DE102005050411A1 - Shoe soles based on foamed thermoplastic polyurethane (TPU) - Google Patents

Abstract

The present invention relates to a method for producing an outsole from foamed thermoplastic polyurethane, in which this is produced in an open mold and pressed to form the outsole, as well as an outsole obtainable by such a process and a shoe having such an outsole.

Description

The The present invention relates to a process for the preparation of a Outsole made of foamed thermoplastic Polyurethane, being the foamed thermoplastic polyurethane introduced into an open tool and then pressed to the outsole. Furthermore The present invention relates to an outsole obtainable according to Such a method, as well as a shoe, such an outsole contains. Further embodiments The present invention are the claims, the description and to take the examples. It is understood that the above mentioned and to be explained below features of the subject invention not only in the specified combination, but also in Other combinations are usable without the scope of the invention to leave.

thermoplastic Polyurethanes (also referred to below as TPU) are partially crystalline Materials and belong to the class of thermoplastic elastomers (TPE). they draw among other things by good strength, abrasion resistance, tear propagation resistance and chemical resistance out and can in almost any hardness be prepared by suitable raw material composition.

It are from EP-A-692 516, WO 00/44821, EP-A-1174459 and EP-A-1174458 Process known, thermoplastic polyurethanes with blowing agents among other things for the production of shoe soles to foam.

you distinguishes in principle between soles with simple density and with so-called double density. Shoe soles with simpler Density consist of a material with a substantially uniform Density, apart from a marginal zone that forms a compact skin, and uniform composition. Double soled shoe soles consist of an outer outsole, which comes in contact with the soil material in use, and one foamed Midsole, in the finished shoe between outsole and shoe upper is arranged and connects both. Most has shoe soles with double density the outsole at least a higher density as the midsole.

In the conventional method of double-density shoe production, the melt of a thermoplastic elastomer (eg PVC, thermoplastic rubber, TPU, etc.) is applied to a so-called rotary table installation (eg 24 stations D612 from DESMA or MainGroup) via a suitable, the Expert known plasticizing unit (eg SPE 22.65 TPU DESMA) poured into an open sole tool (DEScom ^® process, 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 from above, 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 isocyanates reactive groups and at least one propellant, introduced via a dosing unit known in the art 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 Production of a conventional Shoe sole with simple density can proceed as described above be, but with the difference that on a previous production a compact outsole is waived. The abrasion resistance is therefore only about the compact outer skin ensures the resulting polyurethane sole.

Out WO 05/066250 discloses a method for producing shoe soles, in the thermoplastic polyurethane in contact with the shoe upper foamed becomes. The foaming takes place in a closed tool. This can be the foamed thermoplastic polyurethane adds the function of midsole a double-density sole, or the outer outsole function adopt a sole of simple density.

advantages of shoe soles made of thermolpastic polyurethane are next high Strength and low abrasion good tear propagation resistance and good chemical resistance. On the other hand, however, z. B. rubber soles compared to TPU a lower density and above all better slip resistance, especially under wet conditions.

task The invention was therefore to develop an outsole, in addition to the known positive properties of the thermoplastic polyurethanes, with a low sole weight a good skid resistance, both in the dry as well as in the wet, having.

These Task is by an outsole, made of foamed thermoplastic Polyurethane, wherein one is expandable thermoplastic polyurethane into an open tool and pressed to the outsole, solved.

in the Frame of the invention is intended under an outsole of uniform Part of a shoe sole to be understood when in use comes with the soil material. Accordingly, in the context of the invention below an outsole also the entire sole of the sole with a simple density to understand.

Under a closed tool is a hollow body to understand in the is introduced to be formed material. While expanding the thermoplastic polyurethane can though displaced Gases escape, z. B. over introduced vents, but the TPU gets through the walls of the tool and itself thus preventing backpressure from free expansion. The Ultimately, the tool becomes the expansion and the building up internal pressure is filled by the expanding TPU, causing by the contact formed to the tool walls a more or less compact outer skin becomes. The compression factor of the expanded TPU that is made the relationship of the actual Volume of the molding and the theoretical volume at free expansion is usually at less than 0.8. Outsole made of TPU, which in the closed form have been produced usually a thickness of 10 mm and more.

Under an open tool is intended in the context of the invention, a casting tool be understood that while the introduction of the expandable TPU does not form a closed hollow body, d. H. at least to one side of the tool is open. The introduced TPU melt can thus expand freely, before this one of a so-called displacer is pressed in the mold. The compression factor in a shoe sole according to the invention is usually 0.8 and larger. Consequently In the open mold, the expanding TPU on the tool faces does not compacted, d. H. it comes here to none, or only minor training a compact outer skin. This means that the outer skin maintains a largely cellular and poor surface texture.

Under a compact outer skin is within the scope of the invention, the range of a TPU outsole to understand that has a lower porosity than a range inside 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 having 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 can be in the form of powder or are preferably used as masterbatch, the microspheres generally known and commercially available, for example under the brand name 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. In the production of these micro-pheric masterbatches, usually thermoplastics with a very low melting point (eg 60-110 ° C) and very low viscosities are used to prepare the masterbatches from expandable microspheres and carriers by using as much as possible low temperatures to avoid 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 at a heating rate of 20 ° C per minute with a weight of 0.5 mg determined using a "Stare Thermal Analysis System" from the company Mttler Toledo.

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

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

All in all contains the expandable thermoplastic polyurethane for producing a outsole according to the invention preferably 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 the expandable thermoplastic polyurethane, blowing agent.

Prefers For example, the expandable thermoplastic polyurethane can be from 0.1 to 50% by weight, more preferably from 1 to 40% by weight, based on the total weight of the mixture, Contain softener. As plasticizer, all common substances can be used become. Preference is given to esters of benzoic acid and of phthalic acid and Used derivatives thereof

to Production of the expandable thermoplastic polyurethane can be thermoplastic Polyurethanes used as the sole thermoplastic become. Alternatively, it is possible to use TPU blends to use from other well-known thermoplastics It can all known thermoplastics are used. Examples therefor are thermoplastic rubber, ethylene vinyl acetate and polyvinyl chloride. Preferably contains the blend thereby at least 40 wt .-% thermoplastic polyurethane.

to Preparation of the expanded thermoplastic polyurethanes are the thermoplastic polyurethanes, which are generally in powder form, Granules or pellets are present, usually with the expandable Microspheres and / or the masterbatch and optionally zu using other additives, such as other propellants, mixed thermoplastics and plasticizers and thermoplastic to the shoes and / or shoe parts according to the invention processed. The term "thermoplastic processing" means any processing meant that with a melting of the thermoplastic polyurethane connected is. Due to the temperature increase in the thermoplastic Processing there is an expansion of expandable microspheres and thus to the formation of the expanded thermoplastic polyurethanes. To prepare the polyurethanes according to the invention, the melt registered in open forms, the thermoplastic polyurethane expands there and will by a displacer pressed. Preferred is the temperature of the thermoplastic polyurethane when entering in 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. For the production of 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, introduced into the open mold and then by the so-called displacer in the Distributed 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 more preferably a polyurethane reactive system. Preferably, the density of the midsole material differs from that Density of the outsole, in particular the density of the midsole material is lower than the density of the outsole. The thickness of a TPU outsole for a double density sole is preferably less than 10 mm, more preferably 5 to 0.5 mm, and most preferably 3 to 1 mm.

to Production of single-density shoes is done as above, however, the first expandable thermoplastic polyurethane becomes displaced by the shoe upper and the shoe last, thereby simultaneously to a direct adhesion of the not yet solidified first TPU melt comes on the shoe upper and the shoe last itself. To improve the liability can on the shoe upper and the shoe bar a bonding agent be used.

Prefers if the compression factor of an outsole according to the invention is greater than 0.8, more preferably in a range of 0.85 to 1.00 and especially in a range from 0.90 to 0.98. The thickness of any existing Skin is in an outsole according to the invention preferably 0.2 mm or less, more preferably 0.1 mm or lower and in particular 0 mm.

When thermoplastic polyurethanes can the usual and known compounds are used, as for example in Kunststoffhandbuch, Volume 7 "Polyurethane", Carl Hanser Verlag Munich Vienna, 3rd edition 1993, pages 455 to 466 are described. Your Production takes place by reaction of diisocyanates with compounds with at least two isocyanate-reactive hydrogen atoms, preferably difunctional alcohols.

When Diisocyanates usual aromatic, aliphatic and / or cycloaliphatic diisocyanates For example, diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), tri-, tetra-, penta-, hexa-, hepta- and / or octamethylene diisocyanate, 2-methylpentamethylene diisocyanate-1,5, 2-ethyl-butylene-diisocyanate-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-cyclohexane diisocyanate, 1-methyl-2,4- and / or 2,6-cyclohexane diisocyanate, 4,4'-, 2,4'- and / or 2,2'-dicyclohexylmethane diisocyanate

When across from Isocyanate-reactive compounds may include well-known polyhydroxyl compounds with molecular weights of 500 to 8000, preferably 600 to 6000, in particular 800 to 4000, and preferably an average functionality of 1.8 to 2.6, preferably 1.9 to 2.2, in particular 2 are used, for example, polyesterols, 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 from butanediol to hexanediol is preferably 2: 1. Preference is still given Polytetrahydrofuran having a molecular weight of 750 to 2500 g / mol, preferably 750 to 1200 g / mol.

When Chain extender can well-known compounds are used, for example Diamines and / or alkanediols having 2 to 10 C atoms in the alkylene radical, in particular ethylene glycol and / or 1,4-butanediol, and / or hexanediol and / or di- and / or tri-oxyalkylenglykole having 3 to 8 carbon atoms in the oxyalkylene radical, preferably corresponding oligo-polyoxypropylene glycols, wherein mixtures of the chain extenders can be used. When chain can also 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 are chain extenders Ethylene glycol and hexanediol, more preferably ethylene glycol.

Usually Catalysts are used which control the reaction between the NCO groups of the diisocyanates and the hydroxyl groups of the synthesis components accelerate, 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 e.g. Iron (III) acetylacetonate, tin compounds, such as tin diacetate, tin dilaurate or the Zinndialkylsalze aliphatic carboxylic acids such as dibutyltin diacetate, dibutyltin dilaurate, bismuth compounds or similar. The catalysts are usually in amounts of 0.0001 to 0.1 parts by weight per 100 parts by weight of polyhydroxyl compound used.

In addition to catalysts, it is also possible to add conventional auxiliaries 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.

Thermoplastic polyurethane outsoles according to the invention preferably have a density of from 0.1 to 1.2 g / cm ³ , more preferably from 0.6 to 1.05 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 in DE 3635263 described. 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, hydrolysis resistant and oil and chemical resistant and have a good tear propagation resistance. Therefore, outsoles according to the invention are suitable excellent as outsoles for Shoes of any kind. This includes, for example, street shoes, Slippers and safety shoes. Especially on safety shoes high requirements regarding Skid resistance, chemical and oil resistance, hydrolysis resistance and weight put. Therefore, outsoles according to the invention are suitable especially for the production of safety shoes.

The present invention will be illustrated by the following examples: Density: according to DIN 53479 abrasion: according to DIN 53516

slip resistance

When measure for skid resistance the critical angle of static friction was measured. This one became as above explains certainly. The value given in the table is around the mean of six exams.

Trial 1:

100 parts by weight thermoplastic polyurethane (Elastollan ^® B60A10WHA, Elastogran GmbH) were mixed with 3 parts by weight TPU black masterbatch Elastollan ^® conc V 917/1 and 2 parts by weight microspheres masterbatch MB095DU120, a DESMA SPE plasticized 22.65 (temp .: 110/160 / 180 / nozzle = 170 ° C), in one for z. B. DESMA round 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 3 mm 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

It was carried out analogously to experiment 1, wherein instead of 2 parts by weight Microspheres masterbatch MB095DU120 4 parts by weight of microspheres masterbatch MB095DU120 were used. The weight of the sole after deburring, their density, the abrasion and the critical angle of static friction are 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

It was carried out analogously to experiment 1, with the addition of MB095DU120 was waived. The processing temperatures became here over all Zones raised by 20 ° C compared to Verusch 1. The weight of Sole after deburring, their density, abrasion and the critical angle the stiction are given in Table 1.

Comparative experiment 2

When Comparative experiment 2, a standard rubber sole of the same size was used. The weight of the sole after deburring, their density, abrasion and the critical angle of static friction are given in Table 1.

Table 1

table 1 shows that the outsoles according to the invention Compared to rubber with lower density and less abrasion a similar or have only slightly worse skid resistance. in the Compared to non-foamed TPU are skid resistance and density with only a small increase of Abrasion significantly improved.

Claims (12)

Process for producing an outsole made of foamed thermoplastic polyurethane, characterized in that one introduces expandable thermoplastic polyurethane in an open tool and pressed to the outsole. Method according to claim 1, characterized in that the expandable thermoplastic polyurethane is 0.1 to 30% by weight, based on the total weight of the expandable thermoplastic Polyurethane, having blowing agent. Method according to claim 1 or 2, characterized that the expandable thermoplastic polyurethane as a blowing agent expandable microspheres, exothermic or endothermic chemical Propellants or combinations thereof contains. Method according to claim 3, characterized that as blowing agent a mixture of expandable microspheres and chemical blowing agents is used. Method according to claim 4, characterized in that that the blowing agent mixture 5 to 95 wt .-% expandable microspheres and 95 to 5 wt .-% chemical blowing agent. A method according to claim 3 to 5, characterized in that the expandable microspheres a TMA density between 2 and 30 kg / m ³ have. Method according to Claims 2 to 6, characterized the expandable thermoplastic polyurethane is between 0.1 and 50 wt .-% plasticizer. Outsole, available according to one of the claims 1 to 7. Outsole according to claim 8, characterized in that its density is less than 1.05 g / cm ³ . Shoe comprising an outsole according to claim 8 or 9. Shoe according to claim 10, characterized that the foamed thermoplastic polyurethane by the foaming process adhering to the shoe upper connected is. Shoe according to claim 10 or 11, further comprising a midsole that's foamed Polyurethane or foamed having thermoplastic polyurethane.