Preparation method of lignin / rubber nanocomposite masterbatch and product thereof

Abstract

This invention relates to the field of rubber preparation, specifically to a method for preparing a lignin / rubber nanocomposite masterbatch and its product. The invention involves epoxidizing rubber latex to obtain epoxidized rubber latex, then dynamically mixing the obtained epoxidized rubber latex with lignin slurry. At high speed, the lignin adsorbs onto the epoxidized rubber latex particles, resulting in self-flocculation to obtain the lignin / rubber nanocomposite masterbatch. The lignin exhibits good dispersibility in the lignin / rubber nanocomposite masterbatch, significantly reducing stress defects and improving mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of rubber preparation, and more specifically, to a method for preparing lignin / rubber nanocomposite masterbatch and its product. Background Technology

[0002] Natural rubber, as an elastomer with excellent comprehensive properties, has been widely used in many key fields such as transportation, national defense, aerospace, and medical and health care due to its high elasticity, high tensile strength, excellent insulation and wear resistance, and unique "stretching crystallization" behavior. However, the non-polar molecular structure of natural rubber makes it less effective in solvent resistance, aging resistance, wet slip resistance, and airtightness, thus limiting its application potential in a wider range of scenarios. To overcome these performance shortcomings, current research often employs chemical modification methods, introducing specific functional groups at the double bond positions of its molecular chains to effectively improve material properties.

[0003] Carbon black and silica are two extremely important fillers in the rubber industry, playing a crucial role in improving the performance of rubber products. However, the production of carbon black and silica heavily relies on petrochemical resources, resulting in high energy consumption and the emission of large amounts of carbon dioxide, sulfur oxides, and dust, thus consuming a significant amount of non-renewable resources. Moreover, large-scale production and application of carbon black and silica can have adverse effects on the environment and human health.

[0004] Lignin is an aromatic compound and an important component of plant cell walls. Lignin molecules possess a wide variety and abundance of functional groups, such as phenolic hydroxyl groups, alcoholic hydroxyl groups, and ester methoxy groups. These functional groups endow lignin with good polarity and biocompatibility. Furthermore, lignin contains a large number of benzene ring skeletons, giving it a natural three-dimensional network structure, which allows for good reinforcement when combined with rubber. Therefore, lignin possesses the basic qualities to be used as a reinforcing filler in rubber. However, lignin itself has a relatively large particle size, and the presence of numerous polar groups makes it prone to aggregation in the rubber matrix. Directly mixing lignin with rubber can lead to stress defects in the prepared composite material, resulting in poor performance. Summary of the Invention

[0005] To address the technical problem that direct mixing of lignin and rubber leads to stress defects (poor mechanical properties) in the prepared composite material, this invention provides a method for preparing lignin / rubber nanocomposite masterbatch and its product.

[0006] This invention involves epoxidizing rubber latex to obtain epoxidized rubber latex. The obtained epoxidized rubber latex is then dynamically mixed with lignin slurry. At high speed, the adsorption of lignin on the epoxidized rubber latex particles is utilized to achieve self-flocculation, resulting in a lignin / rubber nanocomposite masterbatch. The lignin exhibits good dispersibility in the lignin / rubber nanocomposite masterbatch, leading to significantly reduced stress defects and improved mechanical properties.

[0007] One of the objectives of this invention is to provide a method for preparing lignin / rubber nanocomposite masterbatch.

[0008] The preparation method includes:

[0009] (1) Rubber latex is subjected to epoxidation treatment to obtain epoxidized rubber latex; (2) Grind lignin with water to obtain lignin slurry; (3) Mix and stir the epoxidized rubber latex with the lignin slurry, and collect the solid.

[0010] As a preferred embodiment, the preparation method includes: (4) cutting the collected solid into pieces and washing it with water, then drying it to a constant weight.

[0011] This invention first prepares lignin into a lignin slurry and then mixes it with rubber latex. All raw materials are in liquid state, and mixing occurs in this liquid state. The preparation method of this invention is a wet preparation method; compared to the dry method (where lignin is directly mixed with rubber during the compounding process), the wet preparation method allows lignin and rubber molecular chains to interact in the liquid phase, increasing the contact volume between lignin and rubber and resulting in more uniform dispersion of lignin in the rubber latex. Compared to the dry method, the lignin / rubber nanocomposite masterbatch prepared by the method of this invention exhibits significantly improved lignin dispersion in the epoxidized natural rubber matrix. Transmission electron microscopy (TEM) images show more uniform lignin dispersion, smaller lignin aggregates, and significantly improved dispersibility.

[0012] This invention involves epoxidizing the rubber before mixing it with lignin slurry to obtain epoxidized rubber latex. The epoxidation treatment imparts epoxy groups to the main chain of the epoxidized rubber latex. Lignin itself is a natural polymer with a three-dimensional network structure, containing polar functional groups such as phenolic hydroxyl and alcoholic hydroxyl groups on its molecular chain. These functional groups enable it to form a colloidal network in water. Compared to untreated rubber latex, the epoxy groups on the main chain of the epoxidized rubber latex interact strongly with the phenolic hydroxyl groups of lignin. This results in a tighter and stronger bond between lignin and the epoxidized rubber latex when lignin performs its bridging function, achieving self-flocculation. Therefore, the preparation method of this invention does not require a flocculant.

[0013] In step (1), the rubber latex can be any existing type of rubber latex. As a preferred option, the rubber latex is natural rubber latex.

[0014] In step (1), the solid content (dry rubber mass content) of the rubber latex is 20-40%, for example 25%, 30%, or 35%.

[0015] In step (1), the epoxy degree of the prepared epoxidized rubber latex is 10-60%, for example 15, 20, 25, 30, 35, 40, 45, 50, 55, preferably 15-50%. In epoxidized rubber, epoxy groups partially replace C=C double bonds. Epoxy degree refers to the molar percentage of epoxidized C=C double bonds relative to the total number of C=C double bonds in the rubber molecular chain.

[0016] In step (1), the epoxidation treatment can be performed using conventional methods for rubber epoxidation. As a preferred embodiment, the epoxidation treatment includes: adding a stabilizer to the rubber latex, stirring until the latex is stable, adding an epoxidizing agent and stirring to react, adjusting the pH of the system to 6-7 after the reaction stops, and obtaining the epoxidized rubber latex. As a more preferred embodiment, the reaction conditions are: water bath temperature 35-50℃, stirring speed 140-200 r / min, and adjusting the pH of the system with ammonia.

[0017] The stabilizer may be selected from at least one of nonionic emulsifiers and cationic emulsifiers; preferably, cationic emulsifier OTAC is selected.

[0018] The amount of stabilizer relative to the rubber latex can be a conventional amount. Preferably, the amount of stabilizer relative to the rubber latex is 2-3 wt%.

[0019] The epoxidizing agent can be any one or more existing epoxidizing agents capable of epoxidizing rubber. As a preferred embodiment, the epoxidizing agent can be an epoxidation system composed of formic acid and hydrogen peroxide, or an epoxidation system composed of acetic acid and hydrogen peroxide.

[0020] The amount of the epoxidizing agent relative to the rubber latex can be a conventional amount. Preferably, the amount of the epoxidizing agent relative to the rubber latex is 25-35 wt%.

[0021] In step (2), the lignin can be any existing lignin or its derivatives. Preferably, the lignin is enzymatically hydrolyzed lignin. Compared to other lignins and their derivatives, enzymatically hydrolyzed lignin binds more tightly and firmly to epoxidized rubber latex, exhibiting stronger self-flocculation ability, greatly promoting the formation and stability of the flocculated network, and resulting in higher yield.

[0022] In step (2), the mass ratio of lignin to water is 5~15:100, for example 6:100, 7:100, 8:100, 10:100, 11:100, 12:100, 13:100, or 14:100. At this point, the mass concentration of the prepared lignin slurry is 5~15%.

[0023] In step (2), the grinding can be performed using conventional grinding methods. As a preferred option, a colloid mill is used for grinding; specifically, lignin is initially mixed with water and then poured into a colloid mill for grinding. The colloid mill, through the high-speed relative movement of the fixed and moving teeth, subjectes the lignin to strong shearing forces, effectively pulverizing, emulsifying, and homogenizing it. After grinding, the particle size of the lignin slurry is refined.

[0024] In step (2), conventional grinding conditions can be used. Preferably, the grinding frequency is 40-70 Hz, more preferably 50-60 Hz. Preferably, the grinding time is 20-60 min, more preferably 30-40 min. Preferably, the grinding temperature is 20-40℃, more preferably 25-35℃.

[0025] Before step (2), it is preferable to filter out larger particles of lignin powder through a filter screen, and then mix the remaining powder with water and grind it.

[0026] In step (3), after the epoxidized rubber latex and lignin slurry are mixed to form a mixed system, the lignin crosslinking network and the interaction between the epoxy groups of lignin and the epoxidized rubber latex are used to carry out self-flocculation during stirring, and the solid is collected to obtain the lignin / rubber nanocomposite masterbatch.

[0027] In step (3), the preferred method for mixing the epoxidized rubber latex and the lignin slurry is to pour the lignin slurry into the epoxidized rubber latex all at once. This process allows a large amount of lignin to be incorporated into the latex system, and the stirring action accelerates the construction of the cross-linking system and promotes self-flocculation.

[0028] In step (3), the mass ratio of dry rubber in epoxidized rubber latex to lignin in lignin slurry is 100:1~40, for example 100:5, 100:10, 100:15, 100:20, 100:25, 100:30, 100:35, preferably 100:5~20.

[0029] In step (3), the stirring speed is preferably 150~250 r / min, for example 180 r / min, 200 r / min, or 230 r / min.

[0030] In step (3), the mixing and stirring temperature is preferably 25~45℃, for example 30, 35, 40℃.

[0031] In step (4), the drying temperature is preferably 50~70℃.

[0032] The lignin / rubber nanocomposite masterbatch prepared by the method described above exhibits good lignin dispersion in the masterbatch.

[0033] The second objective of this invention is to provide a lignin / rubber nanocomposite masterbatch.

[0034] The lignin / rubber nanocomposite masterbatch is prepared by the preparation method described in one of the objectives of the invention.

[0035] The third objective of this invention is to provide an epoxidized nanocomposite rubber material.

[0036] The epoxidized nanocomposite rubber material is prepared by mixing raw materials including lignin / rubber nanocomposite masterbatch; the lignin / rubber nanocomposite masterbatch is the lignin / rubber nanocomposite masterbatch prepared by the preparation method described in one of the invention objectives or the lignin / rubber nanocomposite masterbatch described in another of the invention objectives.

[0037] During the mixing and vulcanization process, the epoxy groups in the lignin / rubber nanocomposite masterbatch undergo a ring-opening reaction with the phenolic hydroxyl groups on the surface of the lignin particles, forming covalent bonds between the two phases, which improves the bonding force between the rubber matrix and the lignin filler. Furthermore, due to the combined effect of temperature and shear force during the mixing process, the bonding process between the epoxy groups and the lignin filler is accelerated, resulting in a more uniform dispersion of the lignin filler.

[0038] The epoxidized nanocomposite rubber material, as a preferred embodiment, is prepared by mixing raw materials comprising the following components; the components and their weight parts are as follows: 100 parts by weight of lignin / rubber nanocomposite masterbatch; Anti-aging agent: 1-4 parts by weight, preferably 2-3 parts by weight; Zinc oxide 1 to 10 parts by weight, preferably 3 to 7 parts by weight; Stearic acid 1-4 parts by weight, preferably 2-3 parts by weight; The accelerator is 1 to 4 parts by weight, preferably 2 to 3 parts by weight; The vulcanizing agent is 0.5 to 5 parts by weight, preferably 1 to 4 parts by weight.

[0039] The antioxidant can be selected from any one or more antioxidants currently available for use in the rubber industry. As a preferred embodiment, the antioxidant can be antioxidant 4020.

[0040] The accelerator can be selected from any one or more existing accelerators that can be used in the rubber industry. Preferably, the accelerator can be selected from at least one of accelerator CZ and accelerator DMZ. When the accelerator consists of accelerator CZ and accelerator DMZ, the mass ratio of accelerator CZ to accelerator DMZ can be 3:1.

[0041] The vulcanizing agent can be selected from any one or more vulcanizing agents currently available for use in the rubber industry. Preferably, the vulcanizing agent is sulfur.

[0042] The fourth objective of this invention is to provide a method for preparing the epoxidized nanocomposite rubber material described in the third objective of this invention.

[0043] The preparation method of the nanocomposite rubber material includes: heat-treating the lignin / rubber nanocomposite masterbatch using an internal mixer to obtain heat-treated masterbatch; and mixing the heat-treated masterbatch with other optional raw materials.

[0044] The internal temperature of the internal mixer is preferably 100~150℃, the residence time is preferably 1~6 minutes, and the rotor speed is preferably 30~50 r / min.

[0045] The heat-treated masterbatch can be compounded using conventional rubber compounding processes. Specifically, the heat-treated masterbatch can be compounded with other raw materials. For example, the compounding process includes: first compounding using an internal mixer, and then compounding using an open mill.

[0046] As a specific solution, the preparation method of the nanocomposite rubber material includes: heat-treating the lignin / rubber nanocomposite masterbatch at low speed using a mixer extruder to obtain a heat-treated masterbatch; mixing the heat-treated masterbatch, zinc oxide, stearic acid and antioxidant using a mixer, and then adding an accelerator and sulfur to a two-roll mill for mixing.

[0047] Compared to conventional rubber mixing processes, this invention first uses an internal mixer to heat-treat the lignin / rubber nanocomposite masterbatch. On the one hand, this effectively solves the problem of material dispersion that occurs in traditional heat treatment methods, preventing lignin from scattering and ensuring stable material feeding. On the other hand, the high shear force of the internal mixer enables the epoxy groups to combine with lignin more quickly and allows the epoxy groups to react better with phenolic hydroxyl groups, resulting in uniform dispersion of the filler.

[0048] Compared with the prior art, the beneficial effects of the present invention are as follows: Compared to the dry method, the lignin in the lignin / rubber nanocomposite masterbatch prepared by the method of the present invention has significantly improved dispersion in the epoxidized natural rubber matrix. TEM (transmission electron microscopy) shows that the lignin is more uniformly dispersed, the lignin aggregates are smaller, and the dispersibility is also significantly improved.

[0049] The preparation method of this invention does not require flocculants. First, the rubber latex undergoes epoxidation treatment. Strong interactions occur between the epoxy groups on the main chain of the epoxidized rubber latex and the phenolic hydroxyl groups of lignin. This makes the lignin, in its bridging role, more tightly and firmly bonded to the epoxidized rubber latex, achieving self-flocculation.

[0050] The epoxy groups in the lignin / rubber nanocomposite masterbatch provided by this invention undergo ring-opening reactions with the phenolic hydroxyl groups on the surface of lignin particles during mixing and vulcanization, forming covalent bonds between the two phases. Furthermore, the interaction between the epoxy groups and the lignin filler is accelerated during mixing due to the combined effects of temperature and shear force, resulting in more uniform dispersion of the lignin filler. Using this lignin / rubber nanocomposite masterbatch as a masterbatch for preparing nanocomposite rubber materials can improve the compatibility between lignin and epoxidized natural rubber, solve the problems of excessively large lignin particle size and uneven dispersion, and simultaneously meet the trend of green tire applications. Attached Figure Description

[0051] Figure 1 Transmission electron microscopy (TEM) images of the nanocomposite rubber materials prepared in Examples 1-4 and Comparative Examples 1-4. Detailed Implementation

[0052] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0053] Unless otherwise specified, the raw materials used in the following examples and comparative examples are all commercially available products.

[0054] The natural rubber latex is LA-SPX from Hainan Rubber Group; The enzymatically hydrolyzed lignin was Ligin EL-100 from Shandong Longli Biotechnology Co., Ltd. Sodium lignosulfonate is MN wood pulp from Tianjin Yezi Chemical Technology Co., Ltd.; Calcium lignosulfonate is CAL-A2 from Shanghai Tingruo Chemical Co., Ltd. Alkali lignin is KL19288 from Shanghai Kanglang Biotechnology Co., Ltd.

[0055] Example 1 Step 1: Take 916g of natural rubber latex with a dry rubber content of 60% and put it into a 5L reactor. Add 105g of water to dilute it to a dry rubber content of 54%. Add 36.6g of stabilizer OP-10. Set the stirring speed to 150r / min and stir for 30 minutes. Then add 237g of formic acid with a mass concentration of 85% and 904g of hydrogen peroxide. React in a closed container in a 40℃ water bath for 6 hours. Stop the reaction and add ammonia dropwise until the pH reaches 6.5 to obtain an epoxidized natural rubber latex with a dry rubber content of 25% and an epoxy degree of 30.

[0056] Step 2: Weigh 100g of enzymatically hydrolyzed lignin solid powder, add 900g of water, stir and mix, then pour into a colloid mill. Grind at 70Hz and 25℃ for 10 minutes, then turn off the colloid mill and collect the slurry from the bottom outlet to obtain lignin slurry.

[0057] Step 3: Weigh 687g of the epoxidized natural rubber latex prepared in Step 1 and 63g of the lignin slurry prepared in Step 2 and mix them to obtain a mixture. Stir the mixture at 40℃ and 200 rpm for 30 minutes. After stirring, the mixture will flocculate from a liquid state into a block. Remove the block, cut it into pieces, wash it with water, and dry it in a 60℃ oven until constant weight to obtain 178g of wet-prepared lignin / rubber nanocomposite masterbatch.

[0058] Step 4: Weigh out 125.7 parts by weight of the lignin / rubber nanocomposite masterbatch prepared in Step 3, 6.28 parts by weight of zinc oxide, 2.51 parts by weight of stearic acid, 2.51 parts by weight of antioxidant 4020, 1.25 parts by weight of accelerator DM, 2.51 parts by weight of accelerator CZ, and 2.51 parts by weight of sulfur. Place the lignin / rubber nanocomposite masterbatch into a Hacker internal mixer. Set the temperature of the three zones of the internal mixer to 150°C and the residence time to 1 minute to obtain a heat-treated masterbatch. Add the heat-treated masterbatch to the internal mixer. Set the temperature of the internal mixer to 60°C and the speed to 60 r / min. Mix for 1 minute, then add zinc oxide, stearic acid, and antioxidant and mix for 2 minutes. Discharge the material to obtain a compound. Sheet the compound on a two-roll mill with cooling water and lower the temperature to room temperature. Then, add the accelerator and sulfur in sequence on the two-roll mill. Cut the material five times from left to right, form three triangular clumps, and roll it three times to obtain the nanocomposite rubber material.

[0059] Example 2 Step 1: Take 916g of natural rubber latex with a dry rubber content of 60% and put it into a 5L reactor. Add 105g of water to dilute it to a dry rubber content of 54%. Add 36.6g of stabilizer OP-10. Set the stirring speed to 150r / min and stir for 30 minutes. Then add 237g of formic acid with a mass concentration of 85% and 904g of hydrogen peroxide. React in a closed container in a 40℃ water bath for 6 hours. Stop the reaction and add ammonia dropwise until the pH reaches 6.5 to obtain an epoxidized natural rubber latex with a dry rubber content of 25% and an epoxy degree of 30.

[0060] Step 2: Weigh 100g of enzymatically hydrolyzed lignin solid powder, add 900g of water, stir and mix, then pour into a colloid mill. Grind at 70Hz and 25℃ for 10 minutes, then turn off the colloid mill and collect the slurry from the bottom outlet to obtain lignin slurry.

[0061] Step 3: Weigh 687g of the epoxidized natural rubber latex prepared in Step 1 and 126g of the lignin slurry prepared in Step 2 and mix them to obtain a mixture. Stir the mixture at 40℃ and 200 rpm for 30 minutes. After stirring, the mixture will flocculate from a liquid state into a rubber block. Remove the rubber block, cut it into pieces, wash it with water, and dry it in a 60℃ oven until constant weight to obtain 183g of wet-prepared lignin / rubber nanocomposite masterbatch.

[0062] Step 4: Weigh out 125.7 parts by weight of the lignin / rubber nanocomposite masterbatch prepared in Step 3, 6.28 parts by weight of zinc oxide, 2.51 parts by weight of stearic acid, 2.51 parts by weight of antioxidant 4020, 1.25 parts by weight of accelerator DM, 2.51 parts by weight of accelerator CZ, and 2.51 parts by weight of sulfur. Place the lignin / rubber nanocomposite masterbatch into a Hacker internal mixer. Set the temperature of the three zones of the internal mixer to 150°C and the residence time to 1 minute to obtain a heat-treated masterbatch. Add the heat-treated masterbatch to the internal mixer. Set the temperature of the internal mixer to 60°C and the speed to 60 r / min. Mix for 1 minute, then add zinc oxide, stearic acid, and antioxidant and mix for 2 minutes. Discharge the material to obtain a compound. Sheet the compound on a two-roll mill with cooling water and lower the temperature to room temperature. Then, add the accelerator and sulfur in sequence on the two-roll mill. Cut the material five times from left to right, form three triangular clumps, and roll it three times to obtain the nanocomposite rubber material.

[0063] Example 3 Step 1: Take 916g of natural rubber latex with a dry rubber content of 60% and put it into a 5L reactor. Add 105g of water to dilute it to a dry rubber content of 54%. Add 36.6g of stabilizer OP-10. Set the stirring speed to 150r / min and stir for 30 minutes. Then add 237g of formic acid with a mass concentration of 85% and 904g of hydrogen peroxide. React in a closed container in a 40℃ water bath for 6 hours. Stop the reaction and add ammonia dropwise until the pH reaches 6.5 to obtain an epoxidized natural rubber latex with a dry rubber content of 25% and an epoxy degree of 30.

[0064] Step 2: Weigh 100g of enzymatically hydrolyzed lignin solid powder, add 900g of water, stir and mix it, then pour it into a colloid mill. Grind it at 70Hz and 25℃ for 10 minutes, then turn off the colloid mill and collect the slurry from the bottom outlet to obtain lignin slurry. Step 3: Weigh 687g of the epoxidized natural rubber latex prepared in Step 1 and mix it with 189g of the lignin slurry prepared in Step 2 to obtain a mixture. Stir the mixture at 40℃ and 200 rpm for 30 minutes. After stirring, the mixture will flocculate from a liquid state into a block. Remove the block, cut it into pieces, wash it with water, and dry it in a 60℃ oven until constant weight to obtain 188g of wet-prepared lignin / rubber nanocomposite masterbatch.

[0065] Step 4: Weigh out 125.7 parts by weight of the lignin / rubber nanocomposite masterbatch prepared in Step 3, 6.28 parts by weight of zinc oxide, 2.51 parts by weight of stearic acid, 2.51 parts by weight of antioxidant 4020, 1.25 parts by weight of accelerator DM, 2.51 parts by weight of accelerator CZ, and 2.51 parts by weight of sulfur. Place the lignin / rubber nanocomposite masterbatch into a Hacker internal mixer. Set the temperature of the three zones of the internal mixer to 150°C and the residence time to 1 minute to obtain a heat-treated masterbatch. Add the heat-treated masterbatch to the internal mixer. Set the temperature of the internal mixer to 60°C and the speed to 60 r / min. Mix for 1 minute, then add zinc oxide, stearic acid, and antioxidant and mix for 2 minutes. Discharge the material to obtain a compound. Sheet the compound on a two-roll mill with cooling water and lower the temperature to room temperature. Then, add the accelerator and sulfur in sequence on the two-roll mill. Cut the material five times from left to right, form three triangular clumps, and roll it three times to obtain the nanocomposite rubber material.

[0066] Example 4 Step 1: Take 916g of natural rubber latex with a dry rubber content of 60% and put it into a 5L reactor. Add 105g of water to dilute it to a dry rubber content of 54%. Add 36.6g of stabilizer OP-10. Set the stirring speed to 150r / min and stir for 30 minutes. Then add 237g of formic acid with a mass concentration of 85% and 904g of hydrogen peroxide. React in a closed container in a 40℃ water bath for 6 hours. Stop the reaction and add ammonia dropwise until the pH reaches 6.5 to obtain an epoxidized natural rubber latex with a dry rubber content of 25% and an epoxy degree of 30.

[0067] Step 2: Weigh 100g of enzymatically hydrolyzed lignin solid powder, add 900g of water, stir and mix it, then pour it into a colloid mill. Grind it at 70Hz and 25℃ for 10 minutes, then turn off the colloid mill and collect the slurry from the bottom outlet to obtain lignin slurry. Step 3: Weigh 687g of the epoxidized natural rubber latex prepared in Step 1 and 252g of the lignin slurry prepared in Step 2 and mix them to obtain a mixture. Stir the mixture at 40℃ and 200 rpm for 30 minutes. After stirring, the mixture will flocculate from a liquid state into a block. Remove the block, cut it into pieces, wash it with water, and dry it in a 60℃ oven until constant weight to obtain 194g of wet-prepared lignin / rubber nanocomposite masterbatch.

[0068] Step 4: Weigh out 125.7 parts by weight of the lignin / rubber nanocomposite masterbatch prepared in Step 3, 6.28 parts by weight of zinc oxide, 2.51 parts by weight of stearic acid, 2.51 parts by weight of antioxidant 4020, 1.25 parts by weight of accelerator DM, 2.51 parts by weight of accelerator CZ, and 2.51 parts by weight of sulfur. Place the lignin / rubber nanocomposite masterbatch into a Hacker internal mixer. Set the temperature of the three zones of the internal mixer to 150°C and the residence time to 1 minute to obtain a heat-treated masterbatch. Add the heat-treated masterbatch to the internal mixer. Set the temperature of the internal mixer to 60°C and the speed to 60 r / min. Mix for 1 minute, then add zinc oxide, stearic acid, and antioxidant and mix for 2 minutes. Discharge the material to obtain a compound. Sheet the compound on a two-roll mill with cooling water and lower the temperature to room temperature. Then, add the accelerator and sulfur in sequence on the two-roll mill. Cut the material five times from left to right, form three triangular clumps, and roll it three times to obtain the nanocomposite rubber material.

[0069] Example 5 Step 1: Take 916g of natural rubber latex with a dry rubber content of 60% and put it into a 5L reactor. Add 105g of water to dilute it to a dry rubber content of 54%. Add 36.6g of stabilizer OP-10. Set the stirring speed to 150r / min and stir for 30 minutes. Then add 237g of formic acid with a mass concentration of 85% and 904g of hydrogen peroxide. React in a closed container in a 40℃ water bath for 6 hours. Stop the reaction and add ammonia dropwise until the pH reaches 6.5 to obtain an epoxidized natural rubber latex with a dry rubber content of 25% and an epoxy degree of 30.

[0070] Step 2: Weigh 100g of sodium lignosulfonate solid powder, add 900g of water, stir and mix, then pour into a colloid mill. Grind at 70Hz and 25℃ for 10 minutes, then turn off the colloid mill and collect the slurry from the bottom outlet to obtain lignin slurry.

[0071] Step 3: Weigh 687g of the epoxidized natural rubber latex prepared in Step 1 and 63g of the lignin slurry prepared in Step 2 and mix them to obtain a mixture. Stir the mixture at 40℃ and 200 rpm for 30 minutes. After stirring, the mixture will flocculate from a liquid state into a rubber block. Remove the rubber block, cut it into pieces, wash it with water, and dry it in a 60℃ oven until constant weight to obtain 138g of wet-prepared lignin / rubber nanocomposite masterbatch.

[0072] Compared to Example 1, the yield of the lignin / rubber nanocomposite masterbatch in Example 5 decreased by 40 g. Compared to Example 5, the yield of the lignin / rubber nanocomposite masterbatch in Example 1 increased by 28.9%. The only difference between Example 5 and Example 1 is the type of lignin used in step two: Example 1 used enzymatically hydrolyzed lignin, while Example 5 used sodium lignin sulfonate. This indicates that, compared to sodium lignin sulfonate, enzymatically hydrolyzed lignin exhibits stronger self-flocculation ability with epoxidized rubber latex.

[0073] Example 6 Step 1: Take 916g of natural rubber latex with a dry rubber content of 60% and put it into a 5L reactor. Add 105g of water to dilute it to a dry rubber content of 54%. Add 36.6g of stabilizer OP-10. Set the stirring speed to 150r / min and stir for 30 minutes. Then add 237g of formic acid with a mass concentration of 85% and 904g of hydrogen peroxide. React in a closed container in a 40℃ water bath for 6 hours. Stop the reaction and add ammonia dropwise until the pH reaches 6.5 to obtain an epoxidized natural rubber latex with a dry rubber content of 25% and an epoxy degree of 30.

[0074] Step 2: Weigh 100g of calcium lignosulfonate solid powder, add 900g of water, stir and mix, then pour into a colloid mill. Grind at 70Hz and 25℃ for 10 minutes, then turn off the colloid mill and collect the slurry from the bottom outlet to obtain lignin slurry.

[0075] Step 3: Weigh 687g of the epoxidized natural rubber latex prepared in Step 1 and 63g of the lignin slurry prepared in Step 2 and mix them to obtain a mixture. Stir the mixture at 40℃ and 200 rpm for 30 minutes. After stirring, the mixture will flocculate from a liquid state into a rubber block. Remove the rubber block, cut it into pieces, wash it with water, and dry it in a 60℃ oven until constant weight to obtain 145 wet-processed lignin / rubber nanocomposite masterbatch.

[0076] Compared to Example 1, the yield of the lignin / rubber nanocomposite masterbatch in Example 6 decreased by 33 g. Compared to Example 6, the yield of the lignin / rubber nanocomposite masterbatch in Example 1 increased by 22.7%. The only difference between Example 6 and Example 1 is the type of lignin used: Example 1 used enzymatically hydrolyzed lignin, while Example 6 used calcium lignin sulfonate. This indicates that enzymatically hydrolyzed lignin exhibits stronger self-flocculation ability with epoxidized rubber latex compared to calcium lignin sulfonate.

[0077] Example 7 Step 1: Take 916g of natural rubber latex with a dry rubber content of 60% and put it into a 5L reactor. Add 105g of water to dilute it to a dry rubber content of 54%. Add 36.6g of stabilizer OP-10. Set the stirring speed to 150r / min and stir for 30 minutes. Then add 237g of formic acid with a mass concentration of 85% and 904g of hydrogen peroxide. React in a closed container in a 40℃ water bath for 6 hours. Stop the reaction and add ammonia dropwise until the pH reaches 6.5 to obtain an epoxidized natural rubber latex with a dry rubber content of 25% and an epoxy degree of 30.

[0078] Step 2: Weigh 100g of alkali lignin powder, add 900g of water, stir and mix, then pour into a colloid mill. Grind at 70Hz and 25℃ for 10 minutes, then turn off the colloid mill and collect the slurry from the bottom outlet to obtain lignin slurry.

[0079] Step 3: Weigh 687g of the epoxidized natural rubber latex prepared in Step 1 and 63g of the lignin slurry prepared in Step 2 and mix them to obtain a mixture. Stir the mixture at 40℃ and 200 rpm for 30 minutes. After stirring, a small amount of the mixture will flocculate from the liquid state into a rubber block. Take out the rubber block, cut it into pieces, wash it with water, and dry it in a 60℃ oven until constant weight to obtain 131g of wet-prepared lignin / rubber nanocomposite masterbatch.

[0080] Compared to Example 1, the yield of the lignin / rubber nanocomposite masterbatch in Example 7 decreased by 47 g. Compared to Example 7, the yield of the lignin / rubber nanocomposite masterbatch in Example 1 increased by 35.9%. The only difference between Example 7 and Example 1 is the type of lignin used in step two: Example 1 used enzymatically hydrolyzed lignin, while Example 7 used alkali lignin. This indicates that enzymatically hydrolyzed lignin exhibits stronger self-flocculation ability with epoxidized rubber latex compared to alkali lignin.

[0081] Comparative Example 1 Step 1: Take 916g of natural rubber latex with a dry rubber content of 60% and put it into a 5L reactor. Add 916g of water to dilute it to a dry rubber content of 30%. Add 36.6g of stabilizer OP-10. Set the stirring speed to 150r / min and stir for 30 minutes. Then add 237g of formic acid with a mass concentration of 85% and 904g of hydrogen peroxide. React in a closed container in a 40℃ water bath for 6 hours. Stop the reaction and add ammonia dropwise until the pH reaches 6.5. Epoxidized natural rubber latex with a dry rubber content of 18.3% and an epoxy degree of 30 is obtained.

[0082] Step 2: Weigh 687g of the epoxidized natural rubber latex prepared in Step 1, weigh 1L of anhydrous ethanol and pour it into the latex to cause the latex to flocculate and obtain a solid rubber block. Cut the rubber block into small pieces, wash it repeatedly with deionized water, and dry it in a 60℃ oven until constant weight to obtain the dry epoxidized natural rubber.

[0083] Step 3: Weigh out 125.7 parts by weight of the epoxidized natural rubber dry rubber prepared in Step 2, 6.28 parts by weight of zinc oxide, 2.51 parts by weight of stearic acid, 2.51 parts by weight of antioxidant 4020, 1.25 parts by weight of accelerator DM, 2.51 parts by weight of accelerator CZ, and 2.51 parts by weight of sulfur. Place the epoxidized natural rubber dry rubber into a Hacker internal mixer. Set the mixer temperature to 60℃ and the speed to 60 r / min. Mix for 1 minute, then add zinc oxide, stearic acid, and antioxidant and mix for 2 minutes. Then add 6.3 parts by weight of lignin powder, discharge the mixture, and obtain the compound. Set the temperature of the three zones of the internal mixer to 150℃, then put the rubber compound back into the internal mixer, let it stay for 1 minute, and then take it out. Sheet the rubber compound on a two-roll mill with cooling water and lower the temperature to room temperature. Then add the accelerator and sulfur in sequence on the two-roll mill, cut it with the left and right cutters 5 times, make three triangular wraps, and roll it 3 times to obtain the nano-composite rubber material.

[0084] Comparative Example 2 Step 1: Take 916g of natural rubber latex with a dry rubber content of 60% and put it into a 5L reactor. Add 916g of water to dilute it to a dry rubber content of 30%. Add 36.6g of stabilizer OP-10. Set the stirring speed to 150r / min and stir for 30 minutes. Then add 237g of 85% formic acid and 904g of hydrogen peroxide. React in a closed container in a 40℃ water bath for 6 hours. Stop the reaction and add ammonia dropwise until the pH reaches 6.5. Epoxidized natural rubber latex with a dry rubber content of 18.3% and an epoxy degree of 30 is obtained.

[0085] Step 2: Weigh 687g of the epoxidized natural rubber latex prepared in Step 1, weigh 1L of anhydrous ethanol and pour it into the latex to cause the latex to flocculate and obtain a solid rubber block. Cut the rubber block into small pieces, wash it repeatedly with deionized water, and dry it in a 60℃ oven until constant weight to obtain the dry epoxidized natural rubber.

[0086] Step 3: Weigh out 125.7 parts by weight of the epoxidized natural rubber dry rubber prepared in Step 2, 6.28 parts by weight of zinc oxide, 2.51 parts by weight of stearic acid, 2.51 parts by weight of antioxidant 4020, 1.25 parts by weight of accelerator DM, 2.51 parts by weight of accelerator CZ, and 2.51 parts by weight of sulfur. Place the epoxidized natural rubber dry rubber into a Hacker internal mixer. Set the mixer temperature to 60℃ and the speed to 60 r / min. Mix for 1 minute, then add zinc oxide, stearic acid, and antioxidant and mix for 2 minutes. Then add 12.6 parts by weight of lignin powder, discharge the mixture, and obtain the compound. Set the temperature of the three zones of the internal mixer to 150℃, then put the rubber compound back into the internal mixer, let it stay for 1 minute, and then take it out. Sheet the rubber compound on a two-roll mill with cooling water and lower the temperature to room temperature. Then add the accelerator and sulfur in sequence on the two-roll mill, cut it with the left and right cutters 5 times, make three triangular wraps, and roll it 3 times to obtain the nano-composite rubber material.

[0087] Comparative Example 3 Step 1: Take 916g of natural rubber latex with a dry rubber content of 60% and put it into a 5L reactor. Add 916g of water to dilute it to a dry rubber content of 30%. Add 36.6g of stabilizer OP-10. Set the stirring speed to 150r / min and stir for 30 minutes. Then add 237g of formic acid with a mass concentration of 85% and 904g of hydrogen peroxide. React in a closed container in a 40℃ water bath for 6 hours. Stop the reaction and add ammonia dropwise until the pH reaches 6.5. Epoxidized natural rubber latex with a dry rubber content of 18.3% and an epoxy degree of 30 is obtained.

[0088] Step 2: Weigh 687g of the epoxidized natural rubber latex prepared in Step 1, weigh 1L of anhydrous ethanol and pour it into the latex to cause the latex to flocculate and obtain a solid rubber block. Cut the rubber block into small pieces, wash it repeatedly with deionized water, and dry it in a 60℃ oven until constant weight to obtain the dry epoxidized natural rubber.

[0089] Step 3: Weigh out 125.7 parts by weight of the epoxidized natural rubber dry rubber prepared in Step 2, 6.28 parts by weight of zinc oxide, 2.51 parts by weight of stearic acid, 2.51 parts by weight of antioxidant 4020, 1.25 parts by weight of accelerator DM, 2.51 parts by weight of accelerator CZ, and 2.51 parts by weight of sulfur. Place the epoxidized natural rubber dry rubber into a Hacker internal mixer. Set the mixer temperature to 60℃ and the speed to 60 r / min. Mix for 1 minute, then add zinc oxide, stearic acid, and antioxidant and mix for 2 minutes. Then add 18.9 parts by weight of lignin powder, discharge the mixture, and obtain the compound. Set the temperature of the three zones of the internal mixer to 150℃, then put the rubber compound back into the internal mixer, let it stay for 1 minute, and then take it out. Sheet the rubber compound on a two-roll mill with cooling water and lower the temperature to room temperature. Then add the accelerator and sulfur in sequence on the two-roll mill, cut it with the left and right cutters 5 times, make three triangular wraps, and roll it 3 times to obtain the nano-composite rubber material.

[0090] Comparative Example 4 Step 1: Take 916g of natural rubber latex with a dry rubber content of 60% and put it into a 5L reactor. Add 916g of water to dilute it to a dry rubber content of 30%. Add 36.6g of stabilizer OP-10. Set the stirring speed to 150r / min and stir for 30 minutes. Then add 237g of formic acid with a mass concentration of 85% and 904g of hydrogen peroxide. React in a closed container in a 40℃ water bath for 6 hours. Stop the reaction and add ammonia dropwise until the pH reaches 6.5. Epoxidized natural rubber latex with a dry rubber content of 18.3% and an epoxy degree of 30 is obtained.

[0091] Step 2: Weigh 687g of the epoxidized natural rubber latex prepared in Step 1, weigh 1L of anhydrous ethanol and pour it into the latex to cause the latex to flocculate and obtain a solid rubber block. Cut the rubber block into small pieces, wash it repeatedly with deionized water, and dry it in a 60℃ oven until constant weight to obtain the dry epoxidized natural rubber.

[0092] Step 3: Weigh 125.7 parts by weight of the epoxidized natural rubber dry rubber prepared in Step 2, 6.28 parts by weight of zinc oxide, 2.51 parts by weight of stearic acid, 2.51 parts by weight of antioxidant 4020, 1.25 parts by weight of accelerator DM, 2.51 parts by weight of accelerator CZ, and 2.51 parts by weight of sulfur. Place the epoxidized natural rubber dry rubber into a Hacker internal mixer. Set the mixer temperature to 60℃ and the speed to 60 r / min. Mix for 1 minute, then add zinc oxide, stearic acid, and antioxidant and mix for 2 minutes. Then add 25.2 parts by weight of lignin powder, discharge the mixture, and obtain the compound. Set the temperature of the three zones of the internal mixer to 150℃, then put the rubber compound back into the internal mixer, let it stay for 1 minute, and then take it out. Sheet the rubber compound on a two-roll mill with cooling water and lower the temperature to room temperature. Then add the accelerator and sulfur in sequence on the two-roll mill, cut it with the left and right cutters 5 times, make three triangular wraps, and roll it 3 times to obtain the nano-composite rubber material.

[0093] Comparative Example 5 Step 1: Take 916g of natural rubber latex with a dry rubber content of 60% and put it into a 5L reactor. Add water to dilute it to a dry rubber content of 18.3%. Add 36.6g of stabilizer OP-10. Set the stirring speed of the impeller to 150r / min and stir for 30 minutes to obtain natural rubber latex with a dry rubber content of 18.3%.

[0094] Step 2: Weigh 100g of enzymatically hydrolyzed lignin solid powder, add 900g of water, stir and mix, then pour into a colloid mill. Grind at 70Hz and 25℃ for 10 minutes, then turn off the colloid mill and collect the slurry from the bottom outlet to obtain lignin slurry.

[0095] Step 3: Weigh 687g of the natural rubber latex prepared in Step 1 and 63g of the lignin slurry prepared in Step 2 and mix them to obtain a mixture. Stir the mixture at 40℃ and 200 rpm for 30 minutes. No flocculation occurred.

[0096] Micromorphology Transmission electron microscopy (TEM) images of the nanocomposite rubber materials prepared in Examples 1-4 and Comparative Examples 1-4 are shown below. Figure 1 As shown.

[0097] Figure 1 middle: W5 is a transmission electron microscope image of Example 1. W10 is a transmission electron microscope image from Example 2. W15 is a transmission electron microscope image of Example 3. W20 is a transmission electron microscope image from Example 4. D5 is a transmission electron microscope image of Comparative Example 1. D10 is a transmission electron microscope image of Comparative Example 2. D15 is a transmission electron microscope image of Comparative Example 3. D20 is a transmission electron microscope image of Comparative Example 4.

[0098] from Figure 1 As can be seen, compared with Comparative Examples 1-4, the lignin in the nanocomposite rubber materials prepared in Examples 1-4 is more uniformly dispersed. Moreover, in the nanocomposite rubber materials prepared in Comparative Examples 1-4, obvious agglomeration phenomenon appeared with the increase of lignin addition.

[0099] Performance testing The vulcanization performance and mechanical properties of the nanocomposite rubber materials prepared in Examples 1-4 and Comparative Examples 1-4 were tested respectively.

[0100] The vulcanization performance was tested using a rotorless vulcanizer, and the vulcanizate of the rubber nanocomposite material was prepared using a flat vulcanizing machine. The compound was cut into approximately 6 g discs, lined with cellophane on both sides, and placed in the center of the rotorless vulcanizer. The vulcanization performance of the rubber was tested at a temperature of 150℃ for 40 minutes. After the test, the vulcanization curve and the positive vulcanization times (T10, T20, T30) of the compound were obtained. 90 The vulcanization characteristic parameters, including those mentioned above, are shown in Table 1. In Table 1, MLdN.m represents the minimum torque of the rubber during vulcanization, MHdN.m represents the maximum torque of the rubber during vulcanization, and ΔMdN.m represents the difference between the maximum and minimum torques; ΔMdN.m is used to characterize the degree of crosslinking of the material.

[0101] Mechanical properties were tested using an electronic universal testing machine. First, the vulcanized sheets were cut into standard samples. Five dumbbell-shaped specimens were used for tensile property testing, following the method specified in GB / T 528-2009. The test results are shown in Table 2.

[0102] Table 1

[0103] The difference between Examples 1-4 and Comparative Examples 1-4 is that the masterbatch of Examples 1-4 was prepared by a wet process, and the flocculation process was completed by the self-flocculation of lignin. The masterbatch of Comparative Examples 1-4 was prepared by a traditional dry process, in which lignin powder was directly added to the rubber matrix.

[0104] The data in Table 1 shows: Compared with Comparative Examples 1-4, the scorch time (T) of Examples 1-4 was significantly shorter. 10 Shorten the positive vulcanization time (T) 90 The wet process of this invention allows lignin to be more evenly dispersed in the rubber matrix, promoting the construction of the cross-linking system and thus shortening the vulcanization time, compared to the dry process.

[0105] Compared with Comparative Examples 1-4, the ΔM of Examples 1-4 is increased; This indicates that the degree of crosslinking and the crosslinking density of the masterbatch prepared by the wet method are greater than those prepared by the dry method.

[0106] Table 2

[0107] The difference between Examples 1-4 and Comparative Examples 1-4 is that the masterbatch of Examples 1-4 was prepared by a wet process, and the flocculation process was completed by the self-flocculation of lignin. The masterbatch of Comparative Examples 1-4 was prepared by a traditional dry process, in which lignin powder was directly added to the rubber matrix.

[0108] The data in Table 2 shows: In Examples 1-4, the elongation at break and tensile strength of the materials both increased with increasing lignin content; in Comparative Examples 1-4, the elongation at break and tensile strength of the materials both decreased with increasing lignin content. This indicates that in the dry process, increased lignin content leads to increased agglomeration, which negatively impacts performance. Therefore, the dry process cannot accommodate large amounts of lignin. Compared to the dry process, the lignin masterbatch prepared by the wet process can accommodate more lignin, improving material performance while avoiding agglomeration.

[0109] Compared to Comparative Examples 1-4, the elongation at break and tensile strength of Examples 1-4 were improved. This demonstrates that, compared to the dry process, the wet process of the present invention can improve the elongation at break and tensile strength of rubber materials.

Claims

1. A method for preparing a lignin / rubber nanocomposite masterbatch, comprising: (1) Rubber latex is subjected to epoxidation treatment to obtain epoxidized rubber latex; (2) Grind lignin with water to obtain lignin slurry; (3) Mix and stir the epoxidized rubber latex with the lignin slurry, and collect the solids; Preferably, the preparation method further includes: (4) After the collected solids are cut into pieces, they are washed with water and then dried to constant weight.

2. The preparation method according to claim 1, characterized in that, In step (1), The rubber latex is natural rubber latex; or / and, The solid content of the rubber latex is 20-40%; or / and, The epoxy degree of the epoxidized rubber latex is 10-60%, preferably 15-50%; or / and, The epoxidation treatment includes: adding a stabilizer to the rubber latex, stirring until the latex is stable, adding an epoxidizing agent and stirring to react, and adjusting the pH of the system to 6-7 after the reaction stops to obtain the epoxidized rubber latex.

3. The preparation method according to claim 2, characterized in that, The stabilizer is selected from at least one of nonionic emulsifiers and cationic emulsifiers; or / and, The epoxidizing agent is selected from an epoxidation system composed of formic acid and hydrogen peroxide, an epoxidation system composed of acetic acid and hydrogen peroxide; or / and, The stirring reaction conditions are: water bath temperature 35~50℃, stirring speed 140~200 r / min; or / and, Adjust the pH of the system with ammonia.

4. The preparation method according to claim 1, characterized in that, In step (2), The lignin is enzymatically hydrolyzed lignin; or / and, The mass ratio of lignin to water is 5~15:100; or / and, Grinding was performed using a colloid mill; or / and, The grinding frequency is 40~70Hz; or / and, The grinding time is 20-60 minutes; or / and, The grinding temperature is 20~40℃.

5. The preparation method according to claim 1, characterized in that, In step (3), The mass ratio of dry rubber to lignin in lignin slurry in epoxidized rubber latex is 100:1~40; or / and, The lignin slurry is poured into the epoxidized rubber latex in one go; or / and, The stirring speed is 150~250 r / min; or / and, The mixing and stirring temperature is 25~45℃.

6. The preparation method according to claim 1, characterized in that, In step (4), the drying temperature is 50~70℃.

7. A lignin / rubber nanocomposite masterbatch, prepared by the preparation method described in any one of claims 1-6.

8. An epoxidized nanocomposite rubber material, prepared by mixing raw materials including lignin / rubber nanocomposite masterbatch prepared by any one of the preparation methods described in claims 1-6 or lignin / rubber nanocomposite masterbatch as described in claim 7.

9. The epoxidized nanocomposite rubber material as described in claim 8, characterized in that, It is prepared by mixing raw materials comprising the following components; the components and their parts by weight are as follows: 100 parts by weight of lignin / rubber nanocomposite masterbatch; The antioxidant is 1 to 4 parts by weight, preferably 2 to 3 parts by weight; Zinc oxide 1 to 10 parts by weight, preferably 3 to 7 parts by weight; Stearic acid 1-4 parts by weight, preferably 2-3 parts by weight; The accelerator is 1 to 4 parts by weight, preferably 2 to 3 parts by weight; The vulcanizing agent is 0.5 to 5 parts by weight, preferably 1 to 4 parts by weight.

10. A method for preparing the epoxidized nanocomposite rubber material as described in claim 8 or 9, comprising: The lignin / rubber nanocomposite masterbatch is heat-treated using an internal mixer to obtain the heat-treated masterbatch. The heat-treated masterbatch is then mixed with other optional raw materials.

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