DE10227246A1 - Aerodynamically formed fleece with high modulus fibers - Google Patents

Abstract

The present invention relates to an aerodynamically formed composition of absorbent, binder and synthetic fibers, the synthetic fibers having a modulus greater than about 2 grams per denier and a crimp value less than about 30%. The absorbent makes up about 40 to 80% by weight, based on the composition. The binder makes up about 3 to 15% by weight, based on the composition. The synthetic fibers make up about 10 to 50% by weight, based on the composition. The binder is selected from the class of the conventional latex systems, the hot melt adhesive or the binding fibers or a mixture thereof. The absorbent is a natural absorbent or superabsorbent polymer, or a combination thereof. The natural absorbents are selected from the class of cellulose fluff, cotton, cotton linters and regenerated cellulose fibers. The superabsorbent polymer is selected from the class of agar, pectin, guar gum and the synthetic hydrogel-forming polymer. The synthetic fibers are selected from the class of polyolefins such as polyethylene, polypropylene and the like, polyesters such as polyethylene terephthalate and the like, polyamides such as polyamide 6, polyamide 66 and the like, acrylics and their mixtures and copolymers. The synthetic fibers have an average length of about 3 to 18 mm.

Description

The present invention relates to an aerodynamically formed composition for Diapers, incontinence pads, sanitary napkins and other absorbent pads for Body fluids, filters (air filters, fluid filters) and fabrics for Window treatments, upholstered furniture, pillows and bed linen. In particular, the present invention an aerodynamically formed composition of absorbent, Binder and high modulus fibers, which improved through improved loft Pressure resistance and an increased throughput through the molding head of the aerodynamic fleece. The fiber modulus is more than about 2 Grams per denier and the crimp less than about 30%.

Disposable hygiene items such as B. Disposable diapers are commercially successful at However, there is always a need to improve these products in terms of lower Dense, high loft and pressure resistance. So far it was known, the well-known aerodynamic composites of natural absorbents and possibly up to 25% superabsorbent polymer (SAP), bicomponent fibers as binders and manufacture short-cut synthetic fibers for loft and pressure resistance. This known composition contained approximately 10% bicomponent fibers, approximately 10% regular polyester fibers and about 80% absorbent. This product had one sufficient loft, sufficient fluid intake speed and one good wet strength. Generally, a natural one was used to produce this product Absorbent (cellulose) and possibly SAP with the bicomponent fibers and Synthetic fibers mixed and over the mold heads of aerodynamic fleece formers ejected. The composite was then introduced into a heating zone so that the earlier melting component of the bicomponent fiber melted and to the Crossing points of the fibers ran. Next, the composite was put into one Cooling zone introduced, in which the fleece was cooled and so the melted Solidified component and thereby the mixture to a uniform Fleece structure was connected.

In this known composition, the natural absorbent is said to be like the pulp and / or SAP absorb the body fluids, the bicomponent fibers that tie entire fleece together and the synthetic fibers including the later melting synthetic fiber component of the bicomponent fibers for loft and Ensure pressure resistance, so that the largest possible surface of all individual fibers or particles of natural absorbent is exposed to body fluids.

As part of efforts to improve existing performance Production plants have been found to have an increased throughput due to the Form heads of the aerodynamic fleece formers with the previous composition often too Constipation is coming.

The object of the present invention is to improve the composition so that it with increased throughput, the mold heads do not become blocked aerodynamic nonwoven comes.

The present invention relates to the use of short cut fibers a higher modulus than previously used synthetic fibers. By using a Modification of the conventional formulation of about 3-15% by weight of binding fiber, about 40-80 wt .-% absorbent such. B. pulp fluff and 10-50 wt .-% of Synthetic fiber with a higher modulus and less crimp than conventionally used fibers, it is possible to increase the throughput through the molding head to increase the aerodynamic nonwoven.

The higher modulus means higher fiber stiffness. So far, has been general assumed that good die throughput requires flexible fiber.

In the broadest sense, the present invention relates to an aerodynamically formed one Composition with absorbent, binder and synthetic fibers with a high modulus and weak ripple.

The nonwovens according to the invention are suitable for use in diapers, Incontinence pads, sanitary napkins and other absorbent bodies for body fluids, filters (Air filter, liquid filter) as well as fabrics for window treatments, Upholstered furniture, pillows and bed linen. In particular, the present invention relates a composition of absorbents such as B. pulp or synthetic absorbent polymers, binders and high-modulus synthetic fibers.

The synthetic fibers of previously known processes had a cutting length between 3 and 18 millimeters and preferably about 6 millimeters. Typically, such fibers had a modulus of about 1.5 grams per denier (gpd) and below. According to the invention, the fibers used are heat-set in such a way that the modulus is more than about 2 gpd and preferably more than about 2.5 gpd. The increased module stiffens the entire fiber and, in contrast to the general prejudice, it emerges from the aerodynamic fleece former's molding head much cleaner and without clogging and clogging than conventional compositions. The fibers of the invention also show only a slight crimp and in particular a crimp value of less than about 30%. These fibers have a preferred length range of 4 to 8 mm and a titer of about 1.5 to 4 denier and in particular a titer of about 3 denier. The basis weight of nonwovens from the present composition is approximately 50 to 500 grams per square meter (g / m ² ).

Natural absorbents or superabsorbents come as absorbents known synthetic absorbents or a mixture thereof. The Absorbents preferably make up 40-80% by weight of the nonwoven. natural Absorbents are hydrophilic materials such as cellulose fibers, cellulose fluff, Cotton, cotton linters and regenerated cellulose fibers such as rayon or one Mix of them. The cheap and easily accessible pulp fluff is preferred.

Conventional cellulose fibers show good absorption properties, at compacted cellulose fibers, however, increase the absorption capacity for body fluids their partial exchange for synthetic fibers and preferably polyester fibers, that give the composite loft. Due to the larger loft of the composite the Body fluids exposed a larger surface area of the pulp fibers, causing their Absorbance to body fluids increases considerably.

Absorbents based on natural absorbents do not guarantee in all circumstances adequate fluid absorption. They are also natural absorbents pretty voluminous. As a result, many absorbent bodies contain relatively small amounts of SAP. SAP is a lot more expensive than natural absorbents. By partial Replacing the natural absorbents with SAP allows you to see the total size of the Reduce absorbent body and / or improve fluid absorption.

Here is under "superabsorbent", "superabsorbent polymer" or "SAP" to understand water-swellable, usually water-insoluble material, which in the Capable of being at least about 10 times, desirably about 20 times and preferably about 50 times or more its own weight in water take. The superabsorbent polymer can be made of organic material, too which also includes natural substances such as agar, pectin and guar gum, as well as from synthetic materials such as synthetic hydrogel-forming polymers become. Synthetic hydrogel-forming polymers include e.g. B. Carboxymethyl cellulose, alkali metal salts of polyacrylic acid, polyacrylamides, polyvinyl alcohol, Ethylene maleic anhydride copolymers, polyvinyl ether, hydroxypropyl cellulose, Polyvinyl morpholinone, polymers and copolymers of vinyl sulfonic acid, polyacrylates, Polyacrylamides, polyvinyl pyridine and the like. Suitable polymers include further hydrolysed acrylonitrile graft starch, acrylic acid graft starch and Isobutylene maleic anhydride copolymers and mixtures thereof. The hydrogel-forming polymers are preferably slightly cross-linked so that they are essentially water-insoluble. The Crosslinking can, for example, by irradiation or covalently, ionically, via the Waals forces or by hydrogen bonding. suitable Materials are from a wide variety of commercial suppliers such as Dow Chemical Company, Allied Colloid, Inc. and Stockhausen, Inc. The SAP can be in the form of particles, scales, fibers, rods, foils or any other geometric shapes.

The high-modulus, weakly crimped synthetic fibers can be made of all polymeric materials can be made from which fibers can be made which you can form a nonwoven. To suitable polymeric materials, from The synthetic fibers that can be formed include polyolefins such as Polyethylene, polypropylene and the like, polyester such as polyethylene terephthalate or Polybutylene terephthalate or copolyesters such as polyethylene terephthalate isophthalate or Polyethylene terephthalate adipate and the like, polyamides such as polyamide 6, polyamide 66, polyiminocarboxylpentamethylene and the like, acrylics and mixtures and Copolymers thereof. Polyester fiber such as polyethylene terephthalate is preferred. The Synthetic fibers must have a modulus above about 2.0 gpd and preferably above about 2.5 gpd and most preferably above about 3.0 gpd. The Synthetic fibers must also be low-crimp, with crimp preferred is less than about 30%, and most preferably less than about 25%.

The binder according to the present invention can be conventional Latex systems, hot melt adhesive or binding fibers or a mixture thereof are based. Conventional latex systems such as styrene-butadiene copolymer, acrylate and Polyvinyl acetate systems and mixtures thereof are well known. melt adhesive are generally solid powder substances or of latex familiar to the person skilled in the art various pasty or liquid masses. It can be the case with the binding fibers are conventional melt fibers or bicomponent fibers. As conventional melt fibers come for example polyolefins and especially linear ones Low density polyethylene in question. Bicomponent fibers are included as binding fibers a titer between 2 and 6 denier is preferred. The bicomponent fibers can a side-by-side arrangement in which the portion with the lower melting point next to the portion with the higher melting point, or a core shell structure, in which the cladding has the lower melting point and the core the higher melting point, have. The binders become thermal by conventional means such as an oven (Hot air, radiation or microwaves) or a calender roll or calender rolls or bound by ultrasonic energy. The fleece according to the invention contains between 3 and 15 wt .-% of binding fiber, such as. B. a bicomponent fiber. This Binding fiber content is considered sufficient to combine the fleece to connect uniform structures. There is preferably a binder fiber content of approximately 10% by weight, based on the nonwoven weight, very particularly satisfactory results. If a conventional latex system is used in the present invention, the proportion of binder can make up 5-60% by weight of the nonwoven.

Suitable bicomponent fibers consist of polyethylene / polypropylene, Polyethylene / polyester (especially polyethylene terephthalate), polypropylene / polyester, Copolyester / polyethylene terephthalate, such as Polyethylene terephthalate isophthalate / polyethylene terephthalate, polyamide 6 / polyamide 66 and polyamide 6 / polyethylene terephthalate or mixtures thereof or contain such. Preferably Polyethylene / polyester used, especially grafted Polyethylene / polyethylene terephthalate, such as linear low density polyethylene / polyethylene terephthalate.

The fleece according to the invention preferably contains between 3 and 15 wt .-% binding fiber, such as. B. bicomponent fiber. This proportion of binding fiber is considered sufficient to bond the fleece into a single structure. A binder fiber content of about 10%, based on the nonwoven weight, preferably gives very particularly satisfactory results. The fleece also contains 40 to 80 wt .-% absorbent such. B. pulp fibers, possibly partially replaced by SAP. Finally, the nonwoven preferably contains between 3 and 18 mm short synthetic fibers with a titer between 1.5 and 4 denier in an amount of 10 to about 50% by weight, based on the nonwoven weight. The basis weight of the nonwovens from the present composition is approximately 50 to 500 grams per square meter (g / m ² ).

The formation of the fleece can be done aerodynamically in such a way that the simply mix different fibers together and expose them to an air flow that the fibers are conveyed to a surface, preferably a sieve surface, and tangled thereon separates. If binding fibers are used, the fleece is then converted into a heated zone with a sufficient temperature and a sufficient Dwell time introduced so that the earlier melting portion of the binding fiber melts and on the interface of a group of superimposed, touching and crossing fibers flows. Next, the fleece is put on a conveyor belt Transported cooling zone, in which the melted material solidifies completely and so gives the fleece an internal strength. Is the binder a Latex system, the fleece is covered with the latex by spraying, dipping etc. coated, dried and condensed, whereby the latex solidifies. After that you can cut the fleece into different lengths and widths for use, namely to fenestration cloths, dentist bibs, eye pads, diapers, Incontinence pads, sanitary napkins, wound dressings, air filters, liquid filters and Sheets such as curtains, bed linen or pillows.

The fleece can also be used in combination with other components as part of a laminate with a woven or non-woven fabric. For example, there is SMS composites (spunbond / meltblown / spunbond) used for many purposes become. Another well-known example of a multi-component structure is the Sewing fabric consisting of a thread reinforced with a mesh Non-woven fabric.

test methods

The physical properties of the synthetic fibers were as follows Procedure determined.

titres

The titer of the synthetic fibers was according to ASTM 1577-96, option A. endless fiber material (cable) determined.

module

The module was determined according to ASTM 3822-96. Continuous fibers were used in Cable shape with a nominal length of 5 inches (2.7 cm) at one Deformation rate of 60% / minute used. As a module, the load becomes 10% Elongation expressed in grams / denier (gpd).

Ripple Frequency (sheets per inch or centimeter)

The crimp frequency was determined according to ASTM 3937-94 under option one for the Specimen preparation determined.

fullness

An approximately 1.25 m long piece of cable is clamped at one end and biased to pull out the crimp. The cable is at a distance of 1 m cut off from the clamp. You let the cable relax and measure the length the relaxed crimped cable tie (L, cm). The percentage crimp value is 100 - L.

Forming head performance

The tests were carried out on an aerodynamic nonwoven from Dan-Web. The basis weight of the nonwoven was kept constant at 263 g / m ² by increasing the belt speed with increasing fiber throughput through the forming head. The maximum throughput was considered to be the highest possible rate at which the molding head is not yet clogged, which is shown by a decreasing nonwoven basis weight.

example 1

According to a conventional polyester process, a number of Polyester fibers produced, the fiber module via change in Heat setting conditions were varied. The crimping conditions were also varied to to generate different crimp values. The crimp frequency was constant at 7 sheets per Inches (~ 3 sheets per centimeter) and the titer set to 3 denier, with the cable was cut into lengths of 6 mm. Comparative experiment 4 is the commercial product KoSa T224.

A mixture of 10% by weight of these fibers, 12% by weight of the bicomponent fiber KoSa T255 as binding fiber and 78% by weight of cellulose was fed to the molding head. The results are shown in Table 1 below. Table 1

As can be seen in Table 1, a stiffer, high-modulus fiber can be used with a Process higher molding head throughput than conventional, low-modulus fibers. In addition, a smaller crimp value also results in a higher throughput of the molding head.

According to the invention, a composition is thus made available which is the above mentioned tasks, goals and advantages fully met.

Claims (20)

1. Aerodynamically formed composition of absorbent, binder and Synthetic fibers, the synthetic fibers having a modulus greater than 2 gpd and have a crimp value of less than 30%. 2. Composition according to claim 1, wherein the module is greater than 2.5 gpd. 3. Composition according to claim 1 or 2, wherein the module is greater than 3.0 gpd. 4. Composition according to at least one of claims 1 to 3, wherein the Has a crimp value of less than 25%. 5. The composition of claim 1, wherein the absorbent is natural absorbents or superabsorbent polymer or a combination is about it. 6. The composition of claim 5, wherein the natural absorbents from the Class pulp fluff, cotton, cotton linters and Regenerated cellulose fibers are selected. 7. The composition of claim 5, wherein the superabsorbent polymer of the class agar, pectin, guar gum and the synthetic hydrogel-forming Polymers is selected. 8. The composition of claim 7, wherein the synthetic hydrogel-forming Polymers from the carboxymethyl cellulose class, alkali metal salts of Polyacrylic acid, polyacrylamides, polyvinyl alcohol, Ethylene maleic anhydride copolymers, polyvinyl ether, hydroxypropyl cellulose, polyvinyl morpholinone, Polymers and copolymers of vinylsulfonic acid, polyacrylates, polyacrylamides, Polyvinylpyridine and mixtures of several of them are selected. 9. Composition according to at least one of claims 1 to 8, in which the Absorbent makes up 40 to 80 wt .-%, based on the composition. 10. Composition according to at least one of claims 1 to 9, wherein the Synthetic fibers from the class of polyolefins, polyesters, polyamides, the acrylics and their mixtures and copolymers are selected. 11. Composition according to at least one of claims 1 to 10, wherein the Make up synthetic fibers 10 to 50 wt .-%, based on the composition. 12. Composition according to at least one of claims 1 to 11, wherein the Synthetic fiber has a titer between 3 to 15 denier. 13. Composition according to at least one of claims 1 to 12, wherein the Synthetic fibers have an average length of 3 to 18 mm. 14. Composition according to at least one of claims 1 to 13, in which the Binder from the class of conventional latex systems, the Hot melt adhesive, the binding fibers or a mixture thereof is selected. 15. The composition of claim 14, wherein the binder Binding fibers and the binder 3-15 wt .-%, based on the Composition that matters. 16. The composition of claim 14, wherein the binder is a conventional latex system with compounds from the class of Styrene-butadiene copolymer, the acrylate polymer, the polyvinyl acetate polymer and Mixtures of it. 17. The composition of claim 15, wherein the binding fibers Bicomponent fibers from the class polyethylene / polypropylene, Polyethylene / polyester, polypropylene / polyester, copolyester / polyethylene terephthalate and mixtures thereof. 18. Aerodynamically formed, rigid nonwoven, containing 10-50% by weight Polyester fiber, 3-15% by weight binder fiber and 40-80% by weight absorbent, the polyester fiber having a modulus greater than 2 gpd and a crimp value of less than 30%. 19. The nonwoven of claim 18, wherein the polyester fiber has a modulus of greater 2.5 gpd and has a crimp value of less than 25%. 20. Aerodynamic process for the formation of a rigid fleece, in which one 10-50 wt .-% polyester fiber, 3-15 wt .-% bicomponent fibers and 40-80 wt .-% pulp mixed together and exposed to an air stream that Fleece heated to a temperature at which the bicomponent fibers melt, and cool to a rigid fleece, the polyester fiber one Module of greater than 2 gpd and a crimp value of less than 30%.