Epoxy-functionalized polysulfide modified silica white / rubber composite material and preparation method thereof

Abstract

The application discloses an epoxy functionalized polysulfur modified white carbon black / rubber composite material and a preparation method thereof, wherein the preparation method comprises the following steps: heating sulfur to 130-185 DEG C to melt the sulfur, adding an olefin monomer without heteroatoms, and stirring to react; adjusting the temperature of the reaction system to 110-135 DEG C, adding an olefin monomer containing an epoxy group, and stirring to react, so as to prepare an epoxy functionalized polysulfur; mixing raw rubber, white carbon black and the epoxy functionalized polysulfur in a mixing mill, adding a vulcanization package through an open mill at room temperature, and finally hot-pressing vulcanization to obtain vulcanized rubber. The vulcanized rubber prepared by the method has the advantages of significantly improving white carbon black dispersion and enhancing interface interaction, obtaining higher mechanical properties than traditional white carbon black / rubber composite materials modified by a sulfur-containing silane coupling agent, lower rolling resistance and more excellent wet skid resistance, and the like; the epoxy functionalized polysulfur is easy to synthesize, and no VOC is released in the modification process.

Description

Technical Field

[0001] This invention relates to the field of rubber materials, specifically to an epoxy-functionalized polysulfide-modified silica / rubber composite material and its preparation method. Background Technology

[0002] Silica is a major filler in rubber products, significantly improving the mechanical strength and tear resistance of rubber materials. In particular, adding silica to tire tread compounds enhances wet skid resistance and reduces rolling resistance, making it an essential filler for green tire tread compounds. However, silica contains a large number of silanol groups on its surface, resulting in poor compatibility with non-polar rubbers. Therefore, silica / rubber composites must be modified to improve their compatibility with the rubber matrix, thereby achieving ideal composite properties. In rubber science and engineering, sulfur-containing silane coupling agents are commonly used to modify silica / rubber composites. The alkoxysilane groups in the sulfur-containing silane coupling agent react with the silanol groups on the silica surface, while the sulfur-containing portion (thiol groups or polysulfide bonds) in the molecule participates in the rubber vulcanization reaction, thus improving the interfacial interaction between silica and rubber and enhancing the dispersion of silica in the rubber matrix.

[0003] However, sulfur-containing silane coupling agents are generally obtained by reacting sodium polysulfide with chloropropylsilane in an organic solvent, which is a complex preparation process. Moreover, traditional sulfur-containing silane coupling agents are generally small molecules with low reactivity with silica. During the modification process, VOCs are released due to the reaction of alkoxysilane groups with silica. Summary of the Invention

[0004] Based on this, the present invention provides an epoxy-functionalized polysulfide modified silica / rubber composite material and its preparation method, in order to solve the technical problems in the rubber industry, which require the addition of a large amount of sulfur-containing silane coupling agent to modify silica / rubber composite materials, and the preparation process of sulfur-containing silane coupling agent is complicated, requires the use of organic solvents, and the sulfur-containing silane coupling agent is a small molecule with low modification efficiency, as well as the VOC emission in the modification process.

[0005] The principle of this application is as follows: Sulfur is copolymerized with olefin monomers that do not contain heteroatoms (meaning they do not contain atoms other than carbon and hydrogen), and then olefin monomers containing epoxy groups are added for further copolymerization to prepare polysulfides containing epoxy groups in the chain. The epoxy groups in the epoxy-functionalized polysulfide can react with the silanol groups on the surface of silica, and the sulfur chain can participate in the rubber vulcanization reaction, thereby improving the dispersion and interfacial interaction of silica. Moreover, there are no VOC emissions during the modification process. The epoxy groups in the epoxy-functionalized polysulfide have multiple reaction sites in the molecular chain, resulting in high modification efficiency. According to actual needs, the structure and properties of the epoxy-functionalized polysulfide can be easily controlled by changing the type and content of sulfur, heteroatom-free olefin monomers, epoxy-group-containing olefin monomers, and reaction conditions, thereby controlling the structure and properties of the composite material. Furthermore, the epoxy-functionalized polysulfide is prepared by bulk copolymerization, making the raw materials readily available and the synthesis process simple.

[0006] To achieve the above objectives, the present invention provides a method for preparing epoxy-functionalized polysulfide-modified silica / rubber composite material, comprising the following steps:

[0007] S1. Preparation of epoxy functionalized polysulfide

[0008] Sulfur is heated to temperature T1 to melt it, and olefin monomers without heteroatoms are added. The reaction is stirred for 3 to 12 hours. The temperature of the reaction system is then adjusted to T2, and olefin monomers containing epoxy groups are added. The reaction is stirred for 6 to 24 hours. The reactants are dissolved in an organic solvent, and unreacted sulfur is removed by filtration. The solvent in the upper layer of the solution is evaporated to obtain epoxy functional polysulfide. The organic solvent is one of tetrahydrofuran, chloroform, and toluene.

[0009] Among them: the boiling point of the olefin monomer without heteroatoms is greater than the reaction temperature T1, and the boiling point of the olefin monomer without heteroatoms is greater than the reaction temperature T2. T1 is 130~185℃, and T2 is 110~135℃.

[0010] S2. Preparation of epoxy functionalized polysulfide modified silica / rubber composite materials

[0011] Raw rubber, silica, and epoxy functional polysulfide are mixed in an internal mixer, with the mass ratio of raw rubber to silica being 100:20-100, and the mass of epoxy functional polysulfide being 5%-25% of silica. The mixing time is 3-15 minutes, and the temperature is 110-160℃. Then, a vulcanizing bag is added via a two-roll mill at room temperature, and finally, hot-press vulcanization is performed to obtain an epoxy functionalized polysulfide-modified silica / rubber composite material. The vulcanizing bag refers to a mixture of commonly used sulfur, vulcanization activators, and accelerators. The raw rubber is at least one of natural rubber and styrene-butadiene rubber.

[0012] As a further preferred embodiment of the present invention, the olefin monomer without heteroatoms is one or more of styrene, α-methylstyrene, divinylbenzene, diisopropenylbenzene, squalene, myrcene, limonene, and dicyclopentadiene.

[0013] As a further preferred technical solution of the present invention, the olefin monomer containing the epoxy group is one or more of vinyl glycidyl ether, allyl glycidyl ether, glycidyl methacrylate, glycidyl acrylate, 4-hydroxybutyl acrylate glycidyl ether, 1,2-epoxy-4-vinylcyclohexane, and 4-vinylbenzyl glycidyl ether.

[0014] As a further preferred technical solution of the present invention, in step S1, the sulfur content is 20-80 wt%, the content of olefin monomers without heteroatoms is 5-50 wt%, and the content of olefin monomers containing epoxy groups is 15-75 wt%.

[0015] According to another aspect of the present invention, the present invention also provides an epoxy-functionalized polysulfide-modified silica / rubber composite material.

[0016] The epoxy-functionalized polysulfide-modified silica / rubber composite material and its preparation method of the present invention, by adopting the above technical solution, can achieve the following beneficial effects:

[0017] 1) The preparation method of the present invention uses bulk copolymerization to obtain epoxy functionalized polysulfide. Its synthesis process is simple, requires no solvent, and has high atom utilization, which solves the technical problems of complex synthesis process and need to use organic solvents in traditional sulfur-containing silane coupling agent synthesis.

[0018] 2) The preparation method of the present invention uses bulk copolymerization to obtain epoxy-functionalized polysulfide macromolecules, which is beneficial for polysulfide molecular chains to coat the surface of silica. At the same time, the polysulfide molecular chains have multiple epoxy groups and multiple reaction sites, which increases the probability of reaction with silica. Therefore, the epoxy-functionalized polysulfide modification efficiency is high, and there is no VOC release during the modification process.

[0019] 3) The vulcanized rubber prepared by the method of the present invention significantly improves the dispersion of silica and enhances the interfacial effect, resulting in higher mechanical properties, lower rolling resistance and better wet skid resistance than silica / rubber composites modified by traditional sulfur-containing silane coupling agents. Attached Figure Description

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0021] Figure 1 This is a schematic diagram of the synthesis circuit and structure of epoxy functionalized polysulfide.

[0022] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0023] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0024] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this invention pertains. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0025] I. Preparation of epoxy functionalized polysulfides A1, A2, A3, A4, A5, A6, A7, A8, A9, and A10

[0026] 80 g of sulfur was heated to 185 °C to melt it, 5 g of divinylbenzene was added, and the mixture was stirred for 3 hours. The temperature of the reaction system was then adjusted to 120 °C, 15 g of 4-hydroxybutyl acrylate glycidyl ether was added, and the mixture was stirred for 18 hours. The reactants were dissolved in tetrahydrofuran, filtered, and the solvent was evaporated to obtain epoxy functional polysulfide A1.

[0027] 60 g of sulfur was heated to 140 °C to melt it, 15 g of myrcene was added, and the mixture was stirred for 8 hours. The temperature of the reaction system was then adjusted to 120 °C, 25 g of 4-vinylbenzyl glycidyl ether was added, and the mixture was stirred for 12 hours. The reactants were dissolved in toluene, filtered, and the solvent was evaporated to obtain epoxy functional polysulfide A2.

[0028] 40 g of sulfur was heated to 160 °C to melt it, and 20 g of dicyclopentadiene was added. The mixture was stirred and reacted for 4 hours. The temperature of the reaction system was then adjusted to 120 °C, and 40 g of vinyl glycidyl ether was added. The mixture was stirred and reacted for 16 hours. The reactants were dissolved in tetrahydrofuran, filtered, and the solvent was evaporated to obtain epoxy functional polysulfide A3.

[0029] 40 g of sulfur was heated to 130 °C to melt it, 30 g of styrene was added, and the mixture was stirred for 12 hours. The temperature of the reaction system was then adjusted to 110 °C, 30 g of glycidyl acrylate was added, and the mixture was stirred for 24 hours. The reactants were dissolved in tetrahydrofuran, filtered, and the solvent was evaporated to obtain epoxy functional polysulfide A4.

[0030] 20 g of sulfur was heated to 160 °C to melt it, and 5 g of diisopropylbenzene was added. The mixture was stirred and reacted for 5 hours. The temperature of the reaction system was then adjusted to 135 °C, and 75 g of 1,2-epoxy-4-vinylcyclohexane was added. The mixture was stirred and reacted for 6 hours. The reactants were dissolved in chloroform, filtered, and the solvent was evaporated to obtain epoxy functional polysulfide A5.

[0031] 70 g of sulfur was heated to 145 °C to melt it, 5 g of styrene was added, and the mixture was stirred for 5 hours. The temperature of the reaction system was then adjusted to 130 °C, 25 g of allyl glycidyl ether was added, and the mixture was stirred for 15 hours. The reactants were dissolved in tetrahydrofuran, filtered, and the solvent was evaporated to obtain epoxy functional polysulfide A6.

[0032] 60 g of sulfur was heated to 160 °C to melt it, and 15 g of α-methylstyrene was added. The mixture was stirred and reacted for 8 hours. The temperature of the reaction system was then adjusted to 120 °C, and 25 g of glycidyl methacrylate was added. The mixture was stirred and reacted for 12 hours. The reactants were dissolved in toluene, filtered, and the solvent was evaporated to obtain epoxy functional polysulfide A7.

[0033] 40 g of sulfur was heated to 150 °C to melt it, 20 g of limonene was added, and the mixture was stirred for 4 hours. The temperature of the reaction system was then adjusted to 110 °C, 40 g of glycidyl acrylate was added, and the mixture was stirred for 16 hours. The reactants were dissolved in tetrahydrofuran, filtered, and the solvent was evaporated to obtain epoxy functional polysulfide A8.

[0034] 50 g of sulfur was heated to 160 °C to melt it, and 30 g of diisopropylbenzene was added. The mixture was stirred and reacted for 12 hours. The temperature of the reaction system was then adjusted to 115 °C, and 30 g of 4-vinylbenzyl glycidyl ether was added. The mixture was stirred and reacted for 18 hours. The reactants were dissolved in tetrahydrofuran, filtered, and the solvent was evaporated to obtain epoxy functional polysulfide A9.

[0035] 40 g of sulfur was heated to 140 °C to melt it, and 30 g of squalene was added. The mixture was stirred and reacted for 12 hours. The temperature of the reaction system was then adjusted to 125 °C, and 20 g of 4-hydroxybutyl acrylate glycidyl ether was added. The mixture was stirred and reacted for 18 hours. The reactants were dissolved in tetrahydrofuran, filtered, and the solvent was evaporated to obtain epoxy functional polysulfide A10.

[0036] To investigate the effect of temperature on the preparation process of epoxy functionalized polysulfide, the following comparative experiments were conducted:

[0037] Comparison Test 1

[0038] Using the same preparation method and process parameters as epoxy functional polysulfide A3, except that the reaction system temperature was adjusted to 100℃ before adding vinyl glycidyl ether and stirring the reaction, the final product was characterized by NMR and it was found that vinyl glycidyl ether did not participate in the reaction, and epoxy functional polysulfide was not obtained.

[0039] Comparison Test 2

[0040] Using the same preparation method and process parameters as epoxy functional polysulfide A3, except that the reaction system temperature was adjusted to 145℃ before adding vinyl glycidyl ether for stirring, the final product was characterized by NMR spectroscopy. It was found that the epoxy groups underwent self-polymerization and reacted with the thiol groups generated by heterolytic cleavage of polysulfide bonds, resulting in the gelation of the product and the disappearance of the epoxy groups.

[0041] Furthermore, when the temperature parameters in the above method for preparing epoxy functional polysulfide A1-10 were changed, specifically by changing the stirring reaction temperature of the olefin monomer containing epoxy groups to 110–135°C, and then testing was conducted, it was found that epoxy functional polysulfide could not be obtained.

[0042] The olefin monomers used in the preparation of epoxy functional polysulfide according to this invention fall into two main categories: one category consists of olefin monomers without heteroatoms, including, but not limited to, one or more of styrene, α-methylstyrene, divinylbenzene, diisopropenylbenzene, squalene, myrcene, limonene, and dicyclopentadiene; the other category consists of olefin monomers containing epoxy groups, including, but not limited to, one or more of vinyl glycidyl ether, allyl glycidyl ether, glycidyl methacrylate, glycidyl acrylate, 4-hydroxybutyl acrylate glycidyl ether, 1,2-epoxy-4-vinylcyclohexane, and 4-vinylbenzyl glycidyl ether. Further research has found that, according to the preparation method of epoxy functional polysulfide of this invention, by arbitrarily combining the above-mentioned different heteroatom-free olefin monomers and different epoxy group-containing olefin monomers, epoxy functional polysulfide with high modification efficiency can be prepared (the synthesis process is described in [reference]). Figure 1 Furthermore, by incorporating it into the rubber systems of raw rubber and silica, epoxy-functionalized polysulfide-modified silica / rubber composites can be prepared.

[0043] II. Preparation of epoxy functionalized polysulfide modified silica / rubber composites

[0044] Based on the epoxy functional polysulfide (also known as sulfur-containing silane copolymer) A1, A2, A3, A4, and A5 prepared above, samples of vulcanized rubber were further prepared, as well as comparative samples based on traditional sulfur-containing silane copolymers, as detailed below:

[0045] According to the formulation and process conditions of samples 1-7 in Table 1, raw rubber, silica, and epoxy functional polysulfide (A1, A2, A3, A4, A5) were added to an internal mixer in sequence to obtain a compound. Then, the compound was mixed in a two-roll mill at room temperature and added to a vulcanizing bag. Finally, hot pressing was performed to obtain vulcanized rubber.

[0046] According to the formulation and process conditions of Comparative Sample 1, Comparative Sample 2 and Comparative Sample 3 in Table 1, raw rubber, silica, and bis-[3-(triethoxysilyl)propyl]-tetrasulfide (TESPT) were added to an internal mixer in sequence to obtain a compound. Then, the compound was mixed in a two-roll mill at room temperature and added to a vulcanizing bag. Finally, hot pressing was performed to obtain vulcanized rubber.

[0047] The vulcanizing package can be a commonly used vulcanization system. When the raw rubber is styrene-butadiene rubber (SBR), the vulcanizing package used is: 5 grams of zinc oxide, 1 gram of stearic acid, 1.6 grams of accelerator CZ, 2 grams of accelerator D, and 1.5 grams of sulfur. When the raw rubber is natural rubber, the vulcanizing package used is: 5 grams of zinc oxide, 2 grams of stearic acid, 1.2 grams of accelerator CZ, 1.5 grams of accelerator D, and 2 grams of sulfur. The hot-press vulcanization temperature for SBR is 150℃, and for natural rubber it is 143℃.

[0048] Table 1. Formulation Table

[0049]

[0050] In Table 2, the tensile strength, elongation at break, and stress at 300% constant elongation of the samples were determined according to ISO 37-2005, with a test temperature of room temperature and a tensile rate of 500 mm / min; the tear strength was determined according to GB / T 529-2008; the fatigue heat generation was determined according to ISO 4666-3:2016; and the rolling resistance (tanδ value at 60℃ under 7% strain and 10Hz frequency) and wet slip resistance (tanδ value at 0℃ under 0.5% strain and 10Hz frequency) were measured using DMA.

[0051] Table 2. Mechanical and dynamic properties of the samples

[0052]

[0053] Analysis of Table 2 shows that the silica / rubber composite material (vulcanized rubber) prepared by the method of this invention exhibits increased 300% tensile stress and tensile strength, significantly decreased rolling resistance (tanδ value at 60℃ under 7% strain and 10Hz frequency), improved wet skid resistance (tanδ value at 0℃ under 0.5% strain and 10Hz frequency), and a significant decrease in fatigue temperature rise. Furthermore, comparison of samples 1, 2, and 3 shows that by changing the type and content of comonomers, the structure and properties of epoxy functional polysulfide can be adjusted, thereby producing different effects on the composite material. Comparison of samples 4 and 5 shows that with increasing epoxy functional polysulfide content, the composite material's tensile stress and tensile strength increase, rolling resistance decreases, wet skid resistance improves, and fatigue temperature rise significantly decreases. Comparison of samples 6 and 7 shows that with increasing mixing temperature and time, the degree of interfacial reaction increases, the composite material's tensile stress and tensile strength increase, rolling resistance decreases, wet skid resistance improves, and fatigue temperature rise significantly decreases.

[0054] The epoxy-functionalized polysulfide-modified silica-rubber composite material prepared by this invention significantly improves silica dispersion and interfacial reinforcement, resulting in higher mechanical properties, lower rolling resistance, and superior wet skid resistance compared to traditional silica-rubber composite materials modified with sulfur-containing silane coupling agents. Furthermore, the epoxy-functionalized polysulfide is synthesized via bulk copolymerization, utilizing readily available raw materials, employing a simple synthesis process, and exhibiting no VOC emissions during the modification process.

[0055] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and various changes or modifications can be made to these embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is defined only by the appended claims.

Claims

1. A method for preparing an epoxy-functionalized polysulfide-modified silica / rubber composite material, characterized in that, Includes the following steps: S1. Sulfur is heated to temperature T1 to melt it, and olefin monomers without heteroatoms are added and the reaction is stirred. Then, the temperature of the reaction system is adjusted to T2, and olefin monomers containing epoxy groups are added and the reaction is stirred to prepare epoxy functionalized polysulfide, wherein: T1 is 130-185°C. o C, The boiling point of the olefin monomer without heteroatoms is higher than the reaction temperature T1, and T2 is 110~135℃. o C, The boiling point of olefin monomers without heteroatoms is greater than the reaction temperature T2; S2. Raw rubber, silica, and epoxy functional polysulfide are mixed in an internal mixer, wherein the mass ratio of raw rubber to silica is 100:20-100, and the mass of epoxy functional polysulfide is 5%-25% of silica; then, a vulcanizing bag is added to the mixture through an open mill at room temperature, and finally, hot-press vulcanization is performed to obtain epoxy functional polysulfide modified silica / rubber composite material. The olefin monomer that does not contain heteroatoms is one or more of styrene, α-methylstyrene, divinylbenzene, diisopropenylbenzene, squalene, myrcene, limonene, and dicyclopentadiene; The olefin monomer containing the epoxy group is one or more of vinyl glycidyl ether, allyl glycidyl ether, glycidyl methacrylate, glycidyl acrylate, 4-hydroxybutyl acrylate glycidyl ether, 1,2-epoxy-4-vinylcyclohexane, and 4-vinylbenzyl glycidyl ether. In step S1, the sulfur content is 20-80 wt%, the content of olefin monomers without heteroatoms is 5-50 wt%, and the content of olefin monomers containing epoxy groups is 15-75 wt%.

2. The preparation method of the epoxy functionalized polysulfide modified silica / rubber composite material according to claim 1, characterized in that, In step S1: the olefin monomer without heteroatoms is added and the reaction is stirred at temperature T1 for a time t1 of 3 to 12 hours; the olefin monomer containing epoxy groups is added and the reaction is stirred at temperature T2 for a time t2 of 6 to 24 hours.

3. The preparation method of the epoxy functionalized polysulfide modified silica / rubber composite material according to claim 1, characterized in that, Step S1 also includes the following steps: The reactants, which contain olefin monomers and are stirred, are dissolved in an organic solvent. Unreacted sulfur is removed by filtration, and the solvent in the upper layer of the solution is evaporated to obtain epoxy functional polysulfide.

4. The preparation method of the epoxy functionalized polysulfide modified silica / rubber composite material according to claim 1, characterized in that, The raw rubber is at least one of natural rubber and styrene-butadiene rubber.

5. The method for preparing the epoxy functionalized polysulfide modified silica / rubber composite material according to any one of claims 1 to 4, characterized in that, In step S2, the mixing time is 3 to 15 minutes and the temperature is 110 to 160°C.

6. An epoxy-functionalized polysulfide-modified silica / rubber composite material, characterized in that, Prepared by the method according to any one of claims 1-5.

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