Injection grade sbs material, its preparation method and application as ultra-wear resistant high slip resistant sole material

Abstract

The application discloses a kind of injection molding grade SBS materials and preparation method and as ultra-wear-resistant high skid-resistant shoe sole material application, belong to thermoplastic elastomer technical field.Injection molding grade SBS material has the following structural expression formula: S1BS2;Wherein, S1 and S2 are styrene homopolymer block, B is polybutadiene block;The total mass of S1 and S2 is 15~25% of S1BS2 mass;The number of 1,2-polymerization structure unit in B accounts for 40%~70%;The number average molecular weight of S1BS2 is 8~140,000;It has good flow and excellent ultra-wear-resistant performance, skid-resistant performance and lower glass transition temperature, and it can be prepared by injection molding to prepare shoe sole, obtain the shoe sole with good wear resistance, skid resistance, low temperature resistance.

Description

Technical Field

[0001] This invention relates to an SBS material, specifically an injection-molding grade SBS material, its preparation method, and an application of an SBS material as an ultra-wear-resistant and highly slip-resistant shoe sole material, belonging to the field of thermoplastic elastomer technology. Background Technology

[0002] The footwear industry is an indispensable part of people's daily lives. In recent years, the use of vulcanized rubber and PVC as shoe soles has greatly decreased, replaced by polyurethane and thermoplastic elastomers (TPRs). Internationally, efforts are underway to adopt TPRs in the footwear industry, replacing other polymer raw materials. TPR footwear materials are a new type of polymeric footwear material produced primarily from thermoplastic elastomer SBS. Since its first appearance at the International Footwear Exhibition in Pilmasens, Germany in 1976, its development has been rapid. Currently, in developed countries and regions such as the United States and Western Europe, this material accounts for more than 40% of footwear materials, gradually replacing traditional rubber and PVC soles.

[0003] TPR (Total Resin) is lightweight, comfortable, highly elastic, easy to dye, breathable, and strong. It is particularly excellent in low-temperature resistance, has a high coefficient of friction, and strong grip, making it a promising shoe material. One of the main reasons for TPR's rapid development abroad is its significant energy-saving effect, meeting the needs of today's energy-constrained society. Additionally, its processing technology is simple and highly mechanized, saving labor costs. Its low density, slip resistance, and comfortable feel allow it to be used in both casual and high-end fashion shoes. However, existing SBS grades also have some drawbacks: poor abrasion resistance and heat resistance; high grip on the ground; and under harsh wearing conditions, high heat generation, leading to rapid sole wear and discomfort.

[0004] Chinese patent (publication number: CN107236101A) discloses a styrene-butadiene copolymer, its preparation method, and its application in shoe soles. The styrene-butadiene copolymer has polystyrene blocks at both ends and random styrene-butadiene copolymer blocks in the middle. Compared with traditional styrene-butadiene rubber polymers, it has suitable hardness, and its tear strength and abrasion resistance are significantly improved. It can be used to prepare shoe soles with suitable hardness, high tear strength, and excellent abrasion resistance. According to the disclosed data, the DIN abrasion wear is ≥100mm³.

[0005] Chinese patent (publication number: CN113736041B) discloses a styrene-based elastomer, its preparation method, and its application as a wear-resistant and non-slip shoe sole material. It improves upon existing technology by adding a method for controlling ethylene branch chains, effectively increasing the non-slip coefficient, resulting in a shoe sole that balances wear resistance and non-slip properties, with a DIN abrasion ≥100mm³, a dry slip coefficient ≥0.6, and a wet slip coefficient ≥0.4.

[0006] Although the styrene-based thermoplastic elastomers prepared by the two publicly disclosed patent technologies have excellent DIN abrasion, they still lag behind vulcanized rubber outsoles with a DIN abrasion of ≤80mm³ and cannot be effectively replaced. In addition, the addition of some random polystyrene segments in the middle section increases rigidity and steric hindrance, resulting in poorer flexibility of the soft chain segments in the middle section. Compared with conventional SBS, the glass transition temperature is significantly increased, and the prepared soles are more sensitive to temperature. They will harden at low temperatures (<0℃). These products are more suitable for indoor slipper soles and are difficult to adapt to the low-temperature outdoor environment in winter. Summary of the Invention

[0007] To address the technical issues in existing styrene-based elastomer SBS preparation technologies, such as high wear rate, inability to replace vulcanized rubber, and inability to meet low-temperature environmental requirements:

[0008] The first objective of this invention is to provide an injection-grade SBS material that, on the one hand, has good flowability with a melt index of 6~10g / 10min (200℃, 5Kg), which meets the production efficiency requirements of disc injection molding; on the other hand, it has super wear resistance with a DIN abrasion ≤80mm³; on the third hand, it has excellent anti-slip properties, with a dry slip coefficient ≥0.6 and a wet slip coefficient ≥0.4; and on the fourth hand, it has a low glass transition temperature, so the sole will not harden at low temperatures, thus not affecting wearing comfort.

[0009] The second objective of this invention is to provide a method for preparing injection-molded SBS material, which can be synthesized using existing mature anionic polymerization processes. This method is simple to operate, controllable, low in cost, and meets the requirements of industrial production.

[0010] The third objective of this invention is to provide an application of injection-grade SBS material, which, based on its good fluidity, excellent wear resistance, anti-slip properties, and low glass transition temperature, can be used to prepare shoe soles through injection molding, thereby obtaining shoe soles with excellent wear resistance, anti-slip properties, and low-temperature resistance.

[0011] To achieve the above-mentioned technical objectives, the present invention provides an injection-molded grade SBS material having the following structural expression: S1BS2; wherein S1 and S2 are styrene homopolymer blocks, and B is a polybutadiene block; the total mass of S1 and S2 is 15-25% of the mass of S1BS2; and the number of 1,2-polymer structural units in B accounts for 40-70%.

[0012] The key to the S1BS2 of this invention lies in the microscopic design of its molecular structure. It features long polybutadiene blocks with a high proportion of 1,2-polymer structural units within these blocks. This structure gives S1BS2 excellent flowability, superior abrasion resistance, anti-slip properties, and a low glass transition temperature. It is well known that rubber outsoles have the best abrasion resistance because rubbers such as butadiene or natural rubber have relatively regular molecular chains, good flexibility, low hysteresis and heat generation, and high elasticity and low-temperature resistance. Therefore, downstream SBS shoe sole manufacturers often incorporate butadiene and natural rubber into their formulations to improve abrasion resistance. However, as the proportion of these blends increases, the elastic effect of the melt increases, and the flowability decreases significantly, making processing difficult. The key to improving the abrasion resistance of SBS in this application lies in increasing the proportion of butadiene units in the rubber phase of the SBS copolymer. Numerous experiments have shown that when the molecular weight of the polystyrene phase region, which forms micro-regions of polystyrene blocks, is above 8000, the abrasion resistance gradually increases with the increase of butadiene content. For example, when the total mass proportion of styrene blocks is 24%, the DIN abrasion is ≤80mm³. In addition, the styrene content determines the hardness of SBS. When the content is 24%, the hardness is about 63±3 Shore A, which is the suitable hardness range for shoe soles (50~70 Shore A). At the same time, the butadiene blocks in S1BS2 have a high proportion and a high content of vinyl branches, which can give it good fluidity and meet the requirements of injection molding.

[0013] As a preferred option, the total mass of S1 and S2 is 18-22% of the mass of S1BS2.

[0014] As a preferred embodiment, the 1,2-polymer structural units in component B comprise 50-60%. Increasing the content of 1,2-polymer structural units in the polybutadiene chain leads to decreased molecular chain flexibility, increased hysteresis heat generation, and a significantly higher glass transition temperature (e.g., Figure 1 The DSC curve of S1BS2 prepared in Example 3 shows that its glass transition temperature is approximately -70°C, but this is far less significant than the improvement achieved by adding rigid styrene segments to the middle section (e.g., ...). Figure 2The DSC curve of the styrene-containing block copolymer is shown. Its glass transition temperature is about -10℃. The surface of the S1BS2 polymer with high 1,2-polymer structural units can form a micro-"uneven" structure, which manifests as a "physical suction cup" effect when the polymer comes into contact with the ground, thus improving the anti-slip performance. Moreover, the anti-slip coefficient increases with the increase of the content of polybutadiene 1,2-polymer structural units.

[0015] As a preferred option, the number-average molecular weight of S1BS2 is 95,000 to 110,000. The purpose of controlling the molecular weight of S1BS2 is mainly to balance the polymer's processability (characterized by melt flow index) and tensile strength. If the molecular weight is low, the melt flow index will increase, resulting in excellent processability, but low tensile strength; if the molecular weight is high, the melt flow index will decrease, resulting in poorer processability, but tensile strength will be improved to some extent. Numerous experiments have shown that by controlling the styrene block ratio and simultaneously controlling the number-average molecular weight to be between 80,000 and 140,000, and further optimizing the number-average molecular weight to be between 100,000 and 110,000, SBS with a melt flow index of 6 to 10 g / 10 min and a tensile strength ≥ 8 MPa can be obtained, meeting the requirements of injection molding processes for shoe soles.

[0016] The present invention also provides a method for preparing injection-molded SBS material. The method involves adding styrene monomer and initiator to an anionic polymerization solution system containing structure modifier, activator and initiator to initiate a first-stage polymerization, then adding butadiene monomer to carry out a second-stage polymerization, then adding styrene monomer to carry out a third-stage polymerization, and finally terminating the polymerization reaction after the polymerization is completed to obtain the desired product.

[0017] As a preferred embodiment, the activator comprises tetrahydrofuran. As a preferred embodiment, the concentration of the activator in the anionic polymerization solution system is 180-250 mg / L. The activator primarily enhances the polymerization activity of the monomer.

[0018] As a preferred embodiment, the structure modifier comprises bis(tetrahydrofurfuryl)propane. As a preferred embodiment, the concentration of the structure modifier in the anionic polymerization solution system is 40-75 mg / L. The structure modifier is mainly used to adjust the mass ratio of 1,2-polymer structural units in the butadiene block, and is preferably the highly active bis(tetrahydrofurfuryl)propane. The amount added is used to control the mass ratio of 1,2-polymer structural units in the butadiene block within the desired range.

[0019] As a preferred embodiment, the conditions for the single-stage polymerization are: temperature of 60~70℃, pressure of 0.1~0.5MPa, and time of 20~40min.

[0020] As a preferred embodiment, the conditions for the two-stage polymerization are: an initial temperature of 55~60℃, a maximum temperature not exceeding 80℃, and a time of 25~35min.

[0021] As a preferred embodiment, the conditions for the three-stage polymerization are: maintaining the reaction temperature of the two-stage polymerization reaction for a further reaction time of 15-25 minutes.

[0022] The present invention also provides an application of injection-molded SBS material as a shoe sole material.

[0023] As a preferred embodiment, the injection-grade SBS material is used to prepare ultra-wear-resistant and highly slip-resistant shoe soles.

[0024] Compared with the prior art, the advantages of the technical solution of the present invention are as follows:

[0025] (1) The SBS material of the present invention improves the wear resistance of the product by increasing the proportion of polybutadiene rubber phase in SBS based on the wear-resistant properties of rubber, and the effect is significant.

[0026] (2) The SBS of the present invention controls the content of branched 1,2-structure of polybutadiene segments by adding the amount of structure regulator, so that the product has excellent anti-slip properties.

[0027] (3) The SBS material of the present invention can meet the requirements of injection molding shoe sole process by adjusting the molecular weight to take into account both processability and tensile strength.

[0028] (4) The SBS material of the present invention has the characteristics of high fluidity, super wear resistance and high slip resistance, which is very suitable for replacing vulcanized rubber outsoles and can be used in lightweight TPR shoe soles and various casters to greatly improve wear resistance and has good market prospects. Attached Figure Description

[0029] Figure 1 The DSC curve of SBS synthesized in Example 3 (glass transition temperature -69.21℃) is shown.

[0030] Figure 2 The image shows the DSC curve (glass transition temperature -8.68℃) of the styrene-containing block copolymer in the middle segment. Detailed Implementation

[0031] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0032] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0033] In the following embodiments, unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0034] In the following examples, the number-average molecular weight Mn was determined by gel permeation chromatography, the content of 1,2-structure butadiene units in the polybutadiene segments was determined by nuclear magnetic resonance, the mechanical properties were determined according to GB / T 528-2009, the DIN abrasion was tested according to GB / T9867-2008, and the anti-slip performance was tested according to HG / T3780-2005.

[0035] Examples 1-4

[0036] An anionic polymerization method was used. In a 5L polymerization reactor that had been dried and purged with nitrogen, 2500mL of cyclohexane solvent, 117mg of bis(tetrahydrofuran)propane, 585mg of tetrahydrofuran, and 192mg of butyllithium were added. The polymerization reactor temperature was maintained at 65℃ and the pressure at 0.3MPa. First, styrene monomer (mass m1) was added and reacted for 30min. Then, the polymerization temperature was lowered to 60℃, and butadiene monomer (mass m2) was slowly added. The second-stage reaction was controlled at a high temperature of 80℃ and held for 20min. Finally, the third-stage styrene monomer (mass m3) was added, and the reaction was continued for 30min. Then, 1mL of ethanol terminator was added. After coagulation and precipitation, the finished product was obtained.

[0037] Tables 1 and 2 are the raw material addition amounts and SBS product performance test tables, respectively.

[0038]

[0039]

[0040] As can be seen from Examples 1-4, in the synthesized SBS, as the mass proportion of styrene blocks increases, the tensile strength continuously increases, the elongation at break continuously decreases, the melt flow index continuously decreases, and the wear gradually increases. However, even when the styrene content is 24%, its DIN wear is still <60mm³, showing excellent wear resistance. The anti-slip properties show a downward trend, which is mainly due to the smaller contact area between the specimen and the friction surface after the hardness is increased.

[0041] Examples 5-9

[0042] Performance comparison of SBS with different contents of 1,2-polymer structural units in polybutadiene segments.

[0043] The content of different 1,2-polymer structural units in the polybutadiene chain segment is controlled by the amount of structure modifier added, and increases with the increase of the amount of structure modifier added.

[0044] An anionic polymerization method was used. In a 5L polymerization reactor purged with dry nitrogen, 2500 mL of cyclohexane, m4 of bis(tetrahydrofuran)propane, 585 mg of tetrahydrofuran, and 192 mg of butyllithium were added. The reactor temperature was maintained at 65℃ and the pressure at 0.3 MPa. First, 33 g of styrene monomer was added, and the reaction was allowed to proceed for 30 min. Then, the polymerization temperature was lowered to 60℃, and 234 g of butadiene monomer was slowly added. The second-stage reaction was controlled at a high temperature of 80℃ and held for 20 min. Finally, 33 g of styrene monomer was added for the third stage, and the reaction was continued for 30 min. Then, 1 mL of ethanol was added as a terminator. After coagulation and precipitation, the finished product was obtained. Table 3 shows the SBS performance test results for different contents of 1,2-polymer structural units in the polybutadiene segments.

[0045]

[0046] As can be seen from Examples 5-8, in the synthesized SBS, as the content of 1,2-polymerized butadiene units in the polybutadiene segments increases, the tensile strength melt index and hardness do not change much, the wear gradually increases, and the anti-slip properties are significantly improved.

[0047] Examples 9-12

[0048] The performance of SBS with different molecular weights was compared. The molecular weight was adjusted by the amount of butyllithium added. More butyllithium added resulted in a lower molecular weight, while less butyllithium added resulted in a higher molecular weight.

[0049] Anionic polymerization was employed. In a 5L polymerization reactor purged with dry nitrogen, 2500 mL of cyclohexane, 117 mg of bis(tetrahydrofuran)propane, 585 mg of tetrahydrofuran, and 5 mL of butyllithium were added. The reactor temperature was maintained at 65°C and the pressure at 0.3 MPa. First, 33 g of styrene monomer was added, and the reaction was allowed to proceed for 30 min. Then, the polymerization temperature was lowered to 60°C, and 234 g of butadiene monomer was slowly added. The second-stage reaction was maintained at a high temperature of 80°C for 20 min. Finally, 33 g of the third-stage styrene monomer was added, and the reaction continued for 30 min. Then, 1 mL of a terminator was added. After coagulation and precipitation, the final product was obtained. Table 4 shows the performance test results of SBS with different molecular weights.

[0050]

[0051] As can be seen from Examples 9-12, when the styrene content is 22% and the content of 1,2-polymer structural units in the polybutadiene segments is about 43%, as the molecular weight increases, the melt index gradually decreases, the processability deteriorates, the tensile strength gradually increases, the wear gradually decreases, and the anti-slip property gradually deteriorates.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An injection molding grade SBS material, characterized in that: It has the following structure expression: S1BS2; in, S1 and S2 are styrene homopolymer blocks, and B is a polybutadiene block; The total mass of S1 and S2 is 15-25% of the mass of S1BS2; In component B, 1,2-polymer structural units account for 40% to 70%; The number-average molecular weight of S1BS2 is 80,000 to 140,000.

2. The injection-molding grade SBS material according to claim 1, characterized in that: The total mass of S1 and S2 is 18-22% of the mass of S1BS2.

3. The injection-molding grade SBS material according to claim 1, characterized in that: In component B, 1,2-polymer structural units account for 50-60%.

4. The injection-molding grade SBS material according to claim 1, 2 or 3, characterized in that: The number-average molecular weight of S1BS2 is 95,000 to 110,000.

5. A method for preparing an injection-molding grade super SBS material according to any one of claims 1 to 4, characterized in that: In an anionic polymerization solution system containing a structure modifier, an activator, and an initiator, styrene monomer and an initiator are first added to initiate a first-stage polymerization, then butadiene monomer is added to initiate a second-stage polymerization, and then styrene monomer is added to initiate a third-stage polymerization. After the polymerization is completed, the polymerization reaction is terminated to obtain the final product.

6. The method for preparing an injection-molding grade SBS material according to claim 5, characterized in that: The activator includes tetrahydrofuran; The concentration of the activator in the anionic polymerization solution system is 180~250 mg / L.

7. The method for preparing injection-molding grade SBS material according to claim 5, characterized in that: The structure modifier includes bis(tetrahydrofurfuryl)propane; The concentration of the structure modifier in the anionic polymerization solution system is 40~75 mg / L.

8. The method for preparing an injection-molding grade SBS material according to claim 5, characterized in that: The conditions for the polymerization step are: temperature 60~70℃, pressure 0.1~0.5MPa, and time 20~40min; The conditions for the two-stage polymerization are: an initial temperature of 55~60℃, a maximum temperature not exceeding 80℃, and a time of 25~35min.

9. The conditions for the three-stage polymerization are: maintaining the reaction temperature of the two-stage polymerization reaction for a further reaction time of 15-25 minutes; The application of the injection-molding grade SBS material according to any one of claims 1 to 4 is characterized in that: Application as a material for shoe soles.

10. The application of an injection-molding grade SBS material according to claim 9, characterized in that: Used to manufacture ultra-wear-resistant and highly slip-resistant shoe soles.

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