Micro-nano cellulose reinforcing filler, preparation method thereof and cellulose-rubber composite material

Abstract

The invention relates to the technical field of rubber production, and discloses a micro-nano cellulose reinforcing filler, a preparation method thereof and a cellulose-rubber composite material. The preparation method of the micro-nano cellulose reinforcing filler comprises the following steps: carrying out oxidation treatment on cellulose to obtain modified cellulose with carboxyl functional groups; and carrying out transesterification on the modified cellulose and an unsaturated ester compound to obtain the micro-nano cellulose reinforcing filler. The method does not need traditional homogenization treatment, and is low in energy consumption and high in yield; the hydrogen bond acting force between cellulose molecules is reduced, the aggregation of the nano cellulose caused by hydrogen bonds can be effectively prevented, and the preparation process is simplified. The cellulose reinforcing filler prepared by the invention is a nanoscale cellulose sheet, and has high dispersity and good compatibility in polar rubber; high fraction filling can be realized, the thickness of an interface layer is improved, and external stress is effectively dissipated; the prepared cellulose-rubber composite material is low in compression temperature rise and rolling resistance and excellent in wet skid resistance.

Description

Technical Field

[0001] The present application relates to the technical field of rubber production, and particularly relates to a micro-nano cellulose reinforcing filler, a preparation method thereof, and a cellulose-rubber composite material. Background Art

[0002] Carbon black and white carbon black are commonly used fillers in rubber products, which can significantly improve the mechanical properties of rubber. However, the preparation processes of carbon black and white carbon black have problems such as high energy consumption, complex processes, and environmental pollution. At present, the demand for bio-based fillers with low energy consumption and environmental friendliness has increased greatly. As a bio-based material with a certain degree of crystallinity, cellulose has a reinforcing advantage in modulus and has great potential in the field of bio-based fillers.

[0003] The surface of cellulose contains a large number of hydroxyl groups, and has poor compatibility with natural rubber and styrene-butadiene rubber commonly used in industrial production. Therefore, cellulose usually needs to be surface-modified to reduce its surface energy, improve the interfacial interaction between cellulose and rubber, and improve the dispersion of cellulose in the rubber matrix. The methods for modifying cellulose are mainly divided into two categories: physical modification and chemical modification. For example, cellulose is modified with a silane coupling agent, or an esterification reaction is carried out under the condition of a high dosage of catalyst to graft an alkane chain containing an unsaturated double bond on the surface of cellulose. The existing methods for modifying cellulose have problems such as complex processes, use of a large amount of organic solvents, and low modification efficiency. In addition, the size control of modified cellulose is a major problem. Due to the low solvent accessibility of the cellulose crystalline region, it is difficult to obtain nano-cellulose powder that can be used as a rubber filler through a mild, simple, and efficient method.

[0004] At present, the processes for preparing cellulose-rubber composites mainly include latex compounding methods (natural latex, styrene-butadiene latex), and by modifying cellulose in a solvent to reduce its hydrophilicity, and then adding it to the rubber matrix by wet or dry methods. However, in the above two types of methods, the filling amount of cellulose in rubber is limited, and the dispersion degree and interfacial bonding of cellulose in the rubber matrix cannot be significantly improved, resulting in the performance of cellulose-rubber composites being lower than that of existing carbon black-rubber composites, which limits their wide application.

[0005] Based on this, it is urgent to develop a nano-scale cellulose filler with a simple preparation process, low energy consumption, and high yield, as well as a high-performance cellulose-rubber composite material. Summary of the Invention

[0006] The present application provides a micro-nano cellulose reinforcing filler, a preparation method thereof, and a cellulose-rubber composite material, aiming to solve the problems of complex preparation process, high energy consumption, and low yield existing in the existing cellulose reinforcing filler, as well as the technical problem of low performance of the existing cellulose-rubber composite material.

[0007] To achieve the above object, the present application adopts the following technical solutions for implementation.

[0008] In the first aspect of the present application, a preparation method of a micro-nano cellulose reinforcing filler is provided, including:

[0009] Subjecting cellulose to oxidation treatment to obtain modified cellulose with carboxyl functional groups;

[0010] Carrying out a transesterification reaction between the modified cellulose and an unsaturated ester compound to obtain a micro-nano cellulose reinforcing filler.

[0011] Preferably, the degree of oxidation of the modified cellulose is 1-12%.

[0012] Preferably, the transesterification reaction is a mechanical transesterification reaction, including: subjecting the modified cellulose and the unsaturated ester compound to ball milling or high-speed pulverization, so that the carboxyl functional groups of the modified cellulose react with the unsaturated ester compound in a transesterification reaction;

[0013] Wherein, the mass ratio of the modified cellulose to the unsaturated ester compound is 100:(1-30), and the temperature of the transesterification reaction is 25-90°C.

[0014] Preferably, the cellulose includes at least one of microcrystalline cellulose, nano-crystalline cellulose, nano-cellulose fiber, and nano-cellulose sheet;

[0015] And / or,

[0016] The ester compound includes one, two, or three ester groups.

[0017] Preferably, the unsaturated ester compound includes at least one of methyl acrylate, ethyl acrylate, ethyl sorbate, methyl cocoate, dioleoyl glycerol arachidonate, diglycerol myristate, dioleoyl glycerol docosahexaenoate, dioleoyl glycerol, 1,3-dioleoyl glycerol, trioleoyl glycerol, trilinoleoyl glycerol, or trialpha-linolenoyl glycerol.

[0018] In the second aspect of the present application, a micro-nano cellulose reinforcing filler prepared by the above preparation method is provided.

[0019] In the third aspect of the present application, the application of the micro-nano cellulose reinforcing filler in a rubber composite material is provided.

[0020] In the fourth aspect of the present application, a preparation method of a cellulose-rubber composite material is provided, including:

[0021] Adding raw rubber, a reinforcing filler, and a silane coupling agent into a mixer for the first mixing to obtain a mixed rubber;

[0022] Add the mixed rubber and vulcanizing agent to the open mill and conduct the second mixing at room temperature; subject the mixed rubber after the second mixing to hot press vulcanization to obtain a cellulose-rubber composite material;

[0023] The reinforcing filler is the above-mentioned micro-nano cellulose reinforcing filler or a mixture of the above-mentioned micro-nano cellulose reinforcing filler and carbon black.

[0024] Preferably, the mass ratio of the raw rubber to the reinforcing filler is 100:(30-50);

[0025] and / or,

[0026] The dosage of the silane coupling agent is 0%-15wt% of the dosage of the reinforcing filler;

[0027] and / or,

[0028] The temperature of the first mixing is 25-80°C and the time is 5-10 min;

[0029] and / or,

[0030] The temperature of the hot press vulcanization is 143°C.

[0031] In the fifth aspect of the present application, a cellulose-rubber composite material prepared by the above preparation method is provided.

[0032] Compared with the prior art, the beneficial effects of the present application are as follows:

[0033] In the present application, carboxyl groups are introduced into cellulose by an oxidation method, and then a cellulose reinforcing filler is obtained through a mechanochemical transesterification reaction, without the need for traditional homogenization treatment, which has the characteristics of low energy consumption and high yield; this preparation method reduces the hydrogen bond force between cellulose molecules, can effectively prevent the aggregation of nanocellulose caused by hydrogen bonds, which makes it difficult to be nano-sized, so that nanoscale cellulose can be obtained only by mechanical destruction, and it still remains nanoscale after spray drying, greatly simplifying the preparation process.

[0034] The cellulose reinforcing filler prepared in this application is nano-scale cellulose sheets, which have high dispersibility and good compatibility in polar rubbers. It not only has a higher proportion of bound rubber, enabling high-loading filling, increasing the thickness of the interface layer, and effectively dissipating external stress; but also has low anisotropy, overcoming the shortcomings of the aspect ratio of existing cellulose during rubber reinforcement, resulting in low strength differences between the transverse and longitudinal directions of the cellulose-rubber composite; in addition, through the high conformational transformation barrier energy of nano-cellulose, the periodic dynamic stress directly acting on natural rubber can be eliminated, reducing the heat generated by natural rubber due to internal friction, thereby achieving low compression heat build-up. Unsaturated esters have relatively high transesterification reactivity, improving the modification efficiency, and the cellulose modified with them has unsaturated double bonds that can participate in the vulcanization process of rubber composites, enhancing the interfacial bonding with the rubber matrix. Based on the synergistic effects of the above aspects, the cellulose reinforcing filler of this application can endow the cellulose-rubber composite with lower compression temperature rise and rolling resistance, as well as more excellent wet skid resistance.

[0035] The cellulose-rubber composite prepared in this application has low compression temperature rise, low rolling resistance, and excellent wet skid resistance. Compared with the carbon black-filled sample, it has a comparable mechanical modulus (300% modulus at 14.8 MPa), with a 41% improvement in wet skid resistance, a 41% reduction in compression fatigue heat build-up, and a 29% reduction in rolling resistance. Brief Description of the Drawings

[0036] To more clearly illustrate the technical solutions of the embodiments of this application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments recorded in this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0037] Figure 1 DMA curve graphs of Samples 1-4 and Comparative Sample 2 prepared in this application;

[0038] Figure 2 Scanning electron microscope image of Sample 2 prepared in this application;

[0039] Figure 3 Scanning electron microscope image of Sample 3 prepared in this application;

[0040] Figure 4 Transverse and longitudinal tensile curve graphs of Sample 5 prepared in this application. Detailed Description of the Embodiments

[0041] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0042] In the following description of this embodiment, the terms "including", "comprising", "having", and "containing" are all open-ended terms, meaning including but not limited to.

[0043] In the following description of this embodiment, the term "and / or" is used to describe the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, B exists alone, and both A and B exist simultaneously. Wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after.

[0044] In the following description of this embodiment, the term "at least one" means one or more, and "a plurality" means two or more. "At least one of the following items" or its similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or, "at least one of a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0045] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0046] Those skilled in the art should understand that in the following description of the embodiments of the present application, the sequence numbers do not mean the order of execution. Some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0047] Those skilled in the art should understand that the numerical ranges in the embodiments of the present application should be understood as specifically disclosing each intermediate value between the upper and lower limits of the range. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present application. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0048] Unless otherwise specified, the technical / scientific terms used herein have the same meanings as commonly understood by those of ordinary skill in the art to which this application pertains. Although this application only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of this application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the said documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0049] In a first aspect, this application provides a method for preparing a micro-nano cellulose reinforcing filler, including:

[0050] Subjecting cellulose to oxidation treatment to obtain modified cellulose with carboxyl functional groups;

[0051] Carrying out a transesterification reaction between the modified cellulose and an unsaturated ester compound to obtain the micro-nano cellulose reinforcing filler.

[0052] In this application, the oxidation treatment of cellulose is carried out by the hydrogen peroxide oxidation method disclosed in Patent CN104017090B. Preferably, its degree of oxidation is 1-12%, and modified cellulose with carboxyl groups on the surface is obtained, improving the activity of cellulose.

[0053] In this application, the transesterification reaction is a mechanical transesterification reaction, including: subjecting the modified cellulose and the unsaturated ester compound to ball milling or high-speed pulverization, so that the carboxyl functional groups of the modified cellulose react with the unsaturated ester compound in a transesterification reaction.

[0054] Among them, the mass ratio of the modified cellulose to the unsaturated ester compound is 100:(1-30), and the temperature of the transesterification reaction is 25-90 °C. Specifically, during the ball milling or high-speed pulverization of the modified cellulose and the unsaturated ester compound, the temperature rises due to mechanical friction. When the temperature rises to the range of 25-90 °C, the modified cellulose reacts with the unsaturated ester compound with high reaction activity in a transesterification reaction. Without additional heating, the micro-nano cellulose reinforcing filler can be obtained, greatly reducing energy consumption and having a high yield. The reaction general formula is as follows:

[0055]

[0056] Among them, R1 is the main chain structure of the carboxyl cellulose obtained after oxidation treatment, R is the main chain structure of the cellulose without oxidation treatment, R2 is the hydrocarbon chain of the alcohol corresponding to the ester, and R3 is the hydrocarbon chain of the carboxylic acid corresponding to the ester.

[0057] In this application, carboxyl groups are introduced into cellulose through an oxidation method, and then a cellulose reinforcing filler is obtained through a mechanical transesterification reaction. There is no need to adopt traditional homogenization treatment, which has the characteristics of low energy consumption and high yield. The preparation method of this application reduces the hydrogen bond force between cellulose molecules, effectively preventing the aggregation of nanocellulose caused by hydrogen bonds and making it difficult to be nanosized. Therefore, nanoscale cellulose can be obtained only by mechanical destruction and still remains nanoscale after spray drying, greatly simplifying the preparation process.

[0058] In this application, the cellulose can be selected from at least one of microcrystalline cellulose, nanocrystalline cellulose, nanofibrillated cellulose, and nanocellulose flakes, and preferably microcrystalline cellulose.

[0059] In this application, the unsaturated ester compound can include one, two, or three ester groups, such as monoesters, diesters, or triesters, and it may or may not contain unsaturated double bonds. Specifically, the unsaturated ester compound can be selected from at least one of methyl acrylate, ethyl acrylate, ethyl sorbate, methyl coconutate, diglyceride arachidonate, diglyceride myristate, diglyceride docosahexaenoate, diglyceride oleate, 1,3-dioleoyl glycerol, triolein, trilinolein, or linolenic acid triglyceride.

[0060] The micro-nano cellulose reinforcing filler prepared in this application is nano-scale cellulose flakes and can be used to prepare rubber composites. It has high dispersibility and good compatibility in polar rubbers. On the one hand, it has a higher proportion of bound rubber, can achieve high-loading filling in rubber materials, and thus increases the thickness of the interface layer, effectively dissipating external stress. On the other hand, it has low anisotropy and overcomes the disadvantages of the aspect ratio of existing cellulose when reinforcing rubber, resulting in low strength differences in the transverse and longitudinal directions of the cellulose-rubber composite. Thirdly, the micro-nano cellulose reinforcing filler of this application can eliminate the direct action of periodic dynamic stress on natural rubber through the high conformational transformation barrier energy of nanocellulose, reducing the heat generated by the internal friction of natural rubber, thereby achieving low compression heat generation. The transesterification reaction activity of unsaturated esters is relatively high, improving the modification efficiency. Moreover, the cellulose modified with it has unsaturated double bonds that can participate in the vulcanization process of rubber composites, enhancing the interfacial bonding with the rubber matrix. Due to the synergistic effect of the above aspects, the cellulose reinforcing filler of this application can make the cellulose-rubber composite have higher mechanical properties, lower compression temperature rise and rolling resistance, and more excellent anti-wet skid properties.

[0061] On the other hand, this application provides a method for preparing a cellulose-rubber composite, including:

[0062] Raw rubber, reinforcing filler, and silane coupling agent are added to an internal mixer for the first mixing to obtain a mixed rubber; the temperature of the first mixing is 25 - 80°C, and the time is 5 - 10 min.

[0063] In this application, the reinforcing filler is the above-mentioned micro-nano cellulose reinforcing filler, or a mixture of the above-mentioned micro-nano cellulose reinforcing filler and carbon black; wherein, when the reinforcing filler is a mixture of micro-nano cellulose reinforcing filler and carbon black, the mass of the micro-nano cellulose reinforcing filler is greater than or equal to the amount of carbon black used. The mass ratio of the raw rubber to the reinforcing filler is preferably 100:(30 - 50), more preferably 100:40; the dosage of the silane coupling agent is 0% - 15 wt% of the dosage of the reinforcing filler.

[0064] The mixed rubber and vulcanizing agent are added to an open mill for the second mixing at room temperature; the mixed rubber after the second mixing is subjected to hot press vulcanization to obtain a cellulose-rubber composite material.

[0065] In this application, the raw rubber can be natural rubber or styrene-butadiene rubber.

[0066] The silane coupling agent is used to further improve the dispersion of the micro-nano cellulose reinforcing filler in the rubber matrix and enhance its interfacial bonding with the rubber matrix. The silane coupling agent includes at least one of γ-mercaptopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminoethylaminopropyltrimethoxysilane, bis-[3-(triethoxysilyl)propyl]-tetrasulfide, or bis-[3-(triethoxysilyl)propyl]-disulfide.

[0067] The vulcanizing agent can adopt a common vulcanization system, which includes sulfur, vulcanization activator, and accelerator; wherein, the vulcanization activator includes zinc oxide and stearic acid. When the raw rubber is natural rubber, the dosages of zinc oxide, stearic acid, accelerator, and sulfur in the vulcanizing agent are 5 wt%, 2 wt%, 1.2 wt%, and 1.5 wt% of the dosage of the raw rubber respectively. In the examples of this application, the dosage of the raw rubber is 100 g, and the components of the vulcanizing agent used include 5 g of zinc oxide, 2 g of stearic acid, 1.2 g of accelerator CZ, and 1.5 g of sulfur, and the hot press vulcanization temperature is 143°C.

[0068] The cellulose-rubber composite material prepared in this application has higher mechanical properties, lower compression temperature rise and rolling resistance, and more excellent anti-slip performance when wet. Compared with the sample filled with carbon black, it has a comparable mechanical modulus (300% modulus at elongation of 14.8 MPa), the anti-slip performance when wet is increased by 41%, the compression fatigue heat generation is reduced by 41%, and the rolling resistance is reduced by 29%.

[0069] The present application is further described below through examples.

[0070] In the examples of the present application, the components of the vulcanizing agent used are: 5 g of zinc oxide, 2 g of stearic acid, 1.2 g of accelerator CZ, and 1.5 g of sulfur.

[0071] Example for preparing modified cellulose

[0072] Weigh 20 parts of microcrystalline cellulose by mass and soak it in a potassium carbonate solution with a mass fraction of 24%. After soaking for 2 hours, wash it with distilled water and filter it by suction until it is neutral. Then add 14 parts of hydrogen peroxide, 100 parts of water, and cobalt sulfate accounting for 0.025% of the cellulose mass. Stir with a magnetic stirrer at a temperature of 20 °C for 24 hours. After the oxidation is completed, wash it with distilled water until the pH remains unchanged. Dry the obtained sample in an oven at a temperature of 55 °C for 8 hours to obtain modified cellulose with a high carboxyl content, and measure its carboxyl content to be 6.3%.

[0073] Example 1

[0074] This example provides a preparation method of a micro-nano cellulose reinforcing filler, including:

[0075] Mix 100 g of modified cellulose with 15 g of triglyceride linolenate, and crush it with a high-speed crusher for 3 min. Repeat the crushing process 3 times until a 200-mesh powder is obtained. Place this powder in a forced-air oven at 60 °C and dry it for 12 hours. Process the dried powder with a vibration ball mill at a frequency of 1600 Hz for 30 min to obtain micro-nano cellulose reinforcing filler A.

[0076] Example 2

[0077] This example provides a preparation method of a micro-nano cellulose reinforcing filler, including:

[0078] Mix 100 g of modified cellulose with 20 g of triglyceride linolenate, and crush it with a high-speed crusher for 3 min. Repeat the crushing process 3 times until a 200-mesh powder is obtained. Place this powder in a forced-air oven at 60 °C and dry it for 12 hours. Process the dried powder with a vibration ball mill at a frequency of 1600 Hz for 30 min to obtain micro-nano cellulose reinforcing filler B.

[0079] Example 3

[0080] This example provides a preparation method of a cellulose-rubber composite material, including:

[0081] Add 100 g of natural rubber raw rubber, 40 g of micro-nano cellulose reinforcing filler A, and 3 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane into a Banbury mixer in sequence for the first mixing. The mixing temperature is 45 °C and the time is 8 min to obtain a mixed rubber. Add the mixed rubber and a vulcanizing agent into an open mill and conduct the second mixing at room temperature. Heat press and vulcanize the mixed rubber after the second mixing at 143 °C to obtain a cellulose-rubber composite material, denoted as Sample 1.

[0082] Example 4

[0083] This example provides a preparation method of a cellulose-rubber composite material, including:

[0084] Add 100 g of natural rubber raw rubber, 40 g of micro-nano cellulose reinforcing filler B, and 3 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane into a Banbury mixer in sequence for the first mixing. The mixing temperature is 45 °C and the time is 8 min to obtain a mixed rubber. Add the mixed rubber and a vulcanizing agent into an open mill and conduct the second mixing at room temperature. Heat press and vulcanize the mixed rubber after the second mixing at 143 °C to obtain a cellulose-rubber composite material, denoted as Sample 2.

[0085] Example 5

[0086] This example provides a preparation method of a cellulose-rubber composite material, including:

[0087] Add 100 g of natural rubber raw rubber, 20 g of carbon black, 20 g of micro-nano cellulose reinforcing filler B, and 1.5 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane into a Banbury mixer in sequence for the first mixing. The mixing temperature is 45 °C and the time is 8 min to obtain a mixed rubber. Add the mixed rubber and a vulcanizing agent into an open mill and conduct the second mixing at room temperature. Heat press and vulcanize the mixed rubber after the second mixing at 143 °C to obtain a cellulose-rubber composite material, denoted as Sample 3.

[0088] Example 6

[0089] This example provides a preparation method of a cellulose-rubber composite material, including:

[0090] Add 100 g of natural rubber raw rubber, 10 g of carbon black, 30 g of micro-nano cellulose reinforcing filler A, and 1.5 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane into a Banbury mixer in sequence for the first mixing. The mixing temperature is 45 °C and the time is 8 min to obtain a mixed rubber. Add the mixed rubber and a vulcanizing agent into an open mill and conduct the second mixing at room temperature. Heat press and vulcanize the mixed rubber after the second mixing at 143 °C to obtain a cellulose-rubber composite material, denoted as Sample 4.

[0091] Example 7

[0092] This example provides a method for preparing a cellulose-rubber composite material, including:

[0093] Mix 100 grams of microcrystalline cellulose with 12.5 grams of triglyceride linolenate, and crush it with a high-speed crusher for 3 minutes. Repeat the crushing process 3 times until a 200-mesh powder is obtained. Place the powder in a forced-air oven at 60 °C for drying for 12 hours to obtain a dried powder. Process it with a vibratory ball mill at a frequency of 1600 Hz for 30 minutes to obtain a micro-nano cellulose reinforcing filler C.

[0094] Add 100 g of natural rubber raw rubber, 40 g of micro-nano cellulose reinforcing filler C, and 1.5 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane to an internal mixer in sequence for the first mixing. The mixing temperature is 45 °C and the time is 8 minutes to obtain a mixed rubber. Add the mixed rubber and a vulcanizing agent to an open mill for the second mixing at room temperature. Heat-press vulcanize the mixed rubber after the second mixing at 143 °C to obtain a cellulose-rubber composite material, denoted as sample 5.

[0095] For the longitudinal tensile spline cutting of sample 5, the cutting direction of the tensile spline during hot-press vulcanization is the same as the direction of the sheet produced by the open mill. For the transverse tensile spline cutting of sample 5, the cutting direction of the tensile spline during hot-press vulcanization is perpendicular to the direction of the sheet produced by the open mill.

[0096] Comparative Example 1

[0097] Add 100 grams of natural rubber raw rubber to an internal mixer for plasticizing, and then add it and a vulcanizing agent to an open mill for mixing at room temperature. Heat-press vulcanize the mixed rubber after mixing at 143 °C to obtain a vulcanized rubber, denoted as comparative sample 1.

[0098] Comparative Example 2

[0099] Add 100 g of natural rubber raw rubber and 40 g of carbon black to an internal mixer in sequence for the first mixing. The mixing temperature is 45 °C and the time is 8 minutes to obtain a mixed rubber. Add the mixed rubber and a vulcanizing agent to an open mill for the second mixing at room temperature. Heat-press vulcanize the mixed rubber after the second mixing at 143 °C to obtain a vulcanized rubber, denoted as comparative sample 2.

[0100] Comparative Example 3

[0101] This example provides a method for preparing a cellulose-rubber composite material, including:

[0102] Add 100 g of natural rubber raw rubber, 5 g of micro-nano cellulose reinforcing filler A, and 0.375 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane to a kneader in sequence for the first kneading. The kneading temperature is 45 °C and the time is 8 min to obtain a kneaded rubber. Add the kneaded rubber and a vulcanizing agent to an open mill and conduct the second kneading at room temperature. Heat-press vulcanize the kneaded rubber after the second kneading at 143 °C to obtain a cellulose-rubber composite material, denoted as Comparative Sample 3.

[0103] Comparative Example 4

[0104] This embodiment provides a method for preparing a cellulose-rubber composite material, including:

[0105] Add 100 g of natural rubber raw rubber, 10 g of micro-nano cellulose reinforcing filler A, and 0.75 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane to a kneader in sequence for the first kneading. The kneading temperature is 45 °C and the time is 8 min to obtain a kneaded rubber. Add the kneaded rubber and a vulcanizing agent to an open mill and conduct the second kneading at room temperature. Heat-press vulcanize the kneaded rubber after the second kneading at 143 °C to obtain a cellulose-rubber composite material, denoted as Comparative Sample 4.

[0106] Comparative Example 5

[0107] This embodiment provides a method for preparing a cellulose-rubber composite material, including:

[0108] Add 100 g of natural rubber raw rubber, 20 g of micro-nano cellulose reinforcing filler A, and 1.5 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane to a kneader in sequence for the first kneading. The kneading temperature is 45 °C and the time is 8 min to obtain a kneaded rubber. Add the kneaded rubber and a vulcanizing agent to an open mill and conduct the second kneading at room temperature. Heat-press vulcanize the kneaded rubber after the second kneading at 143 °C to obtain a cellulose-rubber composite material, denoted as Comparative Sample 5.

[0109] The raw material components of Samples 1-4 and Comparative Samples 1-5 prepared in the embodiments of this application are shown in Table 1.

[0110] Table 1 Raw Material Components of Samples 1-4 and Comparative Samples 1-5

[0111]

[0112] Samples 1-4 and Comparative Samples 1-5 were respectively subjected to mechanical property tests, and the test results are shown in Table 2. Among them, the determination standards for tensile strength, elongation at break, and 300% modulus at 500% elongation are ISO 37-2005, the test temperature is room temperature, and the tensile rate is 500 mm / min; the determination standard for tear strength is GB / T 529-2008; the determination standard for heat build-up during fatigue is ISO 4666-3:2016; the rolling resistance (tanδ value at 60 °C under 5% strain and 10 Hz frequency) and wet skid resistance (tanδ value at 0 °C under 0.1% strain and 10 Hz frequency) were measured by DMA.

[0113] Table 2 Mechanical property test results of Samples 1-5 and Comparative Samples 1-5

[0114]

[0115] As can be seen from Table 2, Comparative Sample 1 is a vulcanized rubber without an additive, and its mechanical properties are poor; the addition amounts of the cellulose-rubber composite reinforcing agent in Comparative Samples 3-5 are relatively low, and their mechanical properties are also relatively low. Compared with Comparative Sample 2, which is a vulcanized rubber using carbon black as a reinforcing material, the samples 1-5 of the cellulose-rubber composite with a high addition amount prepared in this application have similar tensile strength, elongation at break, 300% modulus at 500% elongation, and tear strength, while the rolling resistance and heat build-up during compression are significantly reduced, and the wet skid resistance is significantly improved.

[0116] Among them, compared with Comparative Sample 2, the rolling resistance of Sample 1 is significantly reduced, with a reduction rate of up to 29%; the wet skid resistance is significantly improved, with an increase of 88%. Compared with Comparative Sample 2, the heat build-up during compression of Sample 2 is significantly reduced, with a reduction rate of up to 41%.

[0117] The DMA curves of Samples 1-4 and Comparative Sample 2 are as Figure 1 shown. From Figure 1 the loss factor at 60 °C of the curve, it can be seen that compared with Comparative Sample 2, after high addition amounts of the micro-nano cellulose reinforcing filler of this application are filled in natural rubber or equivalently replace carbon black to fill natural rubber, the rolling resistance of the rubber composite can be reduced.

[0118] In Sample 2, 40 parts of the micro-nano cellulose reinforcing filler were filled in the rubber sample, and its scanning electron microscope image is as Figure 2 shown. From Figure 2 it can be seen that the micro-nano cellulose reinforcing filler of this application is uniformly distributed in the rubber matrix with good dispersibility; its size is about 2 microns.

[0119] In Sample 3, 20 parts of the micro-nano cellulose reinforcing filler were equivalently replaced with carbon black in the rubber sample, and its scanning electron microscope image is as Figure 3 shown. From Figure 3It can be seen that after the micro-nano cellulose reinforcing filler is compounded with carbon black, it can be further peeled into smaller nano-cellulose sheets during the processing, with a size of 300-600 nm, making it have balanced comprehensive properties.

[0120] The transverse and longitudinal tensile mechanical properties of Sample 5 were tested, and the results are shown in Table 3. The transverse and longitudinal tensile curves are as Figure 4 shown.

[0121] Table 3 Transverse and longitudinal tensile mechanical property data of Sample 5

[0122]

[0123] From Figure 4 and Table 3, it can be seen that the micro-nano cellulose reinforcing filler prepared in this application has low anisotropy, can overcome the disadvantages of the fiber aspect ratio when reinforcing natural rubber, making the strength difference between its transverse and longitudinal directions relatively low. Therefore, it can replace the traditional non-renewable filler carbon black in fields such as tire products, which has important social significance and application value.

[0124] Although this application has been described in detail in this specification with general descriptions and specific implementation examples, based on this application, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of this application all fall within the scope protected by this application.

Claims

1. A method for preparing a micro-nano cellulose reinforcing filler, characterized in that: include: The cellulose is oxidized to obtain modified cellulose having carboxyl functional groups; The modified cellulose is subjected to an ester exchange reaction with an unsaturated ester compound to obtain a micro-nano cellulose reinforcing filler.

2. The preparation method according to claim 1, characterized in that: The oxidation degree of the modified cellulose is 1-12%.

3. The preparation method according to claim 1, characterized in that: The transesterification reaction is a mechanical transesterification reaction, which includes: subjecting the modified cellulose and the unsaturated ester compound to ball milling or high-speed pulverization, so that the carboxyl functional groups of the modified cellulose and the unsaturated ester compound undergo transesterification reaction; The mass ratio of the modified cellulose to the unsaturated ester compound is 100:(1-30), and the temperature of the transesterification reaction is 25-90°C.

4. The preparation method according to claim 1, characterized in that: The cellulose comprises at least one of microcrystalline cellulose, nanocellulose microcrystals, nanocellulose fibers, and nanocellulose sheets; and / or, The unsaturated ester compound includes one, two or three ester groups.

5. The preparation method according to claim 4, characterized in that: The unsaturated ester compound includes at least one of methyl acrylate, ethyl acrylate, ethyl sorbate, methyl coconut oleate, arachidonic acid diglyceride, myristic acid diglyceride, docosahexaenoic acid diglyceride, oleic acid diglyceride, 1,3-octadecenoic acid diglyceride, oleic acid triglyceride, linoleic acid triglyceride or linolenic acid triglyceride.

6. The micro-nano cellulose reinforcing filler prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the micro-nano cellulose reinforcing filler according to claim 6 in rubber composite materials.

8. A method for preparing a cellulose-rubber composite material, characterized in that: include: Adding raw rubber, reinforcing filler and silane coupling agent into an internal mixer for first mixing to obtain a mixed rubber; Adding the mixed rubber and the vulcanizing agent into an open mill, and performing a second mixing at room temperature; hot pressing and vulcanizing the mixed rubber after the second mixing to obtain a cellulose-rubber composite material; The reinforcing filler is the micro-nano cellulose reinforcing filler according to claim 6, or a mixture of the micro-nano cellulose reinforcing filler according to claim 6 and carbon black.

9. The preparation method according to claim 8, characterized in that: The mass ratio of the raw rubber to the reinforcing filler is 100:(30-50); and / or, The amount of the silane coupling agent is 0% to 15wt% of the amount of the reinforcing filler; and / or, The first mixing temperature is 25-80°C and the time is 5-10 minutes; and / or, The temperature of the hot press vulcanization is 143°C.

10. The cellulose-rubber composite material prepared by the preparation method according to claim 8 or 9.

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