Process for producing a polyurethane foam insole

Abstract

Described herein is a method for producing a PU foam insole, including the following steps of: (1) pouring the raw materials used to form a PU foam into a mould, reacting to obtain a PU sheet, where the height of the mould cavity is from about 1.0 to about 1.6 times of the total thickness of two finished insoles; (2) splitting the PU sheet into two halves in the horizontal direction to obtain two pieces of PU insole material, where one surface of the material has open pores, and the other surface of the material has a skin; and (3) attaching a piece of fabric onto the surface having open pores of the material obtained in step (2). Also described herein is a PU foam insole produced by the method.

Claims

1. A process for producing a polyurethane (PU) foam insole, comprising the following steps of: (1) pouring the raw materials used to form a PU foam into a mould, reacting to obtain a PU sheet, wherein the height of the mould cavity is from about 1.0 to about 1.6 times of the total thickness of two finished insoles; (2) splitting the PU sheet into two halves in the horizontal direction to obtain two pieces of PU insole material, wherein one surface of the material has open pores, and the other surface of the material has a skin; and (3) attaching a piece of fabric onto the surface having open pores of the material obtained in step (2).

2. The process according to claim 1, wherein the height of the mould cavity is from about 0.2 to 8.0 cm.

3. The process according to claim 1, wherein the shape of the mould cavity is a cube or a rectangle, or the profile of the mould cavity corresponds to the profile or the enlarged profile of the insole.

4. The process according to claim 1, wherein the length of the mould cavity is from about 5 to about 115 cm.

5. The process according to claim 1, wherein the raw materials for forming the PU foam are maintained at a temperature of 20-48° C. prior to pouring into the mould.

6. The process according to claim 1, wherein in step (1), the temperature of the mould is set to 25-60° C.

7. The process according to claim 1, wherein in step (1), the reacting time is from about 2 to about 30 minutes.

8. The process according to claim 1, wherein in step (2), after demoulding, the PU sheet is allowed to stand under room temperature or a temperature from about 30 to about 50° C. for about 6 to about 24 hours, then split into two halves.

9. The process according to claim 1, wherein the raw materials for forming the PU foam include A and B components, wherein Component A comprises at least one polyol and a blowing agent and optional other additives; and Component B comprises at least one polyisocyanate.

10. The process according to claim 9, wherein the NCO index of the raw materials is from about 98 to about 125.

11. The process according to claim 9, wherein the polyol comprises (1) Polyol A: a propylene oxide and/or ethylene oxide-terminated polyol having a functionality of from about 2 to about 8, an ethylene oxide content of not more than 40% by weight and a hydroxyl value of from about 14 to about 150 mg KOH/g; and (2) Polyol B: a styrene and acrylonitrile grafted polyether polyol having a functionality of about 3, a solid content of no more than 45%, and a hydroxyl value of from about 20 to about 40 mg KOH/g.

12. The process according to claim 9, wherein the polyisocyanates is a prepolymer obtained by reacting diphenylmethane-4,4′-diisocyanate (MDI), diphenylmethane-2,4′-diisocyanate and/or a carbodiimide-modified diphenylmethane diisocyanate with a polyol, wherein the NCO content of the prepolymer is from about 16 to about 33.5% by weight, based on the total weight of the prepolymer.

13. The process according to claim 9, wherein the optional other additives comprise Polyol C as a cell opener: a propylene oxide and/or ethylene oxide-terminated polyol having a functionality of from about 2 to about 4, an ethylene oxide content of more than 30% by weight and a hydroxyl value of from about 20 to about 70 mg KOH/g.

14. A process for producing a polyurethane (PU) foam insole, comprising the following 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) pouring the premixed polyol composition and the isocyanate component into a mould by means of a pouring machine; reacting to obtain PU sheet; iii) after allowing the PU sheet to stand under room temperature for about 6 to about 24 hours, splitting the PU sheet into two halves in the horizontal direction to obtain two pieces of PU insole material, wherein each piece has two surfaces, with one surface having open pores, and the other surface having a skin; iv) attaching a piece of fabric onto the surface of the material obtained in step iii) having open pores; and v) hot pressing the sheet obtained in step iv) and then cutting into the insole having the desired size.

15. The process according to claim 1, wherein the height of the mould cavity is from about 1.1 to about 1.2 times of the total thickness of two finished insoles.

16. The process according to claim 1, wherein the height of the mould cavity is from about 0.3 to about 2.0 cm.

17. The process according to claim 1, wherein the length of the mould cavity is from about 16 to about 25 cm.

18. The process according to claim 1, wherein in step (1), the reacting time is from about 4 to about 6 minutes.

19. The process according to claim 9, wherein the NCO index of the raw materials is from about 105 to about 115.

Description

DESCRIPTION OF FIGURES

(1) FIG. 1 is a schematic drawing showing a part of the process of the present invention.

(2) The invention is further illustrated by the following examples.

Examples

(3) The raw materials used in the examples are as follows:

(4) Polyol-A: a polyether polyol having a relative molecular weight of 6000, a functionality of 3 and a hydroxyl value of about 28 mg KOH/g, commercially available under TEP-3600 from Sinopec Tianjin Petrochemical Company;

(5) Polyol-B: styrene and acrylonitrile grafted polyether polyol having a solid content of about 30%, a hydroxyl value of about 25 mg KOH/g, commercially available under TPOP36/28 from Sinopec Tianjin Petrochemical Company;

(6) Polyol-C: a polyether polyol having a relative molecular weight of 3500, a functionality of 3 and a hydroxyl value of about 42 mg KOH/g, commercially available under Lupranol 2048 from BASF Company; this polyol is EO content rich and act as a cell opener.

(7) Ethylene glycol (EG): chain extender;

(8) 1,4-Butanediol (1,4-BDO): chain extender;

(9) Distilled water (H.sub.2O): foaming agent;

(10) Catalyst A: aminic gel type catalyst; commercially available under Dabco EG from Air Product;

(11) Catalyst B: aminic gel type catalyst, triethanolamine;

(12) Catalyst C: aminic foaming catalyst; commercially available under A1 from Air Product;

(13) Foam Stabilizer: DC 2585, available from Air Products;

(14) Isocyanate prepolymer components:

(15) Prepolymer 1: NCO %=20%, obtained by the reaction of diphenylmethane-4,4′-diisocyanate and carbodiimide-modified diphenylmethane diisocyanate with a polyether polyol, wherein the polyether polyol has 13% by weight of EO (terminated), a number average molecular weight of about 4800 and a functionality of 3; Elastopan CS9500C-B, available from BASF Polyurethanes (China) Co., Ltd.

(16) Prepolymer 2: NCO %=24%, obtained from the reaction of diphenylmethane-2,4′-diisocyanate (2,4′-MDI), diphenylmethane-4,4′-diisocyanate (4,4′-MDI), carbodiimide-modified diphenylmethane diisocyanate (LUPRANATE MM103C) and polymeric MDI (LUPRANATE M20S) with a polyether polyol, wherein the polyether polyol has 13% by weight of EO (capped), a number average molecular weight of about 4800 and a functionality of 3; the basic recipes for preparing Prepolymer 2 is: 4,4MDI 30%+2,4MDI 5%+LUPRANATE MM103C 38.5%+LUPRANATE M20S 5%+Polyol 21.5% react at 75° C. for 1.5 hours.

(17) According to the following Table 2, the polyol component was premixed with additives such as a chain extender, a catalyst, a foaming agent and the like to obtain a premixed polyol composition. The premixed polyol composition was fed into one hopper of a low-pressure pouring machine (N-series 2-component pouring machine, from Taiwan Green Industry Co., Ltd.) and the isocyanate prepolymer component was fed into the other hoppers of the low-pressure pouring machine, and preheated to 40° C., respectively; and the two components we through the stirring head of the low-pressure pouring machine into a mould preheated Then the mould was closed, and the raw materials were allowed to foam and age for 6 minutes. Subsequently, the mould was opened and the PU sheet was removed. Before the next process step, the PU sheet was allowed to stand under room temperature for 24 hours.

(18) The size of the mould used in Comparative Example 1 was an insole mould (i.e., its shape and size exactly correspond to those of one insole), and a piece of fabric was placed in the upper half mould. The size of the mould cavity used in Comparative Example 2 was 35 cm*25 cm*10 cm, and the size of the mould cavity used in Example 1 was 35 cm*25*1.5 cm.

(19) For Comparative Example 1, after the formed insole was removed from the mould, the flash was removed to obtain the finished insole. For Comparative Example 2, after removing the PU foam from the mould, the upper and lower skin layers were removed, and cut into an insole material having a thickness of 0.7 cm, and then a piece of fabric was bonded onto each of the upper and lower surfaces of the insole material respectively with an adhesive (7710 water-based glue, commercially available from Dongguan Glober Glue Corporation Limited), hot pressed in a hot pressing machine (commercially available from Dongguan Chenghao Machinery co., Ltd.) under 170° C. for 2 minutes, then the flash was removed to obtain the finished insole. For Example 1, after the PU foam was removed from the mould, it was split into two halves along the horizontal plane, and a piece of fabric was bonded onto the surface having open pores with an adhesive (7710 water-based glue, commercially available from Dongguan Glober Glue Corporation Limited), and then hot pressed in a hot pressing machine (commercially available from Dongguan Chenghao Machinery co., Ltd.) under 170° C. for 2 minutes, subsequently the flash was removed to obtain the finished insole.

(20) Example 1 is based on the inventive process, whereas Comparative Example 1 is based on the in-mould casting insole production process from the prior art, and Comparative Example 2 is based on the foamed breathable insole production process from the prior art. Table 2 below shows the composition and weight percentages of the raw materials used.

(21) TABLE-US-00002 TABLE 2 Weight parts Polyol Comparative Comparative component Example 1 Example 2 Example 1 Example 2 Polyol A 75.78 70.58 74.98 68.98 Polyol B 20 20 20 20 Polyol C 6 EG 0.5 5 0.5 0.5 1,4-BDO 0.5 0.5 0.5 0.5 Catalyst A 1 1 1 1 Catalyst B 1 1 1 1 Catalyst C 0.12 0.12 0.12 0.12 DC 2585 0.2 0.2 0.2 0.2 Distilled 0.9 1.6 1.7 1.7 water(H.sub.2O) Isocyanate Weight parts prepolymer component Prepolymer 1 100 Prepolymer 2 100 100 100 NCO value 20% 24% 24% 24 NCO index 105 112 112 112

(22) Table 3 below shows the basic physical properties of the foamed insole materials. The appearance is visually evaluated, wherein “good” indicates that the surface is smooth, and “bad” indicates that the surface is not smooth. The air permeability is evaluated by a panel and given a rating from 1 to 3, wherein 1 indicates that the air permeability is poor, that is, when blowing air through the insole material, the air cannot pass through the material at all; and 3 indicates that the air permeability is excellent, that is, when blowing air through the insole material, the air can pass through the material unimpededly.

(23) TABLE-US-00003 TABLE 3 Comparative Comparative Example 1 Example 2 Example 1 Example 2 (in-mould (foamed (according to (according to casting breathable the present the present insole) insole) invention) invention) Test Standard Density, 0.320 0.130 0.152 0.150 DIN EN ISO 845 g/cm.sup.3 Hardness, 29 ± 1 26 ± 1 27 ± 1 26 ± 1 ASTM D2240 Asker C Tensile 6.2 5.7 5.6 5.8 DIN strength, 53504 kg/cm.sup.2 Tear 2.6 2.4 2.3 2.4 DIN ISO 34-1 strength, (method B) kg/cm Compression 10 14 14 13 ASTM D395 strength, % Vertical 39 ± 1 26 ± 1 39 ± 1 39 ± 1 ASTM D2632 resilience, % Air 1 3 2 3 permeablity Appearance Good Bad Good Good

(24) It can be seen that the skin of the insole prepared by the process of the present invention is smooth, at the same time, the insole has good air permeability, a low density and a good resilience. Moreover, the utilization ratio of materials has been improved over the breathable foam production process, which could amount to 85% or above.