WO2022058335A1

WO2022058335A1 - Production of a form-molded shoe component

Info

Publication number: WO2022058335A1
Application number: PCT/EP2021/075294
Authority: WO
Inventors: Nils ALTROGGE; Jean Philippe ROMAIN; Nicolas HUTTON; Changwoo Shin; Ilmarin Heitz
Original assignee: On Clouds Gmbh
Priority date: 2020-09-15
Filing date: 2021-09-15
Publication date: 2022-03-24
Also published as: CH717846A2

Abstract

The invention relates to a method for producing a form-molded shoe component, more particularly a running shoe component, comprising the steps: a. providing a polymer granulate; b: pre-treating the polymer granulate including binding to or in the polymer granulate a first physical propellant at a first pressure and a first temperature; c. form-molding the pre-treated polymer granulate in a form molding system, the form molding system comprising: i. a drum having a drum feed, the drum defining a treatment chamber including a screw arranged therein; ii. a nozzle fluidically connected to the treatment chamber; and iv. a mold having a mold cavity which is fluidically connected to the nozzle. Form molding includes the following steps: introducing a second physical propellant by means of the propellant feed and introducing the polymer granulate pre-treated in step b. into the treatment chamber through the drum feed, which is fluidically connected to the treatment chamber; melting the polymer granulate in the treatment chamber to produce a molten, in particular monophase polymer composition; and injecting the molten polymer composition into the mold cavity and foaming the polymer composition as a result of the expansion of the first and/or second propellant.

Description

Production of a molded foam shoe component

technical field

The present invention relates to the technical field of shoe manufacture, in particular foamed shoe components, and relates to a method for producing a molded foamed shoe component.

State of the art

Molded foam materials have a large number of pores or cells in the foam material, which means that molded foam materials are particularly suitable as cushioning elements, such as shoe soles. Typically, such foams are made using blowing agent additives. A polymeric material, typically a thermoplastic polymer such as thermoplastic polyurethane, is thereby melted in an extruder. A blowing agent additive is typically added to the polymer material, which expands under predefined conditions and can form the pores or cells in the molded foam material. When it comes to blowing agent additives, a distinction is typically made between chemical and physical blowing agents. Physical blowing agents are those that can expand directly by changing physical parameters, such as pressure and temperature, or can change from the liquid or solid state of aggregation to the gaseous state. Known physical blowing agents are CO ₂ , nitrogen, water, hydrocarbons such as propane, butane, pentane or hexane, and hydrocarbon derivatives, in particular halogenated derivatives such as dichloromethane, chloroform or fluorocarbons. Chemical blowing agents are blowing agents from which a blowing agent can be released in situ under predetermined conditions by chemical reaction. These include, for example, diazo compounds (liberation of N ₂ ), metal hydrides (liberation of H ₂ ) and carbonates (liberation of CO ₂ ). Blowing agents that are available as supercritical fluids (SCF) have established themselves as a special case among physical blowing agents. The best-known process in which SCFs are used is the so-called MuCell® process. Here, a polymer composition is mixed with a SCF in an extruder to form a single-phase mixture and then injected into a mold. A drop in pressure in the mold causes the blowing agent to separate from the polymer solution and vaporize, resulting in the formation of microcells. CO ₂ or nitrogen is usually used as the SCF.

Presentation of the invention

A problem with foam molding with blowing agents is controlling the pore size in the foam. Furthermore, although foaming with SCF is widely used with thermoplastic polyurethane, it is still problematic with other materials, particularly polyamides and copolymers thereof. Controlling the pore size of the foam is particularly relevant for shoe components, especially in the area of running shoes, since on the one hand the lowest possible density should be achieved in order to reduce the overall weight of the shoe and on the other hand a high degree of stability must be guaranteed. Furthermore, although the control of the pore size can be significantly improved by means of supercritical fluids, the use of supercritical fluids is costly and not ecological since a relatively high level of energy is required to provide the required high pressures and temperatures.

It is therefore the general object to further develop the state of the art for the production of foamed shoe components and preferably to overcome one or more of the above-mentioned disadvantages of the prior art in whole or in part. In advantageous embodiments, a method is provided in which the formation of pores, in particular the pore size of the foamed material, can be controlled more precisely. In further advantageous embodiments, a method is provided which makes it possible to produce a foamed shoe component that has a low density, but at the same time ensures high stability. In further embodiments, a more energy-efficient method for producing a molded foam shoe component compared to the prior art is provided.

The general problem is solved by the subject matter of the independent patent claims. Further advantageous embodiments emerge from the dependent claims and the overall disclosure.

A first aspect relates to a method for producing a molded foam shoe component, in particular a running shoe component, comprising the steps: a. providing a polymer granulate; b. Pretreating the polymer granules comprising binding a first physical blowing agent to or in the polymer granules at a first pressure and a first temperature; c. Foam molding the pretreated polymer granules in a foam molding system, the foam molding system comprising: i. a barrel having a barrel lead, the barrel defining a processing space with a screw disposed therein; ii. a propellant supply in fluid communication with the processing space; iii. a nozzle in fluid communication with the processing space; and iv. a mold having a mold cavity in fluid communication with the nozzle. The foam molding comprises: the introduction of a second physical blowing agent by means of the blowing agent feed and the introduction of the in step b. pretreated polymer granules into the processing space through the drum feed line which is in fluid communication with the processing space; Melting the polymer granules in the processing room to produce a molten, in particular single-phase, polymer composition; and injecting the molten polymer composition into the mold cavity and foaming the polymer composition by expansion of the first and/or second blowing agent. By pretreating the polymer granules with a first physical blowing agent additional blowing agent is introduced into the polymer granulate before it is introduced into the drum. This makes it possible to further reduce the density of the manufactured shoe component. In addition, the pore size and pore structure can be controlled more precisely via the amount of bound first blowing agent. It has been found that the first blowing agent can be retained in the polymer granules for a relatively long period of time, in particular for several hours. Typically, the polymer granules are melted in the processing room on the one hand and the polymer granules and the first blowing agent bound thereto are mixed on the other hand, in particular to form a single-phase system.

The pretreatment of the polymer granules with the first blowing agent can include impregnation, for example. The first blowing agent can bind to the surface of the polymer granules. This can include both the binding of the first blowing agent on the outer surface and the binding within the polymer granules, with the blowing agent diffusing into the polymer granules. The pre-treatment has the advantage, among other things, that the foam-molded component shows less material shrinkage and distortion after production than a foam-molded component which is only produced according to a process consisting of step c. will be produced.

The polymer granules can typically have a certain porosity, so that the first blowing agent can penetrate better into the individual polymer particles. Typically, the first pressure and the first temperature are greater than normal pressure (1 bar) or higher than room temperature (25° C.). The person skilled in the art understands that the terms first pressure and first temperature (or second pressure, second temperature, etc.), unless otherwise stated, can also include a temperature or pressure range within which these parameters are maintained. Compared to a process without step b. the process according to the invention enables the production of a foam-moulded shoe component with smaller pores in the foam and a significantly more homogeneous distribution of the pores over the entire foam-moulded component. In addition, the weight of the molded foam Component reduced, which is beneficial for the runner, as they tire less quickly. Typical examples of suitable commercially available polymer granules, which can be used directly without further pretreatment, are polyether blockamide such as PEBAX 2533 (CAMPUSplastics), PEBAX 3533 (CAMPUSplastics), PEBAX 35R53 (CAMPUSplastics), or polyamide such as RILSAN BZMNO (CAMPUSplastics, PA1 1), VESTAMID E40 -S3 (Evonik Industries AG, PA1 2), VESTAMID E47-S1 (Evonik Industries AG, PA1 2).

According to DIN 62, for example, the polymer granules can have a water absorption of 0.8 to 1.2. Typically, the density according to ISO 1183 of the polymer granulate is between 0.9 and 1.1 g/cm ³ .

The expansion of the first and/or second blowing agent typically occurs as a result of a drop in pressure, which can already occur when the molten polymer composition is injected into the mold cavity, and/or also after the injection, for example by increasing the volume of the mold cavity or by opening valves in the mold. can be triggered.

In some embodiments, the first and/or the second blowing agent is selected from CO ₂ , N ₂ and mixtures thereof. CO ₂ is to be preferred for the first blowing agent, since this is typically more soluble in the polymer granulate, in particular because of its physico-chemical properties, and is better bound. This applies above all when polar thermoplastic elastomers such as polyurethane, polyamide or derivatives thereof are used.

In some embodiments, the pretreatment in step b. 3 to 8% by weight, preferably 5 to 6% by weight, of CO ₂ , based on the polymer granules, are bound on or in the polymer granules. This allows a foam-moulded

Shoe component can be achieved with an advantageous density of about 0.4 g / cm ³ . In further embodiments, the mold cavity can be expandable in volume. This typically involves expanding the volume of the mold cavity during injection of the polymer composition and/or during foaming. This can be achieved, for example, by at least one movable wall of the mold, which can be moved in a controlled manner under the control of a control unit, so that the volume of the mold cavity increases.

In some embodiments, the pretreatment in step b. carried out in a pressure reactor, in particular an autoclave.

In further embodiments, the first pressure in step b. 25 bar to 55 bar. Irrespective of this, the first temperature in step b. 0 °C to 150 °C, in particular 40 °C to 120 °C. The first temperature is preferably above room temperature, since this accelerates the binding of the first physical blowing agent on and in the polymer granules. In particular, this increases the depth of penetration of the propellant into the particles of the polymer granules. This is advantageous because blowing agent that has penetrated the granulate remains bound for a significantly longer time. The impregnated polymer granules can thus be stored longer and handled more easily, in particular transferred, without significant amounts of the physical blowing agent being lost. On the other hand, the first temperature selected must not be too high, as this can cause polymer material, in particular thermoplastic material such as polyamide or polyether block amide (PEBA/PEBAX®), to be partially split or degenerate. This is problematic for use in the shoe sector, since such a partially degrading material can quickly lead to insufficient cushioning over the course of use of the shoe, which can lead to knee, hip and ankle pain in the wearer.

In some embodiments, before step b. by heating up

30 to 130° C., in particular 60° C. to 120° C., in particular 50° C. to 90° C., dried, whereby the amount of absorbed or absorbable blowing agent in the polymer granules is increased. The drying can take place down to a maximum residual moisture content of 0.02%.

In further embodiments, the mold can be maintained at a temperature of 20 to 80°C at least during the injection and foaming of the polymer composition. This can be achieved, for example, by an external heating element or by a mold that can be heated. In particular, the mold can be brought to the predetermined temperature by means of an oil and/or water heating element. The choice of temperature has a significant influence on the density, or the porosity and cell size of the foam.

In some embodiments, the second physical blowing agent is present as a supercritical fluid, particularly during delivery and/or in the processing space. The supercritical state can be reached before it is introduced into the processing room or in the processing room itself. One advantage of using a supercritical fluid is that a single-phase system of polymer and blowing agent is achieved in the processing room, which results in a low density of the shoe component and a uniform Allows cell distribution in the foam. This is particularly relevant for shoe components such as soles, as an uneven distribution of the cells in the foam can mean that the foam is more flexible in some areas than in others, which can lead to an uncomfortable walking sensation and even anatomical misalignments. However, the proportion of the supercritical fluid should be reduced from an energetic and ecological point of view, since reaching the supercritical state is energy-intensive due to the high pressure and temperature required. By combining the impregnation of step b. the amount of supercritical fluid required in step c. can be significantly reduced without any loss in the quality of the foam-moulded shoe component. In further embodiments, the mold of the foam molding system is equipped with a gas counter-pressure device, by means of which a counter-pressure, preferably from >0 bar to 40 bar, in particular 1 bar to 40 bar, is applied to the Polymer composition can be exercised. The expansion of the blowing agent can be slowed down or weakened by exerting a counter-pressure. This enables better control of the pore size and cell structure of the foam-moulded component, as well as more even distribution.

In further embodiments, the polymer granules in step b. maintained at the first pressure and temperature for 2 hours to 8 hours, preferably for 2 hours to 5 hours. Typically, this period of time is sufficient to bind a sufficient amount of the first blowing agent on or in the polymer granules.

In some embodiments, after step b. that in step b. pretreated polymer granules are fed under a second pressure into the foam molding system, in particular into the processing room. The second pressure can preferably be at least 50%, in particular at least 75%, in particular at least 90%, in particular at least 95%, in particular at least 100% of the first pressure. This ensures that no significant amount of bound blowing agent is desorbed during transfer into the foam molding system. It has been found here that a pressure which is only 50% of the first pressure is already sufficient to essentially prevent the desorption. The second pressure is typically no more than 200%, in particular no more than 150%, in particular no more than 100% of the first pressure.

In further embodiments, the polymer granules have a Shore hardness of 70 to 85. In some embodiments, the polymer granulate has a density of 0.9 g/cm ³ to 1.5 g/cm ³ , preferably 1.0 g/cm ³ to 1.2 g/cm ³ . The denser the polymer granules are, the lower the amount of bound first blowing agent typically is. The use of polyamide and polyether block amide as polymer granules is particularly advantageous with regard to the uptake and absorption of the first physical blowing agent, in particular CO ₂ .

In some embodiments, the polymer granulate comprises a thermoplastic elastomer, in particular a polyamide, a polyether block amide or a thermoplastic polyurethane. Alternatively, the polymer granulate can consist of a thermoplastic elastomer, in particular a polyamide, a polyether block amide or a thermoplastic polyurethane.

In further embodiments, the shoe component is a shoe sole, in particular a midsole. Such a shoe sole can be provided in that the mold cavity of the mold of the foam molding system is designed in such a way that during the foam molding in step c. a shoe sole is created.

In some embodiments, the step c. produced shoe component represent a blank of a shoe component, which is processed in a subsequent process step to the finished shoe component. For example, this can be a blank for a shoe sole, which is then pressed into a finished sole by compression molding or which is then colored or surface-treated in some other way. In some embodiments, for example after the polymer composition has been foamed by expansion of the first and/or second blowing agent, the molded foamed shoe component produced can be reshaped by compression molding, in particular in a compression molding press. In some embodiments, the nozzle can be designed so that it can be closed and, in particular, can only be open for an injection period during the injection of the polymer composition. The injection duration can be between 0.5 seconds and 2 seconds, for example.

In some embodiments, the molded foam shoe component is a shoe sole, in particular a midsole, and can be connected to a shoe upper in an additional step, so that a shoe, in particular a running shoe, is produced.

A further aspect relates to a foam-moulded shoe component, in particular a shoe sole, produced by a method according to the embodiments disclosed here.

In some embodiments, the molded foam shoe component may have a density of from 0.15 g/cm ³ to 0.5 g/cm ³ , preferably from 0.25 g/cm ³ to 0.5 g/cm ³ , preferably 0.3 g/cm ³ .

In further embodiments, the molded foam shoe component can have an Asker C hardness of 40 to 65, in particular 45 to 65.

In some embodiments, the molded foam shoe component can have pores or cells. In particular, the pores can have a pore size, or the cells can have a cell size, from 30 μm to 1600 μm, in particular from 300 μm to 1600 μm, in particular from 600 μm to 1000 μm.

In some embodiments, the pore size is smaller in a first region of the shoe component than in a second region. Preferably, the shoe component is a midsole having a top and a bottom, wherein the Top side in the operative state, ie when worn, faces the wearer's foot and the bottom side faces the ground. Preferably, the first portion of the midsole is closer to the top of the midsole than the second portion of the midsole. Thus, the smaller pores are located at the top and therefore closer to the foot of the wearer in the operative state. The pores in the first area can have a pore size of 30 μm to 500 μm, in particular from 100 μm to 300 μm. In some embodiments, the pores in the second region can also have a pore size of from 300 μm to 1600 μm, in particular from 600 μm to 1000 μm.

Claims

patent claims

1. A process for producing a molded foam shoe component, comprising the steps of: a. providing a polymer granulate; b. Pretreating the polymer granules comprising binding a first physical blowing agent to or in the polymer granules at a first pressure and a first temperature; c. Foam molding the pretreated polymer granules in a foam molding system, the foam molding system comprising: i. a barrel having a barrel lead, the barrel defining a processing space with a screw disposed therein; ii. a propellant supply in fluid communication with the processing space; iii. a nozzle in fluid communication with the processing space; IV. a mold having a mold cavity in fluid communication with the nozzle; wherein the foam molding comprises: introducing a second physical blowing agent by means of the blowing agent supply and introducing the pretreated polymer granules into the processing space; melting the polymer granules in the processing room to produce a molten polymer composition; injecting the molten polymer composition into the mold cavity and foaming the polymer composition by expansion of the first and/or second blowing agent. A method according to claim 1, wherein the first and/or second physical blowing agent is selected from CO ₂ , N ₂ and mixtures thereof. A method according to any one of the preceding claims, wherein the mold cavity is volume expandable and the volume is expanded during foaming of the polymer composition. Method according to one of the preceding claims, wherein the pre-treatment in step b. carried out in an autoclave. Method according to one of the preceding claims, wherein in step b. the first pressure is 35 bar to 55 bar, and/or the first temperature is 0°C to 150°C, preferably 40°C to 120°C. Method according to one of the preceding claims, wherein the polymer granules before step b. is dried by heating to 30 to 130°C. A method according to any one of the preceding claims, wherein the mold is maintained at a temperature of from 20 to 80°C at least during the injection and foaming of the polymer composition. Method according to one of the preceding claims, wherein the second blowing agent is present as a supercritical fluid, in particular during the introduction and/or in the processing space. Method according to one of the preceding claims, in which the mold is equipped with a gas counter-pressure device, by means of which a 14

Back pressure, preferably from >0 bar to 40 bar, is applied to the polymer composition. 0. The method according to any one of the preceding claims, wherein in step b. the polymer granules are maintained at the first pressure and temperature for 2 hours to 8 hours, preferably for 2 hours to 5 hours. 1 . Method according to one of the preceding claims, wherein in step b. pretreated polymer granules are fed under a second pressure into the foam molding system, in particular into the processing space, the second pressure preferably being at least 50%, in particular at least 75%, in particular at least 90%, in particular at least 95%, in particular at least 100% of the first pressure amounts to. 2. The method according to any one of the preceding claims, wherein the polymer granules have a Shore hardness of 70 to 85 and/or a density of 0.9 g/cm ³ to 1.5 g/cm ³ , preferably 1.0 g/cm ³ to 1 .2 g/cm ³ . 3. The method according to any one of the preceding claims, wherein the polymer granulate comprises a thermoplastic elastomer, in particular a polyamide, a polyether block amide or a thermoplastic polyurethane. 4. The method according to any one of the preceding claims, wherein the shoe component is a shoe sole, in particular a midsole, and wherein the shoe sole is preferably connected to a shoe upper in an additional step, so that a shoe, in particular a running shoe, is produced. 15

15. The method according to any one of the preceding claims, wherein the nozzle can be closed and is only open during the injection of the polymer composition for an injection duration, and the injection duration is preferably between 0.5 and 2 seconds.

16. The method according to any one of the preceding claims, wherein after the foaming of the polymer composition by expansion of the first and / or second blowing agent, the foamed shoe component produced is post-formed by compression molding.

17. Foam-moulded shoe component, in particular a shoe sole, produced by the method according to one of claims 1 to 16. 18. Foam-moulded shoe component, in particular a shoe sole, according to claim

1 7 which has a density of 0.1 5 g/cm ³ to 0.5 g/cm ³ .

19. Molded foam shoe component, in particular a shoe sole, according to claim

1 7 or 18, which has an Asker C hardness of 40 to 65.