WO2002032473A2

WO2002032473A2 - Adhesive attachment system

Info

Publication number: WO2002032473A2
Application number: PCT/US2001/032411
Authority: WO
Inventors: Martin Riswick; Gary F. Raykovitz; Dawn E. Smith
Original assignee: National Starch And Chemical Investment Holding Corporation
Priority date: 2000-10-17
Filing date: 2001-10-16
Publication date: 2002-04-25
Also published as: AU2002211791A1; WO2002032473A3

Abstract

An article comprising an adhesive attachement region is provided. A microsphere pressure-sensitive adhesive is coated on the attachment region of the article at a coat weight of from about 5 to about 100 g/m2.

Description

ADHESIVE ATTACHMENT SYSTEM

FIELD OF THE INVENTION The invention relates to an attachment system for articles of manufacture comprising a microsphere pressure-sensitive adhesive attachment region. Such articles include disposable articles and, in particular, disposable absorbent articles.

BACKGROUND OF THE INVENTION Disposable absorbent pads come in a wide variety of shapes and sizes, however, all generally employ a liquid impermeable barrier sheet coated or supplied with an adhesive attachment region(s). This adhesive attachment region has traditionally been coated with a hot-melt adhesive which is protected by a release liner prior to attachment of the article, e.g., a sanitary napkin or adult incontinent pad, to the fabric undergarment of the user. The release liner is left in place to protect the adhesive from contamination or from transfer to adjacent incontinent pads or sanitary napkins or packaging materials in the package prior to use.

U.S. Patent No. 5,514,122 discloses that the use of a detachable release liner may be eliminated on articles such as on sanitary napkins and on adult incontinent pads when the adhesive used in the attachment region is a pressure sensitive microsphere adhesive. The use of such an adhesive makes the pads stackable without release liners.

Pressure sensitive adhesive microspheres are known in the art to be useful in removable and repositionable pressure sensitive adhesive applications. Pressure sensitive adhesive microspheres usually consist of discrete, tacky, elastomeric particles that form a discontinuous film when coated, and are typically lightly crosslinked, low glass transition temperature, acrylic polymer particles having a particle size between 10 and 100 microns.

Such microspheres are easily deformed when a force is applied to them and recover their original shape upon release of the force.

When a removable pressure sensitive adhesive comprising microspheres comes into contact with a surface, the discontinuous film limits adhesion and provides removability over time. The adhesive tack of removable pressure sensitive adhesives may be controlled by adjusting the percentage of the adhesive surface covered by the microspheres, the extent of crosslinking, and the size of the microspheres. There are numerous references discussing the preparation of acrylic microspheres and acrylic microsphere pressure sensitive adhesives.

Typically, microspheres are prepared via suspension polymerization of one or more free radically polymerizable monomers in the presence of surfactants and/or suspension stabilizers. Prior art methods are described in for example, U.S. Patent No. 3,691 ,140, U.S. Patent No. 4,166,152, U.S. Patent

No. 4,495,318, U.S. Patent 4,598,112, U.S. Patent No. 4,786,696, U.S.

Patent No. 4,839416, U.S. Patent No. 5,571 ,617, U.S. Patent No. 5,656,705. While the use of pressure sensititive microsphere adhesives for the attachment of feminine hygiene pads and adult absorbent pads is known in the art, there continues to be a need for novel microsphere adhesives and for novel methods, including their use in the attachment of articles, such as absorbent pads and the like.

SUMMARY OF THE INVENTION The present invention provides an acrylic microsphere polymerization process, an acrylic microsphere adhesive and articles of manufacture comprising the adhesive. One aspect of the invention is directed to a disposable article comprising a pressure sensitive acrylic microsphere adhesive. In a preferred embodiment the disposable article is a disposable absorbent article, most preferable a disposable absorbent garment having an attachment region comprising a pressure sensitive acrylic microsphere adhesive.

A preferred embodiment of the invention is directed to a disposable absorbent article comprising a liquid-permeable topsheet, a liquid- impermeable backsheet, a fluid-absorbent core material positioned between the topsheet and the backsheet and an adhesive attachment region. The microspheres used to prepare the adhesive are formed by the suspension polymerization of acrylic monomers in the presence of a polymerization initiator and a stabilizer composition. In a preferred embodiment, the stabilizer composition comprises, as a primary surfactant, sodium dodecylbenzene sulfonate and, as a co-surfactant, sodium dihexylsulfosuccinate and/or sodium dioctylsulfosuccinate, and a polymeric stabilizer.

In the practice of the invention, the microsphere pressure sensitive adhesive is present, e.g., on an attachment region of a disposable article, at a coat weight of from about 5 to about 100 g/m², preferably 25 to 60, even more preferable at least about 30 g/m².

BRIEF DESCRIPION OF THE DRAWING FIGURES Figures 1-6 are photomicrographs taken at magnifications of Photomicrographs were taken at magnifications of ~50x (5x objective) Figure 1 , 3 and 6 shows a microsphere adhesive applied at a coat weight of 15 g/m². Figure 2 and 4 shows a microsphere adhesive applied at a coat weight of 30 g/m².

Figure 5 is a control.

DETAILED DESCRIPTION OF THE INVENTION

The disclosures of all references cited herein are incorporated in their entireties by reference.

Stabilizer composition means a combination of one or more materials suitable for use as a suspension stabilizer in the microsphere polymerization of acrylic monomers.

Parts per hundred monomer or pphm means the amount, on a weight basis, of any ingredient relative to 100 parts by weight of total active monomer.

Parts per million or ppm means the amount, on a weight basis, on any ingredient relative to one million parts by weight of the total composition.

Repositionable adhesive and removable adhesive are used interchangeably herein and such terms mean that a product coated with the adhesive has sufficient adhesive strength so as to remain stationary upon the application of pressure on a surface to which it has been applied, but can be removed from the applied surface and, if desired, repositioned on the same or another surface, without adhesive residue being left on the surface.

Primary surfactant refers to the anionic or non-ionic surfactant component of the stabilizer composition used in the polymerization of the microspheres used in the adhesive of the invention Co-surfactant refers to the anionic sulfosuccinate or sulfosuccinamate surfactant component of the stabilizer composition used in the polymerization of the microspheres used in the adhesive of the invention. Coat weight means the weight per unit area of adhesive coating deposited on a substrate once the coating has fully dried.

A disposable article means an article meant to be used and disposed of after one or several uses, preferable after a single use. Such articles include direct food contact labels such as informational labels attached to fresh fruit, e.g., apples, oranges and the like, price labels, resealable tabs for use in reclosure systems, e.g., tissue packages. This term encompasses disposable absorbent articles and disposable absorbent garments.

Disposable absorbent articles refer to articles comprising a component capable of absorbing and containing a fluid, including but not limited to body fluids. Examples include bed liners and bibs. This term encompasses disposable absorbent garments.

Disposable absorbent garments refer to articles designed to absorb bodily fluids, e.g., urine, menses, perspiration. Generally, such items attached to the interior surface of a garment such as underpants, shirt, bra, shoe and the like. Examples include feminine hygiene pads, incontinence pads, dress shields and nursing pads.

The microspheres used to prepare the adhesive of the invention are prepared by suspension polymerizing acrylic monomers in the presence of a polymerization initiator and a stabilizer composition. A preferred stabilizer composition comprises about 0.01 to about 5 parts per hundred monomer of an anionic and/or non-ionic primary surfactant; about 0.01 to about 2 parts per hundred monomer of an anionic sulfosuccinate and/or sulfosuccinamate co-surfactant; about 0.01 to about 4 parts per hundred monomer of a polymeric stabilizer; and an optional chelating agent. Even more preferred is a stabilizer composition comprises up to about 1 parts per hundred monomer of the primary surfactant; about 0.4 parts per hundred monomer of the co- surfactant; about 0.6 parts per hundred monomer of the polymeric stabilizer; and about 600 parts per million (wet basis) of a chelating agent.

Suitable anionic surfactants include, but are not limited to, alkyl aryl polyether sulfonates such as Triton X-200 from Union Carbide, and alkyl sulfates such as sodium or ammonium lauryl sulfate. Preferred anionic surfactants are alkyl aryl sulfonates such as sodium dodecyl benzene sulfonate.

Suitable non-ionic surfactants include, but are not limited to polyoxyethylene octyl phenol ethers such as Triton® X-100 and Triton® X- 405 from Union Carbide, polyoxyethylene nonyl phenol ethers such as

Igepal® CO-887 and Igepal® CO-660 from Rhone-Poulenc, polyoxyethylene stearyl ethers and polyoxyethylene oleyl ethers. The molar amount of ethylene oxide group (n) in these surfactants ranges from 1 to 100. Preferred non-ionic surfactants include polyoxyethylene stearyl ethers and polyoxyethylene oleyl ethers where n is 20 such as Brij®78 and Brij®98 from

ICI Surfactants.

Suitable anionic sulfosuccinate and sulfosuccinamate co-surfactants include, but are not limited to, sodium sulfosuccinate alcohol ethyoxylate, sodium sulfosuccinate alkyl phenol ethoxylate, sodium dicyclohexyl sulfosuccinate, sodium didecyl sulfosuccinate, sodium diamyl sulfosuccinate, disodium N-octadecyl sulfosuccinamate, tetrasodium N-(1 ,2-dicarboxyethyl)-

N-octadecylsulfosuccinamate, and sodium alkyl allyl sulfosuccinate.

Preferred anionic sulfosuccinate co-surfactants include sodium dioctyl sulfosuccinate and sodium dihexyl sulfosuccinate. Polymeric stabilizers which may be used to practice the invention are stabilizers which are conventionally used and are well known in the art for use as polymeric stabilizers. Such polymeric stabilizers include, but are not limited to, poly(vinyl alcohol), poly(vinyl pyrrolidone), cellulosics such as sodium carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose, carboxy-modified polyacrylamides such as Cyanamer A-370™ from American Cyanamid, and poly(vinylmethylether-co-maleic anhydride). Even more preferred polymeric stabilizers include poly(acrylic acid) and its ammonium, sodium, lithium or potassium salts or mixtures of its salts.

The stabilizer composition may also employ a chelating agent to impart stability to electrolytes that may be present as impurities in the formulation ingredients. The delating agent is typically used in the range of from about 100 to about 2,000 ppm. Suitable chelating agents include those described in U.S. Patent No. 5,656,705 and European Patent No. 0 710 678. A preferred chelating agent for use in the practice of the invention is ethylene diamine tetraacetic acid (EDTA). Preferably about 600 ppm EDTA is used. The chelating agent can be added during formulation or it can be added prior to polymerization. If it is present during the polymerization, the chelating agent has the advantage that it improves the robustness of the suspension to ionic contaminants, such as calcium and magnesium salts, which are found in some water sources.

Initiator and acrylic monomer are emulsified in an aqueous solution of the stabilizer composition described herein and polymerized by suspension polymerization. Monomers can be homopolymerized or copolymerized. For purpose of example, the following components may be used in a microsphere polymerization process: 2-ethyl hexyl acrylate (as a monomer); t-butyl peroctoate (as initiator); deionized water (for continuous phase); polyacrylic acid (as stabilizer); ammonium hydroxide (for pH adjustment); ethylene diamine tetraacetic acid (as chelating agent); sodium dodecyl benzene sulfonate (as primary surfactant); and sodium dihexyl sulfosuccinate (as co- surfactant).

While the use of 2-ethyl hexyl acrylate and t-butyl peroctoate is described in the examples, it is to be understood that the choice and the range of monomers and initiators that can be used in the microsphere polymerization process is extensive and can be chosen by one skilled in the art to tailor properties of the pressure sensitive adhesive microspheres for specific performance and/or application requirements, and can be tailored to provide removable adhesives with improved adhesive properties such as cohesive strength, peel adhesion and static shear.

Monomers useful in the practice of the invention include alkyl acrylates such as butyl acrylate, ethyl acrylate, methyl acrylate, and 2- ethylhexylacrylate, alkyl methacrylates such as methyl methacrylate and butyl methacrylate, polar comonomers such as acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxypropyl acrylate, N-tertiary octylacrylamide, acrylonitrile, acrylamide, 1-vinyl-2-pyrrolidone, sodium vinyl sulfonate, vinyl esters such as vinyl acetate, vinyl propionate, vinyl neodecanoate, vinyl stearate and vinyl pivalate. Cross-linking monomers such as butanediol diacrylate and hexanediol diacrylate can also be used. Other useful monomers and combinations thereof which can be used in the practice of the invention would be apparent to one skilled in the art.

Initiators useful in microsphere polymerization include dialkyl peroxides such as lauroyl peroxide trade name Laurox from Akzo Nobel, diacyl peroxides such as dibenzoyl peroxide trade name Lucidol A75 from Elf Atochem, peroxyesters such as t-amyl peroxypivalate (Lupersol 554-M50 from Elf Atochem), t-butyl peroctoate (Luperox 26 from Elf Atochem and Trigonox 21 from Akzo Chemicals), azo compounds such as 2,2'- azobis(isobutyronitrile) trade name VAZO 64 and 2,2'-azobis(2- methylbutanenitrile) trade name VAZO 67, and 2,2'-azobis(2,4- dimethylpentanenitrile) trade name VAZO 52, all from DuPont. Other useful initiators and combinations thereof which can be used in the practice of the invention would be apparent to one skilled in the art.

The microspheres for use in the invention may be formulated to provide removable pressure sensitive adhesives by any method known in the art. For example, adhesives may be formulated with the acrylic microspheres, a film forming acrylic binder, an alkali-soluble thickener, a defoamer and a biocide.

Binders are used mainly to improve anchorage of the microspheres, thus minimizing adhesive transfer. Useful binders should be compatible with the microspheres, and not affect removability of the final formulation. Examples include water-borne emulsion-polymerized acrylic or vinyl-acrylic polymers that are themselves pressure-sensitive adhesives. Typical compositions would contain 0-30% vinyl ester monomers, 0 to 30% alkyl methacrylate monomers, 0 to 6% polar monomers, the remainder being alkyl acrylate monomers, such that the glass transition temperature of the resulting polymer is less than about -20°C. One example of a commercially available binder is Rhoplex N-580 (Rohm and Haas).

The addition of a -thickener improves coatability and provides additional stability for the adhesive formulation. Preferred thickeners include alkali soluble emulsions, such as Acrysol ASE-75, ASE-60 ASE-95 and ASE-108 (commercially available from Rohm and Haas) and polyacrylamide- based dispersions such as Viscalex AT-77 from Ciba Specialty Chemicals. The amount of thickener can be adjusted to achieve a desired viscosity for specific coating methods. Conventional defoamers that can be used to practice the invention include agents sold under the trademark DEEFO 215 from Ultra Additives, Antifoam 1520, 1510 A and C from Dow Corning, and Foamaster 111 , 333 and S from Henkel Corporation. Biocides include Proxel DL by Avecia Biocides, Kathon LX and

Kordec 50C by Rohm and Haas, and the like.

Other conventional additives may be used as appropriate for specific applications. Such additional components include tackifiers, such as SNOWTACK 301 A, 342A, 385G and 348A from Akzo Nobel, TACOLYN 1070 from Hercules, AQUATAK 6080 from Arizona Chemical Company, and FORAL from Hercules, cross-linkers such as butanediol diacrylate and hexanediol diacrylate, as well as fillers, pigments, plasticisers, antioxidants, stabilizers, fire retardants, preservatives and rheology modifiers.

The adhesives of the invention find particular use in the manufacture of disposable articles, including disposable absorbent articles such as disposable absorbent garments. The article may be temporarily adhered to an object by the adhesive.

In one embodiment of the invention, a disposable absorbent product is provided, which disposable absorbent product comprises (1 ) a liquid- permeable topsheet, (2) a liquid-impermeable backsheet, which topsheet may be attached to the backsheet, (3) an absorbent structure positioned between the topsheet and the backsheet, and (4) an adhesive attachment region, and an optional release liner.

While such articles generally comprise a substrate or backing material, a backing is not required in all applications, as for example when used in the preparation of a self-supporting double-sided tape. When present, the backing material generally has at least a front and a back side or surface. When used in the construction of absorbent articles, a liquid impermeable backing, also referred to herein as a barrier backing is advantageously employed.

Those skilled in the art will recognize materials suitable for use as the topsheet and backsheet.

Exemplary of materials suitable for use as the topsheet are liquid- permeable materials, such as spunbonded polypropylene or polyethylene having a basis weight of from about 15 to about 25 grams per square meter.

Backsheets often used in disposable absorbent products are generally prepared from liquid-impermeable materials which function to contain liquids, such as water, urine, menses, or blood, within the absorbent core of the disposable absorbent product and to protect bedding and/or a wears' outer garments from soiling. Materials useful as a backsheet in a disposable absorbant product are generally impermeable to liquid but are permeable to vapor. Examples are liquid-impervious materials such as polyolefin films, e.g., polypropylene and polyethylene, as well as vapor- pervious materials, such as microporous polyolefin films, sometimes referred to as breathable films.

A particularly desirable backsheet material is a film comprising a polyolefin polymer such as a linear low density polyethylene and a filler. As used herein a "filler" is meant to include particulates and other forms of materials which can be added to the film polymer extrusion blend and which will not chemically interfere with or adversely affect the extruded film but which are able to be uniformly dispersed throughout the film. When the film is stretched during processing, the filler generally causes a network of holes to be formed in the film. Such holes are generally small enough to prevent the passage of a liquid, but are generally large enough to allow vapor to pass through the holes. Generally the fillers will be in particulate form and usually will have somewhat of a spherical shape with average particle sizes in the range of about 0.1 to about 7 microns. Both organic and inorganic fillers may be used in the practice of the invention provided that they do not interfere with the film formation process,. Examples of fillers include calcium carbonate (CaC0₃), various kinds of clay, silica (Si0₂), alumina, barium sulfate, sodium carbonate, talc, magnesium sulfate, titanium dioxide, zeolites, aluminum sulfate, cellulose-type powders, diatomaceous earth, magnesium sulfate, magnesium carbonate, barium carbonate, kaolin, mica, carbon, calcium oxide, magnesium oxide, aluminum hydroxide, pulp powder, wood powder, cellulose derivatives, chitin and chitin derivatives.

A removeable release liner or peelable film covering adhesive attachment region until the device is used can advantageously be used. A silicone-coated film is typically used for such applications. Just prior to use of the device, the proximal release liner is removed to expose the adhesive layer. Thus, the proximal release liner is adapted to be removed from the device and should strip off the adhesive surface with minimal force.

The article has disposed on at least one surface thereon the adhesive of the invention at a coat weight of from about 5 to about 100 g/m², preferably from about 25 to about 60 g/m² and more preferably at least about 30 g/m². A coating made in accordance with the invention gives an aggressive coating, but still has clean removeability. The adhesive may be coated on the substrate as a continuous or a discontinuous layer. The adhesive may be disposed over the entire surface (continuously or discontinuously) or only a portion thereon.

While the adhesive attachment region prepared in accordance with the invention are particularly advantageous for use in the construction of disposable articles, non-disposable articles are also encompassed by the invention. Examples of non-disposable articles include photograph album pages for holding and displaying photographs. Other non-limiting examples or articles encompassed by the invention include bed liners, feminine hygiene pads (which include conventional sanitary napkins and panty liners) and adult incontinence pads, dress shields, shoe insoles, bibs, identification badges, price labels, nursing pads, information stickers for clothing, upholstery and the like textile products, wound dressing, shoulder pads, bra pads, double- sided tapes including self supporting double-sided tapes, clothes hangers, stay fresh barrier for food, packaging for cosmetics, cigarettes, and facial tissue. Included within the scope of the invention are articles having at least a front and a back side, which article has a permanent adhesive on one side (e.g., the back side) and a microsphere adhesive applied in accordance with the invention on the other side (e.g., the front side). Such articles find use, e.g., in permanent attachment of one side of the article to a product, from which article a coupon can be removeably released from the other side of the article upon the purchase of the product.

While release liners can be used, as desired, the need for release liners on disposable articles, in particular disposable absorbent articles, can be eliminated by using the pressure-sensitive acrylic microsphere adhesive described herein. The tacky microspheres can be coated onto a barrier backing,. This adhesive coated barrier backing can then be wound for later use into a roll of tape or used to directly produce, e.g., a conventional sanitary napkin or adult incontinent pad, where the barrier backing forms the liquid impermeable backsheet and with no need for separate application of a release liner. Alternatively, the acrylic microsphere adhesive can be coated onto a barrier backing during the production process of the sanitary napkin or adult incontinent pad, and subsequently packaged without any need for a separately disposable release liner.

The microsphere adhesive provides secure attachment to a conventional fabric such as cotton, nylon, silk, polyesters and the like, commonly used in the construction of bedding, and clothing including hosiery, and the like, but does not transfer onto adjacent articles (e.g., sanitary napkins or adult incontinent pads) or packaging film when in the package prior to use. Also, when supplied in a tape form with the barrier backing, the barrier backing need not be release coated to facilitate tape unwind, which could interfere with subsequent manufacture of the absorbent pad or sanitary napkin.

The adhesive is coated onto a backing which generally is a thin water impermeable backing, preferably a thermoplastic film, which is most preferably a thin polyethylene polymer, copolymer or blend. The water impermeable backing layer can be treated by, such as but not limited to, corona discharge, to improve adhesion by the microsphere adhesive. Further layers can be provided depending on the end use of the repositionable and linerless adhesive/backing laminate. Absorbent layers and liquid permeable cover layers are used for sanitary napkins or adult incontinent pads where the repositionable linerless adhesive would be used to attach to the wearer's undergarment keeping the absorbent product in place. With bed liners, the laminate could directly adhere to the bed fabric or cotton sheet with or without a liquid absorbent layer attached to the opposite face of the backing, generally a liquid impermeable film layer. The present invention is further illustrated by the following Examples, but the particular materials and amounts thereof recited in these Examples, as well as other conditions and details, should not be construed as limiting the invention. All materials are commercially available or known to those skilled in the art unless otherwise stated or apparent. The following

Examples are illustrative in nature and are not intended to limit the invention in any way.

EXAMPLES

Examples 1-12 Microsphere polymerization Microsphere polymerization process A (used in Examples 1-9).

Acrylic microspheres suitable for preparing microsphere adhesives were prepared as follows.

A 2L four-neck round-bottom flask was equipped with a 4-inch crescent-shaped paddle stirrer, a water-cooled condenser, a temperature probe, a hot plate and propylene glycol bath, and an addition funnel. 280g 2- ethyl hexyl acrylate (monomer) was added to the round-bottom flask. 2.8g t- butyl peroctoate (initiator, 50% active) was dispersed in a total of 9.2g deionized water (half of which was used to rinse out the beaker used for mixing) and added to the flask. The contents of the flask were stirred at 250 rpm for 15 minutes. Agitation was stopped and 340g de-ionized water and stabilizer solutions (prepared as described below) were added using an addition funnel. The addition funnel was then removed and replaced with a sub-surface nitrogen inlet. Agitation was resumed at 250 rpm. The contents of the flask were mixed for 15 minutes while nitrogen was bubbled through at a rapid rate. The sub-surface nitrogen line was then removed and a nitrogen blanket was maintained above the condenser throughout the reaction. The contents were mixed at 250 rpm for an additional 15-30 minutes. The contents were then heated to 60°C over a 30-40 minute period. The onset of polymerization was detected by a sharp increase in temperature above 60°C. This polymerization exotherm was allowed to help heat the reaction from 60°C to 82°C. Each reaction was then held at 82°C for two hours before cooling to below 30°C. The contents were then discharged.

Preparation of stabilizer composition used in Example 1.

155.4g of deionized water was added to 10g 28% SLS (sodium lauryl sulfate) solution (Rhodapon LSB from Rhone-Poulenc) and stirred for five minutes with a magnetic stirrer. 6Jg of Good-Rite K-702 was then added followed by five minutes of mixing. 1.4g Versene 100 was then added followed by five minutes of mixing. About 1.1 g of 28% aqueous ammonium hydroxide was added dropwise until the pH reached 7.0.

Preparation of stabilizer composition used in Example 2.

155.4g of deionized water was added to 10g 28% SLS solution (Rhodapon LSB from Rhone-Poulenc) and stirred for five minutes with a magnetic stirrer. 1.4g of Aerosol MA 80-I (80% sodium dihexyl sulfosuccinate in isopropanol, from Cytec Industries, Inc.) was then added followed by ten minutes of mixing. 6Jg of Good-Rite K-702 was then added followed by five minutes of mixing. 1.4g Versene 100 was then added followed by five minutes of mixing. About 1.1 g of 28% aqueous ammonium hydroxide was added dropwise until the pH reached 7.0.

Preparation of stabilizer composition used in Example 3.

137.2g of deionized water was added to 28g of 10% aqueous SDBS (sodium dodecyl benzene sulfonate) (Rhodacal DS-4 from Rhone-Poulenc, diluted with de-ionized water to 10%) and stirred for five minutes with a magnetic stirrer. 6.72g of Good-Rite K-702 (25% poly(acrylic acid) from BF Goodrich) was then added followed by five minutes of mixing. 1.4g Versene 100 (35% active aqueous EDTA from Dow Chemical Company) was then added followed by five minutes of mixing. About 1.1g of 28% aqueous ammonium hydroxide was added dropwise until the pH reached 7.0.

Preparation of stabilizer composition used in Example 4.

126.0g of deionized water was added to 28g 10% SDBS solution and stirred for five minutes with a magnetic stirrer. 6Jg of Good-Rite K-702 was then added followed by five minutes of mixing. 1.4g Versene 100 was then added followed by five minutes of mixing. 11.2g of a 10% aqueous solution of Aerosol OT (sodium dioctyl sulfosuccinate from Cytec Industries, Inc.) was then added followed by ten minutes of mixing. About 1.1g of 28% aqueous ammonium hydroxide was added dropwise until the pH reached 7.0.

Preparation of stabilizer composition used in Example 5.

126.0g of deionized water was added to 39.2g 10% SDBS solution and stirred for five minutes with a magnetic stirrer. 6.7g of Good-Rite K-702 was then added followed by five minutes of mixing. 1.4g Versene 100 was then added followed by five minutes of mixing. About 1.1g of 28% aqueous ammonium hydroxide was added dropwise until the pH reached 7.0.

Preparation of stabilizer composition used in Example 6.

137.2g of deionized water was added to 28g 10% SDBS solution and stirred for five minutes with a magnetic stirrer. 14g of Gafquat 755 (a quaternized PVP copolymer from International Specialty Products) was then added followed by five minutes of mixing. 1.4g Versene 100 was then added followed by five minutes of mixing. Preparation of stabilizer composition used in Example 7.

135.8g of deionized water was added to 28g 10% SDBS solution and stirred for five minutes with a magnetic stirrer. 1.4g of a 80% aqueous solution of Aerosol MA (sodium dihexyl sulfosuccinate from Cytec Industries, Inc.) was then added followed by five minutes of mixing. 14g of Gafquat 755 (a quaternized PVP copolymer from International Specialty Products) was then added followed by five minutes of mixing. 1.4g Versene 100 was then added followed by five minutes of mixing.

Preparation of stabilizer composition used in Example 8.

126.0g of deionized water was added to 39.2g 10% SDBS solution and stirred for five minutes with a magnetic stirrer. 14g of Gafquat 755 (a quaternized PVP copolymer from International Specialty Products) was then added followed by five minutes of mixing. 1.4g Versene 100 was then added followed by five minutes of mixing.

Preparation of stabilizer composition used in Example 9.

137.2g of deionized water was added to 28g 10% SDBS solution and stirred for five minutes with a magnetic stirrer. 6.72g of Good-Rite K-702 was then added followed by five minutes of mixing. 1.4g Versene 100 was then added followed by five minutes of mixing. 1.4g of Aerosol MA 80-I (80% sodium dihexyl sulfosuccinate in isopropanol, from Cytec Industries, Inc.) was then added followed by ten minutes of mixing. About 1.1 g of 28% aqueous ammonium hydroxide was added dropwise until the pH reached 7.0. Microsphere polymerization process B (used in Examples 10-12).

Acrylic microspheres suitable for preparing microsphere adhesives were prepared as follows. In these examples, a mixture of acrylic monomers was used. A 2L four-neck round-bottom flask was equipped with a 4-inch crescent-shaped paddle stirrer, a water-cooled condenser, a temperature probe, a hot plate and propylene glycol bath, and an addition funnel. 266g 2- ethyl hexyl acrylate and 14.0g acrylic acid (monomers) were added to the round-bottom flask. 2.8g t-butyl peroctoate (initiator, 50% active) was dispersed in a total of 9.2g deionized water (half of which was used to rinse out the beaker used for mixing) and added to the flask. The contents of the flask were stirred at 250 rpm for 15 minutes. Agitation was stopped and 340g de-ionized water and stabilizer solutions (prepared as described below) were added using an addition funnel. The addition funnel was then removed and replaced with a sub-surface nitrogen inlet. Agitation was resumed at 250 rpm. The contents of the flask were mixed for 15 minutes while nitrogen was bubbled through at a rapid rate. The sub-surface nitrogen line was then removed and a nitrogen blanket was maintained above the condenser throughout the reaction. The contents were mixed at 250 rpm for an additional 15-30 minutes. The contents were then heated to 60°C over a 30- 40 minute period. The onset of polymerization was detected by a sharp increase in temperature above 60°C. This polymerization exotherm was allowed to help heat the reaction from 60°C to 82°C. Each reaction was then held at 82°C for two hours before cooling to below 30°C. The contents were then discharged. Preparation of stabilizer composition used in Example 10.

123.2g of deionized water was added to 42g 10% SDBS solution and stirred for five minutes with a magnetic stirrer. 1.4g Versene 100 was then added followed by five minutes of mixing.

Preparation of stabilizer composition used in Example 11.

121.5g of deionized water was added to 42g 10% SDBS solution and stirred for five minutes with a magnetic stirrer. 1.8g of a 80% aqueous . solution of Aerosol MA (sodium dihexyl sulfosuccinate from Cytec Industries, Inc.) was then added followed by five minutes of mixing. 1.4g Versene 100 was then added followed by five minutes of mixing.

Preparation of stabilizer composition used in Example 12.

109.2g of de-ionized water was added to 56g 10% SDBS solution and stirred for five minutes with a magnetic stirrer. 1.4g Versene 100 was then added followed by five minutes of mixing.

Results - microsphere polymerization.

The products from Examples 1 through 12 were free-flowing, aqueous microsphere suspensions that separated on standing to form two layers. The top layer was a concentrated suspension of polymeric microspheres and the lower layer consisted mainly of water. All suspensions were mixed thoroughly before testing was carried out. Results are shown in Table 1. Table 1

Examples 13-25 Adhesive Formulations

Examples 13-25 illustrate adhesive formulations prepared using the microsphere suspensions of Examples 1-12. Adhesives used in the invention will generally contain 60-100%, preferably 80-90%, microspheres on a dry weight basis. The rest comprising binder, as desired.

Examples 13-14 The adhesive formulations of Examples 13 and 14 were prepared using the microsphere suspensions from Examples 1 and 2, respectively. 200g of the microsphere suspension was stirred using a small paddle blade stirrer to give a good vortex but no foam generation. 20 grams Rhoplex N-580 (a 55% solids acrylic emulsion available from Rohm and Haas) and 3.2 grams of a premixed 1 :1 suspension of Viscalex AT-77 (a polyacrylamide-based thickener from Ciba Specialty Chemicals) and Isopar H (a hydrocarbon diluent available from Exxon) were added. Stirring was continued for 30 minutes. Examples 15-20 The adhesive formulations of Examples 15-20 were prepared using the microsphere suspensions from Examples 3-8, respectively.

50g of the microsphere suspension was stirred using a small paddle blade stirrer to give a good vortex but no foam generation. 5 grams Rhoplex N-580 (a 55% solids acrylic emulsion available from Rohm and Haas) and 0.8 grams of a premixed 1 :1 suspension of Viscalex AT-77 (a polyacrylamide-based thickener from Ciba Specialty Chemicals) and Isopar H (a hydrocarbon diluent available from Exxon) were added. Stirring was continued for 30 minutes.

Example 21 This adhesive formulation was prepared using the microsphere suspension from Example 9. 300g microsphere suspension was stirred using a 1.24" x 3.5" paddle blade stirrer at about 100 rpm to give a good vortex but no foam generation. 0.6 grams of a 14% aqueous ammonium hydroxide solution was added dropwise. After 10 minutes, a premixed solution of 1.15 grams Joncryl 61 (an acrylic copolymer from S.C.Johnson) and 1.0 grams propylene glycol was added. After 20 minutes, 30 grams Rhoplex N-580 (a 55% solids acrylic emulsion available from Rohm and Haas) and 0.44 grams Antifoam 1520 (a defoamer available from Dow Corning) were added. A premixed suspension of 2.3 grams Viscalex AT-77 (a polyacrylamide-based thickener from Ciba Specialty Chemicals) and 1.15 grams Isopar H (a diluent available from Exxon) were then added and stirring was continued for 30 minutes longer. Example 22 This adhesive formulation was prepared using the microsphere suspension from Example 9.

300g microsphere suspension was stirred using a 1.24" x 3.5" paddle blade stirrer at about 100 rpm to give a good vortex but no foam generation. 1.2 grams of a 14% aqueous ammonium hydroxide solution was added dropwise. After 10 minutes, a premixed solution of 2 grams Joncryl 61 (an acrylic copolymer from S.C.Johnson) and 0.45 grams propylene glycol were added. After 20 minutes, 30 grams Carbotac 26-222 (a 50% solids acrylic emulsion available from B.F. Goodrich) and 0.44 grams Antifoam 1520 (a defoamer available from Dow Corning) were added. 3.2 grams Acrysol ASE- 95NP and 3.2 grams Acrysol ASE-75 (alkali-soluble thickeners available from Rohm and Haas) were then added and stirring was continued for 30 minutes longer.

Examples 23-25 The adhesive formulations of Examples 23-25 were prepared using microsphere suspensions from Examples 10-12, respectively.

50g of the microsphere suspension was stirred using a small paddle blade stirrer to give a good vortex but no foam generation. 5 grams Rhoplex N-580 (a 55% solids acrylic emulsion available from Rohm and Haas) and 0.8 grams of a premixed 1 :1 suspension of Viscalex AT-77 (a polyacrylamide-based thickener from Ciba Specialty Chemicals) and Isopar H (a diluent available from Exxon) were added. Stirring was continued for 30 minutes. Results - Adhesive Formulations.

The adhesion formulations 13-25 were applied to the glossy side of 60 lb C1S label paper (Russel Field) using a # 32 meyer rod. The samples were dried at 250°F (121°C) for 10 minutes. 180° peel testing from stainless steel was carried out at 12in/min (304.8mm/min) according to PSTC-1. Peel values are shown as the average of 3 data points, in ounces/inch. The residue test was a subjective assessment of the application surface after the adhesive had been removed. Numbers were assigned on a scale from 1 to 7, where 1 = no detectable residue of any kind, 4 = surface residue observed but no adhesive was detected (often called "ghosting") and 7 = some adhesive residue was detected.

Test results are shown in Table 2.

Table 2

nt = not tested

Example 26 The microsphere adhesives of Examples 21 and 22 were coated out using a coating bar onto the treated (corona discharge) side of a polyethylene film (22 micron thickness from Trioplanex, Sweden) at a coating weight of 15g/m² and 30g/m². They were then allowed to air dry.

Standard peel tests were carried out on the resulting coatings as follows: Cotton Peel 1

The coatings were cut into strips of dimensions 25mm x 60 mm and applied to cotton fabric (dimension 50 x 100 mm ). Cotton type Testfabrics style 437 from Testfabrics Inc, US, adhesive applied to smooth side. 5 samples were prepared for each adhesive and coat weight variation. The 5 prepared samples were all placed under one 250g weight (area of surface contact 45mm x 50mm) in an oven set at 40°C for 1 hour. The weight was then removed and the samples were placed in a controlled temperature room at 23°C for 15 minutes. A t-peel was then carried out on a tensile tester at 500mm/min. The cotton was placed in the bottom jaw, whilst the adhesive coated polyethylene was placed in the top jaw of the tensile tester. The average peel force for the 5 samples was recorded in g/25mm. Cotton Peel 2

The coatings were cut into strips of dimensions 25mm x 60 mm and applied to cotton fabric (dimension 50 x 100 mm ). Cotton type Testfabrics style 437 from Testfabrics Inc, US, adhesive applied to smooth side. 5 samples were prepared for each adhesive and coat weight variation. The prepared samples were laminated using a Pearson Panke Auto Rolldown Machine. This comprises a 2kg rubber roller, width 50mm, diameter 90mm. The samples were passed under the roller twice at a speed of 300mm/min. A t-peel was then carried out immediately on a tensile tester at 500mm/min. The cotton was placed in the bottom jaw, whilst the adhesive coated polyethylene was placed in the top jaw of the tensile tester. The average peel force for the 5 samples was recorded in g/25mm. Nylon Peel

The coatings were cut into strips of dimensions 25mm x 60 mm and applied to ridged side nylon fabric (dimension 50 x 100 mm ). 5 samples were prepared for each adhesive and coat weight variation. The 5 prepared samples were all placed under one 1.6kg weight (area of surface contact 120mm x 60mm) in an oven set at 40°C for 4 hours. The weight was then removed and the samples were placed in a controlled temperature room at 23°C for 15 minutes. A t-peel was then carried out on a tensile tester at 500mm/min. The cotton was placed in the bottom jaw, whilst the adhesive coated polyethylene was placed in the top jaw of the tensile tester. The average peel force for the 5 samples was recorded in g/25mm.

Results are shown in Tables 3 (15 g/m²) and Table 4 (30 g/m²). Dispofix 655, a conventional hot melt positioning adhesive available from National Starch and Chemical Company, Europe, was tested for purpose of comparison.

Table 3

Table 4

The microsphere pressure sensitive adhesives show good performance in this application. No transfer of adhesive to nylon or cotton observed.

Example 27 Microscopy

The microsphere adhesives of Examples 21 and 22 were coated out using a coating bar onto the treated (corona discharge) side of a standard PE (polyethylene) film at a coating weight of 15 g/m² and 30 g/m². Each sample was exposed to iodine vapor inside a dessicator. On removal, the samples were laminated to clear Mylar PET using a 4lb-weighted roller. The laminates were examined under an optical microscope for the degree of contact between the adhesive and the PET (polyethylene terphthalate). A control was prepared by laminating the same type PE film without any adhesive coating. Photomicrographs were taken at magnifications of ~50x (5x objective) and ~200x (20x objective) in the reflectance mode. Backlight was used for some of the photomicrographs to highlight the underlying substrate pattern. The use of backlight helped to differentiate between the PE film, the microsphere adhesive in contact with the PET surface, and microsphere adhesive not in contact with the PET surface. Figure 1 shows the microsphere adhesive of Example 22 at a coat weight of 15 g/m². Figure 2 shows the microsphere adhesive of Example 22 at a coat weight of 30 g/m². Figure 3 shows the microsphere adhesive of Example 21 at a coat weight of 15 g/m². Figure 4 shows the microsphere adhesive of Example 21 at a coat weight of 30 g/m². Figure 6 shows the microsphere adhesive of Example 22 at a coat weight of 15 g/m², with backlighting. Figure 5 is the control.

When the microsphere adhesive is brought into contact with a transparent surface such as glass or PET, a complex squashed sphere morphology, in which individual spheres can be seen as circular areas, while clusters of spheres have rounded contours but featureless interiors, can be seen under the microscope.

The control sample showed a rough texture, specifically a cross- hatching diamond pattern that results from an embossing stage in the manufacturing process.

The laminated samples prepared from 15 g/m² adhesive coatings (Figures 1 , 3 and 6) showed areas of contact but also substantial areas where contact was not achieved. The diamond pattern of the PE film was clearly visible. The adhesive was following the contours of the patterned film. The adhesive was performing inefficiently, some regions entering into an adhesive bond but other regions failing to establish contact. The use of backlighting helped to show adhesive that was not in contact with the PET substrate.

The 30 g/m² coatings (Figures 2 and 4) had a completely different appearance. The adhesive established almost 100% surface contact with the substrate. Only small regions were left unbonded, with the adhesive bonding being much more continuous across the surface. The PE film pattern was obscured.

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

Claims

1. An article having an adhesive attachment region, said attachment region comprising a repositionable microsphere adhesive coated at a weight of from about 5 to about 100 g/m²

2. The article of claim 1 wherein the adhesive is coated at a weight of from about 25 to about 60 g/m².

3. The article of claim 1 wherein the adhesive is coated at a weight of at least about 30 g/m².

4. The article of claim 1 wherein the adhesive comprises 60 to 100 % microspheres.

5. The article of claim 4 wherein the adhesive comprises 80 to 90 % microspheres

6. The article of claim 1 wherein the article is a disposable article.

7. The article of claim 6 wherein the article is a disposable absorbent article.

8. The article of claim 7 wherein the article is a disposable absorbent garment.

9. The article of claim 7 which comprises a liquid-permeable topsheet, a liquid-impermeable backsheet, a fluid-absorbent core material positioned between the topsheet and the backsheet..

10. The article of claim 7 further comprising a release liner.

11. The article of claim 10 wherein the backsheet is attached to the topsheet.

12. The article of claim 9 which article is a feminine hygiene pad.