polybutadiaae-polysty-21 raga block eopo:lyserx . Liaaar polystyraae-po;lyiso-2.2 praaa-pal3rstpraaa black copalyxax°s w hot melt adhesive ~3 costpositioas bared oa tha~ra black copolyaars, s4 artielas produced frost these adhesives, are disclosed 1 T3 L1 . s . P d ~ -G' I7~ ~ ~i ~ . ~~' ~ ~" °~ ~3 , WO 92/20725 PCT1US92l04334 ~.iil~;~<~~ -_2 _ 1 supra. The linear polystrene-polyisoprene-polysty-2 rene block copolymer; or linear, pS-pI-pS block 3 copolymer, disclosed by this application is characte-4 rized by any of the formulas: (1) pI-(pS-pI)n, .
S where n is.,2, or greater than 2t (2) pS-(pI-pS)n, 6 where a is 1, or greater than 1; or (3) (pS-pI)n, 7 where n is 2, or greater than 2; wherein, is any of 8 formulas (1), (2) or (3), pS is a polystyrene block 9 having an average molecular weight ranging from about 12,000 to about 20,000, preferably from about 14,000 11 to about 19,000, pI is a polyisoprene block having an 12 average molecular weight ranging from about 30,000 to 13 about 70,000, preferably from about 35.000 to about 14 60,000, the overall molecular weight of the block copolymer ranges from about 60,000 to about 110"000, 16 preferably from about 70,000 to about 95.000, and the 17 polystyrene block pS components are present is an 18 amount of at least about 27 parts to about 50 parts, 19 ~ preferably from about 35 parts to about 45 parts, per 100 parts by weight of the block copolymer. The 21 pS-pI-pS black copolymer, in all embodiments is char-22 acteri:ad by the presaace of a pI block, or polyiso-23 prune block, located between two pS blocks, or 24 polystyrene blocks which may or may not be terminal endblocks. The pS-pI-pS block copolymer can thus be 26 either a tribloek or mufti-block copolymer, though 27 the triblock copolymer is preferred.
28 The hot melt adhesive composition is coa-29 stituted of the pS-pI-pS block copolymer, a compati-b1e primary tackifier resin, preferably also a 31 secondary tackifier or plasticizing resin or plaeti-32 sizing oil, and stabilizer. These block copolymers, 33 when bleadad in the requisite proportions with these 34 components, produce adhesives with high shear holding power and shear adhesion failure temperature, and a 5 PC.'T/US92/04334 c~ .~ n ~S C> ~ ~'' i.~ .~ ~ ,.l J N t) 1 low overall molecular weight sufficient to provide 2 low viscosity. These adhesives have, inter alia, 3 bees found admirably suitable for the construction of 4 disposable articles wherein the adhesive is applied ~ as a continuous or discontinuous phase between 6 members, e.g.. via brushing, spraying or air-eztru-7 sion, between members to be bound together, particu-8 larly disposable articles of mufti-line construction 9 wherein the adhesive is supplied as fine parallel longitudinal strips, or as a mufti-dot pattern of 11 adhesive droplets, to bond together a moisture 12 impervious outer polyethylene or polypropylene sheet 13 and an inner moisture adsorbent sheet, or tissue, as 14 used in diaper constructions. They have also been found suitable for use in the construction of Z6 sanitary napkins, bed pads, and with or without the I7 addition of other materials, are useful far packaging 18 and carton sealing, magazine and book lining, or book . binding, or as elastic glues generally.
21 Adhesives formed from this type of pS-pI-pS
22 block copolymer has been found admirably suitable, 23 e.g.. in thm production of "mufti-line" (or multi-24 dat) constructions. Rot-melt adhesives applied in the form of fine parallel longitudinal strips (or as 26 patterns of dots) have been found to possess suffi-27 cleat adhesive and cohesive strength to provide high 28 bond strength values so that when subjected to stress 29 the constructions cannot be easily separated.
Moreover, the adhesives can witlistand high mizsag and 31 application temperatures without thermal degradation 32 and loss of adhesive properties, and have good heat 33 and ozidation resistance on aging. The adhesives 34 also perform well at moderate temperatures, Which is required since the disposable articles are worn at .. _ Q _ .. ~~ ~ ~
1 body temperature; and they also perform well at 2 higher temperatures, which is also required since the 3 constructed articles must also be ezposed to elevated 4 temperatures during warehousing and shipping.
Furthermore, these hot-melt adhesives have low adhe-6 sive viscosity such that they can be applied at low 7 temperature fn order to avoid distortion of the 8 polyethylene or polypropylene substrates to which the 9 adhesive is applied. Nonetheless, there remains a need for hot-melt adhesives useful in magazine and 1l book binding, elastic gluing operations generally, 12 hot-melt adhesive compositions useful in the assembly 13 of mufti-lice constructions, and disposable articles 14 of mufti-line construction formed from improved hot-melt adhesive compositions.
16 3. Objects 17 It is, accordingly, a primary objective of 18 this invention to fulfill these and other needs.
19 . A particular object of this invention is to provide novel radial block copolymers constituted of 21 a polystyrene block sagmeat sad a polydiena block 22 segmaat, viz. a polyisopreae block or a polyisopreae 23 block containing some polybutadieae, and improved 24 hot-melt adhesive compositions particularly useful in the assembly of disposable articles of manufacture, 25 particularly disposable articles of mufti-line 27 construction, formed from such radial block copoly-28 mars.
29 A further, and more particular object is to provide hot-malt adhesive compositions which have 31 superior heat resistance, superior static time to 32 failure with low viscosity, good peel adhesion, and 33 good tack sad high ability to bond to a polyethylaae 34 or polypropylene substrate at temperature below that which would be injurious to the substrate.

- 5 - l., i U ~ ~ t~ ~) 1 A further, and yet more specific object is 2 to provide disposable articles as previously des-. 3 cribed, particularly disposable articles of multi-4 line or multi-dot construction, wherein a polyethy-S lens or polypropylene substrate is bonded to a 6 tissue, or nan-woven polyethylene or polypropylene 7 substrate, or both, via the use of said improved hot-8 melt adhesive compositions.
9 4. The Invention These objects aad others are achieved pur-11 suant to the practice of this invention, embodying a 12 novel radial block copolymer constituted of resinous 13 polystyrene block segments and resinous polythene 14 block segments, suitably a polyisoprene black or a predominantly polyisapsene block containing a rela-16 tively small amount of polybutadiene, and a novel 17 hot-melt adhesive composition comprising said novel 18 copolymer, compatible primary tackifier resin, 19. preferably also a secondary tackifier resin or plasticizing oil. and stabilizer. The hot-melt 21 adhesive composition is, in particular, comprised of 22 said radial block copolymers the polystyrene blocks 23 of which are sufficiently high average molecular 24 weight to provide, inter alia, when blended in the requisite proportions with a compatible tackifier 26 resin, preferably also a secondary tackifier resin or 27 plasticizing oil, aad stabilizer, high shear holding 2$ power and shear adhesion failure temperature, and a 29 low overall molecular weight sufficient to provide low viscosity.
31 The novel radial polystyrene-polyisoprene 32 or polystyrene-polyisopreae/polybutadiene block 33 copolymer is characterized by the formulas:

WO 92%20725 PCT/US92/04334 ;, , , ~l ~, _ 6 " ., .~ :W ~ t~ ~
1 (1) (pS-pI)nR
2 (2) (pS-p~I-pB)nR
3 where pS is polystyrene, pI is polyisoprene, pB is 4 polybutadiene, R. is a residue of a multifunctioaal coupling agent used in the production of the radial 6 block copolymer, cad n is a cumber greater thaw 2, 7 and representative of the cumber of branches appended 8 to R. The number a, for (pS-pI)a R block copolymers, 9 will on the average range from above 2 to about 10, 6, preferably above about 3 to about 5; and for 11 (pS-pI-pB)n X block copolymers, on the average will 12 range from above about 3 to about 7, preferably above 13 about 3.5 to about 4. In either formula (1) or (2), 14 pS is a polystyrene block having an average number molecular weight ranging from about 10,000 to about 16 25,000, preferably from about 14,000 to about 20,000, 17 and pI is a polyisoprene block having as average 18 number molecular weight ranging from about 20,000 to 19 about 70,000, preferably from about 20,000 to about '40,000. In formula (2), pI-pB is a polyisoprene/
21 polybutadieae block, or polyisoprane block an end of 22 whieh contains butadiene, or polybutadiene, and the 23 pI-pB component is one having a total average number 24 molecular weight ragging from about 20,000 to about 70,000, preferably from about 20,000 to abaut 26 40,000. The overall mumber average molecular weight 27 of the radial block copolymer is accordance with 28 either formula (1) or formula (2) ranges from about 29 90,000 to about 380,000, preferably from about 100,000 to about 240,000, more preferably 3I from about 120,000 to about 200,000, and the polysty-32 rene block pS components are present in an amount of 33 at least about 25 parts to about 50 parts, preferably 34 from about 27 parts to~about 45 parts, per 100 parts by weight of the radial block copolymer.
::v .~~ PCf/US92/04334 ~~~~iJ~.~.il 1 The radial block copolymers of this in-2 invention are thus constituted of resinous polysty-3 rene block segments aad resinous polydiene block 4 segments, suitably, in accordance with formula (1), S of polyisoprene, pI; or, in accordancq with formula 6 (2), of polyisoprene and polybutadiene, pI-pB. Thus, 7 styrene is employed to make the resinous pS block 8 segments of bath the (pS-pI)nR and (p5-pI-pB)nX
9 block copolymers. In accordance with formula (1), isoprene is employed to make the resinous pI block 11 segments, the (pS-pI) polymer chains being formed by 12 saqueatial polymerization of isoprene with the pS.
13 The (pS-pr) polymer chains, suitably as pS-pI-Li 14 laving polymer chains, are coupled with coupling agents possessing at least three, and preferably four 16 sites reactive toward carbon-lithium bonds, e.g., 17 SiCl4, to form the radial or multiblock (pS-pI)ng 18 copolymer. In forming the radial or multiblock 19 copolymer described by formula (2), i.e., (pS-pI-pB)nR, pS-pI-pB-Li polymer chains are formed 21 by the sequential polymerization of living pS-pI-Li 22 polymer chains with butadiene. The radial or multi-23 block (pS-pI-pB)aX copolymers are correspondingly 24 made by coupling the pS-pI-pB-L i living polymer chains r~ith the mufti- or tetra functional coupling 26 agent, e.g., SiCl4. Thus, the styrene is polymer-27 ized to form pS, the isoprene is then introduced to 28 form pS-pI, the butadiene is then introduced to form 29 pS-pI-pB, and the pS-pI-pB chains are then coupled with the tetrafunctional coupling agent to form the 31 (pS-pI-pB)nR radial or multiblock polymer. In the 32 pI-pB segment of the (pS-pI-pB)aX polymer, the 33 polyisoprene is present is amount sufficient to 34 impart predominantly polyisoprene characteristics.
not butadiene or polybutadiene characteristics, to WO 92/20725 1PC'C/US92/04334 ~~.i~~'~'~O - s -1 the polymer. Thus, in the pI-pB segments of the 2 polymer, the weight amount of polyisopreae will 3 ezceed 50 percent of the total weight of dieae in the 4 polymer, i.e., pI/(pI + pg) > 50 wt.~. Conversely, S the weight amount of butadiene or polybutadieae will 6 be less than 50 percent of the total weight of diene 7 in the polymer, i.e., p8/(pI + pB) < 50 wt.~.
8 Preferably the polybutadiene portion of the dieae 9 segment is less thamm 10 percent, most preferably less than 5 preceat, based on the total weight of the 11 (pI + p8), or dieae component of the polymer.
12 The small amount of butadiene at the end of 13 the diene midblock is useful in that it enhances the 14 coupling reaction is formation of the polymer, and results is a radial polymer with a higher aumber~of 16 branches. A further description of the process at 17 this point will facilitate as uaderstaading of this 18 feature of the invention. The radial polymers of 19 this invention are thus synthesized by first contact-20' ing styrene polymer with an initiator, suitably e.g., 21 a sec-butyllithium initiator, is the presence of as 22 inert dilusnt, e.g.. cyclohezane. A living polymer 23 is then formed, as repsesantad e.g., by the simpli-24 fied structure pS-Li. The living polystyrene polymer pS-Li is aezt contacted with an isoprene monomer;
25 the resulting product being represented by the 27 simplified structure pS-pI-Li. The living polymer is 28 then "coupled" by reacting the pS-pI-Li with a multi-29 functional coupling agent, or agent which has three or more sites. e.g., SiCl4, to produce a polymer with 31 a radial or branched structure which may be repreaea-32 ted as (pS-pI)nR, where R is a residual of the multi-33 functional coupling agent, and n is a number greater 34 than 2. Alternately, tha living polymer pS-pI-Li can be contacted with a small amount of butadiene monomer WO 92/20725 ~ ~ ~ k~ ~, y ~ PCT/US92/04334 _ g 1 to produce a living polymer with the structure 2 pS-pI-pB-Li, where pB represents butadiene or 3 polybutadiene. Coupling of the pS-pI-pB-Li with the 4 coupling agent produces a branched block copolymer S ~ with the structure (pS-pI-pB)aR. The radial polymer 6 that is produced, using SiCl4 as a coupling agent, 7 will on the average produce (pS-pT-pB)aR polymers 8 where n approximates 4, whereas, in contrast, in 9 producing (pS-pI)aZ polymers is an otherwise similar manner it will be found that n will more closely 11 appro:imate 3. The butadiene need b a added only in 12 amount necessary to assure that the ends o~ all of 13 the pI segments of the polymer chains are provided 14 with at least one molecule of butadiene, though as suggested the butadiene can be added in larger 16 amounts. The radial block eopolymers of this 17 invention, in either event, have been found to pro-18 dace unexpectedly good hot melt adhesives when com-19 bined with suitable tackifier resins, plasticizer 20' oils, and antioxidants.
21 Useful coupling agents are those possess-22 ing three or more, preferably four, sites reaetive 23 toward carbon-lithium bonds. Suitable coupling 24 agents are those compositions of the formula %(L)n where R represents the eoupling moiety residue, 25 and L is a suitable leaving group. Exemplary of 27 coupling agents of this type are silica halides, 28 e.g.. SiCl4, or a silane compound where one or more 29 of the halides is substituted by a hydrocarbyl group, e.g., methyl trichlorosilane; epoxy compounds, e.g., 31 epoxidized linseed oil, epaxidized soybean oil;
32 acrylate mufti esters, e.g., pentaerythri:ol tetra-33 acrylate; epoxy silaaes; divinyl compounds, e.g..
34 divinyl bansene, and the like.

~~.iv~c~r.,~> - to -1 The hot-melt, adhesive composition is, is 2 particular, comprised of from about 15 percent to 3 about 35 percent, preferably from about 20 gereent to 4 about 30 percent, based on the weight of the hot-melt 6 adhesive composition, of said radial block copolymer 7 wherein the pT component or pI-pB component, respect-8 tively, is one having as average molecular weight 9 ranging from about 20,000 to about 70,000, preferably from about 20,000 to about 40.000, the pS component 11 is polystyrene having as average molecular weight 12 ranging from about 10,000 to about 25,000, preferably 13 from about 14,000 to about 20,000, the overall I4 molecular weight. of the block copolymer raages from about 90,000 to about 380,000, preferably from about I6 100,000 to about 240,000, and wherein the pS compo-17 neat-~is present in as amount of at least about 25 18 parts up to about 50 parts, preferably from about 27 19 parts to about 45 parts, per_100 parts by weight of the radial block copolymer; from about 45 percent to 21 about 70 percent, preferably from about 50 percent to 22 about 60 percent, based on the weight of the hot-malt 23 adhesive composition, of a compatible primary tacki-24 fying resin; from 0 pesceat to about 30 percent, preferably from about 5 percent to about 20 percent, 26 of a plasticizing oil, or secondary tackifyiag reaia, Z7 or both, based on the weight of the hot-melt adhesive 28 composition; aad from about 0.1 percent to about 2 29 percent, preferably from about 0.5 percent to about 1.5 pesceat of a stabilizer, based on the weight of 31 the hot-melt adhesive composition.
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WO 92/20725 ~ y ~ ~ ~ ~ ~ PCT/US92/04334 1 These hot-melt adhesive compositions, con-2 stituted of a (pS-pI)n X or (pS-pI-pB) X radial block 3 copolymer of intermediate to relatively high styrene 4 content and overall low molecular weight to which the primary tackifying resin, the secondary tackifying 6 resin or plasticising oil, and stabiliser have been 7 added, have bees found to possess properties which 8 are admirably suitable for the construction of 9 disposable articles wherein the adhesive is applied as a continuous or discontinuous phase, or substrate, 11 between members, e.g., via b rushing, spraying or air-12 extrusion, between members to be bound together, 13 articles. particularly disposable articles o~ multi-14 line construction wherein the adhesive is applied as fine parallel longitudinal strips, swirled, or as,a 16 mufti-dot pattern of adhesive droplets, to bond 17 together a moisture impervious outer polyethylene or 18 polypropylene sheet and an innex moisture absorbent 19 sheet, or tissue, as used in diaper constructions.
~ Thsse adhesive compositions have also been found Z1 suitable for use,in the construction of sanitary 22 napkins, bed pads, and, with or without the addition 23 of other materials, are also useful for packaging and 24 carton scaling, magazine and book lining, or book binding, or as elastic glues generally. These hot-26 melt adhesive compositions can be melted, and 27 maintained under a blanketing nitrogen atmosphere, at 28 selatively low to high temperatures without thermal 29 degradation. The compositions can be applied in fluid form to polyethylene and polypropylene sub-31 strates as continuous or discontinuous films, 32 suitably as fine lines or as patterns of sulti-dots, 33 without any risk of damage to the polyethylene or 34 polypropylene substrate: These hot-melt adhesive compositions have also bees found to serve a con-WO 92/20725 ~ ~ ~ ~ ~ ~) J - 12 - PCTlL~S92/04334 .
1 structioa function in binding together an outer 2 sheet, or wrapper overlapped with an absorbent pad as 3 required in the eonstruction of sanitary napkins.
4 The hot-melt adhesive composition applied as a fluid permeates the overlapped area to bind and seal the 6 absorbent pad inside the outer sheet which serves as 7 a Wrapper.
8 The primary tackifying resins useful in the 9 practice of this invention include hydrocarbon resins, synthetic polyterpeaes, rosin esters and 11 natural terpenes which are semi-solid or solid at 12 ambient temperatures, and soften or become liquid at 13 temperatures ranging generally from shout 70°C to 14 about 135°C, preferably from about 85°C to about 120°C. Exemplary of the primary tackifying resins i6 are compatible reline such ere (1) natural and 17 modified rosins such, for ezample, as gum rosia, wood 18 rosin, tall oil rosin. distilled eosin, hydrogenated 19 rosin, dimesi~ed rosin, and-polymerized rosier;
(2) glycerol and pentaesythritol esters of natural 21 and modified rosins, such, for example, as the 22 glycerol ester of pale, wood rosin, the glycerol 23 ester of hydrogenated rosin, the glycerol ester of 24 polymesixed rosin, the pentaerythritol ester of hydrogenated eosin, and the phenolic-modified 2~6 pentaerythritol ester of rosin; (3) copolymers and 27 terpolymess of matured tespanes, e.g., styrene/
28 terpene and alpha methyl styrene/terpane; (4) 29 polyterpene resins having a softening point, as determined by ASTM method E28-58T, of from about 80°
3.1 to 150°C; the latter polyterpene resins generally 32 resulting from the polymerization of terpene hydro-33 cnrbone, such as the bicylic monoterpene known as 34 pinane, is the presence-of Friedel-Crafts catalysts at moderately low temperatures; also included are WO 92/20725 ~ ~ ~ ~ ~ PCT/1JS92/04334 1 the hydrogenated polyterpene resins; (5) phenolic 2 modified terpene resins and hydrogenated derivatives 3 thereof such, for a:ample, as the resin product 4 resulting from the condensation, in an acidic medium, of a bicyclic terpene and a phenol; (6) aliphatic 6 petroleum hydrocarbon resins having a hall and Ring 7 softening point of from about 70° to 135oC; the 8 latter resins resulting from the polymerization of 9 monomers consisting primarily of olefins and diole-fins; also included are the hydrogenated aliphatic 11 petsoleum hydrocarbon resins; (7) aromatic petroleum 12 hydrocarbon resins, and mined aromatic and aliphatic 13 paraffin hydrocarbon resins, and the hydrogenated 14 derivatives thereof; (8) aromatic modified alicyclic petroleum hydrocarbon resins and the hydrogenated 16 deriv.ities thereof; and (9) alicyclie petroleum 17 hydrocarbon resins and the hydrogenated derivatives 18 thereof. The preferred primary tackifying resins for 19 use in the practice of this invention are represented ~ by sub-paragraphs (1), (3) and (7), supra. Suitable 21 secondary tackifyiag resins are those aamed species 22 wherein the resin is a liquid at ambient tempera-23 tuts.
24 Various plasticizing oils are useful in the practice of this invention. The plasticizing oil can 26 be used in place of or in combination with the 27 secondary tackifier to reduce viscosity and improve 28 tack properties. Plastieiziag oils which have been 29 found useful include olefin oligomers and low molecu-lar weight polymers as well as vegetable and animal 31 oil and their derivatives. The petroleum derived 32 oils which may be employed are relatively high 33 boiling materials containing only a minor proportion 34 of aromatic hydroearboas (preferably less than 30x and, mare particularly, less than 15~ by weight of WO 92/20725 Pt.'T/US92/04334 a~ - 14 'Z ( > r F:.~y.~C5~i1 -1 the oil). Alternately, the oil may be totally noa-2 aromatic. The oligomers may be polypropylenes, poly-3 butanes, hydrogenated polyisoprene, hydrogenated 4 polybutadieae, polypiperyleae and copolymers of piperylene and isoprene, or the like having average 6 molecular weights between about 350 and about 7 10,000. Vegetable and animal oils include glyceryl 8 esters of the usual fatty acids and polymerization 9 products thereof.
1O The stabilizer, or antioxidant, used in 11 accordance with the practice of this invention in-12 eludes high molecular weight hindered phenols and 13 multifunctional phenols such as sulfur and phoapho-14 roes-containing phenols. Hindered phenols are well known to those skilled is the art and may be charac-16 terized as phenolic compounds which also contain 17 sterically bulky radicals is close proximity to the 18 pheaolic hydroxyl group thereof. In particular, 19 tertiary butyl groups generally are substituted onto 20' the benzene ring is at least one of the ortho posi-21 tioas relative to the g~heaolic hydroxy group. The 22 presence of these sterically bulky substituted radi-23 eels in the vicinity of the hydroxyl group serves to 24 retard its stretching frequency and, correspondingly, its reactivity: this steric hindrance thus providing 26 the pheaolic compound with its stabilizing proper-27 ties. Representative hindered phenols include:
28 1,3"5-trimethyl 2,4,6-tris (3,5-di-tart-butyl-4-29 hydroxybenzyl) benzene; pentaerythrityl tetrakis-3 (3,5-di-tertbutyl-4-hydroxyphenyl) propioaste:
31 n-octadecyl-3~3,5-di-tart-butyl-4-hydroxyphenyl)-32 propionate: 4,4'-methylenbis (2,~6-tart-butylphenol);
33 4,4'-thiobis (6-tart-butyl-o-cresol): 2,6-di-tart-34 butylphenol; 6-(4-hydrc~yphenoxy)-2,4-bis(n-octyl-thio)-1.3,5 2I triazine; di-n-octadecyl 3.5-di-tart-WO 92/20725 PC:T/US92/04334 ~a - 15 ~1~J~~
1 butyl-4-hydrozy-benzylphosphonate; 2-(n-octylthio) 2 ethyl 3,5-di-tart-butyl-4-hydrozy-benzoate; and 3 sorbitol [hez 3-(3,5-di-tart-butyl-4-hydrozyphenyl)-pxopioaate.l The hot-melt adhesive composition is pre-6 pared fox use by blendiag the radial block copolymer 7 with the primary tackifying resin, the secondary 8 tackifyiag resin or plasticizing oil, and stabilizer, 9 in any order or sequence, or these materials can be IO added together simultaneously to form the adhesive 11 composition. In commercial practice at would be 12 expected that tha primacy tackifying resia and 13 copolymer, with or without the simultaaeous add ition 14 of the secoadary tackifying resin or plaeticiz-15 ing ail, sad stabilizer, would be blended together 16 at sufficiently elevated temperature to form a fluid 17 melt. For ezample, the copolymer caa be bleaded with 18 the solid compatible primary tackifyiag resin at I9 temperatures ranging from about l3OoC to about 200oC, 28 ~ preferably at from about 150°C to about 180oC, to 21 . form a fluid melt. The secondary liquid tackifying 22 resin, ar plasticizing oil, and stabilizer, can then 23 be added to the melt. Alternatively, the fluid melt 24 can be prepared with all components of the adhesive 25 composition present ab initio.
26 The following non-limiting ezamples, and 27 comparative demonstrations, bring out the more 28 salient features of the invention. All parts are 29 gives in terms of weight units ezcept as may other-30 wise be indicated.
...:..: ,:::: ,.~. .... ~,~:... :..:.:,~ ........ :.... ;; .:. . .

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1 8~ca~p 1 a s 2 Ya coadactia= the foxl.o~riag tests the co:-3 position and properties of the neat radialp and ~4 liaaar block copolymers which were prepared for.
making the adhesive compositions were determined by ~b tachaiques "a." '~b" and '"s:~° ,~ la e~~aluatiag the 'l performance characteristics of the adhesive composi-B boas produced from the radial. and linear block ~3 copolymers test procedures "d" through "f" were IO employed, to its.
11 a. Styrene content -~ of the ezperimental I2 radial, and linear ~~lack copolymers was determined I3 from the proton nmr spectra. Samples were dissolved 1~4 is a mizture of d:utesated tetrachlroethaae/
1' M
I~ tatrachloroethylene, and analysed an a Hruker 90 tiBZ
16 spectrometer. Styrene content ~raa calculated from 1°1 tht spectra by the method of o. D. l~oehel, Rubber 1S Chem. and Tech., 34 40, 1:00 (1967.
1!~ ~~. !it>leculax height - of the ezperimeatal 20 radial, and linear block copolymers vas determiaad by 21 GPC, using the meth°d described by :~. R. R~nayoa, et 2:2 al, J. Pol~m. Sci. ~:3, 23~ig ~ 19693 a 23 c, halt Flow Rate (HFR~ - of the ezperi-24 mental radial. axxd linear ~rlock copolymers was 2S determined according to ASTri method D-123$-82, using 2b condition "G" (2U0°~:, 5 Kg weighty .
d. Adhesive ~Iel.t Vs.scosity (ASTH D-3236) 2S - !felt viscosities were measured at a temperattttre of 29 130°C, using a Brookfield fi'hermc~sel viscometer. Low 30 adhesive viscosities arc a necessity for processing 31 in mufti-lice, spray, and fibers,xatian equipment. In 32 addition, t:he viscosity must be foe at relatively lov 33 proeessin~ temperatures its order tc~ avoid distortion 34 of the polyolefia backing when ~xot adhesive is 35 applied.

..
1 s. Shear Adhesion Failnra Tasparatnre 2 (SA1'T) - is a aeasnre of the ability of the hoed, to 3 ~ithataad an elevated tessperatnre riaiag at 10°F/15 4 sin.. reader a coasxaat force ~rh~.th pulls the boa,d is S the shear mode. Soads 1 inch by 1 inch were formed 6 of adhesive, oa a t~yla: ~i(poiyester) backing, to a 7 stainless steal pane::, using a 4.,~ 1b. robber 8 roller. The panel was suspended vertically is an 9 oven at 32°~:, and al:o~red t:o come tea eqnilxbrius,. A
1 kg weight eras suspended from the free end of the 11 adhesive tape" and the temperature eras raised at 12 10°F/15 rein. The temperature at which the tape sad 13 ~raight fell from the panel eras recorded. SAFT was 14 reported as the average of three such determine-tions. Adhesives poasesaiag high fai,lare teapera-16 tares are essential for the assembly of disposable 17 articles. which are r~ften su~sec.ted t.o very high 18 temperatures during xtorage and shipping. Ia 19 addition, these articles are need ~;~rox7n~ at body temperature,.
21 f ~. Shear Holding Foerer ( Static Time to 22 Failure Bond Test; - The cohesive strength of the ad-23 hesives was determined according to the general pro-24 cedures outlined ;gin hSTG-~7 wad A.ST1~ 11-3554. A ;l inch by 0.~ inch bond vas applied to a stainless 2fi steel papal with a 4,~ 1b rubber roller. Tha plate 27 was snspeadad vertically an~a all.ored to equilibxate 28 at 35°C. A 1 Rg reight eras tuapeaded frog the free 29 end of the tape. The t;ima at which the tape and weight fell from the panel vac recorded. The shear 31 hold (in min) was reported as tine average of four 32 such determinations, Long failx~re times are desir-_ 33 able, since they indicate strong bonds, which are 34 essential in certain areas °f the disposable con-<:. 1,a ..
1 structions, rhich era snbjactad to caasidarabla 2 stress dnrin~ use.
3 Exa:iplas 1-4, rhich imsadiataly follor, 4 describe the synthesis, and curtain characteristics of the (pS-pI-pB)aZ xadial polymers of this iavea-6 tioa. Ezaaples S~°7, ors the other head, describe the 7 synthesis and cartaia characteristics of the 8 (pS-pI)aZ radial polyaars of thin ixiveatioa. Demoa-9 stration 9 f.s a liaear pS-pl-pS linear block copolymer of the t.ar~.~e d~.scr:i.x:~c~c:i in U ' . Paterat 11 ~To. 5, 143, 9E8, :~upa~~.: ~'.t,e ~:r~lwt:~:;x-ri{ax~..;~ of wruch made 12 into an adhesive ~s oubstaatiall;y equivalent to that I3 of the radial bloc. x:apolymars of this invention.
14 Demonstration 8 is s radial styrana~-butadiaaa block copolymer rhich has a: stsruaa content comparable to 16 that of the copolymax~s of this ixavention, but an 17 adhesive produced therefrom has a SAFT parfarmance 18 vhieh is inferior to the radial polyiaxs of this 19 invention. Additionally, for comparative purposes, ZO Demonstrations 1D-~1: represent palymars obtained from Z1 commercial sources, formnlsxed ixeto adhesive composi-22 Lions, and testad4 Damonstrat~.oa I~thus describes Z3 the performance character~at3cs of an adheszve com-24 position formed from a radial. pol.ystyrene-polyhutadiene copolymer produced by Shell Chemical 25 Company; Demonstration 11 an adhesive composition Z7 fozmulated from a linear multiblack polystyrene--28 polybutadiena copolymer produced by ~'irastone Tire 29 and Rubber Company; and Demaactrat:ioa 1Z as adhesive composition farmed from a lisaar po~.ystyrene-polyiso-31 prone-polystyrene copolymer produced by Enichem 32 Americas, Iac.

WO 92/20725 ~ ~ ~ ' U ~~ ~~ PCT/US92/04334 1 The preparation of the block copolymers, 2 and certain characteristics of the block copolymers, 3 as employed in Examples 1 through 7 and Demonstra-4 tions 8 and 9 are given as follows:
Ezample 1 (5145-45) Ta a 5-gallon, stirred reactor under a 7 aitrogen atmosphere were added 12.6 kg of cyclohezane .
8 aad 905 g of styrene. The temperature of the reactor 9 was brought to 50°C and 147 g of a 0.28 M solution of see-butyllithium in cyelohexane was added.
11 Polymerization was allowed to continue for 50 12 minutes. The reaction mixture was cooled to 50°C and 13 1148 g of isoprene was added. The isoprene was 14 allowed to polymerize for 32 minutes during which the reactioa temperature reached a maximum of 68°C. At 16 the end of the 32 miautes, 34 g of butadiene was 17 added and it was allowed to polymerize for an 18 additional 30 minutes. Then I4 g of SiCl4 was added 19 slowly over the course of 11 miautes. The reaction ~ was allowed to continue for another 1S minutes before 21 an excess of isopropanol was added to the reaction 22 mixture to quench any residual Li alkyl. A hindered 23 phenol antioxidant was added to the polymer solutioa 24 which was then devolatilized in a vacuum oven under nitrogen at 100°C for 3 hours.
26 Size exclusion chromatography of the 27 resultant polymer showed two peaks, a high molecular 28 weight peak which was the radial or star shaped 29 polymer comprising 78x of the total polymer and a lower molecular weight peak, comprising 22~ of the 31 total polymer, which was the diblock building block 32 before coupling the chain ends using SiCl4. From 33 gel-permeation chromatography, GPC, it was estimated 34 that each arm of the radial polymer was composed of a polystyrene block of 18,000 molecular weight and ~,.i~~~~J~a - 2O "
1 22,800 molecular weight polythene. The melt flow 2 rate was 61.8. Ultimate tensile of the material was 3 2763 psi.
4 Example 2 (5146-14) To a S-gallon, stirred reactor under a ai-6 trogen atmosphere were added 12.6 kg of cyelohezane 7 and 718 g of styrene. The temperature of the reactor 8 was brought to 50°C and 134.6 g of a 0.317 M solution 9 of sec-butyllithium in cyclohezane was added. Poly-merizatioa was allowed to continue for 60 minutes.
11 The reaction mixture was cooled to 50°C and 1328 g of 12 isoprene was added. The isoprene was allowed to 13 polymerize for 25 minutes duriag~which the reaction 14 temperature reached a maximum of 77°C. At the end of the 25 minutes, 34 g of butadiene was added and it 16 was allowed to polymerize for an additional 18 17 minutes. Then I3 g of SiCl4 was added slowly over 18 the course o~ 6 minutes. The reaction was allowed to 19 continue for another 19 minutes before as excess of 2C' isopropaaol was added to the reaction mixture to 21 quench any r~sidual Li alkyl. A hindered phenol 22 antioxidant was added to the polymer solution which 23 was then devolatilised in a vacuum oven under 24 nitrogen at 100oC far 3 hours.
Size exclusion chromatography of the 26 resultant polymer showed two peaks, a high molecular 27 weight peak which was the radial or star shaped 28 polymer comprising 86x of the total polymer and a 2~ lower molecular weight peak, comprising 14x of the total polymer, which was the diblock building block 31 before coupling the materials using SiCl4. From the 32 GPC it was estimated that each arm of the :adial 33 polymer was composed of a polystyrene block of 16,560 34 molecular weight and 30';620 molecular weight poly-diene. The melt flow rate was 18.7. Ultimate o ~n - 21 - ~, ~. ~~ ~ ~ r,. 0 1 tensile of the material was 4430 psi.
2 Ezample 3 (5146-13) 3 To a 5-gallon, stirred reactor under a ni-4 trogea atmosphere were added 12.6 kg of eyclohezaae ~ and 970 g of styrene. The temperature of the reactor 6 was brought~to 50oC and 139.0 g of a 0.317 M solution 7 of see-butyllithium in cyclohezane was added. Poly-8 merization was allowed to continue for 88 minutes.
9 The reaction mixture was cooled to 50°C and 1086 g of isoprene was added. The isoprene was allowed to II polymerize for 39 minutes during which the reaction 12 temperature reached a mazimum of 66°C. At the cad of 13 the 39 minutes, 34 g of butadiene~was added and it 14 was allowed t9 polymerize for an additional 33 minutes. Then I3 g of SiCl4 was added slowly over 16 the course of 8 minutes. The reactioa was allowed to I7 continue for another 18 minutes before an ezcess of 18 isopropanol was added to the _reaction mizture to 19 quench any residual Li alkyl. A hindered phenol ' antiozidaat was added to the polymer solution which 21 was then devolatilizad is a vacuum oven under 22 nitrogen at 100oC for 3 hours.
23 ~ Size ezelusion chromatography of the 24 resultant polymer showed two peaks, a high molecular weight peak which was the radial or star shaped 26 polymer comprising 87~ of the total polymer and a 27 lower molecular weight peak, comprising 13% of the 28 total palymer, which was the diblock building block 29 before coupling the materials using SiCl4. From the GPC it was estimated that each arm of the radial 31 polymer was composed of a polystyrene block of 20,960 32 molecule= weight and 23,440 molecular weight poly-33 diene. The melt flow rate was 29.4. Ultimate 34 tensile of the material'was 3316 psi.

c,.~f'~y~~~;' -22-~...~U~U~=u 1 Example 4 (5146-16) 2 Ta a 5-gallon, stirred reactor under a ai-3 trogea atmosphere were added 12.6 kg of cyclohezane 4 and 85I g of styrene. The temperature of the reactor was brought to 50°C and 121.8 g o~ 0.317 M solution of sec-butyllithium in cyclohezane was added.
7 Polymerization was allowed to continue for 54 8 minutes. The reaction mixture was cooled to 50°C and 9 1200 g of isoprene was added. The isoprene was allowed to polymerize far 31 minutes during whieh the 11 reaction temperature reached a maximum of 74°C. At 12 the end of the 31 minutes, 34 g of butadiene was 13 added and.it was allowed to polymerize for an 14 additional 20 minutes. Then 12 g of SiGl4 was added slowly over the course of 6 minutes. The reaetion 16 was allowed to eontinue for another 16 minutes before 17 an excess of isopropaaol was added to the reaction 18 mixture to quench any residual Li alkyl. A hindered 19 phenol antioxidant was addedwto the polymer solution 20° which was then deeolatiliaed in a vacuum oven under 21 nitrogen at 100oC for 3 hours.

22 Size exclusion chromatography of the 23 resultant polymer showed two peaks, a high molecular 24 weight peak whieh was the radial or star shaped polymer comprising 87~ of the total polymer and a 26 lower molecular weight peak, comprising 13~ of the 27 total polymer, which was the diblock building block 28 before coupling the materials using SiCl4. From the 29 OPC it was estimated that each arm of the radial polymer was composed of a polystyrene block of 20,730 31 molecular weight and 29,200 molecular weight poly-32 diene. The 20 melt flow rate was 21.9. ultimate 33 tensile of the material was 3500 psi.

25 PCT/L'S92l04334 _ 23 _ ~i~~~~J
1 Example S (5280-18) 2 To a 5-gallon, stirred reactor under a ni-3 trogen atmosphere were added 12.6 kg of cyclohezaae 4 and 901 g of styrene. The temperature of the reactor S was brought to 50°C and 129.2 g of a 0.317 M solution 6 of sec-butyllithium in cyclohexane was added. Poly-7 merization was allowed to continue for 55 minutes.
8 The reaction mixture was cooled to 50oC and 1147.1 g 9 of isoprene was added. The isoprene was allowed to polymerize for 31 minutes during which the reaction 11 temperature reached a maximum of 69°C. At the end of 12 the 31 minutes, 23.7 g of SiCl4 was added slowly over 13 the course of 6 minutes. The reaction was allayed to 14 continue for another 30 minutes befose an excess of isopropanol was added to the reaction mixture to, I6 quench any residual Li alkyl. A hindered phenol 17 antioxidant was added to the polymer solutioa~which 18 was then devolatilized in a vacuum oven under 19 nitrogen at 100°C for 3 hours.
' Size exclusion chromatography of the .
Z1 resultant polymer showed two peaks, a high molecular 22 weight peak which was the radial as star shaped Z3 polymer comprising 82.2x of the total polymer and a 24 loner molecular weight peak, comprising 17.8X of the total polymer, which wan the dibloek building block 26 before coupling the materials using SiCl4. From the 27 ~GPC it was estimated that each arm of the radial 28 polymer was composed of a polystyrene block of 21,021 29 molecular weight and 26,755 molecular weight polyiso-prene. Ths melt ~low rate was 8.1 g/10 minutes.
31 Ultimate tensile of the material was 3620 psi.

WO 92120725 PCf/US92/04334 ~~~~ca~~O - 24 -1 Example 6 (5280-19) 2 To a 5-gallon, stirred reactor under a ni-3 trogea atmosphere were added 12.6 kg of cyclohezane 4 and 714.8 g of styzene. The temperature of the reac-for was brought to 50oC and 111.7 g of a 0.317 Pi 6 solution of~ see-butyllithium in cyelohezane was 7 added. Polymerizatson was allowed to continue for 53 8 minutes. The reaction mixture was cooled to 50°C and 3 1327.4 g of isoprene was added. The isoprene was allowed to polymerize for 41 minutes during which the 11 reaction temperature reached a maximum of 74oC. At 12 the end of the 41 minutes, Z0.5 g of SiCl4 was added 13 slowly over the course of 6 minutes. The reaction 14 was allowed to continue for another 30 minutes before an excess of isopropanol was added to the reaction 16 miztwre to quench any residual Li alkyl. A hindered 17 phenol antiozidaat was added to the polymer solution 18 which was then devolatilized is a vacuum oven under 19 nitrogen at 100°C fox 3 hours.
20" Size exclusion chromatography of the 21 reeultaat polymer showed two peaks, a high molecular 22 weight peak which was the radial or star shaped 23 polymer comprising 78.7X of the total polymer and a 24 lover molecular weight peak, comprising 21.3'Z of the total polymer, which was the diblock building black 26 before coupling the materials using SiCl4. Prom the 27 GPC it was estimated that each arm of the radial 28 polymer was composed of a polystyrene block of 19.138 29 molecular weight and 35.541 molecular weight polyiso-psene. The melt flow rate was 5.7 g/10 minutes.
31 Ultimate tensile of the matexial was 4210 psi.

pcrrus92roa33a 1 Example 7 (5280-20) 2 To a 5-gallon, stirred reactor under a ni-3 trogen atmosphere were added 12.6 kg of cyclohexane 4 and 964.2 g of styrene. The temperature of the reactor was brought to 50°C and 118.5 g of a 0.317 M
6 solution of sec-butyllithium is cycloheaaae was 7 added. Polymerization was allowed to eontiaue .for 53 8 minutes. The reaction mixture was cooled to 50°C and 9 1087.3 g of isoprene was added. The isopremme was allowed to polymerize for 35 minutes during which the 11 raaction temperature reached a maximum of 69°C. At 12 the end of the 35 minutes, 21.8 g o~'SiCl,, was added 13 slowly over the course of 6 minutes. The reaction 14 was allowed to continue for another 32 minutes before an excess of isopropanol was added to the reaction 16 mixture to quench any residual Li alkyl. A hindered 17 phenol antioxidant was added to the polymer solution 18 which was they devolatiliaed is a vacuum oven under I9 nitrogen at 100°C for 3 hours.
20' Size exclusion chromatography of the 21 resultant polymer showed two peaks, a high molecular 22 weight peak which was the radial or star shaped 23 polymer comprising 84.8 of the total polymer aad a 24 lower molecular weight Beak, comprising 15.2 of the total polymer, which was the diblock building block 26 before coupling the materials using SiCl4. From the 27 GPC it was estimated that each arm of the radial 2~ polymer was composed of a polystyrene block of 24,534 29 molecular weight and 27,666 moleeular weight polyiso-preae. The melt flow rate was 8.9 g/10 minutes.
31 Ultimate tensile of the material was 3340 psi.
R...S.;..~i:r . ... . n::~\~mw .Lw.~ aS,., ' .. . ~. ... , . >.. , ~ . " ' , .
.

~~~~~I:~i.f - 26 --1 Demonstration 8 (5145-49) 2 To a 5-gallon, stirred reactor under a ni-3 trogen atmosphere were added 12.5 kg of cyclohezane 4 and 911.6 g of styrene. The temperature of the reactor was brought to 50°C and 170.8 g of a 0.317 M
solution of sec-butyllithium in cyclohezane was 7 added. Polymerization was allowed to continue for 46 8 minutes. The reaction mixture was cooled to 50°C and 9 1123 g of butadiene was added. The butadiene was allowed to polymerize for 46 minutes during which the 11 reaction temperature reached a maximum of 69°C. At 1.2 the end of the 46 minutes, 21.5 g of SiCl4 was added I3 slowly aver the course of 10 minutes. The reaction 14 wss allowed to eontiaue for aaotber 17 minutes before an excess of ieopropanol was added to the reaction 16 mixture to quench nay residual Li alkyl. A hindered 17 phenol antioxidant was added to the polymer solution 18 which was then devolatilized is a vacuum oven under 19 nitrogen at 100°C for 3 hours.
' Size exclusion chromatography of the 21 resultaat polymer showed two peaks, a high molecular 22 weight peak which was the radial or star shaped .
23 polymer comprising 76.3 of the total polymer and a 24 lower molecular weight peak, comprisag 23.7 of the total polymer, ~rhich was the diblock building block 26 before coupling the materials using SiCl4. From the 27 GPC it was estimated that each arm of the radial 28 polymer was composed of a polystyrene block of 15,635 29 molecular weight and 19,264 molecular weight polybut-adiene. The melt flow rate was 28.8 g/10 minutes.

.. ~'~ ..
1 Deaoastratioa 9 X505'--30) To a ~..G liter Tractor ~rera charged :1499 g 3 of cyclohasane and a5m8 g of styrene monomer. The 4 miztura mss heated to G0°C and 7.8 ml of a 0.70 solar solution of sac-butyll.ithium initiator is cyclohexaae 6 xas added. After 41 minutes, the reaction tampers--? tare vas reduced to 58oC and L18.5 grass of isoprene 8 vas added. After 3~ minutes the liviag styrene-9 isopreaa diblock polymer eras coupled to form a lineaz styrene-isoprene-styrene vtiblock polya~ar'by adding II 32 n1 of O.IZ H ~..2'di.brom~aathane in cyclohezane over 12 a period of 1'1 minutes. A hindered phenol aatiozi-I3 dent war added to tba polymer aolutioa which vas they 14 devolati=ad in a vacuum vv an undax nitrogea at 100°C
for 3 hours.
I6 Size ezeluaion chromatography of the resul-17 teat polymer shared two peaks, a high molecular 18 weight peak which °ras the linea~t triblock polymer I9 comprising 86.5 of the total polyaar end a lo~rer molecular ~raight peak, comprising 13.5Z of the total 21 polymer, rhich vas the diblock bui.ldiag block before 22 coupling the chain ands usi.ag O~iE,~, from the GPC it 23 was estimated that the molecular ~raight of the 24 stprene blocks vas I6 ~ E~k~O, aid. ~eh~e molecular of the '5 polyisoprene midblack raa 42,580 The melt floe rate 26 was 50 g/10 minutes.
27 Adhesive compositioas were prepared by coa 28 biasing I00 parts of tt~e bl~acl~ ~:apolymer. 220 parts of r 29 the primary tack.ifyiag resin b2onatac I05L, available r n~
from Arizona Cheni.cal~, 80 parts c~f Tufflo 6056 31 ~a plasticizer oxl availah2t from Lyondell Petroleum d as 32 Oompany). sad 3 parts oaf Irganox ~~10 va stabilizer 33 available from ~iba--Geigy3, to produce a homogeaeona 34 adhesive blend. The adhesive was coated on 2 mil WO 92/20725 ~ ~ , ~ ~ ~ ~ ~ PCT/US92/04334 1 thick Mylar (polyester) backing, to produce a 1.5 mil 2 thick film, of adhesive.
The performance characteristics of the ad-4 hesives of the block copolymers are given in the Table, the adhesive formulations for the 5 (pS-pI-pB)nx and (pS-pI)nX radial block copolymers, 7 or °rubbers" of this invention, designated as 8 Ezamples I through 7, being set out for comparison 9 with adhesive formulations prepared from rubbers not of this invention, i.e.. Demonstrations 8-12.
11 Columas.l and 2 of the Table identifies the specific 12 test run and type of rubber tested. Columns 3-6 13 identifies the MFR, or Melt Flow Rate, the total wt.~
14 styrene content of the rubber, the molecular weight of the polystyrene block eompoaent of a rubber, pS, 16 and the molecular weight of the polyieoprene block 17 eompaaent of a rubber, pI. Columns 7-9 describe the 18 rasults of the tests conducted on each of the i9 adhesive formulations, viz. the adhesive viscosity, ' SAFT, and the holding poser. It is clear that the 21 adhesive compositions of this invention, i.e., 22 Examples 1-7, exhibit superior SAFT (high temperature 23 resistance), and superior holding power (static time 24 to failure).

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oc w:,wwc~:w wcaoo o a - z -1 Continuing refsrence to the Tabls, Examples 2 1 thron'h 7 shoe the-perfar*,aace of adhesiae eonposi-:3 tions prepared trop radial, bloc~r polymers Whose Z
4 styrene, poly*tyrene molecular !eeigbt, and polydieae molecular ~raight are all within the preferred ranges a of the radial. 'bloc; copolymer reqn~.red for the ~' practice of this ia~raanti.on. it is required that all H of these parameters fall within th,w ranges expressed in order tc obtain this superior adhesive perfor-IO mance. Comparat~..va ~zampl.e 8. ahawring the perfor-II mince characteristics of an adhas~.we composition of a I2. radial styrene-butadiene capo:lymer mat of this invsn-13 tion, albeit the copol~rmer has a s~:yrea~e content and 14 melt flow ratt comparable ts~ the radial copolynera of thin invention, is inadequate* ;its ,cheat adhesion :6 failure temperature, SAf"~, is very pour. Styreae-17 isoprene copolymers have ixiherently lopes viscosity 18 thaw styrene-butadiene copoi~ya~ers of the same 19 molecular weight, and 'hence the atyxene-isoprene 2G copolymers are superior, in that xhey can be made with 21 higher molecular Freight pS 'black.s. As a result, the 22 styrene-isoprene ~:.ap~alymers can be produced with 23 greater SAFT. Compa~rax.i~re ~xampl~e 9 shows the per-24 formance characte°~isic:s of an adheai.ve composition made from a 1. ineaar p;a-p~l~-p:~ copolymer as disclosed in 25 U.S. Patent Iota. 5a14'~,95~, sag~:~a. L~em~nstr~~tiuns 27 10. 11 and ~.2 represent adhcsirre compositions 28 prepared from cammereiallp available copolymers 29 having properties wh.ch fall ~autaide thane require-men a which are necaassry t.o ahtaiu superior 'hot-melt 3I adhesivec, i.e., a radial ~pS-°pb3nX bloc3c copolymer r ma 32 as represented by Demonstra.ti.ons 10 ~Rraton D 17.22) , 33 a (pS-p8)n pS Linear multibLack copolymer as rtpre-., F
34 rented by Demon*trati.an-11 ~Stereoa 34 840A), and a linear p5-pI-pS block copolymer era represented by WO 92!20725 ,,.. ~ ~ J ~ ~ ~ ~ PCT/US92/04334 .. , - 31 -1 Demonstration 12 (Europrene SOI. T 193 B). As shown 2 by the Table, the adhesive compositions of Ezamples 1 3 through 7 clearly ezhibit the best combination of low 4 adhesive viscosity, high SAET, and high 35°C Hold.
A prepared adhesive composition uaef.ul for 6 magazine ox book binding can also be formed from the 7 hot-melt adhesive composition of this invention by 8 the further addition to the hot-melt adhesive compo-9 sitioa of from 0 to about 5 percent, preferably from about 0.5 to about 5 percent, based on the weight of 11 the hot-melt adhesive composition, of a hydrocarbon 12 or petroleum derived wan. Ezemplary petroleum 13 derived wanes are, e.g., paraffin. and microcrystal-14 lice wanes having melting points within a range of from about 55°C to about 110°C, as well as low 16 molecular weight~polyethyleae and Eischer-Tropsch 17 wanes .
18 It is apparent that various modifications and 19 chaages eaa be made without departing the spirit and 20~ scope of the invention.
21 Having described the invention, what is claimed 22 is:

Claims (26)

Claims:

1. A radial block copolymer constituted of a polystyrene block segment and a polyisoprene block segment, an end of which is constituted of butadiene, as characterized by the formula:

(pS-pI-pB)n X

where pS is polystyrene, pI is polyisoprene, pB is polybutadiene, X is the residue of a multifunctional coupling agent used in the production of the radial block copolymer, and n is a number greater than 2 representative of the number of branches appended to X, pS A has an average number molecular weight ranging from about 10,000 to about 25,000, pI-pB has an average number molecular weight ranging from about 20,000 to about 70,000, the overall number average molecular weight of the block copolymer ranges from about 90,000 to about 380,000, and wherein the pS component is present in an amount of at least 25 parts to about 50 parts per 100 parts by weight of the radial block copolymer and the weight amount of polyisoprene in the block pI-pB is greater than 50 weight percent.

2. The radial block copolymer of claim 1 wherein the average molecular weight of the pI+pB component ranges from about 20,000 to about 40,000, the average molecular weight of the pS component ranges from about 14,000 to about 20,000, the overall molecular weight of the copolymer ranges from about 100,000 to about 240,000, and wherein the pS component is present in amount ranging from about 27 parts to about 45 parts per 100 parts by weight of the copolymer.

3. A hot melt adhesive composition which comprises from about 15 percent to about 35 percent based on the weight of the hot melt adhesive composition, of the radial block copolymer of claim 1;
from about 45 percent to about 70 percent of a compatible primary tackifying resin, based on the weight of the hot melt adhesive composition;

from 0 percent to about 30 percent of a plasticizing oil or secondary tackifying resin, based on the weight of the hot melt adhesive composition, and from about 0.1 percent to about 2 percent of a stabilizer, based on the weight of the hot melt adhesive composition.

4. The hot melt adhesive composition of claim 3 wherein the hot melt adhesive composition contains from about 20 percent to about 30 percent of the copolymer.

5. The hot melt adhesive composition of claim 3 wherein the hot melt adhesive composition contains from about 50 percent to about 60 percent of the compatible primary tackifying resin.

6. The hot melt adhesive composition of claim 3 wherein the host melt adhesive composition contains from about 5 percent to about 20 percent of the plasticizing oil or secondary tackifying resin.

7. The hot melt adhesive composition of claim 3 wherein the hot melt adhesive composition contains from about 0.5 percent to about 1.5 percent of the stabilizer.

8. The composition of claim 3 wherein the average molecular weight of the pI+pB component of the radial block copolymer ranges from about 20,000 to about 40,000, the average molecular weight of the pS component ranges from about 14,000 to about 20,000, the overall molecular weight of the copolymer ranges from about 100,000 to about 240,000, and wherein the pS component is present in amount ranging from about 27 parts to about 45 parts per 100 parts by weight of the copolymer.

9. The hot melt adhesive composition of claim 3 wherein the hot melt adhesive composition additionally contains up to about 5 percent, based on the weight of the hot melt adhesive composition, of a hydrocarbon wax sufficient to form an adhesive composition useful for lining magazines or books, or for packaging and carton sealing.

10. A disposable article comprising a polyethylene or polypropylene substrate bonded to a tissue, non-woven fabric or absorbent fluff by use of a hot melt adhesive composition which comprises from about 15 percent to about 35 percent, based on the weight of the hot melt adhesive composition, of a radial block copolymer constituted of a polystyrene block segment and a polyisoprene block, an end of which is constituted of butadiene, as characterized by the formula:

(pS-pI-pB)n X

where pS is polystyrene, pI is polyisoprene, pB is polybutadiene, X is the residue of a multifunctional coupling agent used in the production of the radial block copolymer, and n is a number greater than 2 representative of the number of branches appended to X, pS has an average number molecular weight ranging from about 10,000 to about 25,000, (pI-pB) has an average number molecular weight ranging from about 20,000 to about 70, 000, the overall number average molecular weight of the block copolymer ranges from about 90,000 to about 380,000, and wherein the pS component is present in an amount of at least 25 parts to about 50 parts per 100 parts by weight of the radial block copolymer, from about 45 percent to about 70 percent of a compatible primary tackifying resin, based on the weight of the hot melt adhesive composition, from 0 percent to about 30 percent of a plasticizing oil or secondary tackifying resin, based on the weight of the hot melt adhesive composition, and from about 0.1 percent to about 2 percent of a stabilizer, based on the weight of the hot melt adhesive composition.

11. The disposable article according to claim 10 wherein the hot melt adhesive composition contains from about 20 percent to about 30 percent of the radial block copolymer.

12. The disposable article according to claim 10 wherein the hot melt adhesive composition contains from about 50 percent to about 60 percent of the compatible primary tackifying resin.

13. The disposable article according to claim 10 wherein the hot melt adhesive composition contains from about 5 percent to about 20 percent of the plasticizing oil or secondary tackifying resin.

14. The disposable article according to claim 10 wherein the hot melt adhesive composition contains from 0.5 percent to about 1.5 percent of the stabilizer.

15. The disposable article according to claim 10 wherein the average molecular weight of the pI+pB
component of the radial block copolymer ranges from about 20,000 to about 40,000, the average molecular weight of the pS component ranges from about 14,000 to about 20,000, the overall molecular weight of the copolymer ranges from about 100,000 to about 240,000, and wherein the pS component is present in an amount ranging from about 27 parts to about 45 parts per 100 parts by weight of the copolymer.

16. The disposable article according to claim 10 wherein the primary tackifying resin is any compatible resin or mixture thereof selected from the group consisting of (1) natural and modified rosins; (2) glycerol and pentaerythritol esters of natural and modified rosins; (3) copolymers and terpolymers of natured terpenes; (4) polyterpene resins having a softening paint, as determined by ASTM method E28-58T, of from about 80° to 150°C; (5) phenolic modified terprene resins and hydrogenated derivatives thereof; (6) aliphatic petroleum hydrocarbon resins having a Ball and Ring softening point of from about 70° to 135°C; (7) aromatic petroleum hydrocarbon resins, and mixed aromatic and aliphatic paraffin hydrocarbon resins, and the hydrogenated derivatives thereof; (8) aromatic modified alicyclic petroleum hydrocarbon resins and the hydrogenated derivatives thereof; and (9) alicyclic petroleum hydrocarbon resins and the hydrogenated derivatives thereof.

17. The disposable article according to claim 10 wherein the disposable article is selected from the group consisting of diapers, sanitary napkins and bed pads.

18. The disposable article according to claim 10 wherein the adhesive component of the disposable article is applied as a continuous or discontinuous film.

19. The disposable article according to claim 18 wherein the disposable article is of multi-line construction.

20. The disposable article according to claim 19 wherein the adhesive component used in forming the disposable article is applied as fine parallel longitudinal strips, swirl or as a multidot pattern of adhesive droplets.

21. The radial block copolymer of claim 1 wherein n on the average ranges from about 3 to about 7.

22. The radial block copolymer of claim 1 wherein the overall number average molecular weight of the radial block copolymer is between about 100,000 to about 240,000.

23. The radial block copolymer of claim 22 wherein the overall number average molecular weight of the block copolymer is between about 120,000 to about 200,000.

24. The radial block copolymer of claim 1 wherein X is -Si.

25. The radial block copolymer of claim 1 wherein the weight amount of polybutadiene in the block pI-pB is less than 10 weight percent.

26. The radial block copolymer of claim 25 wherein the weight amount of polybutadiene in the block pI-pB is less than 5 weight percent.