A tire sidewall rubber composition containing modified lignin and a mixing method thereof

Abstract

The application relates to the technical field of tire rubber manufacturing, and discloses a tire side rubber composition containing modified lignin and a mixing method thereof, wherein modified lignin is added in the rubber composition. The modified lignin is water-soluble lignin obtained by modifying lignin by grafting citric acid groups. The lignin is modified by citric acid, citric acid groups are grafted on the lignin groups under the catalysis of sodium hypophosphite to enhance the hydrophilicity of the lignin, and the dispersibility of the lignin in rubber is effectively improved by combining with wet mixing, and the mixing condition after the lignin replaces carbon black is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tire rubber manufacturing, in particular to a tire side rubber composition containing modified lignin and a mixing method thereof. BACKGROUND

[0002] Due to the non-renewable nature of fossil fuel resources and environmental pollution, greenhouse gas emissions and other problems caused during use, countries around the world are seeking new energy as a sustainable development outlet. Therefore, as a widely available renewable energy source, the development and utilization of biomass-based materials has also received widespread attention.

[0003] Lignin is one of the main components of higher plants. Using lignin as a filler to fill rubber not only can enhance rubber, replace carbon black, and break away from dependence on petroleum, but also has lower production costs, while imparting excellent flame retardancy, UV resistance, and oxidation resistance to rubber, making the application and research of lignin in rubber very cutting-edge. However, due to the complexity and heterogeneity of the chemical and physical structures of lignin, it is difficult to truly form nanoscale dispersion in the rubber matrix to achieve the performance of carbon black reinforced rubber, and sometimes it can even worsen the performance of the material. Therefore, it is still a long way to go for lignin to completely replace carbon black and be applied to most rubber, especially non-polar rubber. In view of this, how to make lignin into a reinforcing filler like traditional fillers and apply it to rubber will be a very promising direction.

[0004] Chinese invention patent (publication number: CN117757159A, publication date: 2024-03-26) discloses a tire rubber composition, which is prepared by mixing raw materials including the following components by weight based on 100 parts of raw rubber: raw rubber 100 parts, reinforcing filler 45-80 parts; and appropriate amount of activator, antioxidant and vulcanizing agent; the raw rubber includes trans-isoprene rubber 5-15 parts, and the reinforcing filler includes lignin modified white carbon black 5-20 parts, the lignin modified white carbon black is prepared by reacting raw materials including the following components by weight based on 100 parts of white carbon black: white carbon black 100 parts, acetylated lignin 10-60 parts. The composition solves the problem of increased heat generation after adding trans-isoprene rubber by using acetylated lignin modified white carbon black, and the prepared mine tire has good tear resistance, puncture resistance, cutting resistance and chipping resistance, while reducing the heat generation of the rubber compound.

[0005] A modified lignin and its preparation method and application in rubber composite are disclosed in Chinese invention patent (publication number: CN112831059B, publication date: 2021-11-26). The modified lignin is obtained by reacting lignin and alkyne compound in an organic solvent. The invention has the following advantages: (1) the acyl chloride functional group in the structure of the alkyne modification reagent is easy to react with the alcohol and phenolic hydroxyl groups in the lignin molecule to form a modified lignin grafted with unsaturated alkyne functional groups. (2) The alkyne modification reduces the content of hydroxyl groups in the lignin molecule, reduces the molecular polarity, helps to inhibit the self-aggregation tendency of lignin caused by hydrogen bonds, and is beneficial to grinding to obtain lignin powder with low particle size, improving the compatibility and affinity of lignin and non-polar natural rubber, and promoting the dispersion of lignin in the natural rubber matrix.

[0006] In addition, the shearing and crushing action of open mill and internal mixer is used to mix the compounding agents and rubber compounds in traditional dry mixing method. This mixing method not only has problems such as dust pollution, high energy consumption and high heat generation, but also has poor dispersion of fillers such as lignin and white carbon black which are easy to self-aggregate and difficult to disperse. The wet mixing method has more obvious advantages. SUMMARY

[0007] The present application provides a tire side rubber composition containing modified lignin and a mixing method thereof, which can effectively replace carbon black to prepare tire side rubber composition and improve the dispersion of lignin in rubber.

[0008] In order to achieve the above purpose, the following technical solutions are adopted in the present application:

[0009] A tire side rubber composition containing modified lignin, the rubber composition is prepared by wet mixing, and the raw material mixing is prepared by the following components based on 100 parts by weight of raw rubber:

[0010] 25.0-55.0 parts of natural rubber,

[0011] 45.0-75.0 parts of butadiene rubber,

[0012] 25.0-55.0 parts of carbon black,

[0013] 5.0-15.0 parts of modified lignin,

[0014] 1.0-10.0 parts of rubber processing oil,

[0015] 1.0-4.0 parts of tackifying resin,

[0016] 1.0-4.0 parts of paraffin wax;

[0017] The modified lignin is water-soluble lignin obtained by grafting citric acid to lignin.

[0018] Preferably, the rubber composition is prepared by raw material mixing comprising the following components per 100 parts by weight of raw rubber:

[0019] natural rubber 35.0-45.0 parts,

[0020] butadiene rubber 55.0-65.0 parts,

[0021] carbon black 35.0-45.0 parts,

[0022] modified lignin 8.0-12.0 parts,

[0023] rubber processing oil 1.0-3.0 parts,

[0024] antioxidant 1.0-6.0 parts,

[0025] tackifying resin 2.5-3.5 parts,

[0026] paraffin wax 1.5-2.5 parts,

[0027] active agent 1.0-5.0 parts,

[0028] accelerator 0.5-3.0 parts,

[0029] vulcanizing agent 1.0-4.0 parts.

[0030] Preferably, the modified lignin is lignin grafted with citric acid to enhance its hydrophilicity under the catalysis of sodium hypophosphite.

[0031] Preferably, the preparation method of the modified lignin comprises the following steps:

[0032] 1) At room temperature, citric acid is dissolved in water to prepare a citric acid solution, sodium hypophosphite is added, and the solution is stirred to mix uniformly; the freeze-dried lignin nanoparticle powder is added, and stirring is continued for 0.5-1.5 hours to allow the lignin nanoparticles to fully contact with the citric acid aqueous solution to obtain a suspension;

[0033] 2) The suspension is placed in a vacuum drying oven and vacuumized, and then left to stand at room temperature for 11-13 hours;

[0034] 3) The suspension is placed in an air drying oven to remove excess water, and then the remaining material is placed in a 125-135℃ oven for 3.5-4.5 hours, and the colloidal lignin nanoparticles are taken out after the reaction is completed;

[0035] 4) dispersing the colloidal lignin nanoparticles into water again and purifying the modified lignin nanoparticles by centrifugation, placing the precipitate obtained after centrifugation into deionized water for dialysis, diluting the modified lignin nanoparticle suspension to below 1%, and uniformly dispersing the modified lignin nanoparticles in water after ultrasonic treatment;

[0036] 5) freeze-drying to obtain the modified lignin.

[0037] Preferably, the concentration of the citric acid solution is 4-6% (w / w);

[0038] Preferably, the concentration of the sodium hypophosphite is 1% (w / w);

[0039] Preferably, the vacuum degree of the vacuum drying oven is 0.5-0.7 Bar, and the placement time of the suspension is 1.5-2.5 hours;

[0040] Preferably, the temperature of the air drying oven is 55-65℃, and the placement time of the suspension is 46-50 hours;

[0041] Preferably, the temperature of the freeze-drying is -45℃ to -55℃, and the vacuum degree is 0.11-0.13 mBar.

[0042] Preferably, the wet mixing process comprises the following steps: mixing carbon black and modified lignin with water to obtain dispersion A, mixing rubber with deionized water to obtain dispersion B, mixing dispersion A with dispersion B, then adding an aqueous CaCl2 solution to make the suspension flocculate to obtain flocculation gel, and washing and drying the flocculation gel to obtain masterbatch, and placing the masterbatch and the compounding agent into an open mill to mix to obtain wet mixed rubber.

[0043] Preferably, the particle size of the carbon black is 30-70 nm.

[0044] Preferably, the active agent uses zinc oxide and stearic acid, the amount of zinc oxide is 1.0-4.0 parts, and the amount of stearic acid is 1.0-3.0 parts.

[0045] Preferably, the accelerator uses accelerator CZ and / or accelerator NS, the amount of accelerator CZ is 0.1-2.0 parts, and the amount of accelerator NS is 0.1-0.65 parts.

[0046] Further, the application also discloses a mixing method of the tire side rubber composition containing modified lignin, which uses wet mixing and comprises the following steps:

[0047] 1) preparing masterbatch

[0048] a. placing carbon black, modified lignin and water into a colloid mill for grinding to obtain a carbon black water dispersion;

[0049] b. Add rubber into deionized water to adjust the solid content to 10%, then transfer into beaker, and stir uniformly with electric mixer, the stirring speed is 450-550 rpm, and the stirring time is 8-12 min;

[0050] c. Add carbon black water dispersion into the uniformly mixed rubber, continue to stir for 25-35 min, and add 5% CaCl2 aqueous solution into the mixture to make it flocculate;

[0051] d. Wash the flocculated gel in deionized water for 4-6 times, then dry in vacuum oven at 55-65℃ for 22-26 h to obtain masterbatch;

[0052] 2) Mixing

[0053] a. Warm up the hot roll mill to 75-90℃, add the masterbatch into the mill to plasticize for 0.5-1.5 min to wrap the roll;

[0054] b. Add rubber process oil, tackifying resin, paraffin, zinc oxide, stearic acid, antioxidant, accelerator and vulcanizing agent into the mill in sequence, cut the rubber continuously to make the compounding agent uniformly dispersed in the rubber, then adjust the roll gap to 0.15-0.25 mm, make triangle bag and roll in sequence, repeat for three times, then adjust the roll gap to 1.5-2.0 mm, and get the sheet, to obtain wet mixing rubber.

[0055] The present application has the following advantages: the present application uses citric acid to modify lignin, grafts citric acid on lignin group to enhance its hydrophilicity, and combines with wet mixing, effectively improves the dispersibility of lignin in rubber, reduces the rolling resistance of rubber composition, and the addition of lignin can enhance the rubber network strength and improve the tensile properties of rubber.

[0056] In the rubber composition of the present application, in addition to the above components, different additives can be mixed, such as other fillers commonly used in tires and other rubber compositions, vulcanizing agents, vulcanization accelerators, different types of oils, antioxidants, plasticizers, etc. These additives are mixed in a common method to obtain a rubber composition that can be used for vulcanization. The amount of these additives can also be the amount of common mixing, provided that it does not adversely affect the purpose of the present application. DETAILED DESCRIPTION

[0057] The technical solutions in the examples of the present application will be described below in a clear and complete manner. Obviously, the described examples are only a part of the examples of the present application, rather than all the examples. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0058] The formula of the examples and comparative examples is shown in Table 1 (parts by weight).

[0059] Table 1

[0060] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Example 1 Example 2 Example 3 Natural Rubber*1 40 40 40 40 40 40 40 40 Butadiene Rubber*2 30 30 30 30 30 30 30 Butadiene Rubber*3 60 30 30 30 30 30 30 30 Carbon Black*4 5 Carbon Black*5 35 35 48 35 35 35 35 35 Carbon Black*6 5 5 5 5 5 5 5 Modified Lignin 20 5 10 15 Lignin*7 10 Rubber Process Oil*8 2 2 2 2 2 2 2 2 Stearic Acid*9 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Antioxidant*10 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Antioxidant*11 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Zinc Oxide*12 3 3 3 3 3 3 3 3 Paraffin Wax*13 2 2 2 2 2 2 2 2 Tackifying Resin*14 3 3 3 3 3 3 3 3 Accelerator*15 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 Accelerator*16 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 Oil-Extended Sulfur*17 2 2 2 2 2 2 2 2

[0061] Table 1 footnote

[0062] *1: Natural rubber (solid content 60%), product of Haigou Group;

[0063] *2: BR1250H, product of ZEON Corporation, Japan;

[0064] *3: BR9000, product of Zhejiang Chuanhua Corporation;

[0065] *4: N330, product of Cabot Chemical Corporation;

[0066] *5: N550, product of Cabot Chemical Corporation;

[0067] *6: N660, product of Cabot Chemical Corporation;

[0068] *7: Lignin HS-L101, product of Hangshi Technology Development Co., Ltd.;

[0069] *8: V500, product of Ningbo Hansheng Co., Ltd.;

[0070] *9: Stearic acid SA1801, product of Yihai Kerry;

[0071] *10: Antioxidant RD, product of Sinopec Nanjing Chemical Industry Co., Ltd.;

[0072] *11: Antioxidant 4020, product of Sinopec Nanjing Chemical Industry Co., Ltd.;

[0073] *12: Zinc oxide, product of Qingdao Haiyan Chemical Co., Ltd.;

[0074] *13: Microcrystalline wax H3236, product of Yanggu Huatai;

[0075] *14: Tackifying resin SL-1801, product of Huachi Chemical;

[0076] *15: Accelerator CZ, product of Shandong Shangshun Chemical Co., Ltd.;

[0077] *16: Accelerator NS, product of Shandong Shangshun Chemical Co., Ltd.;

[0078] *17: Oil-extended sulfur powder, product of Wuxi Huasheng Rubber New Material Science and Technology Co., Ltd.

[0079] Comparative Example 1 used dry mixing, and the remaining comparative examples and examples used wet mixing.

[0080] The specific steps of dry mixing are as follows:

[0081] 1) One-stage mixing: mixing is performed using an internal mixer; rubber is added, and the ram is kept down for 60 seconds; the ram is raised, carbon black, activator, and antioxidant are added, and the ram is kept down for 60 seconds; the ram is raised, rubber process oil, tackifying resin, and paraffin are added, and the ram is kept down for 90 seconds; the ram is raised, and the machine is cleaned;

[0082] 2) Two-stage mixing: mixing is performed using an open mill; the rubber is discharged into the open mill, the double-roller open mill is adjusted to a roll gap of 1.0 mm, and the rubber from the internal mixer is wrapped around the roll; the accelerator and vulcanizing agent are added in sequence, and each is cut three times with the left and right knives; the rubber is wrapped around the roll at a roll gap of 0.20 mm and is passed through the triangle pack five times; the roll gap is adjusted to 2.0 mm, and the rubber is discharged.

[0083] The specific steps of wet mixing are as follows:

[0084] 1) Preparation of masterbatch

[0085] a. Carbon black, modified lignin, and 500 mL of water were placed in a colloid mill and ground to obtain a carbon black water dispersion;

[0086] b. The rubber was added to deionized water to adjust the solid content to 10%, and then transferred to a beaker, and stirred uniformly with an electric stirrer at a stirring speed of 500 rpm for 10 min;

[0087] c. The carbon black water dispersion was added to the uniformly mixed rubber, and stirring was continued for 30 min, and 650 mL of a 5.0% CaCl2 aqueous solution was added dropwise to the mixture to cause flocculation;

[0088] d. The flocculated rubber was washed five times in deionized water, and then dried in a vacuum oven at 60°C for 24 h to obtain a masterbatch;

[0089] 2) Mixing

[0090] a. The hot roll open mill was heated to 80°C, and the masterbatch was added to the open mill and plasticized for 1.0 min to wrap the roll;

[0091] b. Rubber process oil, tackifying resin, paraffin, zinc oxide, stearic acid, antioxidant, accelerator, and vulcanizing agent were added in sequence, and the rubber was continuously cut to uniformly disperse the ingredients in the rubber, then the roll gap was adjusted to 0.20 mm, and the triangle pack and rolling were repeated three times, then the roll gap was adjusted to 2.0 mm, and the rubber was discharged to obtain a wet-mixed rubber.

[0092] The rubber compositions obtained in the examples and comparative examples were tested.

[0093] Vulcanization properties: The vulcanization curve and vulcanization property parameters at 143℃ were determined by using the UR-2030 rotorless vulcanization instrument of the Ucar Company according to the GB / T 9869-1997 standard, and the 1° swing angle.

[0094] Filler dispersion: The rubber processing analyzer RPA2000 of the American Alpha Company was used to test the blended rubber, 5-6 g of the mixed rubber was placed in the mold cavity, and the test was carried out at 60℃, and the influence of different mixing methods and different blending ratios on the filler network of the blended rubber was analyzed and studied.

[0095] Tensile properties: The tensile strength and tear strength of the composite material were carried out according to the GB / T 528-2009 and GB / T 529-2008 standards, the tensile sample was dumbbell-shaped, and the tear sample was right-angle-shaped, and the U-CAN UT-2060 electronic tensile testing machine was used to determine the rate of 500mm / min.

[0096] Dynamic mechanical analysis (DMA) was carried out on the DMA 242D dynamic mechanical analyzer produced by the German Nanjing Company in the tensile mode. The test conditions were: 12 Hz, 0.5% strain, the temperature range was -100-100℃, and the heating rate was 3℃ / min.

[0097] The test data is shown in Table 2.

[0098] Table 2

[0099] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Example 1 Example 2 Example 3 T90(min) 100 95 93 92 90 93 91 90 Payne Effect(%) 100 32 95 90 32 30 26 31 TB(MPa) 100 109 121 111 93 123 128 116 EB(%) 100 109 86 106 112 116 128 111 Tan delta 60°C 100 83 96 86 78 72 73 76

[0100] Analyzing Table 2, Example 2 is the best embodiment, and the comprehensive performance is the best. It can be seen from Comparative Examples 1 and 2 that the filler dispersion of the wet mixing is obviously higher, the tensile properties of the rubber composition are better, and the rolling resistance is also relatively lower. Comparative Example 2 and Example 2 add the same amount of carbon black, and Comparative Example 3 adds sufficient carbon black, it can be seen that the filler dispersion of Example 2 is obviously improved, the network strength of the rubber is also obviously improved, the tensile properties are obviously enhanced, and the rolling resistance is also relatively lower. Lignin can effectively replace part of the carbon black. It can be seen from Comparative Example 4 and Example 2 that the modification of lignin can effectively improve the hydrophilicity to better adapt to the wet mixing, and effectively improve the dispersion of lignin in rubber. It can be seen from Comparative Example 5 and Example that the addition amount of modified lignin should not be too much.

[0101] The foregoing is a description of the embodiments of the present application. The above description of disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A sidewall rubber composition containing modified lignin, characterized in that: The rubber composition is prepared by wet mixing, and the raw materials comprising the following components are mixed based on 100 parts by weight of raw rubber: 25.0-55.0 parts of natural rubber, 45.0-75.0 parts of butadiene rubber, 25.0-55.0 parts of carbon black, 5.0-15.0 parts of modified lignin, 1.0-10.0 parts of rubber processing oil, 1.0-4.0 parts of tackifying resin, 1.0-4.0 parts of paraffin wax; The modified lignin is water-soluble lignin obtained by grafting citric acid onto lignin; The wet mixing method includes the following steps: mixing carbon black, modified lignin and water to obtain dispersion A, mixing rubber and deionized water to obtain dispersion B, mixing dispersion A and dispersion B, then adding a CaCl2 aqueous solution to flocculate them to obtain a flocculent gel, washing and drying the flocculent gel to obtain a masterbatch, and placing the masterbatch and compounding ingredients in an open mill and mixing to obtain a wet mixed rubber.

2. The sidewall rubber composition containing modified lignin according to claim 1, characterized in that: The rubber composition is prepared by mixing the following raw materials based on 100 parts by weight of raw rubber: 35.0-45.0 parts of natural rubber, 55.0-65.0 parts of butadiene rubber, 35.0-45.0 parts of carbon black, 8.0-12.0 parts of modified lignin, 1.0-3.0 parts of rubber operating oil, 1.0-6.0 parts of antioxidant, 2.5-3.5 parts of tackifying resin, 1.5-2.5 parts paraffin wax, 1.0-5.0 parts of active agent, 0.5-3.0 parts of accelerator, 1.0-4.0 parts of vulcanizing agent; The active agents are zinc oxide and stearic acid.

3. A sidewall rubber composition containing modified lignin according to claim 1 or 2, characterized in that: The modified lignin is prepared by grafting citric acid onto the lignin under the catalysis of sodium hypophosphite to enhance the hydrophilicity of the lignin.

4. A sidewall rubber composition containing modified lignin according to claim 1 or 2, characterized in that: The preparation method of modified lignin comprises the following steps: 1) At room temperature, dissolve citric acid in water to prepare a citric acid solution, add sodium hypophosphite, and stir to mix the solution evenly; add freeze-dried lignin nanoparticle powder, and continue stirring for 0.5-1.5 hours to allow the lignin nanoparticles to fully contact the citric acid aqueous solution to obtain a suspension; 2) Place the suspension in a vacuum drying oven and let it stand at room temperature for 11-13 hours; 3) The suspension is placed in an air drying oven to remove excess water, and the remainder is then placed at 125-135°C for 3.5-4.5 hours. After the reaction is completed, the colloidal lignin nanoparticles are taken out; 4) The colloidal lignin nanoparticles are redispersed in water and the modified lignin nanoparticles are purified by centrifugation. The precipitate obtained after centrifugation is dialyzed in deionized water. The modified lignin nanoparticle suspension is diluted to less than 1% and ultrasonically treated to uniformly disperse it in water. 5) Freeze drying to obtain modified lignin.

5. The sidewall rubber composition containing modified lignin according to claim 4, characterized in that: The mass percentage concentration of the citric acid solution is 4-6%; And / or, the mass percentage concentration of the sodium hypophosphite is 0.8-2.0%; And / or, the vacuum degree of the vacuum drying oven is 0.5-0.7 Bar, and the suspension is placed for 1.5-2.5 hours; and / or, the air drying oven temperature is 55-65° C., and the suspension is placed for 46-50 hours; And / or, the freeze-drying temperature is -45°C to -55°C, and the vacuum degree is 0.11-0.13 mBar.

6. A sidewall rubber composition containing modified lignin according to claim 1 or 2, characterized in that: The carbon black particle size is 30-70 nm.

7. The sidewall rubber composition containing modified lignin according to claim 2, characterized in that: The accelerator is accelerator CZ and / or accelerator NS.

8. The mixing method of a sidewall rubber composition containing modified lignin according to any one of claims 2 to 7, characterized in that: The wet mixing method includes the following steps: 1) Preparation of masterbatch a. Grind carbon black, modified lignin and water in a colloid mill to obtain a carbon black aqueous dispersion; b. Add the rubber to deionized water and adjust the solid content to 10%. Then transfer it to a beaker and stir it evenly with an electric stirrer at a speed of 450-550 rpm for 8-12 minutes. c. Add the carbon black aqueous dispersion to the mixed rubber and continue stirring for 25-35 minutes. Add 5% by mass fraction of CaCl2 aqueous solution to the mixture to make it flocculate; d. Wash the flocculent gel in deionized water for 4-6 times, and then dry it in a vacuum oven at 55-65°C for 22-26 hours to obtain a masterbatch; 2) Mixing a. Heat the hot roller mill to 75-90℃, add the masterbatch into the mill and plasticize for 0.5-1.5 minutes until it wraps around the roller; b. Add rubber operating oil, tackifying resin, paraffin, zinc oxide, stearic acid, antioxidant, accelerator and vulcanizing agent in sequence, tapping the rubber continuously to make the compounding agents evenly dispersed in the rubber, then reduce the roller distance to 0.15-0.25mm, make triangle packages and roll them in sequence, repeat three times, then adjust the roller distance to 1.5-2.0mm, and produce sheets to obtain wet mixed rubber.