Copolymer microgel latex and its preparation method and application

Abstract

This invention relates to the field of emulsion polymerization, and discloses copolymer microgel latex, its preparation method, and applications. The monomers forming the copolymer microgel latex include conjugated diene monomers, monovinyl aromatic monomers, vinyl unsaturated carboxylic acid monomers, crosslinking monomers, and monomers containing epoxy functional groups; epoxy monomers are grafted onto the surface of the copolymer. Rubber compositions containing the copolymer microgel exhibit a good balance in rolling resistance, wet skid resistance, and abrasion resistance in their vulcanized rubber, making them suitable for manufacturing tire tread compounds.

Description

Technical Field

[0001] This invention relates to the field of emulsion polymerization, and more specifically, to a copolymer microgel latex, a method for preparing a copolymer microgel latex, a latex composition, a rubber composition, a vulcanizate, and the application of the vulcanizate in the manufacture of tire treads. Background Technology

[0002] Copolymer microgel latex can be directly mixed with natural latex or styrene-butadiene latex, and then co-precipitated to form masterbatch. Due to their large specific surface area, copolymer microgels have more opportunities to interact physically and chemically with the matrix rubber and reinforcing fillers. Compared with inorganic reinforcing fillers, copolymer microgels have a lower density, and their application in rubber can improve or enhance many properties, such as improving extrusion process performance (reducing exit swell and thermal sagging), significantly reducing rolling resistance of vulcanized rubber, improving wet skid resistance, and enhancing abrasion resistance. These properties are particularly important for tire production and use; therefore, the application of copolymer microgels in rubber has become a research hotspot in recent years.

[0003] There are several methods for preparing copolymer microgels. One method involves adding peroxide to the copolymer microgel latex to crosslink the rubber microparticles in the latex under certain conditions. For example, USP6127488 uses peroxide to crosslink styrene-butadiene rubber latex under certain conditions. The crosslinked styrene-butadiene rubber microparticles are then used in NR / BR blends to improve the wet skid resistance and abrasion resistance of the NR / BR blends.

[0004] Secondly, high-energy rays are used to initiate the crosslinking of rubber microparticles in latex, i.e., radiation crosslinking. For example, CN103073758A uses radiation to crosslink nitrile rubber latex, obtaining crosslinked nitrile rubber latex with a particle size of 50-200 nanometers, a gel content greater than 60%, and a homogeneous structure. The crosslinked nitrile rubber latex is mixed with uncrosslinked styrene-butadiene rubber latex, and after coagulation, a rubber composition with a crosslinked nitrile rubber particle to uncrosslinked styrene-butadiene rubber weight ratio of 1:99 to 20:80 is obtained. The rolling resistance, wet skid resistance, and wear resistance of the vulcanized rubber of this rubber composition can be improved simultaneously, and it can be used to prepare high-performance automotive tread rubber. However, the disadvantage of the above two methods is that it is difficult to control the composition, particle structure, and particle size of the gel microparticles.

[0005] The third method involves directly preparing copolymer microgel latex via emulsion polymerization. This method is characterized by two main features: first, the composition, particle structure, and particle size of the copolymer microgel can be flexibly controlled; second, by introducing functional monomers containing special functional groups to graft and modify the particle surface, the processing and application performance of different rubber compositions can be improved. For example, CN104136519A provides a polybutadiene microgel containing hydroxyl groups with a glass transition temperature of -70 to -80℃ and a gel content greater than 80%, along with its tread rubber composition and vulcanized product, for use in the production of winter tires, improving grip on snow and ice, and exhibiting high wear resistance and low rolling resistance. Summary of the Invention

[0006] The purpose of this invention is to provide a new copolymer gel latex that enables the production of tires with excellent performance. This invention provides a copolymer microgel latex, a method for preparing a copolymer microgel latex, a latex composition, a rubber composition, a vulcanizate, and the application of the vulcanizate in the manufacture of tire treads. The vulcanizate prepared using the copolymer gel latex achieves a good balance in rolling resistance, wet skid resistance, and abrasion resistance, making it suitable for manufacturing tire treads.

[0007] To achieve the above objectives, the first aspect of the present invention provides a copolymer microgel latex, wherein the copolymer in the copolymer microgel latex contains (a) structural units provided by conjugated diene monomers, (b) structural units provided by monovinyl aromatic monomers, (c) structural units provided by vinyl unsaturated carboxylic acid monomers, (d) structural units provided by crosslinking monomers and (e) structural units provided by monomers containing epoxy functional groups;

[0008] In this process, structural unit (e) is grafted onto the surface of the copolymer;

[0009] Based on the total weight of structural units (a)-(e), the content of structural unit (a) is 20-80 wt%, the content of structural unit (b) is 15-75 wt%, the content of structural unit (c) is 0.1-5 wt%, the content of structural unit (d) is 0.1-5 wt%, and the content of structural unit (e) is 3-15 wt%.

[0010] Preferably, the average particle size of the latex particles in the copolymer microgel latex is 90-200 nm.

[0011] Preferably, the copolymer microgel latex has a gel content of 90 wt% or more.

[0012] A second aspect of the present invention provides a method for preparing copolymer microgel latex, the method comprising the following steps:

[0013] (1) In the presence of an initiator, an emulsifier, a vinyl unsaturated carboxylic acid monomer and a portion of a monovinyl aromatic monomer are contacted in a dispersion medium to obtain latex A;

[0014] (2) The conjugated diene monomer, the remaining monovinyl aromatic monomer, the crosslinking monomer and the molecular weight regulator are continuously added to the latex A obtained in step (1) to react and obtain latex B;

[0015] (3) Add monomers containing epoxy functional groups to latex B obtained in step (2) and react to obtain copolymer microgel latex;

[0016] Based on the total weight of the monomers, the amount of conjugated diene monomers is 20-80 wt%, the amount of monovinyl aromatic monomers is 15-75 wt%, the amount of vinyl unsaturated carboxylic acid monomers is 0.1-5 wt%, the amount of crosslinking monomers is 0.1-5 wt%, and the amount of monomers containing epoxy functional groups is 3-15 wt%.

[0017] A third aspect of the present invention provides copolymer microgel latex prepared by the preparation method described above.

[0018] A fourth aspect of the present invention provides a latex composition comprising the copolymer microgel latex as described above.

[0019] A fifth aspect of the present invention provides a rubber composition comprising a solid rubber obtained by coagulating and drying a latex composition as described above.

[0020] A sixth aspect of the present invention provides a vulcanizate obtained by vulcanizing a rubber composition as described above.

[0021] The seventh aspect of the present invention provides the use of the copolymer microgel latex, latex composition, rubber composition or vulcanizate as described above in the manufacture of tire tread.

[0022] The copolymer in the copolymer microgel latex of this invention comprises monomers including conjugated diene monomers, monovinyl aromatic monomers, vinyl unsaturated carboxylic acid monomers, crosslinking monomers, and monomers containing epoxy functional groups. The copolymer surface is grafted with epoxy monomers. The preparation process employs emulsion polymerization. During polymerization, the copolymer microgel latex is obtained by changing the polymerization formula, adding crosslinking monomers, introducing monomers containing epoxy groups, and using optimized process conditions. The copolymer microgel latex has a heterogeneous particle structure, with epoxy groups on the particle surface. The average particle size is preferably 90-200 nm, and the gel content is preferably above 90 wt%. It can be used to prepare rubber compositions and vulcanizates. The vulcanizates exhibit a good balance in rolling resistance, wet skid resistance, and abrasion resistance, making them suitable for manufacturing tire treads. Attached Figure Description

[0023] Figure 1 This is a transmission electron microscope (TEM) image of the microstructure of the copolymer microgel prepared in Example 1. Detailed Implementation

[0024] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0025] The first aspect of the present invention provides a copolymer microgel latex, wherein the copolymer in the copolymer microgel latex contains (a) structural units provided by conjugated diene monomers, (b) structural units provided by monovinyl aromatic monomers, (c) structural units provided by vinyl unsaturated carboxylic acid monomers, (d) structural units provided by crosslinking monomers and (e) structural units provided by monomers containing epoxy functional groups;

[0026] In this process, structural unit (e) is grafted onto the surface of the copolymer;

[0027] Based on the total weight of structural units (a)-(e), the content of structural unit (a) is 20-80 wt%, for example, it can be 20, 30, 40, 50, 60, 70, 80 wt% or any range between any two values, preferably 40-70 wt%; the content of structural unit (b) is 15-75 wt%, for example, it can be 15, 20, 30, 40, 50, 60, 70, 75, 99 wt% or any range between any two values, preferably 25-50 wt%; and the content of structural unit (c) is 0.1-5 wt%, for example, it can be 0.1, 0.5, 1... The content of structural unit (d) is 0.1-5 wt%, for example, it can be 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 wt%, and any range between any two values, preferably 0.5-3 wt%. The content of structural unit (e) is 3-15 wt%, for example, it can be 3, 5, 7, 9, 11, 13, 15 wt%, and any range between any two values, preferably 4-12 wt%.

[0028] The conjugated diene monomer can be a conventional conjugated diene monomer in the art. Preferably, the conjugated diene monomer is a C4-C12 conjugated diene selected from at least one of 1,3-butadiene, isoprene, 1,3-pentadiene, 1,3-hexadiene, phenylbutadiene, and 2,3-dimethylbutadiene. More preferably, it is a C4-C8 conjugated diene, such as 1,3-butadiene and / or isoprene.

[0029] The monovinyl aromatic monomer can be a conventional monovinyl aromatic monomer in the art. Preferably, the monovinyl aromatic monomer is selected from at least one of styrene, p-methylstyrene, o-methylstyrene, m-methylstyrene, p-tert-butylstyrene, p-methoxystyrene, vinylnaphthalene, α-methylstyrene, 4-tert-butylstyrene, 3,5-diethylstyrene, 3,5-di-n-butylstyrene, 4-n-propylstyrene, and 4-dodecylstyrene. More preferably, it is at least one of styrene, p-vinyltoluene, and α-methylstyrene, and more preferably, it is styrene.

[0030] Preferably, the vinyl unsaturated carboxylic acid monomer is selected from at least one of acrylic acid, methacrylic acid, itaconic acid, maleic acid and fumaric acid, and more preferably methacrylic acid and / or itaconic acid.

[0031] Preferably, the crosslinking monomer is selected from at least one of diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, neopentyl glycol meth)acrylate, divinylbenzene, divinylnaphthalene, trimellitic acid trimellitate, trivinylbenzene, trimethylolpropane trimellitate, pentaerythritol trimellitate, pentaerythritol tetra(meth)acrylate, and pentaerythritol tetra(meth)acrylate ethoxylate, and is more preferably divinylbenzene and / or trimellitic acid trimellitate.

[0032] Preferably, the monomer containing the epoxy functional group is glycidyl (meth)acrylate.

[0033] Preferably, the copolymer microgel latex further contains a dispersion medium; more preferably, the dispersion medium is water.

[0034] The total solids content in the copolymer microgel latex can be selected within a wide range. Preferably, the total solids content in the copolymer microgel latex is 30 wt% or more, and more preferably 35-45 wt%. Total solids refer to the content of all solid substances in the latex after removing water and volatile components.

[0035] Preferably, the average particle size of the latex particles in the copolymer microgel latex is 90-200 nm. Particle size was determined using a Malvern Zetasizer 3000HSA laser particle size analyzer.

[0036] Preferably, the gel content of the copolymer microgel latex is 90 wt% or more. The gel content is tested as follows: A certain amount of latex is extracted with ethanol and dried. Approximately 0.2 g of the dried sample (mass m1) is placed in a stainless steel mesh cage. The mesh cage is immersed in a wide-mouth bottle containing 50 mL of toluene and left to stand for 24 hours. The mesh cage is removed, the toluene solvent is evaporated, and the sample is dried in a vacuum oven at 100°C for 2 hours. After cooling to room temperature, the mass (m2) is measured. The latex gel mass fraction is then calculated as m2 / m1.

[0037] Preferably, the particles in the copolymer microgel latex have a heterogeneous structure, specifically a core-shell structure. Particle structure testing: Measurements were performed using a Hitachi H-800 transmission electron microscope, and the latex particles were stained with osmium tetroxide.

[0038] A second aspect of the present invention provides a method for preparing copolymer microgel latex, the method comprising the following steps:

[0039] (1) In the presence of an initiator, an emulsifier, a vinyl unsaturated carboxylic acid monomer and a portion of a monovinyl aromatic monomer are contacted in a dispersion medium to obtain latex A;

[0040] (2) The conjugated diene monomer, the remaining monovinyl aromatic monomer, the crosslinking monomer and the molecular weight regulator are continuously added to the latex A obtained in step (1) to react and obtain latex B;

[0041] (3) Add monomers containing epoxy functional groups to latex B obtained in step (2) and react to obtain copolymer microgel latex;

[0042] Based on the total weight of the monomers, the amount of conjugated diene monomer is 20-80 wt%, for example, it can be 20, 30, 40, 50, 60, 70, 80 wt% or any range between any two values, preferably 40-70 wt%; the amount of monovinyl aromatic monomer is 15-75 wt%, for example, it can be 15, 20, 30, 40, 50, 60, 70, 75, 99 wt% or any range between any two values, preferably 25-50 wt%; and the amount of vinyl unsaturated carboxylic acid monomer is 0.1-5 wt%, for example, it can be 0.1, 0.5, 1, 1... The amount of crosslinking monomer is 0.1-5 wt%, for example, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 wt%, or any range between any two values, preferably 0.5-3 wt%. The amount of monomer containing epoxy functional groups is 3-15 wt%, for example, 3, 5, 7, 9, 11, 13, 15 wt%, or any range between any two values, preferably 4-12 wt%. It should be understood that the total weight of monomers refers to the total weight of conjugated diene monomers, monovinyl aromatic monomers, vinyl unsaturated carboxylic acid monomers, crosslinking monomers, and monomers containing epoxy functional groups.

[0043] The types of monomers mentioned are described in the first aspect and will not be repeated here.

[0044] Preferably, the weight ratio of a portion of the monovinyl aromatic monomer in step (1) to the remaining portion of the monovinyl aromatic monomer in step (2) is 1:1-8, for example, it can be 1:1, 1:2, 1:4, 1:6, 1:8 and any range between any two values, more preferably 1:2-6.

[0045] Preferably, the initiator is a water-soluble persulfate and / or an organic peroxide. The water-soluble persulfate is preferably selected from at least one of potassium persulfate, sodium persulfate, and ammonium persulfate. The organic peroxide is preferably selected from at least one of benzoyl peroxide, tert-butyl hydroperoxide, cumene peroxide, and dicumene peroxide.

[0046] Preferably, the amount of the initiator is 0.1-0.5 wt% based on the total weight of the monomers, for example, it can be 0.1, 0.2, 0.3, 0.4, 0.5 wt% or any range between any two values.

[0047] Preferably, the emulsifier is an anionic surfactant and / or a nonionic surfactant, preferably selected from at least one of fatty acid soaps (e.g., C12-C20 fatty acid soaps, such as soaps of lauric acid, myristic acid, palmitic acid, or stearic acid, such as potassium stearate), rosin acid soaps (e.g., potassium dismutate rosinate), alkyl sulfates (e.g., sodium dodecyl sulfate), alkyl sulfonates (e.g., sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate), and fatty alcohol polyoxyethylene ethers (e.g., C12-18 fatty alcohol polyoxyethylene ethers). Those skilled in the art can select according to need.

[0048] Preferably, the amount of emulsifier used is 1-8 wt% based on the total weight of the monomers, for example, it can be 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 7, 8 wt% and any range between any two values, preferably 1.5-5 wt%.

[0049] Preferably, the molecular weight regulator is n-dodecyl mercaptan and / or tert-dodecyl mercaptan.

[0050] Preferably, the amount of the molecular weight regulator is 0.1-1 wt% based on the total weight of the monomers, for example, it can be 0.1, 0.2, 0.4, 0.6, 0.8, 1 wt%, or any range between any two values.

[0051] Preferably, the dispersion medium is water.

[0052] The amount of the dispersion medium can be selected within a wide range. Preferably, based on the total weight of the monomers, the amount of the dispersion medium is 100-250 wt%.

[0053] Preferably, in step (1), the contact conditions include a contact temperature of 60-70°C and a contact time of 0.3-1.5 hours.

[0054] Preferably, in step (1), the contact conditions are such that the average particle size of latex A is 50-60 nm.

[0055] Preferably, in step (2), the continuous addition time is 2-6 hours, and the reaction temperature is 75-90℃.

[0056] Preferably, in step (3), the continuous addition time is 0.5-2 hours, the reaction temperature is 85-100℃, and the reaction time is 1-3 hours.

[0057] Preferably, the method further includes adding a chelating agent to the contact reaction system in step (1).

[0058] Preferably, the chelating agent is selected from at least one of disodium ethylenediaminetetraacetate, trisodium ethylenediaminetetraacetate, and tetrasodium ethylenediaminetetraacetate.

[0059] Preferably, the amount of the chelating agent is 0.01-0.1 wt% based on the total weight of the monomers.

[0060] A third aspect of the present invention provides copolymer microgel latex prepared by the preparation method described above.

[0061] For a description of the latex, see the first aspect.

[0062] A fourth aspect of the present invention provides a latex composition comprising the copolymer microgel latex as described above.

[0063] Preferably, the latex composition further comprises a second latex. The second latex may be a latex conventional in the art, and preferably, the second latex is a natural latex and / or a styrene-butadiene latex.

[0064] Preferably, based on solid content, the latex composition contains 1-5 wt% copolymer microgel latex and 95-99 wt% second latex.

[0065] The latex composition can be prepared into solid rubber by conventional methods in the art, such as coagulation and drying. Those skilled in the art can operate in accordance with conventional methods in the art, and will not be described in detail here.

[0066] A fifth aspect of the present invention provides a rubber composition comprising a solid rubber obtained by coagulating and drying a latex composition as described above.

[0067] The rubber composition may also contain other additives, such as vulcanizing agents, vulcanization accelerators, reinforcing agents, and activators.

[0068] A sixth aspect of the present invention provides a vulcanizate obtained by vulcanizing a rubber composition as described above.

[0069] The method of vulcanizing the rubber composition is a conventional choice in the art, which is known to those skilled in the art and will not be described in detail here.

[0070] The seventh aspect of the present invention provides the use of the copolymer microgel latex, latex composition, rubber composition or vulcanizate as described above in the manufacture of tire tread.

[0071] The present invention will be described in detail below through embodiments, but the present invention is not limited to the following embodiments.

[0072] The performance indicators of the copolymer microgel latex in the examples were tested according to the following methods.

[0073] Particle size determination: The particle size was determined using a Malvern Zetasizer 3000HSA laser particle size analyzer.

[0074] Method for determining glass transition temperature: Differential scanning calorimetry (DSC) was used.

[0075] Particle structure testing: The particle structure was determined using a Hitachi H-800 transmission electron microscope, and the latex particles were stained with osmium tetroxide.

[0076] Test method for gel content: Extract a certain amount of latex with ethanol and dry it. Take about 0.2 grams of the dry sample (mass m1) and put it into a stainless steel mesh cage. Immerse the mesh cage in a wide-mouth bottle containing 50 mL of toluene and let it stand for 24 hours. Take out the mesh cage, evaporate the toluene solvent, dry it in a vacuum oven at 100℃ for 2 hours, cool it to room temperature, and weigh it (m2). Then the latex gel mass fraction = m2 / m1.

[0077] The content of epoxy-containing monomers (%); the rubber was dissolved in toluene and reprecipitated from methanol, and the procedure was repeated twice to purify the rubber, which was then titrated according to the Jay method [RR Jay; Analytical Chemistry, 36667 (1964)].

[0078] In the following examples, "phm" represents the number of parts by mass of the substance relative to 100 parts by mass of the total weight of the monomers.

[0079] Examples 1-4

[0080] This embodiment illustrates the preparation of the copolymer microgel latex described in this invention.

[0081] The monomer types and addition methods for preparing copolymer microgel latex are shown in Table 1, where the amount of each component in the table is in wt%.

[0082] (1) Add 150 phm deionized water, 2.0 phm potassium disproportionate, 2.0 phm potassium stearate, 0.05 phm tetrasodium ethylenediaminetetraacetate and the monomers styrene and methacrylic acid required for the first step reaction to the polymerization reactor. Set the polymerization reactor temperature to 65°C, add 0.3 phm potassium persulfate, and the reaction time is 30 minutes. The average particle diameter of the copolymer latex prepared is about 50-60 nm, and the glass transition temperature is 100°C.

[0083] (2) Add the monomers styrene, butadiene, trimellitic acid tripropylene ester and 0.5 phm tert-dodecyl mercaptan required for the second reaction to the material after the first reaction. Set the polymerization kettle temperature to 80°C and add the monomers continuously for 4 hours to obtain a microgel latex with a heterogeneous structure.

[0084] (3) Glycidyl methacrylate, the monomer required for the third step reaction, is continuously added to the material after the second step reaction. The polymerization reactor temperature is set to 90°C and the monomer is continuously added for 1 hour. The polymerization reactor temperature is set to 95°C and the reaction is continued for 2 hours to obtain a copolymer microgel latex with surface-grafted epoxy groups. The polymerization conversion rate is about 100%.

[0085] Table 1

[0086]

[0087] Figure 1 This is a transmission electron microscope (TEM) image of the copolymer microgel obtained in Example 1. The image shows the heterogeneous structure of the polymer particles, where the light-colored area is polystyrene and the dark-colored area is a copolymer of butadiene and styrene.

[0088] The performance of the obtained gel was tested, and the test results are shown in Table 2.

[0089] Table 2

[0090] performance Example 1 Example 2 Example 3 Example 4 Average particle size, nm 162 125 128 97 Gel content, % 97 94 91 91 Epoxy group content, % 4.6 4.7 9.4 4.9

[0091] Application Examples

[0092] 1. The data in the application example were determined using the following instruments, equipment, and testing methods:

[0093] (1) Rolling resistance: The rolling power loss was measured using an RSS-II rubber rolling resistance tester (Beijing Wanhui Yifang Technology Development Co., Ltd.).

[0094] Rolling resistance index (%): The rolling resistance index is the percentage of the rolling resistance of other modified rubbers relative to the rolling resistance of pure rubber, based on the rolling resistance measurement value of pure rubber.

[0095] (2) Abrasion resistance test: The abrasion value of the vulcanizate was determined by using a WML-76 Akron abrasion tester in accordance with GB / T 1689-1998.

[0096] Abrasion Index (%): The abrasion index is the percentage of the abrasion volume of the modified rubber relative to the abrasion volume of the pure rubber, based on the abrasion volume measurement of the pure rubber.

[0097] (3) Dynamic mechanical property test (determination of slipperiness): The test was conducted using the DMTA IV (Dynamic Mechanical Thermal Analyzer) manufactured by Rheometric Scientific, USA. The test conditions were 10 Hz, 0.5% strain, and heating rate of 2℃ / min.

[0098] Friction and hysteresis loss of rubber compounds on wet surfaces are related, and the tanδ value at 0°C is usually used to characterize wet skid resistance. The larger the tanδ value at 0°C, the better the tire's traction performance on wet roads.

[0099] Anti-slip index (%): The anti-slip index is the percentage of the anti-slip value of the modified rubber relative to the anti-slip value of the pure rubber, with the tanδ anti-slip value of the pure rubber as the base.

[0100] (4) Mechanical properties: Measured according to relevant standards.

[0101] 2. Raw materials used:

[0102] Styrene-butadiene latex 1502: solid content 20%, styrene binding content 23wt%, Mooney viscosity 45, produced by Sinopec Qilu Branch; sulfuric acid, sodium hydroxide, CA coagulant, carbon black N234, zinc oxide, stearic acid, sulfur, and accelerator TBBS are all commercially available products.

[0103] 3. Co-coagulation method of copolymer microgel latex and styrene-butadiene latex 1502

[0104] The copolymer gel latex and styrene-butadiene latex 1502 were mixed at a certain solid content ratio, with the weight ratio of the copolymer microgel latex solid content to the styrene-butadiene latex 1502 solid content being 3:97. The latex mixture was heated to 55±5℃, and a mixture of sulfuric acid and CA coagulant was added to the latex. The mixture was stirred vigorously, and the pH of the latex was controlled at 3.5±0.3 by adjusting the amount of sulfuric acid added. After coagulation, part of the slurry was filtered off, and the temperature was raised to 60±5℃. NaOH solution was added to adjust the pH to 5.3±0.3. The mixture was then filtered, washed with water, and dried to obtain solid rubber.

[0105] 4. Preparation and vulcanization methods of rubber compound

[0106] One stage of process:

[0107] The process was carried out in a 1.57L Benbury internal mixer (Farrell, UK), with a filler coefficient of 0.7, at 80°C / 80 rpm. The process was as follows: styrene-butadiene rubber raw rubber or the copolymer microgel of this invention combined with styrene-butadiene rubber, carbon black, and other additives (except sulfur and accelerators) were added; the top plug was lowered, and the mixture was mixed for 3 minutes. The rubber was then discharged (at a temperature of 150–160°C).

[0108] Two-stage process:

[0109] The formula for the compound is shown in Table 3, with units of parts by weight.

[0110] The aforementioned masterbatch, after being mixed with sulfur and accelerator, is passed through an XK-160 open mill (a product of Shanghai Rubber Machinery Factory) six times, and then sheeted. It is then vulcanized at 160℃ for the appropriate time T. 90 The rubber was vulcanized, and then the vulcanized rubber sample was made into a standard strip for various mechanical property tests. The results are shown in Table 4.

[0111] Comparative Example 1

[0112] The latex was changed from a mixture of two latexes to a single styrene-butadiene latex 1502, and the rest was the same as in the application example. The specific rubber compound formulation is shown in Table 3, and the vulcanized rubber properties are shown in Table 4.

[0113] Table 3

[0114]

[0115]

[0116] Table 4

[0117]

[0118] As can be seen from the results in Table 4, the rubber composition modified with the copolymer microgel of the present invention achieves a good balance in terms of rolling resistance, wet skid resistance and wear resistance, and is suitable for manufacturing tire tread compounds.

[0119] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A copolymer microgel latex, characterized in that, The copolymer microgel latex contains (a) structural units provided by conjugated diene monomers, (b) structural units provided by monovinyl aromatic monomers, (c) structural units provided by vinyl unsaturated carboxylic acid monomers, (d) structural units provided by crosslinking monomers and (e) structural units provided by monomers containing epoxy functional groups; In this process, structural unit (e) is grafted onto the surface of the copolymer; Based on the total weight of structural units (a)-(e), the content of structural unit (a) is 20-80wt%, the content of structural unit (b) is 15-75wt%, the content of structural unit (c) is 0.1-5wt%, the content of structural unit (d) is 0.1-5wt%, and the content of structural unit (e) is 3-15wt%.

2. The copolymer microgel latex according to claim 1, wherein, The conjugated diene monomer is a C4-C12 conjugated diene; and / or The monovinyl aromatic monomer is selected from at least one of styrene, p-methylstyrene, o-methylstyrene, m-methylstyrene, p-tert-butylstyrene, p-methoxystyrene, vinylnaphthalene, α-methylstyrene, 4-tert-butylstyrene, 3,5-diethylstyrene, 3,5-di-n-butylstyrene, 4-n-propylstyrene, and 4-dodecylstyrene; and / or The vinyl unsaturated carboxylic acid monomer is selected from at least one of acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid; and / or The crosslinking monomer is selected from at least one of diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, neopentyl glycol meth)acrylate, divinylbenzene, divinylnaphthalene, trimellitic acid triacrylate, trivinylbenzene, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and pentaerythritol tetra(meth)acrylate ethoxylate; and / or The monomer containing the epoxy functional group is glycidyl (meth)acrylate.

3. The copolymer microgel latex according to claim 2, wherein, The conjugated diene monomer is selected from at least one of 1,3-butadiene, isoprene, 1,3-pentadiene, 1,3-hexadiene, phenylbutadiene, and 2,3-dimethylbutadiene; and / or The monovinyl aromatic monomer is at least one of styrene, p-vinyltoluene, and α-methylstyrene; and / or The vinyl unsaturated carboxylic acid monomer is methacrylic acid and / or itaconic acid; and / or The crosslinking monomer is divinylbenzene and / or trimellitic acid tripropylene ester.

4. The copolymer microgel latex according to claim 3, wherein, The conjugated diene monomer is 1,3-butadiene and / or isoprene; and / or The monovinyl aromatic monomer is styrene.

5. The copolymer microgel latex according to any one of claims 1-4, wherein, Based on the total weight of structural units (a)-(e), the content of structural unit (a) is 40-70wt%, the content of structural unit (b) is 25-50wt%, the content of structural unit (c) is 0.5-3wt%, the content of structural unit (d) is 0.5-3wt%, and the content of structural unit (e) is 4-12wt%.

6. The copolymer microgel latex according to any one of claims 1-4, wherein, The copolymer microgel latex also contains a dispersion medium.

7. The copolymer microgel latex according to claim 6, wherein, The dispersion medium is water; and / or The total solids content in the copolymer microgel latex is above 30 wt%.

8. The copolymer microgel latex according to claim 7, wherein, The total solids content in the copolymer microgel latex is 40-50 wt%.

9. The copolymer microgel latex according to any one of claims 1-4, wherein, The copolymer microgel latex has an average particle size of 90-200 nm; and / or The copolymer microgel latex has a gel content of 90 wt% or more; and / or The particles in the copolymer microgel latex have a heterogeneous structure.

10. A method for preparing a copolymer microgel latex, characterized in that, The method includes the following steps: (1) In the presence of an initiator, an emulsifier, a vinyl unsaturated carboxylic acid monomer and a portion of a monovinyl aromatic monomer are contacted in a dispersion medium to obtain latex A; (2) The conjugated diene monomer, the remaining monovinyl aromatic monomer, the crosslinking monomer and the molecular weight regulator are continuously added to the latex A obtained in step (1) to react and obtain latex B; (3) Add monomers containing epoxy functional groups to latex B obtained in step (2) and react to obtain copolymer microgel latex; Based on the total weight of the monomers, the amount of conjugated diene monomers is 20-80 wt%, the amount of monovinyl aromatic monomers is 15-75 wt%, the amount of vinyl unsaturated carboxylic acid monomers is 0.1-5 wt%, the amount of crosslinking monomers is 0.1-5 wt%, and the amount of monomers containing epoxy functional groups is 3-15 wt%.

11. The preparation method according to claim 10, wherein, Based on the total weight of monomers, the amount of conjugated diene monomer is 40-70 wt%, the amount of monovinyl aromatic monomer is 25-50 wt%, the amount of vinyl unsaturated carboxylic acid monomer is 0.5-3 wt%, the amount of crosslinking monomer is 0.5-3 wt%, and the amount of monomer containing epoxy functional groups is 4-12 wt%; and / or By weight, the ratio of a portion of the monovinyl aromatic monomer in step (1) to the remaining portion of the monovinyl aromatic monomer in step (2) is 1:1-8.

12. The preparation method according to claim 11, wherein, By weight, the ratio of a portion of the monovinyl aromatic monomer in step (1) to the remaining portion of the monovinyl aromatic monomer in step (2) is 1:2-6.

13. The preparation method according to claim 10, wherein, The initiator is a water-soluble persulfate and / or an organic peroxide; and / or The emulsifier is an anionic surfactant and / or a nonionic surfactant; and / or The molecular weight regulator is n-dodecyl mercaptan and / or tert-dodecyl mercaptan; and / or The dispersion medium is water.

14. The preparation method according to claim 13, wherein, in, The water-soluble persulfate is selected from at least one of potassium persulfate, sodium persulfate, and ammonium persulfate; the organic peroxide is selected from at least one of benzoyl peroxide, tert-butyl hydroperoxide, cumene peroxide, and dicumene peroxide; and / or The emulsifier is selected from at least one of fatty acid soap, rosin acid soap, alkyl sulfate, alkyl sulfonate and fatty alcohol polyoxyethylene ether.

15. The preparation method according to any one of claims 10-14, wherein, Based on the total weight of the monomers, the amount of the initiator is 0.1-0.5 wt%; and / or The amount of the emulsifier is 1-8 wt% based on the total weight of the monomers; and / or Based on the total weight of the monomers, the amount of the molecular weight regulator is 0.1-1 wt%; and / or Based on the total weight of the monomers, the amount of the dispersion medium is 100-250 wt%.

16. The preparation method according to any one of claims 10-14, wherein, In step (1), the contact conditions include a contact temperature of 60-70°C and a contact time of 0.3-1.5 hours; In step (2), the continuous addition time is 2-6 hours, and the reaction temperature is 75-90℃; In step (3), the continuous addition time is 0.5-2 hours, the reaction temperature is 85-100℃, and the reaction time is 1-3 hours.

17. The preparation method according to any one of claims 10-14, wherein, The method also includes adding a chelating agent to the contact reaction system in step (1).

18. The preparation method according to claim 17, wherein, The chelating agent is selected from at least one of disodium ethylenediaminetetraacetate, trisodium ethylenediaminetetraacetate, and tetrasodium ethylenediaminetetraacetate; and / or Based on the total weight of the monomers, the amount of the chelating agent is 0.01-0.1 wt%.

19. The copolymer microgel latex prepared by the preparation method according to any one of claims 10-18.

20. A latex composition, characterized in that, The latex composition comprises the copolymer microgel latex according to any one of claims 1-9 and 19.

21. The latex composition according to claim 20, wherein, The latex composition also contains a second latex.

22. The latex composition according to claim 21, wherein, The second latex is natural latex and / or styrene-butadiene latex; and / or Based on solid content, the latex composition contains 1-5 wt% copolymer microgel latex and 95-99 wt% second latex.

23. A rubber composition, characterized in that, The rubber composition comprises the solid rubber obtained by coagulating and drying the latex composition of claim 22.

24. A vulcanizate, characterized in that, The vulcanized rubber is obtained by vulcanizing the rubber composition according to claim 23.

25. The use of the copolymer microgel latex according to any one of claims 1-9 and 19, the latex composition according to any one of claims 20-22, the rubber composition according to claim 23, or the vulcanizate according to claim 24 in the manufacture of tire treads.

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