Wear-resistant PU (polyurethane) foaming sole and preparation process thereof

Abstract

The invention discloses a wear-resistant PU (polyurethane) foaming sole and a preparation process thereof. Polyfuran polyol is prepared and then mixed with isocyanate, the chain extender, the auxiliaries and the like, water foaming, demolding and curing are performed to obtain the PU foaming shoe sole, the prepared foaming material has the characteristics of light weight, high elasticity, shock absorption and the like, and compared with the prior art, the obtained shoe sole has multiple properties of wear resistance, oil resistance, buffering resistance and the like, and has the advantages of being good in foaming effect, good in foaming effect and the like. And the service life is longer.

Description

Technical Field

[0001] The invention relates to the technical field of foamed polyurethane, in particular to a wear-resistant PU foamed sole and a preparation process thereof. Background Art

[0002] PU foam soles, that is, polyurethane foam soles, are a kind of polymer synthetic material with the advantages of light weight, wear resistance, folding resistance, good elasticity, high strength, and flex resistance. PU foam soles are not only comfortable to wear and can effectively reduce foot fatigue, but also have good shock absorption. They are suitable for a variety of footwear such as sports shoes, casual shoes, and labor protection shoes. In addition, PU materials are environmentally friendly and easy to hydrolyze. By adjusting the formula, they can also be given acid and alkali resistance, oil resistance, anti-aging, and anti-hydrolysis properties to meet different needs. The production of PU foam soles usually adopts a foaming process, which is to mix polyurethane resin with raw materials such as isocyanate, add various additives, and then perform foaming molding. This process can accurately control the density and hardness of the sole to meet the needs of different footwear. PU foam soles have become one of the indispensable materials in modern footwear manufacturing with their excellent performance, wide application and environmental protection characteristics.

[0003] The wear properties of polyurethane elastomers are jointly determined by a variety of factors inside and outside the material. In addition to being affected by internal factors such as its own strength, hysteresis, elastic modulus, fatigue, etc., it is also affected by external factors such as temperature, pressure, and sliding speed. The higher the tensile strength, the better the wear resistance. The effects of hardness and constant tensile stress on the wear resistance of elastomers vary depending on the type of wear. When the hardness and constant tensile stress are high, the elastomer has a strong ability to resist deformation, which makes it difficult for the micro-convex bodies on the friction surface to be pressed into the matrix, and the friction coefficient is small; in addition, the greater the rigidity of the elastomer surface, the less likely it is to wrinkle and cause curling, and it is more difficult to cause abrasive wear and curling wear. The wear rate of the elastomer slows down and the wear strength decreases, but under fatigue wear conditions, the situation is the opposite. In addition, the viscoelastic parameters have a direct effect on the friction of the elastomer. The larger the viscoelastic parameters, the lower the degree of crosslinking of the rubber will be. When wear occurs, the friction will increase, resulting in an increase in the wear volume. Improving fatigue resistance is beneficial to reducing fatigue wear strength. Improved fatigue resistance can enhance the ability of the elastomer to resist the tensile damage of the surface caused by friction, resulting in a delayed appearance of the wear pattern. In the case of fatigue wear, the hysteresis loss increases, which increases the friction coefficient and temperature rise, resulting in a decrease in the wear resistance of the elastomer.

[0004] Patent No. 87108373 relates to a novel furan polyol, the core feature of which is that the polyol is composed of the following components: a compound containing a polyol, a monoamine or a polyamine group. These compounds may contain a furan ring, or may be mixed with a chain extender consisting of an organic epoxy compound. When the polyol itself does not contain a furan ring, the organic epoxy compound used must be furan oxirane. In addition, if the chain extender does not contain a certain furan ring, 2,5-dihydroxyfuran cannot be used alone. The main purpose of these furan polyols is to prepare polyurethane foams with improved properties, thereby improving their performance or optimizing their characteristics. CN116622050A relates to a low-density, wear-resistant and non-slip polyurethane sole resin, belonging to the technical field of polyurethane elastomers. The resin of the invention consists of component A, component B and a catalyst, wherein component A contains 70 to 90 parts of polyol P1, 10 to 30 parts of polyol P2, 5 to 15 parts of chain extender, 1 to 10 parts of anti-wear agent, 0.5 to 1.0 parts of silicone oil and 0.4 to 0.8 parts of foaming agent, and the sum of the mass parts of polyols P1 and P2 is 100 parts; component B contains 25 to 40 parts of polyol P1, 0 to 5 parts of polyol I1 and 55 to 75 parts of isocyanate. The amount of catalyst added is 1.5% to 2.5% of the mass of component A. The resin product has low density, low DIN wear value, and excellent wear resistance and anti-slip properties. The invention also provides a preparation method and application of the resin.

[0005] The sole material is an important type of elastomeric material. With the advancement of materials, it is of great practical significance and practical value to develop excellent engineering sole materials with high wear resistance, high oil resistance, light weight, good elasticity, high strength, antistatic, shock absorption effect, etc. for special purposes. Summary of the invention

[0006] In view of the above-mentioned defects in the prior art, the technical problem to be solved by the present invention is to provide a wear-resistant PU foam sole and a preparation process thereof.

[0007] As a material that is often subjected to wear, the wear resistance of the sole directly affects the service life of the shoe. In addition, the sole material with good wear resistance can better maintain the performance of cushioning, shock absorption, grip, etc. Therefore, it is very necessary to improve the wear resistance of polyurethane foam sole materials.

[0008] The invention provides a wear-resistant PU foamed sole. First, polyfuran polyol is prepared and then foamed with isocyanate and chain extender to obtain a sole material. Since the furan group has aromaticity, it provides additional rigidity and stability in polyurethane. This rigid structure can limit the movement of molecular chains, thereby reducing friction and wear. The aromaticity of the furan group also enhances the forces between molecules, such as π-π interaction and hydrogen bond, which can improve the mechanical strength and wear resistance of the material. The obtained foamed material has a more uniform distribution of hard segments and soft segments, and this uniform distribution helps to improve the overall mechanical properties of the material, including wear resistance. Therefore, the wear resistance of the prepared polyurethane foam material is better, and the improvement of this performance is crucial to extending the life of the sole material and maintaining the performance of the sole material.

[0009] The use environment of the sole is relatively complex, so wear resistance is not the only factor that determines its lifespan. The oil-resistant sole material can resist the erosion of grease, reduce the damage caused by grease, and also extend the service life of the sole. When the sole material of the present invention has a strong polar group, the prepared sole can also have good oil resistance, making its application range wider.

[0010] The invention prepares polyfuran polyol, mixes the polyfuran polyol with isocyanate, chain extender, auxiliary agent and the like, and obtains the PU foamed sole through water foaming, demoulding and ripening. The prepared foamed material has the characteristics of light weight, high elasticity and shock absorption. The introduction of furan groups in the polyfuran polyol can provide additional rigidity and stability, thereby improving the strength, toughness and wear resistance of the material. The addition of antioxidant can prevent the material from aging and discoloration. The addition of lubricant can reduce the friction coefficient of the elastomer and the interface. The filler is an important reinforcing material and can reduce the friction force. Therefore, the finally obtained sole has multiple properties such as wear resistance, oil resistance, shock absorption and buffer resistance, and has a longer service life.

[0011] To achieve the above object, the present invention provides a preparation process of a wear-resistant PU foam sole, comprising the following steps: S1, heating bis-(5-carboxyfurfuryl) ether and polyol to 140-150° C. under an inert atmosphere, stirring for 6-10 hours, adding 3-aminoadipic acid, continuing to heat to 160-180° C., stirring for 20-30 hours, adding dibutyltin dilaurate, polymerizing for 48-72 hours, and drying to obtain polyfuran polyol; S2. Mix polyfuran polyol with hexamethylene diisocyanate, 1,4-butanediol, water, dibutyltin dilaurate, amine catalysts and additives, and inject into a shoe mold with a mold temperature of 40-50°C. Curing and foaming for 3-5 minutes, demolding and aging to obtain a wear-resistant PU foam sole.

[0012] Furthermore, the polyol is one of 2,6-dihydroxycapronitrile, 1,5-pentanediol or 1,6-hexanediol.

[0013] Furthermore, the amine catalyst is triethylenediamine.

[0014] Furthermore, the auxiliary agent is a mixture of an antioxidant, a lubricant and a filler.

[0015] Furthermore, the aging temperature is 80-90°C.

[0016] Furthermore, the preparation process of the wear-resistant PU foam sole comprises the following steps, measured in parts by weight: S1, 1 part of bis-(5-carboxyfurfuryl) ether and 2-3 parts of polyols are heated to 140-150° C. under an inert atmosphere and mixed, 2-3 parts of 3-aminoadipic acid are added after stirring for 6-10 hours, the temperature is continued to be raised to 160-180° C., 0.001-0.005 parts of dibutyltin dilaurate are added after stirring for 20-30 hours, and the polymerization is dried after 48-72 hours to obtain polyfuran polyol, bis-(5-carboxyfurfuryl) ether is reacted with polyols as starting raw material to form an ester bond, the obtained product is continued to react with 3-aminoadipic acid to form an ester bond, dibutyltin dilaurate is used as a catalyst to catalyze the reaction process, and finally polyfuran polyol is obtained by polymerization; S2. Mix 100-150 parts of polyfuran polyol with 30-40 parts of hexamethylene diisocyanate, 3-4 parts of 1,4-butanediol, 1-2 parts of water, 0.2-0.3 parts of dibutyltin dilaurate, 0.1-0.2 parts of amine catalyst and 1-2 parts of auxiliary agent, inject into a shoe mold with a mold temperature of 40-50°C, cure and foam for 3-5 minutes, demold and mature at 80-90°C to obtain a wear-resistant PU foamed sole.

[0017] Preferably, the antioxidant is antioxidant 1076.

[0018] Preferably, the lubricant is zinc stearate.

[0019] Preferably, the filler is white carbon black.

[0020] Preferably, the mass ratio of the antioxidant, lubricant and filler in the auxiliary agent is 0.1-0.5:0.1-0.3:1-2.

[0021] The invention also provides a wear-resistant PU foamed sole, which is prepared by the method.

[0022] Beneficial effects of the present invention: 1. Compared with the prior art, the present invention provides a wear-resistant PU foamed sole. First, polyfuran polyol is prepared and then foamed with isocyanate and chain extender to obtain a sole material. Since the furan group has aromaticity, it provides additional rigidity and stability in polyurethane. This rigid structure can limit the movement of molecular chains, thereby reducing friction and wear, so the wear resistance of the prepared polyurethane foam material is better.

[0023] 2. Compared with the prior art, the sole obtained by the present invention has multiple properties such as wear resistance, oil resistance, shock absorption, and anti-buffering, and has a longer service life. BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION

[0025] Bis-(5-carboxyfurfuryl) ether, CAS No.: 76154-25-1.

[0026] Antioxidant 1076, from BASF.

[0027] Polyether polyol, model: PPG-3000, from Dow.

[0028] Example 1 A preparation process of a wear-resistant PU foam sole comprises the following steps, measured in parts by weight: S1, 1 part of bis-(5-carboxyfurfuryl) ether and 2.6 parts of 1,5-pentanediol were heated to 145° C. under a nitrogen atmosphere, stirred for 8 hours, and then 2.8 parts of 3-aminoadipic acid were added, and the temperature was continued to rise to 170° C., and after stirring for 24 hours, 0.003 parts of dibutyltin dilaurate were added, and after the polymerization was completed for 60 hours, the mixture was dried to obtain polyfuran polyol; S2. Mix 125 parts of polyfuran polyol with 35 parts of hexamethylene diisocyanate, 3.5 parts of 1,4-butanediol, 1.5 parts of water, 0.25 parts of dibutyltin dilaurate, 0.15 parts of triethylenediamine, 0.3 parts of antioxidant 1076, 0.2 parts of zinc stearate and 1 part of white carbon black, and inject into a shoe mold with a mold temperature of 45°C. Curing and foaming for 4 minutes, demolding and aging at 85°C for 24 hours to obtain a wear-resistant PU foamed sole.

[0029] Example 2 The process is substantially the same as Example 1, except that 1,5-pentanediol is replaced by 1,6-hexanediol.

[0030] Example 3 The process is substantially the same as Example 1, except that 1,5-pentanediol is replaced by 2,6-dihydroxycapronitrile.

[0031] Comparative Example 1 A preparation process of a wear-resistant PU foam sole comprises the following steps, measured in parts by weight: Mix 125 parts of polyether polyol with 35 parts of hexamethylene diisocyanate, 3.5 parts of 1,4-butanediol, 1.5 parts of water, 0.25 parts of dibutyltin dilaurate, 0.15 parts of triethylenediamine, 0.3 parts of antioxidant 1076, 0.2 parts of zinc stearate and 1 part of white carbon black, inject into a shoe mold with a mold temperature of 45°C, cure and foam for 4 minutes, demold, and mature at 85°C for 24 hours to obtain a wear-resistant PU foam sole.

[0032] Comparative Example 2 A preparation process of a wear-resistant PU foam sole comprises the following steps, measured in parts by weight: S1, 1 part of bis-(5-carboxyfurfuryl) ether and 2.6 parts of 1,5-pentanediol were heated to 145° C. under a nitrogen atmosphere, stirred for 8 hours, and then 2.8 parts of adipic acid were added, and the temperature was continued to rise to 170° C., and after stirring for 24 hours, 0.003 parts of dibutyltin dilaurate were added, and after the polymerization was completed for 60 hours, the mixture was dried to obtain polyfuran polyol; S2. Mix 125 parts of polyfuran polyol, 35 parts of hexamethylene diisocyanate, 3.5 parts of 1,4-butanediol, 1.5 parts of water, 0.25 parts of dibutyltin dilaurate, 0.15 parts of triethylenediamine, 0.3 parts of antioxidant 1076, 0.2 parts of zinc stearate and 1 part of white carbon black, and inject into a shoe mold with a mold temperature of 45°C. Curing and foaming for 4 minutes, demolding and aging at 85°C for 24 hours to obtain a wear-resistant PU foam sole.

[0033] Test Example 1 The PU foam soles prepared in the examples and control examples were tested for mechanical properties, including tensile strength, elongation at break and tear strength; Among them, the tests of tensile strength and elongation at break are carried out according to the methods in GB / T1040.1-2018 "Determination of Tensile Properties of Plastics Part 1: General Principles", and the test of tear strength is carried out according to the methods in GB / T 3903.12-2021 "Test Methods for Tear Strength of Footwear Outsoles".

[0034] Table 1 Experimental protocol Tensile strength / MPa Elongation at break / % Tear strength / kN / m Example 1 28.3 538.3 22.0 Example 2 27.8 525.6 21.3 Example 3 28.9 550.8 22.5 Comparative Example 1 20.2 467.2 16.3 Comparative Example 2 23.5 490.2 18.8 It can be seen from Table 1 that the PU foam sole material prepared by the present invention has good mechanical properties. The polyurethane foam material has a unique pore structure, which can provide good support and cushioning. When subjected to external force, the pores can deform, absorb and dissipate energy, thereby playing a role in cushioning and shock absorption.

[0035] Compared with reference example 1, reference example 1 adopts polyether polyol as soft segment, while the embodiment adopts polyfuran polyol as soft segment in polyurethane material. Soft segment is the soft part in polyurethane structure, has soft, bending and stretchable performance, plays the role of reinforcing material flexibility and elasticity in polyurethane foam. Hard segment is the rigid part in polyurethane structure, has higher strength, hardness and wear resistance. In the embodiment, polyfuran polyol is prepared and then foamed with isocyanate and chain extender to obtain sole material through water, because furan group has aromaticity, which makes it provide extra rigidity and stability in polyurethane. This rigid structure can limit the movement of molecular chain, thereby reducing friction and wear, and the aromaticity of furan group also strengthens the intermolecular force, such as π-π interaction and hydrogen bond, and these forces can improve the mechanical strength of material. And, the obtained foaming material hard segment and soft segment distribution in the embodiment are more uniform, and this uniform distribution helps to improve the overall mechanical properties of material.

[0036] Compared with Example 2, 3-aminoadipic acid is added instead of adipic acid in the preparation of polyfuran polyol. Compared with Example 2, the mechanical properties of Example 2 are also improved to a certain extent. This may be because the amino group of 3-aminoadipic acid can form additional hydrogen bonds with the carbamate structure in the polyurethane, thereby increasing the force and making the internal connection of the material tighter, so the mechanical properties are improved to a certain extent.

[0037] The foamed material prepared by the present invention has the characteristics of light weight, high elasticity, shock absorption and the like. The introduction of furan groups in polyfuran polyol can provide additional rigidity and stability, thereby improving the strength, toughness and wear resistance of the material. Therefore, the final obtained sole has multiple properties such as wear resistance, shock absorption, anti-buffering and the like, and has a longer service life.

[0038] Test Example 2 The PU foam soles prepared in the embodiments and control examples were tested for wear resistance and oil resistance. The wear resistance test was carried out according to ISO4649:2024 "Determination of the wear resistance of vulcanized rubber or thermoplastic rubber using a rotating cylindrical roller apparatus" to determine the volume wear of the sample, and the calculation formula is as follows: 𝑉𝑡=(𝑚1−𝑚2) / 𝜌×1000, 𝑉𝑡 represents the volume wear of the experimental rubber; 𝑚1 and 𝑚2 are the masses of the test rubber before and after wear, respectively; 𝜌 is the density of the experimental rubber.

[0039] The oil resistance performance refers to the method in ISO1817:2024 "Rubber, vulcanized or thermoplastic rubber. Determination of resistance to liquids". The mass change rate of the sample in the test liquid is determined by the following calculation formula: ∆𝑚100=𝑚𝑖−𝑚0 / 𝑚0×100%, where ∆𝑚100 represents the mass change rate of the sample after oil immersion, 𝑚0 is the mass of the sample before oil immersion; 𝑚𝑖 is the mass of the sample after oil immersion.

[0040] Table 2 Experimental protocol Volume wear / mm3 Quality change rate / % Example 1 89 35.2 Example 2 95 36.3 Example 3 93 25.2 Comparative Example 1 155 38.9 Comparative Example 2 121 37.6 As a material that is often subjected to wear and tear, the wear resistance of the sole directly affects the service life of the shoes. And the sole material with good wear resistance can better maintain the performances such as buffering, shock absorption and gripping. As can be seen from Table 2, the PU foam material prepared by the embodiment has a lower volume wear amount, which may be due to the polyfuran polyol prepared in the embodiment and then foamed with isocyanate and chain extender to obtain the sole material through water, because the furan group has aromaticity, which makes it provide extra rigidity and stability in polyurethane. This rigid structure can limit the movement of the molecular chain, thereby reducing friction and wear, and the aromaticity of the furan group also strengthens the intermolecular force, such as π-π interaction and hydrogen bond, and these forces can improve the mechanical strength of the material. In addition, 3-aminohexanedioic acid is added in the preparation of polyfuran polyol, and the amino group that 3-aminohexanedioic acid has can form extra hydrogen bonds with the carbamate structure in the polyurethane, thereby improving the force, making the connection inside the material tighter and more difficult to wear. Therefore, compared with the reference example, the volume wear amount of the embodiment is lower.

[0041] In daily life, the soles of shoes may come into contact with various oils and fats, such as car oil, kitchen oil, etc. If the sole material is not oil-resistant, the oil will penetrate into the sole, causing the sole to swell, deform, crack or lose elasticity, thus affecting the performance and appearance quality of the sole. In addition, oil-resistant sole materials can resist the erosion of oil and fat, reduce damage caused by oil and fat, and thus extend the service life of the sole. The mass change rate can reflect the oil absorption, swelling or dissolution of the material in the oil. An increase in mass usually means that the material has absorbed the oil, while a decrease in mass may mean that some components in the material have dissolved in the oil. The smaller the mass change rate, the better the oil resistance of the material.

[0042] Compared with other embodiments and control examples, Example 3 has a smaller mass change rate. This may be because the polyol 2,6-dihydroxyhexanenitrile in Example 3 has a strong polar group, the nitrile group. The strong polarity enables the material containing the nitrile group to form a certain interaction with the oil molecules, thereby stabilizing the structure of the material and reducing the erosion and swelling of the material by the oil. Therefore, Example 3 performs best in oily liquids and has the lowest mass change rate.

[0043] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A preparation process of a wear-resistant PU foam sole, characterized in that: The steps include: S1, heating bis-(5-carboxyfurfuryl) ether and polyol to 140-150° C. under an inert atmosphere, stirring for 6-10 hours, adding 3-aminoadipic acid, continuing to heat to 160-180° C., stirring for 20-30 hours, adding dibutyltin dilaurate, polymerizing for 48-72 hours, and drying to obtain polyfuran polyol; S2. Mix polyfuran polyol with hexamethylene diisocyanate, 1,4-butanediol, water, dibutyltin dilaurate, amine catalysts and additives, and inject into a shoe mold with a mold temperature of 40-50°C. Curing and foaming for 3-5 minutes, demolding and aging to obtain a wear-resistant PU foam sole.

2. The preparation process of the wear-resistant PU foam sole according to claim 1, characterized in that: The polyol is one of 2,6-dihydroxycapronitrile, 1,5-pentanediol or 1,6-hexanediol.

3. The preparation process of the wear-resistant PU foam sole according to claim 1, characterized in that: The amine catalyst is triethylenediamine.

4. The preparation process of the wear-resistant PU foam sole according to claim 1, characterized in that: The auxiliary agent is a mixture of an antioxidant, a lubricant and a filler.

5. The preparation process of the wear-resistant PU foam sole according to claim 1, characterized in that: The aging temperature is 80-90°C.

6. The preparation process of the wear-resistant PU foamed sole according to claim 4, characterized in that: The antioxidant is antioxidant 1076.

7. The preparation process of the wear-resistant PU foamed sole according to claim 4, characterized in that: The lubricant is zinc stearate.

8. The process for preparing the wear-resistant PU foamed sole according to claim 4, characterized in that: The filler is white carbon black.

9. The process for preparing the wear-resistant PU foamed sole according to claim 4, characterized in that: The mass ratio of the antioxidant, lubricant and filler is 0.1-0.5:0.1-0.3:1-2.

10. A wear-resistant PU foam sole, characterized in that: Prepared by the process described in any one of claims 1 to 9.