WO1998051396A1

WO1998051396A1 - Heat-sealable filter material with biodegradable polymers

Info

Publication number: WO1998051396A1
Application number: PCT/EP1998/002553
Authority: WO
Inventors: Ralf Timmermann; Ernst Grigat; Wolfgang Schulz-Schlitte; Sabine Schroft; Richard Grangladen; Günter Heinrich
Original assignee: Bayer Aktiengesellschaft; Papierfabrik Schoeller & Hoesch Gmbh & Co. Kg
Priority date: 1997-05-13
Filing date: 1998-04-30
Publication date: 1998-11-19
Also published as: AU7651198A; DE19719807A1; AU743370B2; NO995401D0; CA2289739A1; NO995401L; KR20010012495A; JP2001524873A; CN1255072A; TW505722B; EP0981400A1

Abstract

The invention relates to a filter material comprising at least two layers, where at least one layer contains natural fibres and at least one layer contains biodegradable thermoplastic fibres. Said thermoplastic fibres are chosen from among the group of aliphatic or partly aromatic polyester amides, aliphatic or partly aromatic polyesters, aliphatic or partly aromatic polyester urethanes, and aliphatic or aliphatic-aromatic polyester carbonates.

Description

Heat sealable filter material with biodegradable polymers

The invention relates to a filter material consisting of at least one layer of natural fibers and at least a second layer of heat-sealable synthetic material which is biodegradable.

EP-A 0 380 127 A2, for example, describes a heat-sealable teabag paper and the process for producing it, the heat-sealing phase containing polyethylene and / or polypropylene and / or a copolymer of nylon chloride and vinyl acetate and the weight per unit area of this material between 10 and 15 g / m ² .

EP-A 656 224 (application number 94 107 709.1) describes a filter material, in particular for the production of tea bags and coffee bags or filters, with a basis weight between 8 and 40 g / m ² , in which the heat-sealing layer consists of plastic fibers, preferably polypropylene or polyethylene, which is placed in the heated state on the first layer consisting of natural fibers.

The German application DE-A 2 147 321 (US priority 23.09.70, US 74 722) describes a thermoplastic, heat-sealable composition which consists of a polyolefin powder (polyethylene or polypropylene) which is composed of a nylon chloride / Vinyl acetate copolymer is embedded. This material is also used for the heat-sealable finishing of paper-based fiber material.

All of the filter materials mentioned require a proportion of at least 20 to 30% by weight of thermoplastic material, based on the total weight per unit area of the filter material, in order to produce a filter bag by heat sealing.

It is known that the used filter materials, for example tea bags, coffee bags or other filters, are disposed of in a compost heap or in the organic waste bin. After a certain period of time, which depends on other parameters such as temperature, air humidity, microorganisms, etc., the natural fiber components of the filter bag disintegrate and biodegrade, while the thermoplastic polymer fiber network is preserved and the quality of the compost is reduced.

On the other hand, it is not possible to separate the natural fiber component from the thermoplastic, non-biodegradable polymer, i.e. the used filter bag should be sent to the non-recyclable waste (gray bin).

The aim of the invention is therefore to create a completely biodegradable, heat-sealable filter material that is compostable and therefore also represents the cheapest and most economical and ecological solution. In addition, ner processes for the production of such filter materials are to be described.

The invention relates to a filter material consisting of an at least two-layer structure, at least one layer containing natural fibers and one layer of biodegradable thermoplastic fibers, the thermoplastic

Fibers are selected from the group of aliphatic or partially aromatic polyester amides, aliphatic or partially aromatic polyesters, aliphatic or partially aromatic polyester urethanes, aliphatic or aliphatic-aromatic polyester carbonates and can also be a mixture of two or more of these polymers.

The thermoplastic fibers can be placed on the layer of natural fibers both in one operation on the paper machine, and, in the heated state, can be deposited on this layer of paper made of natural fibers by meltblowing and melted, and both with and with each other the paper layer are fused.

The first layer of the filter material generally has a basis weight between 8 and 40 g / m ² , preferably from 10 to 20 g / m ² and an air permeability of 300 to 4,000 l / m ² -sec (DIΝ 53 887), preferably from 500 to 3,000 l / m ² -sec. The second layer of the filter material preferably has a basis weight of 1 to 15 g / m ² , preferably 1.5 to 10 g / m ² .

The first layer of the filter material made of natural fibers is preferably designed to be wet-strength.

The filter material is used, for example, for the production of tea bags, coffee bags or tea or coffee filters.

The filter material can be produced as follows:

In a first stage, an aqueous suspension of the natural fibers is applied to a paper machine screen and in a second stage the heat-sealable, biodegradable polymer fibers are deposited on the natural fiber layer in such a way that they partially penetrate the natural fiber layer, the penetration of the two

Layers through which the degree of drainage on the sieve can be adjusted. Known natural fibers such as hemp, manila, jute, sisal and other long-fiber wood pulp are used for the first layer and are produced in a manner known per se on a paper machine.

According to the invention, a biodegradable thermoplastic polymer or a mixture of the following polymers in fiber form is used for the second layer, which is selected from the group of aliphatic or partially aromatic polyester amides, aliphatic or partially aromatic polyesters, aliphatic or partially aromatic polyester urethanes, aliphatic or aliphatic -aromatic polyester carbonates.

Suitable biodegradable and compostable polymers are aliphatic or partially aromatic polyesters, thermoplastic aliphatic or partially aromatic polyester urethanes, aliphatic or aliphatic-aromatic polyester carbonates, aliphatic or partially aromatic polyester amides. The following polymers are suitable:

Aliphatic or partially aromatic polyester

A) aliphatic bifunctional alcohols, preferably linear C ₂ to o-dialcohols such as ethanediol, butanediol, hexanediol or particularly preferably butanediol and / or optionally cycloaliphatic bifunctional alcohols, preferably having 5 or 6 carbon atoms in the cycloaliphatic ring, such as cyclohexanedimethanol , and / or partially or completely instead of the diols monomeric or oligomeric polyols based on ethylene glycol, propylene glycol, tetrahydrofuran or copolymers thereof with molecular weights up to 4000, preferably up to 1000, and / or optionally small amounts of branched bifunctional alcohols, preferably C ₃ -C 1 _2- alkyldiols, such as neopentylglygol, and in addition, if appropriate, small amounts of higher-functional alcohols, such as 1,2,3-propanetriol or trimethylolpropane, and from aliphatic bifunctional acids, preferably C -C ₁₂ -alkyldicarboxylic acids, such as and preferably succinic acid, Adi pinic acid and / or optionally aromatic bifunctional acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and additionally optionally small amounts of higher functional acids such as trimellitic acid or

B) from acid- and alcohol-functionalized building blocks, preferably with 2 to 12 carbon atoms in the alkyl chain, for example hydroxybutyric acid, hydroxyvaleric acid, lactic acid, or their derivatives, for example ε-caprolactone or dilactide,

or a mixture and / or a copolymer of A and B,

the aromatic acids not more than 50 wt .-%, based on all

Acids, make out. Aliphatic or partially aromatic polyester urethanes

C) aliphatic bifunctional alcohols, preferably linear C ₂ to cio dialcohols such as ethanediol, butanediol, hexanediol, particularly preferably butanediol and / or optionally cycloaliphatic bifunctional alcohols, preferably with a C ₅ - or Cβ-cycloaliphatic ring, such as for example Cyclohexanedimethanol, and / or partially or completely instead of the diols, monomeric or oligomeric polyols based on ethylene glycol, propylene glycol, tetrahydrofuran or copolymers thereof with molecular weights up to 4000, preferably up to 1000, and / or optionally small amounts of branched bifunctional alcohols, preferably C ₃ - C ₂ -alkyldiols, such as neopentylglygol, and additionally optionally small amounts of higher-functional alcohols, preferably C ₃ -C ₂ -alkyl polyols, such as 1,2,3-propanetriol or trimethylolpropane, and from aliphatic see bifunctional acids, preferably C ₂ -C _{] 2} alkyl dicarboxylic acids, such as In some cases and preferably succinic acid, adipic acid, and / or optionally aromatic bifunctional acids such as, for example, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and additionally optionally small amounts of higher-functional acids such as trimellitic acid or

D) from acid- and alcohol-functionalized building blocks, preferably with 2 to 12 carbon atoms, for example hydroxybutyric acid, hydroxyvaleric acid, lactic acid, or their derivatives, for example ε-caprolactone or dilactide,

or a mixture and / or a copolymer of C and D,

the aromatic acids making up no more than 50% by weight, based on all acids;

E) from the reaction product of C and / or D with aliphatic and / or cycloaliphatic bifunctional and in addition, if appropriate, more highly functional nell isocyanates, preferably with 1 to 12 carbon atoms or 5 to 8 carbon atoms in the case of cycloaliphatic isocyanates, for example tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, optionally additionally with linear and / or branched and / or cycloaliphatic bifunctional and / or higher functional alcohols, preferably C ₃ -C 8 alkyl di- or polyols or 5 to 8 C atoms in the case of cycloaliphatic alcohols, for example ethanediol, hexanediol, butanediol, cyclohexanedimethanol, and / or optionally additionally with linear and / or branched and / or cycloaliphatic bifunctional and / or higher functional amines and / or amino alcohols with preferably 2 to 12 carbon atoms in the alkyl chain, for example

Ethylenediamine or aminoethanol, and / or optionally further modified amines or alcohols, for example ethylenediaminoethanesulfonic acid, as free acid or as salt,

wherein the ester content C) and / or D) is at least 75% by weight, based on the sum of C), D) and E).

Aliphatic or aliphatic-aromatic polyester carbonates

F) aliphatic bifunctional alcohols, preferably linear C ₂ to cio dialcohols such as, for example, ethanediol, butanediol, hexanediol or particularly preferably butanediol and / or optionally cycloaliphatic bifunctional alcohols, preferably having 5 to 8 C atoms in the cycloaliphatic ring, such as, for example, cyclohexanedimethanol , and / or partially or completely instead of the diols monomeric or oligomeric polyols based on ethylene glycol,

Propylene glycol, tetrahydrofuran or copolymers thereof with molecular weights up to 4000, preferably up to 1000, and / or optionally small amounts of branched bifunctional alcohols, preferably with C ₂ -C ₂ -alkyldicarboxylic acids, such as neopentylglygol and additionally optionally small amounts of higher functional alcohols such as 1 , 2,3-propanetriol, trimethylolpropane and from aliphatic bifunctional acids such as and preferably succinic acid, adi- pinic acid and / or optionally aromatic bifunctional acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and additionally optionally small amounts of higher functional acids such as trimellitic acid or

G) from acid- and alcohol-functionalized building blocks, preferably with 2 to 12 carbon atoms in the alkyl chain, for example hydroxybutyric acid, hydroxyvaleric acid, lactic acid, or their derivatives, for example ε-caprolactone or dilactide,

or a mixture and / or a copolymer of F and G,

the aromatic acids making up no more than 50% by weight, based on all acids,

H) a carbonate fraction which is produced from aromatic bifunctional phenols, preferably bisphenol-A, and carbonate donors, for example phosgene, or a carbonate fraction which is derived from aliphatic carbonic acid esters or their derivatives such as chlorocarbonic acid esters or aliphatic carboxylic acids or their derivatives such as salts and carbonate donors, for example phosgene is produced, wherein

the ester fraction F) and / or G) at least 70% by weight, based on the sum of

F), G) and H);

Aliphatic or partially aromatic polyester amides

I) aliphatic bifunctional alcohols, preferably linear C ₂ to Cio dialko- hols such as ethanediol, butanediol, hexanediol, particularly preferably butanediol, and / or optionally cycloaliphatic bifunctional Alcohols, preferably with 5 to 8 carbon atoms, such as cyclohexanedimethanol, and / or partially or completely instead of the diols, monomeric or oligomeric polyols based on ethylene glycol, propylene glycol, tetrahydrofuran or copolymers thereof with molecular weights up to 4,000, preferably up to 1,000, and / or optionally small amounts of branched bifunctional alcohols, preferably C ₃ -C ₁₂ alkyldiols, such as neopentylglygol and additionally optionally small amounts of higher functional alcohols, preferably C ₃ -C ₁₂ alkylpolyols, such as 1,2,3-propanetriol, trimethylolpropane and from aliphatic bifunctional acids, preferably with 2 to 12 carbon atoms in the alkyl chain, such as, for example and preferably, succinic acid, adipic acid and / or optionally aromatic bifunctional acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and, if appropriate, small amounts of higher functions ll acids such as trimellitic acid or

K) from acid- and alcohol-functionalized building blocks, preferably with 2 to 12 carbon atoms in the carbon chain, for example hydroxybutyric acid, hydroxyvaleric acid, lactic acid, or their derivatives, for example ε-caprolactone or dilactide,

or a mixture and / or a copolymer of I) and K),

the aromatic acids making up no more than 50% by weight, based on all acids,

L) an amide portion of aliphatic and / or cycloaliphatic bifunctional and / or optionally small amounts of branched bifunctional amines, linear aliphatic C to Cio-diamines are preferred, and additionally optionally small amounts of higher-functional amines, among the amines preferably hexamethylenediamine, isophoronediamine and particularly preferred

Hexamethylenediamine, and from linear and / or cycloaliphatic bifunctional acids, preferably with 2 to 12 carbon atoms in the alkyl chain or C5 or Cβ ring in the case of cycloaliphatic acids, preferably adipic acid, and / or possibly small amounts of branched bifunctional and / or optionally aromatic bifunctional acids such as, for example, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and additionally optionally small amounts of higher functional acids, preferably with 2 to 10 carbon atoms, or

M) from an amide portion of acid- and amine-functionalized building blocks, preferably with 4 to 20 carbon atoms in the cycloaliphatic chain, preferably ω-laurolactam, ε-caprolactam, particularly preferably ε-caprolactam,

or a mixture of L) and M) as an amide component, wherein

the ester fraction I) and / or K) is at least 30% by weight, based on the sum of I), K), L) and M), preferably the weight fraction of the ester structures is 30 to 70

% By weight, the proportion of the amide structures is 70 to 30% by weight.

During the manufacturing process, the synthetically biodegradable heat-sealing fibers of the second layer partially penetrate the first layer and, during the drying process on the paper machine, envelop the natural fibers in the molten state. The necessary pores for filtration are left free.

The invention is explained below with reference to the drawing.

1 shows the various stages in the formation of the invention

Filter material made of natural fibers and synthetic fibers in a general, roughly schematic representation.

In Fig. 1, the formation of the filter material according to the invention is shown in a schematic representation. The formation of a first fiber layer is shown in FIG

Natural fibers 1 and the formation of a second fiber layer of synthetic, biodegradable heat-sealable fibers 2 is shown. The formation of the second Layer with the fibers 2 thus takes place by deposition over the first layer, which is formed by the natural fibers 1. In the drawing, the natural fibers 1 are hatched horizontally to distinguish them, while the synthetic fibers 2 are hatched approximately vertically.

Fig. Lb) shows how a partial penetration of the two layers is achieved by the described dewatering of the two layers, in particular the second layer with the fibers 2, so that the synthetic fibers 2 get between the natural fibers 1.

In a further production step, the partially penetrating layers 1 and 2 are dried and heated in such a way that the synthetic fibers 2 melt and, during re-consolidation, lay around the fibers 1 in such a way that they are at least partially covered. The filter material has thus become heat sealable (Fig. Lc).

Fig. 2 shows the basic structure of a paper machine, as it can be used to produce a filter material according to the invention. First, a suspension "A" is formed from the ground natural fibers and water, and also a suspension "B" from the partially ground synthetic fibers and water.

These two suspensions A and B are fed from the respective containers (3 and 4) via the so-called headbox to the paper machine. This essentially has a peripheral sieve (5) which is passed over a number of dewatering chambers (6, 7 and 8).

The suspension A is passed onto the screen 5, via the first two dewatering chambers 6, via suitable pipelines and pumping devices, which are not shown in more detail, the water being sucked off through the chambers 6 and the dewatering line. A first fiber layer of natural fibers 1 is formed on the moving sieve 5. When the sieve 5 is moved further over the dewatering chambers 7, the second suspension B is fed in, Washing chambers 7 the second layer of synthetic fibers is deposited on the first layer. The drainage takes place via the drainage line. During the further movement of the screen 5 with the two fiber layers lying one on top of the other, dewatering takes place via the dewatering chambers 8, as a result of which the two layers partially penetrate one another. By setting the drainage accordingly, the penetration can be more or less strong.

The material 9 now formed from natural fibers and synthetic fibers is removed from the sieve and fed to drying. This drying can be done in different ways, e.g. by contact drying or through-flow drying.

The elements 10 only give a rough schematic indication of corresponding drying elements.

In Fig. 2 3 drying cylinders 10 are drawn, over which the shaped paper web is dried in the contact process. However, it is also practical to pass the paper web formed over only one cylinder and to dry it with hot air without the web resting on this cylinder.

The heating of the two-layer fiber material causes the synthetic fibers 2 in the mixed layer 9 to melt. During the re-consolidation at the exit of the drying station, the synthetic fibers at least partially envelop the natural fibers and the heat-sealable filter material is rolled up on a roll 11.

With regard to a second production method for a biodegradable heat-sealable filter material, the procedure is as follows:

If the biodegradable polymer is in the form of granules, it can be removed using the

Melt-blown (meltblown fibers) process formed into fibers and still hot adhesive state on a support, such as a paper made of natural fibers.

This process is part of the state of the art, but the basics of the method in FIG. 3 will nevertheless be briefly discussed:

The dried granulate 12 is transported to an extruder 13, in which it is melted and heated to the temperature required for fiber formation. This molten and heated polymer then reaches the MB nozzle 14. This nozzle has a large number of small openings through which the molten polymer is forced and drawn into fibers. These fibers 15 are caught by a strong air stream directly below this nozzle, stretched further, torn into different lengths and placed on a support, e.g. a paper 16, which lies on a suction roller 17, deposited. Since these fibers are still hot and sticky, they stick to the natural fibers of the paper. The material is then rolled up on the winder 18 in the cooled state. The typical diameter of these meltblown fibers is between 2 and 7 μm. 3 is a schematic representation of the meltblown ner driving.

Claims

claims

1. Filter material consisting of an at least two-layer structure, at least one layer of natural fibers and one layer of biodegradable thermoplastic fibers or a mixture of biodegradable fibers, the thermoplastic fibers being selected from the group of aliphatic or partially aromatic polyester amides, aliphatic or partially aromatic Polyester, aliphatic or partially aromatic polyester urethanes, aliphatic or aliphatic-aromatic polyester carbonates.

2. Filter material according to claim 1, wherein the thermoplastic fibers are selected from the following polymers:

Aliphatic or partially aromatic polyester

A) aliphatic bifunctional alcohols, preferably linear C ₂ to Cio dialcohols such as ethanediol, butanediol, hexanediol or particularly preferably butanediol and / or optionally cycloaliphatic bifunctional alcohols, preferably having 5 or 6 carbon atoms in the cycloaliphatic ring, such as cyclohexanedimethanol, and / or partially or completely, instead of the diols, monomeric or oligomeric polyols based on ethylene glycol, propylene glycol, tetrahydrofuran or copolymers thereof with molecular weights of up to 4000, preferably up to 1000, and / or optionally small amounts of branched bifunctional alcohols, preferably

C ₃ -C ₂ alkyldiols, such as neopentylglygol, and in addition, if appropriate, small amounts of higher-functional alcohols such as 1,2,3-propanetriol or trimethylolpropane and from aliphatic bifunctional acids, preferably C ₂ -C ₂ -alkyldicarboxylic acids, such as and preferably succinic acid, adipic acid and / or optionally aromatic bifunctional acids such as, for example, terephthalic acid, isophthalic acid, naph- thalinedicarboxylic acid and, if necessary, small amounts of higher functional acids such as trimellitic acid or

or a mixture and / or a copolymer of A and B,

the aromatic acids making up no more than 50% by weight, based on all acids,

Aliphatic or partially aromatic polyester urethanes

C) aliphatic bifunctional alcohols, preferably linear C ₂ to cio dialcohols such as, for example, ethanediol, butanediol, hexanediol, particularly preferably butanediol and / or optionally cycloaliphatic bifunctional alcohols, preferably with C ₅ - or Cβ-cycloaliphatic ring, such as, for example, cyclohexanedimethanol, and / or partially or completely instead of the diols, monomeric or oligomeric polyols based on ethylene glycol, propylene glycol, tetrahydrofuran or copolymers thereof with molecular weights up to 4000, preferably up to 1000, and / or optionally small amounts of branched bifunctional alcohols, preferably C ₃ -C 1 - Alkyldiols, such as neopentylglygol, and in addition, if appropriate, small amounts of higher-functional alcohols, preferably C ₃ -C ₂ -alkyl polyols, such as 1,2,3-propanetriol or trimethylolpropane, and from aliphatic bifunctional acids, preferably C ₂ -C ₂ -alkyl dicarboxylic acids as example he and preferably succinic acid, adipic acid and / or optionally aromatic bifunctional acids such as, for example, terephthalic acid, isophthalic acid, Naphthalenedicarboxylic acid and, if necessary, small amounts of higher functional acids such as trimellitic acid or

or a mixture and / or a copolymer of C and D,

the aromatic acids making up no more than 50% by weight, based on all acids;

E) from the reaction product of C and / or D with aliphatic and / or cycloaliphatic bifunctional and additionally optionally higher-functional isocyanates, preferably with 1 to 12 C atoms or 5 to 8 C atoms in the case of cycloaliphatic isocyanates, for example tetramethylene diisocyanate, hexamethylene diisocyanate , Isophorone diisocyanate, optionally additionally with linear and / or branched and / or cycloaliphatic bifunctional and / or higher-functional alcohols, preferably C ₃ -C ₂ -alkyldi- or - polyols or 5 to 8 C atoms in the case of cycloaliphatic alcohols, for example ethanediol , Hexanediol, butanediol, cyclohexanedimethanol, and / or optionally additionally with linear and / or branched and / or cycloaliphatic bifunctional and / or higher functional amines and / or amino alcohols with preferably 2 to 12 carbon atoms in the alkyl chain, for example ethylenediamine or aminoethanol, and / or optionally further modified amines or alcohol e such as, for example, ethylenediaminoethanesulfonic acid, as the free acid or as a salt, wherein the ester content C) and / or D) is at least 75% by weight, based on the sum of C), D) and E),

Aliphatic or aliphatic-aromatic polyester carbonates

F) aliphatic bifunctional alcohols, preferably linear C ₂ to cio dialcohols such as ethanediol, butanediol, hexanediol or particularly preferably butanediol and / or optionally cycloaliphatic bifunctional alcohols, preferably having 5 to 8 C atoms in the cycloaliphatic ring, such as cyclohexanedimethanol, and / or partially or completely instead of the diols, monomeric or oligomeric polyols based on ethylene glycol, propylene glycol, tetrahydrofuran or copolymers thereof with molecular weights up to 4000, preferably up to 1000, and / or optionally small amounts of branched bifunctional alcohols, preferably with C ₂ -C ₁₂ -

Alkyldicarboxylic acids, such as neopentylglygol and additionally optionally small amounts of higher functional alcohols such as 1,2,3-propanetriol, trimethylolpropane and from aliphatic bifunctional acids such as and preferably succinic acid, adipic acid and / or optionally aromatic bifunctional acids such as terephthalic acid, isophthalic acid, Naphthalenedicarboxylic acid and, if necessary, small amounts of higher functional acids such as trimellitic acid or

G) from acid and alcohol functionalized building blocks, preferably with

2 to 12 carbon atoms in the alkyl chain, for example hydroxybutyric acid, hydroxyvaleric acid, lactic acid, or their derivatives, for example ε-caprolactone or dilactide,

or a mixture and / or a copolymer of F and G, the aromatic acids making up no more than 50% by weight, based on all acids,

H) a carbonate fraction which is produced from aromatic bifunctional phenols, preferably bisphenol-A, and carbonate donors, for example phosgene, or a carbonate fraction which is obtained from aliphatic carbonic acid esters or their derivatives such as chlorocarbonic acid esters or aliphatic carboxylic acids or their derivatives such as salts and Carbonate donors, for example phosgene, is produced, wherein

the ester fraction F) and / or G) is at least 70% by weight, based on the sum of F), G) and H);

Aliphatic or partially aromatic polyester amides

I) aliphatic bifunctional alcohols, preferably linear C ₂ to cio dialcohols such as, for example, ethanediol, butanediol, hexanediol, particularly preferably butanediol, and / or optionally cycloaliphatic bifunctional alcohols, preferably having 5 to 8 carbon atoms, such as, for example, cyclohexanedimethanol, and / or partially or completely, instead of the diols, monomeric or oligomeric polyols based on ethylene glycol, propylene glycol, tetrahydrofuran or copolymers thereof with molecular weights of up to 4000, preferably up to 1000, and / or optionally small amounts of branched bifunctional alcohols, preferably C ₃ -C 1 -alkyldiols , such as neopentyl-glygol and additionally optionally small amounts of higher-functional alcohols, preferably C ₃ -C ₂ -alkyl polyols, such as 1,2,3-propanetriol, trimethylolpropane and from aliphatic bifunctional acids, preferably with 2 to 12 carbon atoms in the alkyl chain, such as and preferred t succinic acid, adi- pinic acid and / or optionally aromatic bifunctional acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and additionally optionally small amounts of higher functional acids such as trimellitic acid or

or a mixture and / or a copolymer of I) and K),

the aromatic acids making up no more than 50% by weight, based on all acids,

L) an amide component of aliphatic and / or cycloaliphatic bifunctional and / or optionally small amounts of branched bifunctional amines, linear aliphatic C ₂ to Cio-diamines are preferred, and additionally optionally small amounts of higher-functionality amines, among the amines preferably hexamethylenediamine,

Isophoronediamine and particularly preferably hexamethylene diamine, and from linear and / or cycloaliphatic bifunctional acids, preferably with 2 to 12 carbon atoms in the alkyl chain or C ₅ - or C ₆ - ring in the case of cycloaliphatic acids, preferably adipic acid, and / or if necessary small amounts of branched bifunctional and / or optionally aromatic bifunctional acids such as, for example, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and additionally optionally small amounts of higher functional acids, preferably with 2 to 10 carbon atoms, or

M) from an amide portion of acid and amine functionalized building blocks, preferably with 4 to 20 carbon atoms in the cycloaliphatic Chain, preferably ω-laurolactam, ε-caprolactam, particularly preferably ε-caprolactam,

or a mixture of L) and M) as an amide component, wherein

the ester content I) and / or K) is at least 30% by weight, based on the sum of I), K), L) and M).

3. Filter material according to claim 1 and 2, wherein the first layer is a mixture of softwood, hardwood, manila, hemp, jute, sisal and similar natural fibers.

4. Filter material according to claim 1 to 3, wherein the first layer has a basis weight between 8 and 40 g / m ² and an air permeability of 300 to 4,000 l / m ² -s (DIN 53 887).

5. Filter material according to claims 1 to 4, wherein the second layer, consisting of the biodegradable thermoplastic fibers, has a basis weight of 1 to 15 g / m ² .

6. Filter material according to the preceding claims, wherein the first layer is made of natural fibers wet strength.

7. Use of the filter material according to the preceding claims for the production of tea bags, coffee bags or tea or coffee filters.