Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61Q—SPECIFIC USE OF COSMETICS OR SIMILAR TOILETRY PREPARATIONS
  • A61Q19/00—Preparations for care of the skin
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F13/00—Bandages or dressings; Absorbent pads
  • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
  • A61F13/56—Supporting or fastening means
  • A61F13/66—Garments, holders or supports not integral with absorbent pads
  • A61F13/82—Garments, holders or supports not integral with absorbent pads with means for attaching to the body
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K8/00—Cosmetics or similar toiletry preparations
  • A61K8/02—Cosmetics or similar toiletry preparations characterised by special physical form
  • A61K8/0208—Tissues; Wipes; Patches
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
  • A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
  • A61L15/42—Use of materials characterised by their function or physical properties
  • A61L15/58—Adhesives
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
  • A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
  • A61L15/42—Use of materials characterised by their function or physical properties
  • A61L15/58—Adhesives
  • A61L15/585—Mixtures of macromolecular compounds
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L24/00—Surgical adhesives or cements; Adhesives for colostomy devices
  • A61L24/04—Surgical adhesives or cements; Adhesives for colostomy devices containing macromolecular materials
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L53/00—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L53/00—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
  • C08L53/02—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers of vinyl-aromatic monomers and conjugated dienes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L53/00—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
  • C08L53/02—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers of vinyl-aromatic monomers and conjugated dienes
  • C08L53/025—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers of vinyl-aromatic monomers and conjugated dienes modified
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J153/00—Adhesives based on block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Adhesives based on derivatives of such polymers
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J153/00—Adhesives based on block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Adhesives based on derivatives of such polymers
  • C09J153/005—Modified block copolymers
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J153/00—Adhesives based on block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Adhesives based on derivatives of such polymers
  • C09J153/02—Vinyl aromatic monomers and conjugated dienes
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J153/00—Adhesives based on block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Adhesives based on derivatives of such polymers
  • C09J153/02—Vinyl aromatic monomers and conjugated dienes
  • C09J153/025—Vinyl aromatic monomers and conjugated dienes modified
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2666/00—Composition of polymers characterized by a further compound in the blend, being organic macromolecular compounds, natural resins, waxes or and bituminous materials, non-macromolecular organic substances, inorganic substances or characterized by their function in the composition
  • C08L2666/02—Organic macromolecular compounds, natural resins, waxes or and bituminous materials

Definitions

• the present invention relates to a combination of a substrate with a topical adhesive for attachment to the skin.
• the present invention relates to a combination of a substrate with a topical adhesive which can be employed for attachment to the skin in the area were absorption of bodily liquids is desired, particularly for the adhesion of sanitary napkins, pantiiiners, adult incontinence products or sweat pads.
• the combination provides secure attachment and is pleasing to the skin upon application, yet causes no discomfort upon removal. This is achieved by selecting the chemical composition and rheological characteristics of the topical adhesives and with the physical characteristics of the substrate on which the topical adhesive is applied, particularly the viscous modulus G" of the topical adhesive and the stiffness S of the combination of the substrate with the topical adhesive.
• the present invention relates to combination of a substrate with a topical adhesive which is particularly useful to absorbent articles for absorption of body liquids which naturally emanate from a body without a wound.
• a topical adhesive which is particularly useful to absorbent articles for absorption of body liquids which naturally emanate from a body without a wound.
• sanitary napkins or pantiiiners for example to attach sanitary napkins or pantiiiners in the genital region.
• incontinence devices which are worn e.g. in the genital region or sweat pads which are worn in the arm pit region of a person can suitably employ the adhesive of the present invention.
• Topical adhesives that are used for absorbent articles have generally been disclosed in US statutory invention registration H1602 or WO 96/33683. Some more details of the adhesive have been disclosed in PCT application WO 95/16424.
• sanitary articles having a topical adhesive which is applied on the wearer facing side of a sanitary napkin along the entire periphery are disclosed.
• the problem underlying this document is primarily the safe attachment to the skin but mentions also the problems of detachment of such articles after use without causing undue pain to a wearer.
• WO 95/16424 includes a detailed analysis of the criteria for the topical adhesive in respect to rheological criteria.
• rheological criteria taught include epilatory, i.e. hair removal, compositions which are commercially available such as STREP MIELE (TM) sold in Italy by Laboratori Vaj S.p.A.
• the adhesives for topical attachment mentioned in WO 95/16424 include also today's pressure sensitive adhesives which are used to attach sanitary napkins to undergarments. Further, this document only identifies static rheological characteristics but is silent as to the dynamic rheological behaviour of a topical adhesive.
• WO 96/13238 a frequency dependent topical adhesive model is disclosed. However, all measurements disclosed, e.g. on page 9, were made at temperatures between -60°C and +120°C and at actual frequencies of 0.1 to 100 rad/s. In order to obtain the necessary data at application temperature (about 20°C, typical bath room, i.e. storage temperature) the Williams-Landel-Ferry (hereinafter WLF) equation was used.
• WLF Williams-Landel-Ferry
• This WLF equation is empirical and only valid within certain limits e.g. it cannot be used to extrapolate to temperatures below the glass transition temperature of a polymeric adhesive also the WLF cannot be used on the basis of values obtained below the glass transition temperature. Details about the WLF equation and its applicability can be found in "Principles of Polymer processing" by Z. Tadmor and C.G. Gogos, published by John Wiley & Sons or in "Viscoelastic Properties of Polymers" by J.D. Ferry also published by John Wiley & Son. Since this is already missing from WO 96/13238 the applicability of the disclosed data cannot be assessed.
• European Patent Application EP-638 303 discloses the use of a topical adhesive on side cuffs of sanitary napkins in order to keep the cuffs in an upright position.
• Swiss publication CH-643730 discloses the use of a very long sanitary napkin having chamfered outer edges with a topical adhesive at the four corners of the outer edges in order to provide a topical adhesive area well outside the region of pubic hair growth. Both applications are silent as to the adhesive composition.
• the adhesive of the combination for topical attachment does not cause a cold or otherwise unacceptable temperature sensation upon application despite a temperature difference of the adhesive in respect to the skin temperature.
• topical adhesives of the combination are also desirable for topical adhesives of the combination to provide additional benefits such as delivery/dispersal of a compound or composition which is beneficial for the skin or for the body in general. Further, topical adhesives which do not affect the natural skin condition, e.g. by being breathable or water vapour transmitting or water vapour/sweat absorbing, are preferred.
• the present invention will be explained in its use on disposable absorbent articles for topical adhesive attachment to a wearer of such articles.
• the article typically has a wearer or body facing surface and an outside surface.
• the article comprises an absorbent core structure between the wearer facing surface and the outside surface for absorbing liquids emanating from a wearer such as urine, feces, menses, sweat and vaginal discharge.
• the article further comprises a combination of a substrate with a topical adhesive applied thereon, the combination having a stiffness or flexibility S measured in grams (g) according to the Flexibility Test method described hereinafter.
• the topical adhesive of the combination allows to attach an article to the skin of the wearer, being typically applied on the substrate on at least part of the wearer facing surface of the article.
• the viscous behaviour of the adhesive can be interpreted to represent an indication of the ability of the adhesive to quickly attach and securely adhere.
• the elastic behaviour can be interpreted as an indication of the "hardness" behaviour of the adhesive. Its value is also critical for good initial attachment. Their combination is believed to be an indicator of the required force upon removal.
• the relation between elastic and viscous modulus is considered to be an indication on which fraction of the removal energy will be dissipated within the adhesive and which fraction is available to trigger the actual removal.
• the relation between the elastic modulus and the viscous modulus as well as their dynamic behaviour is of key importance.
• the topical adhesive has an elastic modulus at a temperature of 37°C (100° Fahrenheit) abbreviated G' 37) a viscous modulus at a temperature of 37°C (100° Fahrenheit) of G" 37) and a viscous modulus at a temperature of 25°C (77°Fahrenheit) of G" 25 -
• the adhesive further has a dynamic elastic behaviour defined as ⁇ G' 37 which is the difference of G' 37 at a frequency of 100 rad/sec and G' 37 at a frequency of 1 rad/sec and a dynamic viscous behaviour ⁇ G" 37 which is the difference of G" 37 at a frequency of 100 rad/sec and G" 37 at a frequency of 1 rad/sec.
• the topical adhesive according to the present invention preferably satisfies the following conditions.
• G' 37 (1 rad/sec) is in the range 1500 Pa to 20000 Pa, preferably 1500 Pa to 15000 Pa, most preferably 3000 Pa to 10000 Pa.
• G" 37 (1 rad/sec) is in the range 100 Pa to 15000 Pa, preferably 100 Pa to 10000 Pa, most preferably 300 Pa to 5000 Pa.
• the ratio of G' 37 (1 rad/sec) / G" 37 (1 rad/sec) is in the range of 3 to 30.
• G' 37 (1 rad/sec) - G" 37 (1 rad/sec) is not less than 0.5, preferably in the range 0.7 to 3, most preferably in the range 1 to 1.8.
• ⁇ G' 37 is not greater than 10000 Pa, preferably less than 5000 Pa, most preferably less than 2000 Pa, or both.
• the value of the ratio G G' at least for the frequency range from above 1 rad/s up to 100 rad/s should preferably be 3.3 or above, more preferably 5 or above, most preferably 10 or above, while not exceeding about 30, preferably 20, anywhere in the frequency interval.
• Tg Glass Transition Temperature
• Tg should preferably be less than -15°C, more preferably less than - 20°C and most preferably less than -25°C.
• the rheological behaviour and acceptance of a topical adhesive can also be related to the specific heat capacity.
• the specific heat capacity of the topical adhesive is less than 4 J/g/K, more preferably less than 3 J/g/K and most preferably less than 2 J/g/K.
• the rheological behaviour and acceptance of a topical adhesive can also be related to the specific heat conductivity of the adhesive.
• the specific heat conductivity is as low as possible, preferably between 1 and 0.1 W/m/K, most preferably between 0.6 and 0.1 W/m/K .
• Adhesive compositions which satisfy the above criteria can be used as topical adhesives for disposable absorbent articles provided they also satisfy the common requirements of being safe for use on human or animal skin during use and generally after disposal of the article. Often the criteria of hygienic appearance and pleasant feel upon contact are important such that adhesive composition which are transparent or white, and which prevent a cold, unpleasant feeling upon application are preferred.
• compositions where the composition comprises from 45%, preferably from 51 %, to 99.5 % of a plasticising compound or composition which is liquid at 20°C, from 0.5 to 20 %, preferably 5 % to 15 %, of a polymeric compound or composition which is soluble or swellable in the plasticising compound or composition and with a tackifying resin in an amount in the range from 0% to 50% by weight of the composition, preferably from 0 % to 600 % by weight of the polymeric compound.
• the plasticising compound or composition is preferably selected from the group consisting of water, alcohols (preferably glycerol), glycols, polyglycols, liquid polybutenes, oil or combinations thereof.
• the polymeric compound or composition is preferably selected from the group consisting of block-copolymer-thermoplastic-elastomers, styrene-block- copolymers and hydrogenated styrene-block-copolymers, polyacrylics, polyvinyl alcohol, natural gum or gelatines, polyethyleneoxide, polyvinylpyrrolidon (PVP), polyvinylethers, cellulose derivatives, or combinations thereof.
• PVP polyvinylpyrrolidon
• the relation between the stiffness or flexibility S of the combination of the substrate with the topical adhesive applied thereon, on at least part of the body facing surface of the disposable absorbent article, and the viscous modulus G" 25 at about 100 rad/sec of the topical adhesive is relevant to the scope of providing an easy and painless removal from the wearer's skin of such a combination of a substrate with a topical adhesive used for attachment of a disposable absorbent article to the skin of a wearer.
• the combination according to the present invention of the substrate with the topical adhesive applied thereon is such that the viscous modulus G" 25 (100 rad/sec) of the topical adhesive and the stiffness or flexibility S of the combination satisfy the following empirical equation:
• the topical adhesive of the combination of the present invention is applied directly to the skin.
• the adhesive can be used on sanitary napkins which are applied in the genital region of a typically female user around the area of liquid discharge.
• the word "skin" according to the present invention does not only relate to the specific derma of the user but includes the mucous tissue as well as the hair which is typically found in the genital region of users of sanitary napkins.
• the topical adhesive of the combination of the present invention is provided onto at least part of the wearer facing surface of the disposable absorbent article by being applied on a substrate, which combination has a stiffness S measured in grams (g) according to the Flexibility Test described hereinafter.
• the combination can be joined or affixed with any known means to the disposable absorbent article as an additional layer, constituting at least part of the body facing surface of the article or, preferably, the combination can comprise partially or totally the absorbent article itself.
• the substrate can be the topsheet of the absorbent article, or, alternatively, the substrate can be the entire absorbent article.
• the substrate actually comprises the entire disposable absorbent article, typically constituted by at least a liquid pervious topsheet, a liquid impervious backsheet joined to said topsheet, and an absorbent core positioned between said topsheet and said backsheet.
• topical adhesive is provided along the peripheral edge of the topsheet such that a central area of the article is left without adhesive. This will most appropriately facilitate placing the napkin such that the liquid permeable topsheet region without adhesive is placed adjacent the bodily liquid emanating orifice such that emanating liquid is immediately transported into the absorbent structure of the absorbent article without the possibility of leakage or spillage.
• the topical adhesive is provided with the preferred pattern on the substrate on the wearer facing surface of the article in a layer that can be preferably continuous or alternatively discontinuous, e.g. in form of dots, spirals, or stripes, and having a thickness or caliper that is preferably constant.
• topical adhesives are used like pressure sensitive adhesives on human skin hair and mucous tissues, it is understood that the topical adhesive compositions could only with difficulty be considered typical pressure sensitive adhesives (referred to as PSA hereinafter) on the basis of the most characteristic rheological behaviours identifying such materials.
• materials useful as topical adhesives according to the present invention have rheological characteristics which are mostly measured at a reference temperature of 37°C (as usual body temperature of humans) and in a range of frequencies. It has been found that upon application of an article such as a sanitary napkin with a topical adhesive the adhesive contact is formed at a low frequency, while debonding happens at the speed of removing the article. This speed is expressed as a frequency of 100 rad/s while the low frequency of forming the adhesive bond has been found to be on the order of 1 rad/s. Therefore, the frequency range for use according to the present invention is between 1 and 100 rad/s.
• the adhesive bonding characteristics are selected most appropriately at human body temperature. Since the topical adhesive according to the present invention is used directly on skin and the person skilled in the art is directed to select the adhesive composition to have a small specific heat capacity (e.g. preferably less than 4 J/g/K) the actual temperature of the topical adhesive will reach 37°C very quickly or even be warmed up by a human prior to application.
• a small specific heat capacity e.g. preferably less than 4 J/g/K
• the absolute values of the elastic modulus should not be too high, otherwise the adhesive is too hard and it is not able to intimately join or mold to the surface to which it is expected to adhere. It is also important to have a low absolute value of G" in order to have good cohesion which is particularly valuable for use in the field of sanitary napkins while the material remains soft and capable of gently adhering to skin.
• the ratio of G' 37 (1 rad/sec) over G" 37 (1 rad/sec) is important to ensure that these two values are balanced upon adhesion to the skin.
• the absolute changes of G' 37 need to be limited within the range of frequencies considered.
• a value for the ratio of ⁇ G' 37 (i.e. G' 37 (100 rad/sec) - G' 37 (1 rad/sec)) over G' 37 (1 rad/sec) has to be kept small in order to maintain the secure attachment of the topical adhesive without causing discomfort over time or at removal/ delamination. This can also be expressed in absolute terms by keeping the ⁇ G' 37 below certain values.
• G' 37 (1 rad/sec) is in the range 1500 Pa to 20000 Pa, preferably 1500 Pa to 15000 Pa, most preferably 3000 Pa to 10000 Pa.
• G" 37 (1 rad/sec) is in the range 100 Pa to 15000 Pa, preferably 100 Pa to 10000 Pa, most preferably 300 Pa to 5000 Pa.
• G' 37 (1 rad/sec) - G" 37 (1 rad/sec) is not less than 0.5, preferably in the range
• ⁇ G' 37 is not greater than 10000 Pa, preferably less than 5000 Pa, most preferably less than 2000 Pa, or both.
• the value of the ratio G' 37 /G" 37 at least for the frequency range from above 1 rad/s up to 100 rad/s should preferably be 3.3 or above, more preferably 5 or above, most preferably 10 or above, while not exceeding about 30, preferably 20, anywhere in the frequency interval.
• Tg should preferably be less than -15°C, more preferably less than - 20°C and most preferably less than -25X.
• the rheological behaviour and acceptance of a topical adhesive can also be related to the specific heat capacity.
• the specific heat capacity of the topical adhesive is less than 4 J/g/K, more preferably less than 3 J/g/K and most preferably less than 2 J/g/K.
• the rheological behaviour and acceptance of a topical adhesive can also be related to the specific heat conductivity of the adhesive.
• the specific heat conductivity is as low as possible, more preferable between 1 and 0.1 W/m/K, most preferably between 0.6 and 0.1 W/m/K.
• compositions which satisfy the requirements of the above rheological and physical characteristics of a topical adhesive the following formulation criteria can be used in addition. It should be noted that the most of the compositions useful as topical adhesive have a substantially gel-like structure and are preferably gels. This derives from the fact that:
• the plasticiser which is a material liquid at room temperature
• a macromolecular or polymeric component is present in minor quantities vs. the plasticiser. It forms, in the preferred embodiments, a three dimensional network caused by physical or chemical links between the molecules. Particularly useful physical links are the ones present in systems containing Block Thermoplastic Elastomers.
• compositions typically comprise:
• macromolecular or polymeric substances can be natural and/or synthetic such as natural gums or derivatives such as natural gums and gelatins, their derivatives and alginates; polyacrilics; polyvinyl alcohol; polyethylene oxide; polyvinylpyrrolidon (PVP) or polyvinylethers, their copolymers and derivatives; cellulose derivatives; Block Copolymer Thermoplastic Elastomers and preferably Styrenic Block Copolymers and more preferably the hydrogenated grades Styrol/Ethylene-Butylene/Styrol (SEBS), Styrene/lsoprene/Styrene (SIS), and Styrol/Ethylene-Propylene/Styrol (SEPS).
• SEBS Styrol/Ethylene-Butylene/Styrol
• SIS Styrene/lsoprene/Styrene
• SEPS Styrol/Ethylene-Propylene/Styrol
• plasticising substance a plasticising substance or a mixture of plasticising substances, which are liquid at room temperature.
• the plasticiser can be water, various alcohols (like in particular glycerol), glycols and their ethers, polyglycols, liquid polybutenes, esters such phthalates, adipates, stearates, palmitates, sebacates, or myristates, natural or synthetic oils such as vegetable oils, mineral oils, or combinations thereof.
• composition from 0% to 50% by weight of the composition, preferably from 0 to 600 % by weight of the macromolecular polymeric substance of a tackifying resin whose main scope is to tailor the Tg especially in systems based on synthetic polymers.
• hydrophilic or hydrophobic liquid plasticisers may be for oily systems, e.g. the fatty acids of Cs to C22. their metallic salts and their polyoxo-dehvatives; lanolin derivatives; silica; bentonite, montmorillonite and their derivatives; polyamides, waxes or mixtures thereof.
• additives known in the art as preservatives, antioxidants, anti UV, pigments, mineral fillers, rheology modifiers etc. can also be comprised in quantities up to 10 % each.
• a crosslinking agent can be present preferably in quantities up to 5 % by weight.
• Chemical crosslinking can be formed also by mutual neutralisation of polymers having different functionalities as in the reaction between acid polyacrylics and polysaccharides.
• compositions for topical adhesives can be divided into three families according to the nature of the main component, i.e. usually the liquid plasticiser(s):
• hydrophilic compositions are not preferred while the hydrophobic and mixed phases compositions 1) and 2) are preferred in the applications of the present invention.
• hydrophilic compositions used in the medical field show too low elastic character and cohesion for being useful in the present application.
• the other reason to prefer hydrophobic or mixed phase compositions is that the application of the present invention in particular in the sanitary napkin field will include a probability of contacting the topical adhesive with the liquid to be absorbed. Since the liquids are all of a general aqueous kind contact with a hydrophilic topical adhesive would result in a certain absorption of the bodily liquids into the topical adhesives.
• topical adhesives also tend to be perceived as cold and wet which upon application to the skin of a human is not in line with typical expectation. Additional problems result from the fact that in particular topical adhesives comprising water as the plasticiser have a tendency to dry out unless they are sealed into an impermeable package.
• topical adhesive Absorbent articles in which the combination according to the present invention comprising the topical adhesive can be used, can be made by any of the ways usual in the art.
• the application of the adhesive to a substrate to form the combination of the present invention should not cause major problems to those skilled in the art since it can be provided by any well known techniques commonly used for other adhesives.
• the combination of the substrate with the topical adhesive can be applied to the absorbent article as an additional layer.
• the substrate can be partially or totally the absorbent article itself.
• the substrate of the combination can be the topsheet of the absorbent article.
• the substrate of the combination of the present invention is the entire disposable absorbent article.
• the substrate can comprise any suitable material, provided that the conditions set forth hereinbelow are satisfied.
• any material commonly used as a topsheet is suitable as the substrate for the topical adhesive composition in order to form the combination according to the present invention.
• the substrate of the combination according to the present invention is the entire absorbent article, e.g. comprising at least a topsheet, a backsheet and an absorbent core therebetween.
• the total area of the skin or wearer facing surface of an absorbent article comprising the combination of the present invention which is covered by the topical adhesive should be not more than 20 %, preferably not more than 10 %.
• the adhesive is close to the periphery of the absorbent article and when the substrate of the combination is constituted by, or comprises a film topsheet, the adhesive can be preferably on a portion of the film which is not permeable to liquids.
• the topical adhesive is applied on the substrate to form the combination on at least part of the wearer facing surface of the disposable absorbent article in a layer having a thickness or caliper that is preferably constant, or that alternatively can vary over the surface interested by the application of the topical adhesive.
• the article also provides breathability by being at least water vapour permeable, preferably air permeable to prevent stuffiness. Breathability, if not supported by the topical adhesive as such, can be limited to the area of the article where no adhesive is applied.
• the topical adhesive on an article is preferably protected prior to use. This protection can be provided by a release liner such as a siliconised or surfactant treated paper, providing easy release for the selected topical adhesive.
• This invention can be used beneficially on disposable absorbent articles which are applied directly to the skin of a user.
• the article usually exhibits absorbency for bodily fluids, the protection of the user's garments from soiling, is comfortable to the user, and is easy to produce and to package.
• the disposable absorbent article is described below by reference to a sanitary napkin or catamenial, however panty liners, adult incontinence articles or sweat pads are also included under the term disposable absorbent articles.
• sanitary napkin refers to an article which is worn by females adjacent to the pudendal region and which is intended to absorb and contain the various body fluids which are discharged from the body (e.g., vaginal discharges, menses, and/or urine) and which is intended to be discarded after a single use.
• a disposable absorbent article is preferably thin, more preferably between 1 and 5 mm thick and either substantially flat prior to use or in a preshaped form.
• joind or "affixed”, as used herein, encompasses configurations whereby a first member is directly connected to a second member and configurations whereby a first member is indirectly connected to a second member by connecting the first member to intermediate members which in turn are connected to the second member.
• a sanitary napkin of the present invention comprises a liquid pervious topsheet, a liquid impervious backsheet joined to the topsheet, and an absorbent core intermediate the topsheet and the backsheet.
• the sanitary napkin has two main surfaces, a body contacting or wearer facing surface on which the topical adhesive is applied and a garment facing or contacting surface.
• the topsheet is compliant, soft feeling, and non-irritating to the wearer's skin.
• the topsheet also can have elastic characteristics allowing it to be stretched in one or two directions in portions of the topsheet or throughout its extension. Further, the topsheet is fluid pervious permitting fluids (e.g., menses and/or urine) to readily penetrate through its thickness.
• Preferred topsheets for use in the present invention are typically selected from high loft nonwoven topsheets and apertured formed film topsheets.
• Apertured formed films are especially preferred for the topsheets because they are pervious to body exudates and yet non absorbent and have a reduced tendency to allow fluids to pass back through and rewet the wearer's skin.
• the surface of the formed film that is in contact with the wearer remains dry, thereby reducing body soiling and creating a more comfortable feel for the wearer.
• Suitable formed films are described in U.S. Patent 3,929,135; U.S. Patent 4,324,246; U.S. Patent 4,342,314; U.S. Patent 4,463,045; and U.S. Patent 5,006,394.
• a preferred topsheet for the present invention comprises the formed film described in one or more of the above patents and marketed on sanitary napkins by The Procter & Gamble Company of Cincinnati, Ohio as "DRI-WEAVE".
• topical adhesives are most suitably applied on topsheets having not a homogeneous distribution of liquid passage ways but only a portion of the topsheet comprising liquid passage ways oriented such that they result in a centrally permeable and peripherally impermeable topsheet for liquids.
• hybrid topsheets which incorporate fibrous and film like structures particularly useful embodiments of such hybrid topsheets are disclosed in PCT publications WO 93/09744; WO 93/11725 or WO 93/11726.
• topsheet When referring to the topsheet a multi layer structure or a mono layer structure is contemplated.
• the hybrid topsheet mentioned above is such a multi layer design but other multi layer topsheets such as primary and secondary topsheet designs are also considered.
• the absorbent core also can comprise multiple layers and provides fluid storage and distribution function.
• the absorbent core Positioned in fluid communication with, and typically underlying the topsheet is the absorbent core.
• the core can comprise any usual absorbent material or combinations thereof. It preferably comprises absorbent gelling materials usually referred to as “hydrogel”, “superabsorbent”, “hydrocolloid” materials in combination with suitable carriers.
• Suitable absorbent gelling materials for use herein will most often comprise a substantially water-insoluble, slightly cross-linked, partially neutralised, polymeric gelling material. This material forms a hydrogel upon contact with water.
• Such polymer materials can be prepared form polymerizable, unsaturated, acid- containing monomers, such as acrylic acid, which are well known in the art.
• Suitable carriers include materials which are conventionally utilised in absorbent structures such as natural, modified or synthetic fibers, particularly modified or non-modified cellulose fibers, in the form of fluff and/or tissues. Suitable carriers can be used together with the absorbent gelling material, however, they can also be used alone or in combinations. Most preferred are tissue or tissue laminates in the context of sanitary napkins/panty liners.
• An embodiment of the core particularly useful in the application of the present invention, comprises a double layer tissue laminate formed by folding the tissue onto itself. These layers can be joined to each other. Absorbent gelling material or other optional material can be comprised between the layers.
• the absorbent core can include optional components normally present in absorbent webs such as odor control agents, in particular suitable zeolites.
• the backsheet primarily prevents the exudates absorbed and contained in the absorbent core from wetting articles that contact the absorbent product such as underpants, pants, pyjamas and undergarments.
• the backsheet is preferably impervious to liquids (e.g. menses and/or urine) and usually manufactured from a thin plastic film.
• the backsheet typically extends across the whole of the absorbent core and can extend onto and form part of the topsheet by folding around the absorbent core. Thereby a topsheet configuration as disclosed in US 4,342,314, column 16, lines 47 - 62 can be achieved without the requirement to selectively aperture the topsheet.
• the backsheet also provides breathability to the absorbent article by being at least water vapour permeable, preferably air permeable.
• the backsheet can be a laminate material e.g. of a combination of microporous film and/or non- woven material, and/or apertured formed film. Breathability if desired can be limited to the periphery or the center of the backsheet or it can be across the whole backsheet.
• the relationship between the stiffness or flexibility S of the combination of the substrate with the topical adhesive applied thereon, as measured in grams according to the Stiffness Test described hereinbelow, and the viscous modulus G" 25 at 25°C and about 100 rad/sec of the topical adhesive gives an indication on the painless and easy removal of the topical adhesive from the wearer's skin.
• the combination of the substrate with the topical adhesive applied thereon is such that the viscous modulus G" 25 (100 rad/sec) and the stiffness or flexibility S satisfy the following empirical equation:
• the stiffness or flexibility S of the combination of the substrate with the topical adhesive is measured in grams (g) according to the Stiffness Test. It depends on the nature of the substrate and adhesive.
• the substrate comprises all layers that are joined to each other so as to unify them at least in the region corresponding to the region occupied by the topical adhesive.
• the stiffness of the combination of substrate plus topical adhesive depends strongly on which materials and how many layers actually correspond to the substrate.
• the combination of the substrate with the topical adhesive can be joined or affixed to the disposable absorbent article, or alternatively, the substrate can comprise partially or totally the absorbent article.
• the substrate of the combination can be joined or affixed to the absorbent article by any known means, e.g. by adhesive bonding, thermal bonding, mechanical bonding, or any combination thereof, but outside the region corresponding to the region where the topical adhesive is applied.
• the substrate of the combination can comprise one or more separate layers joined or affixed to the absorbent article e.g. along their respective contour edge, the remaining portions of the substrate being not joined to the absorbent article.
• the stiffness of the combination which is relevant in the removal of the absorbent article is that of the layer or layers constituting the substrate.
• the substrate comprises partially the absorbent article, e.g. typically corresponding to the topsheet, it can only be joined or affixed to the remaining part of the absorbent article substantially outside the region corresponding to the region occupied by the topical adhesive. Outside this region the substrate is joined by any known means.
• the flexibility or stiffness of the combination of the substrate with the topical adhesive actually corresponds to the flexibility or stiffness of the entire absorbent article including the topical adhesive, when the layers of the entire article are joined to each other so as to unify them at least in the region corresponding to the region occupied by the topical adhesive.
• a Removal Pain Grade Test has been developed where the adhesion of combinations having different stiffnesses due to different substrates covered with a layer of the same topical adhesive, on the skin of the forearm of members of a sensory panel is achieved, and upon successive removal the pain is evaluated in terms of pain grades.
• the stiffness of the combinations is in turn evaluated according to the Stiffness Test described hereafter.
• Removal Pain Grade Test is utilized to evaluate the pain during removal from the skin of a wearer of a sample provided with a layer of a topical adhesive and previously attached to the wearer's skin. The test specifically evaluates the pain upon removal of each sample as compared to the pain obtained by removing a reference sample constituted by a commercial strong medical plaster.
• the test is performed on rectangular samples 60x20 mm of the selected substrate provided on one side with a continuous layer of the topical adhesive having a constant thickness, applied with an Acumeter Model LH-1 extruder.
• the samples represent the different combinations of substrates with the topical adhesive.
• the reference sample is a 60x20 mm sample of a medical double sided adhesive tape produced by Minnesota Mining and Manufacturing Company under the trade name of No. 1524 Medical Tape; only one of the two layers of adhesive is exposed on the reference sample and used for attachment to the skin during the test.
• a panel of six graders is selected for the test.
• the test is performed in a climatically controlled lab where a temperature of 23 °C and a Relative Humidity of 50% are maintained. No special treatment of the wearer's skin is required beyond normal cleaning/washing with water and soap and drying at least two hours before the test to allow equilibrium with the room conditions is reached for the skin.
• Three different samples A, B, and C are evaluated in the test in comparison with the reference sample R. Each sample is applied by hand by an operator to the inner part of the grader's forearm, being centered between the wrist and the elbow, with the short side of the sample aligned with the length of the arm. The operator exerts on each sample with his palm the same pressure that is typically applied to cause a medical plaster to adhere to the skin.
• Each sample is worn for the prescribed time, and then it is removed from the grader's skin by the operator with a slow and smooth pull.
• the graders were asked to evaluate each sample A, B and C using a pain scale ranging from 0 to 10, where 0 corresponds to no pain and 10 corresponds to the pain upon removal of the reference sample R.
• results collected from the test were analyzed by a statistical analysis program "Comparison of Population Means - Paired Samples", that showed that the differences between the pain values of the samples A, B, and C are statistically significant.
• the Flexibility Test is utilized to quantify the flexibility or stiffness in machine direction of the combination comprising the substrate and the topical adhesive applied thereon.
• the flexibility test used herein is a dynamic stiffness measurement (force to deform vs. distance deformed), that determines the average force (in grams) required to compress a substrate in machine direction.
• the test is performed on rectangular samples 60x20 mm of the selected material cut with the longer side oriented in machine direction, and provided on one surface with a continuous layer of the topical adhesive having a basis weight of 1350 g/m 2 , applied with an Acumeter Model LH-1 extruder. Any protective release paper, if present, is removed before the test is carried on.
• the sample is positioned vertically and symmetrically between the fixed and the moving clamp, with each clamp holding a portion of the sample 5 mm wide along the respective short edge, with the exposed adhesive surface facing the operator. Contact between the clamps and the topical adhesive on the sample is prevented by applying on the topical adhesive a small rectangular piece of release paper about 20x5 mm on each end portion of the sample intended to be held by the respective clamp.
• the sample is slightly biased in order to bend during compression with the convexity on the adhesive surface.
• the clamps are so positioned to start the compression (in product machine direction) from a distance of 50 mm.
• the sample is compressed over a distance of 35 mm to a final clamp separation of 15 mm.
• the Instron records the clamp separation (in mm) and the force exerted to achieve this separation and sends this data via an RS232 interface to an IBM computer equipped with Microsoft Excel worksheet.
• the force and the distance data are loaded into the Excel software and the average force measurements over the full 35 mm compression cycle is determined.
• the measurements are performed and averaged on 5 samples of the same type to ensure a representative stiffness value to be determined for each sample under investigation.
• the topical adhesive is an oil based composition containing 10% by weight of Kraton G-1651 , a Styrene/Ethylene-Butylene/Styrene block copolymer available from Shell Co., 49 % by weight of Kaydol, a paraffinic mineral oil available from Witco Co., 40% by weight of Escorez 5300, a hydrogenated tackifying resin available from Exxon Co., 0.7% by weight of Magnesium Stearate, a co-gelifying agent for oil available from Carlo Erba S.p.A., and 0.3% by weight of Irganox 1010, an antioxidant available from Ciba-Geigy.
• the composition has the following rheological properties at 37°C.
• the composition further has a viscous modulus G" 25 at 25°C and at about 100 rad/sec of 4431 Pa.
• the three substrates of the combinations A, B, and C are as follows:
• Substrate of combination A is a nonwoven sold by Suominen under the trade name of Fibrella, code F2200/50, with a basis weight of 50 g/m 2 .
• Substrate of combination B is a polyester film 23 ⁇ m thick, such as that sold by Effegidi S.p.A. of Colorno (Parma, Italy).
• Substrate of combination C is prepared by applying to a polyester film of the same type already described for substrate of combination B a medical double sided adhesive tape produced by Minnesota Mining and Manufacturing Company under the trade name of No. 1524 Medical Tape. Only one of the two layers of adhesive of the medical tape is exposed and used for attachment of the double tape to the polyester in order to form a composite layered substrate. The release paper of the second adhesive layer of the medical tape is kept in its position. The topical adhesive is applied onto the polyester surface of the composite substrate to form the combination C.
• stiffness values for combinations of substrates with a topical adhesive used for attachment to the skin of disposable absorbent articles can be varied according to the empirical equations of the present invention in order to achieve acceptable removal pain grades with different topical adhesive compositions, and therefore with different values of G" 25 (100 rad/sec), within limits that can be readily determined by the man skilled in the art. Usually, in the field of disposable absorbent articles, this limit should not exceed 300 g. The same is true for possible selection of preferred topical adhesive compositions having different values of G" 25 (100 rad/sec) to be applied to a substrate having a certain fixed stiffness in order to reduce the pain grade upon removal of the absorbent article form the skin.
• G" 25 (100 rad/sec) of a topical adhesive composition are implicitly defined e.g. by the preferred rheological characteristics of the topical adhesive compositions.
• the pain upon removal can be further decreased when in the combination of the present invention the topical adhesive is provided onto the substrate in a layer having a thickness C measured in millimetres (mm) such that the viscous modulus G" 25 (100 rad/sec) and the thickness C of the topical adhesive satisfy the following empirical equation:

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