n a o ur

INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PC

(51) International Patent Classification ^* * (11) International Publication Number: WO 88/ 0 A41B 13/02 // C08L 23/04 Al

(43) International Publication Date: 6 October 1988 (06.

(21) International Application Number: PCT/US88/00760 (74) Agent: JOSEPHIC, David, J.; Wood, Herron & 2700 Carew Tower, Cincinnati, OH 45202 (US)

(22) International Filing Date: 3 March 1988 (03.03.88)

(81) Designated States: AT, AT (European patent), A

(31) Priority Application Number : 032,004 BE (European patent), BG, BJ (OAPI patent) CF (OAPI patent), CG (OAPI patent), CH, C

(32) Priority Date: 27 March 1987 (27.03.87) ropean patent), CM (OAPI patent), DE, DE ( pean patent), DK, FI, FR (European patent)

(33) Priority Country: US (OAPI patent), GB, GB (European patent), H (European patent), JP, KP, KR, LK, LU, LU ( pean patent), MC, MG, ML (OAPI patent), MR

(71) Applicant: CLOPAY CORPORATION [US/US]; 101 PI patent), MW, NL, NL (European patent),

East Fourth Street, Cincinnati, OH 45202 (US). RO, SD, SE, SE (European patent), SN (OAP tent), SU, TD (OAPI patent), TG (OAPI patent

(72) Inventors: CANCIO, Leopoldo, V. ; 5880 Turpin Hills

Drive, Cincinnati, OH 45244 (US). RYLE, Thomas, R. ; 5029 Idlewild Road, Burlington, KY 41005 (US). Published TOMANY, Robert, J. ; 6275 Delcrest, Fairfϊeld, OH With international search report. 45014 (US). WU, Pai-Chuan ; 9564 Linfield Drive, Before the expiration of the time limit for amendi Cincinnati, OH 45242 (US). claims and to be republished in the event of the r of amendments.

(54) Title: THERMOPLASTIC SHEET MATERIAL HAVING IMPROVED TAPE ADHESION

(57) Abstract

Novel thermoplastic sheet materials for permitting positionable and repeated repositionable use of tape faste therewith without experiencing substantial loss of tape adhesion therebetween are disclosed. A novel thermoplastic s material generally comprises an ethylene polymer and an anti-popoff substance in an effective amount for increasing substantially maintaining the tape adhesion. The increase in and substantial maintenance of the tape adhesion is ac plished without adversely affecting the properties or cost of the thermoplastic sheet material. A preferred formulatio producing the novel thermoplastic sheet material comprises polyethylene as the ethylene polymer and a polypropylen alpha-methyl styrene as the anti-popoff substance. The novel thermoplastic sheet materials are especially suitable for as films which can be used as backsheets in absorbent articles, such as, disposable diapers, bandages, surgical dressin drapes and catamenial pads.

FOR THE PURPOSES OF INFORMAπON ONLY

Codes used to identify States party to thePCT on the frontpages of imphlets publishing international appli- cations under the PCT.

AT Austria FR France ML Mali

AU Australia GA Gabon MR Mauritania

BB Barbados GB United Kingdom M Malawi

BE Belgium HU Hungary NL Netherlands

BG Bulgaria rr Italy NO Norway

BJ Benin JP Japan RO Romania

BR Brazil KP Democratic People's Republic SD Sudan

CF Central African Republic ofKorea SE Sweden

CG Congo KR Republic ofKorea SN Senegal

CH Switzerland LI Liechtenstein su Soviet Union

CM Cameroon LK Sri Lanka TD Chad

DE Germany, Federal Republic of LU Luxembourg TG Togo

DK Denmark MC Monaco US United States of America

FI Finland MG Madagascar

THERMOPLASTIC SHEET MATERIAL HAVING IMPROVED ^' TAPE ADHESION

Field of the Invention

The present invention relates to a thermo¬ plastic sheet material, and more particularly to a thermoplastic sheet material for use with absorbent articles, such as disposable diapers, wherein the thermoplastic sheet material has improved tape adhesion with pressure-sensitive adhesive tape-tabs.

Background

It has become common practice today to use disposable diapers with infants and incontinent people. Disposable diapers generally have a rectangular or hour glass shape and comprise an absorbent batt material sandwiched between an outer flexible polyethylene backsheet and an inner flexible polypropylene or polyester nonwoven frontsheet. The outer backsheet typically, but not necessarily, is water-impervious to prevent voided liquid absorbed into the absorbent batt material from striking throug the diaper and soiling the infant's adjacent clothing

or bedding. The inner frontsheet on the other hand i water-pervious to permit the voided liquid to pass therethrough into the absorbent batt material to maintain the infant in a dry, comfortable state. It is also well known and common practice i manufacturing disposable diapers to rely upon tape-ta fasteners as means for fastening the diapers about infants. The safety advantages and practicality of tape-tabs, rather than pins, is self evident. However, there are several shortcomings associated with their use. One major shortcoming lies in the loss or lack of tape adhesion between the tape-tab fasteners and backsheets following the original closures preventing the tape-tab fasteners from being positioned or repositioned on the backsheets. This shortcoming becomes immediately apparent when users, such as nurses or parents, attempt to separate the tape-tab fasteners from the diapers to inspect for soiling and refasten them following their inspection or when the diapers fall off due to the failure of tape-tab fasteners.

Some backsheet materials available heretofore for disposable diapers have very poor tape adhesion, i.e., the pressure-sensitive adhesives of the tape-tab fasteners do not or cannot adhere to the backsheets, making positioning or repositioning very cumbersome, if not virtually impossible. Unfortun¬ ately, this results in unsoiled diapers being

discarded and wasted following routine inspection or childrens' participation in the toilet-training ritual. This lack of reusability not only is inconvenient but also expensive because of the risin costs associated with disposable diapers.

In one attempt to solve the refastening problem, U.S. Patent No. 4,163,077, issued to Antons et al. on July 31, 1979, proposes to-formulate the pressure-sensitive adhesive of the tape-tab fastener with a rubbery block copolymer tackified with a combination of certain liquid and solid tackifiers t improve adhesion and shear properties when the backsheet is contaminated with foreign substances, such as talcum powder. VJhile U.S. Patent No. 4,163,077 reflects o attempt, there have been other attempts made in the past to solve the repositioning problem. Unfortunately, they have attempted to solve such problem by modifying either the tape-tab fasteners, the pressure-sensitive adhesives used therewith or b coating the tape-tab fastener bonding regions locate on the backsheets. These closure systems have the disadvantages of restricting the disposable diaper manufacturers to a particular tape-tab fastener arrangement, a particular pressure-sensitive adhesive formulation or added manufacturing steps, and forcing them to select only those backsheets that are coated at the bonding regions or are compatible with such

arrangements or pressure-sensitive adhesive formulations in order to produce an effective repositionable closure system. Such methods also ha the disadvantage of adding to the cost of manufac- turing disposable diapers.

Consequently, there is a definite need for repositionable yet inexpensive and flexible closure system that is not restricted to a particular tape-t fastener arrangement, pressure-sensitive adhesive formulation or coated backsheet, that has good tape adhesion when the diapers are initially closed, and that does not lose substantial tape adhesion upon repeated use of the tape-tab fasteners following occasional inspection for soiling or childrens' participation in the toilet-training ritual permitti unsoiled diapers to be reused.

Summary of the Invention

In brief, the present invention alleviates the above mentioned problems and shortcomings of the present state of the art through the discovery of a novel thermoplastic shee .material for permitting positionable and repeated repositionable use of a ta fastener therewith without experiencing substantial loss of tape adhesion therebetween. More particu¬ larly, the novel thermoplastic sheet material com¬ prises an ethylene polymer and an anti-popoff substance in an effective amount which accounts for

the increase in and substantial maintenance of the tape adhesion. The ethylene polymer can be a low density polyethylene, a linear low density polyethylene, a high density polyethylene or suitabl blends thereof. The anti-popoff substance can be, f instance, polypropylene, alpha-methyl styrene, ethylene-propylene copolymer and styrenic copolymers, such as styrene-butadiene-styrene block copolymer an styrene-isoprene-styrene block copolymer, which is preferably present in an amount of about greater tha zero up to about ten percent by weight of the sheet material. The unique increase in and substantial maintenance of the tape adhesion associated with the thermoplastic sheet materials of this invention is accomplished without adversely affecting the properties or cost of the sheet material while ob¬ taining the desired advantage of permitting positionable and repeated repositionable use of tape fasteners therewith. Moreover, in following the teachings of the present invention, disposable diaper manufacturers are no longer restricted to a particula tape-tab fastener arrangement or pressure-sensitive adhesive formulation since the thermoplastic sheet materials of this invention, when used as backsheets, can be formulated for compatible use with almost any repositionable tape-tab fastener or system.

The novel thermoplastic sheet materials of this invention are especially suitable for use as

films which can be used as backsheets in absorbent articles, such as bandages, surgical dressings or drapes and catamenial pads, and are especially suitable for use as backsheets in disposable diapers. When the thermoplastic sheet materials of this invention are used to formulate the backsheets of disposable diapers, they uniquely afford ^r cost saving and convenience advantages to users by permitting th tape-tab fasteners to be repositioned to the backsheets so that diapers can be reused with confidence following routine inspection or the toilet-training ritual. In other words, the refastened tape-tabs will adhere firmly to the backsheets, and the disposable diapers will remain i place following their opening or removal by the user The present invention therefore now makes it possibl to initially close a disposable diaper with confiden and to open the originally closed diaper for occasional inspection without fear that the tape-tab fasteners will not reposition on the backsheet, or without fear that the disposable diaper will reopen some point following the original closure or a subsequent closure.

The above features and advantages of the present invention will be better understood with reference to the accompanying Figs., Detailed Description and Examples. It also should be understood that the particular thermoplastic sheet

materials, absorbent articles and methods of this invention are exemplary only and not to be regarded limitations of the invention.

Brief Description of the Fig.

Reference is now made to the accompanying Figs, from which the novel features and advantages the present invention will be apparent: ^"

Fig. 1 is a diagrammatic view in side elevation of a schematic system of an extrusion apparatus suitable for producing the thermoplastic sheet materials of the present invention;

Fig. 2 is a graphic illustration exemplifying the percent increase in tape adhesion o a thermoplastic polyethylene sheet material formulat with a polypropylene or alpha-methyl styrene anti-popoff substance in accordance with the present invention; and

Fig. 3 is a graphic illustration exemplifying the percent increase in tape adhesion o two different commercially available tape-tab fasteners when they are separated (Method C) from a thermoplastic polyethylene sheet material formulated with various concentrations of a polypropylene anti-popoff substance in accordance with the present invention.

Fig. 4 is a graphic illustration comparing the percent increase in tape adhesion between a

polyethylene backsheet containing 5% polypropylene a a commercial tape-tab fastener designated herein as tape-tab fastener 5 over the tape adhesion between a similar polyethylene backsheet free of polypropylene and a similar commercial tape-tab fastener 5 followi an initial fastening and four refastenings.

Detailed Description of the Invention

By way of illustrating and providing a mor complete appreciation of the present invention and many of the attendant advantages thereof, the fol¬ lowing detailed description and examples are given concerning the novel thermoplastic sheet materials, absorbent articles made therewith and methods of production and use thereof.

As used herein, the term "tape adhesion" refers broadly to the force required to remove or separate a pressure-sensitive adhesive fastener from thermoplastic sheet material. The force required to remove or separate the fastener from the thermoplast sheet material is generally measured at a specified angle and at a given speed. Tests to determine tape adhesion may be conducted with an one-inch width fastener, such as a pressure-sensitive adhesive tape-tab fastener, at 90° (Test method A ) and 180° (Test method B) angles of peel at a pull speed of approximately 12 inches per minute at any desirable speed. Of course, it should be understood that the

tape adhesion can be measured at any other angle, su as between 90° and 180° (Test method C) and at different pull speeds. The results may be expressed in grams per inch width of the tape-tab fastener or percent increase as a function of the anti-popoff substance content.

Referring now more particularly to the present invention, the thermoplastic sheet material comprises an ethylene polymer and an anti-popoff substance in an effective amount for increasing and substantially maintaining the tape adhesion between the thermoplastic sheet material and a pressure-sensitive adhesive fastener adhered thereto In other words, the uniquely formulated thermoplasti sheet materials provide for improved tape adhesion following the original or subsequent bonding of a ta fastener to the thermoplastic sheet material. The ethylene polymers which may be used to formulate the thermoplastic sheet materials of the present inventi can be homopolymers of ethylene made from ethylene monomers or comonomers of ethylene with, for example butene, hexene, octene and methyl pentene. Particul ethylene polymers that are suitable for use in the present invention are polyethylenes and more particularly low, linear low or high density polyethylenes or any suitable blends thereof.

By the term "anti-popoff substance," it is meant herein to refer broadly to any substance that,

when combined with an ethylene polymer to form a thermoplastic sheet material of the present inventio can act to increase and substantially maintain the tape adhesion between the thermoplastic sheet materi and a pressure-sensitive adhesive fastener for permitting positionable and repeated repositionable use of the fastener therewith. The unique formulati of an anti-popoff substance in an effective amount with an ethylene polymer can be used to formulate a novel thermoplastic sheet material of the present invention which is believed to be more- resistant to tape fastener peel following positioning or repositioning than heretofore achieved. In other words, the thermoplastic sheet materials of the present invention prevents pressure-sensitive adhesi fasteners from popping off of the sheet materials following their being initially positioned or repositioned thereon.

In determining how much of the anti-popoff substance to incorporate into the thermoplastic shee material, it is necessary to take into account the pressure-sensitive adhesive of the tape fastener selected for use. When anti-popoff substances havin high bonding affinities for the pressure-sensitive adhesives are selected, lesser amounts are required be incorporated into the sheet materials than when anti-popoff substances having low bonding affinities are selected. Nevertheless, it is found as a genera

rule that an effective amount can range from about greater than 0 up to about 10% and more particularl from about 0.75% to about 5% by weight of the thermoplastic sheet material. Regardless of the amount utilized, however, it is preferred to utilize an amount that does not cause the tape adhesion to exceed the tearing strength of the sheet material which can be determined by any conventional techniqu well known to those versed in the art. The tearing strength is a function of, inter alia, the thickness and components of the thermoplastic sheet materials. Preferred anti-popoff substances which may be used t formulate the thermoplastic sheet materials of the present invention are polyproylenes and copolymers thereof, alpha-methyl styrene and styrenic copolymer The preferred anti-popoff polymers include polypropylene, alpha-methyl styrene, ethylene-propylene copolymer, styrenic copolymers, such as styrene-butadiene-styrene block copolymer an styrene-isoprene-styrene block copolymer, and suitab mixtures thereof. The most preferred anti-popoff polymers are a polypropylene and an alpha-methyl styrene. Although the above represents preferred amounts and anti-popoff substances, it should be understood that any effective amount of and any suitable substance, polymer or blends of polymers ma be used as the anti-popoff substance. Of course, by the term "effective amount," it refers to any amount

of a suitable anti-popoff substance in an ethylene polymer sheet material that can increase and substantially maintain tape adhesion between the ethylene polymer sheet material and a tape-tab fastener--'following initial and/or repeated re-fastenable use.

Exemplary of two preferred formulations fo producing a thermoplastic sheet material contemplate by the present invention comprises a polyethylene as the ethylene polymer and a polypropylene or alpha-methyl styrene as the anti-popoff substance. Such formulations generally comprise by weight about 90 to about less than 100% polyethylene and about greater than 0 to about 10% polypropylene or alpha-methyl styrene. As reflected in Fig. 2, there is a dramatic increase in tape adhesion when polypro pylene is selected as the anti-popoff substance. There is, however, only a gradual increase in tape adhesion when alpha-methyl styrene is utilized as th anti-popoff substance. This is also reflected in Fi 2. Even when minor amounts of polypropylene are blended into the sheet materials, the tape adhesion still dramatically increases as compared to a simila thermoplastic polyethylene sheet material having no polypropylene incorporated therein. This can be observed in Table I (Test method A) and Table II (Te method B) where the polypropylene accounts for only

about 0.75% and about 1.3% of the weight of the shee materials, respectively.

TABLE I

Percent Increase in Tape Adhesion (%) — Test Met

Thermoplastic Polyethyl

Anti-popoff substance (polypropylene) Content (%) 0 0.

Commercial Diaper Tape-Tab 1 6

Commercial Diaper Tape-Tab 2 5

TABLE II

Percent Increase in Tape Adhesion (%) -- Test Met

Thermoplastic Polyethy

Anti-popoff Polymer substance (polypropylene) Content (%) 0 0

Commercial Diaper Tape-Tab 1

Commercial Diaper Tape-Tab 2

As a further feature of the present invention, the tape adhesion between a sheet materia having an anti-popoff substance and a tape-tab fastener remains substantially the same even after a repeated number of refastenings. This feature is demonstrated in Fig. 4 wherein the percent increase tape adhesion between a polyethylene backsheet containing 5% polypropylene and commercial tape-tab fastener 5 remained virtually the same as when compared to the tape adhesion between a similar polyethylene backsheet free of polypropylene and commercial tape-tab fastener 5 after five refastenings.

It should be appreciated, however, that eventhough the tape adhesion between a sheet materia of this invention and a tape-tab fastener following a repeated number of fastenings might be less than the original fastening, it is nevertheless believed that such tape adhesion will usually be greater than the adhesion between a sheet material free of an anti-popoff substance and a tape-tab fastener having an equal number of refastenings. Therefore, the term "substantially maintaining tape adhesion" is used herein in a broad sense to refer to not only those instances where the tape adhesion increases or remain substantially the same following repeated fastenings but also to those instances where there is any increase in tape adhesion between the sheet materials

of the present invention and a tape-tab fastener over the tape adhesion between similar sheet materials fre of anti-popoff substances and a tape-tab fastener following refastening. While the inventors do not wish to be limited to any particular theory in which the tape adhesion is increased and substantially maintained, they presently believe that the incorporation of a minor amount of an anti-popoff substance into a thermoplastic ethylene-based sheet material interrup the surface packing of the ethylene polymer, particularly when the ethylene polymer is a polyethylene, resulting in higher surface free-energ associated with the sheet material thus improving th adhesion of pressure-sensitive adhesive fasteners thereto. It is also presently believed that the objectives of this invention can be easily met particularly when the pressure-sensitive adhesive formulation of the selected tape-tab to be used is known by selecting an anti-popoff substance that has high bonding affinity for the particular pressure-sensitive adhesive. Even when the pressure-sensitive adhesive formulation is unknown, is still belie'ved that the objectives of this invention can be met by utilizing one of the polymer substances employed to formulate the backsheet tab o the tape-tab fastener selected as the anti-popoff substance. Generally speaking, a polymeric substanc

commonly utilized to formulate the backsheet tabs of tape-tabs today particularly in the disposable diape industry is a polypropylene. Since polypropylene generally has a high bonding affinity for the pressure-sensitive adhesives utilized with the tape-tab fasteners and is the commonly employed polyolefin utilized to form the backsheet tabs of th tape-tab fasteners, these factors make'polypropylene preferred anti-popoff substance. Basically any commercially available pressure-sensitive adhesive tape-tab fasteners used disposable diaper construction today are suitable fo use with the thermoplastic sheet materials of the present invention. For example, six different commercially available pressure-sensitive adhesive tape-tab fasteners have been utilized herein, and al six have been found to be substantially equally suitable. While the precise formulas of the pressure-sensitive adhesives utilized to form the si different tape-tab fasteners are unknown, it is presently believed that the pressure sensitive adhesive of tape-tab fastener 5 comprises a styrene-isoprene-styrene block copolymer base, an aliphatic mixed olefin tackifying resin and an anti-oxidant. It is also believed that the backsheet tab of tape-tab fastener 5 is formed with a polypropylene. Of course, it should also be appreciated that there are many other commercially

available tape-tab fasteners being used by the disposable-diaper manufacturers that have pressure-sensitive adhesive formulations which are different than the pressure-sensitive adhesive formul of tape-tab fastener 5 described above that are also suitable for use with the present invention.

The commercial tape-tab fastener 5 referred to above can be easily prepared by any ^' _. conventional means, such as by coating the pressure-sensitive adhesive composition just described onto the face sid of a polypropylene-backing tab.

.With reference now to Fig. 1, a slot cast film extrusion method for making the thermoplastic sheet materials of the present will be described. In this method, the thermoplastic sheet materials are generated simply by blending a selected ethylene polymer with a particular anti-popoff substance in an effective amount and extruding the mixture through a conventional extrusion die adapter 1 and cast film di 2 to form the molten web 3. Molten web 3 is then rolled between a metal roll 4 and a rubber roll 5. When an embossed film is desired, an embossing sectio 6 is located on metal roll 4. The sheet materials ca be embossed with any suitable design according to any of a number of well-known techniques. For example, embossing can be performed by the introduction of a pre-formed sheet material into a system of embossing rolls or by the introduction of an extruded melt of

the thermoplastic material through a slot-die betwee embossing rolls. The molten web 3 is then directed onto a chilled metal roll 7 to form the cooled extruded film 8 which is then wound onto a storage roll (not shown) . While the above describes thermoplastic sheet materials of the present inventi being produced by a slot cast film extrusion method, the thermoplastic sheet materials can be produced by blown film extrusion methods as well. These differe processes of making and embossing are described in more detail in U.S. Patent Nos. 4,535,021, 4,546,029 4,376,147 and 3,484,835 which are incorporated herei in their entirety by reference.

In a further feature of the present invention, the thermoplastic sheet materials can be produced by either single extrusion or co-extrusion. When the sheet materials are produced by single extrusion, the anti-popoff substance is generally dispersed throughout the single layer of the films. When the sheet materials are co-extruded, the anti-popoff substance can be generally dispersed either throughout each layer or throughout one or mor layers of the films. For instance, the anti-popoff substance can be generally dispersed throughout the top and/or bottom layers of a two layer or the top, bottom and/or middle layers of a three layer co-extruded film, .it is necessary, however, to disperse the anti-popoff substance at least throughou

the layer of the co-extruded sheet material that is t receive the tape-tab fastener thereon.

Although the sheet materials can be formulated by adding the anti-popoff substance directly to the ethylene polymer to form a pre-extrusion mixture, it is found that better result are achieved when the selected ethylene _polymer is blended with a concentrate containing, ^~~ inter alia, th anti-popoff substance. The concentrate may also include, for instance, an ethylene polymer carrier, such as a conventional low density polyethylene or a conventional linear low density polyethylene, and titanium dioxide as a whitener. Preferred concentrates are those in which the anti-popoff substance is polypropylene wherein the polypropylene is present in an amount ranging from about 5 to about 50% by weight of the concentrate. Such preferred concentrates can further include the ethylene polymer carrier in an amount ranging from about 45% to about 0% and titanium dioxide (TiCC-.) in an amount of about

50% by weight. Examples of three formulations of suc preferred concentrates suitable for use in accordance with the teachings of the present invention are designated as Concentrates I-IV as follows:

Concentrate II III IV polypropylene parts 5 25 45 50 polyethylene parts 45 25 5 0

TiO-, parts 50 50 50 50

Total Parts 100 100 100 100

The preferred concentrate should be intimately blende with an ethylene polymer and in particular a polyethylene in an amount ranging from about 8 to about 10 parts concentrate to about 100 parts polyethylene to form the pre-extrusion mixture which can then be extruded as described above to form liquid-pervious or liquid-impervious sheet materials, such as backsheets. The thermoplastic sheet materials of the present invention are especially suitable for use wit absorbent articles, such as disposable diapers, bandages, surgical dressings or drapes and catamenial pads and most particularly with disposable diapers. When the thermoplastic sheet materials are to be used with the absorbent articles, they can be formulated into thin films that are either liquid-pervious or liquid-impervious, that have either smooth or embosse surfaces and that have either dull or glossy finishes. The thickness of the film can vary over a wide range. When the thermoplastic sheet materials are to be formulated into thin films that are to be used as backsheets for absorbent articles, it is preferred,

but not necessary, that the thin films are moisture-impervious having embossed surfaces and dull finishes. Typically, such thin backsheet films can have a thickness ranging from about 0.5 mils to about 2.0 mils and preferably about 1.0 mils to about 1.5 mils, but these limitations are not critical. Of course, when selecting a film thickness, the tearing strength of the film should not be overlooked so that the objectives of the present invention are not defeated.

A typical disposable diaper practicing the objectives of the present invention generally include a moisture-pervious inner frontsheet, an outer backsheet of the present invention which is preferabl moisture-impervious, an absorbent material or layer positioned between the outer backsheet and inner frontsheet and tape-tab fasteners secured to the disposable diaper. The moisture-pervious inner frontsheet forms the diaper inside surface for direction toward an infant and the outer backsheet forms a diaper outside surface for direction away fro the infant when the disposable -diaper is worn by the infant. To secure the tape-tab fasteners to the disposable diaper, the tape-tab fasteners generally speaking have anchoring ends which are secured to th disposable diaper and user ends which have on one si thereof a pressure-sensitive adhesive presenting tac surfaces facing in the same direction as the diaper

inside surface for contact with the backsheet when t diaper is fitted about an infant. Other absorbent articles such as bandages, surgical dressings or drapes and catamenial pads, on the other hand, generally comprise the same three elements as the disposable diaper absent the tape-tab fasteners. As an additional benefit, the anti-popoff technology improves the ability to assemble the.components of such absorbent products together, such as the glue, backsheets, etc.

Examples of the increase in tape adhesion between a thermoplastic sheet material of the presen invention will now be further illustrated with reference to the following examples.

Example I

A polyethylene in combination with anti-popoff substances are extruded to form the thermoplastic backsheets having increased tape adhesion for preventing the disposable diaper tape-ta fasteners from popping off the backsheets. For instance, about 5% of a conventional polypropylene an about 95% of a conventional polyethylene can be blended and extruded into thin films in the range of about 1.0 to about 1.5 mils which can then be used as backsheets. As indicated in Tables III and IV, the tape adhesion dramatically increases with a thermoplastic sheet material having about 5% polypropylene incorporated therein as when compared t a similar thermoplastic sheet material without polypropylene. It is also believed that any conventional polypropylene, such as shown in Tables I and II, will have the same effect on increasing the tape adhesion. More precisely, the amount of anti-popoff substance needed to increase tape adhesion depends of course upon the interaction of the pressure-sensitive adhesive of the tape-tab fasteners and the film. Another example of an increase in tape adhesion attributed to the use of an anti-popoff substance is described in Example II.

TABLE III

Film Comprising Film Compr 100% PE 95% PE and PP - 1 by weight by weig

Percent (%) increase in tape adhesion by using Method B 0 26%

Percent (%) increase in tape adhesion by using Method C 0 29%

Commercial tape-tab fastener 5

PE — conventional polyethylene

PP - 1— a conventional polypropylene

PP - 2— another conventional polypropylene

TABLE IV

Film Comprising Film Comp 100% PE 95% PE an PP - by weight by wei

Percent ( % ) increase in tape adhesion by using Method B 0 25%

Percent (%) increase in tape adhesion by using Method C 0 25%

Commercial tape-tab fastener

PE — conventional polyethylene

PP - 1— a conventional polypropylene

PP - 2— another conventional polypropylene

Exa ple II

The thermoplastic sheet materials and tape adhesions referred to in Tables I and II are prepared and determined as follows. A first concentrate is prepared which comprises 40 parts of a conventional thermoplstic lo density polyethylene, 10 parts of a conventional thermoplastic polypropylene and 50 parts titanium dioxide. Eight parts of the prepared concentrate are intimately blended with 100 parts of a conventional polyethylene to form a first pre-extrusion mixture. The first pre-extrusion mixture is then extruded in - accordance with the extrusion equipment and procedur described herein to generate a first thin thermoplastic film which comprises by weight about

0.75% polypropylene, about 3.70% titanium dioxide an about 95.55% polyethylene. The first extruded film has a thickness of about 1.5 mils, an embossed surface, a dull finish and is moisture-impervious. A second concentrate is prepared which comprises 35 parts of a conventional thermoplastic lo density polyethylene, 15 parts of a conventional thermoplastic polypropylene and 50 parts titanium dioxide. Nine parts of the prepared concentrate are intimately blended with 100 parts of a conventional polyethylene to form a second pre-extrusion mixture. The second pre-extrusion mixture is then extruded in accordance with the extrusion equipment and procedur

described herein to generate a second, thin thermoplastic film which comprises by weight about 1.3% polypropylene, 4.1% titanium dioxide and 94.6% polyethylene. The second extruded film has a thickness of about 1.5 mils, an embossed surface and dull finish and is moisture-impervious.

As indicated in Tables I and 1=1 , the tape adhesion for the first and second films when bonded with commercial diaper tape-tab fasteners 1 and 2 is expressed in percent (%) increase in tape adhesion o a polyethyelene film containing a polypropylene over similar polyethylene film free of a polypropylene. The 90° (Method A) and 180° (Method B) tape adhesion are determined as follows. Two 5-inch length and 1-inch width specimens of each commercial diaper tape-tab are applied to each film. Approximately 1 inch at the end of each tape-tab specimen is left fr (unbonded) . A roller is passed over each applied specimen once in a lengthwise direction. Care is exercised to ensure that no air bubbles are entrapped Following adhesion, the tests are conducted immediately. For determining the 90° (Method A) and 180° (Method B) tape adhesions, the free end of each specimen is double backed at an angle of 90° (Method A) or 180° (Method B) and 1 inch of the secured end o each tape-tab specimen is peeled from the film. The peeled end of the tape-tab specimen is then clamped into the lower jaw of the adhesion testing machine

manufactured by Instron Corporation and the free end of the tape-tab specimen is changed into the upper jaw. The lower jaw of the testing machine is operate at 12 inches per minute. After the lower jaw is started in motion, the values obtained for the first inch of the tape-tab specimens are disregarded. The average pull value obtained during the peeling of the next 2 inches is used and recorded as the percent increase in tape adhesion of the tape-tab specimens. The above as well as other suitable test procedures are described in the manual entitled "Test Methods fo Pressure Sensitive Tapes", 7th ed. , copyright 1976, - published by the Pressure Sensitive Tape Council whic is incorporated herein in its entirety by reference. in addition to the 90° (Method A) and 180° (Method B) angle test procedures for determining tape adhesion, there are other tests to develop the tape adhesion. For example, as already indicated herein and illustrated in Fig. 3 and Tables III and IV, the tape adhesion can be determined at angles between 90° and

180° (Method C) . Two different commerically availabl tape-tab fasteners are used in this example.

Example III

The percent increase in tape adhesion betw a polyethylene backsheet containing 5% polypropylene and a tape-tab fastener 5 described herein over the tape adhesion between a similar polyethylene backshe but containing no polypropylene and a similar tape-t fastener 5 is determined following an original fastening and four repeated refastenings of the tape-tab fastener 5 to the backsheets. The polyethylene backsheets containing polypropylene are- similar to those described and referred to in Exampl I and Tables III and IV. Under Methods B and C as described herein and referred to in Fig. 4, the tape adhesion is determined. Similar backsheets and tape-tab fasteners 5 are used for both Methods B and C.

Under Method B, Fig. 4 reports that there approximately a 33% increase in tape adhesion following the original fastening between a polyethylene backsheet containing 5% polypropylene a the tape-tab fastener 5 over the tape adhesion betwe a polyethylene backsheet free of polypropylene and a similar tape-tab fastener 5. Fig. 4 also demonstrat that there is a further increase in tape adhesion between the polyethylene backsheet containing 5% polypropylene and the tape-tab fastener 5 over the polyethylene backsheet free of polypropylene and the

tape-tab fastener 5 following four repeated refastenings.

Under Method C, Fig. 4 reports that there is approximately a 19% increase in tape adhesion following the _. original fastening- between a polyethylene backsheet containing 5% polypropylene and the tape-tab fas'tener 5 over the tape adhesion between a polyethylene backsheet free of polypropylene and a similar tape-tab fastener 5.. Fig. 4 also demonstrates that the percent increase in tape adhesion between the polyethylene backsheet containing 5% polypropylene and the tape-tab fastener 5 is substantially maintained ^" over the tape adhesion between the polyethylene backsheet free of polypropylene and the tape-tab fastener 5 following four repeated refastenings.

The present invention may, of course, be carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the present invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive and any changes coming within the meaning and equivalency range of the appended claims are to be embraced therein.