EP1994212A1

EP1994212A1 - Nonwoven based on thermoplastic polyurethane

Info

Publication number: EP1994212A1
Application number: EP07712353A
Authority: EP
Inventors: Rolf Steinberger; Hauke Malz
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2006-03-06
Filing date: 2007-02-28
Publication date: 2008-11-26
Also published as: WO2007101808A1; CN101400838A; US20090011209A1

Abstract

Fibrous nonwoven web based on thermoplastic polyurethane, characterized in that the thermoplastic polyurethane has a crystallization temperature between 130°C and 220°C and is based on aliphatic isocyanates.

Description

Nonwoven fabric based on thermoplastic polyurethane

description

The invention relates to nonwoven fabric based on thermoplastic polyurethane, wherein the thermoplastic polyurethane has a crystallization temperature between 130 ° C and 220 ° C, preferably between 140 ° C and 200 ° C, more preferably between 150 ° C and 200 ° C and aliphatic Isocyanates based. In addition, the invention relates to non-woven based on thermoplastic polyurethane, wherein the thermoplastic polyurethane is obtainable by reacting (a) isocyanates with (b1) polyester diols having a melting point greater than 150 ° C, (b2) polyether diols and / or polyester diols each with a melting point less than 150 ° C and a molecular weight of 501 to 8000 g / mol and (c) diols having a molecular weight of 62 g / mol to 500 g / mol and wherein the molar ratio of the diols (c) having a molecular weight of 62 g / mol to 500 g / mol to component (b2) is preferably between 0.1 to 0.01. Furthermore, the invention relates to non-woven based on thermoplastic polyurethane, wherein the thermoplastic polyurethane is obtainable, in which

(i) reacting a thermoplastic polyester with a diol (c) and then

(Ii) the reaction product of (i) containing (b1) polyester diol having a melting point greater than 15O ⁰ C and optionally (c) diol together with (b2) polyether diols and / or polyester diols each having a melting point of less than 150 ° C and a molecular weight of 501 to 8000 g / mol and optionally further (c) diols having a molecular weight of 62 to 500 g / mol with (a) isocyanate, if appropriate in the presence of (d) catalysts and / or (e) auxiliaries.

In addition, the present invention relates to methods for producing such nonwoven fabrics.

A nonwoven or nonwoven generally refers to a textile structure which is produced by bonding or bonding or bonding and joining fibers by mechanical, chemical, thermal or solvent-technical methods or any combination of these methods, ie a non-woven structure. Polymer nonwovens are mainly produced in continuous processes. Here are especially the meltblown and the spunbond process called. In these processes, the polymer is melted on an extruder and conveyed by melt pumping to a spinning beam. Modern nonwoven processes today operate at high throughputs with spinning beams of up to 5 m width and can continuously produce the nonwovens. In the production of nonwoven by the melt-blown and spunbond process mainly polypropylene and polyester are used. However, the nonwovens made from these plastics are not elastic. For this reason, attempts have been made in recent years to process thermoplastic polyurethanes (also referred to below as TPUs) to nonwovens. Thermoplastic polyurethanes are polyurethanes which, when repeatedly heated and cooled in the temperature range typical of the material for processing and use, remain thermoplastic. Thermoplastic in this case is understood to be the property of the polyurethane, in a temperature range typical for the polyurethane between 150 ° C and 300 ° C to soften repeatedly in the heat and to harden on cooling and repeated in the softened state by flowing as a molded part, extrudate or Forming part to semis or objects formable. Nonwovens based on TPU are characterized by their very high elasticity, good resilience, low residual elongation and tensile strength.

By aromatic thermoplastic polyurethanes is meant those TPUs based on an aromatic isocyanate, for example 4,4 'MDI. By aliphatic TPU is meant those TPU based on aliphatic isocyanates, for example 1, 6 HDI.

Nonwovens go into many different applications, such as sanitation, e.g. Diapers and disposable washcloths, but also in technical fields, e.g. Filters, in medical applications and in civil engineering applications such as geotextiles and roof underlays.

Especially in the hygiene sector, in textiles and in the medical sector, the light fastness of nonwovens is a very important criterion, since the end user equates a yellowed fleece with "unhygienic" or "low quality", while a white fleece is associated with "hygienic and high quality". Lightfastness refers to the resistance of fabrics of all kinds (textiles, prints, plastics, ceramics, etc.) and in all processing conditions against color changes by direct action of daylight without direct effect of the weather.

Due to their different chemical structure, plastics generally contribute to different levels of stability against UV light and thermal damage or against damage caused by environmental influences. Nevertheless, it would be desirable to make the scope of all plastics as broad as possible, i. the stability of the plastic against environmental damage e.g. through heat, sunlight or UV light.

It is generally the art to protect plastics with stabilizers. For example, plastics can be made by a mixture of an antioxidant (AO) and A Hindererd Amine Light Stabilizer (HALS) or by a mixture of a UV absorber and a phenolic antioxidant or by mixing a phenolic antioxidant, a HALS and a UV absorber against UV damage. Due to the significant improvements in the properties of plastics, which were achieved by the addition of stabilizing additives, a vast number of different stabilizers and stabilizer combinations is now commercially available. Examples of such compounds are given in Plastics Additive Handbook, 5th Edition, H. Zweifel, ed., Hanser Publishers, Munich, 2001 ([1]), p.98-S136.

Examples of good stabilization of TPU by combination of different stabilizers are given in WO03031506.

However, the lightfastness of a very well stabilized aromatic TPU is often not considered sufficient. Therefore, development of alipahtic TPU has been promoted in recent years. Due to their chemical structure, aliphatic TPUs do not form chromophores and therefore do not discolour. Especially in the automotive industry aliphatic TPU therefore find more and more applications.

However, surprisingly, aliphatic TPUs can only be inadequately processed into nonwovens with high quality, since during processing very high temperatures of up to 240 ° C. and hot air temperatures of up to 270 ° C. have to be used. However, this causes the TPU filament does not crystallize on the way from the nozzle to the collector belt. The still deformable fibers stick together and the fleece receives an unpleasant foil-like handle, which is perceived as non-textile. In addition, the mechanical property of such a nonwoven is insufficient.

The object of the invention was therefore to produce a lightfast TPU nonwoven, which has a pleasant textile feel, is easy to process and has good mechanical properties, in particular a good elongation at break.

The tasks could be solved by the nonwovens presented above.

The nonwovens according to the invention are characterized in that the thermoplastic polyurethanes used have a rapid solidification behavior. This means that rapid cooling of the TPU takes place during cooling of the melt thread even at high temperatures, which leads to early stabilization of the fiber. Thus, the product on conventional systems to obtain a nonwoven fabric with textile handle processable. Textile grip in this context means that the feel of the nonwoven corresponds to that of a woven or knitted textile. The opposite of a textile handle, for example, would be a foil-like handle, ie the nonwoven feels like a plastic film. The particularly preferred thermoplastic polyurethanes show optically clear, single-phase melts which rapidly solidify and form weakly opaque to white-opaque shaped bodies as a result of the partially crystalline polyester hard phase.

The determination of the crystallization temperature of the thermoplastic polyurethanes of the invention is generally known and is particularly preferably carried out by means of DSC (Dynamic Scanning Calorimetry) with a Perkin Elmer DSC 7, wherein the thermoplastic polyurethane is heated according to the following temperature program:

1. Keep at 25 ° C for 0.1 min

2. Heat up from 25 ° C to 100 ° C at 40 K / min

3. Hold for 10 min at 100 ° C

4. Cool from 100 ° C to -80 ° C with a cooling rate of 20 K / min. Keep at -80 ° C for 2 min

6. Heating from -80 ° C to 230 ° C with 20 K / min heating rate

7. Hold at 230 ° C for 1 min

8. cooling from 230 ⁰ C to -80 ⁰ C and 20 K / min,

and the crystallization temperature is the temperature at which the exothermic heat flow of the sample has a maximum during cooling.

By the term "nonwoven" is meant a nonwoven web and nonwoven web constructed of randomly oriented or randomly bonded fibers solidified by friction and / or cohesion and / or adhesion, and corresponding nonwoven webs are also known as nonwoven webs.

Preferably, paper or products which have been woven, knitted, tufted, stitched together with binding yarns or filaments or felted by wet-rolling are not treated as non-woven fabrics in the context of this application.

In a preferred embodiment, a material is considered to be "nonwoven" within the meaning of this application if more than 50%, in particular 60 to 90%, of the mass of its fibrous constituent of fibers having a length to diameter ratio greater than 300, in particular more than 500.

Preference is given to nonwovens in which the thermoplastic polyurethane has a hardness between 50 Shore A and 80 Shore D, more preferably between 60 Shore A and 60 Shore D, in particular between 60 Shore A and 95 Shore A. In a preferred embodiment, the individual fibers of the nonwoven have a diameter of 50 .mu.m to 0.1 .mu.m, preferably from 10 .mu.m to 0.5 .mu.m, in particular from 7 .mu.m to 0.5 .mu.m.

In a preferred embodiment, the nonwoven fabrics have a thickness of 0.01 to 5 millimeters (mm), more preferably from 0.1 to 2 mm, particularly preferably from 0.15 to 1, 5 mm, measured according to ISO 9073-2.

In a preferred embodiment, the nonwoven fabrics have a basis weight of from 5 to 500 g / m ² , more preferably from 10 to 250 g / m ² , particularly preferably from 15 to 150 g / m ² , measured to ISO 9073-1.

The nonwoven fabric may additionally be mechanically consolidated. The mechanical consolidation may be a one-sided or bilateral mechanical consolidation, preferably a two-sided mechanical consolidation.

In addition to the mechanical consolidation described above, the nonwoven fabric may additionally be thermally bonded. Thermal consolidation can be achieved, for example, by hot air treatment or by calendering the nonwoven fabric. The calendering of the nonwoven fabric is preferred.

In a preferred embodiment, the nonwoven fabric used has an elongation at break in the production direction between 20% and 2000%, preferably between 100% and 1000%, in particular between 200% and 1000%, measured according to DIN EN 12127.

The nonwoven fabric used is based on, i. is made with thermoplastic polyurethane. By this is meant that the nonwoven fabric used contains thermoplastic polyurethane, preferably as an essential constituent. In a preferred embodiment, the nonwoven fabric used contains thermoplastic polyurethane in an amount of 60% by weight to 100% by weight, particularly preferably more than 80% by weight, in particular more than 97% by weight, based on the total weight of the nonwoven fabric.

In addition to thermoplastic polyurethane, the nonwoven fabric used may contain other polymers or auxiliaries, such as, for example, polypropylene, polyethylene and / or polystyrene and / or copolymers of polystyrene, such as styrene-acrylonitrile copolymers.

Thermoplastic polyurethanes, also referred to in this document as TPU, and processes for their preparation are well known. In general, TPUs are prepared by reacting (a) isocyanates with (b) isocyanate-reactive compounds, usually having a molecular weight (M _w ) of 500 to 10,000, preferably from 500 to 5000, more preferably from 800 to 3000, and (c) chain extenders having a molecular weight of from 50 to 499, optionally in the presence of (d) catalysts and / or (e) conventional additives.

In the following, by way of example, the starting components and processes for the preparation of the preferred polyurethanes are shown. The components (a), (b), (c) and optionally (d) and / or (e) usually used in the preparation of the polyurethanes are described below by way of example:

As aliphatic isocyanates (a) it is possible to use generally known isocyanates, preferably diisocyanates, for example tri-, tetra-, penta-, hexa-, hepta- and / or octamethylene diisocyanate, 2-methylpentamethylene diisocyanate 1, 5, 2-ethyl-butylene-diisocyanate-1,4-pentamethylene-diisocyanate-1,5-butylene-diisocyanate-1,4,4-isocyanato-3,3,5-trimethyl-5-isocyanato-methyl-cyclohexane (isophorone). diisocyanate, IPDI), 1, 4- and / or 1, 3-bis (isocyanatomethyl) cyclohexane (HXDI), 1, 4-cyclohexane diisocyanate, 1-methyl-2,4- and / or -2,6-cyclohexane diisocyanate and / or 4,4'-, 2,4'- and 2,2'-dicyclohexylmethane diisocyanate, more preferably 1-isocyanato-3,3,5-trimethyl-5-isocyanato-methyl-cyclohexane ( Isophorone diisocyanate, IPDI) and / or hexamethylene diisocyanate (HDI), in particular hexamethylene diisocyanate.

As isocyanate-reactive compounds (b) it is possible to use the generally known isocyanate-reactive compounds, for example polyesterols, polyetherols and / or polycarbonatediols, which are usually also grouped under the term "polyols", with molecular weights of between 500 and 8000, preferably between 600 and 6000, in particular 800 to less than 3000, and preferably an average functionality over isocyanates of 1.8 to 2.3, preferably 1.9 to 2.2, in particular 2.

Furthermore, it is possible to use as polyetherols so-called low-unsaturated polyetherols. In the context of this invention, low-unsaturated polyols are understood as meaning, in particular, polyether alcohols having a content of unsaturated compounds of less than 0.02 meq / g, preferably less than 0.01 meq / g.

Such polyether alcohols are usually prepared by addition of alkylene oxides, in particular ethylene oxide, propylene oxide and mixtures thereof, to the diols or triols described above in the presence of highly active catalysts. Such highly active catalysts are, for example, cesium hydroxide and multimetal cyanide catalysts, also referred to as DMC catalysts. A frequently used DMC catalyst is zinc hexacyanocobaltate. The DMC catalyst can be left in the polyether alcohol after the reaction, usually it is removed, for example by sedimentation or filtration. Furthermore, polybutadiene diols having a molecular weight of 500-10,000 g / mol, preferably 1,000-5,000 g / mol, in particular 2,000-3,000 g / mol, can be used. TPUs made using these polyols can be radiation crosslinked after thermoplastic processing. This leads eg to a better burning behavior.

Instead of a polyol, it is also possible to use mixtures of different polyols.

As chain extenders (c) it is possible to use generally known aliphatic, araliphatic, aromatic and / or cycloaliphatic compounds having a molecular weight of 50 to 499, preferably 2-functional compounds, for example diamines and / or alkanediols having 2 to 10 carbon atoms in the alkylene radical, especially 1, 3-propanediol, butanediol-1, 4, hexanediol-1, 6 and / or di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona- and or Dekaalkylenglykole having 3 to 8 carbon atoms, preferably corresponding oligo- and / or polypropylene glycols, wherein mixtures of the chain extenders can be used.

Most preferably, components a) to c) are difunctional compounds, i. Diisocyanates (a), difunctional polyols, preferably polyetherols (b) and difunctional chain extenders, preferably diols.

Suitable catalysts (d) which in particular accelerate the reaction between the NCO groups of the diisocyanates (a) and the hydroxyl groups of the constituent components (b) and (c) are the tertiary amines known and customary in the prior art, e.g. Triethylamine, dimethylcyclohexylamine, N-methylmorpholine, N, N'-dimethylpiperazine, 2- (dimethylaminoethoxy) ethanol, diazabicyclo- (2,2,2) octane and the like, and especially organic metal compounds such as titanic acid esters, iron compounds e.g. Iron (Ml) acetylacetonate, tin compounds, e.g. Tin diacetate, tin dioctoate, tin dilaurate or the tin dialkyl salts of aliphatic carboxylic acids such as dibutyltin diacetate, dibutyltin dilaurate or the like. The catalysts are usually used in amounts of from 0.0001 to 0.1 parts by weight per 100 parts by weight of polyhydroxy compound (b).

In addition to catalysts (d), the structural components (a) to (c) can also conventional

Additives and / or additives (s) are added. Examples which may be mentioned are blowing agents, surface-active substances, nucleating agents, lubricants and mold release agents, dyes and pigments, antioxidants, for example against hydrolysis, light, heat or discoloration, inorganic and / or organic fillers, flame retardants, reinforcing agents and plasticizers, metal deactivators. In a preferred embodiment, component (e) also includes hydrolysis protectants such as, for example, polymeric and low molecular weight carbodiimides. Particularly preferred holds the thermoplastic polyurethane in the materials according to the invention meiamincyanurat, which acts as a flame retardant. Melamine cyanurate is preferably used in an amount of between 0.1 and 60% by weight, more preferably between 5 and 40% by weight, in particular between 15 and 25% by weight, in each case based on the total weight of the TPU. The thermoplastic polyurethane preferably contains triazole and / or triazole derivative and antioxidants in an amount of from 0.1 to 5% by weight, based on the total weight of the thermoplastic polyurethane. As antioxidants are generally suitable substances which inhibit or prevent unwanted oxidative processes in the plastic to be protected. In general, antioxidants are commercially available. Examples of antioxidants are hindered phenols, aromatic amines, thiosynergists, trivalent phosphorus organophosphorus compounds, and hindered amine light stabilizers. Examples of hindered phenols can be found in Plastics Additive Handbook, 5 ^th edition, H. Zweifel, ed, Hanser Publishers, Munich, 2001 ([1]), pp. 98-107 and pp. 16-121. Examples of aromatic amines can be found in [1] pp. 107-108. Examples of thiosynergists are given in [1], p.104-105 and p.1 12-1 13. Examples of phosphites can be found in [1], p.109-1.12. Examples of hindered amine light stabilizers are given in [1], p.123-136. Phenolic antioxidants are preferred for use. In a preferred embodiment, the antioxidants, in particular the phenolic antioxidants, have a molecular weight of greater than 350 g / mol, particularly preferably greater

700 g / mol and a maximum molecular weight <10000 g / mol, preferably <3000 g / mol. Furthermore, they preferably have a melting point of less than 180 ° C. Furthermore, antioxidants are preferably used which are amorphous or liquid.

In addition to the abovementioned components a), b) and c) and optionally d) and e) it is also possible to use chain regulators, usually having a molecular weight of from 31 to 3000. Such chain regulators are compounds which have only one isocyanate-reactive functional group, such as. As monofunctional alcohols, monofunctional amines and / or monofunctional polyols. By means of such chain regulators, a flow behavior, in particular with TPUs, can be adjusted in a targeted manner. Chain regulators can generally be used in an amount of 0 to 5, preferably 0.1 to 1, parts by weight, based on 100 parts by weight of component b), and fall by definition under component (c).

To adjust the hardness of the TPUs, the structural components (b) and (c) can be varied in relatively wide molar ratios. Proven molar ratios of component (b) to total used chain extenders (c) of 10: 1 to 1:10, in particular from 1: 1 to 1: 4, the hardness of the TPU increases with increasing content of (c).

The thermoplastic polyurethane preferably has a viscosity number (measured in phenol / chlorobenzene) of at least 100 cm ³ / g, preferably between 100 cm ³ / g and 1000 cm ³ / g, more preferably between 200 cm ³ / g and 600 cm ³ / g, in particular between 250 cm ³ / g and 500 cm ³ / g.

TPUs which are described in WO 03/014179, insofar as these are based on aliphatic losocyanates, are preferably used for the production of the nonwoven fabrics according to the invention. These particularly preferred TPUs, which are described in detail below, have the advantage that the thermoplastic polyurethanes used have a rapid setting behavior, i. have a very good crystallization even at high melt temperatures. This allows the processing of thermoplastic polyurethanes on conventional systems to obtain a nonwoven fabric with a textile handle. Textile grip in this context means that the feel of the nonwoven corresponds to that of a woven or knitted textile. For example, the opposite of a textile handle would be a foil-like handle, i. The nonwoven feels like a plastic film.

These particularly preferred TPUs are preferably obtainable by reacting (a) isocyanates with (b1) polyesterdiols having a melting point greater than 15O ⁰ C, lyetherdiolen (b2) butt and / or polyesterdiols, each having a melting point of less than 15O ⁰ C and a molecular weight of 501 to 8000 g / mol and optionally (c) diols having a molecular weight of 62 g / mol to 500 g / mol. Particular preference is given to thermoplastic polyurethanes in which the molar ratio of the diols (c) having a molecular weight of from 62 g / mol to 500 g / mol to the component (b2) is less than 0.2, particularly preferably from 0.1 to 0.01, is. Particular preference is given to thermoplastic polyurethanes in which the polyesterdiols (b1), which preferably have a molecular weight of from 1000 g / mol to 5000 g / mol, have the following structural unit (I):

-0-ROTCRCOR ¹ O-

O O

with the following meanings for R1, R2, R3 and X:

R 1: carbon skeleton having 2 to 15 carbon atoms, preferably an alkylene group having 2 to 15 carbon atoms and / or a bivalent aromatic radical having 6 to 15 carbon atoms, particularly preferably having 6 to 12 carbon atoms

R 2: optionally branched-chain alkylene group having 2 to 8 carbon atoms, preferably 2 to 6, particularly preferably 2 to 4 carbon atoms, in particular -CH ₂ -CH ₂ - and / or -CH ₂ -CH ₂ -CH ₂ -CH ₂ -, R 3: optionally branched-chain alkylene group having 2 to 8 carbon atoms, preferably 2 to 6, particularly preferably 2 to 4 carbon atoms, in particular -CH ₂ -CH ₂ - and / or -CH ₂ -CH ₂ -CH ₂ -CH ₂ -,

X: an integer from the range 5 to 30. In the preferred embodiment, the preferred melting point and / or the preferred molecular weight mentioned above relate to the structural unit (I) shown.

The term "melting point" in this document means the maximum of the melting peak of a heating curve which was measured using a commercially available DSC apparatus (for example DSC 7 / Perkin-Elmer Co.).

The molecular weights given in this document represent the number average molecular weights in [g / mol].

These particularly preferred thermoplastic polyurethanes can preferably be prepared by reacting in a first step (i) a, preferably high molecular weight, preferably semicrystalline, thermoplastic polyester with a diol (c) and then in a second reaction (ii) the reaction product ( i) containing (b1) polyester diol having a melting point greater than 15O ⁰ C and optionally (c) diol together with (b2) polyether diols and / or polyester diols each having a melting point of less than 15O ⁰ C and a molecular weight of 501 to 8000 g / mol and optionally further (c) diols having a molecular weight of 62 to 500 g / mol with (a) isocyanate, if appropriate in the presence of (d) catalysts and / or (e) auxiliaries.

In the reaction (ii), the molar ratio of the diols (c) having a molecular weight of from 62 g / mol to 500 g / mol to the component (b2) is preferably less than 0.2, preferably from 0.1 to 0.01.

While the hard phases are provided by the step (i) used by the polyester used in step (i) for the final product, the use of the component (b2) in step (ii), the structure of the soft phases. The preferred technical teaching is that polyesters having a pronounced, well crystallizing hard phase structure are preferably melted in a reaction extruder and first degraded with a low molecular weight diol to give shorter polyesters having free hydroxyl end groups. In this case, the original high crystallization tendency of the polyester is retained and can then be used to obtain TPU having the advantageous properties in rapid implementation, as there are high tensile strength values, low abrasion values and high heat resistance and low compression set due to the high and narrow melting range. Thus, according to the preferred method, preferably high molecular weight, partially crystalline stalline, thermoplastic polyesters with low molecular weight diols (c) degraded under suitable conditions in a short reaction time to rapidly crystallizing poly-ester diols (b1), which in turn are then integrated with other polyester diols and / or polyether and diisocyanates in high molecular weight polymer chains.

In this case, the thermoplastic polyester used, ie before the reaction (i) with the diol (c), preferably has a molecular weight of 15000 g / mol to 40,000 g / mol and preferably a melting point of greater than 16O ⁰ C, particularly preferably of 170 ° C. to 260 ⁰ C on.

As the starting product, i. as polyester, in the step (i) preferably in the molten state, particularly preferably at a temperature of 230 ° C to 280 ° C, preferably for a period of 0.1 min to 4 min, particularly preferably 0.3 min to 1 min with the diol (s) (c) is reacted, it is possible to use generally known, preferably high molecular weight, preferably partially crystalline, thermoplastic polyesters, for example in granulated form. Suitable polyesters are based, for example, on aliphatic, cycloaliphatic, araliphatic and / or aromatic dicarboxylic acids, for example lactic acid and / or terephthalic acid, and aliphatic, cycloaliphatic, araliphatic and / or aromatic dialcohols, for example ethanediol-1,2-butanediol-1,4 and / or hexanediol-1, 6.

Particularly preferred polyesters used are: poly-L-lactic acid and / or polyalkylene terephthalate, for example polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, in particular polybutylene terephthalate.

The preparation of these esters from the stated starting materials is well known to the skilled worker and has been described many times. Suitable polyesters are also commercially available

The thermoplastic polyester is preferably melted at a temperature of 180 ° C to 270 ° C. The reaction (i) with the diol (c) is preferably carried out at a temperature of 230 ° C to 280 ° C, preferably 240 ° C to 280 ° C.

As diol (c) it is possible in step (i) for reaction with the thermoplastic polyester and, if appropriate, in step (ii), to use generally known diols having a molecular weight of from 62 to 500 g / mol, for example those mentioned below, eg Ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, heptanediol, octanediol, preferably butane-1,4-diol and / or ethane-1,2-diol.

The weight ratio of the thermoplastic polyester to the diol (c) in the step (i) is usually 100: 1, 0 to 100: 10, preferably 100: 1, 5 to 100: 8.0. The reaction of the thermoplastic polyester with the diol (c) in the reaction step (i) is preferably carried out in the presence of conventional catalysts, for example those which will be described later. Preference is given to using catalysts based on metals for this reaction. Preferably, the reaction in step (i) is carried out in the presence of from 0.1 to 2% by weight of catalysts, based on the weight of diol (c). The reaction in the presence of such catalysts is advantageous in order to be able to carry out the reaction in the available short residence time in the reactor, for example a reaction extruder.

Examples of suitable catalysts for this reaction step (i) are: tetrabutyl orthotitanate and / or tin (II) dioctoate, preferably tin dioctoate.

The polyesterdiol (b1) as the reaction product from (i) preferably has a molecular weight of from 1000 g / mol to 5000 g / mol. The melting point of the polyester diol as the reaction product of (i) is preferably 150 ° C to 260 ° C, especially 165 to 245 ° C, i. in that the reaction product of the thermoplastic polyester with the diol (c) in step (i) contains compounds having the said melting point which are used in the subsequent step (ii).

By reacting the thermoplastic polyester with the diol (c) in the step (i), the polymer chain of the polyester is cleaved by the diol (c) by transesterification. The reaction product of the TPU therefore has free hydroxyl end groups and is preferably further processed in the further step (ii) to the actual product, the TPU.

The reaction of the reaction product from step (i) in step (ii) is preferably carried out by adding a) isocyanate (a) and (b2) polyether diols and / or polyester diols each having a melting point below 150 ° C. and a molecular weight. weight of 501 to 8000 g / mol and optionally further diols (c) having a molecular weight of 62 to 500, (d) catalysts and / or (e) auxiliaries to the reaction product of (i). The reaction of the reaction product with the isocyanate takes place via the hydroxyl end groups formed in step (i). The reaction in step (ii) is preferably carried out at a temperature of from 190 to 250 ° C., preferably for a period of from 0.5 to 5 minutes, more preferably from 0.5 to 2 minutes, preferably in a reaction extruder, more preferably in the same Reaction extruder, in which also the step (i) was carried out. For example, the reaction of step (i) can take place in the first housings of a conventional reaction extruder and later, ie later housings, after the addition of components (a) and (b2), the corresponding reaction of step (ii) can be carried out. For example, the first 30 to 50% of the length of the reaction extruder may be used for step (i) and the remaining 50 to 70% used for step (ii). The reaction in step (ii) is preferably carried out with an excess of the isocyanate groups to the isocyanate-reactive groups. In the reaction (ii), the ratio of the isocyanate groups to the hydroxyl groups is preferably 1: 1 to 1.2: 1, more preferably 1.2: 1 to 1.2: 1.

The reactions (i) and (ii) are preferably carried out in a generally known reaction extruder. Such reaction extruders are described by way of example in the company publications by Werner & Pfleiderer or in DE-A 2 302 564.

Preferably, the preferred process is carried out by introducing into the first housing of a reaction extruder at least one thermoplastic polyester, e.g. Polybutylene terephthalate, dosed and melts at temperatures preferably between 180 ° C to 270 ° C, preferably 240 ° C to 270 ° C, in a subsequent housing a diol (c), e.g. Butanediol, and preferably a transesterification catalyst, at temperatures between 240 ° C to 280 ° C, the polyester by the diol (c) to polyester oligomers with hydroxyl end groups and molecular weights between 1000 to 5000 g / mol degrades, in a subsequent housing isocyanate (a ) and (b2) compounds which are reactive toward isocyanates and have a molecular weight of 501 to 8000 g / mol and optionally (c) diols having a molecular weight of 62 to 500, (d) catalysts and / or (e) auxiliaries and then added at temperatures of 190 to 250 ° C performs the structure of the preferred thermoplastic polyurethanes.

Preferably, in step (ii), with the exception of (c) diols having a molecular weight of from 62 to 500, contained in the reaction product of (i), no (c) diols having a molecular weight of from 62 to 500 are fed.

The reaction extruder preferably has neutral and / or backward-promoting kneading blocks and recycling elements in the region in which the thermoplastic polyester is melted, and in the region in which the thermoplastic polyester is reacted with the diol, preferably screw mixing elements, toothed disks and / or tooth mixing elements Combination with return conveyor elements.

After the reaction extruder, the clear melt is usually fed by means of a gear pump underwater granulation and granulated.

The proportion of the thermoplastic polyester in the end product, ie the thermoplastic polyurethane, is preferably 5 to 75 wt .-%. The preferred thermoplastic polyurethanes particularly preferably comprise products of the reaction of a mixture comprising 10 to 70% by weight of the reaction product of (i), 10 to 80% by weight (b2) and 10 to 20% by weight (a), the weight data being based on the total weight of the mixture containing (a), (b2), (d), (e) and the reaction product of (i) are obtained.

The preferred thermoplastic polyurethanes preferably have the following structural unit (II):

with the following meanings for R1, R2, R3 and X:

R1: carbon skeleton having 2 to 15 carbon atoms, preferably an alkylene group having 2 to 15 carbon atoms and / or an aromatic radical having 6 to 15 carbon atoms,

R 2: optionally branched-chain alkylene group having 2 to 8 carbon atoms, preferably 2 to 6, more preferably 2 to 4 carbon atoms, in particular

-CH 2 -CH 2 - and / or -CH 2 -CH 2 -CH 2 -CH 2 -,

R3: radical which results from the use of polyether diols and / or polyester diols each having molecular weights between 501 g / mol and 8000 g / mol as (b2) or by the use of alkanediols having 2 to 12 carbon atoms for the reaction with diisocyanates,

X: an integer from the range 5 to 30,

n, m: an integer from the range 5 to 20.

The radical R ¹ is defined by the isocyanate used, the radical R ² by the reaction product of the thermoplastic polyester with the diol (c) in (i) and the radical R ³ by the starting components (b2) and optionally (c) in the preparation the TPU.

The thermoplastic polyurethane-containing nonwoven fabrics may usually be prepared by the prior art "meltblown process" or "spunbond process" from the above-described thermoplastic polyurethane. "Meltblown process" and "spunbond process" are known in the art.

The resulting nonwoven fabrics generally differ in their mechanical properties and consistency. So are after the spunbond process Nonwovens produced are particularly stable in both the horizontal and vertical directions, but have an open-pore structure.

Nonwovens produced by the meltblown process have a particularly dense network of fibers and thus provide a very good barrier to liquids.

Nonwovens produced by the meltblown process are preferably used.

For the production of a nonwoven fabric from thermoplastic polyurethane (TPU nonwoven) by the meltblown process, a commercial plant for the production of meltblown nonwovens can be used. Such systems are sold, for example, by Reifenhäuser, Germany.

In the meltblown process, the TPU is usually melted in an extruder and routed to a spinning beam by means of customary auxiliaries, such as melt pumps and filters. Here, the polymer generally flows through nozzles and is drawn at the nozzle exit by a stream of air to a thread. The drawn threads are usually deposited on a drum or a belt and transported on.

In a preferred embodiment, the extruder used is a single-screw extruder with a compression ratio of 1: 2-1: 3.5, more preferably 1: 2-1: 3.

In addition, a three-zone screw with an L / D ratio (length to diameter) of 25-30 is preferably used. Preferably, the three zones are the same length. Preferably, the three-zone screw has a continuously constant pitch of 0.8-1, 2 D, particularly preferably 0.95-1, 05 D. The clearance between the screw and cylinder is> 0.1 mm, preferably 0.1-0.2 mm.

If a barrier screw is used as the extruder screw, it is preferable to use an overflow gap> 1.2 mm.

If the screw has mixing parts, these mixing parts are preferably not shearing parts.

The nonwoven installation is usually dimensioned so that the residence time of the TPU is as short as possible, i. <15 min, preferably <10 min, particularly preferably <5 min.

The TPU according to the invention is usually processed at temperatures between 180.degree. C. and 250.degree. C., preferably between 200.degree. C. and 230.degree. The nonwovens according to the invention are used, for example, as seals in the technical sector, hygiene products, filters, medical products, laminates and textiles, for example as plasters, wound dressings and bandages in the medical sector, as elastic elements in diapers and other hygiene articles, as elastic cuffs in clothing , as an inliner for clothing, as a carrier for films, for example in the production of water vapor permeable membranes, as a laminate for leather, as slip protection for tablecloths, carpets, as slip protection for socks, as a decorative application in the automotive interior, in textiles and sports shoes, curtains, furniture and more.

To extend the application, the nonwoven fabrics of the present invention may be coated with other materials, e.g. Nonwovens, textiles, leather, paper, to be laminated.

The invention thus also relates to seals in the technical sector, hygiene products, filters, medical products, laminates and textiles, particularly preferably hygiene products and / or medical products containing the nonwovens according to the invention.

The invention will be illustrated by the following examples.

Examples

With Elastollan® LP 9300 (aliphatic TPU from Elastogran GmbH) and Elastollan® LP 9277 (aliphatic TPU from Elastogran GmbH) nonwovens were produced in Examples 1.1 and 1.2. The two TPUs had the following crystallization temperatures

Elastollan® LP 9300: 93.7 ° C Elastollan® LP 9277: 166 ° C

Elastollan® LP 9277 is a hard phase-modified aliphatic polyester poly- urethane based on butanediol, HDI, polyester diol (2-methylpropanediol, butanediol adipic acid copolyester) with a molecular weight of 3000 g / mol and polybutylene terephthalate segment as hard phase.

Elastollan® LP 9300 is an aliphatic TPU based on butanediol adipate polyester diol (molecular weight 2400 g / mol), butanediol as chain extender and HDI.

To determine the crystallization temperatures were injection molded test plates of the dimensions 12 cm ^* 8 cm ^* 0.2 cm samples taken and analyzed by a DSC apparatus (Perkin Elmer 7) according to the following test program:

1. Keep at 25 ° C for 0.1 min

2. Heat up from 25 ° C to 100 ° C at 40 K / min 3. Hold for 10 min at 100 ° C

4. Cool from 100 ° C to -80 ° C with a cooling rate of 20 K / min

5. Hold for 2 min at -80 ° C

6. Heating from -80 ° C to 230 ° C with 20 K / min heating rate 7. Hold at 230 ° C for 1 min

8. Cooling from 230 ⁰ C to -80 ⁰ C at 20 K / min

The crystallization temperature used here is the maximum of the heat emission of the sample in the cooling cycle.

Example 1.1

Elastollan® LP 9300 was processed on a commercial meltblown line with 1 m spinneret (25-hole / inch) and 100 mm extruder to a meltbown nonwoven with a basis weight of 50 g / m ² . The temperature of the spinning pump was 240 ⁰ C, the temperature of the nozzle was set to 240 ⁰ C. The temperature of the hot air was 225 ° C. The nozzle diameter was 0.4 mm. The TPU was difficult to process, the nonwoven was inhomogeneous and had a foil-like feel.

Example 1.2

An Elastollan® LP 9277 was processed on the same line. The temperature of the spinning pump was 240 ⁰ C, the die temperature was 240 ⁰ C, and the temperature of hot air was 225 ⁰ C. The basis weight of the web was also adjusted to 50 g / m ^2. In addition, a nonwoven was produced with a basis weight of 100 g / m ² . The TPU worked well. The resulting nonwoven was homogeneous and had a textile, pleasant feel.

The two nonwoven samples 1.1 and 1.2 were then analyzed according to DIN EN 12127.

(MD): values of the fleece in the direction of production

(CD): values of the fleece measured at right angles to the production direction

The following ultimate elongation values are determined 48 hours after processing

Elastollan® LP 9300: elongation at break (MD): 160%

Elongation at break (CD): 190%

Elastollan® LP 9277: Elongation at break (MD): 240%

Elongation at break (CD): 240% The elongation at break measurements showed the superior mechanical properties of the nonwoven according to the invention.

Example 2

Elastollan® C85 A 15 HPM was processed on a commercial meltblown line with 1 m spinneret (25-hole / inch) and 100 mm extruder to a meltbown nonwoven with a basis weight of 50 g / m ² . The temperature of the spinning pump was 230 ° C, the temperature of the nozzle was set to 235 ° C. The temperature of the hot air was 225 ° C. The nozzle diameter was 0.4 mm.

A nonwoven having a basis weight of 100 g / m ^{2 was} produced. Elastollan® C 85 A 15 HPM is an aromatic TPU from Elastogran GmbH.

Example 3

Two nonwoven samples from Example 1.2 (100 g / m ² ) and Example 2 were exposed according to DIN EN ISO 4962. To adjust the desired wavelength of light, an external light filter was used. The yellowness index (YI) was determined to determine the discoloration.

After 24 h, the nonwoven from example 3 already shows a strong discoloration. The nonwoven according to the invention is not discolored even after 100 h. This shows the superior lightfastness of the nonwoven according to the invention over nonwovens made of aromatic TPU.

Claims

claims

1. nonwoven based on thermoplastic polyurethane, characterized in that the thermoplastic polyurethane has a crystallization temperature between 130 ° C and 220 ° C and based on aliphatic isocyanates.

2. nonwoven based on thermoplastic polyurethane, characterized in that the thermoplastic polyurethane is obtainable by reacting (a) isocyanates with (b1) polyester diols having a melting point greater than 150 ° C, (b2) polyether diols and / or polyester diols each having a Melting point less

150 ° C and a molecular weight of 501 to 8000 g / mol and (c) diols having a molecular weight of 62 g / mol to 500 g / mol.

3. Nonwoven according to claim 2, characterized in that the molar ratio of the diols (c) having a molecular weight of 62 g / mol to 500 g / mol to the component (b2) is 0.1 to 0.01.

4. fleece based on thermoplastic polyurethane, characterized in that the thermoplastic polyurethane is obtainable by

(i) reacting a thermoplastic polyester with a diol (c) and then

(ii) the reaction product of (i) comprising (b1) polyesterdiol having a melting point greater than 15O ⁰ C and optionally (c) diol respectively smaller together with (b2) polyetherdiols and / or polyesterdiols having a melting point of 15O ⁰ C and a molecular weight of 501 to 8000 g / mol and optionally further (c) diols having a molecular weight of 62 to 500 g / mol with (a) isocyanate, if appropriate in the presence of (d) catalysts and / or (e) auxiliaries.

5. Nonwoven according to one of claims 1 to 4, characterized in that the thermoplastic polyurethane has a hardness between 50 Shore A and 80 Shore D.

6. Nonwoven according to one of claims 1 to 4, characterized in that the nonwoven fabric has a basis weight of 5 to 500 g / m ² , measured according to ISO 9073-1.

7. Nonwoven according to one of claims 1 to 4, characterized in that the nonwoven fabric has a thickness of 0.01 to 5 millimeters (mm), measured according to ISO 9073-2.

8. Seals in the technical sector, hygiene products, filters, medical products, laminates and / or textiles containing nonwoven according to one of claims 1 to 7.

9. A process for the production of nonwoven fabric according to any one of claims 1 to 7, characterized in that one processes a thermoplastic polyurethane having a crystallization temperature between 130 ° C and 220 ° C by meltblown process for nonwoven.

10. A process for the production of nonwoven fabric according to any one of claims 1 to 7, characterized in that one processes a thermoplastic polyurethane having a crystallization temperature between 130 ° C and 22O ⁰ C by spunbond process for nonwoven.