Preparation process of a colored supercritical foamed shoe material

Abstract

This application relates to the technical field of shoe materials, and specifically provides a preparation process for a colored supercritical foamed shoe material, which includes the following steps: S1. Prepare an inorganic filler to adsorb a cationic pigment to obtain a dispersed pigment; S2. Mix the dispersed pigment, linear-structured polyurethane, and TPU obtained in step S1 evenly and form them to obtain a preformed shoe material; S3. Perform supercritical foaming on the preformed shoe material obtained in step S2 to obtain the product. The preparation process of the colored supercritical foamed shoe material in this application can improve the dispersibility and dispersion stability of the pigment in the foamed shoe material, and solves the problems of difficult dyeing, uneven dyeing, and instability of the supercritical foamed shoe material.

Description

Technical Field

[0001] This application relates to the technical field of shoe materials, and specifically, to a preparation process of a colored supercritical foamed shoe material. Background Art

[0002] The shoe materials prepared by the supercritical foaming technology have the characteristics of good resilience and low density, and have been widely used in sports shoes. Due to technological reasons, currently, the supercritical foamed shoe materials are mainly in their original color, that is, white in visual appearance. Dyeing the supercritical foamed shoe materials can improve the diversity of product design and meet the pursuit of consumers for fashion, individuality, etc. In the prior art, several supercritical colored foamed shoe material technologies have been developed. Taking the TPU foamed shoe material as an example, for instance, methods such as pre - mixing pigments with TPU materials to form particles and then performing supercritical foaming, adding pigments to polyols to prepare TPU and then performing supercritical foaming, mixing pigments with PU prepolymers and then mixing with TPU for supercritical foaming, etc. However, the above - mentioned methods mainly have problems such as poor and uneven pigment dispersion, unstable pigments, and easy migration. Summary of the Invention

[0003] In order to solve the above - mentioned technical problems in the prior art, this application provides a preparation process of a colored supercritical foamed shoe material.

[0004] This application adopts the following technical solutions:

[0005] A preparation process of a colored supercritical foamed shoe material, comprising the following steps:

[0006] S1. Prepare inorganic fillers to adsorb cationic pigments to obtain dispersed pigments;

[0007] S2. Mix the dispersed pigments, linear - structured polyurethane, and TPU obtained in step S1 evenly and form them to obtain a pre - formed shoe material; S3. Perform supercritical foaming on the pre - formed shoe material obtained in step S2 to obtain the colored supercritical foamed shoe material.

[0008] Preferably, the surface of the inorganic filler in step S1 is electronegative, and the average particle size of the inorganic filler does not exceed 5 μm.

[0009] Preferably, the cationic pigments in step S1 are selected from one or more of cationic red GTL, cationic yellow X - 6G, cationic fluorescent yellow X - 10GFF, cationic orange 2G, cationic blue X - GRRL, rhodamine 123, and cationic black RL.

[0010] Preferably, the preparation method of the dispersed pigments in step S1 is: disperse the inorganic filler in water, add the cationic pigments, disperse evenly, filter, and dry the filtered solid to obtain the product.

[0011] More preferably, the weight ratio of the inorganic filler, the water and the cationic pigment is 1:1-100:0.01-1.

[0012] Preferably, the weight ratio of the dispersed pigment, the linear-structured polyurethane and the TPU in step S2 is 0.5-5:0.2-2:100.

[0013] Preferably, the linear-structured polyurethane in step S2 is prepared by reacting a diol raw material with a diisocyanate in a molar ratio of 1:0.9-1;

[0014] The diol raw material is composed of a first polymer diol, a second polymer diol and a chain extender in a weight ratio of 1:0.5-2:0.02-0.1;

[0015] The average molecular weight of the first polymer diol is 5000-10000;

[0016] The average molecular weight of the second polymer diol is 200-2000.

[0017] More preferably, the first polymer diol and the second polymer diol are each independently selected from one or more combinations of polyether diols and polyester diols.

[0018] More preferably, the chain extender is selected from one or more combinations of ethylene glycol, 1,4-butanediol, 1,3-propanediol, 2,2-dimethylolbutyric acid, tartaric acid and 2,2-bis(hydroxymethyl)propionic acid.

[0019] Further preferably, the molar proportion of one or more combinations of 2,2-dimethylolbutyric acid, tartaric acid and 2,2-bis(hydroxymethyl)propionic acid in the chain extender is 30-100%.

[0020] In summary, the present application has the following beneficial effects:

[0021] 1. The present application uses an inorganic filler as the carrier of the cationic pigment, and utilizes the electrostatic adsorption between the electronegativity of the inorganic filler and the cationic pigment to improve the dispersibility of the cationic pigment and reduce agglomeration.

[0022] 2. The present application further uses a polymer diol with a relatively large molecular weight to prepare a linear-structured polyurethane, which not only has good compatibility with TPU, but also has a good coating effect on the pigment due to the large molecular weight polymer diol segments, and can further improve the dispersibility of the pigment in TPU.

[0023] 3. The present application further introduces carboxyl groups into the linear-structured polyurethane, and the electronegative carboxyl groups can form electrostatic adsorption with the cationic pigment, further improving the dispersibility and dispersion stability of the pigment in TPU. Detailed implementation manners

[0024] In order to make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below.

[0025] Throughout this specification, unless otherwise specifically stated, the terms used herein should be understood as having the meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as the general understanding of those skilled in the art to which the present invention pertains. In case of any conflict, this specification shall prevail.

[0026] The present application provides a preparation process for a colored supercritical foamed shoe material, which includes the following steps:

[0027] S1. Prepare an inorganic filler to adsorb a cationic pigment to obtain a dispersed pigment;

[0028] S2. Mix the dispersed pigment, linear-structured polyurethane and TPU obtained in step S1 evenly and form them to obtain a preformed shoe material; S3. Subject the preformed shoe material obtained in step S2 to supercritical foaming to obtain a colored supercritical foamed shoe material.

[0029] The specific operation of the above step S2 may be: Mix the dispersed pigment, linear-structured polyurethane and TPU, add them to a twin-screw extruder, and extrude, inject and form at 210-235 °C to obtain a preformed shoe material.

[0030] The specific process of the supercritical foaming in the above step S3 may be: Place the preformed shoe material in an autoclave and seal it, and saturate the preformed shoe material with a supercritical fluid (such as supercritical CO2, supercritical N2, etc., with a pressure of 15-30 MPa) (temperature 50-90 °C, time 2-5 h), relieve the pressure to obtain a swollen shoe material; Take out the swollen shoe material and place it in a constant temperature device at 80-120 °C for 15-30 minutes to obtain a colored supercritical foamed shoe material.

[0031] In a preferred embodiment of the present application, in step S1, the surface of the inorganic filler is electronegative, and the average particle size of the inorganic filler does not exceed 5 μm. Generally, the surface of unmodified inorganic fillers has active groups such as hydroxyl groups and carboxyl groups, so the surface shows electronegativity. Alternatively, the unmodified inorganic filler can be further treated in an alkali solution, which can be an aqueous solution of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, etc. For example, a method for treating an inorganic filler with an alkali solution is as follows: Add 1-10 parts by weight of the inorganic filler to 100 parts by weight of a sodium hydroxide solution with a concentration of 1-10 wt%, stir at room temperature for 10 min-1 hour, filter, wash with water until the washing liquid is neutral, and dry to obtain the product. In the present application, the inorganic filler is not particularly limited and can be selected from kaolin, talc, aluminum hydroxide, alumina, wollastonite, silica, glass powder, diatomaceous earth, etc.

[0032] In a preferred embodiment of the present application, in step S1, the cationic pigment is not particularly limited and can be selected from one or more of cationic red GTL, cationic yellow X-6G, cationic fluorescent yellow X-10GFF, cationic orange 2G, cationic blue X-GRRL, rhodamine 123, and cationic black RL. For example, one of the above cationic pigments, or two or more can be compounded to form different colors.

[0033] In a preferred embodiment of the present application, the preparation method of the dispersed pigment in step S1 is as follows: Disperse the inorganic filler in water, add the cationic pigment, disperse evenly, filter, and dry the filtered solid to obtain the product. First, disperse the inorganic filler in an aqueous solution (ultrasonic dispersion can be used), and then add the cationic pigment. Since the cationic pigment can dissolve in water and exists in a molecular state in water, it undergoes electrostatic adsorption with the negative charge on the surface of the inorganic filler. The cationic pigment is adsorbed onto the surface of the inorganic filler, and the inorganic filler becomes the carrier of the cationic pigment.

[0034] In a more preferred embodiment of the present application, the weight ratio of the inorganic filler, water, and cationic pigment is 1:1-100:0.01-1. Further preferably, the weight ratio of the inorganic filler, water, and cationic pigment is 1:10-50:0.02-0.06. With the above weight ratio, the cationic pigment can be better dispersed in water and undergo electrostatic adsorption with the inorganic filler, and the cationic pigment is better dispersed on the surface of the inorganic filler.

[0035] In a preferred embodiment of the present application, in step S2, the weight ratio of the dispersed pigment, linear-structured polyurethane, and TPU is 0.5-5:0.2-2:100. Through the dispersion effect of the linear-structured polyurethane, the dispersed pigment can be better dispersed in the TPU, realizing uniform and stable dyeing of the TPU, and supercritical foaming can achieve better dyeing.

[0036] In a preferred embodiment of the present application, in step S2, the linear polyurethane is prepared by reacting a diol raw material with a diisocyanate in a molar ratio of 1:0.9 - 1; more preferably, the linear polyurethane is prepared by reacting a diol raw material with a diisocyanate in a molar ratio of 1:0.92 - 1. For example, the molar ratio can be 1:0.92, 1:0.93, 1:0.94, 1:0.95, 1:0.96, 1:0.97, 1:0.98, 1:0.99, 1:1, etc. In the present application, there is no particular limitation on the preparation method of the linear polyurethane, and it can be prepared according to the existing polyurethane preparation methods. There are mainly two existing polyurethane preparation methods. The first is to mix the diol raw material and the diisocyanate together for reaction, and the second is to first react the polymer diol with the diisocyanate and then add a chain extender for chain extension reaction. In the present application, there is no particular limitation on the diisocyanate, and it can be a diisocyanate commonly used in polyurethane preparation, such as isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), toluene diisocyanate (TDI), etc.

[0037] The diol raw material is composed of a first polymer diol, a second polymer diol, and a chain extender in a weight ratio of 1:0.5 - 2:0.02 - 0.1;

[0038] The average molecular weight of the first polymer diol is 5000 - 10000;

[0039] The average molecular weight of the second polymer diol is 200 - 2000.

[0040] Adopting the above technical solution, the average molecular weights of the first polymer diol and the second polymer diol are quite different, and they can each play a role: the first polymer diol has a relatively high average molecular weight and can achieve good coating of the dispersed pigment particles, and the second polymer diol can improve the compatibility between the linear polyurethane and TPU. Therefore, the linear polyurethane of the present application can improve the dispersibility of the dispersed pigment in TPU.

[0041] In a more preferred embodiment of the present application, the first polymer diol and the second polymer diol are each independently selected from one or several combinations of polyether diols and polyester diols. In the present application, there is no particular limitation on the polyether diol, and it can be polyethylene glycol, polypropylene glycol, polytetrahydrofuran diol, polyethylene glycol / polypropylene glycol copolymer, etc.

[0042] In a more preferred embodiment of the present application, the chain extender is selected from one or a combination of ethylene glycol, 1,4-butanediol, 1,3-propanediol, 2,2-dimethylolbutyric acid, tartaric acid, and 2,2-bis(hydroxymethyl)propionic acid. Using chain extenders such as ethylene glycol, 1,4-butanediol, and 1,3-propanediol will not introduce side chain groups into the molecular structure of linear polyurethane; using chain extenders such as 2,2-dimethylolbutyric acid, tartaric acid, and 2,2-bis(hydroxymethyl)propionic acid can introduce carboxyl groups into the side chains of the molecular structure of linear polyurethane, and the electronegative carboxyl groups can undergo electrostatic adsorption with the cations in the dispersed pigments, further improving the dispersibility and dispersion stability of the dispersed pigments in TPU.

[0043] In a further preferred embodiment of the present application, the molar proportion of one or a combination of 2,2-dimethylolbutyric acid, tartaric acid, and 2,2-bis(hydroxymethyl)propionic acid in the chain extender is 30-100%. By adopting the above technical solution, the dispersibility and dispersion stability of the dispersed pigments in TPU can be further improved. For example, the molar proportion of one or a combination of 2,2-dimethylolbutyric acid, tartaric acid, and 2,2-bis(hydroxymethyl)propionic acid in the chain extender is 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, etc. One or a combination of 2,2-dimethylolbutyric acid, tartaric acid, and 2,2-bis(hydroxymethyl)propionic acid can be either 2,2-dimethylolbutyric acid, tartaric acid, or 2,2-bis(hydroxymethyl)propionic acid alone, or a combination of two or three of 2,2-dimethylolbutyric acid, tartaric acid, and 2,2-bis(hydroxymethyl)propionic acid, such as the combination of 2,2-dimethylolbutyric acid and tartaric acid, the combination of 2,2-dimethylolbutyric acid and 2,2-bis(hydroxymethyl)propionic acid, etc.

[0044] The technical solution of the present application will be described in detail below with reference to examples and comparative examples. Unless otherwise specified, the parts in the following examples and comparative examples are all parts by weight.

[0045] Preparation Examples 1-5 for preparing linear polyurethane

[0046] Preparation Example 1

[0047] The molar ratio of polytetrahydrofuran diol (average molecular weight 650), 1,4-butanediol, and IPDI is 0.92:0.08:0.95.

[0048] After drying and removing water from polytetrahydrofuran diol, it was added to a reaction vessel. Under nitrogen protection, IPDI was added, and the temperature was raised to 90 - 100 °C for reaction for 1 hour. Dibutyltin dilaurate accounting for 0.15% of the total weight of the reaction raw materials was added, and the reaction continued until the theoretical isocyanate content was reached. 1,4-Butanediol was added, and the reaction continued for 3 hours. Then the temperature was lowered to obtain a polyurethane with a linear structure.

[0049] Preparation Example 2

[0050] The molar ratio of polypropylene glycol (average molecular weight 8000), polytetrahydrofuran diol (average molecular weight 650), 1,4-butanediol, and IPDI was 0.46:0.46:0.08:0.95.

[0051] After drying and removing water from polypropylene glycol and polytetrahydrofuran diol, they were added to a reaction vessel. Under nitrogen protection, IPDI was added, and the temperature was raised to 90 - 100 °C for reaction for 1 hour. Dibutyltin dilaurate accounting for 0.15% of the total weight of the reaction raw materials was added, and the reaction continued until the theoretical isocyanate content was reached. 1,4-Butanediol was added, and the reaction continued for 3 hours. Then the temperature was lowered to obtain a polyurethane with a linear structure.

[0052] Preparation Example 3

[0053] In Preparation Example 2, the molar ratio of polypropylene glycol, polytetrahydrofuran diol, 1,4-butanediol, and IPDI was adjusted to 0.6:0.32:0.08:0.95, and the remaining steps remained unchanged.

[0054] Preparation Example 4

[0055] The molar ratio of polypropylene glycol (average molecular weight 8000), polytetrahydrofuran diol (average molecular weight 650), 1,4-butanediol, 2,2-bis(hydroxymethyl)propionic acid, and IPDI was 0.46:0.46:0.04:0.04:0.95.

[0056] After drying and removing water from polypropylene glycol and polytetrahydrofuran diol, they were added to a reaction vessel. Under nitrogen protection, IPDI was added, and the temperature was raised to 90 - 100 °C for reaction for 1 hour. Dibutyltin dilaurate accounting for 0.15% of the total weight of the reaction raw materials was added, and the reaction continued until the theoretical isocyanate content was reached. 1,4-Butanediol and 2,2-bis(hydroxymethyl)propionic acid were added, and the reaction continued for 3 hours. Then the temperature was lowered to obtain a polyurethane with a linear structure.

[0057] Preparation Example 5

[0058] The molar ratio of polypropylene glycol (average molecular weight 9500), polytetrahydrofuran diol (average molecular weight 1000), 1,4-butanediol, 2,2-bis(hydroxymethyl)propionic acid, and IPDI was 0.54:0.4:0.02:0.04:0.97, and the preparation method was as shown in Preparation Example 4.

[0059] Preparation Example 6-8 Preparation of Dispersed Pigments

[0060] Preparation Example 6

[0061] Add 1 part of kaolin with an average particle size of 2.5 μm to 100 parts of water, ultrasonically disperse evenly, add 0.2 part of cationic yellow X-6G, ultrasonically disperse evenly, continue stirring for 10 min, filter, and dry the filtered solid to obtain the dispersed pigment.

[0062] Preparation Example 7

[0063] Add 1 part of talc powder with an average particle size of 2 μm to 50 parts of water, ultrasonically disperse evenly, add 0.3 part of cationic red GTL, ultrasonically disperse evenly, continue stirring for 10 min, filter, and dry the filtered solid to obtain the dispersed pigment.

[0064] Preparation Example 8

[0065] Add 1 part of talc powder with an average particle size of 2 μm to 50 parts of water, ultrasonically disperse evenly, add 0.1 part of cationic blue X-GRRL, ultrasonically disperse evenly, continue stirring for 10 min, filter, and dry the filtered solid to obtain the dispersed pigment.

[0066] Example 1

[0067] Add the dispersed pigment of Preparation Example 6, the linear-structured polyurethane of Preparation Example 1, and TPU to the twin-screw extruder in a weight ratio of 1.5:0.4:100, and extrude, inject, and mold at 210-235 °C to obtain the preformed shoe material.

[0068] Foam the preformed shoe material using the supercritical CO2 foaming technology to obtain the colored supercritical foamed shoe material. The supercritical CO2 foaming technology is specifically as follows: Place the preformed shoe material in an autoclave and seal it. Saturate the preformed shoe material with supercritical CO2 fluid (pressure of 23 MPa) (temperature 70-75 °C, time 3 h), quickly release the pressure to obtain the swollen shoe material; Take out the swollen shoe material and place it in a constant temperature device at 100-110 °C for 22 minutes to obtain the colored supercritical foamed shoe material

[0069] Example 2

[0070] In Example 1, the linear-structured polyurethane of Preparation Example 1 is replaced with the linear-structured polyurethane of Preparation Example 2 in an equal weight portion, and the remaining steps remain unchanged.

[0071] Example 3

[0072] In Example 1, the linear-structured polyurethane of Preparation Example 1 is replaced with the linear-structured polyurethane of Preparation Example 3 in an equal weight portion, and the remaining steps remain unchanged.

[0073] Example 4

[0074] In Example 1, the linear-structured polyurethane of Preparation Example 1 was replaced with the linear-structured polyurethane of Preparation Example 4 in an equal number of parts by weight, and the remaining steps remained unchanged.

[0075] Example 5

[0076] In Example 1, the linear-structured polyurethane of Preparation Example 1 was replaced with the linear-structured polyurethane of Preparation Example 5 in an equal number of parts by weight, and the remaining steps remained unchanged.

[0077] Example 6

[0078] The dispersed pigment of Preparation Example 7, the linear-structured polyurethane of Preparation Example 4, and TPU were added to a twin-screw extruder in a weight ratio of 2:0.7:100, and were extruded, injection-molded, and formed at 210 - 235 °C to obtain a preformed shoe material.

[0079] The preformed shoe material was foamed using the supercritical CO2 foaming technology of Example 1 to obtain a colored supercritical foamed shoe material.

[0080] Example 7

[0081] The dispersed pigment of Preparation Example 8, the linear-structured polyurethane of Preparation Example 4, and TPU were added to a twin-screw extruder in a weight ratio of 3:1:100, and were extruded, injection-molded, and formed at 210 - 235 °C to obtain a preformed shoe material.

[0082] The preformed shoe material was foamed using the supercritical CO2 foaming technology of Example 1 to obtain a colored supercritical foamed shoe material.

[0083] Example 8

[0084] The dispersed pigment of Preparation Example 7, the dispersed pigment of Preparation Example 8, the linear-structured polyurethane of Preparation Example 4, and TPU were added to a twin-screw extruder in a weight ratio of 2:1:1.2:100, and were extruded, injection-molded, and formed at 210 - 235 °C to obtain a preformed shoe material.

[0085] The preformed shoe material was foamed using the supercritical CO2 foaming technology of Example 1 to obtain a colored supercritical foamed shoe material.

[0086] Comparative Example 1

[0087] In Example 1, the dispersed pigment of Preparation Example 6 was replaced with cationic yellow X-6G at 15% of the weight of the dispersed pigment of Preparation Example 6, and the remaining steps remained unchanged.

[0088] Comparative Example 2

[0089] In Example 1, the linear-structured polyurethane of Preparation Example 1 was not added, and the remaining steps remained unchanged.

[0090] Comparative Example 3

[0091] In Example 1, the dispersed pigment in Preparation Example 6 was replaced with a composition consisting of cationic yellow X-6G and kaolin with an average particle size of 2.5 μm in an equal weight portion, and the weight ratio was 1.5:8.5. The remaining steps remained unchanged.

[0092] Performance Test

[0093] Five positions in sequence from the toe position to the heel position of the foamed shoe materials of Examples 1-8 and Comparative Examples 1-3 were taken respectively - the first position, the second position, the middle position, the fourth position and the fifth position. The color difference value ΔE was measured using a precision color difference meter. Taking the chromaticity of the middle position as the comparison reference, the color difference values of the other 4 positions relative to the middle position are shown in Table 1 below.

[0094] Table 1 ΔE

[0095] First position Second position Fourth position Fifth position Example 1 0.17 0.13 0.19 0.22 Example 2 0.12 0.11 0.15 0.15 Example 3 0.11 0.14 0.12 0.15 Example 4 0.07 0.10 0.11 0.09 Example 5 0.10 0.12 0.07 0.10 Example 6 0.09 0.08 0.13 0.11 Example 7 0.12 0.07 0.09 0.08 Example 8 0.09 0.11 0.10 0.05 Comparative Example 1 1.5 1.2 1.3 1.7 Comparative Example 2 0.74 0.61 0.92 0.87 Comparative Example 3 1.3 1.0 0.8 1.1

[0096] It can be seen from the results in Table 1 that the color difference of the colored supercritical foamed shoe material obtained by the preparation process of the colored supercritical foamed shoe material of the present application is very small and the chromaticity uniformity is good.

[0097] At room temperature, the foamed shoe materials of Example 1, Example 2, Example 4, Comparative Example 1 and Comparative Example 2 were respectively immersed in absolute ethanol for 2 hours, taken out, dried and then air-dried. The color difference before and after immersion at the middle position was measured. Three foamed shoe materials were taken for each test, and the test results were averaged. The results are shown in Table 2 below.

[0098] Table 2 ΔE

[0099] Example 1 Example 2 Example 4 Comparative Example 1 Comparative Example 2 0.31 0.24 0.15 0.84 1.1

[0100] It can be seen from the test results in Table 2 that the colored supercritical foamed shoe material obtained by the preparation process of the colored supercritical foamed shoe material of the present application has good stability.

[0101] This specific embodiment is only an explanation of the present application and is not a limitation of the present application. Those skilled in the art can make modifications to this embodiment without creative contributions according to needs after reading this specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A preparation process of a colored supercritical foamed shoe material, characterized in that, It includes the following steps: S1. Prepare inorganic filler to adsorb cationic pigment to obtain dispersed pigment. The preparation method of the dispersed pigment is as follows: Add 1 part of kaolin with an average particle size of 2.5 μm to 100 parts of water, ultrasonically disperse evenly, add 0.2 part of cationic yellow X-6G, ultrasonically disperse evenly, continue stirring for 10 min, filter, dry the filtered solid to obtain dispersed pigment; S2. Add the dispersed pigment, linear structure polyurethane and TPU obtained in step S1 into a twin-screw extruder according to a weight ratio of 1.5:0.4:100, extrude, inject and mold at 210-235 °C to obtain a preformed shoe material; The preparation method of the linear structure polyurethane is as follows: The molar ratio of polypropylene glycol with an average molecular weight of 8000, polytetrahydrofuran glycol with an average molecular weight of 650, 1,4-butanediol, 2,2-bis(hydroxymethyl)propionic acid, and IPDI is 0.46:0.46:0.04:0.04:0.

95. After drying and dehydrating polypropylene glycol and polytetrahydrofuran glycol, add them to a reaction vessel, add IPDI under nitrogen protection, raise the temperature to 90-100 °C and react for 1 hour, add 0.15% of dibutyltin dilaurate based on the total weight of the reaction raw materials, continue reacting until the theoretical isocyanate content, add 1,4-butanediol and 2,2-bis(hydroxymethyl)propionic acid, continue reacting for 3 hours, and cool down to obtain linear structure polyurethane; S3. Supercritically foam the preformed shoe material obtained in step S2 to obtain the colored supercritical foamed shoe material. The supercritical CO2 foaming step is as follows: Place the preformed shoe material in an autoclave and seal it. Under the condition of a pressure of 23 MPa, saturate the preformed shoe material with supercritical CO2 fluid at a temperature of 70-75 °C for 3 h, quickly release the pressure to obtain a swollen shoe material; Take out the swollen shoe material and place it in a constant temperature device at 100-110 °C for 22 minutes to obtain the colored supercritical foamed shoe material.