WO2007045586A1

WO2007045586A1 - Shoe soles based on foamed thermoplastic polyurethane (tpu)

Info

Publication number: WO2007045586A1
Application number: PCT/EP2006/067303
Authority: WO
Inventors: Marcus Leberfinger; Carsten GÜNTHER; Denis Bouvier
Original assignee: Basf Se
Priority date: 2005-10-19
Filing date: 2006-10-12
Publication date: 2007-04-26
Also published as: DE102005050411A1; CN101291789A; EP1940600A1

Abstract

The invention relates to a method for producing an outsole from foamed thermoplastic polyurethane by pressing the outsole in an open tool. The outsole obtainable by said method and a shoe provided therewith are also disclosed.

Description

Shoe soles based on foamed thermoplastic polyurethane (TPU)

The present invention relates to a process for the production of an outsole made of foamed thermoplastic polyurethane, wherein the foamed thermoplastic polyurethane is introduced into an open mold and is then pressed to the outsole. Furthermore, the present invention relates to an outsole, obtainable by such a method, as well as a shoe, which contains such a sole. Further embodiments of the present invention can be taken from the claims, the description and the examples. It goes without saying that the features mentioned above and those still to be explained below of the article according to the invention can be used not only in the particular combination indicated, but also in other combinations, without departing from the scope of the invention.

Thermoplastic polyurethanes (hereinafter also referred to as TPU) are partially crystalline materials and belong to the class of thermoplastic elastomers (TPE). They are characterized among others by good strength, abrasion resistance, tear resistance and chemical resistance and can be produced in almost any hardness by suitable raw material composition.

It is known from EP-A-692 516, WO 00/44821, EP-A-1 174 459 and EP-A-1 174 458 to foam thermoplastic polyurethanes with blowing agents, inter alia, for the production of shoe soles.

One differentiates in principle between soles with simple density and with so-called double density. Single density soles consist of a material of substantially uniform density, except for a marginal zone that forms a compact skin and a uniform composition. Double density shoe soles consist of an outer outsole that comes into contact with the ground material in use, and a foamed midsole that is sandwiched in the finished shoe between the outsole and the upper and connects both. In most cases, the outsole has at least a higher density than the midsole for double density shoe soles.

In the conventional method of double-density shoe production, the melt of a thermoplastic elastomer (eg PVC, thermoplastic rubber, TPU, etc.) is melted on a so-called rotary table installation (eg 24 stations D612 from DESMA or MainGroup) (. eg SPE 22.65 TPU DESMA), known to those skilled plasticizing unit in an open sole tool poured (Descom ^® method; DESMA) and then pressed on a so-called displacer. or possibly injected into a closed sole tool. After solidification of the melt and optionally opening the tool, the shoe upper is positioned over the produced compact sole, the tool is sealed by laterally closing jaws and in a next step a polyurethane reactive system containing at least one compound with isocyanate groups, at least one compound with isocyanate-reactive groups and at least one propellant introduced via a known to those skilled dosing in the cavity between the sole and shaft. After complete reaction of the shoe is removed from the mold and sprouts on the shoe are deburred.

To produce a conventional sole soles with simple density can be moved as described above, but with the difference that is dispensed with prior production of a compact outsole. The abrasion resistance is therefore ensured only on the compact outer skin of the resulting polyurethane sole.

From WO 05/066250 a method for the production of shoe soles is known in which thermoplastic polyurethane is foamed in contact with the shoe upper. The foaming takes place in a closed tool. Here, the foamed thermoplastic polyurethane can take over the function of the midsole in a sole with double density, or the function of the outer sole of a sole simple density.

Advantages of thermolpastic polyurethane soles include high strength and low abrasion, good tear resistance and good chemical resistance. On the other hand, however, z. B. rubber soles compared to TPU lower density and especially better slip resistance, especially in wet conditions.

The object of the invention was therefore to develop an outsole which, in addition to the known positive properties of the thermoplastic polyurethanes, has a good slip resistance, both in the dry and in the wet, with a low sole weight.

This object is achieved by an outsole, made of foamed thermoplastic polyurethane, wherein one introduces expandable thermoplastic polyurethane in an open tool and pressed to the outsole, solved.

In the context of the invention is to be understood by an outsole, the unitary part of a shoe sole, which comes in use in contact with the soil material. Accordingly, in the context of the invention under an outsole, the entire shoe sole with simple density to understand. Under a closed tool is a hollow body to understand, in which the material to be formed is introduced. While expanding the thermoplastic polyurethane can indeed displaced gases escape, z. B. on introduced vents, but the TPU is prevented by the walls of the tool and the counterpressure thus building on the free expansion. The tool is ultimately filled by the expansion and the building up internal pressure by the expanding TPU, which is formed by the contact with the mold walls a more or less compact outer skin. The compression factor of the expanded TPU, which results from the ratio of the actual volume of the shaped body and the theoretical volume during free expansion, is usually less than 0.8. TPU outsoles made in the closed form usually have a thickness of 10mm or more.

In the context of the invention, an open tool is to be understood as meaning a casting tool which does not form a closed hollow body during the introduction of the expandable TPU, ie. H. at least to one side of the tool is open. The introduced TPU melt can thus expand freely before it is pressed by a so-called displacer in the mold. The compression factor in a shoe sole according to the invention is usually 0.8 and larger. Thus, in the open mold, the expanding TPU is not compacted on the tool surfaces, i. H. it comes here to none, or only a small formation of a compact outer skin. This means that the outer skin retains a largely cellular and poor surface texture.

In the context of the invention, a compact outer skin means the region of a TPU outsole which has a lower porosity than an area in the interior of the outsole.

The expandable thermoplastic polyurethanes used according to the invention are preferably a mixture comprising thermoplastic polyurethanes and expandable microspheres as blowing agents, particularly preferably thermoplastic polyurethanes and expandable microspheres with a TMA density (defined below) of between 2 and 30 kg / m ³ , preferably between 2 and 10 kg / m ³ . Due to these low TMA densities, the weight percentage use of microspheres can be minimized with comparable density. This leads to cost savings, since usually the microspheres is the price-determining factor with respect to the raw materials of the final product. The preferred expandable microspheres may be in the form of powders or, preferably, masterbatches, the microspheres being well known and commercially available, eg under the trademark Expancell® from AKZO Nobel Industries, Sweden. By the term masterbatch is meant that the expandable microspheres in a carrier z. As binders, waxes or a thermoplastic (eg., TPU, EVA, PVC, PE, PP, PES, PS, TR, etc., or blends thereof) are bound in granular form. At the Position of these micropher- gent masterbatches are generally employed with very low melting point (eg, 60-110 ° C) thermoplastics and very low viscosities to assist in the preparation of masterbatches of expandable microspheres and supports by the use of a masterbatch the lowest possible temperatures prevent premature expansion. The use of such masterbatches avoids the formation of dust, such as those arising from the use and handling of expandable microspheres in powder form. In addition, homogeneous mixing of the expandable microspheres with the TPU is easier with the use of masterbatches.

The TMA density of the expandable microspheres defines itself as the minimum achievable density [kg / m ³ ] of an expandable microspheric powder or masterbatch thereof until the microspheres collapse. These were determined at a heating rate of 20 ° C per minute with a weight of 0.5 mg using a "Stare Thermal Analysis System" from Mttler Toledo.

By using the preferably used expandable microspheres as propellants can be completely dispensed with the use of co-blowing agents. Nevertheless, it is possible for the production of outsoles according to the invention also co-blowing agent, such as. B. exothermic and endothermic chemical blowing agents to use. Examples of exothermic chemical blowing agents are azodicarbonamides. Examples of endothermic chemical blowing agents are citric acid and bicarbonates, such as alkali bicarbonates.

Preferably outsoles according to the invention are produced with a mixture of one or more expandable microspheres and one or more chemical blowing agents. Particularly preferred are blowing agent mixtures containing 5 to 95 wt .-% expandable microspheres and 95 to 5 wt .-% of one or more chemical blowing agents, more preferably 40 to 90 wt .-% expandable microspheres and 60 to 10 wt .-% of a or more chemical blowing agents, in particular 60 to 80% by weight of expandable microspheres and 40 to 20% by weight of one or more chemical blowing agents, each based on the total weight of the expandable microspheres and the chemical blowing agent without the support used to prepare a masterbatch, used.

Overall, the expandable thermoplastic polyurethane for producing an outsole according to the invention preferably contains 0.1 to 30 wt .-%, particularly preferably 1, 5 and 7.5 wt .-% and in particular 2 to 5 wt .-%, based on the total weight of expandable thermoplastic polyurethane, blowing agent.

The expandable thermoplastic polyurethane may preferably contain from 0.1 to 50% by weight, more preferably from 1 to 40% by weight, based on the total weight of the mixture, of plasticizer. Plasticizers may be any common substance. zen be used. Preference is given to using esters of benzoic acid and phthalic acid and derivatives thereof,

To produce the expandable thermoplastic polyurethane, thermoplastic polyurethanes can be used as the sole thermoplastic. Alternatively, it is possible to use TPU blends of other well-known thermoplastics. All known thermoplastics can be used. Examples of these are thermoplastic rubber, ethylene vinyl acetate and polyvinyl chloride. The blend preferably contains at least 40% by weight of thermoplastic polyurethane.

To produce the expanded thermoplastic polyurethanes, the thermoplastic polyurethanes, which are generally present as powder, granules or pellets, are usually mixed with the expandable microspheres and / or the masterbatch and any other additives to be used, such as further blowing agents, other thermoplastics and plasticizers and thermoplastically processed to the shoes and / or shoe parts according to the invention. By the term "thermoplastic processing" is meant any processing which is associated with a melting of the thermoplastic polyurethane.The temperature increase during the thermoplastic processing leads to an expansion of the expandable microspheres and thus to the formation of the expanded thermoplastic polyurethanes Polyurethane, the melt is introduced into open molds, the thermoplastic polyurethane expands there and is pressed by a displacer .. Preferably, the temperature of the thermoplastic polyurethane when introduced into the mold between 100 ° C and 220 ° C, more preferably between 140 ° C and 190 ° C.

By the method described both soled shoes with single and double density are available. To produce shoes with double-density soles, a first, expandable thermoplastic polyurethane, preferably at a temperature between 100 and 220 ° C., more preferably between 140 and 190 ° C., is introduced into the open mold and subsequently through the so-called displacer distributed in the form. The mold used is preferably part of a commercially available rotary table system. The mold temperature is maintained between 10-130 ° C., preferably between 40-70 ° C. After the at least partial solidification of the first expanded thermoplastic polyurethane, the displacer is opened and then the midsole produced. For this purpose, the shoe upper is preferably positioned over the outsole produced by the method described above, the mold is closed again via lateral jaws and, in a next step, the midsole material is introduced into the intermediate space between sole and shaft. Preferably, the midsole material is a second expandable thermoplastic polyurethane or particularly preferably a polyurethane reactive system. Preferably, the density of the midsole material is different from the density of the outsole, in particular, the density of the midsole material is less than the density of the outsole. The thickness of a TPU outsole is preferably less than 10 mm, particularly preferably 5 to 0.5 mm and in particular 3 to 1 mm in the case of a double-density sole

For the production of single-density shoes, the procedure is as above, but the first expandable thermoplastic polyurethane is displaced by the shoe upper or the shoe last, which at the same time leads to a direct adhesion of the not yet solidified first TPU melt to the shoe upper or the shoe last comes. To improve adhesion, a bonding agent can be used on the shoe upper or the shoe bar.

Preferably, the compression factor (= volume of the inventive outsole / volume of the same amount of TPU, based on the weight, with free expansion) of an outsole according to the invention is large 0.8, more preferably in a range of 0.85 to 1, 00 and in particular a range of 0.90 to 0.98. The thickness of any existing skin in an outsole according to the invention is preferably 0.2 mm or less, particularly preferably 0.1 mm or less and in particular 0 mm.

As thermoplastic polyurethanes, the customary and known compounds can be used, as described for example in Kunststoffhandbuch, Volume 7 "Polyurethanes", Carl Hanser Verlag Munich Vienna, 3 Edition 1993, pages 455 to 466 Their preparation is carried out by reacting with diisocyanates Compounds having at least two isocyanate-reactive hydrogen atoms, preferably difunctional alcohols.

As diisocyanates customary aromatic, aliphatic and / or cycloaliphatic diisocyanates are, for example, diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), tri-, tetra-, penta-, hexa-, hepta- and / or octamethylene diisocyanate, 2- Methylpentamethylene-dinocyanat-1, 5, 2-ethyl-butylene-dιιsocyanat-1, 4, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (isophorone diisocyanate, IPDI), 1.4 and / or 1,3-bis (isocyanatomethyl) cyclohexane (HXDI), 1,4-cyclohexanediocyanate, 1-methyl-2,4- and / or -2,6-cyclohexanediisocyanate, 4,4'- 2,4'- and / or 2,2'-dicyclohexylmethane diisocyanate

As isocyanate-reactive compounds, generally known polyhydroxy compounds having molecular weights of 500 to 8,000, preferably 600 to 6,000, especially 800 to 4,000, and preferably an average functionality of 1, 8 to 2.6, preferably 1, 9 to 2.2 , in particular 2 are used, for example, poly esterols, polyetherols and / or polycarbonate diols. Preference is given to using polyesterdiols which are obtainable by reacting butanediol and hexanediol as diol with adipic acid as dicarboxylic acid, the weight ratio of butanediol to hexanediol preferably being 2: 1. Preference is furthermore given to polytetrahydrofuran having a molecular weight of from 750 to 2500 g / mol, preferably from 750 to 1200 g / mol.

As chain extenders it is possible to use generally known compounds, for example diamines and / or alkanediols having 2 to 10 C atoms in the alkylene radical, in particular ethylene glycol and / or butanediol-1, 4, and / or hexanediol and / or di- and / or Tri-oxyalkylenglykole having 3 to 8 carbon atoms in the oxyalkylene lenrest, preferably corresponding oligo-polyoxypropylene glycols, mixtures of the chain extenders can be used. As chain extenders it is also possible to use 1,4-bis (hydroxymethyl) benzene (1,4-BHMB), 1,4-bis (hydroxyethyl) benzene (1,4-BHEB) or 1,4-bis (2 -hydroxyethoxy) -benzene (1, 4-HQEE) are used. Preferred chain extenders are ethylene glycol and hexanediol, particularly preferably ethylene glycol.

Usually, catalysts are used which accelerate the reaction between the NCO groups of the diisocyanates and the hydroxyl groups of the synthesis components, for example tertiary amines, such as triethylamine, dimethylcyclohexylamine, N-methylmorpholine, N, N'-dimethylpiperazine, 2- (dimethylaminoethoxy) - ethanol, diazabicyclo- (2,2,2) octane and the like, and in particular organic metal compounds such as titanic acid esters, iron compounds such as Iron (III) acetylacetonate, tin compounds such as tin diacetate, tin dilaurate or the tin dialkyl salts of aliphatic carboxylic acids such as dibutyltin diacetate, dibutyltin dilaurate, bismuth compounds or the like. The catalysts are usually used in amounts of 0.0001 to 0.1 parts by weight per 100 parts by weight of polyhydroxyl compound.

In addition to catalysts, customary auxiliaries can also be added to the structural components. Mention may be made, for example, of surface-active substances, flame retardants, nucleating agents, lubricants and mold release agents, flow improvers, abrasion improvers, dyes and pigments, inhibitors, stabilizers against hydrolysis, light, heat, oxidation or discoloration, protective agents against microbial degradation, inorganic and / or organic fillers, reinforcing agents and plasticizers, but also chain regulators, such. B. isocyanate-reactive monofunctional compounds.

Outer soles of thermoplastic polyurethane according to the invention preferably have a density of from 0.1 to 1.2 g / cm ³ , more preferably from 0.6 to 1.5, and in particular from 0.75 to 1.0 g / cm ³ . Preferably outsoles according to the invention have an abrasion according to DIN 53516 of less than 120 mm ³ , more preferably less than 100 mm ³ and in particular less than 80 mm ³ .

Outer soles according to the invention have improved slip resistance. The measurement of slip resistance is carried out with the aid of a device for determining the dynamic limit angle of the static friction of shoes. This procedure according to Dr. med. Radio is described in DE 3635263. To measure the outsole is glued to a Dummy shaft. For a direct comparison of the skid resistance, the size and profile of the test specimens must always be identical. Usually, unprofiled rectangular test plates of 3 mm thickness, 15 cm length and 10 cm width are used. This test shoe is placed cyclically parallel to the substrate on this and loaded with a constant, adjustable weight. Before each cycle, the angle of inclination of the ground is increased until the test shoe slides out. For concrete measurement, a steel plate and a load of 40 kg were chosen as the substrate. For measurement in wet conditions, the steel plate was constantly rinsed with water during the test. Further details of this test can also be found under "Testing machine for measuring the static friction angle" (Funk, H .; Jung, K; Berufsgenossenschaftliches Institut für Arbeitssicherheit, St. Augustin).

Outer soles according to the invention are lightweight, non-slip, resistant to hydrolysis and resistant to oil and chemicals and have good tear resistance. Therefore outsoles according to the invention are outstandingly suitable as outsoles for shoes of any kind. This includes, for example, street shoes, slippers and safety shoes. Safety shoes, in particular, are subject to high requirements with regard to skid resistance, chemical and oil resistance, hydrolysis resistance and weight. Therefore, outsoles according to the invention are particularly suitable for the production of safety shoes.

The present invention will be illustrated by the following examples:

Measurement Methods:

Density: according to DIN 53479 Abrasion: according to DIN 53516

slip resistance

As a measure of slip resistance, the critical angle of static friction was measured. This was determined as explained above. The value given in the table is the mean of six tests. Trial 1:

100 parts by weight thermoplastic polyurethane (Elastollan ^® B60A10WHA, E- lastogran GmbH) were mixed with 3 parts by weight TPU black masterbatch Elastollan ^® conc V 917/1 and 2 parts by weight microspheres masterbatch MB095DU120 added, over a DESMA SPE 22.65 plasticized (Temp .: 1 10/160/180 / nozzle = 170 ⁰ C), in one for z. B. DESMA rotary table systems usual, known in the art open form according to the DEScom ^® method introduced and processed via the displacer to a test plate with 15 cm in length, 10 cm in width and 3mm in height. The mold temperature was 60 ° C. The weight of the sole after deburring, its density, the abrasion and the limit angle of static friction are given in Table 1.

Trial 2

The procedure was analogous to experiment 1, wherein 4 parts by weight of microspheres masterbatch MB095DU120 were used instead of the 2 parts by weight of microspheres masterbatch MB095DU120. The weight of the sole after deburring, its density, the abrasion and the limit angle of static friction are given in Table 1.

Trial 3

The procedure was analogous to experiment 1, wherein prior to foaming additionally 2 parts by weight of the chemical blowing agent Hydrocerol ^® BIH 40 .Cariant GmbH, were added. The weight of the sole after deburring, its density, the abrasion and the limit angle of static friction are given in Table 1.

Comparative experiment 1

The procedure was analogous to experiment 1, wherein the addition of MB095DU120 was omitted. The processing temperatures here were raised by 20 ° C over all zones compared to Verusch 1. The weight of the sole after deburring, its density, the abrasion and the limit angle of static friction are given in Table 1.

Comparative experiment 2

As a comparative experiment 2, a standard rubber sole of the same size was used. The weight of the sole after deburring, its density, the abrasion and the limit angle of static friction are given in Table 1.

Table 1

Table 1 shows that the outsoles of the invention have a similar or only slightly worse slip resistance compared to rubber at lower density and lower abrasion. In comparison to non-foamed TPU, slip resistance and density are substantially improved with only a slight increase in abrasion.

Claims

claims

1. A process for producing an outsole of foamed thermoplastic polyurethane, characterized in that one introduces expandable thermoplastic polyurethane in an open tool and pressed to the outsole.

2. The method according to claim 1, characterized in that the expandable thermoplastic polyurethane from 0.1 to 30 wt .-%, based on the total weight of the expandable thermoplastic polyurethane, of blowing agent.

3. The method according to claim 1 or 2, characterized in that the expandable thermoplastic polyurethane as a blowing agent expandable Mikrosphe- ren, exothermic or endothermic chemical blowing agents or combinations thereof.

4. The method according to claim 3, characterized in that the blowing agent used is a mixture of expandable microspheres and chemical blowing agents.

5. The method according to claim 4, characterized in that the propellant mixture comprises 5 to 95 wt .-% expandable microspheres and 95 to 5 wt .-% chemical blowing agent.

6. The method according to claim 3 to 5, characterized in that the expandable microspheres have a TMA density between 2 and 30 kg / m ³ .

7. The method according to claim 2 to 6, characterized in that the expan- dierbare thermoplastic polyurethane contains between 0.1 and 50 wt .-% plasticizer.

8. outsole, obtainable according to one of claims 1 to 7.

9. outsole according to claim 8, characterized in that the density is less than 1, 05 g / cm ³ ,.

10. Shoe comprising an outsole according to claim 8 or 9.

1 1. Shoe according to claim 10, characterized in that the foamed thermoplastic polyurethane is adhesively bonded by the foaming process with the shoe upper.

A shoe according to claim 10 or 11, further comprising a midsole comprising foamed polyurethane or foamed thermoplastic polyurethane.