A diblock styrene-butadiene copolymer, its preparation method, and its application in transparent vulcanized shoe soles.

Abstract

This invention discloses a diblock styrene-butadiene copolymer, its preparation method, and its application in transparent vulcanized shoe soles. The diblock styrene-butadiene copolymer is composed of styrene homopolymer blocks and styrene-butadiene random copolymer blocks. The preparation method involves adding a mixture of styrene and butadiene monomers to an anionic polymerization system for random copolymerization, followed by adding styrene monomers for homopolymerization. After homopolymerization is completed, the polymerization is terminated to obtain the desired product. When used in vulcanized shoe soles, this diblock styrene-butadiene copolymer can achieve a light transmittance of over 80% and excellent abrasion resistance and tear resistance.

Description

Technical Field

[0001] This invention relates to a styrene-butadiene copolymer, its preparation method, and its application. Specifically, it relates to a diblock styrene-butadiene copolymer composed of styrene homopolymer blocks and styrene-butadiene random copolymer blocks, its preparation method, and the application of the diblock styrene-butadiene copolymer in transparent vulcanized shoe soles, belonging to the field of styrene-butadiene rubber synthesis technology. Background Technology

[0002] In recent years, materials used to make transparent shoe soles include TPU, EPDM, and rubber. Patents related to TPU as a transparent shoe sole material include CN109370197A "High-molecular-weight transparent rubber material for shoe soles and its preparation method and shoe", and CN106279618A "A method for manufacturing a transparent polyurethane shoe sole". These documents show that transparent shoe soles made of TPU have advantages such as good wear resistance, resilience, and impact resistance, but also suffer from problems such as poor resistance to yellowing, poor wet slip resistance and shock absorption, and high hardness. Patents related to EPDM vulcanized transparent shoe soles include CN107603033A "A highly transparent EPDM rubber shoe sole and its manufacturing method". These documents show that EPDM material, as a vulcanized transparent shoe sole material, has advantages such as good weather resistance and transparency, but also suffers from problems such as incompatibility with other rubbers, high cost, difficulty in processing, poor adhesion to other parts of the shoe sole, and a tendency to "come apart". Transparent vulcanized rubber soles, made by blending solution-polymerized styrene-butadiene rubber (SBR) with other rubbers, offer advantages such as high filling capacity, high light transmittance, good tactile feel, smooth surface, clear tread pattern, resistance to deformation, moderate hardness, and good elasticity. However, the rubbers used in vulcanized rubber soles, such as butadiene and isoprene rubber, are conventional grades with relatively fixed structures and properties. Therefore, the transparency and overall performance of the sole depend on the structure of the SBR. Currently, it is difficult to obtain soles that combine high transparency, excellent surface gloss, and superior abrasion and tear resistance after vulcanization using SBR blends with SBR and isoprene rubber. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the first objective of this invention is to provide a diblock styrene-butadiene copolymer composed of a styrene homopolymer segment and a polystyrene-butadiene random copolymer segment. This diblock styrene-butadiene copolymer has a two-segment structure consisting of a styrene homopolymer segment and a polystyrene-butadiene random copolymer segment. The polystyrene-butadiene random copolymer segment has a high styrene unit content, with styrene units randomly distributed within the copolymer segment, and a moderate vinyl side group content. The short styrene homopolymer segment improves the gloss and strength of the product without affecting the wear resistance of the vulcanized outsole. When used in vulcanized shoe outsoles, it can produce vulcanized shoe outsoles with high transparency (light transmittance exceeding 80%) and excellent wear resistance and tear resistance.

[0004] The second objective of this invention is to provide a method for preparing diblock styrene-butadiene copolymers, which is simple to operate, low in cost, and conducive to large-scale production.

[0005] The third objective of this invention is to provide an application of a diblock styrene-butadiene copolymer, which, through mixing and vulcanization with butadiene rubber and other materials, can achieve a transparent vulcanized outsole with high transparency, achieving a light transmittance of over 80% and excellent wear resistance and tear resistance.

[0006] The present invention provides a diblock styrene-butadiene copolymer, wherein the diblock styrene-butadiene copolymer is composed of styrene homopolymer segments and styrene-butadiene random copolymer segments; the cyclohydrogen ratio of the benzene ring in the diblock styrene-butadiene copolymer is 3.0 to 6.0, and the proportion of poly(1,2) structural units in the butadiene units of the diblock styrene-butadiene copolymer is 26% to 40%.

[0007] The benzene ring hydrogen ratio of the diblock styrene-butadiene copolymer of the present invention reflects the randomness of the copolymer, and the preferred range of the benzene ring hydrogen ratio is 3.5 to 6.0, which is beneficial to balance improving the transparency of the product without losing the good wear resistance and tear resistance of the vulcanized outsole.

[0008] As a preferred embodiment, the diblock styrene-butadiene copolymer has a molecular weight of 5.0 × 10⁻⁶. 4 ~2.0×10 5 As a preferred embodiment, the mass ratio of styrene units to butadiene units in the diblock styrene-butadiene copolymer is 30:70 to 60:40; more preferably, it is 40:60 to 50:50. The mass percentage content of styrene units in the random copolymer blocks of the diblock styrene-butadiene copolymer is 30% to 50%; more preferably, it is 30% to 40%.

[0009] The present invention also provides a method for preparing a diblock styrene-butadiene copolymer, wherein in an anionic polymerization system, a mixture of styrene and butadiene monomers is first added for random copolymerization, and then styrene monomer is added for homopolymerization. After homopolymerization is completed, the polymerization is terminated to obtain the copolymer.

[0010] As a preferred embodiment, the total mass ratio of styrene monomer to butadiene monomer in the random copolymerization and homopolymerization process is 30:70 to 60:40, and more preferably 40:60 to 50:50.

[0011] As a preferred embodiment, the mass percentage content of styrene monomer in the styrene and butadiene mixed monomers during random copolymerization is 30-50%; more preferably 30-40%.

[0012] The diblock styrene-butadiene copolymer provided by this invention has a high styrene content, which can improve the processing performance of the compound, reduce the agglomerate size of the rubber, and give the vulcanized product high light transmittance. Most of the styrene units need to be randomly distributed in the rubber segments because the formation of styrene unit blocks would reduce the abrasion resistance of the sole and increase heat generation. Retaining a small portion of styrene blocks improves the demolding effect of the product and gives the product surface excellent gloss. By balancing these two aspects, a good equilibrium can be achieved, improving the transparency of the vulcanized product without sacrificing the superior abrasion resistance, tear resistance, and other properties of the vulcanized sole.

[0013] As a preferred embodiment, the anionic polymerization system comprises a nonpolar hydrocarbon solvent, a polar structure modifier, and an initiator.

[0014] As a preferred embodiment, the initiator is n-butyllithium, and the amount added is 0.02wt% to 0.1wt% of the total mass of the anionic polymerization system. The amount of n-butyllithium added is determined according to the molecular weight of the designed polymer.

[0015] As a preferred embodiment, the activity modifier comprises one or more of tetrahydrofuran, diethyl ether, ethyl methyl ether, anisole, diphenyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofurfuryl ethyl ether, bis(tetrahydrofurfuryl propane), triethylamine, hexamethylphosphonic triamine, and tetramethylethylenediamine. More preferably, the activity modifier is at least one of tetrahydrofurfuryl ethyl ether or bis(tetrahydrofurfuryl propane) and tetrahydrofuran. More preferably, the mass ratio of the two is 1:10 to 1:5.

[0016] As a preferred embodiment, the nonpolar hydrocarbon solvent includes one or more of pentane, hexane, octane, heptane, and cyclohexane. A further preferred nonpolar hydrocarbon solvent is cyclohexane.

[0017] As a preferred embodiment, the styrene and butadiene mixed monomers are added slowly and uniformly. The addition time of the styrene and butadiene mixed monomers is controlled within the range of 30 to 90 minutes.

[0018] As a preferred embodiment, the random copolymerization temperature is between 70 and 80°C. The randomness of the styrene-butadiene copolymerization can be improved to some extent by controlling the slow and uniform addition of the styrene and butadiene mixed monomers.

[0019] As a preferred embodiment, the homopolymerization temperature is between 60 and 70°C.

[0020] This invention also provides an application of a diblock styrene-butadiene copolymer in the preparation of highly transparent vulcanized shoe soles.

[0021] The specific process for preparing shoe soles using the diblock styrene-butadiene copolymer provided by this invention is as follows: Butadiene rubber, the diblock styrene-butadiene copolymer, silica, processing oil, stearic acid, antioxidant, crosslinking agent, and other raw materials are mixed in a Banbury mixer in a certain mass ratio, except for the crosslinking agent. The outlet temperature is 130℃. After the mixed rubber sheet is passed through a thin pass, the crosslinking agent is added, and the sheet is passed through three times. The roller gap is then adjusted to approximately 2.5mm, and the sheet is cut. Finally, it is vulcanized for 5 minutes on a flat vulcanizing machine at 165℃.

[0022] Compared with existing technologies, the beneficial technical effects of the present invention are as follows:

[0023] The diblock styrene-butadiene copolymer provided by this invention is composed of polystyrene homopolymer blocks and polystyrene random copolymer blocks. The polystyrene random copolymer blocks have a high styrene unit content and the styrene units are randomly distributed in the copolymer blocks. The vinyl side group content is moderate. When used to prepare vulcanized shoe outsoles, vulcanized shoe outsoles with high transparency (light transmittance of more than 80%) and excellent wear resistance and tear resistance can be obtained.

[0024] The preparation method of the diblock styrene-butadiene copolymer provided by this invention is simple to operate, low in cost, and conducive to large-scale production.

[0025] The present invention provides a transparent vulcanized shoe outsole with high transparency, light transmittance of over 80%, and excellent wear resistance and tear resistance by mixing and vulcanizing a diblock styrene-butadiene copolymer with cis-butadiene rubber and fillers. Attached Figure Description

[0026] 【 Figure 1 [Image 1] is the proton NMR spectrum of the copolymer obtained in Example 1 of this invention.

[0027] 【 Figure 2 [Image 1] is the proton NMR spectrum of the copolymer obtained in Comparative Example 1 of this invention.

[0028] 【 Figure 3 [Image showing DMA comparison curves for Embodiment 3, Comparative Example 4, and Comparative Example 5 of the present invention] Detailed Implementation

[0029] The following embodiments are further illustrations of the present invention, and not limitations thereof.

[0030] In this invention, the molecular weight and distribution of the polymer can be determined by GPC chromatography according to the GB / T 21836 standard.

[0031] The random distribution of styrene in butadiene and the content of 1,2 polymeric structures were determined by nuclear magnetic resonance spectroscopy (H-NMR): Bruker AVANCE NEO-400 NMR spectrometer, with CDCl3 as solvent, and the analysis was performed according to GB / T 28728.

[0032] The glass transition temperature (Tg) of the sample was determined using a DSC 25 differential thermal analyzer from TA Instruments, with a heating rate of 10 °C / min and a test temperature range of -80 to 40 °C.

[0033] Mooney viscosity was determined using the Taiwan High Speed ​​Rail MVD-3000A, at 100℃, after preheating for 1 minute and testing for 4 minutes, to obtain the lowest Mooney viscosity of the sample.

[0034] Transmittance and haze of vulcanized sheets: Tested using a Shanghai Jingke WGT-2S transmittance and haze meter.

[0035] Dynamic mechanical property testing: Dynamic thermomechanical analyzer TA Instruments DMA3300.

[0036] Example 1

[0037] In a 5L jacketed stainless steel polymerization reactor purged with nitrogen, 2500mL of purified cyclohexane was introduced, along with 0.39g THF, 78mg tetrahydrofurfuryl ethyl ether, and 2.7mmol n-butyllithium, and stirred. The mixture was heated to 70-80℃ using hot water in the jacket. 105g of premixed styrene and 162g of butadiene were added to the polymerization reactor, with the feeding time controlled at 40min. The polymerization reaction proceeded. After 30min at high temperature, the monomers were essentially fully reacted. Then, 33g of styrene was added to continue the polymerization reaction. The reaction was continued for another 30min until the monomers were fully reacted and the conversion rate was greater than 99%. Finally, 0.13g of ethanol was added to terminate the polymerization reaction. The polymer solution was discharged from the polymerization reactor, and 0.75g of antioxidant 1076 and 0.75g of antioxidant 168 were added and stirred until homogeneous. After water precipitation and coagulation, the mixture was dried to obtain the polymer dry gel. GPC and Mooney test results are shown in Table 1, and 1H NMR analysis results are shown in Table 2. (Spectra are shown in...) Figure 1 .

[0038] Comparative Example 1

[0039] In a 5L jacketed stainless steel polymerization reactor purged with nitrogen, 2500mL of purified cyclohexane was introduced, along with 0.39g THF, 78mg tetrahydrofurfuryl ethyl ether, and 2.7mmol n-butyllithium, and stirred. The mixture was heated to 70-80℃ using hot water in the jacket, and 33g styrene was added. After 30 minutes of polymerization, the monomers were basically completely reacted. Then, 105g of premixed styrene and 162g butadiene were added, and polymerization continued. After 30 minutes of high-temperature polymerization to ensure complete monomer reaction, 0.13g ethanol was added to terminate the polymerization. The polymer solution was discharged from the polymerization reactor, and 0.75g antioxidant 1076 and 0.75g antioxidant 168 were added and stirred until homogeneous. After water precipitation and coagulation, the polymer was dried to obtain a dry polymer. GPC and Mooney test results are shown in Table 1, and 1H NMR analysis results are shown in Table 2. The spectra are shown in […]. Figure 2 .

[0040] Table 1 GPC Analysis Structure

[0041] Mw Mn Mw / Mn <![CDATA[ML 1+4 100 ]]> Example 1 11.9 11.6 1.03 45 Comparative Example 1 11.6 11.3 1.03 47

[0042] Table 2. Results of NMR Spectrum Analysis

[0043] Vinyl structure content / % benzene ring hydrogen ratio Example 1 29.9 3.42 Comparative Example 1 25.6 1.56

[0044] The randomness of styrene units in the polymer chain is calculated by the ratio of the peak areas of the absorption peaks at δ=7.09 and δ=6.56 in the 1H NMR spectrum (the hydrogen ratio of the benzene ring). The larger this ratio is, the greater the degree of random distribution of styrene in the solution-polymerized styrene-butadiene polymer chain.

[0045] As can be seen from the 1H NMR spectroscopy analysis results in Table 2, the two-stage feeding sequence method of this invention can achieve a higher vinyl structure content and a better degree of styrene random distribution under the same other process conditions.

[0046] Example 2

[0047] In a 5L jacketed stainless steel polymerization reactor purged with nitrogen, 2500mL of purified cyclohexane was introduced, along with 0.39g THF, 59mg bis(tetrahydrofurfuryl)propane, and 2.7mmol n-butyllithium, and the mixture was stirred. The temperature was raised to 70-80℃ using hot water in the jacket. 105g of premixed styrene and 162g of butadiene were then added to the polymerization reactor, with the feeding time controlled at 40min. The polymerization reaction was allowed to proceed until the monomers were largely reacted. Then, 33g of styrene was added to continue the polymerization. Once the monomers had completely reacted, 0.13g of ethanol was added to terminate the polymerization. The resulting polymer solution was collected, and 0.75g of antioxidant 1076 and 0.75g of antioxidant 168 were added and stirred until homogeneous. After water precipitation and coagulation, the mixture was dried to obtain the polymer dry gel. The 1H NMR and Tg analysis results are shown in Table 3.

[0048] Comparative Examples 2-3

[0049] The experimental procedures for Comparative Examples 2 and 3 were the same as those for Example 2, except that the type of regulator added was changed. Comparative Example 2 was modified with a single regulator, bis(tetrahydrofurfuryl)propane, and Comparative Example 3 was modified with a single regulator, THF. The 1H NMR spectrum and Tg analysis results of the synthesized styrene-butadiene polymers are shown in Table 3.

[0050] Table 3. Results of NMR and DSC analyses

[0051]

[0052] As can be seen from the NMR and DSC analysis results in Table 3, the polymerization reaction using the composite regulator of the present invention can achieve a higher vinyl structure content and a better degree of styrene random distribution under the same process conditions.

[0053] Example 3

[0054] Compound formulation: 25 parts butadiene rubber; 15 parts styrene-butadiene polymer sample from Example 2; 20 parts ultrafine silica; 15 parts processing oil; 0.5 parts stearic acid; 1 part octadecyl ester of β-(3,5-tert-butyl-4-hydroxyphenyl)propionate antioxidant; 1 part bis-(3-triethoxysilanepropyl)tetrasulfide coupling agent; 3 parts di-2-octyl phthalate crosslinking agent.

[0055] The raw materials, excluding the crosslinking agent, were mixed in an internal mixer according to the above-mentioned weight proportions, with an outlet temperature of 130℃. The mixed rubber sheet was then passed through a two-roll mill three times, with the crosslinking agent added. After this process, the roller gap was adjusted to approximately 2.5mm, and the sheet was extruded. It was then vulcanized for 5 minutes on a flat vulcanizing machine at 165℃. The physical property test results of the vulcanized sheet are shown in Table 4, the dynamic mechanical test diagram is shown in Table 3, the analysis results are shown in Table 5, and the light transmittance and haze test results are shown in Table 6.

[0056] Comparative Example 4

[0057] Using the same processing formula and process, the styrene-butadiene polymer was the sample in Comparative Example 2.

[0058] Comparative Example 5

[0059] Using the same processing formula and process, the styrene-butadiene polymer was the sample in Comparative Example 3.

[0060] Table 4. Results of physical property tests

[0061]

[0062] The physical properties of the vulcanized sheets show that the wear resistance deteriorates as the random distribution of styrene decreases. The vulcanized sheets of the styrene-butadiene polymer compound synthesized using this invention exhibit the best physical properties and wear resistance.

[0063] Table 5. Results of Dynamic Mechanical Performance Tests

[0064] name Tg / ℃ tanδ(tg) tanδ(0℃) tanδ(60℃) Example 3 -32.87 0.1835 0.1060 0.1063 Comparative Example 4 -32.91 0.2368 0.1187 0.1303 Comparative Example 5 -32.04 0.2468 0.1347 0.1358

[0065] The results of dynamic mechanical property tests show that the styrene-butadiene polymer vulcanized sheets synthesized using this invention generate the least heat in application and have the best compatibility with other rubbers and fillers.

[0066] Table 6. Results of transmittance and haze tests

[0067] Light transmittance / % Haze / % Example 3 87.3 18.69 Comparative Example 4 78.8 17.14 Comparative Example 5 76.6 17.93

[0068] The results of light transmittance and haze tests show that the styrene-butadiene polymer vulcanized sheet synthesized using this invention has the best light transmittance, reaching over 85%.

Claims

1. A diblock styrene-butadiene copolymer, characterized in that: The diblock styrene-butadiene copolymer is composed of styrene homopolymer blocks and styrene-butadiene random copolymer blocks; The benzene ring hydrogen ratio of the diblock styrene-butadiene copolymer is 3.0~6.0; In the butadiene unit of the diblock styrene-butadiene copolymer, the proportion of poly(1,2) structural units is 26% to 40%. The mass ratio of styrene to butadiene blocks in the diblock styrene-butadiene copolymer is 40:60 to 50:

50. The styrene unit mass percentage content in the random copolymer blocks of the diblock styrene-butadiene copolymer is 30-40%; The benzene ring hydrogen ratio is expressed as the ratio of the peak areas at δ=7.09 and δ=6.56 in the 1H NMR spectrum; the molecular weight of the diblock styrene-butadiene copolymer is 5.0 × 10⁻⁶. 4 ~2.0×10 5 .

2. The method for preparing a diblock styrene-butadiene copolymer according to claim 1, characterized in that: In anionic polymerization systems, styrene and butadiene mixed monomers are first added for random copolymerization, followed by the addition of styrene monomers for homopolymerization. After homopolymerization is completed, the polymerization is terminated to obtain the final product.

3. The method for preparing a diblock styrene-butadiene copolymer according to claim 2, characterized in that: The anionic polymerization system comprises a nonpolar hydrocarbon solvent, a polar structure modifier, and an initiator.

4. The method for preparing a diblock styrene-butadiene copolymer according to claim 3, characterized in that: The initiator is n-butyllithium, and the amount added is 0.02wt% to 0.1wt% of the total mass of the anionic polymerization system.

5. The method for preparing a diblock styrene-butadiene copolymer according to claim 3, characterized in that: The polar structure modifier includes one or more of tetrahydrofuran, diethyl ether, ethyl methyl ether, anisole, diphenyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofurfuryl ethyl ether, bistetrahydrofurfuryl propane, triethylamine, hexamethylphosphonotriamine, and tetramethylethylenediamine.

6. The method for preparing a diblock styrene-butadiene copolymer according to claim 5, characterized in that: The polar structure modifier is composed of at least one of tetrahydrofurfuryl ethyl ether or bistetrahydrofurfuryl propane and tetrahydrofuran in a mass ratio of 1:10 to 1:

5.

7. The method for preparing a diblock styrene-butadiene copolymer according to claim 3, characterized in that: The nonpolar hydrocarbon solvents include one or more of pentane, hexane, octane, heptane, and cyclohexane.

8. A method for preparing a diblock styrene-butadiene copolymer according to claim 3 or 7, characterized in that: The nonpolar hydrocarbon solvent is cyclohexane.

9. The method for preparing a diblock styrene-butadiene copolymer according to claim 2, characterized in that: The styrene and butadiene mixed monomers are fed slowly and at a constant rate, with the feeding time controlled within the range of 30 to 90 minutes.

10. The method for preparing a diblock styrene-butadiene copolymer according to claim 2, characterized in that: The random copolymerization temperature is 70~80℃; The homopolymerization temperature is 60~70℃.

11. The application of the diblock styrene-butadiene copolymer according to claim 1, characterized in that: It is used in the preparation of highly transparent vulcanized shoe soles.

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