Hidden elastic olefin film laminates and methods of making absorbent articles incorporating same

Abstract

A recessive elastic olefin film laminate comprising a film comprising predominantly an olefin elastomer and a method of making an absorbent article incorporating the same are provided. The film is stretched and maintained in a stretched state to impart a desired level of recessive elasticity such that the conditioned film laminate shrinks when activated, for example by heating. The recessive elastic film laminates can be advantageously used in the manufacture of a variety of elastomeric articles, including absorbent personal care articles, by activating recessive elasticity after attachment to the article, thereby wrinkling and elasticizing the components to which the film laminates are attached.

Description

[0001] This application is a divisional application of the PCT international application PCT / US2017 / 059056, whose application date is October 30, 2017 and whose invention name is “Hidden elastic olefin film laminate and method for preparing absorbent products combined therewith”, which entered the Chinese national phase on April 11, 2019 and has application number 2017800628506.

[0002] This application claims priority to U.S. Provisional Patent Application Serial No. 62 / 415,186, filed on October 31, 2016, the entire contents of which are incorporated herein by reference. Background Art

[0003] Elastic materials are usually incorporated into many articles worn on or around the body to improve their ability to better fit the body contour. Examples of such articles that usually use elastic materials include diapers, training pants, adult incontinence clothing, personal protective clothing, wraps, etc. However, elastic materials usually show undesirable hand feel and / or softness levels. Therefore, considering the possibility of skin contact, elastic composite materials are usually used in personal care products and clothes. Elastic composite materials can be formed, for example, by elastic film and one or more outer fabric materials (such as nonwoven fabrics), so as to provide the required hand feel and softness. The nonwoven fabric can be joined to the elastic film, and the film is in a stretched state at the same time, so that the nonwoven fabric can be gathered between the positions where the nonwoven fabric is bonded to the film when the film retracts. The resulting elastic composite material can then be stretched to such an extent that the nonwoven fabric gathers between the bonding positions, and the expansion and flattening of the aggregates allow the elastic film and the composite material to stretch. Examples of composite materials for stretching bonding are disclosed in, for example, US4720415 of Vander Wielen et al. and US5385775 of Wright. Unfortunately, however, the stretchable nature of the composite material often causes problems during the manufacturing process of the article incorporating the composite material. For example, the force required to unwind a rolled composite material can at least partially stretch the elastic composite material while the elastic article is under tension. This partial extension of the stretchable composite material can make it difficult to properly measure the required amount of elastic material in the final product and its positioning therein. In addition, the manufacture of multi-layer articles may require that extensibility be imparted to the article itself, and the method of Vander Wielen and Wright is not easily applicable to the manufacture of complex multi-component articles due to its nature. In this regard, a considerable degree of implicit elasticity would be desirable.

[0004] Elastic composites with latent elasticity are known, including, for example, those described in US Pat. No. 7,585,382 to Hughes et al. In this regard, Hughes utilizes a mixture of olefin and non-olefin elastomers to produce crystalline domains upon stretching, such that subsequent application of heat returns the domains to their unoriented state and causes the stretched film to shrink. However, Hughes requires the use of relatively expensive polymer components and additional blending and compounding steps.

[0005]

[0006] Therefore, there remains a need for improved latent elastic composites formed primarily from olefin polymers that have strong retractive forces when heat activated and are significantly less elastic prior to reactivation and placement into a final product, and methods of making the same. Summary of the invention

[0006] The present invention provides a heat shrinkable composite material, comprising: an elastic film having a polymer portion, the polymer portion comprising at least 90% of a semi-crystalline polyolefin polymer; and a support layer intermittently bonded to the elastic film, wherein the composite material has a heat shrinkage of greater than about 15% at 72°C. In certain embodiments, the polymer portion of the elastic film may be substantially entirely comprised of an olefin polymer, and in other aspects, substantially entirely comprised of a semi-crystalline polyolefin polymer, such as a polymer having a density between about 0.85 g / cm 3 and 0.90g / cm 3 In addition, in certain embodiments, the elastic film may include ethylene polymers, propylene polymers, and blends thereof. In addition, in certain embodiments, the support layer may include a fabric, such as a fabric having a basis weight of less than about 20 g / M 2 and a nonwoven fabric having a tensile strength greater than about 50 g-f.

[0007] Also provided is a method of making an elastic article, comprising the steps of: (i) melt extruding an extrudate having a polymer portion comprising at least 90% of a semi-crystalline olefin polymer; (ii) cooling the extrudate to form a film having a temperature between about 10°C and about 50°C; (iii) then stretching the film to between 2 and 7 times its original length; (iv) bonding a support layer to the stretched film at intermittent locations to form a composite material; (v) winding the composite material onto a winding roll under tension such that the composite material shrinks to less than about 80% of its length (relative to the length when bonded); (vi) aging the tensioned composite material on the roll for at least 24 hours to form a heat shrinkable composite material; (vii) attaching the heat shrinkable composite material to a single component of the article or to at least two components of the article that are remote from each other at two locations remote from each other; and (viii) applying heat to the heat shrinkable composite material, wherein the composite material shrinks and acts to pull inwardly between the attachment points and move the attachment points closer to each other to form elasticized regions within the article. In certain embodiments, the methods may be used to form elastic features of diapers or other garments, such as to form elasticized waistbands, side panels, back panels, front panels, and / or cuffs. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a schematic diagram of a method for forming a composite material according to one embodiment of the present invention;

[0009] Figure 2 is a schematic diagram of a method of forming a composite material according to an alternative embodiment of the present invention;

[0010] Figure 3 is a perspective view of an absorbent personal care article incorporating the elastic composite of the present invention. DETAILED DESCRIPTION

[0011] definition

[0012] Throughout the specification and claims, discussion of the article and / or its individual components has the understanding set forth below.

[0013] The term "comprising" or "including" or "having" is inclusive or open-ended and does not exclude additional unlisted elements, components or method steps. Therefore, the term "comprising" or "including" or "having" encompasses the more restrictive terms "consisting essentially of" and "consisting of".

[0014] As used herein, the term "polymer" generally includes, but is not limited to, homopolymers, copolymers, such as block, graft, random and alternating copolymers, terpolymers, and the like, as well as blends and modifications thereof. In addition, unless otherwise specifically limited, the term "polymer" shall include all possible geometric configurations of the molecule. These configurations include, but are not limited to, isotactic, syndiotactic and random symmetries.

[0015] As used herein, "propylene polymer" means a polymer having a propylene content greater than 50 mol%.

[0016] As used herein, "ethylene polymer" means a polymer having an ethylene content greater than 50 mole percent.

[0017] As used herein, "olefin polymer" means a polymer having an olefin content greater than 50 mole percent.

[0018] As used herein, the term "nonwoven web" means a structure or web of material that is formed without using conventional fabric forming processes such as weaving or knitting to produce a structure of individual fibers or threads that are entangled or interwoven, but not in an identifiable repeating pattern.

[0019] As used herein, the term "fabric" refers to cohesive fibrous sheet materials and includes woven, knitted and nonwoven materials.

[0020] As used herein, the term "machine direction" or "MD" refers to the direction of travel of a film.

[0021] As used herein, the term "cross-machine direction" or "CD" refers to a direction substantially perpendicular to the machine direction defined above.

[0022] As used herein, the terms "elastomeric" and "elastic" refer to a material that can stretch in at least one direction (such as the MD direction) after a stretching force is applied and that contracts and returns to approximately its original dimensions after the stretching force is released. For example, the stretched material may have a stretched length that is at least 50% greater than its relaxed, unstretched length and will return to within at least 50% of its stretched length after the stretching force is released. A hypothetical example would be a one (1) inch sample of material that can be stretched to at least 1.50 inches and will recover to a length of no more than 1.25 inches after the stretching force is released. Advantageously, the material contracts or recovers at least 50% of the stretched length, and even more advantageously at least 80%.

[0023] As used herein, the term "percent stretch" refers to the degree to which a material stretches in a given direction when subjected to a certain force.

[0024] The film extrudate and the corresponding elastic film of the present invention include a polymer portion, and in one aspect, the polymer portion of the film includes greater than 90%, 92%, 95% or 98% of one or more semi-crystalline polyolefin polymers. Exemplary semi-crystalline polyolefins include polyethylene, polypropylene, their blends and copolymers. In certain embodiments, the polymer portion of the film extrudate and / or elastic film may include all or substantially all of the olefin polymers, and on the other hand, may include all or substantially all of the one or more semi-crystalline polyolefin polymers. In certain embodiments, the film extrudate and the corresponding elastic film may include a mixture of semi-crystalline olefin polymers, such as a mixture of semi-crystalline ethylene and propylene polymers. For example, in certain embodiments, the semi-crystalline polymer may include a mixture, the mixture includes greater than about 60% of an ethylene polymer and less than about 40% of a propylene polymer, such as wherein the ethylene polymer accounts for between about 80% and about 99% of the semi-crystalline polymer or between about 85% and about 95%, and the propylene polymer accounts for between about 1% and about 20% of the semi-crystalline polymer or between about 5% and about 15%. In alternative embodiments, the semi-crystalline polymer may comprise a mixture comprising greater than about 60% propylene polymer and less than about 40% ethylene polymer, for example wherein the propylene polymer comprises between about 80% and about 99% or between about 85% and about 95% of the semi-crystalline polymer, and the ethylene polymer comprises between about 1% and about 20% or between about 5% and about 15% of the semi-crystalline polymer.

[0025] Semi-crystalline polyolefins have or can exhibit a substantially regular structure. For example, a semi-crystalline polyolefin may be substantially amorphous in its undeformed state, but may form crystalline domains and / or increased polymer chain arrangements when stretched. The crystallinity of the olefin polymer may be from about 3% to about 30%, from about 5% to about 25% in some embodiments, and from about 5% to about 15% in some embodiments. Likewise, a semi-crystalline polyolefin may have a latent heat of fusion (ΔH) of from about 15 to about 75 joules / gram ("J / g"), from about 20 to about 65 J / g in some embodiments, and from 25 to about 50 J / g in some embodiments. f ), the latent heat of fusion is another indicator of crystallinity. The semi-crystalline polyolefin may also have a Vicat softening temperature of about 10°C to about 100°C, in some embodiments about 20°C to about 80°C, and in some embodiments about 30°C to about 60°C. The semi-crystalline polyolefin may have a melting temperature of about 20°C to about 120°C, in some embodiments about 35°C to about 90°C, and in some embodiments about 40°C to about 80°C. The latent heat of fusion (ΔH f) and melting temperatures can be determined using differential scanning calorimetry ("DSC") according to ASTM D3417-99, as is well known to those skilled in the art. The Vicat softening temperature can be determined according to ASTM D1525-09. As is well known in the art, percent crystallinity can be calculated using the heat of fusion obtained from DSC as described above. By dividing the measured ΔH of the sample by f Divide by the ΔH of the 100% crystalline polymer f This amount is then multiplied by 100 to calculate the percent crystallinity. Assuming a 100% crystalline propylene polymer with a ΔH f is 189 J / g, and assuming a 100% crystalline ethylene polymer ΔH f It is 292J / g.

[0026] Particularly suitable polyethylene copolymers are those that are "linear" or "substantially linear". The term "substantially linear" means that the ethylene polymer contains long chain branches in the polymer backbone in addition to short chain branches that can be attributed to the incorporation of comonomers. "Long chain branches" refers to a chain length of at least 6 carbons. Each long chain branch can have the same comonomer distribution as the polymer backbone and is as long as the polymer backbone to which it is attached. Preferred substantially linear polymers are substituted with 0.01 long chain branches per 1000 carbons to 1 long chain branch per 1000 carbons, and in some embodiments are substituted with 0.05 long chain branches per 1000 carbons to 1 long chain branch per 1000 carbons. In contrast to the term "substantially linear", the term "linear" means that the polymer lacks measurable or obvious long chain branches. That is, the polymer is substituted with less than 0.01 long chain branches per 1000 carbons on average.

[0027] In a particular embodiment, ethylene and α-olefins such as C3-C 20 α-olefins or C3-C 12Ethylene polymers of copolymers of α-olefins. Suitable α-olefins may be linear or branched (e.g., one or more C1-C3 alkyl branches, or aryl groups). Specific examples include 1-butene; 3-methyl-1-butene; 3,3-dimethyl-1-butene; 1-pentene; 1-pentene with one or more methyl, ethyl or propyl substituents; 1-hexene with one or more methyl, ethyl or propyl substituents; 1-heptene with one or more methyl, ethyl or propyl substituents; 1-octene with one or more methyl, ethyl or propyl substituents; 1-nonene with one or more methyl, ethyl or propyl substituents; 1-decene substituted with ethyl, methyl or dimethyl; 1-dodecene and styrene. Particularly desirable α-olefin comonomers are 1-butene, 1-hexene and 1-octene. The ethylene or propylene content of such copolymers can be from about 60 mol % to about 99 mol %, in some embodiments from about 80 mol % to about 98.5 mol %, and in some embodiments from about 87 mol % to about 97.5 mol %. The α-olefin content can also be in the range of from about 1 mol % to about 40 mol %, in some embodiments from about 1.5 mol % to about 15 mol %, and in some embodiments from about 2.5 mol % to about 13 mol %. The density range of the ethylene polymer elastomer can be about 0.85 g / cm 3 To about 0.90g / cm 3 , in certain embodiments, between about 0.85 g / cm 3 To about 0.89g / cm 3 Between or between about 0.86 to about 0.89 g / cm 3 Density can be measured at room temperature according to ASTM 1505-10.

[0028] Suitable propylene polymers may include, for example, propylene copolymers or terpolymers, propylene and α-olefins (e.g., C3-C 20 ) copolymers such as ethylene, 1-butene, 2-butene, various pentene isomers, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 4-methyl-1-pentene, 4-methyl-1-hexene, 5-methyl-1-hexene, vinyl cyclohexene, styrene, etc. The comonomer content of the propylene polymer can be about 35 wt% or less, in some embodiments about 1 wt% to about 20 wt%, and in some embodiments about 2 wt% to about 10 wt%. Preferably, the density of the polypropylene (e.g., propylene / α-olefin copolymer) can be 0.91 g / cm 3 or less, and in certain embodiments may be between about 0.85 g / cm 3 and about 0.90g / cm 3 Between, between about 0.85g / cm 3 and about 0.89g / cm3 , between about 0.85g / cm 3 and about 0.88g / cm 3 Between, even between about 0.85g / cm 3 Up to 0.87g / cm 3 between.

[0029] Exemplary commercially available polyolefin-based thermoplastic elastomers for use in elastomeric films include VISTAMAXX TM (propylene-based elastomer, available from ExxonMobil Chemical, Houston, Tex.), INFUSE TM (olefin block copolymer, available from Dow Chemical Company, Midland, Mich.), VERSIFY TM (propylene-ethylene copolymer) such as VERSIFY TM 4200 and VERSIFY TM 4300 (Dow Chemical Company, Midland, Mich.), ENGAGE TM (ethylene-octene copolymer, available from Dow Chemical, Houston, Tex.) and NOTIO 0040 and NOTIO 3560 (available from Mitsui Chemical (USA), New York, New York). In a particularly suitable embodiment, the polyolefin-based thermoplastic elastomer is VISTAMAXX TM 6102FL.

[0030] Any of a variety of known techniques can be used to form semi-crystalline polyolefins. For example, olefin polymers can be formed using free radicals or coordination catalysts (e.g., Ziegler-Natta). In certain embodiments, olefin polymers can be formed by single-site coordination catalysts such as metallocene catalysts. Such catalyst systems produce such ethylene copolymers, wherein comonomers are randomly distributed in the molecular chain and uniformly distributed in the parts of different molecular weights. Olefin elastomers and preparation methods thereof include but are not limited to those described in US5272236, US5278272, US5472775, US5539056, and US7582716 of Liang, etc., the contents of which are incorporated herein by reference to the extent consistent with this article.

[0031] The film may also include other components as needed to achieve or enhance various properties. For example, in addition to the semi-crystalline polyolefin polymer, the film may optionally include fillers, colorants, plasticizers, tackifiers, antioxidants and / or other known additives. In certain embodiments, the film may include an opaque filler or colorant such as TiO2 in an amount of about 0.1 to about 5 weight % or about 0.5 to about 3 weight % of the film extrudate and elastic film. In other embodiments, a heat and / or UV stabilizer package, such as Eastman Regalrez 1049 or 1126, may be used in an amount between about 2-10 weight % or between about 3-8 weight % of the film extrudate or elastic film. On the other hand, the content of the tackifier may be less than 10 weight %, such as oligomers and / or polymers containing short chain olefins, such as short chain (≤C 20 ) Oligomers of amorphous poly-alpha-olefin (APAO).

[0032] Method for preparing hidden elastic film

[0033] Many different known techniques can be used to form films from extrudates, including blow molding, casting, flat die extrusion, etc. Once refrigerated, the implicit properties of the film can be introduced by stretching orientation. Although not required, the film can be stretched in parallel without having to remove the film for separate processing. For example, the film is immediately pulled by rollers with different speeds so that the sheet is stretched to a desired stretch ratio in the longitudinal direction (machine direction). The "uniaxial" stretched film can then be laminated to the fiber web. In addition, the uniaxially stretched film can also be oriented in the cross-machine direction to form a "biaxial" stretched film. For example, the film can be clamped at its lateral edges by a chain clamp and transported to a tenter. In the tenter, the film can be stretched to a desired stretch ratio in the transverse direction by a chain clamp separated in the forward advance.

[0034] In order to obtain the desired film latent elasticity, various parameters of the stretching operation are selectively controlled, including stretching ratio, stretching temperature, time kept in a stretched state, etc. The stretching ratio can be determined by dividing the linear speed of the film leaving the stretching operation by the linear speed of the film entering the stretching operation. In some embodiments, for example, the film is stretched (for example, along the machine direction) to a stretching ratio of about 2 to about 7, about 3 to about 6 in some embodiments, and about 4 to about 6 in some embodiments. The orientation temperature distribution is selected to provide the desired shrinkage mechanical properties, such as shrinkage tension and shrinkage percentage. More specifically, the orientation temperature is lower than the melting temperature of the semi-crystalline polyolefin. For example, the travel distance of the cooling roller and the film extrudate can be selected so as to obtain a film with sufficient crystallization during stretching to withstand the high tension and stress associated with the stretching operation. In certain embodiments, the temperature of the film extrudate may have an external temperature of about 12°C to about 60°C at the beginning of stretching, and in other embodiments, between about 12°C to about 50°C or between about 18°C ​​to about 43°C. Specifically, when using propylene polymers, it is generally desired to perform film stretching operations at the lower end of the range. Preferably, the film is "cold drawn," ie, stretched at ambient temperature without the application of external heat (eg, heated rollers), to improve latent elasticity.

[0035] Additionally, to achieve the desired invisibility and high retractive force, the film may be stretched and maintained in a stretched state for a period of time exceeding the time required to achieve elasticity. This may be accomplished in any of a number of ways, including, for example, employing an extended stretching system so as to maintain the stretched tensioned state for the desired duration. Alternatively, the stretched film may be wound on a roller in a tensioned state, wherein the tension on the film when wound on the roller may be substantially the same as or less than a selected degree of tension applied for the stretch-thinning step.

[0036] In one embodiment and with reference to Figure 1 , a polymer extrudate is fed from a hopper (not shown), melted and directed to an extrusion device 10, such as a film die. The extruded film 12 is then first stretched and thinned, for example, as desired, by a conventional blown film process, a cast film process, or other desired film forming process. For blown film, air is used to expand a bubble of the extrudate through an annular die. The bubble then collapses and is collected in the form of a flat film. Methods for producing blown film are described, for example, in US3354506 to Raley; US3650649 to Schippers; US3801429 to Schrenk et al., US6824734 to Boggs et al., and US2005 / 0245162 to McCormack et al. In Figure 1In a particular embodiment of the present invention, the blown film 12 is directed to a nip roll or "chill roll" 14 to form a single layer precursor elastic film 16. If a multilayer film is to be produced, the multiple layers are coextruded together into the nip roll. Typically, the nip roll 14 is maintained at a temperature sufficient to solidify and quench the blown film 12 as it is formed, such as about 20° C. to 60° C., to achieve the film temperature as described above.

[0037] The elastic precursor film 16 is then stretch-thinned in the machine direction by passing through a series of rollers 18 traveling at different peripheral speeds. In this regard, a first set of drive rollers 18A travels at a slower peripheral speed than a second set of drive rollers 18B located downstream of the first set of rollers 18A. Figure 1 Four rollers are shown as part of the drive roller 18, but it should be understood that a higher number of rollers may be provided as desired, depending on the desired level of stretching and the degree of stretching between the individual rollers. The film may also be stretched in one or more discontinuous stretching operations as is known in the art. Alternatively, the elastic film may also be stretched using a conventional film orientation unit or machine direction orientator ("MDO") (e.g., commercially available from Parkinson Technologies, Inc.). Due to machine direction orientation and stretching, the elastic film is subsequently formed into a film 20, which is then directed to another set of nip rollers 28.

[0038] At least one support member is used as a facestock material for lamination to the stretched elastic film. In this regard, the support member may include one or more fiber materials or films having desired physical properties, such as a pleasing hand feel, softness, aesthetics, tensile strength, and / or other desired properties. Importantly, the support member provides additional strength properties to the elastic film required for the associated processing, conversion, and manufacture of the final article and / or allows for sufficient durability in use. In this regard, the support member provides additional tensile strength to the composite material, and in this regard, the support fabric has a tensile strength of at least about 50 g-f, including, for example, having a tensile strength greater than about 100 g-f, 150 g-f, 200 g-f, 250 g-f, or even 300 g-f, and in certain embodiments, the tensile strength is less than about 5000 g-f, 3000 g-f, 2500 g-f, 2000 g-f, or even 1500 g-f. In addition, the support member desirably provides a pleasing hand feel. However, while increased strength is desirable, it is important not to significantly degrade the retractive force performance of the film and corresponding laminate. In this regard, the support member may be selected to be highly drapey and / or to have a low flexural modulus.

[0039] Fabrics suitable for use as support members in the present invention include, but are not limited to, woven or knitted fabrics and nonwoven fabrics, such as fabrics made by meltblowing, spunbonding, carding and / or hydroentanglement processes. Examples of suitable fabrics and methods for making them include, but are not limited to, US5492751 of Butt et al., US6224977 of Kobylivker et al., US8603281 of Welch et al., WO99 / 32699 of Stokes et al., and WO16 / 080960 of Kupelian et al.

[0040] Generally speaking, to limit the negative impact on retraction forces, lower basis weight support materials and fabrics will be used. In this regard, the fabric ideally has a basis weight of less than about 30 g / m 2 In certain embodiments, the support material and fabric may have a basis weight of less than about 25 g / m 2 , 20g / m 2 , 18g / m 2 or even 16g / m 2 , and in certain embodiments, may have a basis weight exceeding about 5 g / m 2 , 7g / m 2 Or even 8g / m 2 In addition, to achieve greater drape, it may be desirable to treat the fabric in one or more additional aspects, such as by using internal softeners, external softeners and / or mechanical softening treatments.

[0041] For example, the mechanical treatment of the web can be carried out by many different methods, such as micro-creping, cold embossing, broken rod treatment, necking, ring rolling and combinations thereof. However, other methods known in the art can also be used. Regarding stretching, it can be conducted along the MD, for example, by using a drive roller, or along the CD, for example, by using a tenter. It is also possible to stretch and soften the fabric by grooved roller stretching. Examples of various methods for mechanically treating fabrics to impart improved drape and softness include, but are not limited to, those described in US5413811 of Fitting et al., US5770531 of Sudduth et al., US5810954 of Jacobs et al., US6197404 of Varona, US6372172 of Sudduth et al., and US2004005457 of DeLucia et al.

[0042] The sufficiently drapeable and pliable support fabric may optionally include one or more internal softeners. The specific composition of the softener is not considered to be limiting, but may be anionic, nonionic or cationic. Examples of softeners include, but are not limited to, the following: olefin waxes, such as polyethylene waxes; fatty acids, such as erucic acid, oleic acid, stearic acid; fatty acid amides, such as stearamide or oleylamine; sulfated oils, such as castor, olive and soy; sulfated fatty alcohols or fatty acid esters; glycols and their derivatives, such as glycerol, monostearate, triolein; polyethylene glycol esters of fatty acids, such as palmitic acid and stearic acid long chain amides; sugar alcohols and their derivatives, such as sorbitol and sorbitan stearate; imidazolines; and the like. Examples of additives for improving the drape and softness of fabrics and films include, but are not limited to, those described in US5770531 to Sudduth et al., US6197404 to Varona, US2004005457 to DeLucia et al., and WO2014 / 044235 to Klaska et al.

[0043] By incorporating one or more softening agents less than about 5% by weight in the final composition of extruding or otherwise forming a fiber or film, the drapability and softness of the nonwoven web can be achieved. In other embodiments, the softening agent can be less than about 5%, 3%, or even 1% by weight, and in certain embodiments, the softening agent can be incorporated into the fiber and / or film in an amount greater than about 0.1%, 0.3%, or even 0.5% by weight. As is well known in the art, the softening agent can be compounded with the fiber or film-forming resin as a concentrate, then added and mixed with the uncompounded resin to achieve uniform distribution of the reagent as a part of the masterbatch process.

[0044] The support member or fabric may be manufactured in parallel with the elastic membrane and / or provided from a supply roll. Figure 1 , the first nonwoven fabric 22A can be unwound from the first supply roll 24A and directed through the first set of drive rolls 26A. The nonwoven web 22A can then be directed into the nip formed by the bonding roll 28 along with the stretch film 20. As the superimposed materials travel through the bonding roll 28, they bond to each other and form a cohesive elastic laminate 30. The elastic film 20 can be bonded to the nonwoven fabric 22A using a variety of techniques, including adhesive bonding, such as by gravure printing, slot or spray adhesive systems, and mechanical bonding, such as by thermal bonding, ultrasonic bonding, etc.

[0045] However, in order not to overly restrict elasticity and / or shrinkage, the fabric is ideally bonded to the elastic film using a pattern that provides a bonding area of ​​less than about 35%, 30%, 25% or even 20%, and in some embodiments, has a bonding area of ​​at least about 3%, 5%, 8% or even 10%. In addition, with regard to thermal bonding, in some embodiments, the fabric can be bonded to the elastic film at a temperature below about 150°C and above about 110°C. The bonding pattern used may include a pattern of discrete, spaced bonding points; such bonding points may have various shapes, including curved shapes such as circles or ovals, geometric shapes such as squares, rectangles or triangles, and icons such as puppies, leaves or other recognizable objects. Individual bonding points may be solid or hollow (i.e., having an unbonded inner portion). Alternatively, the pattern may include a series of continuous bonding lines, such as discretely spaced non-intersecting lines, including, for example, parallel and spaced lines having a sine curve or other configuration with a fine crenulation. Additionally, the bonding pattern may be provided as part of an open lattice-type pattern comprising a series of intersecting lines, such as those of a honeycomb-type pattern.

[0046] Optionally, the elastic film may also be bonded to the second fabric so that the elastic film is located between the two outer fabrics. Figure 1 As shown, the elastic film 20 is simultaneously bonded on its other side to a second nonwoven fabric 22B originating from a second supply roll 24B and passing through a second drive roll 26B. The second fabric 22B may be the same or different from the first fabric 22A. The nonwoven webs 22A and 22B may be directed into a nip formed by a bonding roll 28 with the stretch film 20, wherein the film is located between the outer nonwoven fabric layers 22A, 22B. As the superimposed materials travel through the bonding roll 28, they bond to each other, thereby forming a cohesive elastic laminate 30.

[0047] As another option, the peripheral speed of the drive roll 26 can be the same as or slower than the peripheral speeds of the laminating roll 28 and the winding roll 32. In this regard, by employing a slower peripheral speed of the drive roll 26, necking of the nonwoven fabrics 22A, 22B can be achieved, as is known in the art, to obtain improved drape and / or CD extensibility of the nonwoven fabrics and composites.

[0048] In reference Figure 1In the present embodiment shown, the composite material 30 is wound onto the winding roll 32 under tension, which is substantially the same as the tension applied to the elastic films 16, 20 upstream of the laminating roll 28. By using the same circumferential speed of the winding roll 32 as the laminating roll 28 and / or the stretching roll 18B, the composite material 30 remains completely under tension without retraction. Alternatively, by applying a tension that is only slightly less than the tension applied upstream by the laminating roll 28 and / or the stretching roll 18B, the elastic composite material can be allowed to retract slightly. This can be achieved by using a slower circumferential speed of the roll 32 relative to the laminating roll 28. In this regard, the elastic composite material can be allowed to retract no more than about 35%, 30%, 25%, 20% or even 15%. Since the film 20 of the composite material 30 is tensioned before lamination, it will retract toward its initial pre-stretched machine direction length when relaxed and thus become shorter in the machine direction, thereby bending or forming wrinkles in the outer support layer of the composite material. The resulting elastic composite thus becomes extensible in the machine direction to the extent that wrinkles or bends in the outer fabric can be flattened out after being pulled back, thereby allowing the elastic film to stretch.

[0049] The composite material under tension on the roll is maintained at ambient conditions for at least about 24 hours, 48 ​​hours, or even 72 hours to achieve further setting and / or crystallization of the stretched (stretched) polymer film. Subsequent heating of the composite material to above the softening temperature of the semi-crystalline polymer(s) causes the highly oriented regions to return to an amorphous state and "shrink" along the MD, resulting in the formation of wrinkles and an elastic composite material with a significantly higher degree of elasticity.

[0050] The elastic composite formed according to the present invention exhibits a hidden shrinkage with high retractive force, capable of pulling the facestock material and other materials bonded thereto as part of a personal care absorbent article. For example, the percent heat shrinkage of the composite at 72°C is desirably greater than about 15%, 20%, 25%, 30% or 35% (relative to the length before heat activation and shrinkage), and in certain embodiments may be less than about 55% or 50%. In addition, the percent stretch of the activated (contracted) elastic composite is at least 50%, 60%, 70% or 80%.

[0051] In an alternative embodiment, and with reference to Figure 2 , extrudates are extruded, blown and stretched in a similar manner. In this regard, the same numbers have been used to indicate the same parts and / or functions. However, Figure 1Unlike the process described, the stretch film 20 is maintained under tension along the S-wrap assembly 19 before being laminated to the face material or fabric. In certain embodiments, the stretch film 20 is then maintained in a stretched state for at least about 0.5 seconds, 0.6 seconds, or 0.8 seconds or longer. The continuous state under the stretched condition helps to increase and / or set the hidden properties in the film. The conditioned stretch film 21 is then laminated to at least one support material or fabric 22A, and optionally also laminated to a second support material or fabric 22B to form a multilayer laminate or composite material 31. The composite material 31 is then wound onto a winding roll under tension, however, the tension may be less than the tension associated with the previous embodiment. In this regard, the composite material can be substantially retracted before being wound onto the roll, for example, by adopting a winding speed of the winding roll 32 that is less than the speed of the composite material 31 just before the bonding roll 28. The composite material can be retracted to approximately 80%, 75%, 70%, 65% or even 60% of its length; in other words, the winding roller 32 can be operated at a circumferential speed of at least approximately 20%, 25%, 30%, 35% or even 40% of the upstream roller (such as the laminating roller 28 shown in the present embodiment).

[0052] It is easy to understand that the above process can be incorporated into other methods for preparing elastic laminates. For example only, the method of the present invention can be incorporated into one or more methods and form the material described in US7803244 of Siqueira et al., and the content of the patent is incorporated herein by reference to the extent consistent with this article. For example, elastic membranes 20, 21 and outer fabrics 22A, 22B can be guided to the roller gap defined between rollers 28 for attaching each layer and forming a cohesive multilayer laminate. One or both of the rollers 28 can include a plurality of elevated bonding elements and / or can be heated. When laminating, elastic membranes 20, 21 are melt-bonded to fiber materials 22A, 22B at a plurality of discrete bonding sites. That is, one or more elastomeric polymers of elastic membranes 20, 21 soften and / or melt so that they can physically trap the fibers of fabrics 22A, 22B. Of course, elastic membranes 20, 21 can have a certain viscosity so that it also adheres to the fibers when laminating. Depending on the heat and / or pressure applied by the patterned roll, the bonding sites can be located near corresponding holes that were formed by displacement of the film. As described in more detail in Siqueira, the specific location of bonding sites adjacent to or near holes can enhance the integrity of the resulting composite by strengthening the area around the holes and also provide vapor permeability to the composite.

[0053] In addition, although not shown here, various other possible processing and / or finishing steps known in the art such as cutting, handling, expanding holes, printing patterns, etc. can be carried out without departing from the spirit and scope of the present invention. For example, the resulting composite material can be optionally mechanically stretched in the cross machine direction and / or machine direction to enhance extensibility. In one embodiment, the composite material can be guided through two or more rollers with grooves in the CD and / or MD direction. In addition to the grooved roller, other techniques can also be used for mechanically stretching the composite material in one or more directions. For example, the composite material can be passed through a tenter, a machine direction orientator or other devices known in the art. As mentioned above, the composite material can be alternatively and / or additionally necked. Examples of various stretching systems considered suitable for use in the present invention include, but are not limited to, those described in US414400 to Schwarz, US4981747 to Morman, US5770531 to Sudduth et al., US5789065 to Haffner et al., US6368444 to Jameson et al., US7198742 to Gerndt, US7320948 to Morman et al., and US2006 / 151914 to Gerndt et al.

[0054] The composite material of the present invention can be processed into the final product more easily because it has less elasticity before activation and is therefore more stable in size. For example, the hidden elastic composite material can be incorporated into an absorbent personal care product or personal protective clothing to provide elastic regions and / or components therein. During the manufacturing or assembly process, the hidden elastic composite material can be attached to one or more other components of the product and then activated by applying heat, or specifically used for the function of the shrink film or combined with other functional steps, such as in the curing process of the adhesive used to connect the components of the product together. Because the hidden elastic composite material has a higher dimensional stability than a high elastic material, improved processing efficiency can be achieved. For example, during attachment to other components of the product, the composite material does not need to be kept in a mechanically stretched state. This allows greater freedom in the location and manner of applying the adhesive. In addition, the shrinkage of the film and the wrinkling of the composite material together with one or more components of the product combined therewith can produce products with improved elasticity and / or freedom of movement.

[0055] Those skilled in the art will appreciate that the application and use of the elastic composite material of the present invention can be used to manufacture and construct absorbent personal care products, such as diapers, adult incontinence garments, incontinence pads / liners, sanitary napkins, panty liners, and the like. In this regard, absorbent personal care products typically include a liquid-impermeable outer cover, a liquid-permeable top sheet positioned in a facing relationship with the outer cover, and an absorbent core between the outer cover and the top sheet. In addition, absorbent personal care products also typically include one or more fit-related components, such as fastening belts or tabs, waistbands, elastic waist panels, elastic side panels, elasticized leg cuffs, wings, and the like. The unique elastic composite materials prepared and provided herein are very suitable for use as a component of an absorbent personal care product having one or more elasticized components or as a component. By way of example only, various elasticized personal care absorbent articles and methods of making the same include, but are not limited to, those described in US Pat. No. 4,685,916 to Enloe, US Pat. No. 4,816,094 to Pomplum et al., US Pat. No. 4,857,067 to Wood et al., US Pat. No. 5,643,396 to Rajala et al., US Pat. No. 5,745,922 to Rajala et al., US Pat. No. 5,940,887 to Rajala et al., US Pat. No. 6,336,922 to Van Gompel et al., US Pat. No. 6,953,452 to Popp et al., US Pat. No. 7,018,369 to Van Gompel et al., and US Pat. No. 7,150,731 to Cazzato et al., the contents of which are incorporated herein by reference to the extent consistent herewith.

[0056] As previously noted, absorbent personal care products typically include a liquid-permeable top sheet facing the wearer, and a liquid-impermeable back sheet or outer cover. Disposed between the top sheet and the outer cover is an absorbent core. In this regard, the top sheet and the outer cover are typically joined and / or sealed to encase the absorbent core. Although certain aspects of the present invention are described in the context of specific personal care absorbent products, it should be readily understood that similar uses in other types of personal care absorbent products and / or other combinations or changes of the specific constructions discussed below can be made by those skilled in the art without departing from the spirit and scope of the present invention.

[0057] In a specific embodiment, and with reference to Figure 3 , the diaper 50 may include a liquid-impermeable outer cover 54, a liquid-permeable top sheet 52 positioned in a facing relationship with the outer cover 54, and an absorbent core (not shown) between the outer cover 54 and the top sheet 52. The diaper 50 may have a variety of shapes, such as an overall rectangular shape, a T-shape, an hourglass shape, etc. The top sheet is generally coextensive with the outer cover, but may optionally cover an area greater or less than that of the outer cover. Although not shown, it should be understood that portions of the diaper (such as edge sections of the outer cover) may extend past and around the terminal edges of the product and form a portion of the body-facing layer.

[0058] As in Figure 3 The top sheet or body side liner 52 shown representatively in the top sheet or body side liner 52 ideally presents a compliant, soft to the touch and non-irritating body-facing surface to the wearer's skin. The top sheet 52 allows liquid to quickly enter the absorbent article, and ideally also helps to isolate the wearer's skin from the liquid retained in the absorbent core. Top sheets are well known in the art and can be made of a wide variety of materials, such as porous foam, reticulated foam, open-cell plastic film, natural fibers (wool, cotton fibers, etc.), synthetic fibers (polyester, polypropylene, polyethylene, etc.), combinations of natural and synthetic fibers, etc. The top sheet can include a single layer or multiple layers, and the layers include a combination of one or more different materials. Nonwoven fabrics and laminates thereof are generally used to form top sheets. Suitable topsheet materials include, but are not limited to, those described in US5382400 to Pike et al., US5415640 to Kirby et al., US5527300 to Sauer, US5994615 to Dodge et al., US6383960 to Everett et al., US6410823 to Daley et al., and US2014 / 0121623 to Biggs et al.

[0059] Backsheet or outer covering 54 comprises liquid-impermeable material.Ideally, the outer covering comprises a material that prevents water from passing through but allows air and water vapor to pass through. The outer covering may include a single layer of material or multiple layers including one or more layers of different materials.In a particular embodiment, the outer covering may include a film fixedly attached or bonded to one or more nonwoven webs.The specific structure and composition of the outer covering may be selected from various combinations of films and / or fabrics.In this regard, the outermost layer is usually selected to provide desired strength, wear resistance, tactile properties and / or aesthetics.For example, a nonwoven fabric is usually used as the outermost layer of the outer covering.Suitable outer coverings include, but are not limited to, those described in US4041203 of Brock et al., US6075179 of McCormack et al., US6111163 of McCormack et al., and US2015 / 099086 of Cho et al.

[0060] In this embodiment, the diaper 50 may also include an elastic waistband 56 located around the waist opening 55. The elastic composite material that provides elasticity to the waistband may be located on the skin-contacting side of the topsheet, exposed to the outside of the backsheet and / or located between the topsheet and the backsheet. When located on the skin-contacting surface of the topsheet, the waistband may also provide the dual function of acting as a containment pocket as is known in the art. In addition, as Figure 3 As shown, in some embodiments, the diaper can be provided with separate front and rear waistbands 56A, 56B. Alternatively, for some pant-type garments, a continuous elastic waistband can be used.

[0061] In certain embodiments, diaper 50 may also include elastic side panels 56. The elastic composite material providing elasticity for the side panels may form all or part of each side panel. For example, alternatively, non-elastic sheet 58 may be located between fastener 60 and the elastic composite material forming a part of side panel 56. As known in the art, elastic side panels may be integrally formed with backsheet and / or topsheet, or alternatively, include separate components attached to a central diaper chassis, such as attached to at least one or two of backsheet and topsheet. Diaper 50 may also include elastic leg cuffs 62 located around leg openings 61. The leg cuffs may be bent around the leg openings, or may use a plurality of leg elastics extending toward the side panels and front and rear waist openings near the leg openings. In addition, it will be appreciated by those skilled in the art that the elastic composite material of the present invention may be used for one or more different components and / or additional components of the article described herein to provide elasticity and stretching properties thereto.

[0062] In addition, it will be appreciated by those skilled in the art that elastic composites can be similarly used to provide elasticity and conformability enhancement properties to other clothes or articles (including, for example, protective clothing). In this regard, elastic composites can be used to form elastic sheets, waistbands, cuffs, etc. For example only, elastic composites can be used in clothes, such as described in US5594955 of Sommers, US6799331 of Griesbach, etc., and US2005 / 097659 of Aroch, etc., the content of which is incorporated herein by reference to a degree consistent with this article. In a similar manner, elastic composites can be used in another article, such as wipes, sweat pads, bath towels, bandages, body wraps, mattresses, etc.

[0063] Test Method

[0064] Percent stretch: The percent stretch is determined by measuring the increase in the length of the material in the stretched dimension, dividing the value by the original size of the material, and then multiplying by 100. These measurements were determined using a "stripelongation test" (strip elongation test) substantially in accordance with the instructions of ASTM D5035-11. Specifically, the test uses two clamps, each having two jaws, each having a face that contacts the sample. The clamps clamp the material in the same plane, usually vertically, 3 inches apart, and move apart at a specific extension rate. The sample size is 3 inches × 6 inches, the jaw height is 1 inch, the width is 3 inches, and the constant elongation is 300mm / min. The sample is clamped in a Sintech 2 / S tester, for example, with a Renew MTS mongoose box (controller) and using TESTWORKS 4.07b software (Sintech Corp, of Cary, NC). The test is carried out under ambient conditions. The results are usually reported as the average of three specimens, and the results can be obtained using specimens in the transverse direction (CD) and / or the machine direction (MD).

[0065] Heat Shrinkage Percentage: A strip of material under tension on the roller is removed from the roller and allowed to shrink. A 75 mm x 175 mm strip is then cut from the material and marks are placed 100 mm apart, the distance between the marks being the initial length (the recovery length before heating or "BHRL"). The material is then immersed in 72°C water for 2 minutes. The strip of material is then allowed to cool to room temperature. Thereafter, the distance between the marks is measured again (the recovery after heating or "AHRL"). The shrinkage percentage represents the implicit elasticity of the material and is calculated by the following equation:

[0066] Shrinkage percentage = 100*(BHRL-AHRL) / BHRL

[0067] The measurements of 3 samples were taken and averaged. The measurements were performed under ambient conditions.

[0068] Tensile Strength As used herein, "tensile strength" or "strip stretch" is the peak load value, i.e., the maximum force generated by a sample when pulled to rupture. Samples for tensile strength testing were prepared by drying and then die-cutting the specimens to a width of 25 mm and a length of approximately 152 mm. The instruments used to measure tensile strength were the MTS Criterian 42 and the MTS TestWorks TMfor Windows version 4 (MTS Systems Corp., Research Triangle Park, NC). Depending on the strength of the sample being tested, the load cell is selected so that the peak load value falls between 10% and 90% of the full scale value of the load cell. The gauge length is 76 mm and the jaw length is 76 mm. The crosshead speed is 305 mm / min, and the break sensitivity is set at 70%, with slope preset points of 70 g and 157 g. The sample is placed in the jaws of the instrument and centered with the longer dimension parallel to the direction of load application. The test is then started and ends when the sample breaks. For the purposes of this article, the peak load is determined based on the CD tensile strength. Six (6) representative samples were tested, and the arithmetic mean of all the individual samples tested is the tensile strength of the product.

[0069] Examples

[0070] Example 1

[0071] A mixture of 70% INFUSE 9108, 20.5% INFUSE 9508, 9% Vistamaxx and 0.5% antioxidant was melted and extruded to form a film by a cast film process. The film extrudate was passed through a cooling roller at 18°C ​​and then fed into the first S-type winding assembly. The speed of the upstream roller was 0.25M / sec (50fpm) and the speed of the downstream roller was 1.52M / sec (300fpm) to stretch the film. The film was then directed to a second S-type winding assembly operating at a speed of 1.46M / sec (289fpm). From the second S-type winding assembly, the stretched film was directed to a calendering roll operating at 1.39M / sec (273fpm). The stretched film was passed through a calendering roll together with two polypropylene spunbond nonwoven webs, each having a basis weight of 12g / M 2 The nonwoven web and the film are laminated in a calendering roll using a Rib-Knit bonding pattern, as shown in Figure 12 of US5620779 of Levy etc., and the bonding area is about 15%. The film / nonwoven laminate is then wound on a winding roll operated at a speed of 0.47M / second (92fpm). The laminate wound is kept on a roll for more than 3 days. The laminate has a high retractive force and a 26% thermal shrinkage percentage.

[0072] Although the present invention has been described in detail with respect to its specific embodiments, it will be appreciated that those skilled in the art can easily conceive of alternatives, variants and equivalents of these embodiments after obtaining an understanding of the foregoing. Therefore, the scope of the present invention should be assessed as the scope of the appended claims and any equivalents thereof.

Claims

1. A method for preparing an elasticized product, comprising: melt extruding an extrudate having a polymer portion comprising greater than 90 weight percent of a semicrystalline olefin polymer; cooling the extrudate to form a film having a temperature between about 10° C. and about 50° C.; stretching the film to between 2 and 7 times its original length; bonding a support fabric to the membrane at intermittent points while the membrane is in a stretched state to form a composite material; winding the composite material onto a winding roll under tension so that the composite material shrinks to less than 80% of its length during the bonding step; aging the tensioned composite on the roller for at least 24 hours to form a heat shrinkable composite; attaching the heat-shrinkable composite material to at least one component of the article at two locations distal from each other and thereby forming distal attachment points; applying heat to the heat shrinkable composite material, wherein the composite material shrinks and acts to pull inwardly between the distal attachment points and move the distal attachment points closer to each other, thereby forming an elasticized area in the article, wherein the article comprises an absorbent personal care article having a liquid permeable body-facing topsheet, a liquid impermeable backsheet, and an absorbent core disposed between the topsheet and the backsheet, the heat shrinkable composite material being attached to at least one of the topsheet and the backsheet, and the polymer portion of the extrudate comprising at least 95% by weight of a semi-crystalline polyolefin polymer selected from a group consisting of polymers having a density between about 0.85 g / cm 3 and 0.89 g / cm 3 A semi-crystalline polymer of ethylene with a density between about 0.85 g / cm 3 and 0.89 g / cm 3 A semi-crystalline polymer of propylene.

2. The method of claim 1 wherein the extrudate comprises greater than 50 wt% propylene polymer, and further wherein the film is at a temperature between about 21°C and about 10°C when stretching begins.

3. The method of claim 1 wherein the extrudate comprises greater than 50 weight percent ethylene polymer, and further wherein the film is at a temperature between about 32°C and about 10°C when stretching begins.

4. The method of claim 1 wherein the polymer portion of the extrudate comprises at least about 95 weight percent of a semi-crystalline olefin polymer having a crystallinity between about 3% and about 30%.

5. The method of claim 1, wherein the heat shrinkable film shrinks between about 15% and about 50% when heat is applied to shrink the composite material and draw it inwardly between the distal attachment points.

6. An elasticized article prepared according to the method of any one of claims 1 to 5, the elasticized article comprising a heat-shrinkable composite material, the heat-shrinkable composite material comprising: an elastic film having said polymer portion and wherein said polymer portion comprises greater than 90 weight percent of a semi-crystalline polyolefin polymer; a support fabric intermittently bonded to the elastic membrane; The thermal shrinkage percentage of the composite material at 72° C. is greater than 15%.

7. The elasticized article of claim 6, wherein the polymer portion of the elastic film comprises at least 95% by weight of a semi-crystalline polyolefin polymer.

8. The elasticized article of claim 6, wherein the semi-crystalline polyolefin polymer comprises a density between about 0.85 g / cm 3 and 0.89 g / cm 3 Semi-crystalline polymers of ethylene with a density between about 0.85 g / cm 3 and 0.89 g / cm 3 A blend of semi-crystalline polymers of propylene.

9. The elasticized article of claim 8, wherein the ethylene semi-crystalline polymer comprises about 80 to 99 weight percent of the polymer portion of the film and the propylene semi-crystalline polymer comprises about 20 to 1 weight percent of the polymer portion of the film.

10. The elasticized article of claim 8, wherein the propylene semi-crystalline polymer comprises from about 80 wt% to 99 wt% of the polymer portion of the film and the ethylene semi-crystalline polymer comprises from about 20 wt% to about 1 wt% of the polymer portion of the film.

11. The elasticized article of claim 6, wherein the film further comprises between about 0.1 wt% and about 5 wt% filler particles.

12. The elasticized article of claim 6, wherein the film further comprises between about 0.1 wt% and 10 wt% of an olefin tackifier.

13. The elasticized article of claim 6, wherein the semi-crystalline polyolefin polymer has a latent heat of fusion of between about 15 J / g and about 75 J / g.

14. The elasticized article of claim 6, wherein the semi-crystalline polyolefin polymer has a crystallinity between about 3% and about 30%.

15. The elasticized article of claim 13, wherein the polymer portion of the elastic film comprises at least 98 weight percent of a semi-crystalline polyolefin polymer.

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