Preparation method of ESBR / SiO2-coated ESSBR composite material

Abstract

The invention discloses a preparation method of an ESBR / SiO2-coated ESSBR composite material, and belongs to the technical field of rubber composite material production, and the preparation method comprises the following steps: S1, preparing white carbon black nanoparticles; s2, preparing a dopamine solution; s3, additionally preparing white carbon black (SiO2-PDA) modified by dopamine; s4, preparing a SiO2 coated ESSBR (Ethylene Styrene Butadiene Rubber) organic hybrid filler; s5, flocculating a mixture of emulsion polymerized styrene-butadiene rubber and the SiO2 (at) ESSBR organic hybrid filler to obtain a rubber master batch; s6, adding the rubber master batch, zinc oxide, stearic acid and an antioxidant 4020 into the internal mixer, mixing for 6 minutes, discharging rubber, cooling to room temperature, mixing on an open mill, adding sulfur and an accelerant CZ, batching out, and cooling for later use; s7, vulcanizing the rubber compound in a press vulcanizer, and fully cooling at room temperature after vulcanization to obtain the ESBR / SiO2-coated ESSBR composite material, the technical problems of low grafting rate of white carbon black, poor dispersibility of silicon dioxide and poor compatibility of silicon dioxide and a rubber matrix are solved, and the ESBR / SiO2-coated ESSBR composite material is widely applied to production of rubber composite materials.

Description

Technical Field

[0001] This invention belongs to the field of rubber composite material production technology, and particularly relates to a method for preparing ESBR / SiO2@ESSBR composite material. Background Technology

[0002] In recent years, with the rapid development of the green tire industry, the demand for high-performance rubber composite materials has become increasingly urgent. To meet the requirements of green tires, tread materials are required to have low rolling resistance, high wear resistance, and high wet skid resistance, which places higher demands on tread compounds. Emulsion styrene-butadiene rubber (ESBR), as an important type of styrene-butadiene rubber, has advantages over solution-polymerized styrene-butadiene rubber, such as low cost, good processability, flexural resistance, and environmental friendliness, and occupies an important position in tire manufacturing. Silica, as a major reinforcing filler in green tires, is used in tire treads to improve wet skid resistance, reduce rolling resistance, and save energy and protect the environment. However, silica has a large number of silanol groups on its surface, resulting in high surface polarity. These polar hydroxyl groups have strong adsorption effects and easily form hydrogen bonds with their own hydroxyl groups, making dispersion difficult. At the same time, the inorganic hydrophilic properties of silica make it poorly compatible with non-polar rubber matrices, seriously restricting the overall performance of composite materials and becoming a key bottleneck for the technological upgrading of green tires.

[0003] To address this issue, surface modification of silica is the primary method to improve its compatibility and dispersibility with rubber matrices. Surface grafting modification, which involves covalently grafting polymers onto the surface of silica, is widely used due to its high stability and strong functional designability. Epoxidized solution-polymerized styrene-butadiene rubber (ESSBR) is a bifunctional chemical containing epoxy groups and carbon-carbon double bonds. Currently, only ESSBR grafting of silica has been explored; however, ESSBR has significant steric hindrance, resulting in low grafting rates that fail to meet the performance requirements of the desired composite material.

[0004] Therefore, in the field of rubber composite material production technology, there is still a need for research and improvement on the preparation method of ESBR / SiO2@ESSBR composite material. This is a research hotspot and focus in the current field of rubber composite material production technology, and it is also the starting point for the completion of this invention. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to provide a method for preparing ESBR / SiO2@ESSBR composite material to solve the technical problems of low grafting rate of silica, poor dispersion of silica and poor compatibility with rubber matrix.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is: a method for preparing ESBR / SiO2@ESSBR composite material, comprising the following steps: S1. Adding ethyl silicate and ammonia to a mixture of ethanol and deionized water, stirring thoroughly at 40℃-60℃ for 6-8 hours, and repeatedly washing with water by centrifugation to obtain silica nanoparticles; S2. Dissolving dopamine in tris(hydroxymethyl)aminomethane hydrochloride buffer solution to obtain a dopamine solution; S3. Adding silica nanoparticles to tris(hydroxymethyl)aminomethane hydrochloride buffer solution, sonicating, mixing with the dopamine solution, sonicating the mixture, stirring thoroughly at 25℃ for (10±3) hours, dopamine self-polymerizing on the silica surface to form a polydopamine layer, centrifuging and drying, and then grinding to obtain dopamine-modified silica (SiO2-PDA); S4. Dissolving ESSBR in cyclohexane, adding dopamine-modified silica (SiO2-PDA), and stirring thoroughly at 45℃ for 5-8 hours, ESSBR molecules... The epoxy groups on the chain undergo a ring-opening reaction with the amino and catechol groups on the polydopamine layer. ESSBR is covalently grafted onto the surface of silica. After repeated centrifugation and washing with toluene to remove unreacted ESSBR, the material is dried to obtain SiO2@ESSBR organic hybrid filler. S5. The SiO2@ESSBR organic hybrid filler is added to deionized water and ultrasonically dispersed for 1 hour. The dispersion is added to emulsion styrene-butadiene rubber and stirred thoroughly to ensure uniform mixing. The mixture of emulsion styrene-butadiene rubber and SiO2@ESSBR organic hybrid filler is flocculated to obtain a masterbatch, which is then dried for later use. S6. The masterbatch, zinc oxide, stearic acid, and antioxidant 4020 are added to a mixer and mixed for 6 minutes. After the mixture is discharged and cooled to room temperature, it is mixed on a two-roll mill with sulfur and accelerator CZ added. When the system is uniformly mixed, it is sheeted and cooled for later use. S7. The mixed material is placed in a flat vulcanizing machine for vulcanization. After vulcanization, it is cooled thoroughly to room temperature to obtain the ESBR / SiO2@ESSBR composite material.

[0007] As an improvement, in step S2, the pH of the tris(hydroxymethyl)aminomethane hydrochloride buffer is 8.5.

[0008] As a further improvement, in step S4, the weight ratio of ESSBR to dopamine-modified silica (SiO2-PDA) is 2.5% to 10%.

[0009] As a further improvement, in step S5, 30 parts by weight of SiO2@ESSBR organic hybrid filler are added to deionized water and ultrasonically dispersed for 1 hour. The dispersion is then added to 100 parts by weight of emulsion styrene-butadiene rubber and stirred thoroughly to make it uniform. The mixture of emulsion styrene-butadiene rubber and SiO2@ESSBR organic hybrid filler is flocculated to obtain masterbatch.

[0010] As a further improvement, in step S5, a 2wt% CaCl2 aqueous solution is used as a flocculant to flocculate the mixture of emulsion styrene-butadiene rubber and the SiO2@ESSBR organic hybrid filler to obtain a masterbatch, which is then dried at 50°C for later use.

[0011] As a further improvement, in step S6, 130 parts by weight of masterbatch, 3 parts by weight of zinc oxide, 2 parts by weight of stearic acid and 2.5 parts by weight of antioxidant 4020 are added to the internal mixer and mixed for 6 minutes. After the glue is discharged and cooled to room temperature, 2.5 parts by weight of sulfur and 2 parts by weight of accelerator CZ (N-cyclohexyl-2-benzothiazole sulfenamide) are added to the open mill. When the system is mixed evenly, it is sheeted and cooled for later use.

[0012] As a further improvement, in step S7, the flat vulcanizing machine is set to a temperature of 150°C, a pressure of 10MPa, and a time of 1.3×Tc90, and then cooled to room temperature for 8-10 hours after vulcanization.

[0013] After adopting the above technical solution, the beneficial effects of the present invention are:

[0014] (1) The coating modification of ESSBR in this invention, combined with the surface modification of silica by dopamine, facilitates the reaction between the amino and phenolic hydroxyl groups of dopamine on the silica surface and the epoxy groups of ESSBR, promoting the mutual bonding of the two. After modification, ESSBR molecular chains are grafted onto the silica surface, which can effectively improve the dispersibility of silica. According to the principle of like dissolves like, the interfacial interaction between silica and rubber matrix is ​​significantly improved. Because the interfacial compatibility between the filler and rubber matrix is ​​good and the dispersibility of silica is improved, the composite material has better dynamic mechanical properties.

[0015] (2) The modified silica process used in this invention provides a large number of active reaction sites in the polydopamine layer, which improves the grafting rate of the polymer.

[0016] (3) The improved dispersibility of the filler and its compatibility with the rubber matrix of the present invention are beneficial to the mechanical properties of rubber composite materials, improve the anti-slip performance, and reduce rolling resistance. Attached Figure Description

[0017] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0018] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0019] Figure 1 This is the strain dependence of the storage modulus (G') of different ESBR / SiO2@ESSBR-x composite materials in the embodiments of the present invention;

[0020] Figure 2 This is the strain dependence of the loss factor (Tanδ) of different ESBR / SiO2@ESSBR-x composite materials in the embodiments of the present invention;

[0021] Figure 3 This describes the variation of the loss factor (Tanδ) with temperature for different ESBR / SiO2@ESSBR composite materials in the embodiments of the present invention.

[0022] Figure 4 These are SEM images of the fracture surfaces of different ESBR / SiO2@ESSBR composite materials in embodiments of the present invention. Detailed Implementation

[0023] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] The terms used in this specification, such as "front," "back," "left," "right," "inner," "outer," and "middle," are merely for clarity of description and are not intended to limit the scope of the invention. Any changes or adjustments to their relative relationships, without substantially altering the technical content, shall also be considered within the scope of the invention.

[0025] In the following embodiments:

[0026] Emulsion-polymerized styrene-butadiene rubber (SBR) is a copolymer of butadiene and styrene synthesized through emulsion polymerization. Silica (fumed silica) is a white, non-toxic powder rich in silanol groups (Si-OH) on its surface, with the chemical formula SiO2·nH2O. Dopamine-modified silica (SiO2-PDA) has a silica microsphere structure; therefore, SiO2 can be used to simplify the structure of dopamine-modified silica with silica as the main component. Furthermore, SiO2@ESSBR can represent the structure of ESSBR grafted onto the surface of silica; and ESBR / SiO2@ESSBR can represent ESSBR grafted onto silica / rubber composites.

[0027] This invention provides a method for preparing ESBR / SiO2@ESSBR composite material, comprising the following steps:

[0028] S1. Add ethyl silicate and ammonia to a mixture of ethanol and deionized water, stir thoroughly at 40℃-60℃ for 6-8 hours, and wash repeatedly with water by centrifugation to obtain silica nanoparticles.

[0029] S2. Dissolve dopamine in a tris(hydroxymethyl)aminomethane hydrochloride buffer solution at pH 8.5 to obtain a dopamine solution;

[0030] S3. Add silica nanoparticles to tris(hydroxymethyl)aminomethane hydrochloride buffer, sonicate, mix with dopamine solution, sonicate the mixture, stir thoroughly at 25°C for (10±3) h, dopamine self-polymerizes on the silica surface to form a polydopamine layer, centrifuge, dry and grind to obtain dopamine-modified silica (SiO2-PDA).

[0031] S4. Dissolve ESSBR in cyclohexane, add dopamine-modified silica (SiO2-PDA), and stir thoroughly at 45℃ for 5-8 hours. The epoxy groups on the ESSBR molecular chain undergo a ring-opening reaction with the amino and catechol groups on the polydopamine layer. ESSBR is covalently grafted onto the surface of silica. After repeated centrifugation and washing with toluene to remove unreacted ESSBR, the product is dried to obtain SiO2@ESSBR organic hybrid filler. The weight ratio of ESSBR to dopamine-modified silica (SiO2-PDA) is 2.5% to 10%.

[0032] S5. Add 30 parts by weight of SiO2@ESSBR organic hybrid filler to deionized water and ultrasonically disperse for 1 hour. Add the dispersion to 100 parts by weight of emulsion styrene-butadiene rubber and stir thoroughly to make it evenly mixed. Use 2 wt% CaCl2 aqueous solution as flocculant to flocculate the mixture of emulsion styrene-butadiene rubber and the SiO2@ESSBR organic hybrid filler to obtain masterbatch. Dry the masterbatch at 50°C for later use.

[0033] S6. Add 130 parts by weight of masterbatch, 3 parts by weight of zinc oxide, 2 parts by weight of stearic acid and 2.5 parts by weight of antioxidant 4020 to the internal mixer and mix for 6 minutes. After discharging and cooling to room temperature, mix on the open mill with 2.5 parts by weight of sulfur and 2 parts by weight of accelerator CZ (N-cyclohexyl-2-benzothiazole sulfenamide). When the system is mixed evenly, sheet it and cool it for later use.

[0034] S7. The compound rubber is placed in a flat vulcanizing machine for vulcanization. After vulcanization, it is cooled to room temperature to obtain ESBR / SiO2@ESSBR composite material. The flat vulcanizing machine is set with a temperature of 150℃, a pressure of 10MPa, and a time of 1.3×Tc90. After vulcanization, it is cooled to room temperature for 8-10 hours.

[0035] like Figure 1 and Figure 2 As shown, curves ae represent the mass percentages of ESSBR in the composite material as 0%, 2.5%, 5%, 7.5%, and 10% of the SiO2-PDA mass, respectively. With increasing ESSBR content, the initial G' value of the ESBR / SiO2@ESSBR composite material continuously decreases, and the strain dependence of Tanδ decreases. This is because with increasing ESSBR content, the dispersibility of SiO2 improves, weakening the filler-filler network.

[0036] like Figure 3 As shown, curves ae represent the mass percentages of ESSBR in the composite material as 0%, 2.5%, 5%, 7.5%, and 10% of the SiO2-PDA mass, respectively. The loss factors of different ESSBR / SiO2@ESSBR composites at 0℃ and 60℃ are shown in the table below:

[0037] Sample Tanδat 0℃ Tanδat 60℃ <![CDATA[ESBR / SiO2]]> 0.193 0.082 <![CDATA[ESBR / SiO2@ESSBR-2.5]]> 0.205 0.080 <![CDATA[ESBR / SiO2@ESSBR-5]]> 0.206 0.079 <![CDATA[ESBR / SiO2@ESSBR-7.5]]> 0.227 0.078 <![CDATA[ESBR / SiO2@ESSBR-10]]> 0.246 0.076

[0038] With increasing ESSBR content, Tanδ at 0℃ increases, improving the composite material's anti-slip properties; Tanδ gradually decreases at 60℃, thus reducing rolling resistance. ESSBR exhibits steric hindrance, which is beneficial for improving filler dispersibility. Improved filler dispersibility and enhanced interfacial compatibility can enhance dynamic mechanical properties.

[0039] like Figure 4 As shown in Figures a and e, the fracture surface SEM images are presented for composite materials with ESSBR content of 0%, 2.5%, 5%, 7.5%, and 10% of the SiO2-PDA mass, respectively. With increasing ESSBR content, the fracture surface becomes smoother, and the phase interface between ESSBR and the rubber matrix becomes blurred, with no significant phase interface separation observed. This indicates that with increasing ESSBR content, the dispersibility of SiO2 in the rubber matrix is ​​improved, and its compatibility with the rubber matrix is ​​greatly enhanced.

[0040] This invention first modifies silica with dopamine. Dopamine can self-polymerize on the silica surface to form a polydopamine layer. The amino and catechol groups on the polydopamine layer enhance surface activity, providing a reaction platform for the preparation of organic hybrid materials and increasing the grafting rate of polymer chains. The epoxy groups of ESSBR undergo ring-opening reactions with the amino and catechol groups on the polydopamine molecular chains to form covalent bonds, improving the stability of the interfacial bonding between ESSBR and silica. ESSBR has a nonpolar structure similar to ESBR. Based on the principle of similar compatibility, ESSBR and ESBR have good compatibility. Grafting ESSBR molecular chains onto the silica surface effectively improves the dispersibility of silica, significantly improving the interfacial compatibility between silica and the rubber matrix, thus resulting in composite materials with better dynamic mechanical properties. Furthermore, the ESSBR on the surface of the organic hybrid material has a steric hindrance effect, which is beneficial for improving the dispersibility of the filler. Therefore, the prepared composite material exhibits good performance.

[0041] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A preparation method of an ESBR / SiO2@ESSBR composite material, characterized in that, The method comprises the following steps: S1. Adding ethyl silicate and ammonia water into a mixture of ethanol and deionized water, and stirring sufficiently at a temperature of 40-60 DEG C for 6-8 h, and repeatedly centrifuging and washing with water to obtain white carbon black nanoparticles; S2. Dissolving dopamine in a tris-hydroxymethyl aminomethane hydrochloride buffer to obtain a dopamine solution; S3. Adding the white carbon black nanoparticles into the tris-hydroxymethyl aminomethane hydrochloride buffer, and mixing after ultrasonic treatment, and mixing with the dopamine solution, and ultrasonic treatment, and stirring sufficiently at 25 DEG C for (10±3) h, and self-polymerizing the dopamine on the surface of the white carbon black to form a polydopamine layer, and centrifuging and drying, and grinding to obtain dopamine-modified white carbon black (SiO2-PDA); S4. Dissolving ESSBR into cyclohexane, and adding the dopamine-modified white carbon black (SiO2-PDA) and stirring sufficiently at a temperature of 45 DEG C for 5-8 h, and allowing the epoxy groups on the molecular chain of the ESSBR to undergo ring-opening reaction with the amino groups and the o-diphenol groups on the polydopamine layer, and allowing the ESSBR to be grafted to the surface of the white carbon black through a covalent bond, and repeatedly centrifuging and washing with toluene, and drying after removing the unreacted ESSBR to obtain SiO2@ESSBR organic hybrid filler; S5. Adding the SiO2@ESSBR organic hybrid filler into deionized water and ultrasonic dispersing for 1 h, and adding the dispersion into emulsion styrene-butadiene rubber, and stirring sufficiently to mix uniformly, and flocculating the mixture of the emulsion styrene-butadiene rubber and the SiO2@ESSBR organic hybrid filler to obtain masterbatch, and drying the masterbatch for standby use; S6. Adding the masterbatch, zinc oxide, stearic acid and antioxidant 4020 into an internal mixer and mixing for 6 min, and discharging and cooling to room temperature, and adding sulfur and accelerator CZ on an open mill after the system is mixed uniformly, and discharging and cooling for standby use; S7. Placing the mixed rubber into a flat vulcanizer for vulcanization, and cooling sufficiently at room temperature after vulcanization is completed to obtain an ESBR / SiO2@ESSBR composite material.

2. The preparation method of the ESBR / SiO2@ESSBR composite material according to claim 1, characterized in that, In step S2, the pH of the tris-hydroxymethyl aminomethane hydrochloride buffer is 8.

5.

3. The preparation method of the ESBR / SiO2@ESSBR composite material according to claim 1, characterized in that, In step S4, the weight of the ESSBR accounts for 2.5%-10% of the weight of the dopamine-modified white carbon black (SiO2-PDA).

4. The preparation method of the ESBR / SiO2@ESSBR composite material according to claim 1, characterized in that, In step S5, 30 parts by weight of the SiO2@ESSBR organic hybrid filler is added into deionized water and ultrasonic dispersing for 1 h, and the dispersion is added into 100 parts by weight of emulsion styrene-butadiene rubber, and stirred sufficiently to mix uniformly, and the mixture of the emulsion styrene-butadiene rubber and the SiO2@ESSBR organic hybrid filler is flocculated to obtain masterbatch.

5. The preparation method of the ESBR / SiO2@ESSBR composite material according to claim 4, characterized in that, In step S5, 2wt% CaCl2 aqueous solution is used as a flocculating agent to flocculate the mixture of the emulsion styrene-butadiene rubber and the SiO2@ESSBR organic hybrid filler to obtain masterbatch, and the masterbatch is dried at a temperature of 50 DEG C for standby use.

6. The preparation method of the ESBR / SiO2@ESSBR composite material according to claim 1, characterized in that, In step S6, 130 parts by weight of the masterbatch, 3 parts by weight of zinc oxide, 2 parts by weight of stearic acid and 2.5 parts by weight of antioxidant 4020 were mixed in a Banbury mixer for 6 minutes, and after the discharge was cooled to room temperature, 2.5 parts by weight of sulfur and 2 parts by weight of accelerator CZ (N-cyclohexyl-2-benzothiazole sulfenamide) were added and mixed on an open mill. After the system was uniformly mixed, it was cooled and used.

7. The preparation method of the ESBR / SiO2@ESSBR composite material according to claim 1, characterized in that, In step S7, the flat vulcanizing machine was set to a temperature of 150°C, a pressure of 10 MPa, and a time of 1.3 x Tc90, and after vulcanization was completed, it was cooled at room temperature for 8-10 hours.

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