High-compressibility polyurethane sole stock solution, preparation method thereof and polyurethane sole

Abstract

The invention discloses a high-compressibility polyurethane shoe sole stock solution, a preparation method thereof and a polyurethane shoe sole. The high-compressibility polyurethane shoe sole stock solution comprises a component A and a component B, a polymer polyol A2; grafting polyether polyol A3; a foaming agent; a foam stabilizer; the hydroxyl value of the component A ranges from 44.0 mgKOH / g to 48.0 mgKOH / g; the component B is an isocyanate-terminated prepolymer, wherein the mass percentage of an isocyanate group is 19-21%, and the addition amount of the composite catalyst is 1.9-2.6% of the mass of the component A; when in use, the component A and the component B are mixed according to the mass ratio of 100: (77-81). According to the invention, the dynamic balance of foaming and gel reaction is ensured, so that a uniform and fine foam structure with tough hole walls is formed, and the obtained polyurethane sole has the advantages of low density, obviously improved compression strength, greatly reduced compression set and excellent rebound rate.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a high-compressibility polyurethane shoe sole raw material, its preparation method, and a polyurethane shoe sole. Background Technology

[0002] Polyurethane soles are widely used in various footwear products due to their advantages such as light weight, wear resistance, flexibility, and wearing comfort. However, traditional polyurethane materials have difficulty balancing hardness and elasticity in their microstructure, resulting in a significant gap in compressive strength and compression set compared to special rubbers. This makes them unsuitable for applications with extremely high requirements for shock absorption, support, and durability, such as the midsoles of special safety shoes, high-intensity sports shoes, or certain industrial cushioning components.

[0003] While existing technologies have attempted to improve polyurethane performance by adjusting the type of common polyether polyol or adding fillers, these approaches often come at the expense of other aspects. For example, increasing hardness often leads to a decrease in resilience and tear resistance, and also narrows the processing window, resulting in a low product yield.

[0004] Those skilled in the art generally know that adding rigid fillers or increasing crosslinking density can improve the hardness and compressive strength of polyurethane, but this almost inevitably leads to decreased material resilience, increased brittleness, and a narrower processing window. Furthermore, while the foaming process is crucial to performance, the industry generally believes that foaming temperature primarily affects the foaming rate and surface quality, with insufficient understanding of its synergistic effect with specific formulations to precisely control the cell structure and thus decisively influence the final compressive resilience performance. This contradiction—that increasing strength inevitably sacrifices elasticity—has become a technical obstacle to developing high-performance polyurethane shoe soles.

[0005] Therefore, there is an urgent need in this field to develop a polyurethane shoe sole raw material that combines high compression performance, high resilience, and good processability to fill the gap in existing technologies and achieve an effective replacement for special rubbers. Summary of the Invention

[0006] This invention provides a high-compressibility polyurethane sole raw material and its preparation method, which can solve the technical problems of low compressive strength, poor resilience, and large permanent compression deformation of existing polyurethane soles.

[0007] To solve the above technical problems, the present invention provides a high compressibility polyurethane shoe sole raw material, comprising component A and component B, wherein component A and component B are mixed at a mass ratio of 100:77-81; Component A comprises the following components by weight: Polyester polyol A1: 40-60 parts; Polymer polyol A2: 20-40 parts; Grafted polyether polyol A3: 5-15 parts, wherein the grafted polyether polyol A3 is modified by styrene and acrylonitrile as grafting monomers; Foaming agent: 1-3 parts; Foam stabilizer: 1-3 parts; and catalyst; Component B is an isocyanate-terminated prepolymer, wherein the mass percentage of isocyanate groups in the prepolymer is 19-21%. The polymer polyol A2 is prepared by ring-opening polymerization of propylene glycol as an initiator with at least one of ethylene oxide, propylene oxide and ethylene oxide; The grafted polyether polyol A3 is prepared by free radical polymerization of styrene and acrylonitrile as grafting monomers, with polyether polyol as matrix. In a preferred embodiment of the present invention, the polyester polyol A1 has a functionality of 2, a number-average molecular weight of 1700-2500, an acid value of 0.1-0.8 mgKOH / g, and a hydroxyl value of 50-55 mgKOH / g. The polymer polyol A2 has a functionality of 2, a number-average molecular weight of 2000-4500, an acid value of 0.01-0.08 mgKOH / g, and a hydroxyl value of 32-35 mgKOH / g. The grafted polyether polyol A3 has a functionality of 2, a number-average molecular weight of 3000-8000, and a hydroxyl value of 26-30 mgKOH / g.

[0008] In a preferred embodiment of the present invention, the weight ratio of styrene to acrylonitrile monomer in the grafted polyether polyol A3 is 70:30 to 50:50.

[0009] In a preferred embodiment of the present invention, component A further comprises 0.5-2 parts by weight of a chain extender, wherein the chain extender is at least one selected from ethylene glycol, 1,4-butanediol or 1,3-propanediol.

[0010] In a preferred embodiment of the present invention, the prepolymer is prepared by reacting polyether polyol B1 and / or polyether polyol B2 with an excess of isocyanate, wherein the polyether polyol B1 is prepared by ring-opening polymerization of propylene oxide with trimethylolpropane as an initiator; and the polyether polyol B2 is prepared by ring-opening polymerization of at least one of ethylene oxide, propylene oxide, or butane oxide with ethylene glycol or diethylene glycol as an initiator.

[0011] In a preferred embodiment of the present invention, the polyether polyol B1 has a functionality of 3 and a number-average molecular weight of 3000-4500; the polyether polyol B2 has a functionality of 2, a number-average molecular weight of 1000-2500, and an acid value of 0.01-0.05 mgKOH / g.

[0012] In a preferred embodiment of the present invention, the catalyst includes an alkanolamine catalyst and an organometallic catalyst.

[0013] To address the aforementioned technical problems, this invention also discloses a method for preparing the above-mentioned high-compressibility polyurethane shoe sole raw material, comprising the following steps: (1) Preparation of component A: The polyester polyol A1 of the formula amount is dehydrated for 2-3 hours at 100-120℃ and vacuum degree not lower than -0.095MPa; then the temperature is lowered to 40-60℃, and the polymer polyol A2, grafted polyether polyol A3, foaming agent, foam stabilizer and chain extender added as needed are added. The mixture is stirred and mixed evenly to obtain homogeneous component A. (2) Preparation of component B: Dehydrate the polyether polyol B1 and / or polyether polyol B2 in the prescribed amount for 2-3 hours at 100-120℃ and vacuum degree not lower than -0.095 MPa; then cool down to 70-90℃, add excess isocyanate and acidic storage stabilizer under inert gas protection, and keep the reaction at the temperature for 2-4 hours to obtain a prepolymer with isocyanate group mass percentage of 19-21%, which is component B.

[0014] To address the aforementioned technical problems, this invention also discloses a method for preparing polyurethane shoe soles using the aforementioned high-compressibility polyurethane shoe sole raw material, comprising the following steps: S1: Preheat component A and component B to 30-40°C respectively; S2: Measure the components A and B according to the mass ratio of 100:77-81; S3: Mix the metered component A and component B at a high speed of 4000-6000 rpm for 3-8 seconds; S4: Pour the mixture into a mold preheated to 50-60℃ and cure it at a curing temperature of 75-85℃ for 5-10 minutes; S5: Demolding to obtain the finished polyurethane shoe sole.

[0015] To solve the above-mentioned technical problems, the present invention also discloses a polyurethane shoe sole, which is made by reacting and molding the above-mentioned high compressibility polyurethane shoe sole raw liquid through the above-mentioned method. The shoe sole has a uniform and dense foam structure, its compressive strength is not less than 160 kPa, its permanent compression deformation is not greater than 20%, and its rebound rate is not less than 45%.

[0016] The beneficial effects of this invention are as follows: This invention provides a high-compressibility polyurethane shoe sole raw material, its preparation method, and a polyurethane shoe sole. Through the ternary synergistic molecular design of polyester polyol A1, polymer polyol A2, and grafted polyether polyol A3, a "rigid and flexible" microphase separation structure is constructed. By synergistically designing the mass ratio of component A to component B (100:77-81) and the curing temperature (75-85℃), the dynamic balance between foaming and gelation reactions is ensured, thereby forming a uniform, fine, and tough pore structure. This results in a polyurethane shoe sole that maintains low density while significantly improving compressive strength, greatly reducing compression set, and exhibiting excellent resilience. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the process flow for preparing high-compressibility polyurethane shoe sole raw material to obtain polyurethane shoe soles according to the present invention. Detailed Implementation

[0018] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0019] Example 1 Preparation of polyester polyol A1: In a reactor equipped with a stirrer, fractionating column, thermometer, and nitrogen inlet pipe, metered amounts of ethylene glycol and adipic acid (with an alcohol-acid molar ratio of 1.1:1) were added according to the target hydroxyl value. Tetrabutyl titanate was added as a catalyst at a concentration of 200 ppm of the total feed. After purging the air with nitrogen, the temperature was slowly raised to 160°C under nitrogen protection to begin esterification and dehydration. Once the rate of water loss slowed, the temperature was gradually increased to 210°C, and the reaction continued until the acid value dropped below 5 mgKOH / g. Subsequently, the vacuum system was activated, and the vacuum level was gradually increased to above -0.098 MPa. Polycondensation was then carried out at 220°C to continuously remove residual water and small molecule products, while closely monitoring the acid and hydroxyl values. The reaction was stopped when the acid value reached 0.6 mgKOH / g and the hydroxyl value reached 50 mgKOH / g. The temperature was lowered to below 80°C, and the product was filtered to obtain polyester polyol A1 with a functionality of 2 and a number-average molecular weight of approximately 2000.

[0020] Preparation of polymer polyol A2: Metered amounts of propylene glycol as an initiator and catalyst (such as KOH or DMC) were added to a high-pressure reactor, heated to 100°C, and dehydrated under vacuum. Then, the reactor was purged with nitrogen, heated to 120°C, and propylene oxide (or a mixture with ethylene oxide) was continuously introduced with stirring, while maintaining the pressure inside the reactor at 0.4 MPa. The reaction was continued until the propylene oxide was completely added. After aging, the product underwent neutralization, dehydration, filtration, and other post-processing steps to obtain polymer polyol A2 with a number-average molecular weight of 4000 and a hydroxyl value of 34 mgKOH / g.

[0021] Preparation of grafted polyether polyol A3: 1000 g of a polyether polyol with a functionality of 2, a number-average molecular weight of approximately 4000, and a hydroxyl value of 28 mgKOH / g, prepared by the above method, was added to a four-necked flask. Stirring was started, and nitrogen gas was introduced three times to replace the air.

[0022] Heat the contents of the flask to 85°C. In another container, prepare a monomer mixture: 130 g of styrene, 70 g of acrylonitrile (i.e., styrene:acrylonitrile = 65:35), then add 4.0 g of initiator azobisisobutyronitrile (AIBN) (accounting for 2.0% of the total monomers) and 2.0 g of chain transfer agent mercaptoethanol, and stir to dissolve.

[0023] After the base polyether temperature stabilized at 85℃, the monomer mixture was added dropwise at a constant pressure dropping funnel over a period of approximately 3 hours. During the addition, the reaction system temperature was controlled at 115±2℃ using an external oil bath. After the addition was complete, the reaction was maintained at 115℃ for another 2 hours to ensure complete monomer reaction. Subsequently, the reaction system was cooled to below 60℃. Unreacted monomers were removed by vacuum devolatilization at -0.095 MPa and 80℃ for 1 hour. The resulting reaction product was filtered through a 100-mesh filter to obtain a slightly yellow, viscous liquid, which is the grafted polyether polyol A3. Testing showed that its solid content was approximately 42%, its hydroxyl value was approximately 28 mgKOH / g (calculated), and its viscosity (at 25℃) was approximately 4500 mPa·s. The product has a functionality of approximately 2 and a number-average molecular weight in the range of approximately 5000-6000.

[0024] Preparation of polyether polyol B1: Add 134.0 g (1.0 mol) of trimethylolpropane (TMP) and 4.5 g of potassium hydroxide (approximately 0.25% of the expected total product mass) to a clean, dry 2-liter high-pressure reactor. Replace the air in the reactor three times with nitrogen. Heat to 110°C and dehydrate under vacuum (-0.095 MPa) for 1 hour with stirring to remove trace amounts of moisture from the raw materials. After dehydration, restore the reactor pressure to atmospheric pressure using nitrogen. Adjust and stabilize the reactor temperature at 105±5°C.

[0025] 1162 g of propylene oxide was continuously and uniformly introduced into the reactor. The exothermic reaction was controlled by cooling water to maintain the pressure inside the reactor below 0.3 MPa. After the propylene oxide was completely added and the pressure dropped to near atmospheric pressure, the temperature was adjusted to 115 ± 5 °C, and then 174 g of ethylene oxide was introduced. After the addition was complete, the reactor was kept at 115 °C for 2 hours until the pressure inside the reactor no longer decreased, indicating that the alkyl oxide reaction was complete. The reaction product was cooled to below 80 °C. A measured amount of phosphoric acid aqueous solution was added for neutralization until the reaction solution was neutral or weakly acidic. Magnesium silicate adsorbent was added, and the mixture was stirred for 1 hour to adsorb the potassium salts produced during neutralization. The material was filtered to obtain a clear crude polyether, which was dehydrated at 120 °C and a vacuum of -0.095 MPa for 2 hours. The temperature was then lowered to below 60 °C, and the product was discharged as a slightly yellow viscous liquid, which was polyether polyol B1.

[0026] Preparation of polyether polyol B2: Add 318.0 g (3.0 mol) of diethylene glycol (DEG) and 6.0 g of KOH catalyst to a dry, high-pressure reactor. After purging the reactor with nitrogen, heat to 110 °C and dehydrate under vacuum (-0.095 MPa) with stirring for 1 hour. After dehydration is complete, restore atmospheric pressure and stabilize the temperature at 105 ± 2 °C.

[0027] Stirring was started, and 1740 g of propylene oxide was continuously and uniformly fed into the reactor. The heat of reaction was controlled by jacket cooling, and the pressure inside the reactor was maintained at 0.25 MPa. The reactor was kept at 110°C for 2 hours until the pressure inside the reactor dropped to near atmospheric pressure, indicating that the reaction was basically complete.

[0028] Cool to below 80℃. Add an appropriate amount of phosphoric acid aqueous solution to neutralize to neutral. Add magnesium silicate as adsorbent, stir, and filter to remove potassium salts. Dehydrate the filtrate under vacuum at 120℃ and -0.095 MPa for 2 hours. Cool and discharge to obtain a colorless to slightly yellow transparent viscous liquid, which is polyether polyol B2.

[0029] Preparation of component A: Based on 100 parts by weight of component A, 50 parts of dehydrated polyester polyol A1, 35 parts of polymer polyol A2, and 10 parts of grafted polyether polyol A3 were added to a mixing vessel and stirred at 50°C. Cyclopentane (2 parts), foam stabilizer L-580 (1.5 parts), chain extender 1,4-butanediol (1 part), A-33 catalyst (a dipropylene glycol solution of triethylenediamine, i.e., an alkanolamine catalyst) 1.5 parts, and T-9 catalyst (stannous octoate, i.e., an organometallic catalyst) were added sequentially. Stirring continued for 60 minutes until completely homogeneous, yielding component A. The calculated hydroxyl value of component A was approximately 46 mgKOH / g (calculated by weighting based on the feed amounts of each component and their respective hydroxyl values: A1 = 50 mgKOH / g, A2 = 34 mgKOH / g, and A3 = 28 mgKOH / g).

[0030] Preparation of component B: In a reactor, 80 parts of polyether polyol B1 and 20 parts of polyether polyol B2 were added, and the mixture was dehydrated for 2.5 hours at 110°C and under a vacuum of -0.098 MPa. The mixture was then cooled to 80°C, and under nitrogen protection, 45 parts of MDI (in excess) and 0.001 parts of phosphoric acid (approximately 0.001% of the total feed) were added. The reaction was maintained at this temperature for 3 hours. A sample was taken and the NCO content was determined to be 20.1%. The prepolymer was then obtained.

[0031] Sole molding: Component A (which already contains the formulated amount of catalyst) and component B are preheated to 35°C respectively. The materials are weighed according to a mass ratio of component A to component B of 100:80.

[0032] Weigh out components A and B and mix them in a high-pressure foaming machine (5000 rpm, 5s). Pour the resulting mixture into a 60℃ mold and then into an 80℃ drying tunnel to cure for 8 minutes.

[0033] Demolding yields shoe sole sample S1.

[0034] Example 2 The difference from Example 1 is that the amount of grafted polyether polyol A3 is reduced to 7 parts, while the amount of polymer polyol A2 is increased to 38 parts, keeping the total amount of component A unchanged. The preparation of components A and B and the shoe sole molding process parameters are the same as in Example 1. Sample S2 is obtained.

[0035] Example 3 The difference from Example 1 is that the components A and B were fed in a mass ratio of 100:78. Sample S3 was obtained.

[0036] Comparative Example 1 The difference from Example 1 is that 10 parts of grafted polyether polyol A3 are not added; instead, an equal amount of polyester polyol A1 is used (i.e., the total amount of A1 is 60 parts). The preparation and molding process are the same as in Example 1. Sample DS1 is obtained.

[0037] Comparative Example 2 The formula is exactly the same as in Example 1. The difference is that during the sole molding process, the drying tunnel temperature is set to 65°C, while other process parameters remain unchanged. Sample DS2 is obtained.

[0038] The samples obtained from Examples 1-3 and Comparative Examples 1-2 were subjected to performance tests, and the results are shown in Table 1 below.

[0039] Table 1 The results in Table 1 show that: With similar density and hardness, Example 1 containing A3 significantly outperformed Comparative Example 1 without A3 in both compressive strength (increased by 54%) and resilience (increased by 32%), while reducing compression set by 54%.

[0040] This fully demonstrates that A3, as a nanoscale organic rigid reinforcing phase, effectively enhances the strength and toughness of the polymer matrix and cell walls, and forms an effective synergistic reinforcing effect with A1 and A2.

[0041] With the exact same formulation, simply lowering the curing temperature from 80℃ to 65℃ (Comparative Example 2) resulted in a significant decrease in the product's compressive strength and resilience, while a significant increase in compression set. This verifies that precisely controlling the curing temperature at 80±1℃, matched with the mass ratio of component A to component B (100:77-81), is a necessary process condition for achieving optimal performance. Within this window, the foaming and gelation reaction rates are optimally matched, forming an ideal cell structure; deviations lead to reaction imbalances, resulting in structural defects and performance degradation.

[0042] Example 2 shows that, within the scope of the invention, appropriately reducing the amount of A3 slightly reduces the performance, but it is still far superior to the comparative example and maintains good overall performance, proving that the formulation has a certain degree of adjustability to meet different hardness requirements.

[0043] The polyurethane shoe sole prepared by this invention has excellent comprehensive performance, with a compressive strength of not less than 160 kPa, a compression set of not more than 20%, and a resilience of not less than 45%.

[0044] This invention optimizes the microphase structure and cell morphology of polyurethane by synergistically controlling specific grafted polyether polyols, the mass ratio of component A to component B (100:77-81), and the curing temperature. This significantly improves compressive strength and resilience under low density conditions, which is a technical effect that the prior art could not have foreseen.

[0045] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A high-compressibility polyurethane shoe sole raw material, characterized in that, It contains component A and component B, and component A and component B are mixed in a mass ratio of 100:77-81; Component A comprises the following components by weight: Polyester polyol A1: 40-60 parts; Polymer polyol A2: 20-40 parts; Grafted polyether polyol A3: 5-15 parts, wherein the grafted polyether polyol A3 is modified by styrene and acrylonitrile as grafting monomers; Foaming agent: 1-3 parts; Foam stabilizer: 1-3 parts; And a catalyst, the amount of which is added is 1.9-2.6% of the mass of component A; The hydroxyl value of component A is 44.0-48.0 mgKOH / g; Component B is an isocyanate-terminated prepolymer, wherein the mass percentage of isocyanate groups in the prepolymer is 19-21%. The polymer polyol A2 is prepared by ring-opening polymerization of propylene glycol as an initiator with at least one of ethylene oxide, propylene oxide and ethylene oxide; The grafted polyether polyol A3 is prepared by free radical polymerization of styrene and acrylonitrile as grafting monomers, with polyether polyol as the matrix.

2. The high compressibility polyurethane sole raw material according to claim 1, characterized in that, The polyester polyol A1 has a functionality of 2, a number-average molecular weight of 1700-2500, an acid value of 0.1-0.8 mgKOH / g, and a hydroxyl value of 50-55 mgKOH / g. The polymer polyol A2 has a functionality of 2, a number-average molecular weight of 2000-4500, an acid value of 0.01-0.08 mgKOH / g, and a hydroxyl value of 32-35 mgKOH / g. The grafted polyether polyol A3 has a functionality of 2, a number-average molecular weight of 3000-8000, and a hydroxyl value of 26-30 mgKOH / g.

3. The high compressibility polyurethane sole raw material according to claim 2, characterized in that, In the grafted polyether polyol A3, the weight ratio of styrene to acrylonitrile monomer is 70:30 to 50:

50.

4. The high compressibility polyurethane sole raw material according to claim 1, characterized in that, The A component further contains 0.5-2 parts by weight of a chain extender, wherein the chain extender is at least one of ethylene glycol, 1,4-butanediol or 1,3-propanediol.

5. The high compressibility polyurethane sole raw material according to claim 1, characterized in that, The prepolymer is prepared by reacting polyether polyol B1 and / or polyether polyol B2 with excess isocyanate, wherein the polyether polyol B1 is prepared by ring-opening polymerization of propylene oxide with trimethylolpropane as an initiator; and the polyether polyol B2 is prepared by ring-opening polymerization of ethylene oxide, propylene oxide, or butane as an initiator with ethylene glycol or diethylene glycol as an initiator.

6. The high compressibility polyurethane sole raw material according to claim 5, characterized in that, The polyether polyol B1 has a functionality of 3 and a number-average molecular weight of 3000-4500; the polyether polyol B2 has a functionality of 2, a number-average molecular weight of 1000-2500, and an acid value of 0.01-0.05 mgKOH / g.

7. The high compressibility polyurethane sole raw material according to claim 1, characterized in that, The catalysts include alkanolamine catalysts and organometallic catalysts.

8. A method for preparing a high-compressibility polyurethane shoe sole raw material as described in any one of claims 1-7, characterized in that, Includes the following steps: (1) Preparation of component A: The formulated amount of polyester polyol A1 is dehydrated for 2-3 hours at 100-120℃ and vacuum degree not lower than -0.095 MPa; then the temperature is lowered to 40-60℃, and the formulated amounts of polymer polyol A2, grafted polyether polyol A3, foaming agent, foam stabilizer and chain extender added as needed are added. The mixture is stirred and mixed evenly to obtain homogeneous component A. (2) Preparation of component B: Dehydrate the polyether polyol B1 and / or polyether polyol B2 in the prescribed amount for 2-3 hours at 100-120℃ and vacuum degree not lower than -0.095 MPa; then cool down to 70-90℃, add excess isocyanate and acidic storage stabilizer under inert gas protection, and keep the reaction at the temperature for 2-4 hours to obtain a prepolymer with isocyanate group mass percentage of 19-21%, which is component B.

9. A method for preparing polyurethane shoe soles using the high compressibility polyurethane shoe sole raw material as described in any one of claims 1-7, characterized in that, Includes the following steps: S1: Preheat component A and component B to 30-40°C respectively; S2: Measure the components A and B according to the mass ratio of 100:77-81; S3: Mix the metered component A and component B at a high speed of 4000-6000 rpm for 3-8 seconds; S4: Pour the mixture into a mold preheated to 50-60℃ and cure it at a curing temperature of 75-85℃ for 5-10 minutes; S5: Demolding to obtain the finished polyurethane shoe sole.

10. A polyurethane shoe sole, characterized in that, It is made by reacting and molding the high compressibility polyurethane sole raw material according to any one of claims 1-7 according to the method described in claim 9. The sole has a uniform and fine pore structure, its compressive strength is not less than 160 kPa, its permanent compression deformation is not greater than 20%, and its rebound rate is not less than 45%.

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