EP4097286B1 - Cellulose acetate-containing fibrous material for a nonwoven product, nonwoven product comprising such a fibrous material, and method for producing such a fibrous material - Google Patents

Description

The present invention relates to cellulose acetate-containing fiber materials and products obtainable therefrom. These include in particular flat products such as nonwovens.

A particularly preferred aspect of the invention relates to wipes, cleaning wipes, sanitary products, medical products and household towels made of such cellulose acetate-containing fiber materials, which are characterized by advantageous properties, in particular with regard to their behavior towards externally acting moisture.

The invention further provides processes for producing the cellulose acetate-containing fiber materials and the products derived therefrom.

Flat products that contain cellulose acetate-containing fiber materials according to the invention or are made from them can be available in different forms. One example is so-called nonwoven products.

Nonwovens are now seen as an independent product group. Nonwovens include nonwovens and nonwoven fabrics and finished products made from them often for cleaning and hygiene needs. These composite materials, which are often textile-like, are flexible, porous fabrics that are not made by the classic methods of weaving warp and weft or by stitching, but by intertwining and/or by cohesive and/or adhesive bonding of typical synthetic textile fibers, which can be in the form of endless or finite-length prefabricated threads, as synthetic threads produced in situ, or in the form of staple fibers.

Alternatively, they can be made from mixtures of synthetic fibres in the form of staple fibres and natural fibres, for example natural plant fibres.

Hydrophobic properties are undesirable for nonwoven products of the type considered here, particularly for sheet-like textile structures such as nonwovens. Such nonwoven products in the form of nonwovens are used, for example, as cleaning and wiping cloths, dishcloths and napkins. In these applications, it is important that spilled liquids such as milk, coffee, etc. are quickly and completely absorbed when wiped up and that damp surfaces are dried as completely as possible. A cleaning cloth absorbs liquid more quickly the faster it is transported across the fiber surface, with fibers with a hydrophilic surface being easily and quickly wetted by aqueous liquids.

In order to hydrophilize the surfaces of flat textile structures and thus improve the water absorption properties of the textile structures, especially nonwovens, surface-active hydrophilizing agents such as emulsifiers, surfactants or wetting agents are generally used. This achieves excellent initial hydrophilicity. However, these textile structures, for example nonwovens, have the disadvantage that the hydrophilic agents are gradually washed out by water or other aqueous media.

In particular, after repeated contact with water, the product becomes increasingly hydrophobic.

Another disadvantage of the known surface-active agents is the strong reduction of the interfacial tension of water, so that in many Applications, particularly in hygiene and cleaning fleeces, the permeation tendency and the wetting capacity of the extracted liquid is undesirably increased.

The publication WO 2020/200873 A1 relates to an insulating material, in particular in the form of mats, which can be used with or without lamination, for example between roof rafters, wherein the insulating material is designed as a tubular composite structure comprising tubular cellulose acetate filaments.

The publication WO 2020/046634 A1 also relates to a fiber material for thermal insulation.

The publication EP 0 634 113 A2 relates to a filter rod for cigarettes, wherein the filter rod comprises cellulose ester fibres.

The publication US 4,276,173 A relates to semipermeable hollow fibers made of cellulose acetate with an inner diameter in the range of 100 to 300 µm and a wall thickness in the range of 20 to 60 µm.

The present invention is based on the object of providing hydrophilic linear or planar structures and a method for increasing the surface hydrophilicity of such structures.

This object is achieved in particular by a cellulose acetate-containing fiber material according to independent patent claim 1, wherein advantageous further developments of the fiber material according to the invention are specified in the dependent claims.

Accordingly, the invention relates in particular to a cellulose acetate-containing fiber material for a nonwoven product, in particular in the form of a wiping cloth, cleaning cloth, sanitary product, medical product or household towel, wherein the fiber material is at least partially or regionally designed as a tubular composite structure which has tubular cellulose acetate filaments.

The fiber material according to the invention is based on the basic idea of exploiting the natural hydrophobicity of the tubular cellulose acetate filaments due to the capillary effect. This ensures that the fiber material has increased surface hydrophilicity even after repeated contact with water.

In particular, the fiber material according to the invention can be produced in a particularly environmentally friendly manner, since the application of surface-active hydrophilizing agents, such as emulsifiers, surfactants or wetting agents, can be completely dispensed with.

The fiber material according to the invention consists of cellulose acetate filaments, so that the fiber material is completely biocompatible and biodegradable. The fiber material is in principle as degradable as wood, for example, although the tubular composite structure enables optimal water absorption over the surface and in the capillaries, which is comparable to the corresponding values that can be achieved with microfibers made of polyester, polyamide or polyacrylic.

The cellulose acetate filaments that make up the fiber material preferably have triangular or star-shaped hollow cross-sections in order to form a larger attack surface than the fibers usually used in cleaning cloths.

Preferably, the cellulose acetate filaments are relatively large compared to the fibers usually used in cleaning cloths and are, for example, between 5 and 30 den or dtex. In this way, the fiber material according to the invention is particularly suitable for cleaning surfaces, for example tiles, mirrors or glass.

The fiber material consists of cellulose acetate filaments and/or cellulose acetate staple fibers, which are formed by forcing a solution of cellulose acetate with an acetyl number of at least 53% in acetone through a spinneret with several openings. The cellulose acetate filaments are then cut into cellulose acetate staple fibers, if necessary. The cellulose acetate filaments are combined to form a filter tow, which is crimped if necessary.

In particular, it is provided that the spinneret through which the solution of cellulose acetate is pressed is designed in such a way that hollow-shaped cellulose acetate filaments are spun externally.

In particular, the hollow portion in the tubular composite structure of the cellulose acetate-containing fiber material is 25% to 90% and preferably 50% to 80%. This hollow portion makes a decisive contribution to the achievable permanent hydrophilic effect of the fiber material, which can only be achieved due to the hollow fibers of the tubular composite structure, but not with closed filaments, for example with conventional microfibers made of polyester, polyamide or polyacrylic, or with natural fibers. The hollow portion corresponds to the ratio of "hollow" area to the "total" area of the fiber cross-section.

In this context, it should be mentioned that the fibrous material according to the invention differs from the fibers known from the prior art made of polyester, polyamide or polyacrylic in particular in that the filament diameter of the cellulose acetate filaments is significantly larger than the filament diameter of other (synthetic) hollow fibers whose filament diameter is in the range between 1 and 25 µm.

In contrast, the filament diameter of the hollow cellulose acetate filaments is in a range between 50 and 150 µm, and preferably in a range between 60 and 100 µm (outer diameter). In this way, the hollow portion and thus the specific capillary effect of the fiber material according to the invention can be significantly increased.

Furthermore, the fiber material according to the invention is characterized by the fact that it can be made almost chemical-free without having to accept deterioration of the water absorption properties of the fiber material after repeated contact with water.

In addition, cellulose acetate filaments, such as those used for the tubular composite structure of the fibrous material according to the invention, are already known from the cigarette industry for cigarette filters, for example. This material (cellulose acetate) is completely harmless to health, so that the fibrous material according to the invention is particularly suitable for sanitary products or hygiene articles.

A further advantage is that the fibrous material according to the invention can be produced using existing systems for producing filter tow material. Therefore, no increased costs are to be expected for the production of the fibrous material according to the invention, so that the fibrous material itself is relatively easy to produce.

To produce the fibrous material according to the invention, a tow material is first produced from uncrimped continuous cellulose acetate filaments. This is then crimped or uncrimped and cut into fibers, with typical fiber lengths being 10 to 80 mm long, preferably 20 to 50 mm long.

With regard to the tubular composite structure of the fibrous material according to the invention, it is provided according to embodiments that it comprises tubular and crimped continuous cellulose acetate filaments. However, the invention is not limited to cellulose acetate filaments; rather, it has been found that An excellent capillary effect and thus a good and permanent water absorption property can also be achieved if the tube composite structure has tubular, crimped and cut continuous cellulose acetate filaments.

In order to improve the biodegradability of the fibrous material according to the invention, specifically under the influence of environmental influences, it is provided according to embodiments of the solution according to the invention that the tubular composite structure made up of cellulose acetate filaments has an additive which is preferably applied at least in regions to the surface of the cellulose acetate filaments, wherein this additive consists of a nitrogen-containing, organic compound, the degradation of which by microorganisms produces basic decomposition products, in particular ammonia and/or basic compounds, such as an NH group or NH groups and/or an NH ₂ group or NH ₂ groups.

The nitrogen-containing organic compound is preferably urea or a urea derivative. These substances are preferred because they are harmless to health and especially to food law and are available in large quantities at an acceptable price.

On the other hand, the nitrogen-containing organic compound can also consist of a protein, with beta-lactoglobulin being particularly preferred. Proteins are also harmless from a health point of view, and beta-lactoglobulin is produced in large quantities during cheese production as a by-product that is rarely used industrially.

Furthermore, it is preferred that the nitrogen-containing organic compound is a condensation product of an aldehyde with ammonia or with an amine, wherein this condensation product is very particularly preferably hexamethylenetetramine.

Finally, it is preferred that the nitrogen-containing organic compound is a cyclic compound, in particular carbazole. Of course, other nitrogen-containing organic compounds can also be used, although care should be taken to ensure that they are as non-toxic as possible.

Alternatively or additionally, the biodegradability of the fiber material according to the invention can be improved by adding MgO.

According to implementations of the fibrous material according to the invention, it is provided that the tubular composite structure formed from the cellulose acetate filaments consists of an acetone-soluble cellulose acetate with an acetyl number of less than 60%, preferably an acetyl number between 53% and 75%. This ensures that the hydrolysis of the cellulose acetate preceding the biological degradation takes place in a shorter time.

The tow material, which serves as a starting point for producing the fibrous material according to the invention, can be uncrimped (crimp index = 0). Although the material cannot be bulked up with a curl index of 0%, the uncrimped material can be used in thin, flat layers.

Preferably, however, the tow material which serves as a starting point for producing the fibrous material according to the invention has a crimp index which is between 5 and 40% and preferably between 10 and 20%.

In this way, an optimal cross-linking of the cellulose acetate filaments is achieved, while at the same time the tubular composite structure provides a high number of capillaries, which is necessary for an increased water absorption property of the fiber material.

The curl index I _x is a measure of the intensity of the curl. The curl index of a filter tow is determined by a tensile test (relationship between force and elongation). It is defined as the ratio of the stretched length L ₂ under test load minus the initial length to the initial length under preload L ₁ : $${\mathrm{I}}_{\mathrm{x}}={\mathrm{L}}_{\mathrm{2}}-{\mathrm{L}}_{\mathrm{1}}/{\mathrm{L}}_{\mathrm{1}}\ast 100\%$$

The test load is 25 N and the preload 2.5 N. The clamping length is 250 mm. The curl index is determined in a tensile test with a constant strain rate of 300 mm/min on a G02 device from Borgwaldt GmbH, Hamburg. 10 individual measurements are recorded per measurement. The test is carried out under standard conditions: 20 °C and 60% relative humidity.

Preferably, the tensile strength of the tow material, which is the starting point for the fibrous material according to the invention, based on the total titre, is preferably at most 15 cN/tex and even more preferably at most 8 cN/tex. This feature facilitates the mechanical comminution prior to biological degradation. In addition, it is advantageous if cut continuous cellulose acetate filaments are used.

According to embodiments of the present invention, the tensile strength and thus strength of the tow material, which is the starting point for the fibrous material according to the invention, based on the total titre, is between 6 and 20 cN/tex and preferably between 8 and 12 cN/tex for the crimped tow. The tensile strength/strength for uncrimped or even only slightly crimped tow material can be up to 20 cN/tex.

A tow material in the sense of the present invention is basically understood to mean a band made of a large number of cellulose acetate filaments and/or cellulose acetate staple fibers. A filament is understood to mean a practically endless fiber, and the term "staple fiber" means a fiber of limited length. This particularly involves chopped fibers with typical lengths between 10 and 60 mm. Such staple fibers are particularly suitable for use in nonwoven products with particularly high water absorption properties.

For the purposes of the present invention, acetyl number means the proportion of bound acetic acid in the cellulose acetate, expressed as a percentage by mass.

In summary, the fibrous material according to the invention achieves various advantages. Firstly, the tubular composite structure formed from cellulose acetate is suitable for use in special applications in the medical field, which can nevertheless be produced relatively inexpensively. The fibrous material according to the invention also shows an acceleration of the rotting rate under environmental influences compared to known fibrous materials made from polyolefins; nevertheless, the use of the fibrous material as a cleaning agent is or wiping cloth, sanitary product, medical product or household towel is easily possible under today's usual conditions without the risk of microbiological degradation.

The tubular cellulose acetate filaments are produced by essentially spinning cellulose acetate filaments by pressing a solution of cellulose acetate in acetone through a spinneret with multiple openings and optionally subsequently cutting the cellulose acetate filaments into cellulose acetate staple fibers, and combining a plurality of the cellulose acetate filaments and/or cellulose acetate staple fibers thus obtained to form a tow material.

In order to ensure that the additive is present in the cellulose acetate filaments and in the cellulose acetate staple fibers, this additive can be added to the aforementioned solution of cellulose acetate in acetone, after which it is spun.

In order to ensure that the additive, i.e. the optionally added compound, is present on the surface of the cellulose acetate filaments and the cellulose acetate staple fibers, this additive can be applied to these filaments or to the cellulose acetate staple fibers formed therefrom during the manufacture of the tow material, but after the formation of the cellulose acetate filaments. For example, the additive can be applied to the filaments immediately before the cellulose acetate filaments are cut into cellulose acetate staple fibers, or the additive can be applied to the finished tow material, i.e. after the cellulose acetate filaments and/or cellulose acetate staple fibers have been combined to form a tow material.

In order to bulk up the provided tow material, which may contain the optionally provided additive, a so-called processing device is used according to implementations of the present invention, which can have a pair of rollers for continuously pulling an endless strip of tow material from a tow bale. After removal from the tow bale, the tow strip passes two air nozzles on its way to the pair of rollers, on which it is guided over a deflection roller, which serve to spread and loosen the fabric of the tow strip.

The invention relates not only to the optimized fiber material, but also to the use of the fiber material as a nonwoven product, in particular in the form of a cleaning or wiping cloth, a sanitary product, a medical cloth or a household cloth. For example, the fiber material according to the invention can be used in cleaning textiles in a wide variety of forms, in particular as a cleaning cloth, cleaning glove, cleaning tape and/or cleaning disc for cleaning machines, as well as for other purposes.

Claims (10)

1. Cellulose acetate-containing fibrous material for a nonwoven product, in particular in the form of a wipe, cleaning cloth, sanitary product, medical product or household cloth, wherein the fibrous material being configured at least partially or in certain areas as a tubular composite structure comprising tubular and in particular crimped continuous cellulose acetate filaments and/or tubular and in particular crimped and cut continuous cellulose acetate filaments,
   characterized in that

   the filament diameter of the cellulose acetate filaments is in a range between 50 to 150 µm, and preferably in a range between 60 to 100 µm (outer diameter); and that

   the tubular cellulose acetate filaments have a wall thickness of 5 µm to 15 µm.
2. Fibrous material according to claim 1,
   wherein the crimp index of the cellulose acetate filaments is between 0% and 40%, in particular between 5% and 40% and preferably between 10% and 20%.
3. Fibrous material according to claim 1 or 2,
   wherein the tubular cellulose acetate filaments are spaced apart from one another in an irregular arrangement, and wherein the cellulose acetate filaments are preferably crosslinked, wherein the connecting cellulose acetate filaments are intertwined and/or entangled and/or bonded with one another.
4. Fibrous material according to any one of claims 1 to 3,
   wherein the cellulose acetate filaments have a fineness of 5 to 30 deniers.
5. Fibrous material according to any one of claims 1 to 4,
   wherein the hollow portion in the tubular composite structure is 25% to 90% and preferably 50 % to 80%.
6. Fibrous material according to one of claims 1 to 5,
   wherein the tubular cellulose acetate filaments have a strength of 5 cN/tex to 15 cN/tex.
7. Fibrous material according to one of claims 1 to 6,
   wherein the tubular cellulose acetate filaments have an elongation of 5% to 20 % and preferably of 10% to 18%.
8. Nonwoven product comprising the fibrous material according to any one of claims 1 to 7.
9. Nonwoven product according to claim 8,
   wherein the nonwoven product is a wipe, cleaning cloth, sanitary product, medical product or household cloth.
10. Method for producing a cellulose acetate-containing fibrous material for a nonwoven product, in particular in the form of a wipe, cleaning cloth, sanitary product, medical product or household cloth, and in particular a fibrous material according to one of claims 1 to 7, which comprises tubular and in particular crimped continuous cellulose acetate filaments and/or tubular and in particular crimped and cut continuous cellulose acetate filaments, in which method a solution of cellulose acetate having an acetyl value of at least 53% in acetone is pressed through a spinneret having a plurality of openings, and wherein the cellulose acetate filaments are subsequently optionally cut into cellulose acetate spun fibers, and wherein a plurality of the cellulose acetate filaments and/or cellulose acetate spun fibers thus obtained are combined to form a filter tow which is optionally crimped, wherein the spinneret through which the solution of cellulose acetate is pressed is configured such that hollow cellulose acetate filaments are spun,
    characterized in that

    the filament diameter of the cellulose acetate filaments is in a range between 50 to 150 µm, and preferably in a range between 60 to 100 µm (outer diameter); and

    the tubular cellulose acetate filaments have a wall thickness of 5 µm to 15 µm.