WO2019121322A1 - Foamed fusible fibres - Google Patents

Abstract

The invention relates to foamed fusible fibres made of biodegradable polymers, in particular fusible fibres having a fineness measured according to ISO 1144:2016-09 of 0.1 to 100 dtex and 1 to 50 dtex, and foamed staple fibres made of biodegradable polymers having a fineness measured according to ISO 1144:2016-09 of 1 to 50 dtex, foamed continuous fibres made of biodegradable polymers having a fineness measured according to ISO 1144:2016-09 of 100 to 3000 dtex, and foamed monofilaments made of biodegradable polymers having a fineness measured according to ISO 1144:2016-09 of 0.5 to 5 mm. The invention further relates to non-woven materials (non-wovens), textiles, agrotextiles or geotextiles, film strips, packaging and fishing nets containing the fibres according to the invention and to methods for producing the fibres and non-wovens according to the invention.

Description

 Foamed melt fibers

description

The invention relates to foamed melt fibers of biodegradable polymers; in particular melt fibers with a fineness measured in accordance with ISO 1144: 2016-09 from 0.1 to 100 dtex and 1 to 50 dtex, and foamed staple fibers made from biodegradable polymers with a fineness measured to ISO 1144: 2016-09 from 1 to 50 dtex, foamed endless fibers of biodegradable polymers with a fineness measured in accordance with ISO 1144: 2016-09 of 100 to 3000 dtex, foamed monofilaments of biodegradable polymers with a fineness measured in accordance with ISO 1144: 2016-09 of 0.5 up to 5 mm.

The invention furthermore relates to nonwovens (nonwovens), agrochemicals or geotextiles, film tapes, packaging and fishing nets containing the fibers according to the invention and to processes for producing the fibers and nonwovens according to the invention.

The production of fibers from thermoplastics, so-called melt fibers is known from the literature. In most cases, the aim here is that the fibers have no imperfections and thus a smooth surface, in order to be able to achieve the highest possible strength, high drawing rates and high processing speeds.

Isolated references (US Pat. Nos. 5,124,094 and 4,562,022) deal with the production of foamed melt fibers from thermoplastics such as polyamides or polyethylene terephthalate, which, however, are not biodegradable.

We have now found that foamed high-fines fibers can be made from biodegradable polymers that have very interesting properties:

The increased surface area and unevenness of the fibers due to the foaming leads to faster biodegradability due to better colonization by microorganisms, and / or faster hydrolysis. Furthermore, due to the porosity of the fiber, the already weakened polymer structure of the fiber loses its strength during the biological and / or hydrolytic degradation process, as a result of which the fiber structures, such as, for example, nonwovens, disintegrate more rapidly.

Also, the foaming-modified surface of the fibers of the present invention results in improved softness, which is otherwise experienced by e.g. can be achieved with crimping of the fibers. The fibers are easy to process, for example nonwovens.

The invention will be described in more detail below.

Biodegradable polymers are understood as meaning polymers which Composting requirements according to DIN EN 13432: 2000-12.

In general, biodegradability causes the polymer (s) to disintegrate in a reasonable and detectable time. Degradation may be enzymatic, hydrolytic, oxidative and / or by the action of electromagnetic radiation, for example UV radiation. The biological, enzymatic degradation is carried out by the action of microorganisms such as bacteria, yeasts, fungi and algae. The biodegradability can be quantified, for example, by mixing polyesters with compost and storing them for a certain period of time. For example, according to DIN EN 13432 C0 ₂ -free air is allowed to flow through ripened compost during composting and subjected to a defined temperature program. Here, the biodegradability on the

Ratio of the net C0 ₂ release of the sample (after subtraction of the C0 ₂ release by the compost without sample) to the maximum C0 ₂ release of the sample (calculated from the

Carbon content of the sample) as a percentage of biodegradation.

Biodegradable polyesters (mixtures) usually show clear degradation phenomena such as fungal growth, cracking and hole formation after only a few days of composting.

Other methods of determining biodegradability are described, for example, in ASTM D 5338 and ASTM D 6400 and ISO 18606 and ISO 17800.

Suitable biodegradable polymers are, for example, polylactic acid,

Polyhydoxyalkanoates, polycaprolactone and especially aliphatic-aromatic polyesters such as polybutylene adipate coterephthalate, polybutylene sebacate coterephthalate or preferably aliphatic polyesters such as polybutylene succinate or polybutylene succinate-co-adipate. Of course, mixtures of several such biodegradable polymers are suitable.

Preferred biodegradable polymers are polyesters based on aliphatic or aliphatic and aromatic dicarboxylic acids and aliphatic dihydroxy compounds. The latter are also referred to as aliphatic-aromatic or partially aromatic polyesters. Common to these polyesters is that they are biodegradable according to DIN EN 13432.

Especially preferred are polyesters containing as essential components:

A1) 40 to 100 mol%, based on the components A1) to A2), of an aliphatic C ₄ -Cie dicarboxylic acid or mixtures thereof,

A2) 0 to 60 mol%, based on the components A1) to A2), of an aromatic Dicarboxylic acid or mixtures thereof,

B) 98.5 to 100 mol%, based on components A1) to A2), of a diol component of a C _{4 to} C 12 alkanediol or mixtures thereof; and

C) 0 to 1, 5 wt .-%, and preferably 0.05 to 1 wt .-%, based on the components A1) to A2) and B, one or more compounds selected from the

Group consisting of:

C1) a compound having at least three groups capable of ester formation,

C2) a compound having at least two isocyanate groups,

C3) a compound having at least two epoxide groups. By partially aromatic polyesters according to the invention, polyester derivatives are also to be understood which contain up to 10 mol% of functions other than ester functions

Polyetheresters, polyesteramides or polyetheresteramides and polyesterurethanes. Suitable partially aromatic polyesters include linear non-chain extended polyesters (WO 92/09654). Preferred are chain-extended and / or branched partially aromatic polyesters. The latter are from the documents mentioned above, WO 96/15173 to 15176, 21689 bis

21692, 25446, 25448 or WO 98/12242, to which reference is expressly made. Mixtures of different partially aromatic polyesters are also possible. Interesting recent developments are based on renewable raw materials (see WO-A 2006/097353, WO-A 2006/097354 and EP 08165372.7). In particular, are under

semiaromatic polyesters such as Ecoflex® (BASF SE) and Eastar® Bio, Origo-Bi® (Novamont).

Particularly preferred partially aromatic polyesters include polyesters containing as essential components:

A1) 40 to 60 mol%, preferably 45 to 60 mol%, based on the components A1) to A2), of an aliphatic dicarboxylic acid selected from the group consisting of

Succinic acids, adipic acid, sebacic acid and azelaic acid, or mixtures thereof,

A2) 40 to 60 mol%, preferably 40 to 55 mol%, based on the components A1) to A2) of an aromatic dicarboxylic acid selected from the group consisting of terephthalic acid and 2,5-furandicarboxylic acid or mixtures thereof, B) 98.5 to 100 mol%, preferably 99 to 99.95 wt .-%, based on the components A1) to A2), a diol component of a C2 to C4 alkane diol, preferably a 1, 3-propanediol or 1,4-butanediol or mixtures thereof; and

C) 0 to 1, 5 wt .-%, preferably 0.05 to 1 wt .-%, based on the components A1) to A2) and B), one or more compounds selected from the group consisting of:

C1) a compound having at least three groups capable of ester formation,

 preferably glycerol or pentaerythritol,

C2) a compound having at least two isocyanate groups, preferably 1, 6-hexamethylene diisocyanate or 1, 6-hexamethylene diisocyanurate, and

C3) a compound having at least two epoxide groups, preferably one. Copolymer of styrene, glycidyl (meth) acrylate and (meth) acrylate.

Suitable aliphatic acids and the corresponding derivatives A1 are generally those having 4 to 18 carbon atoms, preferably 4 to 10 carbon atoms, more preferably 4 to 10 carbon atoms. They can be both linear and branched. In principle, however, can also dicarboxylic acids with a larger number of

Carbon atoms, for example, be used with up to 30 carbon atoms.

Examples are succinic acid, glutaric acid, 2-methylglutaric acid, 3-methylglutaric acid, a-ketoglutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, brassylic acid, fumaric acid, 2,2-dimethylglutaric acid, suberic acid (suberic acid), diglycolic acid, glutamic acid, aspartic acid , Itaconic acid and maleic acid. The can

Dicarboxylic acids or their ester-forming derivatives, used individually or as a mixture of two or more thereof.

Succinic acid, adipic acid, azelaic acid, sebacic acid or their respective ester-forming derivatives or mixtures thereof are preferably used. Succinic acid, adipic acid or sebacic acid or their respective ester-forming derivatives or mixtures thereof are particularly preferably used. Succinic acid, azelaic acid, sebacic acid and brassylic acid also have the advantage that they are accessible from renewable raw materials.

Particularly preferred are the following aliphatic-aromatic polyesters: Polybutylene adipate coterephthalate (PBAT), polybutylene sebacate coterephthalate (PBSeT) or polybutylene succinate coterephthalate (PBST), polybutylene azelate coterephthalate, and most preferably polybutylene adipate coterephthalate (PBAT) and polybutylene sebacate coterephthalate (PBSeT).

Further preferred are mixtures of polybutylene adipate coterephthalate (PBAT) and polybutylene sebacate coterephthalate (PBSeT).

The aromatic dicarboxylic acids or their ester-forming derivatives A2 may be used singly or as a mixture of two or more thereof. Particularly preferred

Terephthalic acid and 2,5-furandicarboxylic acid or their ester-forming derivatives such as

Dimethyl terephthalate or dimethyl furanate.

In general, the diols B are selected from branched or linear alkanediols having 2 to 12 carbon atoms, preferably 3 to 6 carbon atoms, or cycloalkanediols having 5 to 10 carbon atoms.

Examples of suitable alkanediols are ethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 2-butanediol, 1, 4-butanediol, 1, 5-pentanediol, 2,4-dimethyl-2-ethylhexane-1, 3 diol, 2,2-dimethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 2,2,4-trimethyl - 1, 6-hexanediol, in particular ethylene glycol, 1, 3-propanediol, 1, 4-butanediol and 2, 2-dimethyl-1, 3-propanediol (neopentyl glycol). Particularly preferred are 1, 4-butanediol and 1, 3-propanediol which also have the advantage that they are available as a renewable raw material. It is also possible to use mixtures of different alkanediols.

Aliphatic, biodegradable polyesters are understood as meaning polyesters of aliphatic diols and aliphatic dicarboxylic acids such as polybutylene succinate (PBS), polybutylene adipate (PBA), polybutylene succinate-coadipate (PBSA), polybutylene succinate cosebacate (PBSSe), polybutylene sebacate (PBSe) or corresponding polyesteramides or polyester urethanes. The aliphatic polyesters PBS and PBSA, for example, are marketed by the companies Showa Highpolymers under the name Bionolle® and by Mitsubishi (MCC) under the name GSPLA® and by PTTMCC under the name BioPBS®. More recent developments are described in WO 2010/03471 1.

Preferably, the aliphatic polyesters are composed of the following components:

Ai) 90 to 100 mol%, based on the components Ai to Aii, succinic acid; Aii) 0 to 10 mol%, based on the components Ai to Aii, one or more C6-C18 dicarboxylic acids;

B) 99 to 100 mol%, based on the components Ai to Aii and B, 1, 3 propanediol or 1, 4-butanediol or mixtures thereof;

C) 0 to 1% by weight, based on the components Ai to Aii, B and C of a diisocyanate, preferably 1, 6 hexamethylene diisocyanate and / or a compound having at least three ester-capable groups, preferably glycerol or pentaerythritol;

The biodegradable polyesters may also contain mixtures of the previously described aliphatic-aromatic polyesters and purely aliphatic polyesters such as

for example, mixtures of polybutylene adipate coterephthalate and polybutylene succinate.

The abovementioned aliphatic and aliphatic-aromatic polyesters generally have a number-average molecular weight (Mn) in the range from 1000 to 100,000, in particular in the range from 9,000 to 75,000 g / mol, preferably in the range from 10,000 to 50,000 g / mol, and Melting point in the range of 60 to 170, preferably in the range of 80 to 150 ° C.

The melt volume rate (MVR) according to EN ISO 1133 (190 ° C, 2.16 kg weight) of the aliphatic or aliphatic-aromatic polyesters is generally from 0.1 to 50, preferably from 2.0 to 30, and most preferably from 5 to 25 cm ^3/10 minutes.

The biodegradable polymers described above may contain, in effective amounts, other additives such as dyes, pigments, fillers, flame retardants, synergists for flame retardants, antistatics, stabilizers (such as hydrolysis stabilizers), surfactants, plasticizers, and infra-red opacifiers.

If fillers are used, they may be inorganic and / or organic. If fillers are included, these are, for example, organic and inorganic powders or fibrous materials and mixtures thereof. As organic fillers, for example, wood flour, starch, flax, hemp, ramie, jute, sisal, cotton, cellulose or

Aramid fibers are used. Suitable inorganic fillers are, for example, silicates, barite, glass beads, zeolites, metals or metal oxides. Particular preference is given to pulverulent inorganic substances such as chalk, kaolin, aluminum hydroxide,

Magnesium hydroxide, aluminum nitrite, aluminum silicate, barium sulfate, calcium carbonate,

Calcium sulfate, silicic acid, quartz flour, aerosil, alumina, mica or wollastonite, or spherical or fibrous inorganic materials such as iron powder, glass beads, glass fibers or carbon fibers used. The average particle diameter or, in the case of fibrous fillers, the length of the fibers should be in the range of the cell size or smaller. A mean particle diameter or an average length of the fibers is preferably in the range from 0.1 to 100 gm, in particular in the range from 0.5 to 10 gm. The fibers can also be used in mixtures with the biodegradable ones described above

Synthetic fibers are used.

Suitable flame retardants are, for example, tricresyl phosphate, tris (2-chloroethyl) phosphate, tris (2-chloropropyl) phosphate, tris (1, 3-dichloropropyl) phosphate, tris (2,3-dibromopropyl) phosphate and tetrakis (2 chloroethyl) ethylene. Besides the abovementioned halogen-substituted phosphates, it is also possible to use inorganic flame retardants with red phosphorus, aluminum oxide hydrate, antimony trioxide, arsenic trioxide,

Ammonium polyphosphate and calcium sulfate or cyanuric acid derivatives, for example melamine or mixtures of at least two flame retardants, for example ammonium phosphate and melamine and optionally starch and / or expandable graphite used for flame retardancy of the foamed thermoplastic elastomers produced. In general, it has proven expedient to use from 0 to 50% by weight, preferably from 5 to 25% by weight, of the flame retardants or flame retardant mixtures, based on the total weight of the blowing agent-containing system, if a particle size in the range from 0.1 to 50 gm, in particular 0.5-10 gm can be achieved

The additives mentioned can be added to the biodegradable polymers as described above, or later in the extrusion for fiber or nonwoven production

be used for example in the form of masterbatches or dry blends in the respective process.

In the following, preferred processes for the production of the fibers and nonwovens according to the invention are described: a) Extruder foams b) Direct extrusion c) Autoclave driving

Extruder foams (a)

The production of the fibers or fleeces takes place continuously in the stages: i) melting the polymer and placing the polymer with 0.01 to 20 wt .-% based on the polymer of a blowing agent and optionally a nucleating agent such as talc and pressing the blowing agent-containing and optionally nucleated polyester melt by a to a temperature between 150 ° C. and 280 ° C tempered spinneret plate.

The propellant may be a chemical propellant such as Hydrocerol® (especially CT3178) or baking powder or a physical propellant such as

Carbon dioxide and / or nitrogen and / or pentane, butane, alcohol or water. The blowing agent can already be introduced in an upstream step by means of compounding and / or tumbling and / or mixing. ii) foaming the polymer melt and stretching the resulting foamed fibers in an expansion zone e.g. a spunbond, meltblown nonwoven or

Fiber plant. iii) depositing the webs on a belt or winding the fibers on, for example, coils.

In the melt blown process and in the spunbond process, a polymer melt mixed with a blowing agent and optionally further additives is passed through the

Spinneret plate pressed. The preparation of the blowing agent and optionally further

Additives containing polymer melt is generally carried out with the aid of an extruder and / or a melt pump. These apparatuses are also used to generate the necessary pressure to press the polymer melt through the spinneret plate. When using an extruder, for example a twin-screw extruder, the polymer is first plasticized and optionally mixed with auxiliaries. During mixing, the material contained in the extruder is in the direction of tempered

Spinneret plate transported. If the blowing agent has not already been introduced into the extruder with the polymer at the beginning, this can be added to the material after passing through a section in the extruder. The blowing agent and the polymer are mixed while passing through the remaining extruder section. The melt is brought to the temperature required for the subsequent spinning of 150 to 280 ° C and preferably 200 to 240 ° C. The pressure required for pressing the melt through the spinneret plate can be applied, for example, with a melt pump. Alternatively, the required pressure is generated by the corresponding geometry of the extruder and in particular the extruder screw. Through the tempered spinneret plate passes the

Polymer melt in the expansion section.

In the expansion section, the polymer pressed by the tempered spinneret plate becomes shaped into strands. In and especially directly after the spinneret plate, the fibers foam strongly. They are stretched by a gas stream and cooled. The shape of the resulting foamed fibers is dependent on the one hand on the shape and size of the openings in the spinneret plate, on the other hand, the shape is dependent on the pressure with which the melt is forced through the holes of the spinneret plate and the

Speed of the gas flow in the expansion section.

Through the expansion section flows a tempered gas. It is preferred that this gas be replaced by suitable constructions - such as pressurized encapsulation

Expansion section - is under an overpressure. This overpressure is 0.01 bar to 5 bar above the ambient pressure.

When using a propellant mixture of carbon dioxide and nitrogen in

Mixing ratio 10: 1 to 2: 1, the gas pressure in the expansion zone is preferably 0.5 to 5 bar and particularly preferably 1 to 3 bar above the ambient pressure. Overall, this driving style provides highly expanded, high surface area fibers. It can also be used exclusively as carbon dioxide blowing agent.

It is also possible to operate the expansion section without pressure.

With the controlled gas temperature and possibly the specific gas pressure in the

Expansion distance is avoided that the propellant-containing polymer melt expands uncontrollably without a foamed fiber can form. Although such fibers may initially have a low bulk density, they readily collapse again. The result in such cases are inhomogeneous fibers of high bulk density and low elasticity. By the method according to the invention, the expansion of the fibers is controlled slowed down, so that structured fibers are formed. The fibers preferably have an open-celled skin and in some cases also show a cellular structure. The maximum thickness of the foamed individual fibers is preferably in the range from 0.1 to 100 μm, in particular in the range from 1 to 50 μm.

The expansion of the fibers is controlled by adjusting the pressure and temperature of the gas in the expansion zone, as well as by adjusting the temperature of the spinneret plate. If the fibers expand too fast, the gas pressure is usually increased in the expansion zone and / or the gas temperature in the expansion zone is lowered. The increased pressure of the tempered gas surrounding the fibers counteracts the expansion effect of the propellant and slows the expansion of the fibers. At a relative to the used Propellant to high gas pressure or too low a temperature, expansion of the fibers can be hindered or even completely prevented, so that fibers are formed with too high bulk density. In this case, the gas pressure in the expansion section is lowered and / or the temperature is raised.

In addition to the adaptation of the pressure and / or the temperature in the expansion section, the expansion of the fibers can be influenced in particular by the temperature of the spinneret plate. The temperature in the expansion zone is preferably between 5 ° C and 90 ° C, and more preferably at 30 to 80 ° C. The temperature of the tempered

Spinneret plate is preferably between 150 ° C and 280 ° C, more preferably, a temperature of the spinneret plate between 200 ° C and 240 ° C.

However, it is also possible by using suitable polymers and blowing agents to obtain expanded fibers and nonwovens, without a pressure encapsulation or pressurization takes place.

In the final step of process (iii), the foamed fibers are laid down, for example, on a web for the production of nonwovens and, if necessary, welded by pressure, temperature or other suitable means (for example calender rolls). This step is known to the person skilled in the art.

The foamed fibers can also be wound up on reels as separated chamfers in step iii.

The use of such extrusion processes to produce expanded fibers enables continuous production and hence rapid processing of different polymers as well as the rapid change of further properties, such as the color of the expanded fibers produced.

It is also advantageous that the process can do without the use of combustible propellant. Furthermore, the foamed fibers produced need not be stored before delivery until the flammable propellant used has volatilized.

Surprisingly, it has been found that the lowest densities are not obtained as expected with the highest possible propellant quantities, but that a propellant amount, for example when using carbon dioxide / nitrogen mixtures of at most 10 wt .-%, preferably of at most 5 wt .-% and in particular of a maximum of 3 wt .-%, based on the polymer melt, lead to a particularly low fiber density. The optimum amount of blowing agent used depends on the polymer used and the composition of the blowing agent, but is preferably between 1 and 10 wt .-%.

Direct extrusion (b) Preference is furthermore given to a special embodiment of the product described under a)

Extruder foaming, which is referred to in the following as direct extrusion (b). The

Direct extrusion takes place without intermediate isolation of the biodegradable polymer produced, in particular an aliphatic or aliphatic-aromatic polyester.

Here, the polyester, which has been produced batchwise, semicontinuously or continuously in a first stage (x), is introduced directly as a melt via a heated pipe in extruder foams (a). This can save energy and also costs for the granulation and the subsequent melting of the polymer.

In detail, this process alternative is as follows: Process for the production of expanded fibers or nonwovens from one or more polyesters based on biodegradable polymers, in particular polyesters of aliphatic or aliphatic and aromatic dicarboxylic acids and aliphatic diols, comprising the steps:

(X) addition of aliphatic or aliphatic and aromatic dicarboxylic acids and aliphatic diols used to prepare a polyester melt, and

 optionally further starting materials in a polymer processing machine,

(i) introducing the polyester melt and adding the blowing agent to the polyester melt as described under (a) and introducing the polymer melt into a spinneret unit,

(ii) foaming the polymer melt and stretching the resulting foamed fibers in an expansion zone of e.g. a spunbond, meltblown web or fiber plant as described under (a),

(iii) depositing the webs on a belt or winding the fibers as described under (a).

Autoclave method (c) The melt fibers or nonwovens can also be produced in a conventional way (unfoamed) and then preferably exposed to blowing agent in a pressure vessel, for example an autoclave reactor, at elevated temperature and pressure, so that the melt fibers or nonwovens absorb blowing agent (hereinafter Autoclave method (c) called).

The process generally comprises the steps ca) to cd): ca) production of melt fibers or nonwovens by known processes, cb) introduction into an autoclave and an impregnation step, the gaseous medium having an impregnation temperature Ta, the absolute pressure of the gaseous medium cc) an expansion step wherein the melt fibers are subjected to a pressure reduction at a first expansion temperature Tb and expand, and cd) optionally a welding step at the welding temperature Tc.

The impregnation temperature Ta, the expansion temperature Tb and the

Welding temperature Tc depend on the type of biodegradable polymer.

The melt fibers produced by the autoclave process are characterized by densities between 1000 and 1300 g / l.

The pressure of the gaseous medium in the impregnation step c-b) is dependent on the

desired pressure drop rate and is between 1 bar and 1000 bar, preferably between 50 bar and 700 bar, more preferably between 200 bar and 600 bar. Will the

Expansion step c-c) carried out in a second apparatus, the pressure is here in the second apparatus initially between 1 bar and 200 bar, preferably between 5 bar and 35 bar and more preferably between 5 bar and 25 bar. The duration of the impregnation step c-b) depends on several factors, in particular the material and the size of the fibers, the temperature and the pressure in the pressure vessel.

Preferably, the impregnation step cb) continues until the fibers are saturated with blowing agents. The saturation of the fiber can be determined by an iterative weighing process, for example by means of a magnetic levitation balance. For impregnation, all the Professional known propellant can be used. Preference is given to physical blowing agents, for example alkanes, such as butane (n- or iso-butane), pentane (n- or iso-pentane),

 Cyclopentane or octane, carbonyl compounds such as acetone, alcohols such as ethanol, fluorinated hydrocarbons or inert gases such as argon, nitrogen or carbon dioxide. Physical blowing agents are understood to mean blowing agents whose chemical structure remains unchanged during the expansion process, whose state of aggregation can change during the expansion process and which are gaseous for expansion. Particular preference is given to using carbon dioxide or butane or mixtures of both. Furthermore, blowing agent mixtures can also be used with said combustible blowing agents.

The carbon dioxide used as blowing agent is particularly preferably in the form of a

Mixture with N ₂ used. In this case, any mixing ratio of C0 ₂ to N2 is initially possible. However, it is preferred to use as blowing agent a mixture of carbon dioxide and nitrogen containing 50 wt .-% to 100 wt .-% carbon dioxide and 0 wt .-% to 50 wt .-% nitrogen. In particular, it is preferred that the propellant contains only CO2, N2 or a mixture of these two gases and no further propellant. Preferably, a physical blowing agent is used.

The adjusted blowing agent content is between 0.1 wt .-% and 20 wt .-%, preferably between 0.5 wt .-% and 15 wt .-%, particularly preferably between 2 wt .-% and 10 wt%. As a result, with proper process control biodegradable nonwovens with densities of less than 1300 g / l with basis weights of 10 to 1500 g / m ^2, preferably from 10 to 150 g / m ^{2, can be produced} by welding in at least one form from this expanded nonwoven. As the fibers expand, pressure and temperature are selectable process parameters. A low pressure drop rate or an increased remaining pressure after the pressure reduction counteracts the expansion effect of the propellant and slows the expansion of the fiber. The lower the temperatures selected in the process, the thicker is the skin of the fibers which offers resistance to expansion. At a pressure that is too high or too low relative to the blowing agent used, expansion of the fiber can be hindered or even completely prevented, so that expanded fibers are formed with excessive density.

The expansion step c-c) is preferably carried out in an inert atmosphere.

In the expansion step c-c), the temperature is preferably on the so long

Expansion temperature Tb held until the desired expansion is reached. The progress of the expansion can be controlled by means of the pressure reduction rate of the pressure reduction, which is between 50 bar / s and 5000 bar / s, preferably between 100 bar / s and 1000 bar / s. A Reduction of the pressure with pressure drop rates from these areas is referred to in the context of the invention as a sudden pressure reduction.

The residence time in the pressure vessel, ie the duration of the impregnation step b) and the

Expansion step c-c) and optionally the expansion step b2) and the

Welding step d) is between 0.25 hours and 12 hours, preferably between 1 hour and 6 hours.

The preferred range of the selected temperatures of the gaseous medium during the impregnation step c-b) (impregnation temperature Ta) and the expansion step c-c)

(Expansion temperature Tb) is dependent on the glass transition temperature TG in the case of amorphous polymers and on the melting temperature Ts of the non-impregnated polymer in the case of semicrystalline polymers. In the context of the invention, the glass transition temperature TG is understood to mean the temperature which is defined in accordance with DIN EN ISO 1 1357-2: 2013-09. When

Melting temperature of partially crystalline thermoplastic elastomers is referred to in the context of the invention, the temperature, which is defined according to DIN EN ISO 1 1357-3: 2013- 04.

If the fibers are not welded directly in the first or second apparatus, the expanded fibers produced according to the invention can subsequently be welded or glued to nonwovens by methods known to those skilled in the art or used in other ways known to the person skilled in the art. In a further embodiment, the fibers may be partially crosslinked prior to the impregnation step c-b) by methods known in the literature, crosslinking being understood to mean long chain branching and only partially crosslinking to the extent that the thermoplastic properties are retained. This can be advantageous for the production in particular of expanded melt fibers, which essentially contain semicrystalline polymers. The crosslinking can be achieved, for example, by using crosslinking reagents, for example triallyl cyanurates or O-O-labile

Compounds (peroxides), or can be achieved by the use of electrons or gamma rays. When gamma rays are used, typical radiation doses for crosslinking are in the range of 5 kGy to 200 kGy, preferably 25 kGy to 100 kGy. Preferably, the crosslinking is achieved without the use of crosslinking reagents.

The autoclave method allows easy production of expanded melt fibers which have a low density and high porosity. Furthermore, it is with the

method according to the invention possible in a preferred embodiment the

Impregnation to carry out the expansion and, where appropriate, the welding to nonwovens in only one apparatus. Foamed melt fibers and nonwovens may be made from these melt fibers with the aforementioned methods, the biodegradable polymers preferably being biodegradable polyesters.

The production of the melt fibers is preferably carried out by melt spinning, wherein the biodegradable polymer is melted in an extruder and the blowing agent is added at a suitable point at the beginning, in the course of the extruder or at the end of the extruder and then pressed through a spinneret. A particularly efficient and processable process is obtained when 1 to 10% by weight of a chemical blowing agent based on the extruded material (in front of the die) is used.

In the following, some preferred methods of melt spinning for the production of foamed fibers in a defined fineness range will be described.

With the preferred meltblown process are very fine, foamed fibers with a thickness of 0.1 to 100 dtex, preferably 0.1 to 20 dtex and from it - alone or with other natural fibers (cellulose, cotton, lyocell, sisal, hemp, flax , Stinging nettle, etc.) or synthetic polymer fibers mixed - produced nonwovens accessible. The dtex values are determined here and below in accordance with ISO 1144: 2016-09. The fine, foamed fibers and nonwovens obtainable by the meltblown process are particularly suitable for the production of nonwovens for coffee pads, for hygiene articles such as toilet paper, moist hygiene tissues, baby diapers, sanitary napkins, tampons or incontinence products.

The likewise preferred spunbond process makes it possible to obtain fine, foamed fibers having a thickness of from 1 to 50 dtex, preferably from 1 to 15 dtex, and nonwovens produced therefrom, which are for example-as mentioned above-for the production of hygiene articles,

Filter materials and disposable clothing are suitable.

In addition, foamed staple fibers having a thickness of 1 to 100 dtex, preferably 1 to 50 dtex and a length of 1 to 50 mm, preferably 3 to 10 mm, which are suitable as carpet or paper fibers, or in the Drylaid or wetlaid process alone or with other natural fibers (cellulose, cotton, lyocell, sisal, hemp, flax, stinging nettle, etc.) or synthetic polymer fibers mixed into nonwovens for applications such Coffee pads and filter materials can be processed.

The aforementioned melt fibers and staple fibers can also be used on the nonwoven system other fibers are mixed, filed and bonded as preferably with cellulose fibers. From such nonwovens, for example, hygiene papers but also filter fleeces for foodstuffs such as coffee and beer or air filters can be produced.

With the LOY (low oriented yarn) and in particular POY (partially oriented yarn) method, in which the orientation of the polymer chains improves with increasing withdrawal speed of generally 1000 to 6000 m / min, foamed continuous fibers are in one thickness from 100 to 3000 dtex and preferably from 200 to 700 dtex, which can be used in particular as textile fibers for the production of, for example, sports shirts, underwear or

Sports shoes or in agriculture as geotextiles and agrotextiles such as twine, as a foil tape for artificial turf or carpet backing fabric, packaging (bags, nets and bags) are suitable.

Foamed monofilaments with a diameter of 0.5 to 5 mm are available, for example, with monofilament extrusion, which, in addition to the aforementioned applications, can also be used to make foil tapes (raffia), packaging (bags, sacks and big bags) and nets such as shopping bags. and fishing nets.

The fibers and nonwovens produced by the processes described above can be post-treated by methods known from the literature. For example, they may be provided with an antistatic agent, dye, hydrophobizing agent or lubricant.

Preferably, the additives such as an antistatic agent, dye, water repellents or

Lubricant in a bicomponent melt spinning process, a coextrusion in which

Outer layer of the fiber driven.

From the fibers and nonwovens according to the invention it is also possible to produce foamed shaped bodies by known processes.

For example, the fibers and nonwovens according to the invention can be applied in a continuous or discontinuous process with the aid of an adhesive, such as, for example

Polyurethane adhesive are glued together.

Preferably, however, the fibers and nonwovens of polyester according to the invention are welded together under the effect of heat. As a heat carrier, preferably steam can be used. It is also possible to bond the fibers and nonwovens according to the invention in a solvent vapor. For this purpose, one fills the fibers and nonwovens according to the invention into a mold and, after closing the mold, introduces steam or hot air, whereby the Weld fibers together. The welding can also be done continuously, for example, on tapes. It can also be used belt presses. In this way, for example, tissue, plates, profiles or webs, or other molded parts with simple or complicated geometry arise.

The present invention also relates to a foam comprising the fibers and nonwovens according to the invention, preferably prepared, by the abovementioned processes.

We have now found that the fibers and nonwovens of biodegradable polymers according to the invention - such as polylactic acid, Polyhydoxyalkanoate, polycaprolactone and especially aliphatic-aromatic polyesters such as Polybutylenadipat- coterephthalat, Polybutylensebacat-coterephthalat or preferably aliphatic polyesters such as polybutylene succinate or polybutylene succinate-coadipate - with a Basis weight from 20 to 100 g / m2 of 200-800g / l, good tensile strength, and acceptable softness and

Water vapor permeability can be produced with good distribution of moisture.

Examples:

Biodegradable polymers used: i-1 (polybutylene adipate-co-terephthalate): 87.3 kg. Were used to prepare the polyester

Dimethyl terephthalate, 80.3 kg of adipic acid, 1 17 kg of 1, 4-butanediol and 0.2 kg of glycerol mixed with 0.028 kg of tetrabutyl orthotitanate, wherein the molar ratio between

Alcohol component and acid components 1, 30 was. The reaction mixture was heated to a temperature of 180 ° C and reacted at this temperature for 6 hours. Subsequently, the temperature was raised to 240 ° C and the excess dihydroxy compound distilled off under vacuum over a period of 3h. Subsequently, 0.9 kg of hexamethylene diisocyanate were metered in slowly within 1 h at 240 ° C.

The thus obtained polyester i-1 had a melting temperature of 119 ° C and a

Molecular weight (Mn) of 23000 g / mol. i-2 (polybutylene sebacate-co-terephthalate): dimethyl terephthalate (70.1 l kg), 1,4-butanediol (90.00 kg), glycerol (242.00 g), tetrabutyl orthotitanate (260.00 g) and sebacic acid (82.35 kg) placed in a 250L kettle and the apparatus purged with nitrogen. Methanol was distilled off to an internal temperature of 200 ° C. It was cooled to about 160 ° C and condensed under vacuum (<5 mbar) to an internal temperature of 250 ° C. After reaching the desired viscosity was cooled to room temperature. The prepolyester had a viscosity of VZ = 80 ml / g.

The chain extension was carried out in a kneader. The prepolyester was melted at 220 ° C. and the melt was added dropwise at 0.3% by weight, based on the polyester i, to HDI (hexamethylene diisocyanate). The progress of the reaction was monitored by observing the torque. The reaction mixture was cooled after reaching maximum torque, and the chain-extended, biodegradable polyester was removed and characterized. The polyester i-2 had a MVR of 4.7 cm ^3/10 min. i-3 (polybutylene succinate): 82.0 g of 1,4-butanediol, 82.7 g of succinic acid, 0.09 g of glycerol and 0.13 g of titanium orthotitanate were initially introduced and melted at 120 ° C. Subsequently, the

Temperature increased to 160 ° C and distilled off water. Thereafter, vacuum was applied and the temperature increased to 250 ° C and the polycondensation to the desired

Viscosity number completed. Subsequently, 1.2 g of hexamethylene diisocyanate were added slowly at 220 ° C. within 1 h. The thus-obtained polyester i-3 had a molecular weight (Mn) of 31,000 g / mol. Chemical blowing agent: ii-1 Hydrocerol® CT 3168 from Clariant is a mixture of 25% by weight of sodium carbonate, 25% by weight of citric acid in 50% by weight of polylactic acid as a carrier polymer

Fiber / nonwoven production (meltblown process): The fiber was produced in a spunbond (Meltblown) plant consisting of a 60 mm-25 D Reifenhäuser extruder and a nozzle plate with 1735 holes per meter and a hole diameter of 0.3 mm and a nozzle width of 60 cm.

Mixtures of 1% by weight, 5% by weight and 10% by weight of hydrocerol in the biodegradable polymer i-3 were prepared and prepared in the nonwowing (nonwoven) process at 10 to 50 g / m ² and wound up.

The gas bubbles (carbon dioxide released from hydrocerol CT3168) were at

Melt spinning the fibers in the melt until the melt exits the die. Then, gas bubbles at the surface were drawn by spinning the melt during spinning and became visible as thin spots of the fiber. The resulting thick and thin places increased the surface of the fiber and the softness increases. A rough surface was particularly pronounced with 5 -10 wt% Hydrocerol CT3168 additive. The result was nonwovens that were particularly suitable for cleaning purposes.

Propellant additives of more than 10% Hydrocerol CT3168 led to powdery particles, which formed a very rough surface, but could no longer be processed into nonwovens.

Table 1: Nonwovens produced by the meltblown process with a basis weight of 50 g / m ²

^* % By weight based on the extruded material (biodegradable polymer including blowing agent)

The softness of the webs determined in Table 1 was determined as follows: Webs having the same basis weight (50 g / m ² ) were cut into strips of 15 mm and clamped horizontally with a length of 200 mm. Gravity deformation of the web was measured by the maximum vertical deviation from the horizontal. The softer the fleece, the stronger the vertical (vertical) deviation.

From a concentration of 1 wt .-% blowing agent, gas bubbles were observed in the sieve package and with more than 2 to 10 wt .-% blowing agent foamed fibers (microscopic

Examination). Example 1 visually contained no foamed fiber, although equal to the web at the same basis weight was slightly softer than a non-woven fabric without propellant. Examples 2 and 3 contained foamed fibers even softer than Example 1 (greater vertical deviation). When more than 10% by weight of blowing agent was used, irregularities occurred in fiber production.

Fiber / nonwoven production (spunbond process):

In the Reicofil Spunbond process, two 90 mm extruders were used to make two-component fibers. The tool was equipped with a core / shell structure, which made it possible to produce fibers with an inner layer C1 (core layer) and an outer layer C2. The nozzle bar had a width of 1.2 m with 6827 nozzles per meter of length. The nozzles had an exit diameter of 0.6 mm. The throughput was limited to 237 kg / h, because at higher throughputs problems with the maximum back pressure of the two extruders and in the cooling shaft for bonding the fibers could occur. The

 Blowing agent was added to the extruder, the outer layer or the inner layer or both extruders.

The fibers were after the nozzle exit in the cooling shaft by suitable

Cross-section of the cooling air (25 -35 ° C) guided and subtracted. The average fiber diameter was between 1, 5 and 5 dtex (12.6 - 15.7 pm).

The fibers were deposited at a basis weight of 50 g / m ² in a 3 to 5 cm thick layer on a conveyor belt with elastomer surface. The layer was then compacted with heated calender rolls (85-100 ° C. at 50 bar contact pressure) to form a spunbonded nonwoven and wound up into rolls 1, 2-1, 4 m wide. Spun nonwovens of 20, 50 and 100 g / m ² were produced.

Nonwovens were produced at a melt temperature of 265 ° C, the maximum extruder pressure of 100 bar was not exceeded.

Special fleece qualities were produced with 3000 ppm behenic acid amide finish in the outer layer of the fibers. These spunbonded nonwovens had a hydrophobic surface that did not let water droplets through - but water vapor already. When the hydrophobized nonwoven fabric was combined with non-hydrophobicized nonwoven fabric on the skin side of the fabric, a breathable yet water repellent fabric was created.

Claims

claims 1. Foamed melt fibers of biodegradable polymers. 2. Melt fibers according to claim 1 with a fineness measured according to ISO 1 144: 2016-09 from 0.1 to 100 dtex. 3. Melt fibers according to claim 1 with a fineness measured according to ISO 1144: 2016-09 from 1 to 50 dtex. 4. Staple fibers of biodegradable polymers having a fineness measured in accordance with ISO 1 144: 2016-09 of 1 to 50 dtex. 5. Endless fibers of biodegradable polymers with a fineness measured in accordance with ISO 1 144: 2016-09 of 100 to 3000 dtex. 6. Monofilaments of biodegradable polymers with a fineness measured according to ISO  1 144: 2016-09 from 0.5 to 5 mm. The fibers of claims 1 to 6, wherein the biodegradable polymer is a polyester comprising: A1) 40 to 100 mol%, based on the components A1) to A2), of an aliphatic C 4 -C 18 dicarboxylic acid or mixtures thereof, A2) 0 to 60 mol%, based on the components A1) to A2), of an aromatic dicarboxylic acid or mixtures thereof, B) 98.5 to 100 mol%, based on components A1) to A2), of a diol component of a C2 to C12 alkanediol or mixtures thereof; and C) 0 to 1, 5 wt .-%, based on the components A1) to A2) and B), a compound or more compounds selected from the group consisting of: C1) a compound having at least three groups capable of ester formation, C2) a compound having at least two isocyanate groups, C3) a compound having at least two epoxide groups. 8. Fibers according to one of claims 1 to 7, containing water repellents, dyes, antistatic agents and / or lubricants. 9. Nonwoven fabric made of fibers according to any one of claims 2, 3, 7 or 8, preferably by means of the meltblown or spunbond process. 10. Nonwoven fabric made of staple fibers according to claim 4, 7 or 8, preferably by means of the airlaid process or the wet-laid process. 1 1. Nonwoven fabric according to claim 9 or 10, additionally containing natural fibers such as cellulose or wool fibers. 12. textile, geotextile or agrotextile, made of continuous fibers according to claim 5, 7 or 8. 13. film tapes, packaging or fishing nets made of monofilaments according to one of claims 6 to 8. 14. A process for producing fibers according to any one of claims 1 to 8 by melt spinning, wherein the biodegradable polymer is melted in an extruder and 1 to 10 wt .-% of a chemical blowing agent, based on the extruded material at the beginning, im Is added to the extruder or at the end of the extruder and the resulting extruded material is forced through a spinneret.