CA2002358C - Disposable article construction - Google Patents

Abstract

Composite articles such as disposable diaper are made more efficiently through the use of a single hot melt adhesive composition having sufficient resistance to creep, sufficiently high bond strength, and a viscosity that is controllable through a range permitting it to be used for elastic attachment and in fine line, multi-line extrusion or sprayed adhesive preparation techniques. The adhesive composition in one embodiment comprises (a) 5 to 14 wt-% of a radial block copolymer having a molecular weight of at least 145,000 having the formula:
(A--B)n--Y
wherein Y is a multivalent coupling agent, A comprises a polyvinyl substituted aromatic block, B comprises a polymeric rubbery midblock, and n comprises an integer of at least 3;
(b) about 45 to 85 wt-% of a compatible tackifying agent selected from the group consisting of C5 resin, a styrenated C5 resin, a styrenated terpene resin, a hydrogenated C9 resin, a resin derivative, a styrenated terpene resin and mixtures thereof; and (c) about 5 to 35 wt-% of a plasticizing oil;
wherein the hot melt pressure sensitive adhesive has a static shear at 100°F of at least 30 min., a creep resistance at 100°F of less than about 30% and exhibits a viscosity of less than 25,000 cP at 275°F.

Description

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z Field of the Invention ' ~ ._.y~
The invention relates to a hot melt construction.adhesive and to a disposable compossite article made by adhesively,joining' its components. ThE: invention more particularly relates to a disposable article such as a disposable diaper, an incontinent pad, a bed pad, or a feminine pad, made by adhesively bonding:a layer such as a film, a woven or nonwoven fabric, a tissue or sheet, or an elastic band to a substrate using the novel adhesive of the invention. ~'he adhesive of the invention has superior adhesion and cohesion, unexpected resistance to creep, high construction bondincY strength, heat resistance, and a viscosity profile designed for both elastic attachment and assembly processes including extrusion bonding, fine line construction, multi-line construction or spray application in disposable article technology.
More particularly, the invention relates to disposable diapers that can be constructed using extrusion, spray and multi line techniques to join a layer to a substrate, or to join an elastic band to a substrate using the adhesive of the invention.
Ba.ckctround of the Invention The typical commercially used disposable article adhesive uses a plasticizing oil, ~~ tackifying resin in combination with typically a styrene-butadiene-styrene (S-B-S) or styrene-isoprene-styrene (S--I-S) linear (A-B-A) block or a multi-block (A-B-A-B-A-B) copolymer having a molecular weight less than about 140,000. Such convf~ntional commercial adhesives are typically formulated to contain about 20 wt-% S-I-S or S-B-S, A-B-A block copolymer, preferably 25 to 35 wt-% with 40 to 60 wt-o tackifier and 25 to 35 wt-% oil. Amounts of A-B-A block copolymer ranging from 20-35 wt- o of the adhesive are required to maintain cohesive strength and adhesion and to enhance the creep resistance properties in linear A-B-A block copolymer systems when used in the elastic attachmESnt mode . The use of this amount of A-B-A
rubber in these forrnulas result in high costs when compared to other adhesive systems. Additionally, such an adhesive with a high polymer content: can result in a product viscosity that is in excess of the maximum viscosity used in the multi-line article construction. Such an adhesive with a lower polymer level (i.er.~
about 20 wt-%) that has a viscosity in the multi-line article construction range can lose cohesive strength, adhesion or creep resistance and can often :Fail in the elastic attachment mode.
Disposable articles and their manufacture from construction materials including woven and nonwoven fabrics, films and adhesives are described in a variety of U.S. patents. Buell, U.S. Pat. No. 3,860,003, 4Voon et al, U.S. Pat. No. 4,050,462, Strickland et al, U.S. Pat.. No. 4,253,461, and Ryan et al, U.S.
Pat. No. 4,326,528 teach disposable diaper construction. Such diapers typically cc>mprise a fluid impervious backing sheet and absorbent materials appliE_d to the backing sheet. Such diapers typically also comprise an elastic band attached to the portion of the diaper forming the leg opening. The absorbent material and the elastic band; are attached to the poly impervious backing sheet with hot melt adhes_Lves.
Puletti et al, U.S. Pat. No. 4,419,494 teaches the use of S-B-S linear A-B-A ~~lock copolymers in conjunction with a fatty acid polyamide in heat resistant hot melt adhesives for use in the elastic attachment mode. Roeder, U.S. Pat. No. 3,672,371, Allison, U.S. Pat. rdo. 4, 531,945, and VanTilberg, U.S. Pat. No.
4,687,478 teach various a:~pects of sanitary absorbent articles.
Such articles typically comprise a fluid impervious back sheet with an absorbent la~~er attached thereto. Such absorbent articles can have a pervious top sheet over the absorbent layer and also can be fully wrapped by a pervious outer wrap . Such constructions are made using hot melt adhesives. Marsan et al, U.S. Pat. No.
4,392,862, Buell, U.S. Pat. No. 4,396,645 and Lindman et al, U. S . Pat . No . 4 , 681, 793 tE:ach a variety of absorbent devices and their materials and methods of construction. Collins et al, U.S.
Pat. No. 4,136,699 teaches an A-B-A block copolymer based construction and positioning adhesive for absorbent articles.
Schmidt, Jr. et: al, i:J.S. Pat. No. 4,526,577 is primarily directed to the use of si~yrene-butadiene-styrene linear A-B-A

block and linear A-B-A-B-A-B multi-block copolymers in hot melt adhesives in the man~.~facture of disposable laminates using multi-line extrusion adhesive application technology. Schmidt, Jr. et al teach that hot melt adhesives have found a wide range of uses-, however while a pari~icular hot melt adhesive may have adequate bonding in a particular use, it may be completely unsuitable for other uses or applications . Of the many various hot melt adhesive compositions that h~~ve been proposed for use in construction of disposable articles, the use of a particular hot melt adhesive is dependent on its;properties, particularly its ability to bond to polyethylene on pol~rpropylene films, tissue, absorbent materials, and elastic banding.
The primary focus of the Schmidt patent is directed to bonding laminates with linear A-B-A and linear multi-block A-B-A
B-A-B block copolymers which are specifically disclosed arid claimed in the patent. Schmidt does not appear to teach elastic band attachment. Only the multi-block A-B-A-B-A-B polymer based adhesives are exemp7_ified in the patent. The patent discloses but does not claim radial or teleblock block copolymers and fails to disclose any aspect of such polymers including molecular weight, percent styrene, percent midblock, percent di-block, molecular weight distribution, or other polymer indicia relevant to adhesive properties and formulation. Further, Schmidt teaches that the adhesive materia:L should contain 15 to 35 wt-% of the preferred linear or p,-B-A-B-A-B multi-block copolymer and prefers and exemplifies adhesive; containing 20 wt-% or more of the multi-block copolymer. Additionally, the Schmidt patent prefers relatively high concentrations of styrene, i.e. at levels of at least 35 wt-% or as much as 43 wt- o styrene in the most preferred A-B-A-B-A-B multi-block copolymer.
The typical S-F;-B-S, S-B-S block copolymers identified by the Schmidt et al patent f:or the adhesives include linear A-B-A
block copolymers which range in molecular weight from about 50,000 to about 140,000. The most preferred adhesives contain STEREON 840A, a mult:i-block A-B-A-B-A-B block copolymer having 35 wt-%, or greater, styrene and a molecular weight of about 70,000.

In conventional production of such composite disposable articles, hot melt adhesives are typically extruded at elevated temperatures (about 250-.350° F.) directly onto a work piece, typically a polyethylene o:r polypropylene film. Additional layers' such as a nonwoven fabric, an absorbent material, or a film can be adhered to the poly film substrate using the hot melt adhesive. Spray adhesives technology has been studied and has attracted increasing attention in recent years. However, the predominant application technique mode in production remains the extruded fine line, multi~-dot or multi-line methods.
In adhesive construction of disposable articles a variety of materials are bonded ,under a wide range of conditions. To optimize performancE: separate adhesives have evolved for use in the manufacture of premium quality disposable articles. This is particularly true in elastic attachment and in laminate construction. For the most. part multi-line construction requires an adhesive with controllable, relatively low viscosity and sufficient bonding strength to maintain the mechanical integrity of the laminate com~~osite article comprising a substrate and an absorbent layer. In sharp contrast to bond elastic materials to substrates, a different adhesive is currently used that primarily exhibits high creep resistance to ensure that the elastic, when under stress, does not move relative to the surface of the substrate or become partially or fully detached.
Should the elastic move or become detached, for example in a disposable diaper, the resulting loss of fit could result in inconvenience, waste, embarrassment, discomfort, and associated health and safety problems.
The use of separate adhesives for fine line and for elastic attachment purposes, each having different formulas and properties, increases disposable article manufacturing complexity and can reduce productivity. Additionally, if multiple adhesives are required inventory and storage problems are increased. If the incorrect adhesive is used in the elastic banding it can lead to bond failure. Also, the multi-line extruder nozzle can become plugged. Such problems can lead to inferior products, lost production or both. While some disposable diapers are manufactured with a single adhesive for both multi-line construction and elastic attachment, those diapers are not premium diapers in that they often do not have premium mechanical integrity and can exhibit elastic creep, or detachment.
Accordingly a substantial need exists for a single adhesive having properties rendering the adhesive applicable to both multi-line construction and elastic bonding applications, which requires a significant advancement in providing improved bond strength, creep resistance and low application viscosity in a single adhesive.
Summary of the Invention In accordance with the invention there is provided a A' - 5a -disposable diaper comprising (i) a polymeric film substrate, (ii) at least one absorbent layer, and (iii) an elastic band, wherein the absorbent layer and the elastic band are independently bonded to the substrate with a hot melt adhesive composition. The adhesive comprises about 5 to 14 wt-% of a radial block copolymer having a molecular weight of at least about 185,000, having the formula:
(AB) nl-Y-(B) n2 wherein Y is a multivalent coupling agent, A comprises a polyvinyl substituted aromatic block, B comprises a polybutadiene rubber midblock, n1 is an inter of 3 to 10 and n2 is an integer of at least 0 to 10. The adhesive further comprises about 45 to 85 wt-% of a compatible tackifying resin selected from the group consisting of a C5 resin, a styrenated C5 resin, a styrenated terpene resin, a hydrogenated C9 ,.es;n~ a rosin derivative, a styrenated terpene resin and mixtures thereof and about 5 to 25 wt-% of a plasticizing oil.
Also in accordance with the invention there is provided a disposable diaper comprising (i) a polyethylene or polypropylene film substrate, (ii) at least one absorbent layer comprising a tissue wrapped fluff and (iii) an elastic band, wherein the absorbent layer and the elastic band are independently bonded to the film substrate with a hot melt pressure sensitive adhesive composition. The adhesive comprises about 5 to 14 wt-% of a radial block copolymer having a molecular weight of at least about 185,000 to 240,000 having the formula:
CAB) ~ Y
wherein Y is a multivalent coupling agent, A comprises a rA:

- 5b -polyvinyl substituted aromatic block, B comprises a polymeric rubbery midblock and n comprises an integer of at least 3; about 0.1 to 10 wt-% of a linear A-B-A block copolymer wherein A is a polystyrene block and B is a polyisoprene or polybutadiene block:
about 40 to 80 wt-% of a compatible tackifying resin selected from the group consisting of a C5 resin, a styrenated C5 resin, a styrenated terpene resin, a hydrogenated C9 resin, a rosin derivative and mixtures thereof; and about 5 to 35 wt-% of a plasticizing oil.
Further in accordance with the invention a disposable article comprises (i) a substrate, and (ii) at least one absorbent layer, wherein the absorbent layer is bonded to the substrate with a hot melt pressure sensitive adhesive composition. The adhesive comprises about 5 to 14 wt-% of a radial block copolymer having a molecular weight of at least 145,000, having the formula:
(A-B)~ Y
wherein Y is a multivalent coupling agent, A comprises a polyvinyl substituted aromatic block, B comprises a polymeric rubbery midblock, and n comprises an integer of at least 3 ; about 45 to 85 wt-% of a compatible tackifying resin selected from the group consisting of a C5 resin, a styrenated C5 resin, a styrenated terpene resin, a hydrogenated C9 resin, a rosin derivative, a styrenated terpene resin and mixtures thereof; and about 5 to 35 wt-% of a plasticizing oil. ,The adhesive has a static shear at 100°F of at least 30 min. , a creep resistance at 100°F of less than about 30% and exhibits a viscosity of less than 25,000 cP at 275°F.

-5~- 2002358 Additionally, the invention provides a hot melt pressure sensitive adhesive composition for the multi-line construction of disposable articles which consists essentially of about 5 to 14 wt-% of a radial block copolymer having a molecular weight of about 185,000 to 240,000 having the formula:
(A-B)~ Y
wherein Y is a multivalent coupling agent, A comprises a polystyrene block, B comprises a polymeric butadiene midblock and n comprises an integer of about 3 to 5; about 0.1 to 10 wt-% of a linear A-B-A block copolymer wherein A is polystyrene blend and B comprises polybutadiene block or polyisoprene block; about 40 to 80 wt-% of a compatible tackifying agent selected from the group consisting of a C5 resin, a styrenated C5 resin, a styrenated terpene resin, a hydrogenated C9 resin, a rosin derivative, a styrenated terpene resin and mixtures thereof; and about 5 to 35 wt-% of a plasticizing oil. The adhesive has a static shear of at least about 30 min. at 100°F, a creep resistance of at least about 30% at 100° and exhibits a viscosity of less than 15,000 cP at 275°F.
Brief Discussion of the Invention We have found that surprisingly low levels of a radial block copolymer having a molecular weight of greater than about 140,000 preferably greater than 160,000, can be used to obtain a high level of creep resistance, bond strength, and a low viscosity profile, in a multiple-purpose construction and elastic attachment adhesive. The adhesive exhibits properties qualifying the adhesive for both a elastic band attachment and construction applications using multi-line or other disposable article construction techniques.
The radial block copolymer can be blended in amounts that are surprisingly small in comparison to the prior art adhesives~.,~
as represented by S~~hmidt, Jr. et al, U.S. Pat. No. 4,526,577, with appropriate tackifying resins and plasticizing oils. The radial block copol,~mers of the invention can optionally be combined with linear A~-B-A (both S-I-S and S-B-S) block copolymers to produce an adhesive having superior adhesion and cohesion, high bond strength, resistance to creep and resistance to peel when compared to the prior art including the Schmidt patent. The adhesive can have a viscosity profile at application temperatures which typically range from 250-350° F. useful in both multi-line construction of laminate pieces to polyolefin films and in attachment of elastic to a film.
Radial (or tele:block) copolymers having a molecular weight in excess of about 140,000 are known as shown in the Shell brochure for KRATOIJ* 11E34. An inspection of the brochure indicates that the material is primarily used as a flexibilizing agent for bituminous compositions such as asphalt. The brochure does not indicate that the materials are suitable for use as an adhesive composition or any other adhesive related use.
A different ty3~e of adhesive is disclosed in Doss et al, U.S. Pat. No. 3,993,613 which teaches an adhesive composition comprising about 10 parts by weight of a rubbery radial teleblock copolymer and a blended tackifier made by mixing a polyterpene, a polyvinyl aromatic o:r other tackifying resins with a polyalkylene tackifying copolymer. Additionally, Taylor et al, U.S. Pat. No. 4,212,910 teaches a PET bottle base adhesive having 20-40 wt-% low molecular weight radial block polymer, 30-59% tackifier and 2C-40% wax or oil.
The radial or teleblock copolymers having a molecular weight above 140,000 present significant difficulties in adhesive preparation to manufacturing personnel. While laboratory blending apparatus can be used to manufacture adhesives in small laboratory scale amounts f=rom such radial block copolymers, *Trademark _7_ typical single stage hot melt manufacturing or plant blending techniques, utilized in preparation of prior art adhesives made of typical A-B-A b_Lock copolymers and A-B-A-B-A-B multi-block copolymers as represented by Schmidt, Jr., U.S. Pat. No...~
4, 256, 577, fail to a.dequat:ely blend high molecular weight radial block copolymers wL_th tackifiers or plasticizers into useful adhesive compositions.
Further, the high molecular weight of the radial block copolymers when used. at a concentration found in typical adhesive formulations (about 20 wt-% and more) results in a viscosity that exceeds production specifications or machine application specifications in typical extrusion, multi-line or fine line construction or ela:~tic attachment methods.
We have found techniques for use with radial or teleblock polymers in hot melt adhesive preparations that permit the rapid and effective preparation of the unique adhesive of the invention. These techniques involve a dual stage or multi-stage process in which a preblend of the high molecular weight radial block copolymers with a lower molecular weight adhesive component such as either a ta~~kifier, a plasticizer or mixtures thereof, is prepared. The preblend. can then be combined with the balance of the adhesive components to form a useful hot melt adhesive composition through a complete intimate blending of the components. We have: also found that the adhesive compositions, manufactured with these techniques, have significantly reduced processing time.
The adhesives of this invention can maintain a "T" peel strength of about 100 to 1'75 gms. at 77° F. (25° C.), S.A.F.T.
of about 160 to 190° F.., a creep resistance of elastic attachment of about 5 to 30% at: 100° F. (38° C.) , and exhibit a viscosity of less than about 25, 000 centipoise (cP) at 275° F. The articles made with the adhesive are storage stable at 140° F. with little or no delamination a.nd exhibit substrate failure in the dynamic peel adhesion mode.
The radial block copolymers useful in manufacturing the adhesives of the invention have a molecular weight of about 145,000 and have the: general formula:

_g_ (A-B) nl'Y- (B) n2 wherein A is a glassy block of a polymerized vinyl substituted aromatic monomer, B is a saturated or unsaturated rubbery block of a polymerized dime having 4-12 carbon atoms, Y is a polyfunctional coupling agent residue, nl is an integer of at least 3, preferably 3 to .LO, most preferably 3 to 5 and nz is an integer of 0 to 10, most preferably 0 to 4. The end A or mid'B
blocks can be homo or copolymers of related monomers. Further, at the transition between the blocks some random copolymerization of the A monomers with B 'monomers can exist.
The preferred rubber~~ are radial block copolymers having the general formulae A - B - i . (B - A)n , B
A
wherein n is 1-3, tree A block comprises styrene and the B block comprises butadiene, isoprene, or mixtures thereof which can be hydrogenated. The preferred radial block copolymers contain preferably 15 to 45 wt-°., most preferably 25 to 35 wt-% of styrene. The average molecular weight of the preferred rubbery block copolymers is at least about 140,000. Most preferably the molecular weight of the block copolymers used in the adhesives of this invention i;~ greater than about 160,000. Currently no radial block copolymer has'. a molecular weight greater than about 275,000. However w~~ believe increased molecular weights would be beneficial to the: adhe:~ives of the invention.
The polyfunctional coupling agents (Y) are well known coupling agents for use in the manufacture of the radial block copolymers of the invention. Such coupling agents and the preparations of the rubbery copolymers useful in the adhesive compositions of the: invention are described in detail in a variety of patents including U.S. Pat. No. 3,639,521 and others.
A-B-A block co~~olymers can be used with the radial block polymers. The A blocks of such A-B-A block copolymer comprise blocks of polymerized vinyl substituted aromatic monomers and the B blocks comprise polymerized dimes having 4-12 carbon atoms.
Preferably the A-B-A block copolymers are made of A blocks comprising polymerized styrene and B blocks comprising polymerized butadiene, isoprene or mixtures thereof. Such copolymers typically have a molecular weight in the range of about 70,000-140,00() and :have from about 12 to 35 wt-% styrene.
Such linear and mult:i-blo~~k copolymers are available from Shell Chemical Company, Enichem, Fina and Firestone.
We have found that the adhesive's excellent construction and elastic attachment properties can be improved by stabilizing the oil component of the: adhe:~ive. We believe that the migration of oil from the adhesive mase> to the bond line between the adhesive and a polyolefin film can cause failure of the adhesive bonds.
Stabilizing the oil .in the adhesive preventing its migration from the adhesive composition can increase bond strength. We have found that the bond strength can be improved using at least two mechanisms. First a gelling agent can be used which forms an adhesive contained oil gel. The gel effectively locks the oil in place within the adhesive mass, preventing its migration.
Additionally', highly oil compatible tackifying agents can be used which through compat:ibilii~y tend to prevent migration.
Tackifyinct Resin The adhesives of the invention contain a tackifying resin in combination with a t-hermoplastic block copolymer and a plasticizer. Tacki:Eying resins useful in the adhesives of the invention comprise rosin derivatives including wood rosin, tall oil, tall oil derivatives, rosin ester resins, natural and synthetic terpenes and aliphatic or mixed aliphatic-aromatic tackifying resins.
Aromatic monomers useful in forming the aliphatic aromatic resin compositions ~~f thi.s invention can be prepared from any monomer containing substantial aromatic qualities and a polycnerizable unsaturated group. Typical examples of such aromatic monomers include the styrenic monomers, styrene, alphamethyl styrene, vinyl toluene, methoxy styrene, tertiary butyl styrene, chlc>rostyrene, etc., indene monomers including indene, methyl inder.~e and others . Aliphatic monomers are typical natural and synthetic terpenes which contain CS and C6 cyclohexyh or cyclopentyl satu:rated groups that can additionally contain a variety of substantial aromatic ring substituents. Aliphatic tackifying resins can be made by polymerizing a feed stream containing sufficient aliphatic monomers such that the resulting resin exhibits aliphatic characteristics . Such feed streams can contain other aliphatic unsaturated monomers such as 1,3-butadiene, cis-1,3-:pentadiene, trans-1,3-pentadiene, 2-methyl-1,3-butadiene, 2-met:hyl-2-butene, cyclopentadiene, dicyclopentadiene, t:erpene monomers and others. Mixed aliphatic aromatic resins c~~ntain sufficient aromatic monomers and sufficient aliphatic monomers and optionally other C3~C8 unsaturated monomer; to produce a resin having both aliphatic and aromatic character. The article by Davis, The Chemistry of C5~
Resins, discusses s~rnthet:ic CS resin technology.
The adhesive compositions of the invention can contain rosin and rosin derivatives as a tackifying agent. Rosin is a solid material that occur; naturally in the oleo rosin of pine trees and typically is derived from the oleo resinous exudate of the living tree, from aged stumps and from tall oil produced as a by product of kraft paper manufacture. After it is obtained rosin can be treated by hydrogenation, dehydrogenation, polymerization, esterification, and other post treatment processes. Rosin is typically classed aa; a gum rosin, a wood rosin, or as a tall oil rosin which indicate its source. The materials can be used unmodified, in the form of esters of polyhydric alcohols, and can be polymerized though the inherent unsaturation of the molecules. Materials are commercially available and can be blended into the adhesive compositions using standard blending techniques. RepresESntative examples of such rosin derivatives include pentaerythritol esters of tall oil, gum rosin, wood rosin, or mixtures t:hereo:E.
Representative examples of such aliphatic resins include hydrogenated synthfstic C9 resins, synthetic branched and unbranched C5 resins and mixtures thereof. Representative examples of such aromatic: tackifying resins include styrenated terpene resins, styrenated CS resins or mixtures thereof. The selection of tackifying resins is often based on the nature of the B or midblock r<~dial lblock copolymer. Rosin derivatives are best for S-I-S/S-B-:3 blends and can be used with either S-I-S or S-B-S alone. Hydrog~enateci C9 or straight aliphatic resins are preferred for S-I-S ~~opolymers. For S-B-S copolymers, styrenated terpenes or rosin e:~ters .are preferred.
P1<~sticizing oils Plasticizing oils are used in the construction/elastic attachment adhesive: of the invention. Such oils are primarily hydrocarbon oils lo'N in aromatic content. Preferably the oils are paraffinic or napht:henic in character. The oils are preferably low in volatility, are clear and have as little color and odor as possible. The use of a plasticizing oil of this invention also contemplates the use of olefin oligomers, low molecular weight polymers., vegetable oils and their derivatives and similar plasticizing :Liquids.
Oil Gelling or Complexing Agents Plasticizing oils used in adhesive compositions can be prevented from migration by the use of gelling or complexing agents which tend to re:~train the migration of oil through formations of gels or complexes. The oil can be restrained by a variety of gelling agents including waxes, polyethylene waxes, oxidized waxes, oxidized polyethylene waxes, polyvalent metal soaps, etc.
The following gable nets forth the useful, preferred, and most preferred formulas.

Table 1 Most Inaredient Useful Preferred Preferred Radial block copol~ymer* 5-14 7-13 8-12 A-B-A block copolymer* 0-14 0-12 0-10 Tackifier 45-85 50-80 55-75 Plasticizing oil 5-35 6-30 8-20 Synthetic polyethy:Lene 0-10 0.1-9 0.25-5 wax (or other oi:L

complexing agent) * Total polymer content (including both radial block and linear block polymer) is atypically about 15 wt-% or less of the adhesive.
In sharp contrast to prior art single stage blending procedures for the manufacture of pressure sensitive hot melt disposable article construction adhesives which are represented by Schmidt, Jr. et <~1, U.S. Pat. No. 4,526,577, we have found that effective commercial manufacture of the hot melt adhesives of this invention using high molecular weight radial block copolymers involves a two--step manufacturing procedure. In the first step the radial block copolymer is mixed at elevated temperature with at least one additional adhesive component such as a tackifier, plasticizers, or mixtures thereof to form a preblend or a premix wherein the block copolymer is intimately mixed with the other adhe:~ive ingredient. The preblend is then blended with the x-emaining adhesive components at elevated temperature in standard commercial blending equipment.
In somewhat greater detail, from about 0.5 part of resin to about 2.5 parts of resin can be blended per part of radial block copolymer in order i.o form the preblend of the invention. The preblends can be prepared in conventional thermoplastic polymer processing equipment capable of providing sufficiently high shear to intimately blend the high molecular weight polymers and the low molecular weight adhesive components such as tackifying resins, oils or other low molecular weight polymeric materials or blends thereof . Exampl.es of such equipment are single or twin screw extruders, intensive internal mixers, Mixtruders, Sigma Blade mixers and the like, which are heated to a sufficient=
processing temperature, typically between 250-350° F. If a batch .
mixer is used the polymer is blended with the adhesive component such as resin, oil or component blends thereof, typically at an amount less than or equal to the polymer to provide a homogeneous preblend. Thereafter the remaining ingredients can be added and mixed until homogeneous.
The equipment a.nd processes useful in the manufacture of the preblend materials of the invention is described in the following articles. The article "Machinery and Equipment" of Plastics Compounding Redbook of 19~g7 88, is a compilation of information regarding compounding and size reduction equipment including lab and production scale blending apparatus. The articles "Liquid Resin Injection System for Continuous Mixing of HMPSA" and "Extruder Performance Over Broad Melt Index Ranges" discuss blending materials having different viscosity profiles.
The article "Advance in Production and Coating Technology for Hot Melt Pressure Sensitive Adhesives - Multiruder System"
discusses the mult_Lruder system of premixer, multiruder and coater and is used f:or continuous production and coating of hot melt pressure sensitive adhesives for labels and tapes.
The article "Continuous Compounding of Hot Melt Adhesives"
discusses continuously operating blending systems capable of blending hot melt adhesives with reduced heat history. Such compounding systems involve extrusion processing.
The article "Technical Aspects for Extrusion Compounding of Hot Melt Adhesives" discu;~ses continuous processing systems for the manufacture of hot rnelt and pressure sensitive adhesive formulations using batch and twin screw manufacturing methods.
The article "'twin ;3crew Extruder Process of Adhesive"
discusses continuous processing hot melt adhesive compounding with block polymer formulations using multi-stage feeding of oil resins, additives and base polymer.
The article "C~~ntinuous Production of Hot Melt Adhesives Aspects of Quality and Costing" discusses basic processing possibilities for ~~roduc:Lng hot melts continuously involving working from a premix and deals with four basic continuous processes. The disclosure involves multi-stage addition.., pelletizing, coating, etc. Equipment for such manufacture is shown in the brochures of Welding Engineers, Inc., Eagan Manufacturing Company, Buss-Kneader, Warner and Pfleiderer, Conair and Black Cl;~usen.
We have found t:hat for ease of handling the preblend of the invention can be dividi.ed into pieces sized for further processing. We have found that the preblend can be pelletized using a strand, waterface or underwater pelletizer (such as those made by Black Clause:n). P,n underwater pelletizing system can be used in which a waf=er stream removes the cut pellet from the cutting area and directs t:he water-pellet stream to a centrifugal device that separates the: water from the pellet and dries the pellets to a useful format.
The handling properi=ies of the preblend pellets can be improved by treating the surface of the pellets with a nontacky organic or inorganic coating. Such coatings can comprise aqueous dispersions of water insoluble waxes, fatty acid esters, and other known anti-blocking agents. Useful inorganic anti-blocking agents can include such materials as silica, talc, gypsum, calcium oxide, magnesium oxide, etc. One mode of adding the antiblocking agent to the adhesive pellets is in the circulating water in the pel:Letizing machine. An addition of the antiblocking agent t:o the water inherently coats the pellets as they are formed at t:he cutting head with the antiblocking agent which remains after- the pellet is separated from the water solution and dried.
The hot melt adhesive, of the invention can be manufactured by pillow pelletizing, a procedure such as that disclosed in Franke, U.S. Pat. No:~. 3, 723, 035 and 4, 054, 632. The pillow-shaped pellets can be coatE~d with a nonblocking thermoplastic coating agent. Such coating agents are known, for example EPOLENE C-10 from Eastman Chemical or AC-400 from Allied Chemical, or blends of compatible polymers and additives to control coating viscosity as required to obtain a uniform protective coat. Additionally, the preblend can be extruded in multiple ribbons onto a cooled stainless belt precoated with a compatible thermoplastic coating.
Composite Construction Broadly, disposable composite articles such as disposable diapers, feminine protection articles, incontinent pads, bed pads and others are typically made by joining to a substrate, typically a plastic or polyolefin film substrate, an absorbent layer frequently covered by a tissue and a woven or nonwoven overlayer. Elastic; banding materials can also be adhesively attached to the plastic film layer between the film and the woven or nonwoven over-layer in articles requiring a close fit around the leg or waist.
Plastic substrates u;~eful in the articles of the invention comprise films made from polyethylene, polypropylene, polyester such as polyethy_Lene terephthalate, polyvinyl chloride, polyvinylidine chloride, polyvinyl acetate, and other materials capable of film formation.. The tissue layer is a well known, typically loosely formed cellulosic sheet of high porosity or permeability.
The woven or nonwoven layers can consist of a fluid permeable flexible material that can be made of either hydrodhilic or hydrophobic fiber components. The woven and nonwoven webs comprising the fabric can comprise natural or synthetic fibers or mixtures thereof. Woven and nonwoven materials are well known and their construction methods have been practiced for man~,r years. Woven fabrics are typically manufactured in weaving machines forming an interlocking mesh of fibers forming the layer. Nonwoven fabrics can be made through a dry laid or wet :Laid method in carding processes, air laid processes, or spun bond processes to produce a web that is mechanically, chemically or thermally formed. The fabric layers for use in the composite articles of the invention typically have a basis weight in t:he range of about 10 to 25, preferably 14 to 18 grams per square yard, a minimum dry tensile of at least 800 grams per centimeter squ<~red in the machine direction, and at least 200 grams per centimeter squared in the cross machine direction.
Synthetic materials commonly used in forming the woven or nonwoven fabric layE~rs in~~lude rayon, polyester, polypropylene, polyethylene, nylon and others.
Absorbent layers bonded into the disposable articles of the invention by the adhesive of the invention comprise typically cellulosic pulp or i_luff, super-absorbent batts or combinations of fluff and super-.absorbent materials. Such fluff layers are often formed and wrapped in tissue to provide mechanical integrity to the fluff which has little inherent mechanical strength. Fluff is typically manufactured through the formation of finely divided cellulo~:ic fibers, however other materials can be used to form highly absorbent, fluff or pulp layers.
Elastics or fi:Laments, threads or ribbons of an elastomer or elastic polymer material can be used in the manufacture of the disposable articles. of the invention. Such elastomers are polymeric substance: with molecular memory. Such materials when placed under stress elongate, but when the stress is relieved, return to their original dimensions. Elastomeric polymers are typically mono or copolymers of moderate molecular weight. Known elastomeric materials include styrene-butadiene copolymers, natural rubbers, isobutylene-isoprene copolymers, polychloroprene systems (NEOPRENE, duPont), polyurethanes, polysulfide rubbers, polyacrylate elastomers comprising the copolymerization of ethyl acrylate and acry:Lic acid-lower alkanol esters, silicone elastomers, fluoro e:Lastomers, ethylene-propylene elastomers, and mixtures thereof . Such elastomers can be crosslinked to increase strength and elastic: properties .
In the continuous manufacture of the disposable articles of this invention and particularly disposable diapers, a small amount of adhesive :in the mufti-line, mufti-dot, fine line, or random pattern is applied by extrusion, wheel or spray application to a th_Ln plastic film substrate. The application occurs at a temperat=ure o:f about 250-325° F. and the adhesive is applied at a rate of about 0.1 to 2 mg/lineal inch. The absorbent materials forming t:he absorbing inner liner of the disposable article is applied. to i~he multi-line adhesive on the film substrate.
In somewhat greater detail, disposable diapers are made in a continuous proces~c by adhering the components of the disposable diaper to a continuous polyethylene or polypropylene film sheet from which the diaper is c:ut after the individual components are adhered. Typically the components are added in stages including an addition of an elastic', an addition of the absorbent layer, and the optional addition of a waist shield.
In such a technique) thin lines of adhesive are extruded onto the material at a rate of about 0.1 to 2 milligrams per lineal inch of adhesive and the absorbent layers are bonded to the fine lines of adhesive. Such application can be in the form of multi-lines, mufti-dots, or other adhesive pattern that can be effectively formed on the poly surface of the film for construction purposes. The absorbent layer is laid down on a continuous web of the poly film.
Elastic bands can be applied to the film layer prior to the absorbent layer or ~~an be applied to the absorbent layer after the layer is bound to the film or the band can be adhesively applied to the outer surface of the film. Elastics are typically applied in a manner such that the elastics provide constriction or stretchable beha~;rior to the edge of the disposable article.
Such constricting or ela:~tic behavior provides the disposable article with the propert~~ that the disposable article fits or seals itself to the underlying wearer's body surface, generally the leg or the waist . Such constricting or stretchable properties are obtained in one of two ways . The elastic is stretched and adhered to the underlying film. As the stretch on the elastic is released the underlying substrate is gathered. Alternatively, the film substrate can be gathered and unstretched elastic material can be adhesively attached to the peaks of the fluted or gathered film. In this process the elastic needs no stretching since the gathers are preforme:d.

Elastic attachment i:~ commonly achieved by applying adhesive to the elastic or sprayed over an elastic/poly or elastic/nonwoven composite. The elastic with the adhesive can be applied to the surfaces of either the poly sheet or nonwoven sheet. The adhesive can be extruded or applied in a spray, in a spiral pattern, i.n an intermittent pattern or other format .
The entire length of: the elastic in contact with the poly can be adhered. Alternati~rely, t;he portion of elastic within about 2'-3 inches from the waist band can remain unadhered to the poly layer. The continuous bonded composite article containing poly, absorbent layer and elastic 1S then cut to form leg openings and to divide the continuous web into individual diapers. Preferably the leg openings are cut. with a water jet spray, while the individual diapers <~re cut with a rotary knife.
Optionally, a waste barrier can be formed in the diaper waist area by adher:Lng a polyethylene film layer over the fluff or absorbent layer at the cut forming the waist band. The adhesive is typically applied at the bond between the poly waste shield and the poly backing, forming an overlapping layer that prevents wicking from the absorbent layer past the waist band to the exterior of the diaper .
Test Procedures The following test procedures were used to test the Examples that follow the proc:edure:~.
A. Creep Resistance of Elastic Attachment and Mult:ipuripose Adhesives This test is used t.o evaluate an adhesive's ability to withstand the stress imparted on the glue line by the elastic when held in an elongated': state at the use temperature of the disposable article.
Materials and E<~uipment:
1. Multibead applicator similar to Meltex CT-225 having adjustable temperature, web speed, application rate, elastic at:tachmfsnt tensioning device and nip pressure.
2. Oven capable of maintaining 37° C. (100° F.) for 4 hours.
3. 3/4" plywood, 12" wide and 12" long.
4. 300 mm ru:Ler.
5. Natural rubber elastic.
6. Polyethyle=ne film.

7. Stapler.
Procedure:
Remove operato=r side nozzle from the multibead applicator and adjust the elast=ic attachment tensioning device such that the elastic passes under but does not touch this orifice. Adjust the tensioning device so that the elastic will be laminated to the polyethylene film at: 100% stretch. , Preferred Meltex Settings:
Temperature 150° C. (300° F.) Nip Pressure 4.0 bar (60 psi.) Application Rate 7.0 mg/inch Rewind and Unwind Tension As low as possible Web Speed 45 ~ 5 meter/min.
Use the following equation to determine either flow rate or web speed:
Web Speed (M/min.) - Flow Rate (g/min.) (0.007 g/in.) 39.4 in/M) Run several meters o:E good application at 7.0 mg/in. coat weight.
Allow the elastic/polyethylene laminate to contract and equilibrate at 25° C'. ovex-night prior to testing.
Sample Preparat=ion for Creep Testing at 37° C.:
A. Using the 300 mm ruler, mark a line 290 mm from the end of the 12" x 12" x 3/4" p7_ywood. Mark another line 300 mm from the same end.
B. Peel the elastic' away from one end of the polyethylene enough to facilitate' stapling through the poly into the end of the plywood. Stretch the laminate until the polyethylene is ungathered but not stretched. Mark the elastic at the 300 mm line. Allow the laminate to contract until the mark on the elastic is over t:he 290 mm line and staple through the polyethylene to secure th.e other end of the laminate. You now have a laminate that is fixed at 97% of full extension of the elastic.
C. Peel the Eslastic back from the poly at one end of the edge of the plywood board. Peel the other end to the 290 mm line .
D. Prepare 5 specimens per adhesive tested.
Test Procedure:
A. Preheat oven to 37° C. Prepare test specimens per above instructions.
B . Place plyv~ood with attached test specimens in oven and note the time.
C. After 4 hours remove plywood and measure the length of elastic that is sti:Ll glued down to the polyethylene. , Use the followLLng eq,aation to calculate the % creep;.
Original length Length after Creep = 290 mm - 4 hours X 100 Original length (290 mm) B. Dynamic Pee:L and Static Shear Tests For Multibead Adhesives Scope:
Static Shear:
This test is <~n indication of an adhesive's ability to withstand bond fail,are under a constant load at a temperature approximating the u:~e temperature of a disposable article.
~rnamic Peel:
This test is u;~ed to determine the bonding strength of an adhesive when subjected to a dynamic. peel force.
Materials and E;guipment:
1. Multibead applicator similar to Meltex CT-225 having adjustable>. temperature, web speed, application rate and nip pressure.
2. Suitable f=orce measuring device (i.e., Instron or I-Mass) .
3. Programmable oven capable of maintaining 37° C.

(100°F.) :for 8 hours and registering failure times.
4. 50 gram mass equipped with mechanical means of attaching to samples.
5. Release p;~per cut into 2" x 8" strips.
6. Nonwoven :fabric and polyethylene film.
Procedure:
Adjust multibe<~d applicator to proper settings. Preferred settings are shown below. Adjustments can be made based on the type of adhesive or application. Normally, beads should be applied to the treated side of the poly and nipped to the nonwoven or other substrate.
Preferred Mult:Lbead Settincrs Temperature 275°F., 300° F.
Nip Pressure 1.4 bar (20 psi) Application Rate 1.6 mg/inch/bead , Swivel Roll Applied, but no pressure Rewind and Unw:Lnd Tension As low as possible Web Speed 45 ~ 5 meters/min.
Use the following equation to determine either flow rate or web speed.
(Web speed (39.4 (App.
flow rate (g/min) - (M/min)) (in/M)) (rate) (G/in/bd) (#of beads) Run several meters of good application at 1.6 mg/inch/bead coat weight. During' the run, drop in 8-10 strips of release paper. Make sure they are applied as straight across the bead as possible.
1. Procedure for si~atic shear:
A. Sample preparation - mark along the bond line at 1 inch interv~~ls. Cut across 3 bond lines at these intervals. Cut: off the PE at one end and NW at the other end resulting i.n a t~~pical shear sample.
Prepare 7-8 samples.
B. Test procedure - preheat oven to 100° F. Preclamp all samples tc> be nested to a 50 gram mass. Hang all samples in oven as quickly as possible. Take care to insure that al:L samples hang freely and do not interfere with each other. Close oven, note starting time, and record failure times.
2. Procedure for Dynamic Peel:
A. Sample preparation - cut across the bond lines in the middle of the release paper. Then cut out about ..3 inches of a 1 inch wide strip containing 1 bead. The resulting strip should have 1 inch of release paper and 2 inches of a si:zgle bead. Prepare 7-8 samples.
B. Test procedure - run T-peels on 7-8 samples ~t room temperature using a crosshead speed of 1 in/min., 25 seconds dwell time. Start crosshead and run for 10 seconds and then reset the counter for 25 more seconds. Use this average for thE: peel value.
Report:
1: Static shfsar:
Average e:Lapsed hang time (in minutes) . , Failure mode (adhesive vs. substrates).
Additiona=L descriptive statistics and pertinent information such as adhesive I.D., application temperature, nip pressure, application rate .
Samples that sustain 480 minutes of loading should be recorded as such and noted a:~ "did not fail".
2. Dynamic Peel:
Average maximum force to rupture (in grams).
Failure mode (adhesive, substrate or cohesive).
Additiona7_ descriptive statistics and pertinent information as described above .
Comparative Example A
Using a sigma b:Lade mixer an adhesive for elastic attachment was selected from Puletti,, U.S. Pat. No. 4,419,494.
Table 2 Inaredient Name Percent A-B-A block copolyttier KRATON* 1102 30.0 A-B-A block copolyttier KRATON* 1111 5.0 Tackifying resin FORAL* 105 38.5 Tackifying resin ESCOREZ* 5320 20.0 *Trademark Plasticizing oil KAYDOL* 5.0 Antioxidant blend (IRGANOX*1010 & 1076) 2.0 Comparative Example B
Using standard hot melt processing technology, the following multi-line adhesive was :prepared from Schmidt, U.S. Pat. No.
4,526,557.
Table 3 Ingredient Name Percent Multiblock A-B-A-B--A-B
block copolymer STEREON* 840A 20.0 Tackifier ZONATAC* 105 LITE 60.4 Plasticizing oil White USP Mineral Oil 20.0 Antioxidant IRGANOX 1010 0.1 The adhesives c>f Table 6, No. 1, Comparative Example A and B were tested for visco:>ity, color, static shear, softening point, SAFT and creep resistance at 100° F. The results of that testing is shown in the following table.

Table 4 Adhesive of Table Example B 6, No. 1 Example A

Brookfield Viscosit=y spindle SC4-21 ' at 250 F. 11,240 cP 12,700 cP 341,000 cP

at 275 F. 5,430 cP 6,300 cP 145,000 cP

at 300 F. 2,970 cP 3,150 cP 73,000 cP

at 325 F. 1,768 cP 1,875 cP 41,400 cP

at 350 F. 1,170 cP 1,200 cP 24,900 cP

Gardner Color 2-3 3-4 12-13 Multiline Static Shears at 100 F. 143 min. 326 min. N/A*

Mettler Soft. Pt. 1'70 F. 187 F. 211 F.

SAFT 165 F. 177 F.

Creep Resistance 7:L% 5% 77.5%

of elastic attachment at 100 F.

Peel test** 105/110 F. 110/115 F. N/A*

Dynamic Peel Cohesive Substrate N/A

Adhesion failure failure (_L23 gms) Storage at total de- no N/A

140 F. lamination delamina-tion * The high visco~~ity adhesive intermittently clogged the extruder nozzle and when. not clogging the adhesive did not machine well - it did not form a fine line extrudate.
** (Pass/Fail, s~~e Schmidt, U.S. Pat. No. 4,526,577 Crossmachine direction.) ~3onds were made on a Meltex* CT-* 225 *Trademark according to procedures outlined in the static shear test method at a coat weight of 1.6 g/min.
The data recorded in Table 4 comparing a standard, elastic attachment adhe:~ive (Comparative Example A) and a standard multi-line construction adhesive (Comparative Example B) with the adhesive of Table 6, No. 1 of the invention shows that the invention in comparison to the Comparative Examples provides superior multi-line construction and elastic band attachment properties.
With respect t« the multi-line construction properties of the adhesives, applicant's adhesive is a significant improvement over the multi-line adhe:~ive disclosed in the Schmidt patent .
The multi-line static shear test indicates that the multi-line bond between the polyethylene film and nonwoven has a much greater resistance to shear at body temperature, indicating that the disposable article made with the adhesive of the invention would be much more likely to retain its mechanical integrity while worn. The dynamic peel adhesion test indicates that the Schmidt adhesive band beaween nonwoven and polyethylene is subject to adhesive failure, while the adhesive of the invention maintains the integ~°ity of the bond until the substrate itself fails. Such a resu=Lt additionally indicates that the adhesive bond is more likely to survive during use. The storage test at 140° F. indicates l~hat t:he adhesives of the invention when compared to the Schmidt adhesive are much more likely to retain an intact construction during high temperature storage. Should the disposable articles be subject to high temperature during storage and transpox-tation, articles made with the adhesive of the invention are much more likely to maintain structural integrity of the elastic. The articles made using the Schmidt adhesive suffer the drawback that the elastic may no longer be bonded to the polyet;hylen~~ backing sheet if stored at 140° F.
With respect to elastic attachment properties, Example A and Example B have a creep fai:Lure of the elastic attachment of 77.5%
and 71%, respective:Ly, indicating that the elastic once bonded to the polyethylene backing sheet could lose a substantial proportion of its stretch during use . In comparison, the adhesive of the invention loses only 5% of its stretch at these test conditions. Such test results indicate that once applied to the polyethylene backing' sheet, the elastic using the adhesive of the invention is securely bonded and has very little movement . These results indicate that when used in a disposable diaper, the elastics used in either a ~'_eg opening or waistband would maintain a tight, secure fit because the elastics were maintained in a correct position. When using the adhesives of the Puletti patent, the elastic; may not remain fully fixed to the poly resulting in a loose>., unacceptable fit.
Example I
In a Baker-Perkins twin screw 80 millimeter compounder extruder having 2 feed ports and.. maintained at 275° F., approximately equal volumes of radial block copolymer (KRATON D
1184) and tackifyin.g resin (ZONATAC 105) were blended using established extrusion processing techniques as described in "Continuous Production of Hot Melt Adhesives, Aspects of Quality and Coating", at a rate of 300 lbs. per hour by adding the copolymer and a portion of: resin to a feed port and the remaining resin through a second feed port. The blended rubber/resin mixture is extruded. through a three die section with multiple circular ports and is pelletized under 50° F. water. The pelletized preblend is treated with an aqueous talc dispersion (about 1 wt-o in water) to reduce blocking.
Example II
Example I was repeated except that the pellets are dusted with talc to reduce :blocking at a weight add-on of about 0.07 wt-o talc.
Example III
In a Baker-Per~~ins twin screw compound extruder having two feed ports and a single screw side stuffer at 275° F. at 300 lbs.
per hour manufacturing rate, an adhesive preblend of the following composition is made:

Table 5 Preblend I
Incrredient Name Parts (Wt . ) Radial block polymESr K 1184 1 Tackifier ZONATAC 105 1.5 The composition was pelletized in 90° F. water containing approximately 1 wt-°s talc resulting in a talc coating add-on of about 0.07 wt-o.
Into a heated sigma blade mixer was placed 19.6 parts of TUFFLO* 6056 oil, 0.5 part=s of WESTON* 619 antioxidant and 26.0 parts of Preblend I'. The contents of the mixer were agitated until uniform and into the mixer was placed 53.3 parts of the tackifying resin (PE'~RMALYl~d* 305) . This adhesive is shown as No.
1 in Table 6.
The following Table 6 sets forth adhesives and test results comparing the adhesives of the invention to adhesives of the prior art based on S'.CEREON 840A and KRATON 1111 and 1102 polymer.

*Trademark ._ ' 2002358 - 29 ~-N O
O lf1O tI1O N

.- 1 o cm n o o m a, o w o c~
E

M M rl N N cj,' ~,' lf7 r1 N

O

O.
O tn O ~ O O

. . . . ~ LL O z 01 u o c' n o 0 o w o w r., ~r E

M M r1 N N c~, r-I r~,' N
,-~

O

O
O O ~f1O t,f1O

m l O d' tl1 O O l0 w O w Q1 E

M M rl N rl r3,' Q', C' rl C' O

O LI1O tt1O O ~f' 01 . . . . . N w ~O

O C' t!7 O O w N U7 C~

N Q' ~ N l0 I~ V7 rl O
O lt1O tf1O ~I1 00 . . . . . N w 00 O C L!1 O O ~ 01 V7 N

N 'C'rl N lD Q1 U1 rl O
O ll1O lI1O lf1 N w O C' ll1 O O . I~ C~ C' N CW -1 N V~ 00 (n CD

O

O
U

. O
r-1tpO tl1O ll7O w .L1 . . .

O C tf1 O O 00 H N C' rl N ri O
O tf1O t!7O 00 . . . ,~ O

o c m o 0 o w m N
E

rl Lf1rl N rl rl U n M

u~
O ~1 O to O N

V' . . . . r-IO

O V' t!7 O O ~ O w CO
d' E

ri l!7r-i N r1 r1 U N
C' O t11O tf1O O

M . . . (n O
O ' ~ ~ O O Q1 O w M

E

u1 r-1 N .-1 U r1 ~D

M Q1 lf1 la tf~

N
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M t!1O Q1 O V7 vL.1 r1 r-I 00 M U~ r-i O
O CO O

M w r-1c!'O 01 C' ~ Cn N

LC)rl rl l0 lfl Cl~ M

W

z ~ H w ~ ~u c ~ ~a w w U x U o U
z o z z a ~ z o o ' ~

o a ~r,( ~ .,~ v 0 w o o N o z o o . w 0o ~

a o c~ ~n E .,~
E-~pG E-i E-m-i~ ~ H d W ~ U ~ ~n ~, ,, .~ N ~D o C~ N o o a~ -.1 ~0 .u ~ ra 4,'W ~I,'r,~,LY z V7 (')w [-1 N U v.r r-i o C
rl O O rl Lf1rl 01 I~ tI1-1 ~ Q1 tv r UI C G ~ N ~I
fx E~ ~ fx W p W ~ ~ W u .~ ~ O -.-1 E
I c ~--~.-io o ~ o o I ..~s, v .C
cp ~

. . >, ,.~ ~
x V1 ac x W N 3 H U .~
D m r-, ~ M m ~ ~ w o E

E-,W ~ U sa C1 v7 cn ~p W r0 .u ~r C1 .-~
~0 N

~~ ty a~
c a~
a~ x o a~

G
O O
O O
O O.
N ~
.'., .r., ww ~ >~ a~
a~

t~ ca D

co .~ .--I

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~ Z3 N
N

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~ ~ ~i ~

O QJ ii II

1~ 2 P., G Gr Gr O ~
~C

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.>Ju~~U ~

w ~

En O N

N
tT
'O
O
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v _ 1.~ it ~
C .-1 ~
.~ -.i ~i _ >~ rt1 -~
it w ~
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Table 6 compar~'s adhesives prepared with KRATON D 1184, a preferred high molecular weight radial block copolymer of the invention and comparison adhesives prepared from STEREON 840A (a linear multi-block A-B-A.-B-A-B copolymer), KRATON 1102, anal KRATON 1111 (two linear A-B-A block copolymers). The adhesives are compared at amounts r;~nging from about 10 to about 30 parts of polymer per about 100 parts of adhesives. These data clearly show that the adhesives made with KRATON D1184 are different and superior to conventional adhesives in adhesive properties. These superior properties are obtained from a polymer with a substantially different function, at substantially differing proportions to prow='_de substantially different test results.
The high molecular weight radial block copolymers of the invention function ;substantially differently than the polymers disclosed in the Sclzmidt patent. The Schmidt polymers are low molecular weight polymers having a molecular weight of less than 140,000 and the Schmidt patent is primarily directed to the linear A-B-A and A-B-A-B-A.-B block copolymer. These differences between the high molecular' weight radial block copolymers of the invention and the pc>lymer;~ of the Schmidt application result in the use of substantially reduced proportions of polymer that surprisingly give results that are superior to the Schmidt adhesives in a multi-line construction mode and provide an elastic attachment property that is lacking in the Schmidt adhesive materials.
Clearly only th~= KRATON D1184 adhesives containing less than about 15 wt-% of the high molecular weight radial block copolymer contained sufficient properties to enable manufacture of disposable articles using the adhesive in both a multi-line and elastic attachment mode.
In the dynamic:peel adhesion test, adhesives prepared using the linear block copolymers of the Schmidt patent provide adequate propertie:~ only at amounts of the polymer that approximate 20 wt-%. At lesser proportions the adhesive fails cohesively. At greater ;proportions, 30%, the adhesive fails adhesively either the nonwoven or the polyethylene backing sheet .
In sharp contrast, the adhesive of the invention using the high molecular weight racial block copolymers at amounts resulting in cohesive failure in the <~dhesives of the invention produce an adhesive bond stronger than the substrate which adhesive does not fail at test conditions .
In the elastic ;attachment mode, the adhesives prepared using the law molecular weight linear block copolymers fail to provide creep resistance. Additionally the adhesives of the Schmidt patent made with 30 wt-o of the prior art linear copolymers fail adhesively to the polyethylene backing sheet. The Schmidt adhesives fail to provide adhesion in the creep mode under stress. These adhE~sives also fail in an unstressed mode by losing bond integrity at :140° F. under storage conditions. Only the adhesives made with the high molecular weight radial block copolymer provide adequate: bond strength to maintain the elastic in a stretched configuration on the disposable article or in,a high temperature un:atressed storage environment.
With respect to adhesive viscosity, it is important to note that the viscosity of the adhesive of the invention No. 1 has a viscosity suitable for both multi-line and elastic attachment procedures. The adhesive in Table 6, No. 6 made with 20 wt-o of the high molecular weight radial block copolymers results in a viscosity that is t:oo hi.gh for either elastic attachment or multi-line properties. Wh~.ile at the same loading, the adhesives made with conventional low molecular weight polymers have a viscosity useful in multi~-line construction techniques.
We have shown in the: above discussion and tables of data that the adhesive of this invention is a superior multi-line/elastic attachment material . Additionally they are superior to standard prior art mult:i-line adhesives that are exemplified in Table 6 which ty~~ically contains substantially more polymer at increased cost.

Table 7 KRATON 1184 9.1:Z 9.12 KRATON 1117 4.9 4.9 ZONATAC 501 13.:L8 13.18 KAYDOL MINERAL OIL 19.4 19.4 WESTON 619 0.5 0.5 PERMALYN 305 47.9 49.9 AC-9 5.0 PETROLYTE E-1040 3.0 Creep 3.0"s 11.4%
resistance 4 hrs.
at 100 F.

Static shear at 275 min. 260 min.
100 F.

Viscosity at 275F 12,875 cP 9,325 cP

Storage at 140F. No change No change Dynamic Peel SSF SSF
Adhesion SSF = Substrate fai7_ure CF - Cohesive failure Table 7 shows that the use of other block copolymers in combination with a high molecular weight radial polymer will result in adhesive with unproved properties over the prior art.
In view of tree di~~closure and data in this case and particularly in view of Tables 4, 6 and 7, we have shown that the adhesive compositions of this invention are prepared from polymers having substantially different functions than that disclosed in the Schmidt. and Puletti patents. Further the adhesive properties are c>btained in a substantially different way, i.e. with different proportions. Lastly, the resulting properties are subst.antia_Lly different in that the adhesives of the invention are superior to the Schmidt materials in construction properties and possess properties not present in the Schmidt adhesives. Namely the adhesive compositions are useful as elastic attachment adhesives .while the Schmidt adhesives fail in this application.
The above discussion provides a basis for understanding the spirit and scope or the: invention.
However, since many embodiments of the invention can be made obtaining the benefits of the invention, the invention resides in the claims hereinafter appended.

Claims (25)

1. A disposable diaper comprising (i) a polymeric film substrate, (ii) at least one absorbent layer, and (iii) an elastic band, wherein the absorbent layer and the elastic band are independently bonded to the substrate with a hot melt adhesive composition, said adhesive comprising:
(a) about 5 to 14 wt-% of a radial block copolymer having a molecular weight of at least about 185,000, having the formula:
(AB)n1-Y-(B)n2 wherein Y is a multivalent coupling agent, A comprises a polyvinyl substituted aromatic block, B comprises a polybutadiene rubbery midblock, n1 is an integer of 3 to 10 and n2 is an integer of at least 0 to 10;
(b) about 45 to 85 wt-% of a compatible tackifying resin selected from the group consisting of a C5 resin, a styrenated C5 resin, a styrenated terpene resin, a hydrogenated C9 resin, a rosin derivative, a styrenated terpene resin and mixtures thereof; and (c) about 5 to 25 wt-% of a plasticizing oil.

2. The disposable diaper of claim 1 wherein the film comprises a polyethylene film or a polypropylene film.

3. The disposable diaper of claim 1 wherein the layer is bonded to the substrate using a multi-line adhesive construction.
Page 1 of Claims

4. The disposable diaper of claim 1 wherein the layer is bonded to the substrate using a multi-dot adhesive construction.

5. The disposable diaper of claim 1 wherein the elastic band is used in a disposable diaper leg band.

6. A disposable diaper comprising (i) a polyethylene or polypropylene film substrate, (ii) at least one absorbent layer comprising a tissue wrapped fluff and (iii) an elastic band, wherein the absorbent layer and the elastic band are independently bonded to the film substrate with a hot melt pressure sensitive adhesive composition comprising:
(a) about 5 to 14 wt-% of a radial block copolymer having a molecular weight of at least about 185,000 to 240,000 having the formula:
(AB)n-Y
wherein Y is a multivalent coupling agent, A comprises a polyvinyl substituted aromatic block, B comprises a polymeric rubbery midblock, and n comprises an integer of at least 3;
(b) about 0.1 to 10 wt-% of a linear A-B-A block copolymer wherein A is a polystyrene block and B is a polyisoprene or polybutadiene block;
(c) about 40 to 80 wt-% of a compatible tackifying resin selected from the group consisting of a C5 resin, a styrenated C5 resin, a styrenated terpene resin, a hydrogenated C9 resin, a rosin derivative and mixtures thereof; and (d) about 5 to 35 wt-% of a plasticizing oil.

Page 2 of Claims

7. The disposable diaper of claim 6 wherein the absorbent layer is bonded to the substrate using multi-line construction.

8. The disposable diaper of claim 6 wherein the elastic band is a leg band.

9. A disposable article comprising (i) a substrate, and (ii) at least one absorbent layer, wherein the absorbent layer is bonded to the substrate with a hot melt pressure sensitive adhesive composition, comprising:
(a) about 5 to 14 wt-% of a radial block copolymer having a molecular weight of at least 145,000, having the formula:
(A-B)n-Y
wherein Y is a multivalent coupling agent, A comprises a polyvinyl substituted aromatic block, B comprises a polymeric rubbery midblock, and n comprises an integer of at least 3;
(b) about 45 to 85 wt-% of a compatible tackifying resin selected from the group consisting of a C5 resin, a styrenated C5 resin, a styrenated terpene resin, a hydrogenated C9 resin, a rosin derivative, a styrenated terpene resin and mixtures thereof; and (c) about 5 to 35 wt-% of a plasticizing oil.

10. The disposable article of claim 9 wherein the substrate comprises a polymeric film.

Page 3 of Claims

11. The disposable article of claim 10 wherein the polymeric film is a polyethylene film or a polypropylene film and the absorbent layer comprises tissue.

12. The disposable article of claim 9 wherein the layer is bonded to the substrate using multi-line construction.

13. The disposable article of claim 9 wherein the layer is.
bonded to the substrate using multi-dot construction.

14. The disposable article of claim 9 wherein the article comprises a diaper having an elastic band.

15. The disposable article of claim 14 wherein the elastic band is used in a diaper leg band.

16. The disposable article of claim 9 wherein the article is a feminine absorbent pad.

17. A hot melt adhesive composition for the construction of disposable articles which comprises:
(a) 5 to 14 wt-% of a radial block copolymer having a molecular weight of at least 145,000 having the formula:
(A--Bn--y wherein Y is a multivalent coupling agent, A comprises a polyvinyl substituted aromatic block, B comprises a polymeric rubbery midblock, and n comprises an integer of at least 3;

Page 4 of Claims (b) about 45 to 85 wt-% of a compatible tackifying agent selected from the group consisting of a C5 resin, a styrenated C5 resin, a styrenated terpene resin, a hydrogenated C9 resin, a rosin derivative, a styrenated terpene resin and mixtures thereof; and (c) about 5 to 35 wt-% of a plasticizing oil; wherein the hot melt pressure sensitive adhesive has a static shear at 100°F of at least 30 min. , a creep resistance at 100°F of less than about 30% and exhibits a viscosity of less than 25,000 cP
at 275°F.

18. The adhesive of claim 17 wherein A comprises a polystyrene block and B comprises a hydrogenated or non-hydrogenated polymeric block comprising butadiene, isoprene, or mixtures thereof.

19. The adhesive of claim 18 wherein B comprises a polybutadiene block.

20. The adhesive of claim 18 wherein B comprises a polyisoprene block.

21. The adhesive of claim 17 wherein the plasticizing oil comprises a naphthenic, a paraffinic oil or mixtures thereof.

22. The adhesive of claim 17 wherein the viscosity comprises 5,000 to 10,000 cP at 275°F.

Page 5 of Claims

23. The composition of claim 17 wherein the creep resistance at 100°F comprises about 5 to 25%.

24. The adhesive of claim 18 wherein the adhesive additionally comprises 0.1 to 10 wt-% of a linear A-B-A block copolymer wherein A comprises a polystyrene block and B comprises a polymeric rubbery midblock comprising butadiene, isoprene, or mixtures thereof.

25. A hot melt pressure sensitive adhesive composition for the multi-line construction of disposable articles which consists essentially of:
(a) about 5 to 14 wt-% of a radial block copolymer having a molecular weight of about 185,000 to 240,000 having the formula:
(A-B)n-Y
wherein Y is a multivalent coupling agent, A comprises a polystyrene block, B comprises a polymeric butadiene midblock, and n comprises an integer of about 3 to 5;
(b) about 0.1 to 10 wt-% of a linear A-B-A block copolymer wherein A is polystyrene blend and B comprises polybutadiene block or polyisoprene block;
(c) about 40 to 80 wt-% of a compatible tackifying agent selected from the group consisting of a C5 resin, a Page 6 of Claims styrenated C5 resin, a styrenated terpene resin, a hydrogenated C9 resin, a rosin derivative, a styrenated terpene resin and mixtures thereof; and (d) about 5 to 35 wt-% of a plasticizing oil; wherein the hot melt pressure sensitive adhesive has a static shear of at least about 30 min. at 100°F, a creep resistance of at least about 30% at 100° and exhibits a viscosity of less than 15,000 cP
at 275°F.

Page 7 of Claims