阅读说明：本技术 制造聚氨酯泡沫鞋垫的方法 (Method for producing polyurethane foam shoe pad ) 是由 梁振鹏 钟运邦 于 2018-12-04 设计创作，主要内容包括：本发明涉及一种制造PU泡沫鞋垫的方法,其包括以下步骤：(1)将用于形成PU泡沫的原料浇注至模具中,使其反应以获得PU片材,其中模腔的高度为两个成品鞋垫总厚度的约1.0-约1.6倍,优选约1.1-约1.4倍,更优选约1.1-约1.3倍,最优选约1.1-约1.2倍；(2)将PU片材在水平方向上剖成两半以获得两片PU鞋垫材料,其中该材料的一个表面具有开孔,且该材料的另一个表面具有皮层；(3)将织物片附着至步骤(2)中所获得的材料的具有开孔的表面上。通过本发明制造的PU泡沫鞋垫具有低密度和良好回弹性、明亮且有光泽的皮层外观和良好透气性,且制造期间的原料利用率高。本发明克服了模内浇铸鞋垫的缺点如高密度和不良透气性,且可在鞋垫制造期间改善环境保护且满足消费者日益增加的需求。(The invention relates to a method for manufacturing PU foam insoles, which comprises the following steps: (1) pouring the raw materials for forming the PU foam into a mold and allowing them to react to obtain a PU sheet, wherein the height of the mold cavity is about 1.0 to about 1.6 times, preferably about 1.1 to about 1.4 times, more preferably about 1.1 to about 1.3 times, most preferably about 1.1 to about 1.2 times the total thickness of the two finished footbeds; (2) cutting the PU sheet into two halves in the horizontal direction to obtain two pieces of PU insole materials, wherein one surface of the materials is provided with openings, and the other surface of the materials is provided with a skin layer; (3) attaching a piece of fabric to the surface of the material obtained in step (2) having the openings. The PU foam insole manufactured by the invention has low density and good rebound resilience, bright and glossy skin appearance and good air permeability, and the raw material utilization rate during the manufacturing process is high. The present invention overcomes the disadvantages of in-mold cast insoles such as high density and poor air permeability and can improve environmental protection during insole manufacture and meet the increasing demands of consumers.)

1. A method of manufacturing a PU foam insole comprising the steps of:

(1) pouring the raw materials for forming the PU foam into a mold and allowing them to react to obtain a PU sheet, wherein the height of the mold cavity is about 1.0 to about 1.6 times, preferably about 1.1 to about 1.4 times, more preferably about 1.1 to about 1.3 times, and most preferably about 1.1 to about 1.2 times the total thickness of the two finished footbeds;

(2) cutting the PU sheet into two halves in the horizontal direction to obtain two pieces of PU insole materials, wherein one surface of the materials is provided with openings, and the other surface of the materials is provided with a skin layer; and

(3) attaching a piece of fabric to the surface of the material obtained in step (2) having the openings.

2. The process of claim 1, wherein the height of the mold cavity is from about 0.2 to about 8.0cm, preferably from about 0.2 to about 5.0cm, more preferably from about 0.2 to about 3.0cm, even more preferably from about 0.3 to about 2.0 cm.

3. A method as claimed in claim 1 or 2, wherein the mould cavity is in the shape of a cube or cuboid, or the outline of the mould cavity corresponds to the outline or enlarged outline of the insole.

4. A process according to any one of claims 1 to 3, wherein the mould cavity has a length of from about 5 to about 115cm, preferably from about 15 to about 36cm, more preferably from about 18 to about 34cm, most preferably from about 20 to about 33 cm; the width of the mold cavity is from about 5 to about 115cm, preferably from about 11 to about 29cm, more preferably from about 14 to about 26cm, and most preferably from about 16 to about 25 cm.

5. The process of any of claims 1-4, wherein the raw materials for forming the PU foam are maintained at a temperature of 20-48 ℃ prior to casting into the mold.

6. The method according to any one of claims 1 to 5, wherein in step (1), the temperature of the mold is set to 25 to 60 ℃.

7. The process of any of claims 1 to 6, wherein in step (1), the reaction time is from about 2 to about 30 minutes, preferably from about 3 to about 10 minutes, more preferably from about 4 to about 8 minutes, most preferably from about 4 to about 6 minutes.

8. The process of any one of claims 1 to 7, wherein in step (2), after demolding, the PU sheet is left to stand at room temperature or a temperature of about 30 to about 50 ℃ for about 6 to about 24 hours, followed by splitting into two halves.

9. The process as claimed in any of claims 1 to 8, wherein the raw materials for forming the PU foam comprise an A-component and a B-component, wherein component A comprises at least one polyol and a blowing agent and optionally further additives; component B comprises at least one polyisocyanate.

10. The process of claim 9 wherein the feed has an NCO index of about 98 to about 125, more preferably about 102 to about 118, and most preferably about 105 to about 115.

11. The process of claim 9 or 10, wherein the polyol comprises:

(1) polyol A: a propylene oxide and/or ethylene oxide capped polyol having a functionality of from about 2 to about 8, an ethylene oxide content of no more than 40 weight percent, and a hydroxyl number of from about 14 to about 150mg KOH/g; and

(2) polyol B: a styrene and acrylonitrile grafted polyether polyol having a functionality of about 3, a solids content of no more than 45% and a hydroxyl number of from about 20 to about 40mg KOH/g.

12. The method of any of claims 9-11, wherein the polyisocyanate is a prepolymer obtained by reacting diphenylmethane-4, 4 '-diisocyanate (MDI), diphenylmethane-2, 4' -diisocyanate and/or carbodiimide modified diphenylmethane diisocyanate with a polyol, wherein the prepolymer has an NCO content of about 16 to about 33.5 weight percent, based on the total weight of the prepolymer.

13. The process of claim 9 wherein the optional additional additives comprise polyol C: a propylene oxide and/or ethylene oxide capped polyol having a functionality of from about 2 to about 4, an ethylene oxide content of greater than 30 weight percent, and a hydroxyl number of from about 20 to about 70mg KOH/g.

14. The method of claim 1, comprising the steps of:

i) premixing a polyol component with a chain extender, a catalyst, a blowing agent, and other additives to obtain a premixed polyol composition;

ii) casting the premix polyol composition and the isocyanate component into a mold by a casting machine; reacting it to obtain a PU sheet;

iii) after leaving the PU sheet at room temperature for about 6 to about 24 hours, cutting the PU sheet in half in the horizontal direction to obtain two pieces of PU insole material, wherein each piece has two surfaces, one of which has openings and the other of which has a skin layer;

iv) attaching a piece of fabric to the surface with openings of the material obtained in iv) in step; and v) hot-pressing the sheet obtained in step v) and subsequently cutting it into insoles of the desired size.

15. An insole obtainable by a method according to any one of claims 1 to 14.

Technical Field

The invention relates to a method for producing Polyurethane (PU) foam insoles and insoles obtainable by said method.

Background

PU has been increasingly used as a shoe material. Nowadays, PU insoles have been widely used in medium and high-grade sports shoes, casual shoes and other fields because of their ease of processing, good elasticity, excellent cushioning properties, good wearing comfort and resistance to deformation, etc. There are currently two types of PU insoles: foamed breathable insoles and in-molded (in-molded) insoles.

Foamed breathable insoles are generally made from: the polyol composition is mixed with the polyisocyanate component, then foamed and aged in a large-size mold to form a long or slabstock foam, then aged, then cut into foam pieces having a desired thickness, then the fabric pieces are attached to the foam pieces with an adhesive, and finally hot-pressed and cut into insoles having different sizes.

In-mold casting insoles are generally made ofManufacturing: the polyol composition is mixed with the polyisocyanate component and then cast into a mold wherein a piece of fabric has been attached to the top half of the mold, then the mold is closed, foamed and aged for 5-6 minutes, after foaming, the PU is attached to the fabric that will be in contact with the sole of the foot, then demolded and cut into insoles. Insoles made by in-mould casting have a relatively high density (typically 0.32 + -0.02 g/cm)³). In addition, the shoe insole manufactured by the in-mold casting method has poor air permeability because a dense skin layer exists on both the upper and lower surfaces thereof.

The foamed air-permeable insole is different from the insole cast in the mould in that:

(1) on the one hand, the size of the mould for foaming breathable insoles is relatively large (for example 200cm long × 110cm wide × 100cm deep), and the resulting PU foam is generally rectangular and needs to be cut into sheets having the thickness of the insole and further processed in order to obtain foamed breathable insoles;

(2) the total foaming time for foaming the breathable insole is relatively long and multiple pairs of insoles can be manufactured in one cycle; whereas the total foaming time for in-mold casting of insoles is relatively short, only one pair of insoles can be made in one cycle;

(3) the aging time for foamed breathable insoles is relatively long, typically about 30 to about 90 minutes, and post-aging must be carried out, typically for about 5 hours or more; whereas in-mold cast insoles have relatively short aging times, typically from about 5 to about 6 minutes, and typically do not require post-aging;

(4) the process steps for making foamed breathable insoles are numerous, such as post-aging, splitting, etc.; the process steps for manufacturing the in-mold casting insole are fewer, and the step of splitting is not required;

(5) during the manufacture of foamed breathable insoles, this results in a great waste of material and a low utilization rate (typically about 50 to about 65%) since on the one hand the foam heads and foam tails and the upper and lower skin layers of the foam are not available and on the other hand a large amount of waste material is generated during the final cutting step, all of which are not recyclable. In contrast, in-mold cast insoles are directly formed and only require cutting of flash, thus resulting in high utilization;

(6) the density of the foamed breathable insole is relatively low and there is a density gradient distribution in the foam, where the density at the top is high and the density at the bottom is low, the overall density being typically 0.13 + -0.01 g/cm³(ii) a Whereas the density of the in-mold cast insole is relatively high, typically 0.32 + -0.02 g/cm³；

(7) Foamed breathable insoles have no skin and therefore have a poor appearance; whereas in-mold cast insoles have a skin layer and therefore a good appearance;

(8) the foamed breathable insoles have poor resilience; the rebound resilience of the insole cast in the mould is better; and

(9) the foamed breathable insole is breathable and is mould-proof; whereas in-mold cast insoles are not air-permeable and therefore not mould proof.

The prior art discloses various methods for making foamed breathable insoles and in-mold cast insoles.

For example, CN1730554A discloses a method of manufacturing foamed breathable shoe insoles, wherein polyether polyol, polymer polyol, pigment paste, catalyst, foaming agent, pore former, silicon surfactant, ethylene glycol, antimicrobial agent are mixed in a container, and the resulting mixture (abbreviated as white material) is maintained at a constant temperature of 15-30 ℃; at the same time, the MDI prepolymer is also kept at a constant temperature of 15-30 ℃, and the rubber powder is added to the MDI prepolymer (abbreviated as black material); then stirring the white material and the black material in a ratio of 100:50 to 100:120 at a speed of 200-3500 rpm; after stirring for 10-25 seconds, the mixture is rapidly poured into a mold having a constant temperature of 35-50 ℃; subsequently closing the mold; aging the material for 30-90 minutes; the shaped article is subsequently demolded and sectioned to obtain the finished product.

CN101864164A discloses a method for manufacturing foamed air-permeable shoe insoles, characterized by comprising the steps of (1) placing a polyol composition and isocyanate in thermostatic chambers at a temperature of 7-35 ℃ for 5-8 hours, respectively, (2) coating a mold with a release agent and maintaining the mold at a temperature of 45-48 ℃, (3) pouring the polyol composition into a stirring tank, adding a catalyst, a surfactant, an antibacterial agent, a foaming agent, a pigment slurry and a pore forming agent, stirring together for 120-150 seconds, followed by adding isocyanate and stirring for 10-20 seconds, (4) pouring the stirred mixture into the mold within 5 seconds, blowing off bubbles caused by the pouring by an air gun, followed by closing and locking the mold, (5) after 35-45 minutes, opening the mold and removing the molded article to cut it into sheets having a desired size, the size of the mold used in this application is at least 200cm long by 36110 cm wide by × cm deep, which is sufficiently large that the raw materials can be sufficiently mixed in the mold, thereby obtaining a light foamed air-permeable shoe insole and a light aging.

CN101585901A discloses a PU foam and a method for producing the same, which comprises adding polyether polyol, chain extender, blowing agent, catalyst and foam stabilizer in specific proportions to a container and thoroughly mixing, and then maintaining the resulting material at about room temperature; pouring a prepolymer of diphenylmethane diisocyanate maintained at the same temperature into a container and rapidly stirring at a high speed of 1000-10000rpm for 8-16 seconds, followed by rapidly pouring into a foaming tank; controlling the foaming time to be 18-28 seconds; about 150-300 seconds after the free foaming to the highest point, placing the material in an oven to age for 4-72 hours; the foam is then cut for subsequent processing steps. Foamed breathable insoles are obtained in this application. There is a large amount of waste material and thus the material utilization is low. Furthermore, although the air permeability of the obtained foamed breathable insole is good, the appearance is poor because no skin layer is present.

Description of the invention

The invention provides a method for manufacturing PU foam insoles. In the method of the present invention, a mold having a flat inner cavity, i.e., a mold cavity having a height of about 1.0 to about 1.6 times the total thickness of the two finished shoe insoles, is used, thereby obtaining a PU foamed sheet. The foamed sheet was cut in half in the horizontal direction (in other words, along a plane defined by the length and width), thereby obtaining a PU material having a solid skin layer on one surface and open pores on the other surface. Subsequently, a piece of fabric is attached to the surface with the openings, followed by hot pressing and other process steps, and finally an insole with good breathability and resilience is obtained. The porous surface with the attached fabric, which has high porosity and good air permeability, will be in direct contact with the sole of the foot. The surface with the compact skin layer is in contact with the shoe, which has an intact skin layer obtained by foaming and a good appearance. Furthermore, due to the dense skin layer, good resilience can be obtained at low foam density.

The PU foam insole manufactured by the invention has low density, good rebound resilience, bright and glossy skin appearance, good air permeability and relatively high raw material utilization rate. The present invention overcomes the disadvantages of in-mold cast insoles such as high density and poor air permeability, improves environmental friendliness and meets the increasing demands of consumers.

In particular, the present invention relates to a method of manufacturing a PU foam insole, comprising the steps of:

(1) pouring raw materials for forming PU foam into a mold, and reacting to obtain a PU sheet, wherein the height of the mold cavity is about 1.0 to about 1.6 times of the total thickness of the two finished insoles;

(2) cutting the PU sheet into two halves in the horizontal direction to obtain two pieces of PU insole materials, wherein one surface of the materials is provided with openings, and the other surface of the materials is provided with a skin layer; and

(3) attaching a piece of fabric to the surface of the material obtained in step (2) having the openings.

In an embodiment of the present invention, the cavity of the mold may be a flat body having a relatively high width and length and a relatively low height, wherein the height is about 1.0 to about 1.6 times the total thickness of the two finished footbeds. The reason for choosing the height of the mould cavity to be about 1.0 times or more the total thickness of the two finished insoles is that the split sheet may be slightly compressed during subsequent steps such as hot pressing. Therefore, in order to make the thickness of the split sheet material after being subjected to compression correspond to that of the finished insole, it is necessary to make the thickness of the split sheet material equal to or slightly thicker than that of the finished insole, that is, the thickness of the PU insole material formed in the mold is equal to or slightly greater than the total thickness of the two finished insoles. In particular, the height of the mold cavity may be determined according to actual requirements, and is typically from about 1.0 to about 1.6 times, preferably from about 1.1 to about 1.4 times, more preferably from about 1.1 to about 1.3 times, and most preferably from about 1.1 to about 1.2 times the total thickness of the two finished footbeds. For example, the height of the mold cavity may be from about 0.2 to about 8.0cm, preferably from about 0.2 to about 5.0cm, more preferably from about 0.2 to about 3.0cm, and most preferably from about 0.3 to about 2.0 cm.

In another embodiment, the shape of the mold cavity is not limited to a cube or cuboid, or the contour of the mold cavity may also correspond to the contour or enlarged contour of the insole, so that when cutting the foamed sheet into insoles, unnecessary corners do not have to be cut and material is saved.

The mold used in the present invention may be made of various materials commonly used in the art, and is not limited to metal, such as iron, steel, aluminum, or alloys thereof, and may be plastic, such as PP or PE.

The length and width of the mold cavity is not limited to the dimensions used to make one insole, but may be larger than one insole. In the method of the present invention, a sheet having a size corresponding to two insoles or more can be manufactured. In particular, the mold cavity of the present invention may have a length of from about 5 to about 115cm, preferably from about 15 to about 36cm, more preferably from about 18 to about 34cm, and most preferably from about 20 to about 33 cm; the width of the mold cavity may be from about 5 to about 115cm, preferably from about 11 to about 29cm, more preferably from about 14 to about 26cm, and most preferably from about 16 to about 25 cm.

In the process of the present invention, the raw materials for forming the PU foam are maintained at a temperature of about 20 to about 48 ℃ prior to casting into the mold.

In step (1) of the process of the present invention, the temperature of the mold is set to about 25 to about 60 ℃.

In step (1) of the process of the present invention, the reaction time may be from about 2 to about 30 minutes, preferably from about 3 to about 10 minutes, more preferably from about 4 to about 8 minutes, and most preferably from about 4 to about 6 minutes. During the reaction, the material foams and ages.

In step (2) of the process of the present invention, after demolding, the PU sheet is left to stand at room temperature or a temperature of about 30 to about 50 ℃ for about 6 to about 24 hours, and then cut into two halves in the horizontal direction. The thickness of the two halves may be the same or different, preferably the same.

In step (3) of the process of the invention, a fabric is attached to the surface of the material obtained in step (2) having open pores, wherein an adhesive or a TPU (thermoplastic PU) hot melt film can be used. When the TPU hot melt film is used, the TPU hot melt film is first adhered to the fabric, and then the fabric is attached to the surface of the PU sheet having the open pores. During hot pressing, the TPU hot melt film melts and bonds the fabric and PU sheet together.

In step (3) of the process of the present invention, the temperature of the hot pressing is from about 120 to about 180 ℃ and the hot pressing time is from about 1 to about 2.5 minutes.

After the attachment of the fabric, the resulting material is cut to the desired dimensions in order to obtain the finished insole.

The PU foam used in the present invention is prepared by reacting a polyol component with a polyisocyanate component in the presence of a chain extender, a catalyst, a blowing agent, and optionally other additives.

The raw materials for forming the PU foam comprise an A component and a B component, wherein:

component a comprises at least one polyol, a blowing agent and optionally other additives;

component B comprises at least one polyisocyanate.

In the present invention, the NCO index of the feed is from about 98 to about 125, more preferably from about 102 to about 118, and most preferably from about 105 to about 115.

The polyol used in the present invention may be any polyol suitable for preparing PU foam, such as polyether polyol or polyester polyol. However, it has been found that when the following polyols are used in conjunction with the process of the present invention, the resulting insoles have good mechanical properties, including good hardness, tensile strength, tear strength, vertical rebound and compression resistance:

(1) polyol A: a propylene oxide and/or ethylene oxide capped polyol having a functionality of from about 2 to about 8 and a hydroxyl number of from about 14 to about 150mg KOH/g. Polyol a has an ethylene oxide content of no more than 40% by weight. The polyol a can be obtained by polymerizing propylene oxide and/or ethylene oxide using a polyol such as glycerin, trimethylolpropane or pentaerythritol as a starter; and

(2) polyol B: a styrene and acrylonitrile grafted polyether polyol having a functionality of about 3, a solids content of no more than 45% and a hydroxyl number of from about 20 to about 40mg KOH/g.

The polyisocyanate used in the present invention may be any polyisocyanate suitable for the preparation of PU foams. However, it has been found that when a polyisocyanate prepolymer obtained by reacting diphenylmethane-4, 4 '-diisocyanate (MDI), diphenylmethane-2, 4' -diisocyanate and/or a carbodiimide modified diphenylmethane diisocyanate with a polyol is used in conjunction with the process of the present invention, the resulting insole has good mechanical properties, including good hardness, tensile strength, tear strength, vertical resilience and compression resistance. The prepolymer has an NCO content of about 16 to about 33.5 weight percent, based on the total weight of the prepolymer. Here, the polyol may be the polyol described above for polyol a.

The blowing agent used in the present invention may be a chemical blowing agent, such as water and/or formic acid. Physical blowing agents may also be used in the present invention. The physical blowing agent can be chosen, for example, from propane, n-butane, isobutane, cyclobutane, n-pentane, isopentane, cyclopentane, cyclohexane, dimethyl ether, methylethyl ether, methylbutyl ether, methyl formate, acetone and fluorinated alkanes that can decompose in the troposphere and therefore do not destroy the ozone layer, such as trifluoromethane, difluoromethane, 1,1,1,3, 3-pentafluorobutane, 1,1,1,3, 3-pentafluoropropane, 1,1,1, 2-tetrafluoroethane, difluoroethane and heptafluoropropane. Blowing agents are generally used in amounts of about 0.1 to about 15 wt.%, preferably about 0.1 to about 10 wt.%, particularly preferably about 0.1 to about 5 wt.%, based on the total weight of the reaction mass.

Component a of the present invention may also include optional additional additives such as cell openers, chain extenders and/or crosslinkers, foam stabilizers, catalysts, antimicrobial agents, and the like.

Cell openers are typically surfactants comprising a hydrophobic moiety and a hydrophilic moiety. The cell opener can lower the surface tension of the foam and promote the breaking of the foam. Commonly used cell openers can be liquid paraffin, polybutadiene, methyl polysiloxane, and polyether polyols. Preferably, the polyether polyol can be a propylene oxide and/or ethylene oxide capped polyol having a functionality of from about 2 to about 4, an ethylene oxide content of greater than 30 weight percent, and a hydroxyl number of from about 20 to about 70mg KOH/g.

As chain extenders and/or crosslinkers, difunctional or trifunctional amines and alcohols, in particular diols, triols or both, can be used. Such bifunctional compounds are called chain extenders and trifunctional or higher functional compounds are called crosslinkers. By way of example, mention may be made of ethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 2-pentanediol, 1, 3-pentanediol, 1, 10-decanediol, 1, 2-dihydroxycyclohexane, 1, 3-dihydroxycyclohexane, 1, 4-dihydroxycyclohexane, diethylene glycol and triethylene glycol, dipropylene glycol and tripropylene glycol, 1, 4-butanediol, 1, 6-hexanediol and bis (2-hydroxyethyl) hydroquinone; triols, such as 1,2, 4-trihydroxycyclohexane, 1,3, 5-trihydroxycyclohexane, glycerol and trimethylolpropane.

Foam stabilizers are substances which promote the formation of a regular cell structure during foaming. Examples are: silicon-containing foam stabilizers, for example siloxane-oxyalkylene copolymers and other organopolysiloxanes. The following alkoxylation products can also be used: fatty alcohols, oxo alcohols, fatty amines, alkyl phenols, dialkyl phenols, alkyl cresols, alkyl resorcinols, naphthols, alkyl naphthols, naphthylamines, anilines, alkyl anilines, toluidines, bisphenol a, alkylated bisphenol a, polyvinyl alcohols, and alkoxylation products of the condensation products of: formaldehyde and an alkyl phenol, formaldehyde and a dialkyl phenol, formaldehyde and an alkyl cresol, formaldehyde and an alkyl resorcinol, formaldehyde and an aniline, formaldehyde and a toluidine, formaldehyde and a naphthol, formaldehyde and an alkyl naphthol, and formaldehyde and bisphenol a, or a mixture of two or more of these foam stabilizers. The foam stabilizers are preferably used in amounts of from about 0.5 to about 4.0% by weight, particularly preferably from about 1.0 to about 3.0% by weight, based on the total weight of the reaction mass.

As catalyst, all compounds capable of promoting the reaction between isocyanate and water and/or the reaction between isocyanate and polyol can be used. These catalysts are known and are described, for example, in "Kunststoffhandbuch, volume 7, Polyurethane", Carl Hanser Press, 3 rd edition, 1993, chapter 3.4.1. These include amine-based catalysts and organometallic compound-based catalysts, preferably tertiary amine catalysts. The catalyst used may be, for example, bis (2-dimethylaminoethyl) ether, N, N, N, N, N-pentamethyldiethylenetriamine, N, N, N-triethylaminoethoxyethanol, dimethylcyclohexylamine, dimethylbenzylamine, triethylamine, triethylenediamine, pentamethyldipropylenetriamine, dimethylethanolamine, N-methylimidazole, N-ethylimidazole, tetramethylhexamethylenediamine, tris (dimethylaminopropyl) hexahydrotriazine, dimethylaminopropylamine, N-ethylmorpholine, diazabicycloundecene or diazabicyclononene. The catalyst is preferably used in an amount of about 0.1 to about 10.0 wt%, preferably about 0.5 to about 5.0 wt%, more preferably about 1.0 to about 3.0 wt%, based on the total weight of the reaction mass.

The antimicrobial agent may be those commonly known to those skilled in the art for use in insoles, such as Zinc Omadine 48% FPS Ind available from Arch Chemical (China) limited.

In the process of the present invention, the polyol may be premixed with the blowing agent and optionally other additives (e.g., cell opener, chain extender, catalyst, etc.) to obtain a premixed component a; then respectively adding the component B into one hopper of a low-pressure casting machine, and adding the premixed component A into the other hopper of the low-pressure casting machine; then pouring the component B and the premixed component A into a mould through a stirring head of a low-pressure pouring machine; the mold is closed and the reaction subsequently takes place.

In particular, the method for manufacturing the PU foam insole of the present invention comprises the steps of:

i) premixing the polyol component with a blowing agent and optionally other additives (e.g., cell opener, chain extender, catalyst) to obtain a premixed polyol composition;

ii) casting the premix polyol composition and the isocyanate component into a mold by a casting machine; reacting it to obtain a PU sheet;

iii) after allowing the PU sheet to stand at room temperature for about 6 to about 24 hours, splitting the PU sheet in half in the horizontal direction to obtain two pieces of PU insole material, wherein each piece has two surfaces, one of which has openings and the other of which has a skin layer;

iv) attaching a piece of fabric to the surface with openings of the material obtained in iv) in step; and

v) hot pressing the sheet obtained in step v) and subsequently cutting it into insoles of the desired size.

In this method, the casting machine may be a low pressure casting machine. The premix polyol composition obtained in step i) is fed separately into one hopper of a low-pressure casting machine and the isocyanate component is fed into the other hopper of the low-pressure casting machine. The premixed polyol composition and isocyanate component are then passed through and mixed in the stirring head of a low pressure casting machine and then cast into a mold.

The invention also provides formulation designs compatible with the methods of the invention. By combining the selection of prepolymers of polyether polyol and diphenylmethane diisocyanate and the use of corresponding additives with the method of the present invention, the resulting cast breathable insole has high physical properties, good resilience, smooth skin, good air and perspiration absorption, good cushioning effect and light weight; in addition, the utilization rate of the material is high.

Typical physical properties of the insoles obtained by the invention are as follows:

TABLE 1

Item	Performance of	Test standard
			Density of	145-155kg/m3	DIN 53420(＝ISO 845)
Hardness of	25-35Asker C	ASTM D2240
			Tensile strength	>＝5.5kg/cm2	ASTM D412
Tear strength	>＝2.1N/mm	DIN ISO 34-1 (method B)
			Vertical resilience	>＝38％	DIN 53512
Resistance to compression	<＝15％	ASTM D395:2003

Drawings

FIG. 1 is a schematic diagram showing a part of the method of the present invention.

The invention is further illustrated by the following examples.

Examples