Improved composite material for manufacturing rubber products and preparation method thereof

Abstract

The invention relates to an improved composite material for manufacturing a rubber product and a preparation method of the improved composite material, the composite material comprises the following substance components: lignin, rubber and a functional auxiliary agent, and the mass part ratio of the lignin to the rubber to the functional auxiliary agent is (1-280): (98-102): (0-280); the lignin is obtained by alkaline pulping, semi-chemical and semi-mechanical papermaking pulping, semi-chemical papermaking pulping or mechanical papermaking pulping, or obtained by fermenting cellulose in gramineous plants, herbaceous plants, woody plants and vine plants separated by a similar process to prepare bioethanol; the rubber is natural rubber, synthetic rubber or a combination of the natural rubber and the synthetic rubber, a coprecipitate of the composite material is prepared, and the coprecipitate has a microcosmic or sub-microcosmic structure that lignin is wrapped by the rubber. The method has the characteristics of better physical and mechanical properties, wide collection range of applied lignin and lower preparation cost of the lignin.

Description

Technical Field

[0001] This invention relates to an improved composite material for manufacturing rubber products and its preparation method, specifically a composite material with lignin and rubber as the main components and its preparation technology. It belongs to the field of chemical materials and their preparation technology. Background Technology

[0002] In the existing technology, there are two methods for preparing lignin-containing composite materials used to manufacture rubber products: dry blending and wet blending. Dry blending refers to the method of directly blending modified or unmodified lignin with raw rubber in an internal mixer or open mill; wet blending refers to the method of preparing a dispersion of modified or unmodified lignin and then blending it with rubber latex to form an emulsion co-precipitate. However, the following problems exist: (1) The internal microstructure of the coprecipitate obtained by wet blending is a hybrid micro or submicroscopic structure of lignin-encapsulated rubber and rubber-encapsulated lignin, resulting in poor physical and mechanical properties of the composite material prepared in this way. (2) Dry blending often requires modification of the raw material lignin, which results in a longer process route and higher preparation costs. (3) The range of lignin that can be collected is limited.

[0003] For example, the invention patent with patent number 89109494.6, "Method for using lignin as a rubber reinforcing agent," and the invention patent with authorization announcement number CN 101314675 B, "An industrial lignin-reinforced and filled blended elastomer material and its preparation method," are typical dry blending process technologies. Applying lignin to the rubber field can yield excellent physical and mechanical properties; however, the source of lignin raw materials is limited to black liquor obtained from alkaline pulping, and the adopted process route has relatively high energy consumption and cost. The invention patent with authorization announcement number CN 117700844 B, "A fully bio-based high-filled lignin rubber masterbatch and its preparation method and application," reacts lignin, acetic acid, and oleic acid in a catalyst to obtain modified lignin. The obtained modified lignin is then blended with rubber and granulated to obtain lignin rubber masterbatch, which also employs a dry blending process technology.

[0004] The invention with application number 2013102614516, entitled "Industrial Lignin-Filled Polymer Composite Material and Its Preparation Method and Uses," and authorization announcement number CN 102718995 B, entitled "An Industrial Lignin-Reinforced Rubber and Its Preparation Method," is a typical wet blending process. The co-precipitation coagulation method of the invention with application number 2013102614516, entitled "Industrial Lignin-Filled Polymer Composite Material and Its Preparation Method and Uses," involves adding 100 parts by weight of dry rubber, 10-300 parts by weight of oven-dry lignin, and 0-100 parts by weight of oven-dry third component to a solution of hydroxymethylated modified sodium lignin. After stirring evenly, a coagulant is added, causing the hydroxymethylated modified sodium lignin to convert to hydroxymethylated modified lignin while simultaneously co-precipitating with the rubber and third component to form a coprecipitate; the coagulant contains at least one acid. The invention, authorized by announcement number CN 102718995 B and entitled "An Industrial Lignin-Reinforced Rubber and Its Preparation Method," describes a preparation method comprising: 1) preparing lignin, 2) preparing a lignin dispersion, 3) preparing latex, 4) co-precipitation and coagulation, and 5) obtaining industrial lignin-reinforced rubber. The lignin is hydroxymethylated modified lignin. This invention, without reducing the physical and mechanical properties of the rubber compound, combines the drying process of lignin and rubber production, reducing the power consumption of rubber compounding. The co-precipitation and coagulation method involves adding the prepared lignin dispersion or multi-component lignin dispersion to latex or a latex mixture, stirring evenly, and then adding a coagulant. This allows the lignin, inorganic fillers, and rubber in the lignin dispersion or multi-component lignin dispersion to co-precipitate, or the lignin, inorganic fillers, rubber, plasticizer, and processing oil to co-precipitate, forming a coprecipitate.

[0005] Another technical solution for wet blending, after purifying the raw material lignin, is mentioned in Cheng Kai et al., "The Influence of Biochemical Lignin on the Properties of Natural Rubber Composites [J]. Rubber Industry, 2018, 65(885-889]". This involves first dissolving and diluting solid biochemical lignin with a certain concentration of sodium hydroxide solution to 500 mL, then adding the biochemical lignin solution to a certain amount of natural latex to form a preliminary mixture, followed by mechanical stirring, acid precipitation, water removal, and drying to obtain a co-precipitated rubber of natural rubber / biochemical lignin. The invention patent "Wheel Tire" with authorization announcement number CN 108430797 B uses lignin with a phenolic group concentration of 2.5-6 mmol / g and a number-average molecular weight Mn of 1000-10000 g / mol. The specification lists SodaGrass lignin, Softwood Kraft lignin, Hardwood Kraft lignin, Wheat Straw lignin, and Rice lignin. Five types of lignin from rice husk are used. The lignin is solubilized in an alkaline solution before being added to the latex of natural rubber. The solid content of the natural rubber latex is preferably 30-60% by weight. The lignin is slowly added to the latex over 5-15 minutes at room temperature with stirring. The resulting mixture is stirred at room temperature for 1-2 hours. Co-precipitation (coagulation) is then achieved by adding an acid solution to the mixture. The invention patents "Tire for Vehicle Wheels" with application number 2022800765542 and "Tire for Vehicle Wheels" with application number 2022800765631 employ the same or similar technical solutions.

[0006] Other wet blending techniques used after modifying lignin include: Patent CN115746332B, "A Lignin-Based Core-Shell Hybrid Material and Its Preparation Method and Its Application in Rubber," which involves adding lignin, an aminosilane coupling agent, and aldehyde compounds to an organic solvent to prepare a lignin-based core-shell hybrid material, followed by emulsion compounding to prepare a lignin / rubber composite material. Patent CN115521513A, "A Flexible Sensor Device Based on Laser Direct Writing Lignin / Rubber Composite Material and Its Preparation Method," uses lignin (sodium lignin sulfonate, calcium lignin sulfonate, sulfonated lignin, alkali lignin, or enzymatically hydrolyzed lignin) or modified lignin (carboxylated lignin, hydroxymethylated lignin, aminated lignin, or phenolic lignin). ① The lignin or modified lignin is dissolved in water with pH 7-12 and added to the rubber along with a carbonizing agent. ① Prepare a composite emulsion from the emulsion; ② Demulsify the composite emulsion obtained in step ① with hydrochloric acid or calcium chloride, filter and wash the demulsified composite or dry it in a forced-air dryer at 60-100℃ to obtain an unvulcanized composite; or directly dry the composite emulsion in a forced-air dryer at 60-100℃ to obtain an unvulcanized composite; ③ Mix the unvulcanized composite obtained in step ② with a vulcanizing agent and an accelerator in a two-roll mill, and then mold it at 120℃-160℃ to obtain a lignin / rubber composite elastic base film.

[0007] Another wet blending technology solution is the invention patent application "Tire for Vehicle Wheels" with application number 2021800785842. The lignin is selected from softwood sulfate lignin, hardwood sulfate lignin, soda grass lignin, wheat straw lignin, rice husk lignin, lignin obtained by biorefining process, and organic solvent lignin. A surfactant is added and the crude lignin suspension is wet-milled by a grinding device to obtain a first suspension with a median diameter D50 of 2-10 micrometers of lignin particles. After mixing with latex, a second suspension is obtained. The second suspension is dried to obtain a pre-dispersion of elastomer diene polymer and lignin with a moisture content ≤5%. The invention patent CN 109536079 B, entitled "A Wet Preparation Process of a Bio-based Multifunctional Constant-Viscosity Adhesive," describes a process where a lignin-rubber solvent is dissolved in water and stirred uniformly at room temperature to form a stable dispersion with a mass concentration of 0.5-5%. A lignin-rubber solvent aqueous dispersion at a mass fraction of 2-50% relative to natural rubber is added to the natural rubber and mixed uniformly. Additives (two or more coupling agents, surface modifiers, surfactants, and antioxidants) at a mass fraction less than 1% of the natural rubber are added, and the mixture is stirred at room temperature for 30-90 minutes. The reacted mixture is then transferred to a drying tank for drying at room temperature for 3-4 days. Afterward, the mixture is creped using a crepe machine, filtered, dehydrated, impurities removed, and washed. It is then fully oxidized in a cool place, i.e., dried, and sun-dried for 1-2 days on the 15th day. Finally, the mixture is granulated, dried, pressed into blocks, and packaged. This invention patent does not specify the exact composition of the lignin-rubber solvent. Summary of the Invention

[0008] One of the objectives of this invention is to address the problem that existing lignin-rubber composite materials have poor physical and mechanical properties due to their hybrid microstructure of lignin-encapsulated rubber and rubber-encapsulated lignin in the co-precipitate. The invention provides an improved composite material for manufacturing rubber products. This composite material contains lignin, and its co-precipitate has a microstructure of rubber-encapsulated lignin, which offers better physical and mechanical properties, a wider range of lignin collection options, and lower lignin preparation costs.

[0009] The second objective of this invention is to provide an improved method for preparing a composite material for manufacturing rubber products. This method addresses the problem that existing lignin-rubber composites often have a hybrid microstructure (either lignin-encapsulated rubber or rubber-encapsulated lignin) in their co-precipitates, resulting in poor physical and mechanical properties. The composite material contains lignin, and its co-precipitate has a microstructure (either rubber-encapsulated lignin) in its microstructure (either lignin-encapsulated rubber). This method offers advantages such as better physical and mechanical properties, a wider range of lignin collection options, and lower lignin preparation costs.

[0010] To achieve one of the objectives of this invention, the following technical solution can be adopted:

[0011] An improved composite material for manufacturing rubber products, characterized by:

[0012] 1) The composite material comprises lignin, rubber and functional additives, and the mass weight ratio of each component is lignin: rubber: functional additives = 1-280: 98-102: 0-280;

[0013] 2) The lignin is obtained by alkaline pulping, semi-chemical and semi-mechanical papermaking pulping, or semi-chemical papermaking pulping or mechanical papermaking pulping, or by fermenting cellulose from grass, herbaceous, woody and vine plants separated by similar processes to prepare bioethanol;

[0014] 3) The rubber is natural rubber, synthetic rubber, or a combination of natural rubber and synthetic rubber.

[0015] 4) The functional additive is an antioxidant, an inorganic or organic filler for rubber, a plasticizer or a softener, or one or more other rubber functional additives besides the aforementioned functional additives;

[0016] 5) Prepare coprecipitates of composite materials with a micro or submicroscopic structure of lignin encapsulated in rubber.

[0017] To achieve the second objective of this invention, the following technical solution can also be adopted:

[0018] Furthermore, the other rubber functional additives include one or more combinations of zinc oxide, stearic acid, sulfur, organic peroxides, and accelerators.

[0019] To achieve the second objective of this invention, the following technical solution can be adopted:

[0020] An improved method for preparing a composite material for manufacturing rubber products, characterized in that the composite material is prepared by co-precipitation of lignin dispersion and rubber latex.

[0021] To achieve the second objective of this invention, the following technical solution can also be adopted:

[0022] Furthermore, when the lignin source is semi-chemical and semi-mechanical papermaking pulping or semi-chemical papermaking pulping or mechanical papermaking pulping, and when cellulose and lignin are separated from grasses, herbs, woody plants, and vines using similar processes, such as obtaining lignin from cellulose fermentation to prepare bioethanol, the lignin is purified and then directly mixed with rubber to produce composite materials, i.e., dry method production of composite materials; or the raw material lignin is modified or unmodified, prepared into a dispersion with a solid content of 5-30% and adjusted, and then mechanically mixed with rubber latex with a solid content of 5-30%, allowed to stand, co-precipitate, and matured to form a micro or submicroscopic structure in which lignin is encapsulated by rubber. After solid-liquid separation, washing, drying, and post-treatment if necessary, a composite material is produced with rubber as the continuous phase and lignin and other antioxidants, inorganic or organic fillers for rubber, plasticizers or softeners, and other rubber functional additives present in the composite material components as the dispersed phase.

[0023] Furthermore, when the weight ratio of lignin to rubber is 1-200:100, the main function of lignin in rubber products is as a reinforcing filler, while also acting as an adhesive enhancer and flame retardant synergist. When the weight ratio of lignin to rubber is 200-280:100, the main function of lignin in rubber products is as a functional material, including acting as an adhesive enhancer between rubber and the skeleton material, or as a flame retardant synergist.

[0024] Furthermore, the antioxidants, inorganic or organic fillers for rubber, plasticizers or softeners, and other rubber functional additives contained in the composite material components are mixed with lignin to form a multi-component dispersion and co-precipitated with rubber latex.

[0025] Furthermore, the modification of raw material lignin refers to phenolization, sulfonation, hydroxymethylation, aminomethylation, halogenation, nitration, alkylation, acetylation, quaternization, grafting modification of lignin, or a combination of two or more modifications, including acetylated hydroxymethylation modification, acetylated aminomethylation modification, hydroxymethylated phenol grafting modification, and acetylated hydroxymethylated phenol grafting modification; the adjustment refers to the use of strong acidic substances such as oxalic acid, sulfuric acid, hydrochloric acid, or nitric acid, and strong alkaline substances such as NaOH or Na2S, to adjust the acidity or alkalinity of the lignin dispersion so that the pH value of the lignin dispersion before mixing with rubber latex is 4.0-7.5.

[0026] Furthermore, the rubber latex is natural rubber latex, synthetic rubber latex, or latex obtained by emulsifying block, granular, or powdered rubber or resin obtained by solution polymerization or bulk polymerization, or a metered physical mixture of natural rubber latex and synthetic rubber latex; before mixing the rubber latex with the lignin dispersion, the viscosity of the system should be adjusted by adjusting its solid content. The suitable solid content of the latex is 5-30% so that the blended system after mixing the latex and the lignin dispersion has a good sedimentation rate and does not separate into layers when standing; after mixing the rubber latex with the lignin dispersion, the standing time at room temperature to 45°C is 5 minutes to 72 hours.

[0027] Furthermore, co-precipitation aims to achieve a microscopic or submicroscopic structure of lignin encapsulated in rubber in the co-precipitate. A measured amount of lignin, along with contingent antioxidants, inorganic or organic fillers for rubber, plasticizers or softeners, and other rubber functional additives, is mixed in dispersion form with a measured amount of rubber latex under stirring. The mixture is then allowed to stand until the latex phase thickens or undergoes other phase changes. The system is then heated to 18-80°C for approximately 0.25-3 hours. If necessary, a measured amount of flocculant is added under stirring. The flocculant can be an acid, salt, or dicyandiamine-formaldehyde condensate. The compound CA, or a mixture of the three, is used to induce phase change and demulsification in the latex system, resulting in the co-precipitation of lignin with a microscopic or submicroscopic structure encapsulated in rubber. The co-precipitate is granular or agglomerated rather than powdery. After the co-precipitation operation, if necessary, the system temperature is maintained at 40-80℃ for 5-60 minutes for further maturation before discharge. Then, subsequent solid-liquid separation, washing, and drying operations are carried out. During washing, hot water at room temperature to 80℃ is used. The acid includes sulfuric acid or hydrochloric acid, and the salt includes NaCl or CaCl2.

[0028] Furthermore, the post-processing involves kneading using a rubber internal mixer or open mill to suppress the self-agglomeration of modified or unmodified lignin particles caused by surface hydroxyl groups, thereby improving their dispersion in the continuous rubber phase. During this process, unmodified lignin can also be modified by reacting with modifiers such as hydroxymethyl donors, aminomethyl donors, or acetyl donors. Alternatively, antioxidants, inorganic or organic fillers for rubber, plasticizers or softeners, and other rubber functional additives can be added at this stage to produce multi-component composite materials.

[0029] This invention has the following characteristics and beneficial effects:

[0030] 1. This invention relates to an improved composite material for manufacturing rubber products, which achieves a microscopic or submicroscopic structure of lignin encapsulated in rubber during co-precipitation. Macroscopically, the coprecipitate without solid-liquid separation is granular or agglomerated rather than powdery. The microscopic structure of lignin encapsulated in rubber refers to lignin encapsulated in rubber at a scale between angstroms (Å) and nanometers (nm), such as alkali lignin treated by acid precipitation, which is encapsulated within rubber molecules at a scale between Å and nanometers. The submicroscopic structure of lignin encapsulated in rubber refers to lignin encapsulated in rubber at a scale between nanometers and micrometers, such as alkali lignin modified by aminomethylation or hydroxymethylation, and lignin obtained by mechanical, semi-chemical, or semi-chemical-semi-mechanical processes separating cellulose and lignin, which is encapsulated within rubber molecules at a scale between nanometers and micrometers. Therefore, it can solve the problems of existing lignin-rubber composite materials, such as the internal microstructure of the composite material being a micro or submicroscopic structure of lignin encapsulating rubber, poor physical and mechanical properties, limited lignin collection range, and high lignin preparation cost. It has the advantages of a composite material with an internal microstructure of rubber encapsulating lignin, better physical and mechanical properties, a wider lignin collection range, and lower lignin preparation cost.

[0031] 2. The improved method for preparing composite materials for manufacturing rubber products involved in this invention expands the range of lignin that can be used in rubber. It can use lignin obtained from alkaline pulping, lignin obtained from semi-chemical / semi-mechanical paper pulping, or lignin obtained from semi-chemical / semi-mechanical paper pulping, or lignin obtained from separating cellulose and lignin using other alkaline, mechanical, semi-chemical, or semi-chemical / semi-mechanical processes as raw materials. By achieving a micro- or sub-microscopic structure of lignin encapsulated in rubber during co-precipitation, it solves the problems of existing methods for preparing lignin-rubber composite materials, which result in poor physical and mechanical properties due to the internal microstructure of the composite material being a lignin-encapsulated rubber micro- or sub-microscopic structure, a limited range of applicable lignin, and high lignin preparation costs. This method offers the advantages of a rubber-encapsulated lignin micro- or sub-microscopic structure as the internal microstructure of the composite material, better physical and mechanical properties, a wider range of applicable lignin, and lower lignin preparation costs.

[0032] 3. The present invention is based on the fact that the lignin encapsulated in rubber has a scale between angstroms (Å) and nanometers (nm). For example, alkali lignin that has undergone acid precipitation is encapsulated in rubber molecules at a scale between angstroms and nanometers. The so-called submicroscopic structure of rubber-encapsulated lignin refers to the lignin encapsulated in rubber having a scale between nanometers and micrometers. It has the characteristics of compact internal molecular structure, good physical and mechanical properties, and wide applicability.

[0033] 4. Since the present invention can use lignin obtained by alkaline pulping as raw material, or lignin obtained by semi-chemical and semi-mechanical paper pulping, or semi-chemical and semi-mechanical paper pulping, or lignin obtained by separating cellulose and lignin by other alkaline or mechanical, semi-chemical, or semi-chemical and semi-mechanical processes as raw material, it has the characteristics of a wide range of lignin collection and low lignin preparation cost. Detailed Implementation

[0034] Specific Example 1: The preparation method of the product in this example uses lignin obtained from semi-chemical and semi-mechanical pulping to co-precipitate with nitrile latex to prepare nitrile-based lignin / rubber composite material for reinforcing and filling rubber.

[0035] The raw material lignin obtained from semi-chemical and semi-mechanical pulping is a blocky substance obtained by flocculation and pressure filtration of pulping wastewater. It is weakly acidic. The measured raw material lignin is mixed with measured water and NaOH, pulped, and the pulp is filtered through a 100-300 mesh filter. The filter residue is discarded to obtain a lignin dispersion. The solid content of the lignin dispersion is 5-30%, and the pH value is 4.0-7.5.

[0036] Antioxidant is added to nitrile rubber latex, and the solid content of nitrile rubber latex is adjusted with water to make the mixture of nitrile rubber latex and lignin dispersion have a suitable viscosity. A metered amount of lignin dispersion is added to a metered amount of nitrile rubber latex. In this example, the ratio of oven-dry lignin to oven-dry nitrile rubber is 100:100. The mixture is allowed to stand at room temperature to -45°C for an appropriate time. After the mixture thickens significantly, it is heated to 48-80°C for about 0.5-2 hours. If necessary, a metered amount of flocculant is added while stirring. The flocculant is an acid (such as sulfuric acid), a salt (such as CaCl2), and CA (dicyandiamine formaldehyde condensate) or a mixture of the three to promote phase change and demulsification of the latex system, resulting in the co-precipitation of the submicroscopic structure of lignin encapsulated by rubber.

[0037] After co-precipitation, if necessary, maintain the system temperature at 48-80℃ for further maturation for 5-60 minutes before discharging. Then proceed with subsequent solid-liquid separation, washing, and drying operations. For washing, use hot water at room temperature to 80℃. After kneading using a rubber internal mixer or open mill, obtain acrylonitrile-based lignin / rubber composite material.

[0038] Performance testing: The physical and mechanical properties of the rubber compound are tested using the usual formulation system and test methods for evaluating the performance of nitrile rubber reinforcing fillers.

[0039] Test sample: the butadiene-acrylonitrile lignin / rubber composite material obtained in this embodiment.

[0040] Table 1. Basic fit and physical and mechanical properties of the test samples.

[0041]

[0042] In the test sample of nitrile-based lignin / rubber composite material, the ratio of lignin to nitrile rubber is 100 / 100. As shown in Table 1, lignin has a reinforcing effect on nitrile rubber, and the compound has a low proportion of rubber, which has the advantage of saving rubber resources and reducing costs.

[0043] Specific Examples 2 and 3: Specific Example 2 involves test sample 2, which is a co-precipitation of alkali lignin and natural rubber latex to prepare a natural rubber-based lignin / rubber composite material, used as an adhesion promoter between rubber and the skeleton material. Specific Example 3 involves test sample 3, which is a co-precipitation of alkali lignin and styrene-butadiene rubber latex to prepare a styrene-butadiene rubber-based lignin / rubber composite material, used as an adhesion promoter between rubber and the skeleton material.

[0044] Alkali lignin is obtained by spray drying of black liquor from alkaline pulping. A measured amount of alkali lignin is dissolved in a measured amount of water, and a measured amount of oxalic acid is added to the alkali lignin solution to adjust the pH value, thus obtaining a lignin dispersion. The lignin dispersion has a pH value of 4.0-7.5 and a solid content of 5-30%.

[0045] The solid content of natural rubber latex and styrene-butadiene rubber latex was adjusted to 5-30% with water to ensure suitable viscosity in the mixtures of natural rubber latex, styrene-butadiene rubber latex, and lignin dispersion. Measured amounts of lignin dispersion were added to measured amounts of natural rubber latex and styrene-butadiene rubber latex, respectively. For test sample 2, the ratio of oven-dry lignin to oven-dry natural rubber was 100:100; for test sample 3, the ratio was 100:100. The mixtures were allowed to stand at room temperature (-45℃) for an appropriate time. After a phase change occurred, the mixtures were heated to 18-80℃ for approximately 0.5-2 hours. If necessary, measured amounts of flocculant were added while stirring. The flocculant could be an acid (such as sulfuric acid), a salt (CaCl2), dicyandiamine formaldehyde condensate (CA), or a mixture of these three substances. This promoted demulsification of the latex system, resulting in the co-precipitation of the lignin microstructure encapsulated in rubber.

[0046] After co-precipitation, if necessary, maintain the system temperature at 40-80℃ for further maturation for 5-60 minutes before discharging. Then proceed with subsequent solid-liquid separation, washing, and drying operations. During washing, use hot water at room temperature to 80℃. After drying, test samples 2 and 3 are obtained, namely, natural rubber-based lignin / rubber composite material and styrene-butadiene rubber-based lignin / rubber composite material.

[0047] Performance testing: The physical and mechanical properties of the rubber compound were tested using the usual tire steel cord fabric compounding system and the H-extraction test method to evaluate the effect of lignin as an adhesive enhancer between rubber and reinforcing steel wire.

[0048] Test samples: namely, test sample 2 of natural rubber-based lignin / rubber composite material and test sample 3 of styrene-butadiene rubber-based lignin / rubber composite material obtained in this embodiment.

[0049] Control sample: Phenolic resin RN 3260 and HMMM-65 were used together.

[0050] Table 2 Basic Mixture Table and Physical and Mechanical Properties of Test Samples

[0051]

[0052]

[0053] RN 3260 is a commercially available phenolic resin. In the test samples, the ratio of lignin to rubber in the natural rubber-based lignin / rubber composite and the styrene-butadiene rubber-based lignin / rubber composite was 100 / 100. Observation of the surface morphology of the steel wire after H extraction revealed rubber adhesion. Table 2 shows that lignin enhances the adhesion between natural rubber and the reinforcing steel wire, and since lignin is non-toxic and harmless, it can be used as a safe and environmentally friendly rubber adhesion promoter.

[0054] Specific Examples 4 and 5: Specific Example 4 involves test sample 4, which is lignin obtained from a semi-chemical, semi-mechanical pulping process. After purification, it is directly mixed with nitrile rubber to prepare a nitrile-based lignin / rubber composite material, used as a rubber reinforcing filler. Specific Example 4 also involves test sample 5, which is lignin obtained from a semi-chemical, semi-mechanical pulping process. After purification, it is directly mixed with styrene-butadiene rubber to prepare a phenylbutadiene lignin / rubber composite material, used as a rubber reinforcing filler.

[0055] The lignin obtained from semi-chemical and semi-mechanical pulping is a lumpy substance produced by flocculation and pressure filtration of pulping wastewater. It is weakly acidic. A measured amount of raw lignin is mixed with a measured amount of water, pulped, and the pulp is filtered through a 100-300 mesh screen. The filter residue is discarded, and the pulp is dehydrated and dried to obtain lignin. A measured amount of lignin is then kneaded with nitrile rubber or styrene-butadiene rubber using a rubber internal mixer or open mill to produce nitrile-based lignin / rubber composites and styrene-butadiene lignin / rubber composites, namely test samples 4 and 5.

[0056] Performance testing: The physical and mechanical properties of rubber compounds are tested using conventional methods.

[0057] Test samples: These are the test samples obtained using this embodiment, where test sample 4 is a nitrile lignin / rubber composite material and test sample 5 is a butyl phenyl lignin / rubber composite material.

[0058] Table 3. Basic Mixture Table and Physical and Mechanical Properties of Test Samples

[0059]

[0060] In the test samples of nitrile rubber-based lignin / rubber composites and styrene-butadiene rubber-based lignin / rubber composites, the lignin / rubber ratio was 100 / 100. As shown in Table 3, lignin has suitable reinforcing and filling capabilities for both nitrile rubber (a representative polar rubber) and styrene-butadiene rubber (a representative non-polar rubber).

[0061] Specific Example 6: The test sample 6 involved in Specific Example 6 is lignin obtained from semi-chemical and semi-mechanical pulping. After purification, it is directly mixed with nitrile rubber to prepare nitrile-based lignin / rubber composite material, which is used as a rubber reinforcing filler and adhesive promoter.

[0062] The lignin obtained from semi-chemical and semi-mechanical pulping is a lumpy substance produced by flocculation and pressure filtration of pulping wastewater. It is weakly acidic. A measured amount of raw lignin is mixed with a measured amount of water, pulped, and the pulp is filtered through a 100-300 mesh screen. The filter residue is discarded, and the pulp is dehydrated and dried to obtain lignin. A measured amount of lignin is then kneaded with nitrile rubber using a rubber mixer or open mill to obtain a nitrile-based lignin / rubber composite material, i.e., test sample 6.

[0063] Performance testing: The physical and mechanical properties of the rubber compound were tested using a conventional hydraulic steel wire braided hose base rubber compound system and the H-extraction test method to evaluate the reinforcing effect of lignin on the rubber and the adhesion enhancement effect of the skeleton steel wire.

[0064] Test sample: the butadiene-acrylonitrile lignin / rubber composite material obtained in this embodiment.

[0065] Control samples: N660 carbon black and phenolic resin RC.

[0066] Table 4. Basic Mixture and Physical-Mechanical Properties of Test Samples

[0067]

[0068]

[0069] In the nitrile-based lignin / rubber composite material of the test sample, the ratio of lignin to nitrile rubber is 100 / 100. Observation of the surface morphology of the steel wire after H extraction revealed rubber adhesion. Table 4 shows that, compared to the control sample, the test sample exhibits a better adhesion-enhancing effect on the nitrile rubber and the reinforcing steel wire. Furthermore, lignin is non-toxic and harmless, making it a safe and environmentally friendly rubber adhesion promoter. The reinforcing effect of lignin on nitrile rubber is roughly equivalent to that of N660 carbon black.

[0070] In production practice, in addition to papermaking and pulping, the production of bioethanol also uses similar processes to separate cellulose and lignin from grasses, herbs, woody plants, and vines. After obtaining cellulose, it is fermented to prepare bioethanol. Cellulose and lignin are separated by alkaline methods and mechanical, semi-chemical, and semi-chemical-semi-mechanical processes. The resulting lignin also meets the scope of this patent application.

[0071] Lignin from different sources has different application methods and prospects as a material in the rubber industry. Patent application No. 200610139529.7, "Non-random Styrene-Butadiene Rubber," uses lignin sulfonate (also called sulfonated lignin or lignin sulfite) or kraft paper lignin (also called lignin sulfate) obtained by sulfite pulping; patent application No. 202180029904.5, "High Impermeability Inner Liner Compound and Manufacturing Method Thereof," uses sulfate lignin; patent application No. 201480008164.7, "Tire Carcass Cord Layer Separator," uses sulfonated lignin; patent application No. 201780028647.7, "Adhesive Compound for Reinforcing Cord Layers in Tires," uses sulfonated lignin; and patent application No. 202110278203.7, "Environmentally Friendly Rubber Composition for Tires Containing Lignin Compounds," uses sulfate lignin (Kraft... The lignin used in this invention includes lignin, lignin sulfonate, alkali lignin, or mixtures thereof; the functionalized lignin used in the invention patent "Tire for Wheels" with authorization announcement number CN 104837910 B is selected from esterified sulfur-free lignin as well as etherified and esterified lignin; the invention patent application "Lignin in Tire Components" with application number 200880129551.0 directly uses lignin obtained by spray drying from black liquor separated from cellulose during the kraft pulping process. The above and similar technical solutions differ from the lignin sources and raw materials used in this invention.

[0072] The product prepared by this invention exhibits lignin dispersion at the nanoscale or even molecular level in rubber, thus possessing uniformity and excellent physical, mechanical, and other properties. The semi-chemical / semi-mechanical papermaking pulping process, or similar processes for separating cellulose and lignin from grasses, herbs, woody plants, and vines—such as obtaining lignin from cellulose through fermentation to prepare bioethanol—can be purified and directly compounded with rubber to produce composite materials. Compared to existing technologies, this significantly shortens the process flow and expands the range of lignin applicable in the rubber industry.

[0073] In this invention, when wet blending is used, the co-precipitate is macroscopically shaped into clumps or granules rather than powder before solid-liquid separation. Compared with powdered materials, this reduces loss and increases yield during solid-liquid separation, thereby reducing costs and pollutant emissions. At the same time, the hydrophobicity of the rubber phase wrapped around the lignin phase in the clumps or granules of the co-precipitate can be utilized to automatically release most of the water before solid-liquid separation, which is more energy-efficient than existing technologies.

[0074] This invention expands the range of lignins applicable to rubber. It allows the use of lignin obtained from alkaline pulping, lignin obtained from semi-chemical / semi-mechanical paper pulping, or lignin obtained from semi-chemical / semi-mechanical paper pulping, or lignin obtained from mechanical paper pulping, or lignin obtained from other processes that separate cellulose and lignin using alkaline, mechanical, semi-chemical, or semi-chemical / semi-mechanical processes. Specifically, the use of lignin obtained from semi-chemical / semi-mechanical paper pulping, or semi-chemical / semi-mechanical paper pulping, to manufacture composite materials with rubber, and as a raw material for manufacturing rubber products, has not been reported in the literature for any other identical or similar technical solutions.

[0075] The technical solution adopted in this invention aims to achieve a microscopic or submicroscopic structure of lignin encapsulated in rubber during co-precipitation. Macroscopically, the coprecipitate without solid-liquid separation is granular or agglomerated rather than powdery. The microscopic structure of lignin encapsulated in rubber refers to lignin encapsulated in rubber at a scale between angstroms (Å) and nanometers (nm), such as alkali lignin after acid precipitation, which is encapsulated within rubber molecules at a scale between Å and nanometers. The submicroscopic structure of lignin encapsulated in rubber refers to lignin encapsulated in rubber at a scale between nanometers and micrometers, such as alkali lignin modified by aminomethylation or hydroxymethylation, and lignin obtained by separating cellulose and lignin using mechanical, semi-chemical, or semi-chemical-semi-mechanical processes, which is encapsulated within rubber molecules at a scale between nanometers and micrometers. The coprecipitate without solid-liquid separation is macroscopically powdery, and usually has a micro- or submicroscopic structure of lignin-encapsulated rubber or a hybrid structure of rubber-encapsulated lignin. Such changes and fluctuations in micro- or submicroscopic phase structure lead to fluctuations and inferior quality of lignin / rubber composite materials in industrial production, which does not meet the purpose of this invention.

[0076] Before mixing the lignin dispersion with rubber latex, the pH of the multi-component dispersion composed of the lignin dispersion and contingent antioxidants, inorganic or organic fillers for rubber, plasticizers or softeners, and other rubber functional additives is adjusted so that the pH of the lignin dispersion or multi-component dispersion is 4.0-7.5 before mixing with rubber latex.

[0077] To obtain homogeneous coprecipitates, lignin dispersions typically require stirring after being mixed into rubber latex to initiate coprecipitation. However, the technical solution adopted in this invention requires the material to stand at room temperature (-45°C) for 5 minutes to 72 hours before coprecipitation solidification to allow for phase transition preparation before latex demulsification. The lignin obtained from alkali pulping, lignin obtained through appropriate modification, and lignin obtained from semi-chemical / semi-mechanical papermaking pulping, semi-chemical papermaking pulping, or mechanical papermaking pulping have a specific gravity of approximately 1.1-1.3, which meets the requirement for a longer standing time. In contrast, lignin sulfonates obtained from sulfite pulping have a specific gravity ≥1.5, and therefore cannot be covered by the technical solution of this invention.

[0078] The co-precipitation coagulation scheme adopted in this invention involves mixing a measured amount of lignin with, or contingent, antioxidants, inorganic or organic fillers for rubber, plasticizers or softeners, and other rubber functional additives in dispersion form with a measured amount of rubber latex under stirring, allowing the mixture to stand, and after the latex phase exhibits thickening or other phase change phenomena, heating the system to 18-80°C for approximately 0.5-2 hours. If necessary, a measured amount of flocculant is added under stirring. The flocculant is an acid (such as sulfuric acid), a salt (such as NaCl, CaCl2, etc.), and CA (dicyandiamine formaldehyde condensate), or a mixture of the three, which promotes phase change and demulsification of the latex system, resulting in co-precipitation of lignin with a microscopic or submicroscopic structure encapsulated in rubber. The coprecipitate is granular or agglomerated rather than powdery.

[0079] After the co-precipitation operation is completed, if necessary, maintain the system temperature at 40-80℃ for 5-60 minutes to continue maturation before discharging the material. Then proceed with subsequent solid-liquid separation, washing, and drying operations. During washing, use hot water at room temperature to 80℃.

[0080] This invention achieves a microscopic or submicroscopic structure of lignin encapsulated in rubber during co-precipitation, rather than a microscopic or submicroscopic structure of rubber encapsulated by non-lignin, or a microscopic or submicroscopic structure of lignin encapsulated by hybrid rubber. This allows lignin to achieve nanoscale or even molecular-level dispersion in the rubber, resulting in uniform and excellent physical, mechanical, and other properties. Before solid-liquid separation, the coprecipitate macroscopically appears as clumps or granules rather than powder, reducing loss and increasing yield compared to powdered materials during solid-liquid separation. This reduces costs and pollutant emissions. Furthermore, the hydrophobicity of rubber allows most of the water to be automatically released from the coprecipitate before solid-liquid separation, resulting in greater energy savings compared to the invention patent with authorization announcement number CN 102718995 B and the invention patent application number 201310261451.6.

Claims

1. An improved composite material for manufacturing rubber products, characterized by: 1) The composite material comprises lignin, rubber and functional additives, and the mass weight ratio of each component is lignin: rubber: functional additives = 1-280: 98-102: 0-280; 2) The lignin is obtained by alkaline pulping, semi-chemical and semi-mechanical papermaking pulping, or semi-chemical papermaking pulping or mechanical papermaking pulping, or by fermenting cellulose from grass, herbaceous, woody and vine plants separated by similar processes to prepare bioethanol; 3) The rubber is natural rubber, synthetic rubber, or a combination of natural rubber and synthetic rubber. 4) The functional additive is an antioxidant, an inorganic or organic filler for rubber, a plasticizer or a softener, or one or more other rubber functional additives besides the aforementioned functional additives; 5) Prepare coprecipitates of composite materials with a micro or submicroscopic structure of lignin encapsulated in rubber.

2. An improved composite material for manufacturing rubber products as described in claim 1, characterized in that: The other rubber functional additives include one or more combinations of zinc oxide, stearic acid, sulfur, organic peroxides, and accelerators.

3. The improved method for preparing a composite material for manufacturing rubber products as described in claim 1, characterized in that: The composite material was prepared by co-precipitation of lignin dispersion and rubber latex emulsion.

4. The improved method for preparing a composite material for manufacturing rubber products as described in claim 1, characterized in that: When the lignin source is semi-chemical / semi-mechanical papermaking pulping or semi-chemical papermaking pulping or mechanical papermaking pulping, and when lignin and cellulose in grass, herbaceous, woody, and vine plants are separated by similar processes, such as obtaining lignin from cellulose through fermentation to prepare bioethanol, the lignin is purified and then directly mixed with rubber to produce composite materials, i.e., dry method production of composite materials; or the raw material lignin is modified or unmodified, prepared into a dispersion with a solid content of 5-30% and adjusted, and then mechanically mixed with rubber latex with a solid content of 5-30%, allowed to stand, co-precipitate, and matured to form a micro or submicroscopic structure in which lignin is wrapped in rubber. After solid-liquid separation, washing, drying, and post-treatment if necessary, a composite material is produced with rubber as the continuous phase and lignin and antioxidants, inorganic or organic fillers for rubber, plasticizers or softeners, and other rubber functional additives present in the composite material components as the dispersed phase.

5. The improved method for preparing a composite material for manufacturing rubber products as described in claim 1, characterized in that: When the weight ratio of lignin to rubber is 1-200:100, lignin mainly functions as a reinforcing filler in rubber products, while also acting as an adhesive enhancer and flame retardant synergist. When the weight ratio of lignin to rubber is 200-280:100, lignin mainly functions as a functional material in rubber products, including acting as an adhesive enhancer between rubber and the skeleton material, or as a flame retardant synergist.

6. An improved method for preparing a composite material for manufacturing rubber products as described in claim 2, characterized in that: The composite material contains antioxidants, inorganic or organic fillers for rubber, plasticizers or softeners, and other rubber functional additives, which are mixed with lignin to form a multi-component dispersion and co-precipitated with rubber latex.

7. An improved method for preparing a composite material for manufacturing rubber products as described in claim 4, characterized in that: The modification of raw lignin refers to phenolization, sulfonation, hydroxymethylation, aminomethylation, halogenation, nitration, alkylation, acetylation, quaternization, grafting modification of lignin, or a combination of two or more modifications, including acetylated hydroxymethylation modification, acetylated aminomethylation modification, hydroxymethylated phenol grafting modification, and acetylated hydroxymethylated phenol grafting modification. The adjustment refers to the use of strong acidic substances such as oxalic acid, sulfuric acid, hydrochloric acid, or nitric acid, and strong alkaline substances such as NaOH or Na2S, to adjust the pH of the lignin dispersion so that the pH value of the lignin dispersion before mixing with rubber latex is 4.0-7.

5.

8. An improved method for preparing a composite material for manufacturing rubber products as described in claim 4, characterized in that: Rubber latex is natural rubber latex, synthetic rubber latex, or latex obtained by emulsifying block, granular, or powdered rubber or resin obtained by solution polymerization or bulk polymerization, or a metered physical mixture of natural rubber latex and synthetic rubber latex. Before mixing rubber latex with lignin dispersion, the viscosity of the system should be adjusted by adjusting its solid content. The suitable solid content of latex is 5-30% so that the blended system after mixing latex and lignin dispersion has a good sedimentation rate and does not separate into layers when standing. After mixing rubber latex with lignin dispersion, the standing time at room temperature to 45°C is 5 minutes to 72 hours.

9. An improved method for preparing a composite material for manufacturing rubber products as described in claim 4, characterized in that: [The method involves...] The aim is to achieve a micro or submicroscopic structure of lignin encapsulated in rubber in the co-precipitate. A measured amount of lignin, along with contingent antioxidants, inorganic or organic fillers for rubber, plasticizers or softeners, and other rubber functional additives, is mixed in dispersion form with a measured amount of rubber latex under stirring. The mixture is allowed to stand until the latex phase thickens or undergoes other phase changes. The system is then heated to 18-80°C for approximately 0.25-3 hours. If necessary, a measured amount of flocculant is added under stirring. The flocculant can be an acid, salt, or dicyandiamine-formaldehyde condensate C. A, or a mixture of the three, is used to induce phase change and demulsification of the latex system, resulting in the co-precipitation of lignin in a microscopic or submicroscopic structure encapsulated by rubber. The co-precipitate is granular or agglomerated rather than powdery. After the co-precipitation operation, if necessary, the system temperature is maintained at 40-80℃ for 5-60 minutes for further maturation before discharge. Then, subsequent solid-liquid separation, washing, and drying operations are performed. During washing, hot water at room temperature to 80℃ is used. The acid includes sulfuric acid or hydrochloric acid, and the salt includes NaCl or CaCl2.

10. An improved method for preparing a composite material for manufacturing rubber products as described in claim 1, characterized in that: The post-processing involves kneading using a rubber internal mixer or open mill to suppress the self-agglomeration of modified or unmodified lignin particles caused by surface hydroxyl groups, thereby improving their dispersion in the continuous rubber phase. During this process, unmodified lignin can also be modified by reacting with modifiers such as hydroxymethyl donors, aminomethyl donors, or acetyl donors. Alternatively, antioxidants, inorganic or organic fillers for rubber, plasticizers or softeners, and other rubber functional additives can be added at this stage to produce multi-component composite materials.

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