KR20130137008A - Nonwoven composite including regenerated cellulose fibers - Google Patents

Abstract

The present invention provides a soft, bulky, absorbent hydroentangled nonwoven fabric comprising regenerated cellulose fibers and staple or wood pulp fibers, and a method of making the same, the method comprising: a) regenerated cellulose on a forming surface Arranging the fibers, b) depositing staples or wood pulp fibers on the regenerated cellulose fibers, and c) hydroentangling the regenerated cellulose fibers and staples or wood pulp fibers together to form a hydroentangled composite. And d) drying the hydroentangled composite, and then e) creping the hydroentangled composite with a foamed creping solution or dispersion.

Description

Nonwoven composite comprising regenerated cellulose fibers {NONWOVEN COMPOSITE INCLUDING REGENERATED CELLULOSE FIBERS}

Cross Reference of Related Application

This application claims the benefit of US patent application Ser. No. 12/979852, filed December 28, 2010, the entirety of which is incorporated herein by reference.

Hydroentangled nonwoven composites having hydraulically entangled absorbent fibers with synthetic fiber webs are known in the art, see, for example, US Pat. No. 4,808,467 to Suskind and US Pat. It is considered in various patents and publications, including 5,284,703. Hydroentangled nonwoven composites formed from absorbent fibers entangled with synthetic fiber webs are known in the art to be durable, wear resistant and still absorbent.

These hydroentangled nonwoven composites can be creped to increase the volume and ductility of the hydroentangled nonwoven composites. However, during the creping process, the heat from the creping dryer can have a detrimental effect on synthetic fibers such as polypropylene fibers, where softening and melting may occur at drying temperatures. As a result, there is a need in the art for hydroentangled nonwoven composites that are more suitable for creping at higher temperatures.

In one embodiment, a direct-molded nonwoven comprising regenerated cellulose fibers and staple or wood pulp fibers is formed by the following steps: a) placing regenerated cellulose fibers on a forming surface, b) regeneration Depositing staples or wood pulp fibers on cellulose fibers, c) hydroentangling the regenerated cellulose fibers and staples or wood pulp fibers together to form a hydroentangled composite, d) drying the hydroentangled composites And then e) creping the hydroentangled composite with a foamed creping solution or dispersion. In one embodiment, the regenerated cellulose fibers may have a basis weight of about 10 to about 20 grams per square meter. In another embodiment, the regenerated cellulose fibers may be continuous fibers. In another embodiment, the staple or wood pulp fibers have a basis weight of about 30 to about 150 grams per square meter.

In one aspect, the creping step comprises the steps of: a) positioning the additive composition applicator adjacent to the hot impermeable dryer surface, b) applying a foamed dispersion or foamed solution comprising the additive composition to the dryer surface; c) converting the foamed dispersion or foamed solution into an adhesive film, d) directly bonding the hydroentangled composite to the adhesive film, and e) the hydroentangled composite and adhesive bonded from the dryer surface. And scraping the film. In one embodiment, the additive composition may further comprise a blowing agent. In another embodiment, the additive composition may comprise a hydroxypropyl cellulose solution. In one embodiment, the high temperature impermeable dryer surface may have a temperature above about 300 ° F., optionally between about 500 ° F. and about 550 ° F. In other embodiments, the adhesive film may be a substantially continuous adhesive film.

In another embodiment, the integrated composite fabric comprises more than about 5 weight percent and less than about 30 weight percent continuous regenerated cellulose filaments and more than about 70 weight percent and less than about 95 weight percent wood pulp fibers. In one embodiment, the integrated composite fabric may have an absorption capacity of greater than 5.6 g / g. In other embodiments, the integrated composite fabric may have at least 4 logs softness than similar integrated composite fabrics having polypropylene filaments instead of regenerated cellulose filaments. In other embodiments, the wood pulp fibers may be discontinuous fibers. In another embodiment, the continuous regenerated cellulose filament is a Lyocell filament. In another embodiment, the continuous regenerated cellulose filament may be a spunbond filament.

In another embodiment, a method of making a direct-molded nonwoven comprising regenerated cellulose fibers and wood pulp fibers comprises a) placing regenerated cellulose fibers on a forming surface, and b) depositing wood pulp fibers on regenerated cellulose fibers. C) hydroentangling regenerated cellulose fibers and wood pulp fibers together to form a hydroentangled composite, d) drying the hydroentangled composite, and then e) foamed creping. Creping the hydroentangled complex with a solution or dispersion. In another embodiment, the regenerated cellulose fibers may be continuous fibers.

In another embodiment, the creping step includes a) positioning an additive composition applicator adjacent to the hot impermeable dryer surface, and b) applying a foamed dispersion or foamed solution comprising the additive composition to the dryer surface; c) converting the foamed dispersion or foamed solution into an adhesive film, d) directly bonding the hydroentangled composite to the adhesive film, and e) the hydroentangled composite bound from the dryer surface. And scraping the adhesive film. In one embodiment, the additive composition may further comprise a blowing agent. In another embodiment, the additive composition may comprise a hydroxypropyl cellulose solution. In one embodiment, the high temperature impermeable dryer surface may have a temperature above about 300 ° F., optionally between about 500 ° F. and about 550 ° F. In other embodiments, the adhesive film may be a substantially continuous adhesive film.

1 illustrates an exemplary process for preparing the nonwoven composite of the present invention.

Justice

As used herein, the term “staple fiber” refers to discontinuous fibers made of regenerated cellulose or synthetic polymers such as polypropylene, polyester, post consumer recycle (PCR) fibers, polyester, nylon, and the like. However, non-hydrophilic ones can be treated to be hydrophilic. The staple fiber may be chopped fiber or the like. Staple fibers may have a cross section that is round, bicomponent, multicomponent, molded, hollow, or the like. Typical staple fiber lengths used in the present invention are 3 to 12 mm in length and have deniers of 1 to 6 dpf (denier per fiber).

As used herein, the term "pulp fiber" refers to fibers from natural sources such as woody and non-woody plants. Wood fibers include, for example, hardwoods and conifers. Non-woody plants include, for example, cotton, flax, esparto grass, milkweed, straw, jute hemp and bagasse.

As used herein, the term "nonwoven web" refers to a web having a structure of individual fibers or threads that are interleaved but interleaved in a manner that can be identified as a knitted fabric. Nonwoven webs are formed by a number of processes such as, for example, meltblowing processes, spunbonding processes, and bonded carded web processes. The basis weight of a nonwoven web is typically expressed in ounces of material per square yard (osy) or grams per square meter (gsm), and the fiber diameter is typically expressed in microns or denier per fiber (dpf). Note that to convert from to gsm, we multiply osy by 33.91).

As used herein, the term "microfiber" is a small diameter fiber having an average diameter of about 75 microns or less, such as from about 0.5 microns to about 50 microns, or in particular, the microfibers from about 0.5 microns to about 40 It can have an average diameter of microns. Another frequently used expression of fiber diameter is denier, which is defined as grams per 9000 meters of fiber. As an example, the diameter of a polypropylene fiber given in microns can be converted to denier by squared and multiplying the result by 0.00629, thus the 15 micron polypropylene fiber has a denier of about 1.42 (15 ² x 0.00629 = 1.415) .

As used herein, the term “spunbond” refers to, for example, US Pat. No. 4,340,563 to Appel et al., US Pat. No. 3,692,618 to Dorschner et al., US Pat. No. 3,802,817 to Matsuki et al., US Pat. No. 3,338,992 to Kinney, and Spinning nozzles in which the diameter of the extruded filaments is drastically reduced after extrusion, such as by processes disclosed in US Pat. No. 3,341,394, US Pat. No. 3,502, 538 to Levy, US Pat. No. 3,502,763 to Hartman, and US Pat. refers to a process by which small diameter fibers are formed by extruding molten thermoplastic material as filaments from a plurality of fine, generally circular capillaries of a spinnerette). Spunbond fibers are generally continuous and have a diameter of greater than 7 microns, in particular between about 10 and 30 microns. Spunbond fibers are generally not tacky when they are deposited on a collecting surface.

As used herein, the term “meltblown” is a thread melted into a converging fast gas (eg air) stream that attenuates filaments of molten thermoplastic material to reduce its diameter, which may be a microfiber diameter. Or as a filament, a process in which fibers are formed by extruding a molten thermoplastic material through a plurality of fine, generally circular die capillaries. The meltblown fibers are then carried by the high velocity gas stream and deposited on a collecting surface to form a web of optionally dispensed meltblown fibers. Such a process is disclosed, for example, in US Pat. No. 3,849,241 to Butin. Meltblown fibers can be continuous or discontinuous and are generally microfibers smaller than 10 microns in diameter.

As used herein, the term "melt spun" includes "spunbond" or "meltblown" and may or may not include a bond.

As used herein, the term "bonded carded web" is known to those of skill in the art and is formed by a carding process described further in US Pat. Refers to nonwoven webs. In the carding process, blends of other components such as staple fibers, binding fibers and possibly adhesives can be used. These components are formed into bulky balls that have been combed or otherwise treated to produce a substantially uniform basis weight. This web is heated or otherwise processed to activate any adhesive component resulting in an integrated, non-woven material.

As used herein, the term “creping” refers to when the polymer adhered to the web is scraped from the dryer surface (eg, Yankee dryer surface) with a doctor blade. By way of example, the foam composition can be applied to a heated drier to evaporate water from the foam composition. The heat of the dryer turns the foam composition into a polymer film. Using a compressive force, the web is in contact with the film on the surface of the dryer, so it is attached to it prior to creping.

As used herein, the term "forth" is a liquid foam. When the foamable composition is heated, it does not form a solid foam structure. Instead, when applied to a heated surface, the foamable composition is converted into a substantially continuous film.

As used herein, the terms “comprises”, “comprising” and other derivatives from the other source term “comprises” refer to the presence of any declared feature, element, integral, step, or component. It is intended to be an open end term and not to exclude the addition or presence of one or more other features, elements, integrals, steps, components or groups thereof.

Those skilled in the art should understand that the description is merely illustrative of exemplary embodiments and is not intended to limit the broader aspects of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a nonwoven web composite comprising fibers comprising regenerated cellulose and hydroentangled short fibers and fibers comprising regenerated cellulose.

In one embodiment of the present invention, the nonwoven composite web of the present invention comprises a nonwoven web of continuous fibers comprising regenerated cellulose and a layer of hydroentangled discontinuous fibers and a nonwoven web of continuous fibers comprising regenerated cellulose to form a nonwoven composite. It is prepared from. Alternatively, the nonwoven composite web of the present invention may be prepared from a nonwoven web of discontinuous fibers comprising regenerated cellulose and a layer of other discontinuous fibers hydroentangling and a nonwoven web of discontinuous fibers comprising regenerated cellulose to form a nonwoven composite. Can be.

Regenerated cellulose fibers are well known in the art. There are a number of processes available for the production of regenerated cellulose fibers. By way of example, viscose rayon is a regenerated cellulose fiber prepared by a process comprising the step of steeping cellulose with mercerizing strength caustic soda solution to form alkaline cellulose. As another example, copper ammonium rayon is regenerated cellulose fiber produced by a process comprising dissolving cellulose in a solution of ammonia copper oxide. As another example, Lyocell is a term used for regenerated cellulose fibers composed of cellulose precipitated from an organic solution in which no substitution of hydroxyl groups occurs and no chemical mediator is formed. Lyocell may be produced by a process comprising dissolving cellulose in water, suitably about 12% water, and N-methylmorpholine-N-oxide. In one embodiment, the regenerated cellulose fibers of the nonwoven composite web may be selected from the group consisting of viscose rayon, copper ammonium rayon and Lyocell. In another embodiment, the regenerated cellulose fibers of the nonwoven composite web may be based on Lyocell fibers. In some embodiments, regenerated cellulose fibers may have deniers in the range of about 0.1 to about 2.7 deniers or more per fiber, or suitably in the range of about 0.9 to about 2.7 deniers per fiber. Lyocell fibers, methods of making Lyocell fibers, and methods of making webs of Lyocell fibers are disclosed in US Pat. No. 6,306,334 to Luo et al., US Pat. No. 7,067,444 to Luo et al. And Luo, the contents of which are incorporated herein by reference. It is further described in US Pat. No. 8,012,565.

In one embodiment, the regenerated cellulose fibers may be a nonwoven web of fibers formed from Lyocell regenerated cellulose. By way of example, the regenerated cellulose fibers may be TencelWeb nonwoven webs of fibers formed from Lyocell regenerated cellulose (available from Lenzing AG of Lenzing, Austria).

Nonwoven webs of continuous fibers comprising regenerated cellulose can be formed by, for example, known solvent spinning or melt spinning processes, such as known nonwoven extrusion processes such as spunbonding or meltblowing.

Regenerated cellulose fibers can be prepared from original regenerated cellulose, recycled regenerated cellulose, or mixtures thereof.

The regenerated cellulose fibers may further comprise other solvent spinnable or melt spinnable thermoplastic polymers, copolymers or blends thereof. Other suitable polymers include, but are not limited to, for example, polyolefins such as polypropylene, polyethylene, and the like, polyamides, polyesters, polyurethanes, thermoplastic elastomers, blends and copolymers thereof, and the like. Optionally, the regenerated cellulose fibers can be multicomponent fibers composed of two or more different polymers. The regenerated cellulose fibers can be round or of any suitable shape known to those skilled in the art, including but not limited to bilobal, trilobal, and the like. Preferably, the regenerated cellulose fibers may have a basis weight of about 8 to about 70 gsm. More preferably, the regenerated cellulose fibers have a basis weight of about 10 to about 35 gsm.

By way of example, other ingredients or additives may be added to the regenerated cellulose used to prepare regenerated cellulose fibers including pigments, antioxidants, flow promoters, stabilizers, fragrances, abrasive particles, fillers and the like.

The discontinuous fibers hydroentangled with the nonwoven web of regenerated cellulose fibers may be staple fibers, pulp fibers or blends thereof. The discontinuous fibers may be formed into a web and entangled with a nonwoven web of regenerated cellulose fibers, or the discontinuous fibers may be disposed on a nonwoven web of regenerated cellulose fibers and then entangled with a nonwoven web of regenerated cellulose fibers.

Generally, the discontinuous fibers are staple fibers or pulp fibers. Staple fibers and pulp fibers often range from about 1 to about 150 mm, in some embodiments from about 5 to about 50 mm, in some embodiments from about 10 to about 40 mm, and in some embodiments from about 10 to about 25 mm. Has a fiber length. Generally, staple fibers are carded using conventional carding processes, such as wool or cotton carding processes. However, other processes such as air laid or wet raid processes may also be used to form staple fibers or pulp fiber webs. A wide variety of polymeric materials are known to be suitable for use in making staple fibers. Examples include, but are not limited to, polyolefins, polyesters, polyamides, regenerated cellulose and other melt spinnable and / or fiber forming polymers. Any conventional polymer commonly used to make fibers can be used as the polymer component to produce staple fibers useful in the present invention. Other suitable staple fibers include, but are not limited to, acetate staple fibers, rayon staple fibers, Nomex ^® staple fibers, Kevlar ^® staple fibers, polyvinyl alcohol staple fibers, Lyocell staple fibers, and the like.

Staple fibers usable for making nonwoven composites may also be multicomponent (eg, bicomponent) staple fibers. By way of example, suitable configurations for multicomponent fibers include side-by-side configurations and shell-core configurations, and suitable shell-core configurations include eccentric shell-core and concentric shell-core configurations. In some embodiments, as is well known in the art, the polymers used to form the multicomponent fibers have sufficiently different melting points to form various crystallization and / or solidification properties. The multicomponent fiber may have from about 20% to about 80% by weight, and in some embodiments, from about 40% to about 60% by weight low melting polymer. In addition, the multicomponent fibers may have from about 80% to about 20% by weight, and in some embodiments, from about 60% to about 40% by weight high melting point polymer. When bicomponent or multicomponent fibers are used as staple fibers or are part of staple fibers, the composite can be bonded using heat in addition to heat.

In other aspects of the invention, the nonwoven web composite may also include various materials such as, for example, activated charcoal, clay, starch, and superabsorbent materials. By way of example, these materials may be added to the non-thermoplastic absorbent staple fibers prior to their integration into the composite layer. Alternatively, and / or additionally, these materials may be added to the composite after the non-thermoplastic absorbent staple fibers and the thermoplastic fibers are combined. Useful superabsorbents are known to those skilled in the art of absorbent materials.

Hydroentangling of staples of pulp fibers into nonwoven webs of regenerated cellulose fibers can be accomplished using conventional hydroentangling equipment well known in the art. Such hydroentangling equipment can be obtained from Fleissner GmbH, Egelsbach, Germany or other well-known manufacturers. The hydroentangling of the present invention may be performed with any suitable working fluid such as, for example, water. The working fluid flows through a manifold that distributes the fluid evenly to a series of individual holes or orifices. These holes or orifices may have a diameter of about 0.003 to about 0.015 in. By way of example, the invention may be practiced using a manifold comprising a 0.007 in diameter orifice, 30 holes per inch, and one hole row. Many other manifold configurations and combinations can be used. By way of example, a single manifold may be used or multiple injectors may be arranged in series.

In the hydroentangling process, the working fluid passes through the orifice at a pressure in the range of about 200 to about 3500 psig (pounds per square inch gage). In the upper range of the described pressure, it is contemplated that the hydroentangled material or materials can be processed at a rate of about 500 fpm to about 2000 fpm. The fluid affects the material supported by the porous surface or wire, which may be, for example, a single planar mesh having a mesh size of about 40 × 40 to about 100 × 100. The porous surface may also be a multi-ply mesh having a mesh size of about 50 × 50 to about 200 × 200. As is common in many water jet treatment processes, the vacuum slot can be located directly below the hydroentangling injector and / or below the porous entangling surface downstream of the hydroentangling manifold, so that excess water is hydroentangled. Withdrawn from the material or materials.

It may be desirable to use a finishing step and / or a post treatment process to impart selected properties to the nonwoven web composite. By way of example, the nonwoven web composite may be subjected to mechanical treatment, chemical treatment, and the like. Mechanical treatments include, but are not limited to, pressurization, creping, brushing and / or pressing by calender rolls, embossing rolls, and the like, to provide a uniform external appearance and / or specific tactile properties. Chemical workups include, by way of non-limiting example, adhesives, dyes and the like.

In creping of nonwoven web composites, an aqueous dispersion of creping chemistry may be sprayed onto the dryer surface. As an example, liquid or foaming chemicals may be used. In contrast to liquid chemicals, foaming chemicals have sufficient structural integrity to reach the dryer surface. By creating a foaming chemical, the chemical applicator can be placed very close to the dryer surface. The close proximity of the chemical applicator to the dryer surface improves chemical mass efficiency and energy efficiency. The efficiency is increased because the air introduced into the foam acts as a diluent. As a result, less heat is required to remove water from the creping chemistry during the drying process.

Generally, preparing foaming chemicals uses a system that pumps both liquid and air into the mixer. The mixer mixes air into the liquid to produce a foam that inherently comprises a plurality of small air bubbles. The foam leaves the mixer and flows to the applicator.

One parameter for defining the amount of foaming chemical is the blow ratio, which is defined as the ratio of the volume of small bubbles captured by the dispersion chemical to the volume of the dispersion before mixing. For example, at a blow ratio of 10: 1, a dispersion flow rate of 1 liter / minute can capture 10 liters / minute of air into the liquid and produce a total foam flow rate of 11 liters per minute.

In order to achieve a high blow ratio, both mechanical mixing and foaming function of the additive composition are determinants. If the chemical can only hold or capture an air volume up to a blow rate of 5, no matter how powerful the foam unit is, it will not produce a stable foam with a blow rate of 10. Any excess air above the blow rate of 5 is released to the outside of the foaming system after the mechanical force has been removed. In other words, any trapped air above the air containing function of the dispersion becomes unstable. Most of these unstable air bubbles escape from the foam immediately after mechanical agitation is stopped (bubble removal).

A further advantage of foam creping is that after the creping step, the dry layer of the additive composition remaining on the tissue substrate surface adds more volume. The increase in volume is due to the trapped air inside the coated layer. Although the foamed additive composition becomes a film during the drying step, not all of the air trapped in the foam is lost during the drying step due to the higher viscosity associated with the higher solids level of the foamed additive composition. In some embodiments, the film can be a substantially continuous film.

Most commercial blowing agents are suitable for producing foam creping. Suitable blowing agents include polymeric materials in liquid form. The foamable composition of the water-insoluble polymer may be in the form of a dispersion or solution. Examples of effervescent dispersions include polyolefin dispersions such as HYPOD 8510 available commercially from The Dow Chemical Company, Freeport, Texas; And Kraton Polymers U.S., Houston, Texas, USA. Polyisoprene dispersions, such as those sold under the KRATON trademark commercially available from LLC, polybutadiene-styrene block copolymer dispersions, latex dispersions such as E-PLUS commercially available from Wacker, Munich, Germany; Both include, but are not limited to, polyvinyl pyrrolidone-styrene copolymer dispersions and polyvinyl alcohol-ethylene copolymer dispersions available from Aldrich, Milwaukee, Wisconsin.

Further details regarding the foam creping process can be found in US patent application Ser. No. 12/979852, filed Dec. 28, 2010, the entirety of which is incorporated herein by reference.

Importantly, the creping efficiency of nonwoven composites comprising regenerated cellulose fibers is improved by the fact that the regenerated cellulose fibers are not as temperature sensitive as other synthetic thermoplastic polymer fibers. Nonwoven composites comprising regenerated cellulosic fibers are fabricated on a hot dryer surface at temperatures in excess of about 300 ° F., suitably in the range of about 350 to about 550 ° F., more suitably in the range of about 500 to about 550 ° F. Can be dried.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the present invention, reference is made to the drawings of the present specification. Referring to FIG. 1, a process 10 for forming the nonwoven composite of the present invention is schematically illustrated. As mentioned above, the nonwoven composites of the present invention may all be composed of regenerated cellulose fibers or may only partially comprise regenerated cellulose material. By way of example, both continuous fibers and / or discontinuous fibers may be composed of regenerated cellulose material, or may only partially comprise regenerated cellulose material.

According to the present invention, a dilute suspension of discontinuous fibers is supplied by the head box 12 and deposited onto the forming fabric 16 of a conventional paper machine through a sluice 14 in a uniform dispersion. The suspension of fibers can be diluted to any desired concentration. By way of example, the suspension may comprise fibers suspended in about 0.01 to about 1.5 weight percent water. Water is removed from the suspension of fibers to form a layer of discontinuous fibers 18.

Small amounts of wet-strength resins and / or resin binders may be added to improve strength and wear resistance. Useful binders and wet-strength resins include, for example, Kymene 557 H, available from Ashland Hercules Chemical Company. Crosslinking aids and / or hydration aids may also be added to the fiber mixture. Separation aids may be added to the fiber mixture to reduce the extent of any potential hydrogen bonding where very open or loose nonwoven fiber webs are desired. Binding aids of one embodiment are available from Quaker Chemical Company, Consohoken, Pa. Under the trade name Quaker 2008. As an example of the composite, adding certain separation aids in amounts of 0.1 to 4% by weight has also been shown to reduce the measured static and dynamic coefficient of friction and improve the wear resistance of the continuous filament-rich side of the nonwoven composite. Separators are believed to act as lubricants or friction reducers.

Nonwoven web 20 comprising regenerated cellulose fibers is unwound from feed roll 22 and passes through nip 24 of S-roll arrangement 26 formed by stack rollers 28, 30. Nonwoven web 20 may be formed by known nonwoven web manufacturing processes, such as, for example, known solvent spinning or melt spinning processes, and may pass directly through nip 24 without first being stored on a feed roll. have. Continuous filament nonwoven web 20 may be a nonwoven web of continuous melt spun regenerated cellulose filaments formed by a spunbond process. Melt spun filaments may be formed from any composition comprising regenerated cellulose described above.

Nonwoven substrate 20 may have a basis weight of about 3.5 to about 70 grams per square meter (gsm). In particular, the nonwoven substrate 20 may have a basis weight of about 10 to about 35 gsm. The polymer may include additional materials such as, for example, pigments, antioxidants, flow promoters, stabilizers and the like.

Preferably, the nonwoven continuous filament web 20 has less than about 30% total bond area and a uniform bond density greater than about 100 bonds per square inch. As an example, the nonwoven continuous filament web may have a total bonding area of about 2 to about 30% (as determined by conventional optical microscopy methods) and a bonding density of about 250 to about 600 fin bonds per square inch.

This combination of total bond area and bond density results in a continuous filament web having a fin bond pattern with more than about 100 pin bonds per square inch that provides less than about 30% of total bond surface area when in total contact with the smooth anvil roll. By combining. The upper limit of bonds per square inch may be at least 600 pin bonds per square inch. As the number of pin bonds per square inch increases, the size of the pin will generally decrease to maintain the bond density within the desired range. Preferably, the bonding pattern may have a fin bond density of about 250 to about 350 pin bonds per square inch, and a total bond surface area of about 10% to about 25% when in contact with the smooth anvil roll.

Although the pin bond created by the thermal bond roll has been described above, the present invention contemplates any form of bond that creates a good tie down of the filament with a minimum overall bond area, such as a hot air knife (HAK). Another example is a combination of latex implants and thermal bonds that can be used to provide a desired filament fixture with a minimum bond area. Alternatively and / or additionally, the resin, latex or adhesive may be applied to the nonwoven web, for example by spraying, printing or drying to provide the desired bond.

The layer of fiber 18 is then disposed on a nonwoven web 20 disposed on the porous entangling surface 32 of a conventional hydraulic entangling machine. The fiber 18 is preferably between the hydroentangle manifold 34 and the nonwoven web 20 of regenerated cellulose. The layer of nonwoven web 20 and fiber 18 passes under one or more hydroentangle manifolds 34 and jets of fluid to entangle all or at least most of the filaments and fibers of the nonwoven web 20 of regenerated cellulose. Is treated as. In addition, a jet of fluid drives the fibers into and through the nonwoven web of regenerated cellulose fibers 20 to form the composite 36.

Alternatively, hydroentanglement may occur while the layer of fibers 18 and the nonwoven web 20 are present on the same porous screen (ie mesh nonwoven composite) where wet excretion is made thereon. The present invention also contemplates superimposing the dried sheet on a nonwoven web comprising regenerated cellulose fibers, re-humidifying the dried sheet to a certain concentration, and then subjecting the re-humidified sheet to hydroentanglement.

Hydroentanglement may occur while the fibers 18 are highly saturated with water. By way of example, the layer of fibers 18 may include up to about 90 weight percent water just prior to hydroentanglement. Alternatively, the fiber may be an airlaid or dry excretion layer of the fiber.

Hydraulic entanglement can be achieved using conventional hydroentangle equipment such as can be found in US Pat. No. 3,485,706 to Evans, the contents of which are incorporated herein by reference. Hydraulic entanglement of the present invention may be performed with any suitable working fluid such as, for example, water. The working fluid flows through a manifold that distributes the fluid evenly to a series of individual holes or orifices. These holes or orifices can be about 0.003 to 0.015 in diameter. By way of example, the invention may be practiced using a manifold produced by Rieter-PerfoJet, Inc. of Grenoble, France. Many other manifold configurations and combinations can be used. By way of example, a single manifold may be used or multiple manifolds may be arranged in succession.

In the hydroentanglement process, the working fluid passes through the orifice at a pressure in the range of about 200 to about 3000 psig (pounds per square inch gauge). In the upper range of the described pressure, it is contemplated that the nonwoven composite can be processed at a rate of about 1500 fpm (feet per minute). The fluid may, for example, impact the nonwoven webs 20 and fibers 18 of regenerated cellulose fibers supported by a porous surface, which may be a single planar mesh having a mesh size of about 8 × 8 to about 100 × 100. have. The porous surface may also be a multilayer mesh having a mesh size of about 50 × 50 to about 200 × 200. As is typical of many water jet treatment processes, the vacuum slot 38 can be located directly below the hydro-needling manifold or just below the porous entangled surface 32 downstream of the entangled manifold, so that excessive water It is withdrawn from this hydroentanglement composite 36.

Although the inventors are not bound to a particular theory of operation, the columnar jet of working fluid that directly affects the fibers disposed on the nonwoven web of regenerated cellulose fibers may be partially and through a matrix or nonwoven network of filaments of the web. It is believed to act to drive these fibers into it. When a fluid jet or fiber interacts with a nonwoven web having the bonding properties described above (and a filament diameter in the range of about 5 microns to about 40 microns), the fibers are also intertwined with the regenerated cellulose filaments of the nonwoven web and . On the other hand, if the overall bonding area of the web is too large, fiber penetration can be poor. In addition, too large bond areas also cause dirty nonwoven composites, because when they hit a large nonporous bond spot, jets of fluid splatter, scatter and wash off the fibers. The specified level of bonding provides a coherent web that can be formed into a nonwoven composite by hydroentanglement on only one side and also provides a strong and useful nonwoven composite and a nonwoven composite with desirable dimensional stability. .

In one aspect of the invention, the energy of the fluid jet affecting the fibers and the web is controlled so that the fibers are inserted into and intertwined with the web of regenerated cellulose fibers in a manner that enhances the two-sidedness of the nonwoven composite. Can be. That is, the entanglement can be adjusted to produce a corresponding low fiber concentration on the opposite side and a high fiber concentration on one side of the nonwoven composite. Alternatively, the nonwoven web of regenerated cellulose fibers may be entangled with a fiber layer on one side and another fiber layer on the other side.

After the fluid jet treatment, the nonwoven composite 36 may be transferred to an incompressible drying operation. Differential speed pickup rolls 40 may be used to transfer material from the hydraulic needling belt in an incompressible drying operation. Alternatively, conventional vacuum pickup and delivery nonwoven composites can be used. If desired, the nonwoven composite may be wet creped by a liquid or foam creping process as described above prior to delivery to the drying operation. Incompressible drying of the web can be accomplished using a conventional rotary drum through-air drying apparatus, shown at 42 in FIG. 1. The through dryer 42 may be an external rotatable cylinder 44 having a perforation 46 in combination with an outer hood 48 to receive hot air blown through the perforation 46. The through dryer belt 50 delivers the nonwoven composite 36 over the upper portion of the through dryer outer cylinder 40. The heated air blown through the perforations 46 in the outer cylinder 44 of the through dryer 42 removes water from the nonwoven composite 36. The temperature of the air blown through the nonwoven composite 36 by the through dryer 42 is between about 200 and about 550 ° F, suitably between about 300 and about 550 ° F, and more suitably between about 500 and about 550 ° F. It can be a range. Other useful through drying methods and apparatus can be found, for example, in US Pat. Nos. 2,666,369 and 3,821,068, the contents of which are incorporated herein by reference.

It may be desirable to use a finishing step and / or a post treatment process to impart selected properties to the composite 36. By way of example, the nonwoven composite may be lightly pressed, creped or brushed by a calender roll to provide a uniform external appearance and / or specific tactile properties. Alternatively and / or additionally, chemical workups such as adhesives or dyes may be added to the nonwoven composite.

Test procedure

Caliper: The caliper of the fabric corresponds to its thickness. The caliper is in this example a TAPPI test method, T402 "Standard Conditioning and Testing Atmosphere For Paper, Board, Pulp Handsheets and Related Products" or T411 om-89 "Thickness (caliper) of Paper, Paperboard with Note 3 for laminated sheets. , and Combined Board ". The micrometer used to perform the T411 om-89 can be an Emveco Model 200A Electronic Microgage (manufactured by Emveco, Inc., Newbury, Oregon) with an enville pressure of 2 kilopascals and an anvil diameter of 57.2 mm. .

Gripping Tensile Strength: The gripping tensile test is a measure of the fracture strength of a fabric when subjected to unidirectional stress. This test is known in the art and meets the specifications of Method 5100 of Federal Test Methods Standard 191A. The result is expressed in pounds until destruction. Higher numbers indicate stronger fabrics. The gripping tension test uses two clamps, each of which has two jaws, each jaw having a face contact with the sample. The clamps hold material that is generally vertically separated in the same plane by 3 in (76 mm) and are spaced at a specified elongation. Values for gripping tensile strength are 4 in (102 mm) x 6 in (152 mm), with a jaw face size of 1 in (25 mm) x 1 in and a constant rate of extension of 300 mm / min. Is obtained using a sample size. The sample is wider than the clamp jaw to provide results representative of the effective strength of the clamped width of the fiber combined with the additional strength contributed by adjacent fibers in the fabric. Psalms eg, Cary, NC, which is available from Sintech Sintech Corporation of two materials tester, Massachusetts Instron, available from Instron Corporation of Canton Model ^TM or material of Pennsylvania in Philadelphia Thwing-Albert Instrument Co. It is clamped in a Thwing-Albert Model INTELLECT II available from. This simulates the fabric stress conditions used in practice. The results are reported as the average of three specimens and can be performed using the specimen in the cross direction (CD) or machine direction (MD).

Absorption Capacity: Absorption capacity refers to the ability of a material to absorb a liquid (eg, water or motor oil) over a period of time and relates to the total amount of liquid held by the material at its saturation point. Absorption capacity is measured according to federal specification number UU-T595C on industrial and standard towels and wiping paper. Specifically, the absorption capacity is determined by measuring the increase in the weight of the sample resulting from the absorption of the liquid, and is expressed as either the% of the absorbed liquid or the weight of the absorbed liquid using the following equation.

Absorption Capacity = (Saturated Sample Weight-Sample Weight)

or

% Absorption Capacity = [(Saturated Sample Weight-Sample Weight) / Sample Weight] x 100

Cup Crush: The ductility of nonwoven fabrics can be measured according to the "cup crushing" test. The cup test consists of 23 cm x 23 of fabric fabricated to approximately 6.5 cm diameter by a 6.5 cm high reversing cup, with the cup shaped fabric surrounded by a cylinder of approximately 6.5 cm diameter to maintain uniform deformation of the cup-shaped fabric. Fabric stiffness is assessed by measuring the peak load required for a 4.5 cm diameter hemispherical forming foot to grind the cm fragments. An average of 10 readings is used. The foot and cup are aligned to avoid contact between the foot and the cup wall, which may affect readings. Foot is measured at a rate of about 0.25 inches per second (38 cm per minute) and measured in grams. Lower cup break values indicate softer laminates. In addition, the cup grinding test is formed by a value for the total energy required to grind the sample (“cup grinding energy”), which is the energy from the start of the test to the peak loading point, ie load in grams on one axis. The area under the curve to be calculated and the distance in millimeters in which the foot travels to the remaining phase are calculated. Cup grinding energy is reported in gf * mm units. A suitable device for measuring cup break is a model FTD-G500 load cell (500 gm range) available from Schaevitz Company, Pensauken, NJ.

In-Hand Ranking Test (IHR): IHR is a basic assessment of the hand feel of fibrous webs and evaluates properties such as ductility. Such a test is useful for obtaining a rapid reading of whether process changes are detectable by manpower and / or affect soft softness against the control. Differences in IHR ductility data between treated and control webs reflect the extent of ductility improvement.

Panels of testers were trained to provide more accurate assessments than the average untrained consumer can provide. Grade data generated for each sample code by the panel was analyzed using a proportional hazards regression model. This model computationally assumes that the panelist goes through the grading process from the largest attribute to the smallest attribute being evaluated. Ductility test results are expressed as log odd values. The log order is the natural log of the risk ratio estimated for each code from the proportional risk regression model. Larger log odds indicate that the associated attribute is perceived with greater intensity.

Because the IHR results are expressed in log odds, the improved softness deviation is much more pronounced than the data actually shows. As an example, when the deviation of the IHR data is 1, this actually represents a 10-fold (101 = 10) improvement of the total ductility or a 1,000% improvement over its control. In another example, when the deviation is 0.2, this represents a 1.58-fold (100.2 = 1.58) or 85% improvement.

Data from the IHR can also be expressed in grade form. This data can generally be used to perform relative comparisons within a test when the grading of the product depends on the graded product. Cross-test comparisons can be made when at least one product is tested in both tests.

 The following examples and comparative examples have been prepared to illustrate the unexpected properties of the nonwoven composites of the present invention.

Yes

Coating chemistries as described below are applied on drums of cylinders which are foamed and heated in an offline conversion process. The dryer has a diameter of 22 inches. Various dry hydroentangling basesheets are coated on heated cylinder rolls with coating chemistries and creped from the heated rolls upon curing of the foam coating on the substrate.

The various basic sheets evaluated were:

1. Commercial 54 gsm pulp / polypropylene (PP) commercial Hydroknit® basesheets.

2. Lyocell Combined Carded Web (Lyocell Hydroknit®) Pulp and Hydroentangled (Lyocell Basis Weight = 25 gsm)

3. TencelWeb (TencelWeb Hydroknit®) pulp and hydroentangled (TencelWeb basis weight = 15 gsm)

The base sheet described above is treated with the following chemicals:

1. 14% solid Crepetrol mixture: Resozol (90:10) (available from Ashland, Inc., Wilmington, DE) + blowing agent. (Unifroth 0154 (available from Unichem, Inc., Greenville, SC))

2. HYPOD 8510 creping chemistry with 30% DPOD solids + 10% Expancel® (available from Eka Chemicals, Inc., Dallas, GA).

This chemical is diluted to the above mentioned level with water and foamed using the above-mentioned foam producing process. Processing details are listed in Table 1.

Tables 2, 3, 4 and 5 summarize the measured properties for the codes of each example.

Table 2 contains material volume and caliper data. This data shows that creping increases the volume of material compared to its corresponding control.

Table 3 contains absorbent capacity data, which shows that creping in combination with the use of Lyocell fibers results in increased absorbent capacity compared to standard pulp / PP hydroentangling materials (code 512s compared to code 511).

Table 4 contains cup grinding data for various material examples. The data show that Lyocell or TencelWeb results in lower energy when hydroentangled and creped with pulp, which means that the lower energy is a softer tactile material. The reduction in energy is as high as 66% (between Code 3 and Code 512s).

Table 5 contains IHR (enhanced ranking) ductility data for selecting codes that show that TencelWeb hydroentangling pulp is perceived as softer than pulp and hydroentangled polypropylene spunbond (codes 512s and 511). .

Although the present invention has been described with reference to various embodiments, those skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For this reason, the foregoing detailed description is considered to be illustrative and not restrictive, and the appended claims, including all equivalents, are intended to define the scope of the invention.

Claims (20)

A direct forming nonwoven comprising regenerated cellulose fibers and staple or wood pulp fibers,
Placing regenerated cellulose fibers on the forming surface;
Depositing staple or wood pulp fibers on regenerated cellulose fibers;
Hydroentangling the regenerated cellulose fibers and staple or wood pulp fibers together to form a hydroentangled composite;
Drying the hydroentangled complex; next
Creping the hydroentangled composite with a foamed creping solution or dispersion
Directly formed nonwoven fabric formed from. The direct formed nonwoven fabric of claim 1, wherein the regenerated cellulose fibers have a basis weight of about 10 to about 20 grams per square meter. The direct forming nonwoven fabric of claim 1, wherein the regenerated cellulose fibers are continuous fibers. The direct forming nonwoven of claim 1, wherein the staple or wood pulp fibers have a basis weight of about 30 to about 150 grams per square meter. The method of claim 1 wherein the creping step
Positioning the additive composition applicator adjacent to the hot impermeable dryer surface;
Applying a foamed dispersion or foamed solution comprising the additive composition to the dryer surface;
Converting the foamed dispersion or foamed solution into an adhesive film;
Bonding the hydroentangled composite directly to the adhesive film; And
Scraping the bonded hydroentangled composite and adhesive film from the dryer surface
Directly formed nonwoven comprising a. The direct forming nonwoven fabric of claim 5, wherein the adhesive composition further comprises a blowing agent. The direct forming nonwoven fabric of claim 6, wherein the additive composition comprises a hydroxypropyl cellulose solution. The direct forming nonwoven of claim 5, wherein the high temperature impermeable dryer surface has a temperature in excess of about 300 ° F., optionally between about 500 ° F. and about 550 ° F. 7. An integrated composite fabric comprising greater than about 5 wt% and less than about 30 wt% continuous regenerated cellulose filaments and greater than about 70 wt% and less than about 95 wt% wood pulp fibers. The composite composite fabric of claim 9 having an absorption capacity of greater than 5.6 g / g. 10. The composite composite fabric of claim 9, having a softness of at least 4 logs than a similar integrated composite fabric having polypropylene filaments instead of regenerated cellulose filaments. 10. The integrated composite fabric of claim 9, wherein the wood pulp fibers are discontinuous fibers. 10. The integrated composite fabric of claim 9, wherein the continuous regenerated cellulose filaments are lyocell filaments. 10. The integrated composite fabric of claim 9, wherein the continuous regenerated cellulose filaments are spunbond filaments. A method of making a direct molded nonwoven fabric comprising recycled cellulose fibers and wood pulp fibers,
Placing regenerated cellulose fibers on the forming surface;
Depositing wood pulp fibers on regenerated cellulose fibers;
Hydroentangling the regenerated cellulose fibers and wood pulp fibers together to form a hydroentangled composite;
Drying the hydroentangled complex; next
Creping the hydroentangled composite with a foamed creping solution or dispersion
Directly forming nonwoven fabric manufacturing method comprising a. The method of claim 15 wherein the regenerated cellulose fibers are continuous fibers. The method of claim 15, wherein the creping step
Positioning the additive composition applicator adjacent to the hot impermeable dryer surface;
Applying a foamed dispersion or foamed solution comprising the additive composition to the dryer surface;
Converting the foamed dispersion or foamed solution into an adhesive film;
Bonding the hydroentangled composite directly to the adhesive film; And
Scraping the bonded hydroentangled composite and adhesive film from the dryer surface
Directly forming nonwoven fabric manufacturing method comprising a. 18. The method of claim 17, wherein the additive composition further comprises a blowing agent. The method of claim 18 wherein the additive composition comprises a hydroxypropyl cellulose solution. The method of claim 17, wherein the high temperature impermeable dryer surface has a temperature above about 300 ° F., optionally between about 500 ° F. and about 550 ° F. 18.

Images