DE202012103513U1 - Absorbent fiber mat - Google Patents

Abstract

Absorbent fiber mat, which has an absorbent layer of largely biodegradable materials and optionally further layers, characterized in that the absorbent layer contains superabsorbent polymers based on polysaccharides.

Description

The present invention relates to an absorbent fibrous mat comprising an absorbent layer of pulp materials and optionally further layers.

Packaging is often provided with flat mats to protect the packaged goods, which can absorb moisture, liquids and gases escaping from the product, to cushion the product or to protect it from external influences. The flat mats can be present either as a continuous web or in the form of cut, already prefabricated mats. Depending on the application, they can be made from a wide variety of materials and can be obtained in a wide variety of blanks. A big advantage of these mats is that they are easy to handle and can be in large formats as well as small blanks or cut to smaller sizes. A common area in which flat mats are used are as starting or intermediate products for the production of hygiene products, filter materials, cleaning equipment (cleaning wipes). In these areas, the filter materials and absorber materials are often used in the form of flat blanks with simple geometric shapes. These are generally disposable products that are disposed of after use. In most cases, waste disposal means waste incineration because the materials used are not biodegradable.

One reason that the biodegradability of the absorber mats is insufficient is that the hygiene products and filter materials often contain additives that are important to the effect of the materials, in particular the binding effect on the substances to be absorbed and increase the effectiveness. In hygiene products, superabsorbent polymers are often used. This means that even if the base materials in the hygiene products are biodegradable materials, for example those based on pulp, it is not possible to recycle these products to the economic cycle via the composting plant; they must be disposed of via appropriate incinerators.

Flat absorber mats based on pulp are already known from the prior art. An example of such mats is in European Patent 1,032,342 described. These absorber mats are often added so-called absorbent materials with high absorbency for aqueous liquids. These absorbents are also referred to as superabsorbents, SAP. They can absorb large quantities of liquid and hold it permanently. These superabsorbents are mainly made from petroleum products and are not or only very poorly biodegradable. This applies in particular to the usual superabsorbents based on polyacrylates and polyacrylate copolymers. In addition, it may cause skin irritation when used in personal care products, medical or cosmetic applications where skin contact is direct. In particular, the superabsorbents with acrylate structure are classified as not safe, since the polyacrylates are classified in the MAK lists as carcinogenic compounds category 4, ie as substances with effect threshold.

The present invention has for its object to provide absorber materials in the form of sheet-like structures, which are made largely from biodegradable materials and have a good water or moisture absorbency that with the absorber materials of this kind from not biologically degradable polymers are prepared or contain corresponding additives, is comparable.

The present invention accordingly provides an absorbent fibrous mat which has an absorbent layer of largely biodegradable materials and optionally further layers and which is characterized in that the absorbent layer contains superabsorbent polymers based on polysaccharides.

The object according to the invention is achieved by the use of superabsorbent materials based on polysaccharides. The use of polysaccharides also has the advantage that these polymers can be produced from renewable raw materials.

The combination of absorbent layer of largely biodegradable materials and superabsorbent materials based on polysaccharides results in a fibrous mat which is also largely biodegradable. Preferably, the fibrous mat is at least 95% biodegradable.

Biodegradable in the context of the present invention means that the individual components decomposed by microorganisms in the presence of oxygen in carbon dioxide, water and salts of other existing elements (mineralization) to form new biomass or in the absence of oxygen in carbon dioxide, methane, mineral salts and new biomass the material is European Standard EN 13432 "Requirements on the recycling of packaging through composting and biodegradation " should meet. According to this standard, a maximum of 10% of the initial dry weight of the test material, ie the starting material, may be found after composting for a maximum of 12 weeks in a> 2 mm sieve fraction.

The polysaccharide-based superabsorbent polymers are derivatized polysaccharide molecules which have good absorbency to water and aqueous solutions and are also biodegradable, that is, can be recycled to the natural product cycle after use in conventional composting facilities or similar facilities.

As starting material for the preparation of the derivatized polysaccharides, any starch product, fine or coarse meal can be used. Suitable materials include starch such as potato starch, corn starch, wheat starch and sorghum starch, but also coarser corn flour, peeled yucca root, unpeeled yucca root, oatmeal, banana flour and tapioca flour.

A class of derivatized polysaccharides suitable for use in the present invention are so-called graft copolymers of starch. The preparation of these polymers is carried out by prepolymerization of polysaccharides with acid group-containing grafting reagents, wherein the graft copolymer is formed with an acid group as an intermediate and then saponified the graft copolymer in a conventional manner. The saponified product precipitates as a solid. It can be dried, granulated or converted into a solid in a manner known per se.

For the preparation of a graft copolymer, as may be used in the present invention, grafting reagents used are preferably acrylic derivatives, acrylonitrile, 2-acrylonitrile-2-methylpropanesulphonic acid, acrylic acid and / or acrylamide and an initiator. The reaction of acrylonitrile with gelatinized corn starch leads to particularly good results. The acrylic derivatives can be used alone or in combination with other monomers commonly used in the industry. The preferred weight ratio of starch to acrylic derivatives is in the range between about 1: 2 and about 1: 5. The acrylic derivative is polymerized to the starch in the presence of an initiator, preferably a cerium (IV) salt is used. Particular preference is given to using cerium ammonium nitrate as the initiator, although it is also possible to use other suitable initiator systems; those skilled in the art can select them on the basis of their specialist knowledge. The polymerization is completed within a few minutes, with long, grafted chains of polyacrylonitrile (or polyacrylonitrile with other monomers) bound to the starch. Subsequently, the grafted starch copolymer is saponified with an alkali metal hydroxide, typically potassium hydroxide or sodium hydroxide, to convert the nitrile groups to a mixture of carboxamides and alkali carboxylates. The saponification gives a highly viscous mass, which must be converted to a dry form for further use.

The viscous mass of the resulting saponified product is then precipitated and the resulting product isolated. For this it is necessary to separate the isolated product from the viscous polymer. This separation step is usually carried out by adding water-miscible solvents, such as alcohols, such as methanol, ethanol, propanol and isopropanol. The viscous mass is added in the alcohol, preferably methanol, with the alkali starch graft copolymer precipitating in particulate form, separated and dried.

In another embodiment for preparing the resulting graft copolymers, the particles are not precipitated using an alcohol, but an acid-based precipitation is carried out by separating and neutralizing the reaction mixture to form rod-shaped particles. These particles are dried and then optionally ground.

The individual process steps for the preparation of the graft copolymers can be carried out in a manner known per se. The precipitation of the saponified product is usually effected by adding acid to a pH of between about 2.0 and about 3.5, more preferably about 3.0. The precipitate is then washed, preferably with water, to remove salts and optionally other substances. The product may then be separated, for example by settling, centrifuging or any other mechanical separation process. The carboxylic acid of the graft copolymer can then be converted into the alkaline form with alkali metal hydroxide, preferably potassium hydroxide, to a pH of between about 6.0 and about 8.0, in particular about 7.0. The resulting viscous mass is then dusted to reduce tack and dried. The dried particles can be used without further processing, but it is also possible to first fractionate the particles into their respective sizes to obtain a uniform particle size for further processing.

The polysaccharides or polysaccharide derivatives can be used as such or applied to carrier materials, as so-called nanocomposite Materials are used. Suitable support materials are silicates with a high surface area, for example bentonite, zeolites, phyllosilicates, which can take up the superabsorber.

In addition to the graft copolymers described above, other polysaccharide derivatives can be used which have a good absorption capacity against water and aqueous solutions and are biodegradable. These also include intricate polysaccharides with a glass-like pattern and / or cross-linked polysaccharides.

The polysaccharides can be reacted in a conventional manner with conventional crosslinking reagents. Examples of suitable crosslinking reagents are borax (for manose polymers), boric acid (for manose polymers), glyoxal, epichlorohydrin, sodium metaphosphate, sodium tripolyphosphate, phosphorus oxychloride and mixtures thereof. Further suitable crosslinking reagents are organic components, such as succinyl dichloride, alcryloyl chloride, butanediol diglycidyl ether, ethanediol diglycidyl ether, pyromellitic dianhydride, divinyl sulfones, diisocyanates, alkylenebisacrylamides, dicarboxylic, tricarboxylic or polycarboxylic acids, for example malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, malic acid, tartaric acid, itaconic acid, sebacic acid , Citric acid, mucic acid, sugar acid, furandicarboxylic acid and / or butanetetracarboxylic acid and mixtures thereof. Particularly preferred crosslinking agents are boric acid and boron, these crosslinking agents are particularly useful for crosslinking galactomanans.

The superabsorbent polymers are incorporated according to the invention in the absorbent layer of pulp materials. Preferably, they are particulate. Depending on the construction of the absorbent layer, the superabsorbent polymers can be distributed in layers or evenly over the entire absorbent layer.

The absorbent layer according to the invention is largely biodegradable. Preferably, this layer is formed from pulp or pulp-related materials capable of absorbing moisture, water or aqueous polar solutions. It is preferably in the form of non-woven or fabric-like material, with a nonwoven being particularly preferred. These materials have the advantage of being biodegradable. In addition, these are inexpensive and commercially available materials that are easy to work with. Airlaid nonwovens or tissue papers have proven to be particularly suitable adsorption layers. In a preferred embodiment, the absorbent layer of pulp fibers is an airlaid. In a particularly preferred embodiment, the pulp layer has embossed regions distributed over its surface, in which the fibers are pressed together more strongly than in the remaining regions and are thereby adhesively and / or binder-free connected. In one possible embodiment, the absorbent core is made of a fibrous web of cellulose fibers, which are calendered and bonded in a point-free or linear manner to form the embossed regions in the printing region. The embossed areas are preferably frustoconical or truncated pyramidal. The production of such materials is for example in European Patent 1,032,342 described. The fiber layer of the layer of cellulose fibers is structured in this embodiment so that the pulp fibers outside of these discrete embossed areas loosely superimposed or only slightly adhering to each other, whereas they are pressed together in the embossing areas and enter into an intimate connection with the respective adjacent pulp fibers. By this configuration, a complete waiver of adhesives and binders to form the composite of pulp fibers is possible, allowing a simple and complete recycling. In the embossing areas, the fibers do not merely adhere to one another. Rather, it is achieved by the pressurization that adjacent pulp fibers are firmly connected to each other in these embossed areas. This compound is also able to withstand the action of moisture, so that the absorption layer used according to the invention is characterized by mechanical strength even in the wet state. The areas outside the discrete embossing areas, in which the fibers are loosely stacked or only weakly adhered to each other, are characterized by a good absorption capacity. In these areas, the means for binding moisture are preferably present. These can be distributed within the individual pulp fibers and in the areas outside the discrete embossing areas they are in good contact with the environment, in particular with the moisture, due to the loose association of the pulp fibers. If larger amounts of moisture or liquid are present, they are taken up by the loose composite of cellulose fibers, distributed over the entire surface of the absorbent layer and held there.

Below, the fibrous mat according to the invention will be explained in more detail by means of embodiments with reference to the accompanying figures. Show:

1 a greatly enlarged partial section through the pulp mat

2 a greatly enlarged partial section through a multi-layer fibrous mat

3 a greatly enlarged partial section through another multi-layer fibrous mat.

1 shows a partial section through the fibrous mat according to the invention 12 , This mat 12 has a location 1 on that a high percentage of pulp fibers 2 and in the superabsorbent polysaccharides 3 are incorporated. The superabsorbent polysaccharides are particulate in the illustrated embodiment. The location 1 may be used as such or the core of a multilayer mat or multilayer absorbent element 12 form.

The pulp fibers 2 are in the stamping areas 4 compacted and connected in this way. The stamping areas 4 lie in the embodiment shown here on the top and bottom opposite each other, so that in the respective embossing area 4 only a narrow web of interconnected pulp remains. The rest, between the respective stamping areas 4 arranged areas of the layer 1 have a loose pulp layer. An intimate connection between the pulp fibers 2 does not exist in these areas.

The adsorption to moisture, liquids and / or gaseous substances is determined by the location 1 from the pulp fibers 2 and the polysaccharide 3 and any other substances that may be present in the situation 1 can be incorporated. The location 1 has in the embodiment shown here in the stamping areas 4 the shape of truncated pyramids or truncated cones, wherein the angle of the slopes formed should preferably be between 10 ° and 45 °.

As cellulosic material for the fibrous web 1 can be used inexpensively available mass material. Preferably, a so-called fluff pulp is used, which is characterized by a very good binding behavior, which improves the mechanical strength of the element against vertical tensile forces.

In the production of the element according to the invention, a sheet material is first produced in the embodiment shown here, which can then be cut to the desired size. In the production of the web in a continuous process, the later becomes the situation 1 forming fibrous web from a piled up in the air flow bed of fibers 2 from defiberized pulp (wood pulp) and the superabsorbent polymers 3 and optionally incorporated further substances. For the production of a standardized, defiberized commodity, it is possible to make use of the renewable raw materials available on the market.

The method of pulp as the starting material for the situation 1 allows dry processing of the pulp fibers 2 and thus in the subsequent embossing of the multilayer web between two structural rolls a very good compaction of the pulp fibers in the discrete embossing areas 4 , Outside of these stamping areas 4 If the fibers are loosely attached to one another, which influences the behavior of the incorporated polysaccharides in such a way that the moisture does not interfere with the given binding capacity, the loose layering of the fibers between the respective embossing areas also increases the flexibility of the element 1 improved and if the element 1 Used in packaging, it also serves as protection against bumps, etc. of the product to be packaged.

The production of the element according to the invention is made of sheet material, which is manufactured in a continuous process. In air-assisted stratification, the pulp fibers first become 2 and polysaccharides 3 and optionally further additives to form the layer 1 placed. This is followed by the production of the embossed areas in a calender with two structured calender rolls 4 , A possible manufacturing process is z. In the European Patent 1,032,342 disclosed.

Depending on how thick the finished web should be, it is also possible to have several layers of pulp fibers 2 and polysaccharides 3 and optionally further aggregates to be stacked and then introduced into the calender to the embossing areas 4 to obtain. In this way, the Polysaccharrid is incorporated in layers in the web. A homogeneous distribution is achieved if the moisture-binding agents are processed together with the pulp fibers, so evenly distributed in the pulp fibers to sheet material.

A multi-layered train 5 as they are in 2 can be prepared, for example, by a cover layer 6 or a base layer 7 initially used as a carrier layer. On this carrier layer 6 respectively. 7 becomes the bed of pulp fibers 2 and polysaccharide 3 applied in the air stream. Subsequently, this arrangement of carrier layer and bed is passed together through the structural rollers of the calender. Alternatively, previously, ie before the final passage through the calender, the other of the two layers 6 . 7 , which is not already the carrier layer, also on the pulp layer 1 be hung up.

The two layers 6 and 7 can also be added later if necessary with additional layers be applied in a conventional manner. If the further layers are subsequently applied, then they can have any surface structure, for example smooth.

In the 2 illustrated embodiment shows a total 3 Layers, namely one from the layers 6 . 1 and 7 compound track.

The lowest layer serves as a base material and a layer is applied as the upper layer. The cover layer 6 has the advantage that the product to be packaged does not directly contact the pulp fibers and the liquid adsorbent.

As base material 7 and also as a cover layer 6 In particular, those materials are contemplated, through which water vapor can pass, but which is impermeable to the incorporated, the moisture-binding agent. Examples of such breathable materials are perforated two- and / or three-dimensional film, a breathable SMS, nonwoven fabric made of natural or synthetic fibers, a laminate of different materials, such as nonwoven and breathable film (BTBS = Breathable film textile backsheet ). These materials of the layers 6 and 7 are preferably also biodegradable.

In 3 an inventive element is shown that has the same structure as the element of 2 , but from other locations 8th and 9 is surrounded. These other layers 8th and 9 can be larger than the location 1 and the layers optionally arranged thereon 6 and 7 , The layers 8th and 9 may be the same or different and serve to adapt the properties of the element to the specific requirements of the products to be stored. These other layers can be connected together without affecting the location 1 and the layers optionally arranged thereon 6 and 7 is included. These two layers form an envelope for the element. They may be made of textile, nonwoven or film-like material or tissue, wherein at least one layer of such a cover should be permeable to moisture. Preferably, the layers are 8th respectively. 9 selected from cotton, fleece and / or perforated foil.

The fibrous mat according to the invention can be used for the production of hygiene products, as a filter material, for use in dedusting and gas cleaning plants and in tobacco products, household and cleaning goods.

LIST OF REFERENCE NUMBERS

1

location

2

Cellulose fibers

3

superabsorbent polymers

4

embossed areas

5

Multi-layered train

6

topcoat

7

base layer

8, 9

more layers

12

Fiber mat

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1032342 [0004, 0021, 0032]

Cited non-patent literature

• Standard EN 13432 "Requirements for the recovery of packaging by composting and biodegradation" [0009]

Claims (15)

Absorbent fibrous mat comprising an absorbent layer of substantially biodegradable materials and optionally further layers, characterized in that the absorbent layer contains superabsorbent polymers based on polysaccharides. Fiber mat according to claim 1, characterized in that it is at least 95% biodegradable. A fibrous mat according to claim 1 or 2, characterized in that the polysaccharide-based polymer is a graft copolymer obtained by reacting polysaccharides with acid group-containing grafting reagents to form a graft copolymer and then saponifying the obtained polymer. Fiber mat according to claim 1 or 2, characterized in that the superabsorbent polymer is a polymer based on crosslinked polysaccharides. Fiber mat according to claim 4, characterized in that the superabsorbent polymer is in the form of a nanocomposite of crosslinked polysaccharides and silicates. Fiber mat according to one of claims 1 to 5, characterized in that the absorbent layer of pulp or cellulose-related materials is constructed. Fiber mat according to one of claims 1 to 6, characterized in that the absorbent layer is a non-woven. Fiber mat according to claim 7, characterized in that the absorbent layer of cellulose fibers is provided with over the surface of the mat distributed embossing areas in which the pulp fibers are pressed together more than in the other areas. Fiber mat according to claim 8, characterized in that the embossed areas are frustoconical or truncated pyramidal. Fiber mat according to one of the preceding claims, characterized in that the absorbent layer consists of air-laid fibers of defiberized pulp (wood pulp). Fiber mat according to one of the preceding claims, characterized in that the superabsorbent polymers are particulate and distributed in layers or homogeneously distributed in the absorbent layer. Fiber mat according to one of the preceding claims, characterized in that it has as further layers a base layer and / or a cover layer. Fiber mat according to claim 12, characterized in that the base layer and / or the cover layer are selected from film and nonwoven materials on a synthetic or natural basis. Fiber mat according to claim 13, characterized in that the base layer and / or cover layer are selected from biodegradable films, breathable films, nonwoven and nonwovens or perforated films. A fibrous mat according to claim 14, characterized in that the breathable film is a perforated two- and / or three-dimensional film, a breathable SMS, nonwoven (nonwoven) of natural or synthetic fibers, a laminate of different materials, such as nonwoven and breathable film (BTBS Films = Breathable film textile backsheet) is.

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