Patent Application
20120328841
This disclosure relates to vapor-permeable, substantially water-impermeable multilayer articles, as well as related products and methods.
Films that allow passage of gases at moderate to high transmission rates are often called breathable. The gases most commonly used to demonstrate a film's breathability are water vapor (also referred to herein as moisture vapor or moisture) and oxygen. The moisture vapor transmission test and oxygen transmission test measure the mass or volume of gas transported across the cross-section of a film in a given unit of time at a defined set of environmental conditions. Breathable films can be classified either as microporous films or monolithic films (which are not porous).
A breathable film can be laminated onto a nonwoven substrate to form a vapor-permeable, substantially water-impermeable multilayer article. A vapor-permeable, substantially water-impermeable multilayer article can refer to an article that allows the passage of a gas but substantially does not allow the passage of water.
The inventors have unexpectedly discovered that a vapor-permeable, substantially water-impermeable multilayer article containing a microporous breathable film (e.g., a film containing the same type of polymer used in the nonwoven substrate) between a monolithic breathable film and a nonwoven substrate can improve the adhesion of the monolithic breathable film to the nonwoven substrate while maintaining the moisture vapor transmission rate (MVTR) of the entire article. Such an article can be suitable for use as a construction material (e.g., a housewrap or a roofwrap).
In one aspect, this disclosure features an article that includes a nonwoven substrate, a first film supported by the nonwoven substrate, and a second film. The first film is between the nonwoven substrate and the second film, and includes a first polymer and a pore-forming filler. The difference between a surface energy of the first film and a surface energy of the nonwoven substrate is at most about 10 mN/m. The second film includes a second polymer capable of absorbing and desorbing moisture and providing a barrier to aqueous fluids.
In another aspect, this disclosure features an article that includes a nonwoven substrate, a first film supported by the nonwoven substrate, and a second film. The first film is between the nonwoven substrate and the second film and includes a first polymer and a pore-forming filler. The difference between a surface energy of the first film and a surface energy of the nonwoven substrate being at most about 10 mN/m. The second film includes a second polymer selected from the group consisting of maleic anhydride block copolymers, glycidyl methacrylate block copolymers, polyether block copolymers, polyurethanes, polyethylene-containing ionomers, and mixtures thereof.
In another aspect, this disclosure features an article that includes a nonwoven substrate, a first film supported by the nonwoven substrate, and a second film. The first film is between the nonwoven substrate and the second film, and includes a first polymer and a pore-forming filler. The first polymer includes a polyolefin or a polyester. The second film includes a second polymer selected from the group consisting of maleic anhydride block copolymers, glycidyl methacrylate block copolymers, polyether block copolymers, polyurethanes, polyethylene-containing ionomers, and mixtures thereof.
In another aspect, this disclosure features a constructive material (e.g., a housewrap or a roofwrap) that includes at least one of the articles described above.
In still another aspect, this disclosure features a method of making the article described above. The method includes (1) applying a first film and a second film onto a nonwoven substrate to form a laminate such that the first film is between the nonwoven substrate and the second film; and (2) stretching the laminate to form the article. The first film includes a first polymer and a pore-forming filler. The difference between a surface energy of the first film and a surface energy of the nonwoven substrate is at most about 10 mN-m. The second film includes a second polymer capable of absorbing and desorbing moisture and providing a barrier to aqueous fluids.
Embodiments can include one or more of the following optional features.
The second polymer is selected from the group consisting of maleic anhydride block copolymers (e.g., poly(olefin-co-acrylate-co-maleic anhydride) such as poly(ethylene-co-acrylate-co-maleic anhydride)), glycidyl methacryalte block copolymers (e.g., poly(olefin-co-acrylate-co-glycidyl methacrylate) such as poly(ethylene-co-acrylate-co-glycidyl methacrylate)), polyether block copolymers (e.g., polyether ester block copolymers, polyether amide block copolymers, or poly(ether ester amide) block copolymers), polyurethanes, polyethylene-containing ionomers, and mixtures thereof.
The second film can further include a polyolefin, such as a polyethylene or a polypropylene. Examples of polyethylene polymers include those selected from the group consisting of low-density polyethylene, linear low-density polyethylene, high-density polyethylene, and copolymers thereof.
The second film can further include a vinyl polymer. The vinyl polymer can include a copolymer formed between a first comonomer and a second comonomer, in which the first comonomer can include ethylene, and the second commoner can include alkyl methacrylate, alkyl acrylate, or vinyl acetate. Exemplary vinyl polymers include poly(ethylene-co-methyl acrylate), poly(ethylene-co-vinyl acetate), poly(ethylene-co-ethyl acrylate), and poly(ethylene-co-butyl acrylate).
The second film can further include a compatibilizer, such as polypropylene grafted with maleic anhydride (PP-g-MAH) or a polymer formed by reacting PP-g-MAH with a polyetheramine.
The second film can include at least about 20% by weight of the second polymer; at least about 10% by weight of the vinyl polymer; at least about 5% by weight of the polyolefin; and at least about 0.1% by weight of the compatibilizer, based on the weight of the second film.
The second film can further include a polyester, such as a polybutylene terephthalate, a polyethylene terephthalate, or a polytrimethylene terephthalate.
The first polymer can include a polyolefin (e.g., a polyethylene or a polypropylene) or a polyester (e.g., a polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polyglycolide, polylactide, polycaprolactone, polyethylene adipate, polyhydroxyalkanoate, or a copolymer thereof).
The pore-forming filler can include calcium carbonate. For example, the first film can include from about 30% by weight to about 70% by weight of the calcium carbonate.
The first film can further include a nanoclay, such as a montmorillonite clay.
The first film can further include an elastomer, such as a propylene-ethylene copolymer.
The first film can be from about 2% to about 98% of the total weight of the first and second films.
The nonwoven substrate can include randomly disposed polymeric fibers, at least some of the fibers being bonded to one another.
The article can have a moisture vapor transmission rate (MVTR) of at least about 35 g/m2/day when measured at 23° C. and 50 RH %.
The article can have a tensile strength of at least about 40 pounds in the machine direction and/or a tensile strength of at least about 35 pounds in the cross-machine direction as measured according to ASTM D5034.
The article can have a hydrostatic head of at least about 55 cm.
The article can be embossed.
The first and second films can be co-extruded onto the nonwoven substrate.
The laminate can be stretched at an elevated temperature (e.g., at least about 30° C.).
The laminate can be stretched in the machine direction or in the cross-machine direction.
The laminate can be stretched by a method selected from the group consisting of ring rolling, tentering, embossing, creping, and button-breaking.
The method can further include embossing the laminate prior to or after stretching the laminate.
The method can further include bonding randomly disposed polymeric fibers to produce the nonwoven substrate prior to forming the laminate.
Embodiments can provide the following advantage.
Without wishing to be bound by theory, it is believed that a vapor-permeable, substantially water-impermeable multilayer article containing a microporous breathable film (e.g., a film containing the same type of polymer used in the nonwoven substrate) between a monolithic breathable film and a nonwoven substrate can improve the adhesion of the monolithic breathable film to the nonwoven substrate while maintaining the MVTR of the entire article.
Other features and advantages of the invention will be apparent from the description, drawings, and claims.
Like reference symbols in the various drawings indicate like elements.
This disclosure relates to, for instance, an article (e.g., a vapor-permeable, substantially water-impermeable multilayer article) containing a microporous breathable film between a monolithic breathable film and a nonwoven substrate. The microporous breathable film can include a polymer and a pore-forming filler. The monolithic breathable film can include a polymer capable of absorbing and desorbing moisture and providing a barrier to aqueous fluids. The nonwoven substrate can be formed from polymeric fibers (e.g., fibers made from polyolefins).
Microporous breathable film 16 can include a polymer and a pore-forming filler.
The polymer used to form film 16 and the polymer forming the surface of nonwoven substrate 14 can be selected in such a manner that the difference between the surface energy of film 16 and that of nonwoven substrate 14 is at most about 10 mN/m (e.g., at most about 8 mN/m, at most about 6 mN/m, at most about 4 mN/m, at most about 2 mN/m, at most about 1 mN/m, or at most about 0.5 mN/m). In some embodiments, the surface energy of film 16 is substantially the same as that of nonwoven substrate 14. Without wishing to be bound by theory, it is believed that when the difference between the surface energy of film 16 and that of nonwoven substrate 14 is relatively small, the adhesion between the film 16 and nonwoven substrate can be significantly improved.
In some embodiments, film 16 can be made from a polyolefin or a polyester. In some embodiments, film 16 can include at least two (e.g., three, four, or five) polymers. In such embodiments, the difference between the surface energy of film 16 and that of that of nonwoven substrate 14 can be at most about 10 mN/m. As an example, when the polymer on the surface of nonwoven substrate 14 is a polyolefin (e.g., a polyethylene or polypropylene), the polymer used to form film 16 can also be a polyolefin (e.g., a polyethylene or polypropylene). As used here, the term “polyolefin” refers to a homopolymer or a copolymer made from a linear or branched, cyclic or acyclic alkene. Examples of polyolefins that can be used in film 16 include polyethylene, polypropylene, polybutene, polypentene, and polymethylpentene.
Polyethylene has been reported to have a surface energy of from about 35.3 mN/m to about 35.7 mN/m at 20° C. and polypropylene has been reported to have a surface energy of about 30 mN/m at 20° C. Thus, when both film 16 and nonwoven substrate 14 are made primarily from a polyethylene or polypropylene, the difference between the surface energy of film 16 and that of substrate 14 can range from about 0.5 mN/m to about 0 mN/m. When one of film 16 and substrate 14 is made primarily from a polyethylene and the other is made primarily from a polypropylene, the difference between the surface energy of film 16 and that of substrate 14 can range from about 5 mN/m to about 6 mN/m.
Exemplary polyethylene include low-density polyethylene (e.g., having a density from 0.910 g/cm2 to 0.925 g/cm2), linear low-density polyethylene (e.g., having a density from 0.910 g/cm2 to 0.935 g/cm2), and high-density polyethylene (e.g., having a density from 0.935 g/cm2 to 0.970 g/cm2). High-density polyethylene can be produced by copolymerizing ethylene with one or more C4 to C20 α-olefin co-monomers. Examples of suitable α-olefin co-monomers include 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, and combinations thereof. The high-density polyethylene can include up to 20 mole percent of the above-mentioned α-olefin co-monomers. In some embodiments, the polyethylene suitable for use in film 16 can have a melt index in the range of from about 0.1 g/10 min to about 10 g/10 min (e.g., from about 0.5 g/10 min to 5 g/10 min).
Polypropylene can be used in film 16 by itself or in combination with one or more of the polyethylene polymers described above. In the latter case, polypropylene can be either copolymerized or blended with one or more polyethylene polymers. Both polyethylene and polypropylene are available from commercial sources or can be readily prepared by methods known in the art.
In some embodiments, when the polymer forming the surface of nonwoven substrate 14 is a polyester (e.g., a polyethylene terephthalate), the polymer used to form film 16 can also be a polyester (e.g., a polyethylene terephthalate or a polybutylene terephthalate). Examples of polyesters that can be used in film 16 include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polyglycolide or polyglycolic acid (PGA), polylactide or polylactic acid (PLA), polycaprolactone (PCL), polyethylene adipate (PEA), polyhydroxyalkanoate (PHA), and copolymers thereof. As an example, polyethylene terephthalate has been reported to have a surface energy of about 44.6 mN/m at 20° C.
The amount of the polymer in film 16 can vary depending on the desired applications. For example, the polymer can be at least about 30% (e.g., at least about 35%, at least about 40%, at least about 45%, at least about 50%, or at least about 60%) and/or at most about 95% (e.g., at most about 90%, at most about 85%, at most about 80%, at most about 75%, or at most about 70%) of the total weight of film 16.
The pore-forming filler in film 16 can generate pores upon stretching (e.g., by using a ring-rolling process during the manufacture of multilayer article 10) to impart breathability to film 16 (i.e., to allow passage of vapor through film 16).
The pore-forming filler generally has a low affinity to and a lower elasticity than the polyolefin component or the other optional components. The pore-forming filler can be a rigid material. It can have a non-smooth surface, or have a surface treated to become hydrophobic.
In some embodiments, the pore-forming filler is in the form of particles. In such embodiments, the average value of the maximum linear dimension of the filler particles can be at least about 0.5 micron (at least about 1 micron or at least about 2 microns) and/or at most about 7 microns (e.g., at most about 5 microns or at most about 3.5 microns). Without wishing to be bound by theory, it is believed that filler particles with a relatively small average value of the maximum linear dimension (e.g., from about 0.75 microns to 2 microns) can provide a better balance of compoundability and breathability than filler particles with a relatively large average value of the maximum linear dimension.
The pore-forming filler in film 16 can be any suitable inorganic or organic material, or combinations thereof. Examples of the inorganic fillers include calcium carbonate, talc, clay, kaolin, silica diatomaceous earth, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium sulfate, aluminum hydroxide, zinc oxide, magnesium oxide, calcium oxide, magnesium oxide, titanium oxide, alumina, mica, glass powder, glass beads (hollow or non-hollow), glass fibers, zeolite, silica clay, and combinations thereof. In some embodiments, the pore forming filler in film 16 includes calcium carbonate. In some embodiments, the inorganic pore-forming filler can be surface treated to be hydrophobic so that the filler can repel water to reduce agglomeration of the filler. In addition, the pore-forming filler can include a coating on the surface to improve binding of the filler to the polyolefin in film 16 while allowing the filler to be pulled away from the polyolefin when film 16 is stretched or oriented (e.g., during a ring-rolling process). Exemplary coating materials include stearates, such as calcium stearate. Examples of organic fillers that can be used in film 16 include wood powder, pulp powder, and other cellulose type powders. Polymer powders such as TEFLON powder and KEVLAR powder can also be included as an organic pore forming filler. The pore forming fillers described above are either available from commercial sources or can be readily prepared by methods known in the art.
Film 16 can include a relatively high level of the pore-forming filler as long as the level of the filler does not undesirably affect the formation of film 16. For example, film 16 can include from at least about 5% (e.g., at least about 10%, at least about 20%, or at least about 30%) to at most about 70% (e.g., at most about 60%, at most about 50%, or at most about 40%) by weight of the pore-forming filler (e.g., calcium carbonate). In some embodiments, film 16 can include about 50% by weight of the pore-forming filler. Without wishing to be bound by theory, it is believed that, if film 16 does not include a sufficient amount (e.g., at least about 30% by weight) of the pore-forming filler, the film may not have an adequate moisture vapor transmission rate (MVTR) (e.g., at least about 35 g/m2/day when measured at 23° C. and 50 RH %). Further, without wishing to be bound by theory, it is believed that, if film 16 includes too much (e.g., more than about 70%) of the pore-forming filler, film 16 may not be uniform or may have a low tensile strength.
In some embodiments, film 16 can further include a functionalized polyolefin (e.g., functionalized polyethylene or polypropylene), such as a polyolefin graft copolymer. Examples of such polyolefin graft copolymers include polypropylene-g-maleic anhydride and polymers formed by reacting PP-g-MAH with a polyetheramine. In some embodiments, such a functionalized polyolefin can be used a compatibilizer to minimize the phase separation between the components in film 16 and/or to improve adhesion between film 16 and nonwoven substrate 14. The compatibilizer can be at least about 0.1% (e.g., at least about 0.2%, at least about 0.4%, at least about 0.5%, at least about) %, or at least about 1.5%) and/or at most about 30% (e.g., at most about 25%, at most about 20%, at most about 15%, at most about 10%, at most about 5%, at most about 4%, at most about 3%, or at most about 2%) of the total weight of film 16.
Optionally, film 16 can include an elastomer (e.g., a thermoplastic olefin elastomer) to improve the elasticity of the film. Examples of suitable elastomers include vulcanized natural rubber, ethylene alpha olefin rubber (EPM), ethylene alpha olefin diene monomer rubber (EPDM), styrene-isoprene-styrene (SIS) copolymers, styrene-butadiene-styrene (SBS) copolymers, styrene-ethylene-butylene-styrene (SEBS) copolymers, ethylene-propylene (EP) copolymers, ethylene-vinyl acetate (EVA) copolymers, ethylene-maleic anhydride (EMA) copolymers, ethylene-acrylic acid (EEA) copolymers, and butyl rubber. Commercial examples of such an elastomer include VERSIFY (i.e., an ethylene-propylene copolymer) available from Dow (Midland, Mich.) and LOTRYL (i.e., an ethylene-maleic anhydride copolymer) available from Arkema (Philadelphia, Pa.). Film 16 can include from about 5% (e.g., at least about 6% or at least about 7%) to at most about 30% (e.g., at most about 25%, at most about 20%, or at most about 15%) by weight of the elastomer. Without wishing to be bound by theory, it is believed that one advantage of using an elastomer in film 16 is that multilayer article 10 containing such a film can have both improved tensile strength (e.g., by at least about 5% or at least about 10%) and improved elongation (e.g., by at least about 20% or at least about 50%).
Further, film 16 can optionally include a nanoclay (e.g., montmorillonite nanoclay). Examples of nanoclays have been described in, e.g., U.S. Provisional Patent Application No. 61/498,328, entitled “Vapor Permeable, Substantially Water Impermeable Multilayer Article.”
Film 12 can include a breathable polymer capable of absorbing and desorbing moisture and providing a barrier to aqueous fluids (e.g., water). For example, the breathable polymer can absorb moisture from one side of film 12 and release it to the other side of film 12. As the breathable polymer imparts breathability to film 12, film 12 does not need to include pores. As such, film 12 can be monolithic and not porous. In addition, as film 12 can be co-extruded with film 16 onto nonwoven substrate 14, the extruded films thus obtained can have excellent adhesion between each other. Thus, film 12 does not need to have a surface energy similar to that of film 16 and can have any suitable surface energy.
In some embodiments, the breathable polymer in film 12 can include maleic anhydride block copolymers, glycidyl methacrylate block copolymers, polyether block copolymers, polyurethanes, polyethylene-containing ionomers, and mixtures thereof. Examples of maleic anhydride block copolymers include poly(olefin-co-acrylate-co-maleic anhydride), such as poly(ethylene-co-acrylate-co-maleic anhydride). Commercial examples of maleic anhydride block copolymers include LOTADER MAH available from Arkema and BYNEL available from E.I. du Pont de Nemours and Company, Inc. (Wilmington, Del.). Examples of glycidyl methacrylate block copolymers include poly(olefin-co-acrylate-co-glycidyl methacrylate), such as poly(ethylene-co-acrylate-co-glycidyl methacrylate). A commercial example of a glycidyl methacrylate block copolymer is LOTADER GMA available from Arkema.
Examples of polyether block copolymers include polyether ester block copolymers, polyether amide block copolymers, and poly(ether ester amide) block copolymers. Commercial examples of polyether ester block copolymers include ARNITEL available from DSM Engineering Plastics (Evansville, Ind.), HYTREL available from E.I. du Pont de Nemours and Company, Inc., and NEOSTAR available from Eastman Chemical Company (Kingsport, Tenn.). A commercial example of a polyether amide block copolymer is PEBAX available from Arkema.
A polyethylene-containing ionomer can include an ethylene copolymer moiety and an acid copolymer moiety. The ethylene copolymer moiety can be formed by copolymerizing ethylene and a monomer selected from the group consisting of vinyl acetate, alkyl acrylate, and alkyl methacrylate. The acid copolymer moiety can be formed by copolymerizing ethylene and a monomer selected from the group consisting of acrylic acid and methacrylic acid. The acidic groups in the polyethylene-containing ionomer can be partially or fully converted to salts that include suitable cations, such as Li+, Na+, K+, Mg2+, and Zn2+. Examples of polyethylene-containing ionomers include those described in U.S. Patent Application Publication Nos. 2009/0142530 and 2009/0123689. Commercial examples of polyethylene-containing ionomers include ENTIRA and DPO AD 1099 available from E.I. du Pont de Nemours and Company, Inc. (Wilmington, Del.).
Other suitable breathable polymers have been described in, for example, U.S. Pat. Nos. 5,800,928 and 5,869,414.
The amount of the breathable polymer in film 12 can vary depending on the desired applications. Film 12 can include an amount of the breathable polymer that is large enough to impart desired breathability to film 12 but small enough to minimize manufacturing costs. For example, the breathable polymer can be at least about 20% (e.g., at least about 25%, at least about 30%, at least about 35%, at least about 40%, or at least about 45%) and/or at most about 100% (e.g., at most about 90%, at most about 80%, at most about 70%, at most about 60%, or at most about 50%) of the total weight of film 12.
As breathable polymers can be expensive to manufacture, film 12 can optionally include a vinyl polymer to reduce costs while maintaining the properties of this film. The vinyl polymer can include a copolymer formed between a first comonomer and a second comonomer different from the first comonomer. Examples of the first comonomer can be olefins (such as ethylene or propylene). Examples of the second commoner can include alkyl methacrylate (e.g., methyl methacrylate), alkyl acrylate (e.g., methyl acrylate, ethyl acrylate, or butyl acrylate), and vinyl acetate. Examples of suitable vinyl polymers include poly(ethylene-co-methyl acrylate), poly(ethylene-co-vinyl acetate), poly(ethylene-co-ethyl acrylate), and poly(ethylene-co-butyl acrylate).
In some embodiments, film 12 can include at least about 10% (e.g., at least about 15%, at least about 20%, at least about 25%, at least about 30%, or at least about 40%) and/or at most about 70% (e.g., at most about 65%, at most about 60%, at most about 55%, at most about 50%, or at most about 45%) by weight of the vinyl polymer.
In some embodiments, when film 16 is made from a polyolefin, film 12 can optionally include a suitable amount of a polyolefin that is either the same as or similar to that in film 16 to improve adhesion between these two films. For example, the polyolefin in film 12 can be a polyethylene (e.g., a low-density polyethylene, a linear low-density polyethylene, a high density polyethylene, and a copolymer thereof), a polypropylene, or a mixture thereof. The amount of the polyolefin in film 12 can be at least about 5% (e.g., at least about 10%, at least about 15%, at least about 20%, at least about 25%, or at least about 30%) and/or at most about 60% (e.g., at most about 55%, at most about 50%, at most about 45%, at most about 40%, or at most about 35%) of the total weight of film 12. Similarly, when film 16 is made from a polyester or a mixture of polymers, film 12 can optionally include a suitable amount of a polyester (e.g., a polybutylene terephthalate, a polyethylene terephthalate, or a polytrimethylene terephthalate) or a mixture of polymers that are either the same as or similar to those in film 16.
When film 12 includes at least two polymers, it can optionally include a compatibilizer to improve the compatibility of the polymers (e.g., by reducing phase separation). The compatibilizer can be a functionalized polyolefin (e.g., functionalized polyethylene or polypropylene), such as a polyolefin graft copolymer. Examples of such polyolefin graft copolymers include polypropylene-g-maleic anhydride and a polymer formed by reacting PP-g-MAH with a polyetheramine. The compatibilizer can be at least about 0.1% (e.g., at least about 0.2%, at least about 0.4%, at least about 0.5%, at least about 1%, or at least about 1.5%) and/or at most about 5% (e.g., at most about 4.5%, at most about 4%, at most about 3.5%, at most about 3%, or at most about 2.5%) of the total weight of film 12.
The weight ratio between films 12 and 16 can vary depending on, e.g., the compositions of the films or the intended applications. In some embodiments, film 12 is from about 2% to about 98% (e.g., from about 5% to about 95%, from about 10% to about 90%, from about 20% to about 80%, or from about 40% to about 60%) of the total weight of films 12 and 16.
Without wishing to be bound by theory, it is believed that a vapor-permeable, substantially water-impermeable multilayer article containing microporous breathable film 16 (e.g., containing the same type of polymer used in the nonwoven substrate) between monolithic breathable film 12 and nonwoven substrate 14 can improve the adhesion of film 12 to nonwoven substrate 14 while maintaining the MVTR of the entire article.
Nonwoven substrate 14 can include randomly disposed polymeric fibers, at least some of the fibers being bonded to one another. As used herein, the term “nonwoven substrate” refers to a substrate containing one or more layers of fibers that are bonded together, but not in an identifiable manner as in a knitted or woven material.
Nonwoven substrate 14 can be formed from any suitable polymers. Exemplary polymers that can be used to form nonwoven substrate 14 include polyolefins and polyesters. Examples of suitable polyolefins include polyethylene, polypropylene, and copolymers thereof, such as those in film 12 described above. Examples of suitable polyesters include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polyglycolide or polyglycolic acid (PGA), polylactide or polylactic acid (PLA), polycaprolactone (PCL), polyethylene adipate (PEA), polyhydroxyalkanoate (PHA), and copolymers thereof.
Nonwoven substrate 14 can be formed from single component fibers, i.e., fibers containing a polymer having a single chemical structure (e.g., a polymer described in the preceding paragraph such as a polyethylene, a polypropylene, or a polyethylene terephthalate). In some embodiments, nonwoven substrate 14 can include single component fibers made from polymers having the same chemical structure but different characteristics (e.g., molecular weights, molecular weight distributions, density, or intrinsic viscosities). For example, substrate 14 can include a mixture of a low density polyethylene and a high density polyethylene. Such fibers are still referred to as single component fibers in this disclosure.
Nonwoven substrate 14 can also be formed from multicomponent fibers, i.e., fibers containing polymers with different chemical structures (such as two different polymers described above). For example, substrate 14 can be formed from a mixture of a polypropylene and a polyethylene terephthalate. In some embodiments, a multicomponent fiber can have a sheath-core configuration (e.g., having a polyethylene terephthalate as the core and a polypropylene as the sheath). In some embodiments, a multicomponent fiber can include two or more polymer domains in a different configuration (e.g., a side-by-side configuration, a pie configuration, or an “islands-in-the-sea” configuration).
In some embodiments, the surface of nonwoven substrate 14 can be formed of a polymer having a chemical structure similar to (e.g., the same type as) or the same as the chemical structure of a polymer in the surface of film 16. As an example, a polyolefin (e.g., a polyethylene or propylene) is of the same type as and similar to a different polyolefin (e.g., a polyethylene or propylene). Without wishing to be bound by theory, it is believed that such two layers can have improved adhesion. For example, when nonwoven substrate 14 is formed from single component fibers, the fibers can be made from a polyolefin, which has a chemical structure similar to or the same as a polyolefin that is used to make film 16. When nonwoven substrate 14 is formed of multicomponent fibers (e.g., having a sheath-core configuration), the polymer (e.g., a polyolefin in the sheath) in the fibers that contacts film 16 can have a chemical structure similar to or the same as the chemical structure of a polyolefin in film 16. Both examples described above can result in a multilayer article with improved adhesion between the film and the nonwoven substrate.
Nonwoven substrate 14 can be made by methods well known in the art, such as a spunlacing, spunbonding, meltblowing, carding, air-through bonding, or calendar bonding process.
In some embodiments, nonwoven substrate 14 can be a spunbonded nonwoven substrate. In such embodiments, nonwoven substrate 14 can include a plurality of random continuous fibers, at least some (e.g., all) of which are bonded (e.g., area bonded or point bonded) with each other through a plurality of intermittent bonds. The term “continuous fiber” mentioned herein refers to a fiber formed in a continuous process and is not shortened before it is incorporated into a nonwoven substrate containing the continuous fibers.
As an example, nonwoven substrate 14 containing single component fibers can be made by using a spunbonding process as follows.
After the polymer for making single component fibers is melted, the molten polymer can be extruded from an extruding device. The molten polymer can then be directed into a spinneret with composite spinning orifices and spun through this spinneret to form continuous fibers. The fibers can subsequently be quenched (e.g., by cool air), attenuated mechanically or pneumatically (e.g., by a high-velocity fluid), and collected in a random arrangement on a surface of a collector (e.g., a moving substrate such as a moving wire or belt) to form a nonwoven web. In some embodiments, a plurality of spinnerets with different quenching and attenuating capability can be used to place one or more (e.g., two, three, four, or five) layers of fibers on a collector to form a substrate containing one or more layers of spunbonded fibers (e.g., an S, SS, or SSS type of substrate). In some embodiments, one or more layers of meltblown fibers can be inserted between the layers of the above-described spunbonded fibers to form a substrate containing both spunbonded and meltblown fibers (e.g., an SMS, SMMS, or SSMMS type of substrate).
A plurality of intermittent bonds can subsequently be formed between at least some of the fibers (e.g., all of the fibers) randomly disposed on the collector to form a unitary, coherent, nonwoven substrate. Intermittent bonds can be formed by a suitable method such as mechanical needling, thermal bonding, ultrasonic bonding, or chemical bonding. Bonds can be covalent bonds (e.g., formed by chemical bonding) or physical attachments (e.g., formed by thermal bonding). In some embodiments, intermittent bonds are formed by thermal bonding. For example, bonds can be formed by known thermal bonding techniques, such as point bonding (e.g., using calender rolls with a point bonding pattern) or area bonding (e.g., using smooth calender rolls without any pattern). Bonds can cover between about 6 percent and about 40 percent (e.g., between about 8 percent and about 30 percent or between about 22 percent and about 28 percent) of the total area of nonwoven substrate 14. Without wishing to be bound by theory, it is believed that forming bonds in substrate 14 within these percentage ranges allows elongation throughout the entire area of substrate 14 upon stretching while maintaining the strength and integrity of the substrate.
Optionally, the fibers in nonwoven substrate 14 can be treated with a surface-modifying composition after intermittent bonds are formed. Methods of applying a surface-modifying composition to the fibers have been described, for example, in U.S. Provisional Patent Application No. 61/294,328.
The nonwoven substrate thus formed can then be used to form multilayer article 10 described above. A nonwoven substrate containing multicomponent fibers can be made in a manner similar to that described above. Other examples of methods of making a nonwoven substrate containing multicomponent fibers have been described in, for example, U.S. Provisional Patent Application No. 61/294,328.
Multilayer article 10 can be made by the methods known in the art or the methods described herein. For example, multilayer article 10 can be made by first applying films 12 and 16 onto nonwoven substrate 14 to form a laminate. Films 12 and 16 can be applied onto nonwoven substrate 14 by co-extruding (e.g., cast extrusion) a suitable composition for film 12 (e.g., a composition containing a breathable polymer) and a suitable composition for film 16 (e.g., a composition containing a polyolefin and a pore forming filler) at an elevated temperature to form two layers of films onto nonwoven substrate 14. In some embodiments, the just-mentioned compositions can be co-extruded (e.g., by tubular extrusion or cast extrusion) to form a web, which can be cooled (e.g., by passing through a pair of rollers) to form a precursor two-layer film. A laminate can then be formed by attaching the precursor film to nonwoven substrate 14 by using, for example, an adhesive (e.g., a spray adhesive, a hot melt adhesive, or a latex based adhesive), thermal bonding, ultra-sonic bonding, or needle punching.
In some embodiments, multilayer article 10 can include multiple (e.g., two, three, four, or five) films supported by nonwoven substrate 14, wherein at least two of the films are films 12 and 16 described above. The additional films can be made by one or more of the materials used to prepare film 12 or 16 described above or other materials known in the art. In some embodiments, nonwoven substrate 14 can be disposed between two of the multiple films. In some embodiments, all of the films can be disposed on one side of nonwoven substrate 14.
The laminate formed above can then be stretched (e.g., incrementally stretched or locally stretched) to form a vapor-permeable, substantially water-impermeable multilayer article 10. Without wishing to be bound by theory, it is believed that stretching the laminate generates pores around the pore-forming filler in film 16 that render this film breathable (i.e., allowing air and/or water vapor to pass through), but does not generate pores in film 12. The laminate can be stretched (e.g., incrementally stretched) in the machine direction (MD) or the cross-machine direction (CD) or both (biaxially) either simultaneously or sequentially. As used herein, “machine direction” refers to the direction of movement of a nonwoven material during its production or processing. For example, the length of a nonwoven material can be the dimension in the machine direction. As used herein, “cross-machine direction” refers to the direction that is essentially perpendicular to the machine direction defined above. For example, the width of a nonwoven material can be the dimension in the cross-machine direction. Examples of incremental-stretching methods have been described in, e.g., U.S. Pat. Nos. 4,116,892 and 6,013,151.
Exemplary stretching methods include ring rolling (in the machine direction and/or the cross-machine direction), tentering, embossing, creping, and button-breaking. These methods are known in the art, such as those described in U.S. Pat. No. 6,258,308 and U.S. Provisional Application No. 61/294,328.
In some embodiments, the laminate described above can be stretched (e.g., incrementally stretched) at an elevated temperature as long as the polymers in the laminate maintain a sufficient mechanical strength at that temperature. The elevated temperature can be at least about 30° C. (e.g., at least about 40° C., at least about 50° C., or at least about 60° C.) and/or at most about 100° C. (e.g., at least about 90° C., at least about 80° C., or at least about 70° C.). Without wishing to be bound by theory, it is believed that stretching the laminate described above at an elevated temperature can soften the polymers in films 12 and 16 and nonwoven substrate 14, and therefore allow these polymers to be stretched easily. In addition, without wishing to be bound by theory, it is believed that stretching the laminate described above at an elevated temperature can increase the MVTR by increasing the number of the pores in film 16, rather than the size of the pores (which can reduce the hydrostatic head (i.e., resistance of water) of the multilayer article). As a result, it is believed that stretching the laminate described above at an elevated temperature can unexpectedly improve the MVTR of the resultant multilayer article while still maintaining an appropriate hydrostatic head of the multilayer article. In certain embodiments, the laminate described above can be stretched (e.g., incrementally stretched) at an ambient temperature (e.g., at about 25° C.).
In some embodiments, the laminate described above can be embossed prior to or after being stretched (e.g., by using a calendering process). For example, the laminate can be embossed by passing through a pair of calender rolls in which one roll has an embossed surface and the other roll has a smooth surface. Without wishing to be bound by theory, it is believed that an embossed multilayer article can have a large surface area, which can facilitate vapor transmission through the multilayer article. In some embodiments, at least one (e.g., both) of the calender rolls is heated, e.g., by circulating a hot oil through the roll.
Without wishing to be bound by theory, it is believed that the adhesion between film 16 and nonwoven substrate 14 is significantly higher than that between film 12 and nonwoven substrate. For example, the adhesion between film 16 and nonwoven substrate 14 can be at least about 200 gram-force/in (e.g., at least about 300 gram-force/in, at least about 500 gram-force/in, at least about 1,000 gram-force/in, or at least about 1,500 gram-force/in). By contrast, the adhesion between film 12 and nonwoven substrate 14 can be at most about 200 gram-force/in (e.g., at most about 150 gram-force/in, at most about 100 gram-force/in, at most about 50 gram-force/in, or at most about 10 gram-force/in).
In some embodiments, multilayer article 10 can have a suitable MVTR based on its intended uses. As used herein, the MVTR values are measured according to ASTM E96-A. For example, multilayer article 10 can have a MVTR of at least about 35 g/m2/day (e.g., at least about 50 g/m2/day, at least about 75 g/m2/day, or at least about 100 g/m2/day) and/or at most about 140 g/m2/day (e.g., at most about 130 g/m2/day, at most about 120 g/m2/day, or at most about 110 g/m2/day) when measured at 23° C. and 50 RH %. Multilayer article 10 can have a MVTR of between 70 g/m2/day and 140 g/m2/day.
In some embodiments, multilayer article 10 can have a sufficient tensile strength in the machine direction and/or the cross-machine direction. The tensile strength is determined by measuring the tensile force required to rupture a sample of a sheet material. The tensile strength mentioned herein is measured according to ASTM D5034 and is reported in pounds. In some embodiments, multilayer article 10 can have a tensile strength of at least about 40 pounds (e.g., at least about 50 pounds, at least about 60 pounds, at least about 70 pounds, or at least about 80 pounds) and/or at most about 160 pounds (e.g., at most about 150 pounds, at most about 140 pounds, at most about 130 pounds, or at most about 120 pounds) in the machine direction. In some embodiments, multilayer article 10 can have a tensile strength of at least about 35 pounds (e.g., at least about 40 pounds, at least about 50 pounds, at least about 60 pounds, or at least about 70 pounds) and/or at most about 140 pounds (e.g., at most about 130 pounds, at most about 120 pounds, at most about 110 pounds, or at most about 100 pounds) in the cross-machine direction.
As a specific example, when multilayer article 10 has a unit weight of 1.25 ounce per square yard, it can have a tensile strength of at least about 40 pounds (e.g., at least about 45 pounds, at least about 50 pounds, at least about 55 pounds, or at least about 60 pounds) and/or at most about 100 pounds (e.g., at most about 95 pounds, at most about 90 pounds, at most about 85 pounds, or at most about 80 pounds) in the machine direction, and at least about 35 pounds (e.g., at least about 40 pounds, at least about 45 pounds, at least about 50 pounds, or at least about 55 pounds) and/or at most about 95 pounds (e.g., at most about 90 pounds, at most about 85 pounds, at most about 80 pounds, or at most about 75 pounds) in the cross-machine direction.
In some embodiments, multilayer article 10 can have a sufficient elongation in the machine direction and/or the cross-machine direction. Elongation is a measure of the amount that a sample of a sheet material will stretch under tension before the sheet breaks. The term “elongation” used herein refers to the difference between the length just prior to break and the original sample length, and is expressed as a percentage of the original sample length. The elongation values mentioned herein are measured according to ASTM D5034. For example, multilayer article 10 can have an elongation of at least about 5% (e.g., at least about 10%, at least about 20%, at least about 30%, at least about 35%, or at least about 40%) and/or at most about 100% (e.g., at most 90%, at most about 80%, or at most about 70%) in the machine direction. As another example, multilayer article 10 can have an elongation of at least about 5% (e.g., at least about 10%, at least about 20%, at least about 30%, at least about 35%, or at least about 40%) and/or at most about 100% (e.g., at most about 90%, at most about 80%, or at most about 70%) in the cross-machine direction.
In some embodiments, multilayer article 10 can have a sufficient hydrostatic head value so as to maintain sufficient water impermeability. As used herein, the term “hydrostatic head” refers to the pressure of a column of water as measured by its height that is required to penetrate a given material and is determined according to AATCC 127. For example, multilayer article 10 can have a hydrostatic head of at least about 55 cm (e.g., at least about 60 cm, at least about 70 cm, at least about 80 cm, at least about 90 cm, or at least about 100 cm) and/or at most about 900 cm (e.g., at most about 800 cm, at most about 600 cm, at most about 400 cm, or at most about 200 cm).
Multilayer article 10 can be used in a consumer product with or without further modifications. Examples of such consumer products include construction materials, such as a housewrap or a roofwrap. Other examples include diapers, adult incontinence devices, feminine hygiene products, medical and surgical gowns, medical drapes, and industrial apparels.
While certain embodiments have been disclosed, other embodiments are also possible.
In some embodiments, an effective amount of various additives can be incorporated in film 12, film 16, or nonwoven substrate 14. Suitable additives include pigments, antistatic agents, antioxidants, ultraviolet light stabilizers, antiblocking agents, lubricants, processing aids, waxes, coupling agents for fillers, softening agents, thermal stabilizers, tackifiers, polymeric modifiers, hydrophobic compounds, hydrophilic compounds, anticorrosive agents, and mixtures thereof. In certain embodiments, additives such as polysiloxane fluids and fatty acid amides can be included to improve processability characteristics.
Pigments of various colors can be added to provide the resultant multilayer article 10 that is substantially opaque and exhibits uniform color. For example, multilayer article 10 can have a sufficient amount of pigments to produce an opacity of at least about 85% (e.g., at least about 90%, at least about 95%, at least about 98%, or at least about 99%). Suitable pigments include, but are not limited to, antimony trioxide, azurite, barium borate, barium sulfate, cadmium pigments (e.g., cadmium sulfide), calcium chromate, calcium carbonate, carbon black, chromium(III) oxide, cobalt pigments (e.g., cobalt(II) aluminate), lead tetroxide, lead(II) chromate, lithopone, orpiment, titanium dioxide, zinc oxide and zinc phosphate. Preferably, the pigment is titanium dioxide, carbon black, or calcium carbonate. The pigment can be about 1 percent to about 20 percent (e.g., about 3 percent to about 10 percent) of the total weight of film 12, film 16, or nonwoven substrate 14. Alternatively, the pigment can be omitted to provide a substantially transparent multilayer article.
In some embodiments, certain additives can be used to facilitate manufacture of multilayer article 10. For example, antistatic agents can be incorporated into film 12, film 16, or nonwoven substrate 14 to facilitate processing of these materials. In addition, certain additives can be incorporated in multilayer article 10 for specific end applications. For example, anticorrosive additives can be added if multilayer article 10 is to be used to package items that are subject to oxidation or corrosion. As another example, metal powders can be added to provide static or electrical discharge for sensitive electronic components such as printed circuit boards.
Each of film 12, film 16, and nonwoven substrate 14 can also include a filler. The term “filler” can include non-reinforcing fillers, reinforcing fillers, organic fillers, and inorganic fillers. For example, the filler can be an inorganic filler such as talc, silica, clays, solid flame retardants, Kaolin, diatomaceous earth, magnesium carbonate, barium carbonate, magnesium sulfate, calcium sulfate, aluminum hydroxide, zinc oxide, magnesium hydroxide, calcium oxide, magnesium oxide, alumina, mica, glass powder, ferrous hydroxide, zeolite, barium sulfate, or other mineral fillers or mixtures thereof. Other fillers can include acetyl salicylic acid, ion exchange resins, wood pulp, pulp powder, borox, alkaline earth metals, or mixtures thereof. The filler can be added in an amount of up to about 60 weight percent (e.g., from about 2 weight percent to about 50 weight percent) of film 12, film 16, or nonwoven substrate 14.
In some embodiments, the surface of film 12, film 16, or nonwoven substrate 14 can be at least partially treated to promote adhesion. For example, the surface of film 12, film 16, or nonwoven substrate 14 can be corona charged or flame treated to partially oxidize the surface and enhance surface adhesion. Without wishing to be bound by theory, it is believed that multilayer article 10 having enhanced surface adhesion can enable printing on its surface using conventional inks Ink-jet receptive coating can also be added to the surface of multilayer article 10 to allow printing by home or commercial ink-jet printers using water based or solvent based inks.
The following examples are illustrative and not intended to be limiting.
The following two multilayer articles were prepared: (1) TYPAR (i.e., a polypropylene spunbonded nonwoven substrate available from Fiberweb, Inc.) having a unit weight of 1.9 ounce per square inch and coated with a monolithic breathable film containing 40 wt % LOTADER, 56 wt % ethyl methacrylate, 2 wt % TiO2, and 2 wt % UV stabilizer, and (2) a multilayer article similar to multilayer article (1) except that it contained a microporous breathable film between the TYPAR and the monolithic breathable film, where the microporous breathable film included 50 wt % calcium carbonate (i.e., a pore-forming filler), 41 wt % polypropylene, 5 wt % low-density polyethylene, 2 wt % TiO2, and 2 wt % UV stabilizer. Multilayer article (1) was formed by extruding the monolithic breathable film onto TYPAR at 480° F. Multilayer article (2) was formed by co-extruding the microporous breathable film and the monolithic breathable film onto TYPAR at the same temperature. Multilayer articles (1) and (2) had total film unit weights of 22 gsm and 27 gsm, respectively.
Multilayer article (1) and (2) were evaluated for their MVTR and the adhesion between the nonwoven substrate and the film(s). The MVTR was measured by using ASTM E96-A. The adhesion was measured as follows: 9-inch long samples were prepared by adhering a 2-inch wide housewrap tape over the coating (folding over one end of the tape onto itself to provide a tab for gripping) to prevent elongation of the coating. The peel adhesion of the samples was then measured by using an Instron or IMASS peel tester with a 5-pound load cell. A 180 degree peel angel was used with a rate of separation of 12 in/minute. The test results are summarized in Table 1 below.
The results showed that, although multilayer article (1) had an adequate MVTR, it exhibited poor adhesion between the nonwoven substrate and the monolithic breathable film. Unexpectedly, multilayer article (2) exhibited superior adhesion between the microporous breathable film and the nonwoven substrate while maintaining the MVTR of the multilayer article.
Multilayer articles (3) and (4) were prepared in the same manner as described in Example 1. Multilayer article (3) was similar to multilayer article (1) except that it included a monolithic breathable film containing 45 wt % PEBAX MV3000, 50 wt % LOTRYL 20MA08, and 5 wt % BYNEL 22E757. Multilayer article (4) was similar to multilayer article (2) except that it included a monolithic breathable film containing 45 wt % PEBAX MV3000 and 55 wt % LOTRYL 20MA08.
Multilayer article (3) and (4) were evaluated for their MVTR and the adhesion between the nonwoven substrate and the film(s) using the same methods described in Example 1. The results are summarized in Table 2 below.
The results showed that, although multilayer article (3) had an adequate MVTR, it exhibited poor adhesion between the nonwoven substrate and the monolithic breathable film. Unexpectedly, multilayer article (4) exhibited superior adhesion between the microporous breathable film and the nonwoven substrate while maintaining the MVTR of the multilayer article.
Other embodiments are in the claims.
This application claims priority to U.S. Provisional Patent Application No. 61/500,476 filed Jun. 23, 2011, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61500476 | Jun 2011 | US |
