KR101143763B1 - Absorbent article having an aliphatic-aromatic copolyester film - Google Patents

Abstract

An absorbent article is disclosed that includes a laminated outer cover. The laminated outer cover comprises an aliphatic aromatic copolyester film comprising a filler material. Aliphatic aromatic copolyester films are substantially biodegradable and have suitable breathability, vapor mobility and tensile strength properties.

Absorbent Articles, Biodegradable, Aliphatic Aromatic Copolyester Films, Laminated Outer Covers, Breathable

Description

Absorbent article with aliphatic aromatic copolyester film {ABSORBENT ARTICLE HAVING AN ALIPHATIC-AROMATIC COPOLYESTER FILM}

The present invention relates to an absorbent article such as a diaper containing an outer cover comprising a substantially biodegradable film material. More specifically, the present invention relates to an absorbent article containing an outer cover made from a film material comprising an aliphatic aromatic copolyester material that exhibits improved biodegradability after use. When filled with a filler material such as calcium carbonate, the aliphatic aromatic copolyester film material is highly breathable and has good barrier and tensile strength properties.

People rely on disposable absorbent articles such as diapers to make their lives easier. Commercial diapers today are generally comfortable for wearers and have good barriers to leakage out of the diaper. Despite providing good barrier to liquids, many commercially available diapers pass water around through the diaper to reduce the amount of moisture retained in the skin and to reduce skin irritation and rashes that may be caused by skin overhydration. Let's do it. Many diapers include a laminated outer cover, often referred to as a breathable outer cover, to enable passage of vapor through and around the diaper while retaining liquid.

Generally, such breathable outer cover comprises a nonwoven outer facing layer bonded with an inner facing linear low density polyethylene layer. The polyethylene layer typically comprises calcium carbonate, which causes a series of openings in the polyethylene layer to be generated when the film is stretched prior to use in the product, ultimately allowing water vapor to pass through without passing the liquid.

While most diapers on the market today include an outer cover suitable for the purposes outlined above, one disadvantage to date is that the polyethylene used in the manufacture of the diaper, in particular one layer of the outer cover, is not substantially biodegradable. to be. Since diapers and other absorbent products are popular and a large number of these products are used annually, it may be advantageous to provide absorbent article components that exhibit improved biodegradability upon landfilling after use and disposal.

Summary of the Invention

The present invention relates to an absorbent article or article comprising a film with improved biodegradable properties. Films particularly useful as one component of the outer cover of an absorbent article include aliphatic aromatic copolyesters. The film also includes calcium carbonate or other suitable filler material such that when stretched, pores develop around the filler material. These pores allow water vapor to pass but not liquid. The film is also highly breathable and has good barrier properties and tensile strength properties.

In one embodiment, the film comprises copolyester and filler particles comprising three monomers, namely 1,4-butanediol, terephthalic acid, and adipic acid. The copolyester has a weight average molecular weight of about 90,000 to about 160,000 daltons and a number average molecular weight of about 35,000 to about 70,000 daltons, and includes a total of 40 mol% to about 60 mol% of acid comonomers.

Accordingly, the present invention relates to an absorbent article comprising a laminated outer cover. The laminated outer cover comprises a stretched biodegradable aliphatic aromatic copolyester film. The film comprises about 10 mol% to about 30 mol% of aromatic dicarboxylic acid or ester thereof, about 20 mol% to about 40 mol% of aliphatic dicarboxylic acid or ester thereof, and about 30 mol% to about 60 mol% of 2 And copolyester and filler particles comprising an alcohol. The weight average molecular weight of the copolyester is about 90,000 to about 160,000 daltons and the number average molecular weight of the copolyester is about 35,000 to about 70,000 daltons. The glass transition temperature of the copolyester is less than about 0 ° C.

In addition, the present invention relates to an absorbent article comprising a laminated outer cover. The laminated outer cover comprises a stretched biodegradable aliphatic aromatic copolyester film. The film comprises about 10 mol% to about 30 mol% terephthalic acid, about 20 mol% to about 40 mol% adipic acid, and about 30 mol% to about 60 mol% 1,4-butanediol And filler particles. The weight average molecular weight of the copolyester is about 90,000 to about 160,000 daltons and the number average molecular weight is about 35,000 to about 70,000 daltons. The glass transition temperature of the copolyester is less than about 0 ° C.

1 shows the geometric mean of machine direction and transverse strain data at break for calcium carbonate filler levels of various films.

FIG. 2 shows the geometric mean of machine direction and transverse modulus data for calcium carbonate filler levels of various films.

The present invention generally relates to disposable absorbent articles comprising aliphatic aromatic copolyester films. In one embodiment, an aliphatic aromatic copolyester film that can be used in combination with a spunbonded nonwoven to form a composite outer cover imparts several desired characteristics including high breathability and good barrier properties and tensile strength properties. Also included are filler materials. In addition, aliphatic aromatic copolyester films as described have improved biodegradable properties compared to conventional film materials such as linear low density polyethylene.

Although primarily described herein with respect to composite outer covers of absorbent articles, such as diapers, those skilled in the art, based on the present disclosure, appreciate that the aliphatic aromatic copolyester films described herein may be used in other parts of the absorbent article in addition to the outer cover. Will understand. For example, a stool retaining member, such as described in US Pat. No. 5,676,661 (Faulks et al.) May comprise the copolyester film described herein.

Additionally, although mainly described herein with respect to diapers, the aliphatic aromatic copolyester films described herein may also be used in a variety of other absorbent articles, including but not limited to training pants and adult incontinence garments. Those skilled in the art will understand based on the present disclosure. In addition, the aliphatic aromatic copolyester films described herein can also be used in connection with nonabsorbent articles. Suitable non-absorbent articles include, for example, surgical drape, surgical gowns, and the like.

As used herein, the term "precursor film" is meant to include films that have not been stretched prior to use and / or evaluation and analysis. This includes films containing filler materials, such as calcium carbonate, in which pores are formed around the calcium carbonate and water vapor is not stretched through the film.

As used herein, the term "extended film" is meant to include a film that is stretched to create pores around the filler material. These stretched films can be used directly in absorbent articles as water vapor will pass through them.

As used herein, the term “biodegradable” or “biodegradable polymer” refers to a polymer that can be readily degraded by biological means such as bacterial action, environmental heat, and / or moisture. When tested according to ASTM D6340-98, a biodegradable polymer is one that separates and / or degrades (oxidizes) at least about 80% after 180 days in a controlled compost environment as described in the procedure.

Typically, the outer cover of the diaper is a multilayer laminate or composite structure, such as a necked multilayer laminate structure. Such laminated composite structures provide the desired level of stretch as well as liquid impermeability and vapor permeability. The laminate structure typically includes an outward facing layer and an inward or body facing layer. Outward facing layers are generally made of vapor and liquid permeable nonwoven materials, and inward facing layers are generally made of liquid impermeable, vapor permeable materials. This combination allows vapor to permeate through the diaper while retaining the liquid in the diaper. The two layers are generally fixed together thermally or with a suitable lamination adhesive. Thermal bonding includes continuous or discontinuous bonding using a heating roll. Point bonding is an example of such a technique. In addition, thermal bonding should be understood to include various ultrasonic, microwave, and other bonding methods that generate heat in a nonwoven or film.

The liquid permeable outward facing layer may be any suitable material and generally provides a cloth-like texture. Suitable neckable materials for outward facing layers include nonwoven webs, woven fabrics, and knitted fabrics, such as those described in US Pat. No. 4,965,122 to Morman. Nonwoven fabrics or webs are formed from many processes, such as spunbonding processes, bonded carded web processes, meltblowing processes, and spunbonding spunlacing processes. The patent describes stretching a material, such as a nonwoven, in one direction such that the material is reversibly tapered or "necked" in the vertical direction. The inelastic neckable material is preferably formed from one or more members selected from inelastic polymer fibers and filaments. Such polymers include polyesters such as polylactic acid, polyhydroxy alkanoates, polyethylene terephthalates, polyolefins such as polyethylene and polypropylene, and polyamides such as nylon 6 and nylon 66 do. Preferred materials are spunbond polypropylenes. These fibers or filaments are used alone or in mixtures of two or more thereof. Suitable fibers to form the neckable material include bicomponent, multicomponent, and shaped polymeric fibers as well as natural and synthetic fibers.

For example, many polyolefin fibers include fiber-forming polypropylene, including Escorene PD 3445 polypropylene from Exxon Chemical Company and PF-304 from Himont Chemical Company. Available for manufacture. Polyethylenes, such as Asun 6811A linear low density polyethylene from Dow Chemical, are also suitable polymers. The nonwoven web layer may be bonded to impart a discontinuous bonding pattern of defined bonding surface area. If too much bonding portion is present on the neckable material, it will break before necking. If there is not enough bonding portion, the neckable material will fall off. Typically, the% bond portion is from about 5% to about 40% of the area of the neckable material.

One particular example of a suitable material from which an outward facing layer can be made is 0.4 osy (oz per square yard) or 14 gsm (grams per square meter) spunbond polypropylene nonwoven web that is neckable from about 35% to about 45%. Typically, the basis weight of a suitable nonwoven is less than about 30 gsm. In addition, the outward facing layer of the outer cover need not be liquid permeable, but is preferably cloth-like texture.

Another example of a suitable material from which an outward facing layer can be made is a polylactic acid spunbond such as manufactured by Unitika (Osaka, Japan) or Kanebo (Tokyo, Japan).

The liquid impermeable, vapor permeable inward facing layer is preferably made of elongated aliphatic aromatic copolyester containing film as described herein. The aliphatic aromatic copolyester film of the present invention comprises (1) aromatic dicarboxylic acids or esters thereof, aliphatic dicarboxylic acids or esters thereof, and copolyesters containing dihydric alcohols, and (2) filler particles. . Optionally, multifunctional branching agents can also be incorporated into the aliphatic aromatic copolyester films of the present invention.

In general, methods for preparing polyesters and especially aromatic aliphatic copolyesters are known in the art. Most commonly, aromatic dicarboxylic acids (represented by HOOC-Ar-COOH in the following scheme), aliphatic dicarboxylic acids (represented by HOOC-R-COOH in the scheme below), and diols (represented by HO-R'-OH in the scheme below) The monomer mixture comprising c) is reacted in the presence of a catalyst. Water is removed and under appropriate conditions copolyester is produced as shown in the scheme below (which may be a block or a random copolymer).

nHOOC-Ar-COOH + mHOOC-R-COOH + (n + m) HO-R'-OH →

-(OCArCO) _n- (OR'0) _n- (OCRCO) _m- (OR'0) _m- + (m + n) H ₂ 0

Alternative synthetic methods include using methyl esters instead of carboxylic acids. In this way methanol during the reaction is somewhat more volatile than water. Other synthetic methods are also known.

For the purposes of the present invention, when polyesters are mentioned to include various monomers, it is assumed that the starting materials were carboxylic acids and alcohols as provided in general in the above scheme. While it is understood that other synthetic schemes may utilize other types of monomers, reference to copolyesters comprising the carboxylic acids and alcohols mentioned is intended to define the final polymer and not the actual starting material. In addition, the detailed method of polymer synthesis is not critical as long as the desired properties of the polymer are achieved.

Any aromatic dicarboxylic acid known in the art can be used as the aromatic dicarboxylic acid monomer of the copolyesters of the films described herein. Useful aromatic dicarboxylic acids include lower alkyl (C ₁ -C ₆ ) esters of unsubstituted and substituted aromatic dicarboxylic acids and aromatic dicarboxylic acids. Examples of useful diacid residues include those derived from terephthalate, isophthalate, naphthalate, and bibenzoate. Specific examples of useful aromatic dicarboxylic acid components include terephthalic acid, dimethyl terephthalate, isophthalic acid, dimethyl isophthalate, 2,6-naphthalene dicarboxylic acid, dimethyl-2,6-naphthalate, 2,7-naphthalenedicarboxylic acid, dimethyl-2 , 7-naphthalate, 3,4'-diphenyl ether dicarboxylic acid, dimethyl-3,4'-diphenyl ether dicarboxylate, 4,4'-diphenyl ether dicarboxylic acid, dimethyl-4,4'- Diphenyl ether dicarboxylate, 3,4'-diphenyl sulfide dicarboxylic acid, dimethyl-3,4'-diphenyl sulfide dicarboxylate, 4,4'-diphenyl sulfide dicarboxylic acid, dimethyl-4,4 '-Diphenyl sulfide dicarboxylate, 3,4'-diphenyl sulfone dicarboxylic acid, dimethyl-3,4'-diphenyl sulfone dicarboxylate, 4,4'-diphenyl sulfone dicarboxylic acid, dimethyl-4 , 4'-diphenyl sulfone dicarboxylate, 3,4'-benzophenonedicarboxylic acid, dimethyl-3,4'-benzo Non-dicarboxylate, 4,4'-benzophenonedicarboxylic acid, dimethyl-4,4'-benzophenonedicarboxylate, 1,4-naphthalene dicarboxylic acid, dimethyl-1,4-naphthalate, 4,4 '-Methylene bis (benzoic acid), dimethyl-4,4'-methylenebis (benzoate) and the like and mixtures of two or more thereof. Preferably, the aromatic dicarboxylic acid component is derived from terephthalic acid, dimethyl terephthalate, isophthalic acid, dimethyl isophthalate, 2,6-naphthalene dicarboxylic acid, dimethyl-2,6-naphthalate, or a mixture of two or more thereof. do. Carboxylic acid chlorides or anhydrides of these monomers may also be suitable.

The aromatic dicarboxylic acid is present in the aliphatic aromatic copolyester in an amount of about 10 mol% to about 30 mol%, optionally about 15 mol% to about 25 mol%, and optionally about 17.5 mol% to about 22.5 mol%.

Any aliphatic dicarboxylic acid known in the art can be used as the aliphatic dicarboxylic acid monomer component of the copolyesters of the films described herein. Useful aliphatic dicarboxylic acid components include, preferably, unsubstituted or substituted, linear, branched, or cyclic aliphatic dicarboxylic acids having 2 to 36 carbon atoms, and lower alkyl esters thereof. Examples of useful aliphatic dicarboxylic acid components are oxalic acid, dimethyl oxalate, malonic acid, dimethyl malonate, succinic acid, dimethyl succinate, methyl succinic acid, glutaric acid, dimethyl glutarate, 2-methylglutaric acid, 3-methylglutaric acid. Tartaric acid, adipic acid, dimethyl adipate, 3-methyladipic acid, 2,2,5,5-tetramethylhexanediic acid, pimelic acid, suberic acid, azelaic acid, dimethyl azelate, sebacic acid, 1 , 11-Undecanedicarboxylic acid, 1,10-decanedicarboxylic acid, undecanediic acid, 1,12-dodecanedicarboxylic acid, hexadecanediic acid, docosanediic acid, tetracosanediic acid, dimer acid, 1,4-cyclohexane Dicarboxylic acid, dimethyl-1,4-cyclohexanedicarboxylate, 1,3-cyclohexanedicarboxylic acid, dimethyl-1,3-cyclohexanedicarboxylate, 1,1-cyclohexanediacetic acid and the like and two Or mixtures thereof. Carboxylic acid chlorides or anhydrides may also be suitable. Preferred aliphatic acids or esters include succinic acid, dimethyl succinate, glutaric acid, dimethyl glutarate, adipic acid, dimethyl adipate, and dimer acids.

Aliphatic dicarboxylic acids are present in aliphatic aromatic copolyesters in amounts of about 20 mol% to about 40 mol%, optionally about 25 mol% to about 35 mol%, and optionally about 27.5 mol% to about 32.5 mol%.

Any dihydric alcohol, glycol, or diol known in the art can be used as the dihydric alcohol component of the aliphatic aromatic copolyesters of the films of the present invention. Examples include, for example, unsubstituted or substituted, straight chain, branched, cyclic aliphatic, aliphatic aromatic, or aromatic diols having 2 to 36 carbon atoms and poly (alkyl having a molecular weight of preferably about 250 to about 4,000. Lene ether) diols. Specific examples of useful diol components include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecane Diol, 1,14-tetradecanediol, 1,16-hexadecanediol, 4,8-bis (hydroxymethyl) -tricyclo [5.2.1.0/2.6] decane, 1,4-cyclohexanedimethanol, di (Ethylene glycol), tri (ethylene glycol), poly (ethylene oxide) glycol, poly (butylene ether) glycol, isosorbide and the like and mixtures of two or more thereof. Preferred dihydric alcohols include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, and poly (ethylene oxide) glycol.

The dihydric alcohol is present in the aliphatic aromatic copolyester in an amount of about 30 mol% to about 60 mol%, optionally about 45 mol% to about 55 mol%, and optionally about 47.5 mol% to about 52.5 mol%.

The aliphatic aromatic copolyester component of the films described herein may comprise any multifunctional branching agent, such as three or more carboxylic acid functional groups, or any substance having a hydroxy functional group or all of these functional groups. Can be. Specific examples of useful polyfunctional branching agents components include 1,2,4-benzenetricarboxylic acid (trimelitic acid), trimethyl-1,2,4-benzenetricarboxylate, 1,2,4-benzenetricarboxylic anhydride ( Trimellitic anhydride), 1,3,5-benzenetricarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid), 1,2,4,5-benzenetetracarboxylic dianhydride (pyromel Lithic anhydride), 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, citric acid, tetrahydrofuran-2,3,4,5- Tetracarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid, pentaerythritol, 2- (hydroxymethyl) -1,3-propanediol, 2,2-bis (hydroxymethyl) propionic acid, and the like or two or its It includes a mixture of the above. Multifunctional branching agents can be included where higher resin melt viscosity is required for a particular end use. Excess portions of the multifunctional group (ie, two or more functional groups) can lead to the formation of a gel portion or an insoluble crosslinking material. The total amount of multifunctional branching agent may be less than about 10% of the total monomer composition. Or in the alternative, the multifunctional branching agent may be less than about 3%, or less than about 1%.

In one embodiment of the invention, the total amount of acid comonomers present in the aliphatic aromatic copolyester component of the films described herein is about 40 mol% to about 60 mol%. That is, the molar amount of aromatic dicarboxylic acid plus the molar amount of aliphatic dicarboxylic acid present in the aliphatic aromatic copolyester is from about 40 mol% to about 60 mol%. Preferably, the total amount of acid comonomers present in the copolyester is from about 45 mol% to about 55 mol%, even more preferably from about 47.5 mol% to about 52.5 mol%.

The total amount of acid comonomer present in the aliphatic aromatic copolyester component of the films described herein affects the adhesion properties between the aliphatic aromatic copolyester and the filler material component of the film, which is described below. In order to make the film suitable for use in absorbent articles, it is generally desirable to have low adhesion between the filler material and the copolyester. If too much acid comonomer is present in the copolyester, the adhesion to the filler material is too high. And when the film is stretched, the filler material does not work properly and does not effectively create pores around the filler material. This results in a film with insufficient vapor permeability.

The aliphatic aromatic copolyester component of the films described herein has a weight average molecular weight and a number average molecular weight such that the copolyester has a suitable tensile strength. If the molecular weight value is too small, the copolyester will be too sticky and the tensile strength will be too low. If the molecular weight value is too large, various processing problems arise, such as the need for elevated temperatures to handle the increased viscosity. Suitable weight average molecular weight of the copolyester is from about 90,000 to about 160,000 daltons, preferably from about 100,000 to about 130,000 daltons, more preferably from about 105,000 to about 120,000 daltons. Suitable number average molecular weights of the copolyesters are from about 35,000 to about 70,000 daltons, more preferably from about 40,000 to about 60,000 daltons, more preferably from about 42,000 to about 50,000 daltons.

The aliphatic aromatic copolyester films of the present invention generally have a thickness suitable for use in absorbent articles such as diapers. Typically, the thickness of the film will be less than about 250 μm, preferably from about 2.5 μm to about 130 μm. The thickness of the standard film useful for a diaper can be, for example, from about 10 μm to about 25 μm. In some embodiments, the use of a film having a thickness of about 50 μm may be desirable.

The copolyesters described herein for use in the films of the present invention have a glass transition temperature such that the copolyesters have flexible characteristics suitable for use in the film. As used herein, "glass transition temperature" means the temperature at which the polymer becomes hard and brittle, such as glass. In the case of the copolyesters described herein, their glass transition temperatures are preferably less than about 0 ° C, optionally less than about -10 ° C. When the glass transition temperature is below these values, the copolyester has properties suitable for use in the absorbent articles described herein.

The aliphatic aromatic copolyester films of the present invention have a water vapor transmission rate that is suitable for the film to pass a substantial amount of water vapor to mitigate the possibility of skin excess. Films of the invention can be made substantially vapor permeable through the addition of filler particles or materials during the manufacture of the film. During manufacture, the filler material is mixed with the polymer prior to casting the polymer into the film. Once cast, the film is stretched to produce fine pores in the film around the filler particles. These pores permeate the vapor but do not pass a substantial amount of the liquid.

Filler particles may comprise any suitable inorganic or organic filler. The filler particles are preferably small in order to maximize the penetration of the vapor through the pores. In general, the average particle diameter of the filler particles should be about 0.1-10.0 μm, optionally about 0.5-5.0 μm, and optionally about 1.5-3.0 μm. Organic filler examples include starches such as thermoplastic starch or pregelatinized starch, microcrystalline cellulose, and polymeric microbeads. Other suitable fillers are calcium carbonate, non-swellable clay, silica, alumina, barium sulfate, sodium carbonate, talc, magnesium sulfate, titanium dioxide, zeolite, aluminum sulfate, diatomaceous earth, magnesium sulfate, magnesium carbonate, barium carbonate, kaolin, mica, carbon, Calcium oxide, magnesium oxide, aluminum hydroxide and polymer particles. Calcium carbonate is the presently preferred filler material.

Filler particles may optionally be coated with trace amounts (eg, up to 2% by weight) of fatty acids or other materials so that they are readily dispersed in the polymer matrix prior to casting. Suitable fatty acids include, but are not limited to, longer chain fatty acids such as stearic acid, or behenic acid. The amount of filler particles in the film is from about 30% to about 80% (by weight of film and filler particles), optionally from about 40% to about 70% (by weight of film and filler particles), and optionally from about 50% to About 65% (by weight of film and filler particles), and optionally about 50% to about 55% (by weight of film and filler particles).

The filler particles may or may not be microporous. Microporosity refers to materials in which the pores are generally about 2 GPa to about 50 GPa and form continuously interconnected void spaces or networks. The shape of the filler particles may generally be spherical or circular. Other embodiments include sheet metal-like, needle-like, or irregular shapes, points, or sharp edges.

In some embodiments of the present invention, the water vapor permeability of the stretched film as described herein is from about 2000g / m ² / day or more, optionally from about 5000 g / m ² / day or more, optionally from about 10,000 g / m ² / day And optionally 25,000 g / m ² / day. At this level, the film passes a sufficient amount of water vapor to protect the skin from excess moisture.

In addition to a suitable water vapor transmission rate, it is also desirable for the stretched film described herein to withstand hydrostatic pressure such that a substantial amount of liquid water does not pass through the film when pressure is applied. In general, it is desirable for the film to withstand hydrostatic pressure of at least about 60 mbar, optionally at least about 80 mbar, optionally at least about 120 mbar, and optionally at least about 180 mbar without passing liquid water.

In addition to suitable water vapor transmission rate and suitable resistance to hydrostatic pressure, it is also preferred that the films described herein have a suitable elastic modulus. Tensile properties of the films disclosed herein are described in "Standard Test Method for Tensile Properties of Plastics" ASTM D 938-99 (published by the American Material Testing Association, West Conshohoken, Pennsylvania, USA). ) Can be determined by one skilled in the art. The procedure is that the break stress is the tensile stress at the elongation at break (i.e. the elongation at the time of sample break), the yield stress is the tensile stress at the first point of the stress-strain curve where the strain increases without increasing the stress, and the elastic modulus Indicates the ratio (nominal) of the stress to the corresponding strain below the proportional limit of the material.

The precursor film preferably has an elastic modulus ratio suitable for characterizing the desired adhesion between the filler particles and the film. As used herein, the term "modulus ratio" means the elastic modulus of the filled precursor film divided by the elastic modulus of the unfilled film. For precursor films comprising about 50% filler material, the modulus ratio is preferably about 0.5 to about 3.5, optionally about 0.75 to about 3.25, and optionally about 1.0 to about 3.0. For precursor films comprising about 55% filler material, the modulus ratio is about 0.45 to about 4.25, optionally about 0.75 to about 3.75, and optionally about 1.0 to about 3.5. Within this ratio, the film has a desirable elastic modulus to provide a desirable adhesion ratio between the film and the filler particles.

In addition, the precursor film preferably has suitable elongation characteristics. That is, the precursor film can be stretched to a sufficient amount prior to fracture to achieve the desired film thickness and breathability level. The elongation measurement of the film includes percent strain at break, break stress (MPa) and yield stress (MPa). For precursor films comprising about 50% filler material, the film may be stretched in the machine direction and may be from about 50% strain to about 1000% strain, optionally from about 300% strain to about 1000% strain, and optionally before breaking. Is preferably about 450% strain to about 1000% strain. As used herein, “strain” means subtracted 1 from the ratio of the length of the stretched film to the length of the precursor film, which is typically reported in%.

For precursor films comprising about 55% filler material, the film may be stretched in the machine direction and may be from about 50% to about 1000% strain, optionally from about 75% to about 1000% strain, and optionally before breaking. It is preferred that about 250% to about 1000% strain be possible.

It is also advantageous for the precursor film to have a suitable draw ratio in the machine direction. As used herein, "draw ratio" means the length of the stretched film divided by the length of the unstretched film. In one embodiment, the draw ratio of the precursor films described herein is at least about 2.5 to about 10, optionally about 3.5 to about 10, and optionally about 4.5 to about 10.

For precursor films comprising about 50% filler material, the film may be stretched in the transverse direction and may be from about 50% strain to about 1000% strain, optionally from about 300% strain to about 1000% strain, and optionally before breaking. It is desirable that they may not be broken from about 450% strain to about 1000% strain. For precursor films comprising about 55% filler material, the film may be stretched in the transverse direction and may be about 50% to about 1000% strain, optionally about 250% to about 1000% strain, and optionally before breaking It is desirable that they may not be broken from about 350% strain to about 1000% strain.

For precursor films comprising about 50-55% filler material, the film can be stretched in the machine direction and the break stress is about 4 to about 30 MPa, optionally about 6 to about 20 MPa, and optionally about 8 to Preferably, it may be about 15 MPa. For precursor films comprising about 50 to about 55% filler material, the film can be stretched in the machine direction and the yield stress is about 4 to about 16 MPa, optionally about 6 to about 14 MPa, and optionally about 8 It is also preferred that it can be from about 10 MPa. As those skilled in the art can understand based on the disclosure herein, the films described herein can be stretched by any method known in the art. For example, the film can be stretched by blowing, or by using a tenter hook, or by using a parallax speed on the roller.

For stretched films, it is preferred that the elastic modulus of the film is about 50 to about 250 MPa, optionally about 70 to about 150 MPa, and optionally about 80 to about 100 MPa. With regard to elongation, it is preferred that the stretched film can be stretched in the machine direction with about 15 to about 100% strain, optionally about 20 to about 60% strain, and optionally about 30 to about 50% strain before fracture. . It is also preferred that the stretched film can be stretched transversely with about 150 to about 500% strain, optionally about 175 to about 400% strain, and optionally about 200 to about 300% strain before fracture. In addition, when elongated in the machine direction, the break stress of the stretched film is preferably about 10 to about 50 MPa, optionally about 15 to about 40 MPa, and optionally about 25 to about 35 MPa.

As mentioned above, the aliphatic aromatic copolyesters described herein can be prepared from aliphatic dicarboxylic acids, aromatic dicarboxylic acids, and divalent acid monomers using any conventional process known to those skilled in the art. For example, copolyesters can be prepared using conventional polycondensation techniques, or conventional melt polymerization methods. In addition, aliphatic aromatic copolyesters are obtained commercially from BASF (BASF, Mount Olive, NJ), Ire Chemical (Seoul, Korea) and Eastman Chemical (Kingsport, Tennessee, USA). Can be.

Films comprising the copolyester and filler particles described herein and suitable for use in the absorbent articles described herein can be prepared using any conventional film forming technique, including extrusion casting and melt blowing. Extrusion casting techniques can be used with heat fixation after film annealing, film stretching, and / or stretching operations.

In one embodiment, the cast rolls during the film casting operation optionally have a roll surface temperature of about 20 ° C to about 70 ° C, optionally about 30 ° C to about 60 ° C and optionally about 45 ° C to about 55 ° C. After the film is cast on a cast roll, the film can be cooled and annealed at about 40 ° C. to about 60 ° C. This cooling and annealing occurs when the film is transported under low tension (on a series of rollers, conveyor belts, air conveyors, etc.). In this document, "low tension" indicates that the film is stretched less than 100%, optionally less than 25%, or less than 10% when transported. This portion of the film making apparatus that extends from the cast roll to the stretching operation is called a casting line.

The casting line length is about 5 m to about 50 m, optionally about 10 m to about 30 m. Longer line lengths can lead to longer residence times for film fixation and annealing before the film is introduced into the stretching operation. Longer residence times will improve film tensile properties such as strength, stretch, and other properties useful for stretching operations.

In the stretching operation, the film is preferably stretched at a temperature of about 15 ° C to about 50 ° C, optionally about 25 ° C to about 40 ° C, and optionally about 30 ° C to about 40 ° C. Cooling elongation can enhance pore formation around the filler particles, but can limit film extensibility. Optionally, the film is stretched in two zones, optionally heated in the range of about 30 ° C. to about 50 ° C. between the stretch zones. A single extension or band or multiple bands can be used. The film can be stretched uniaxially, biaxially, or in both uniaxial and biaxial (in different times). Uniaxial stretching may be in the machine direction, in the transverse direction, or in the oblique direction.

The stretch or stretch ratio during stretch operation is about 2.5 to about 10. For example, the linear velocity of the film from the stretching operation is 2.5 to 10 times the precursor film rate introduced into the stretching operation. Optionally, the stretch or stretch ratio is about 3.5 to about 7.

After stretching, the film is optionally heat fixed to stabilize the stretched film. Heat fixation may be achieved at about 40 ° C. to about 80 ° C., and optionally at about 50 ° C. to about 70 ° C. Heat fixation operations can reduce shrinkage of the stretched film and can improve film properties and breathability. Any technique known in the art for heat fixation can be used, including heated rolls and oven fixation. Additional treatments such as surface treatment, UV treatment, sonication, and plasma treatment can be applied to improve the stretched film properties.

Example  One

In this example, an aliphatic aromatic copolyester film was produced using two commercially available aliphatic aromatic copolyester resins as starting materials. The first group of films was made without any filler material, and the second group of films was made with calcium carbonate filler materials of varying content (% by weight of filler based on the total weight of the film and filler). One group of filled and unfilled films was made using Ecoflex F BX 7011 aliphatic aromatic copolyester (BASF), and one group of films was EnPol G8060M (Ere Chemical) aliphatic aromatic co Prepared using polyester.

Prior to extruding the film from the aliphatic aromatic copolyester, a group of Ecoflex copolyester films and a group of Enpol copolyester films were transferred to a WSKER & Pfleiderer (Ramsey, NJ) ZSK-30 biaxial comb A compounding extruder was used to blend separately with Omya (Proctor, Vermont, USA) 2sst 2 micron calcium carbonate filler material. Blends of calcium carbonate filler material and each resin (molten form) were prepared at filler levels of 40 wt% (based on the total weight of the film and filler), 50 wt%, 55 wt%, 60 wt%, and 65 wt%. .

After blending the resin with the filler material, the films of each blend were extruded. The film was extruded using a Rheocord 90 benchtop twin screw extruder with an HAAKE (Thermo Electron Corporation, Woburn, Mass.) With an 8 inch die. The extruder had three temperature zones, a melt pump of controlled temperature, and a die of controlled temperature. The unfilled film comprising each copolyester was also extruded.

Temperature profiles used to cast Ecoflex copolyesters into films were 160 ° C, 170 ° C, 170 ° C (extruder temperature), 170 ° C (melt pump temperature), and 160 ° C (die temperature). The temperature profiles used to cast the enpol copolyesters into films were 170 ° C, 180 ° C, 180 ° C (extruder temperature), 180 ° C (melt pump temperature), and 180 ° C (die temperature). The temperature profile was chosen to achieve a viscosity suitable for handling of the molten polymer. Both packed and unfilled films with a thickness of about 15 μm to about 50 μm were extruded.

Example  2

In this example, the tensile strength test was performed on various aliphatic aromatic copolyester precursor films prepared in Example 1. Each film to be tested was cut into a strip of film 3 mm wide by 50 mm long. Tensile tests were performed according to ADTM D-638 using dog bone shape, 0.7 inch (18 mm) gauge length, and transverse head speed of 5 inches (127 mm) per minute. The film was stretched under these conditions until the film broke.

(1) 0% calcium carbonate, 25 μm, (2) 40% calcium carbonate, 50 μm, (3) 50% calcium carbonate, 50 μm, (4) 55% calcium carbonate, 50 μm, (5) 60% carbonic acid Calcium, 50 μm Ecoflex substrate and Enpol substrate films were stretched and tested in the machine and transverse directions. In addition, linear low density polyethylene was tested for comparison purposes. The results are shown in Tables 1-5 below.

Tensile Strength Properties of Linear Low Density Polyethylene Films LLPDE Machine direction Transverse machine direction Thickness (㎛) 25 25 % Deformation at break 700 747 Peak stress (MPa) 31 31 Stress at Yield (MPa) 8 9 Modulus (MPa) 102 105

Mechanical Directional Tensile Properties of Copolyester Precursor Films Ecoflex Ecoflex / CaCO ₃ Ecoflex / CaCO ₃ Ecoflex / CaCO ₃ Ecoflex / CaCO ₃ Do not charge 60/40 50/50 45/55 40/60 MD MD MD MD MD Thickness (㎛) 25 50 50 50 50 % Deformation at break 609 561 470 259 48 Peak stress (MPa) 36 18 11 9 12 Stress at Yield (MPa) 8 8 9 9 12 Modulus (MPa) 60 153 177 192 277

Transverse Machine Directional Tensile Properties of Precursor Films Ecoflex Ecoflex / CaCO ₃ Ecoflex / CaCO ₃ Ecoflex / CaCO ₃ Ecoflex / CaCO ₃ Do not charge 60/40 50/50 45/55 40/60 CD CD CD CD CD Thickness (㎛) 25 50 50 50 50 % Deformation at break 945 696 484 374 45 Peak stress (MPa) 40 16 10 8 10 Stress at Yield (MPa) 9 8 9 8 10 Modulus (MPa) 72 155 183 219 233

Mechanical Directional Tensile Properties of Copolyester Precursor Films Enpol Enpol / CaCO ₃ Enpol / CaCO ₃ Enpol / CaCO ₃ Enpol / CaCO ₃ Do not charge 60/40 55/45 50/50 45/55 MD MD MD MD MD Thickness (㎛) 25 50 50 50 50 % Deformation at break 715 378 330 231 8 Peak stress (MPa) 32 17 13 12 14 Stress at Yield (MPa) 7 11 13 12 14 Modulus (MPa) 78 210 237 227 352

Transverse Machine Directional Tensile Properties of Precursor Films Enpol Enpol / CaCO ₃ Enpol / CaCO ₃ Enpol / CaCO ₃ Enpol / CaCO ₃ Do not charge 60/40 50/50 45/55 40/60 CD CD CD CD CD Thickness (㎛) 25 50 50 50 50 % Deformation at break 889 474 203 136 7 Peak stress (MPa) 36 14 12 11 12 Stress at Yield (MPa) 14 11 12 11 12 Modulus (MPa) 86 210 237 262 332

1 and 2 are derived from the data of Tables 2-5. 1 shows the geometric mean of MD and CD modification data at break for calcium carbonate filler levels. FIG. 2 shows the geometric mean of MD and CD modulus data for calcium carbonate filler levels. The geometric mean is calculated by taking the square root of the product of the machine direction data and the transverse machine direction data.

The data in Tables 2-5 and FIGS. 1 and 2 show that the strains at break for unfilled (ie 0% calcium carbonate) ecoplexes and enpols are very close at break. Unfilled films also have a similar modulus. However, as filler levels increase, the values for Ecoflex and Enpol films will vary. When considering a filler containing film of 40% or more, the enpol base film is stronger than the ecoflex base film as evidenced by the higher modulus for the enpol base film and the lower strain at break compared to the ecoflex base film. This difference indicates that filler particles adhered to the enpol base film are more strongly bonded than filler particles adhered to the ecoplex substrate film.

It is desirable that the filler particles do not adhere too strongly to the copolyester. Weaker adhesion allows the film to stretch better without breaking. In addition, weaker adhesion results in better peeling (separation) of the filler particles from the polymer as the film is stretched. This separation provides voids in the film, enhancing vapor permeability. Such voids also tend to produce low density films.

Example  3

In this example, the elongated extruded Ecoflex substrate and Enpol substrate precursor films in Example 1 were stretched to produce an elongated film so as to further evaluate the hydrohead pressure, water vapor transmission rate, and tensile strength of the film. Thereby creating pores around the calcium carbonate filler material. The films were stretched to create pores prior to further analysis to test the films when they were used in commercial embodiments. That is, the filled film extruded in Example 1 will first be stretched according to the procedure of this example before being used in the absorbent article, and this stretching creates pores of the film through which vapor is permeated.

Each film was cut into sheets measured about 18.0 cm wide by about 10.0 cm long. Each film was then stretched at a speed of 840 mm / min to about 470% (deformation) of its original length, resulting in 2200% / min elongation and 350% elongation. All Ecoflex films have been successfully stretched to a calcium carbonate concentration of 60%. Enpol films could not be successfully stretched to the same extent at calcium carbonate concentrations above 40% because they broke at higher calcium carbonate loading levels. Excessive adhesion of the copolyester to the filler particles was assumed to make the endurance of the enpole film less durable than the ecoflex film.

In order to account for the difference in adhesion between the two films, an analytical operation (gel permeation chromatography for molecular weight determination) was performed on the Echoplex and Enpol copolyester. It was determined that Enpol resin (119,300 Daltons) had a higher weight average molecular weight when compared to Ecoflex resin (109,850 Daltons). It was determined that Enpol resin (43,800 Daltons) also had a lower number average molecular weight when compared to Ecoflex resin (46,700 Daltons). It was also determined that Enpol resin (57 mol%) had a higher total amount of acid monomer content when compared to Ecoflex (51 mol%). The combination of differences in molecular weight and differences in total acid monomer content is believed to have resulted in an increased degree of tack with which the enpole film does not delaminate much compared to the ecoflex film.

Example  4

In this example, the resistance to hydrostatic pressure of various films stretched in accordance with Example 3 was evaluated. Resistance of the material to liquid penetration was measured by hydrostatic pressure. The resistance to hydrostatic pressure of various films is ASTM Standard Test Method For Coated Fabrics, except that the dial is read when the third drop is observed in paragraph 40.4.4. ), Designation D751, "Hydrostatic Resistance Procedure A-Mullen Type Tester". All films were stretched in the machine direction.

Film comprising Ecoplex, elongated according to Example 3, namely Ecoplex (25 μm) with 55% calcium carbonate, Ecoplex (25 μm) with 50% calcium carbonate, and 40% calcium carbonate ECOplex (20 μm) having was evaluated. In addition, the film containing the enpol, e.g., an enpol having a calcium carbonate of 40% (23 mu m), which was stretched according to Example 3, was evaluated. Hydrostatic pressure analysis results are shown in Table 6.

Hydrostatic pressure Base material resin % CaCO ₃ Thickness (㎛) Elongation direction Pressure at Break (Mbar) Ecoflex 55 25 MD 100 Ecoflex 50 25 MD 100 Ecoflex 40 20 MD 148 Enpol 40 23 MD 104

As the data in Table 6 show, all the films tested had high hydrostatic resistance values, indicating that during use all films would be resistant to the passage of water droplets. In particular, the value of Ecoflex (20 μm) containing 40% calcium carbonate was 148.00, indicating that the resistance to the passage of liquid would be large.

Example  5

In the present Example, the water vapor transmission rate of the various films extended | stretched according to Example 3 was evaluated. Water vapor transmission rate measures the ability of water vapor to penetrate a film. The water vapor transmission rate of the various films was determined using ASTM F-1249 using a Permatran 100 K analyzer (MOCON, Minneapolis, Minn.). The film was stretched in the machine direction or transverse direction as mentioned above.

Films comprising Ecoflex, ie Ecoflex with 55% calcium carbonate (19 μm machine direction), Ecoplex with 55% calcium carbonate (25 μm machine direction), Ecoflex with 55% calcium carbonate ( 25 μm transverse direction), Ecoplex with 50% calcium carbonate (23 μm machine direction), Ecoplex with 50% calcium carbonate (19 μm machine direction), Ecoplex with 40% calcium carbonate (17 μm Machine orientation), and Ecoflex (22 μm machine orientation) with 40% calcium carbonate. A film comprising an enpol, i.e., an enpole with 40% calcium carbonate (18 μm machine direction), an enpole with 40% calcium carbonate (20 μm transverse direction), an enpole with 40% calcium carbonate (15 μm transverse direction) ), An enpol having 40% calcium carbonate (25 μm machine direction), and an enpol having 40% calcium carbonate (20 μm machine direction) were evaluated. Water vapor permeability analysis results are shown in Table 7.

All ecoflex films were made from a resin having a temperature of about 175 ° C. when exiting the die during casting. Enpols tested at 40% calcium carbonate were cast at about 160 ° C.

Water vapor transmission rate Base material resin % CaCO ₃ Thickness (㎛) Elongation direction g / m ² / day Ecoflex 55 19 MD 21,207 Ecoflex 55 25 MD 19,763 Ecoflex 55 25 CD 16,405 Ecoflex 50 23 MD 15.660 Ecoflex 50 19 MD 13,995 Ecoflex 40 17 MD 3498 Ecoflex 40 22 MD 3091 Enpol 40 18 MD 3371 Enpol 40 20 CD 2918 Enpol 40 15 CD 2593 Enpol 40 23 MD 2348 Enpol 40 20 MD 2322

The data in Table 7 demonstrate that films with higher filler loading levels tend to have higher water vapor transmission rates than films with lower filler loadings.

Example  6

In this example, the tensile strength of various stretched films prepared according to Example 3 was used to evaluate modulus, percent strain at break, peak stress, and peak load using the same test procedure as described in Example 2. The film was stretched in the machine direction (Table 8) and in the transverse machine direction (Table 9). The results are shown in Tables 8 and 9.

Tensile properties of stretched breathable film; Film stretched to MD and tested for MD LLPDE Enpol with MD / CaCO ₃ 60/40 Ecoflex / CaCO ₃ 45/55 Extended with MD MD MD MD Thickness (㎛) 23 23 25 % Deformation at break 72 47 35 Peak stress (MPa) 34 41 33 Peak load (gf) 234 287 253 Modulus (MPa) 322 125 85

Tensile properties of stretched breathable film; Film stretched to MD and tested for CD LLPDE Enpol with MD / CaCO ₃ 60/40 Ecoflex / CaCO ₃ 45/55 Extended with MD CD CD CD Thickness (㎛) 23 23 25 % Deformation at break 187 460 222 Peak stress (MPa) 3 4 2 Peak load (gf) 21 28 14 Modulus (MPa) 73 88 12

As the data in the table show, both the enpol and ecoflex substrate films, once stretched, have similar properties to LLPDE.

It is to be understood that the description of the above embodiments given for the purpose of explanation should not be construed as limiting the scope of the invention. Although only some exemplary embodiments of the invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without substantially departing from the novel teachings and advantages of the invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined by the appended claims and their equivalents. In addition, although many embodiments may be envisioned that do not achieve all the advantages of some embodiments, particularly preferred embodiments, the absence of particular advantages should not be construed as necessarily meaning that such embodiments are outside the scope of the present invention. Will recognize.

Claims (20)

A laminated outer cover comprising an elongated biodegradable aliphatic aromatic copolyester film comprising copolyester and filler particles, The copolyester comprises 10 mol% to 30 mol% of aromatic dicarboxylic acid or ester thereof, 20 mol% to 40 mol% aliphatic dicarboxylic acid or ester thereof, 30 mol% to 60 mol% dihydric alcohol. And a weight average molecular weight of 90,000 to 160,000 Daltons, a number average molecular weight of 35,000 to 70,000 Daltons, and a glass transition temperature of less than 0 ° C. The absorbent article of claim 1 wherein the filler particles are present in the film in an amount of 30% (by weight of the film and filler particles) to 80% (by weight of film and filler particles). The method of claim 1, wherein the filler particles are calcium carbonate, non-swellable clay, silica, alumina, barium sulfate, sodium carbonate, talc, magnesium sulfate, titanium dioxide, zeolite, aluminum sulfate, diatomaceous earth, magnesium sulfate, magnesium carbonate, barium carbonate, kaolin , Mica, carbon, calcium oxide, magnesium oxide, aluminum hydroxide and polymer particles. The absorbent article of claim 1 wherein the aromatic dicarboxylic acid or ester thereof is selected from the group consisting of unsubstituted and substituted aromatic dicarboxylic acids and C ₁ -C ₆ esters of aromatic dicarboxylic acids. The method of claim 1, wherein the aliphatic dicarboxylic acid or ester thereof is oxalic acid, dimethyl oxalate, malonic acid, dimethyl malonate, succinic acid, dimethyl succinate, methyl succinic acid, glutaric acid, dimethyl glutarate, 2-methylglutar Acid, 3-methylglutaric acid, adipic acid, dimethyl adipate, 3-methyladipic acid, 2,2,5,5-tetramethylhexanediic acid, pimelic acid, suberic acid, azelaic acid, dimethyl azelate , Sebacic acid, 1,11-undecandicarboxylic acid, 1,10-decanedicarboxylic acid, undecanediic acid, 1,12-dodecanedicarboxylic acid, hexadecanediic acid, docosanedic acid, tetracoic acid, dimer acid, 1,4-cyclohexanedicarboxylic acid, dimethyl-1,4-cyclohexanedicarboxylate, 1,3-cyclohexanedicarboxylic acid, dimethyl-1,3-cyclohexanedicarboxylate, 1,1-cyclohexane Diacetic acid, and mixtures of two or more thereof To the absorbent article. The poly (alkylene ether) according to claim 1, wherein the dihydric alcohol is substituted or unsubstituted straight, branched, or cyclic aliphatic, aliphatic aromatic, or aromatic diol having 2 to 36 carbon atoms and a molecular weight of 250 to 4,000. ) An absorbent article selected from the group consisting of glycols. The absorbent article of claim 1 wherein the film further comprises a multifunctional branching agent. The absorbent article of claim 7 wherein the multifunctional branching agent is selected from the group consisting of three or more carboxylic acid functional groups, three or more hydroxy functional groups, and a material having all of these functional groups. The absorbent article of claim 1 wherein the aromatic dicarboxylic acid is terephthalic acid, the aliphatic dicarboxylic acid is adipic acid and the dihydric alcohol is 1,4-butanediol. 10. The absorbent article of claim 9 wherein the filler material is calcium carbonate. The absorbent article of claim 1 wherein the film has a thickness of less than 250 μm. The absorbent article of claim 1 wherein the laminated outer cover further comprises a nonwoven fabric. The absorbent article of claim 12 wherein the nonwoven is a spunbonded nonwoven. The absorbent article of claim 12 wherein the basis weight of the nonwoven is less than 30 g / m ² . The absorbent article of claim 12 wherein the film and the nonwoven are bonded together with an adhesive. The absorbent article of claim 12 wherein the film and the nonwoven are thermally bonded together. The absorbent article of claim 12 wherein the film and the nonwoven are ultrasonically bonded together. The absorbent article of claim 1, wherein the laminated outer cover further comprises a bonded carded web. The absorbent article of claim 1 wherein the absorbent article is selected from the group consisting of diapers, training pants, and incontinence garments for adults. A laminated outer cover comprising an extended biodegradable aliphatic aromatic copolyester film comprising filler particles and a copolyester,  The copolyester comprises 10 mol% to 30 mol% terephthalic acid, 20 mol% to 40 mol% adipic acid, 30 mol% to 60 mol% 1,4-butanediol and has a weight average molecular weight of 90,000 to 160,000 An absorbent article having a dalton, a number average molecular weight of 35,000 to 70,000 daltons, and a glass transition temperature of less than 0 ° C.

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