A hydrophobic sisal cellulose microcrystal reinforced natural rubber and its preparation method

Abstract

The present invention discloses a hydrophobic sisal cellulose microcrystal reinforced natural rubber and its preparation method. The surface of sisal cellulose microcrystals (MCC) is modified by amino groups using the silane coupling agent KH550. The synthesized poly (dodecahydroxystearic acid) (PHS) is subjected to amidation reaction with the surface amino-functionalized sisal cellulose microcrystals (KH550-g-MCC) to obtain hydrophobic poly (dodecahydroxystearic acid) grafted sisal cellulose microcrystals (PHS-g-MCC), and the contact angle is 115-120°. The natural rubber composite material is reinforced and modified by PHS-g-MCC, and its tensile strength is 25.0-26.0 MPa, the 100% modulus at elongation is 1.40-1.50 MPa, and the Shore A hardness is 56-59.

Description

Technical Field

[0001] The present invention belongs to the field of natural polymers, and particularly relates to a hydrophobic sisal cellulose microcrystal reinforced natural rubber and a preparation method thereof. Background Art

[0002] Natural rubber (NR) is a natural polymer compound mainly composed of cis-1,4-polyisoprene, and has excellent resilience, tensile strength, elongation at break, abrasion resistance, and its tear and compression set performance are superior to most synthetic rubbers. Natural rubber is widely used in the fields of construction, transportation, aerospace, electronics, and military. In the process of preparing rubber products, rigid fillers are usually added to increase its strength, such as carbon black, silica, fiber, clay, etc. Filling the filler into the rubber can not only improve the rubber properties, but also reduce costs and meet the actual use requirements. In addition, due to the increasing shortage of petrochemical resources, growing environmental problems and sustainable development requirements, and more because plant fibers have the characteristics of rich sources, high crystallinity, excellent mechanical properties and biodegradability, plant fibers as natural rubber composite reinforcements have attracted much attention from researchers.

[0003] Sisal, also known as pineapple hemp, belongs to the genus Agave in the family Agavaceae. It is a perennial tropical hard-leaf fiber crop. Originating from Mexico, it is now mainly cultivated in Africa, Latin America, Asia and other places. It is the hard fiber with the largest consumption and the widest range of use in the world today. Sisal fiber has the characteristics of being tough, wear-resistant, resistant to salt and alkali, and corrosion-resistant. It is widely used in various industries such as transportation, fishery, petroleum, and metallurgy. Moreover, it is also used in filling and reinforcing resin-based composites. Like other plant celluloses, there are many hydrophilic polar hydroxyl groups (-OH) in the molecular structure of sisal cellulose, which makes the interfacial compatibility between sisal cellulose and non-polar resin matrix poor, thus affecting the performance of the composite material. Therefore, in order to improve the interfacial compatibility between sisal cellulose and non-polar resin matrix, it is necessary to carry out hydrophobic modification on the surface of sisal cellulose to expand its application scope. Regarding the hydrophobic modification of cellulose surface, there have been many literature reports. For example, CN107365423A introduces a method of using chemical vapor deposition to prepare hydrophobic modified cellulose materials by in-situ one-step reaction of organosilane reagents (hexamethyldisilazane, methyltrimethoxysilane, etc.). The literature (Hu Qifei, Tianjin University of Technology, 2018) uses ramie fiber as raw material and octadecyltrichlorosilane as modifier to graft long hydrophobic chains onto the fiber surface to obtain hydrophobic and lipophilic ramie. The literature (ACS Applied Materials & Interfaces, 2016, 8: 24893) grafts poly (lauryl methacrylate)-block-poly (2-hydroxyethyl methacrylate) onto the surface of cellulose nanofibers to prepare hydrophobic nanocellulose. From the above literature, the preparation methods of the reported cellulose hydrophobic materials all have defects such as cumbersome steps, complex post-treatment processes, and high preparation costs, making it difficult to achieve large-scale production. Summary of the Invention

[0004] The object of the present invention is to provide a hydrophobic sisal cellulose microcrystal reinforced natural rubber and its preparation method. Specifically, in the present invention, dodecahydroxystearic acid (12-HSA) is polymerized by polycondensation reaction to form a poly dodecahydroxystearic acid (PHS) oligomer. The surface of sisal cellulose microcrystals (MCC) is modified by amination using a silane coupling agent KH550. Then, PHS and the surface-aminated sisal cellulose microcrystals are subjected to amidation reaction to obtain poly dodecahydroxystearic acid grafted sisal cellulose microcrystals (PHS-g-MCC). Since the molecular structure of PHS-g-MCC contains many non-polar fatty long chains, the sisal cellulose microcrystals are endowed with hydrophobic properties. In addition, the non-polar fatty long chains on PHS-g-MCC can physically entangle with the molecular chains of natural rubber, improving the interfacial compatibility between the sisal cellulose microcrystals and natural rubber, and enabling PHS-g-MCC to have good dispersibility in the natural rubber matrix. At the same time, the long rod-shaped sisal cellulose microcrystals have a reinforcing effect on rubber and can be used to replace part of the inorganic fillers for preparing high-performance green environmental protection natural rubber composites.

[0005] A hydrophobic sisal cellulose microcrystal reinforced natural rubber and its preparation method according to the present invention mainly include the following components:

[0006] 90 - 100 g of natural rubber, 5 - 10 g of PHS-g-MCC, 20 - 30 g of silica (150 mesh), 2 - 3 g of stearic acid, 4 - 6 g of zinc oxide, 1 - 2 g of antioxidant, 0.5 - 1 g of accelerator, 1 - 3 g of insoluble sulfur. The preparation method of the PHS-g-MCC reinforced natural rubber composite includes the following steps:

[0007] 1. Preparation method of sisal cellulose microcrystals (MCC)

[0008] Take 100 g of sisal fibers and cut them into lengths of 3 - 5 mm, add them to a mixed solution containing 30 - 40 g of sodium sulfate, 100 - 120 ml of 5wt% sodium hydroxide, and 500 ml of deionized water. Stir at 100 °C for 4 - 5 hours, then filter. The filter cake is washed with deionized water multiple times until neutral. Then, the filter cake is placed in 500 ml of deionized water, 15 - 20 ml of glacial acetic acid, and 13 - 15 g of sodium hypochlorite solution, heated to 85 °C and stirred for 3 - 4 hours, then cooled, filtered, and dried to obtain white powdery sisal cellulose microcrystals (MCC).

[0009] 2. Preparation method of poly dodecahydroxystearic acid grafted sisal cellulose microcrystals (PHS-g-MCC)

[0010] (1) Place 60 - 80 g of dodecahydroxystearic acid (12 - HSA) in a three - necked flask, heat it to 100 - 110 °C to melt it. After complete melting, add 0.75 - 1.0 g of p - toluenesulfonic acid. Stir and raise the temperature of the system to 130 - 140 °C and continuously evacuate the air. React for 6 - 8 hours under this condition and then discharge the product. Wash the product twice with 100 mL of 75% ethanol solution, and then place it in a vacuum drying oven at 60 - 80 °C to dry to constant weight, and then brown viscous liquid poly - dodecahydroxystearic acid (PHS) can be obtained.

[0011] (2) Prepare a 5 - 10% ethanol aqueous solution of 5 - 8 g of γ - aminopropyltriethoxysilane (KH550) and hydrolyze it at room temperature for 1 - 2 hours. After hydrolysis, place it in a three - necked flask with 3 - 6 g of MCC and react at 70 - 80 °C for 6 - 8 hours. After the reaction is completed, cool, filter by suction, wash, and place it in a vacuum drying oven at 60 - 80 °C to dry to constant weight, and then light yellow amino - modified sisal cellulose microcrystals (KH550 - g - MCC) powder can be obtained.

[0012] (3) Take 60 - 100 mL of xylene, 10 - 15 g of PHS, and 3 - 6 g of KH550 - g - MCC and add them to a 250 mL three - necked flask. Add 0.3 - 0.4 g of triphenylphosphine and 0.5 - 2.0 mL of pyridine as catalysts. Heat to 130 - 140 °C under N2 protection and react for 6 - 8 hours. After the reaction is completed, filter the product by suction, wash it repeatedly with xylene to remove unreacted substances, and then extract the product with anhydrous ethanol to remove residual xylene. Place the product in a vacuum drying oven at 60 - 80 °C to dry to constant weight, and then dark yellow poly - dodecahydroxystearic acid grafted sisal cellulose microcrystals (PHS - g - MCC) powder can be obtained.

[0013] 3. Preparation method of PHS - g - MCC / natural rubber composite

[0014] Add 90 - 100 g of natural rubber to a two - roll mill, plasticate for 5 - 7 minutes, and then add 4 - 6 g of zinc oxide, 2 - 3 g of stearic acid, 1 - 2 g of antioxidant, 5 - 10 g of PHS - g - MCC, 20 - 30 g of silica (150 mesh), 0.5 - 1 g of accelerator, and 1 - 3 g of insoluble sulfur in sequence; cut the mixed rubber on both sides 6 - 10 times each, then alternately roll and make triangular packages, and take out the sheet; after 24 hours, test the vulcanization characteristics of the rubber compound to obtain the optimum vulcanization time t 90 , and after hot - forming the mixed rubber by flat - plate vulcanization, the PHS - g - MCC / natural rubber composite can be obtained.

[0015] The accelerator described in the present invention may be tetra methyl thiuram disulfide (accelerator TMTD), or N-cyclohexyl-2-benzothiazole sulfenamide (accelerator CZ), or dibenzothiazole disulfide (accelerator DM), preferably tetra methyl thiuram disulfide (accelerator TMTD).

[0016] The process conditions for the rubber vulcanization and molding in the present invention are as follows: the temperature is 140 - 145 °C, the pressure is 5 - 10 MPa, and the heat preservation time is 7 - 10 minutes.

[0017] For the hydrophobic PHS-g-MCC prepared by the present invention, the contact angle is 115 - 120°; the tensile strength of the PHS-g-MCC / natural rubber composite is 25.0 - 26.0 MPa, the 100% modulus is 1.40 - 1.50 MPa, and the Shore A hardness is 56 - 59. Compared with the mechanical properties of the natural rubber composite without adding PHS-g-MCC (tensile strength: 25.4 - 25.8 MPa, 100% modulus: 1.01 - 1.11 MPa), PHS-g-MCC can enhance the modulus and Shore A hardness of the natural rubber composite.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. The molecular structure of the prepared PHS-g-MCC contains non-polar flexible long chains, and these flexible long chains can have good entanglement with the natural rubber molecular chains, which is beneficial to the dispersion of PHS-g-MCC in the natural rubber matrix and improves the mechanical properties of the composite material.

[0020] 2. PHS-g-MCC is prepared by surface amination of sisal cellulose microcrystals with silane coupling agent KH550 and then amidation reaction with poly dodecahydroxy stearic acid. The reaction operation is simple, and the raw materials used are inexpensive, which is beneficial to large-scale production. Description of the Drawings

[0021] To further elaborate on the content of the present invention, the inventor provides an attached drawing for Example 1:

[0022] Figure 1 It is the preparation technical route diagram of PHS-g-MCC;

[0023] Figure 2 It is the infrared spectrogram of 12-HSA, PHS, MCC, KH550-g-MCC, and PHS-g-MCC;

[0024] Figure 3 It is the digital photos of the appearances of 12-HSA, PHS, MCC, KH550-g-MCC, and PHS-g-MCC products;

[0025] Figure 4 Photographs of the water dispersibility and contact angles of MCC, KH550-g-MCC, and PHS-g-MCC products. Detailed implementation modes

[0026] The present invention will be further described in detail below through examples. These examples are only used to illustrate the present invention and do not limit the scope of the present invention.

[0027] Example 1

[0028] 1. Preparation of microcrystalline sisal cellulose (MCC)

[0029] Take 100 grams of sisal fiber and cut it into lengths of 3 - 5 mm, add it to a mixed solution containing 30 grams of sodium sulfate, 100 ml of 5wt% sodium hydroxide, and 500 ml of deionized water. Stir at 100 °C for 5 hours, then filter. Wash the filter cake with deionized water multiple times until neutral. Then place the filter cake in 500 ml of deionized water, 15 ml of glacial acetic acid, and 15 grams of sodium hypochlorite solution. Heat to 85 °C and stir for 3 hours, then cool, filter, and dry to obtain white powdery microcrystalline sisal cellulose (MCC).

[0030] 2. Preparation of poly (dodecahydroxystearic acid)-grafted microcrystalline sisal cellulose (PHS-g-MCC)

[0031] (1) Place 60 grams of dodecahydroxystearic acid (12-HSA) in a three-necked flask, heat to 110 °C to melt it. After complete melting, add 0.75 grams of p-toluenesulfonic acid. Stir and raise the temperature of the system to 130 °C and continuously evacuate. React for 6 hours under this condition and then discharge the product. Wash the product with 100 ml of 75% ethanol solution twice, and then place it in a vacuum drying oven at 60 °C to dry to constant weight to obtain a brown viscous liquid poly (dodecahydroxystearic acid) (PHS).

[0032] (2) Prepare a 5% ethanol aqueous solution of 5 grams of γ-aminopropyltriethoxysilane (KH550) and hydrolyze it at room temperature for 1 hour. After hydrolysis, place it in a three-necked flask with 3 grams of MCC and react at 70 °C for 6 hours. After the reaction, cool, filter, wash, and place it in a vacuum drying oven at 60 °C to dry to constant weight to obtain light yellow amino-functionalized microcrystalline sisal cellulose (KH550-g-MCC) powder.

[0033] (3) Add 60 mL of xylene, 10 g of PHS, and 3 g of KH550-g-MCC into a 250 mL three-necked flask, and add 0.3 g of triphenylphosphine and 0.5 mL of pyridine as catalysts thereto. Heat to 130 °C under N2 protection and react for 6 hours. After the reaction is completed, filter the product, wash it repeatedly with xylene to remove unreacted substances, and then extract the product with absolute ethanol to remove residual xylene. Place the product in a vacuum drying oven at 60 °C and dry it to constant weight to obtain dark yellow poly(dodecahydroxystearic acid)-grafted sisal cellulose microcrystal (PHS-g-MCC) powder.

[0034] 3. Preparation method of PHS-g-MCC / natural rubber composite

[0035] Add 90 g of natural rubber to a two-roll mill, plasticize for 5 minutes, and sequentially add 4 g of zinc oxide, 2 g of stearic acid, 1 g of antioxidant, 5 g of PHS-g-MCC, 20 g of silica (150 mesh), 0.5 g of accelerator, and 1 g of insoluble sulfur; cut the mixed rubber 6 times on each side, then alternately roll and make triangular bales, and take out the sheet; test the vulcanization characteristics of the rubber compound 24 hours later to obtain the optimum vulcanization time t 90 , and after hot forming the mixed rubber by flat vulcanization, the PHS-g-MCC / natural rubber composite can be obtained. The tensile strength of the obtained composite is 25.23 MPa, the 100% modulus is 1.01 MPa, and the Shore A hardness is 56.

[0036] Example 2

[0037] 1. Preparation of sisal cellulose microcrystal (MCC)

[0038] Take 100 g of sisal fiber and cut it into lengths of 3 - 5 mm, add it to a mixed solution containing 30 g of sodium sulfate, 100 mL of 5 wt% sodium hydroxide, and 500 mL of deionized water, stir at 100 °C for 5 hours, then filter, and wash the filter cake with deionized water multiple times until neutral; then place the filter cake in 500 mL of deionized water, 15 mL of glacial acetic acid, and 15 g of sodium hypochlorite solution, heat to 85 °C and stir for 3 hours, then cool, filter, and dry to obtain white powdery sisal cellulose microcrystal (MCC).

[0039] 2. Preparation of poly(dodecahydroxystearic acid)-grafted sisal cellulose microcrystal (PHS-g-MCC)

[0040] (1) Place 60 g of dodecahydroxystearic acid (12-HSA) in a three-necked flask, heat it to 110 °C to melt it, and after complete melting, add 0.75 g of p-toluenesulfonic acid. Stir and raise the temperature of the system to 130 °C and continuously evacuate. After reacting under these conditions for 6 hours, discharge the product. Wash the product twice with 100 mL of 75% ethanol solution, and then place it in a vacuum drying oven at 60 °C and dry it to constant weight to obtain a brown viscous liquid, poly dodecahydroxystearic acid (PHS).

[0041] (2) Prepare an 8% ethanol aqueous solution of 6 g of γ-aminopropyltriethoxysilane (KH550) and hydrolyze it at room temperature for 2 hours. After hydrolysis, place it in a three-necked flask with 4 g of MCC and react at 70 °C for 6 hours. After the reaction is completed, cool, filter by suction, wash, and place it in a vacuum drying oven at 60 °C and dry it to constant weight to obtain a light yellow powdered product of amino-functionalized sisal cellulose microcrystals (KH550-g-MCC).

[0042] (3) Take 80 mL of xylene, 12 g of PHS, and 4 g of KH550-g-MCC and add them to a 250 mL three-necked flask. Add 0.3 g of triphenylphosphine and 1.0 mL of pyridine as catalysts, heat to 130 °C under N2 protection and react for 6 hours. After the reaction is completed, filter the product by suction, wash it repeatedly with xylene to remove unreacted substances, and then extract the product with anhydrous ethanol to remove residual xylene. Place the product in a vacuum drying oven at 60 °C and dry it to constant weight to obtain a dark yellow powdered product of poly dodecahydroxystearic acid grafted sisal cellulose microcrystals (PHS-g-MCC).

[0043] 3. Preparation method of PHS-g-MCC / natural rubber composite

[0044] Add 95 g of natural rubber to a two-roll mill, plasticate for 6 minutes, and successively add 5 g of zinc oxide, 2 g of stearic acid, 1 g of antioxidant, 7 g of PHS-g-MCC, 25 g of silica (150 mesh), 0.5 g of accelerator, and 2 g of insoluble sulfur; cut the mixed rubber 6 times on each side, then alternately roll and make triangular bales, and take out the sheet; after 24 hours, test the vulcanization characteristics of the rubber compound to obtain the optimum vulcanization time t 90 , and after hot forming the mixed rubber by flat vulcanization, a PHS-g-MCC / natural rubber composite can be obtained. The tensile strength of the prepared composite is 25.52 MPa, the 100% modulus is 1.53 MPa, and the Shore A hardness is 58.

[0045] Example 3

[0046] 1. Preparation of sisal cellulose microcrystals (MCC)

[0047] Take 100 g of sisal fiber and cut it into lengths of 3 - 5 mm. Add it to a mixed solution containing 30 g of sodium sulfate, 100 mL of 5 wt% sodium hydroxide, and 500 mL of deionized water. Stir at 100 °C for 5 hours, then filter. Wash the filter cake with deionized water multiple times until neutral. Then place the filter cake in 500 mL of deionized water, 15 mL of glacial acetic acid, and 15 g of sodium hypochlorite solution. Heat to 85 °C and stir for 3 hours, then cool, filter, and dry to obtain white powdery sisal cellulose microcrystals (MCC).

[0048] 2. Preparation of poly (dodecahydroxystearic acid) grafted sisal cellulose microcrystals (PHS-g-MCC)

[0049] (1) Place 60 g of dodecahydroxystearic acid (12-HSA) in a three-necked flask, heat to 110 °C to melt it. After complete melting, add 0.75 g of p-toluenesulfonic acid. Stir and raise the temperature of the system to 130 °C and continuously evacuate. After reacting for 6 hours under this condition, discharge the product. Wash the product 2 times with 100 mL of 75% ethanol solution, and then place it in a vacuum drying oven at 60 °C to dry to constant weight to obtain a brown viscous liquid poly (dodecahydroxystearic acid) (PHS).

[0050] (2) Prepare a 10% ethanol aqueous solution of 8 g of γ-aminopropyltriethoxysilane (KH550) and hydrolyze it at room temperature for 2 hours. After hydrolysis, place it in a three-necked flask with 6 g of MCC and react at 70 °C for 8 hours. After the reaction is completed, cool, filter, wash, and place it in a vacuum drying oven at 60 °C to dry to constant weight to obtain light yellow amino-functionalized sisal cellulose microcrystals (KH550-g-MCC) powder.

[0051] (3) Take 100 mL of xylene, 15 g of PHS, and 6 g of KH550-g-MCC and add them to a 250 mL three-necked flask. Add 0.4 g of triphenylphosphine and 1.5 mL of pyridine as catalysts. Heat to 130 °C under N2 protection and react for 8 hours. After the reaction is completed, filter the product, wash it repeatedly with xylene to remove unreacted substances, and then extract the product with anhydrous ethanol to remove residual xylene. Place the product in a vacuum drying oven at 60 °C to dry to constant weight to obtain dark yellow poly (dodecahydroxystearic acid) grafted sisal cellulose microcrystals (PHS-g-MCC) powder.

[0052] 3. Preparation method of PHS-g-MCC / natural rubber composite

[0053] Add 100 g of natural rubber into a two-roll mill, plasticize for 7 minutes, and then add 6 g of zinc oxide, 3 g of stearic acid, 2 g of antioxidant, 10 g of PHS-g-MCC, 30 g of white carbon black (150 mesh), 1 g of accelerator, and 3 g of insoluble sulfur in sequence; cut the compound 8 times on each side, then alternately roll and make triangle packages, and take out the sheet; after 24 hours, test the vulcanization characteristics of the compound to obtain the optimum vulcanization time t 90 , and after hot forming the compound by flat vulcanization, the PHS-g-MCC / natural rubber composite material can be obtained. The tensile strength of the obtained composite material is 21.56 MPa, the 100% modulus is 1.67 MPa, and the Shore A hardness is 59.

[0054] The above is only a more preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be regarded as the protection scope of the technical solution of the present invention.

Claims

1. A preparation method of hydrophobic sisal cellulose microcrystal reinforced natural rubber, characterized in that, The specific steps are as follows: (1) Preparation method of sisal cellulose microcrystals (MCC) Take 100 g of sisal fibers and cut them into lengths of 3 - 5 mm. Add them to a mixed solution containing 30 - 40 g of sodium sulfate, 100 - 120 mL of 5 wt% sodium hydroxide, and 500 mL of deionized water. Stir at 100 °C for 4 - 5 hours, then filter. Wash the filter cake with deionized water multiple times until neutral. Then place the filter cake in 500 mL of deionized water, 15 - 20 mL of glacial acetic acid, and 13 - 15 g of sodium hypochlorite solution. Heat to 85 °C and stir for 3 - 4 hours, then cool, filter, and dry to obtain white powdery sisal cellulose microcrystals (MCC). (2) Preparation method of poly (dodecahydroxystearic acid) grafted sisal cellulose microcrystals (PHS-g-MCC) ① Place 60 - 80 g of dodecahydroxystearic acid (12-HSA) in a three-necked flask, heat to 100 - 110 °C to melt it. After complete melting, add 0.75 - 1.0 g of p-toluenesulfonic acid. Stir and raise the temperature of the system to 130 - 140 °C and continuously evacuate. React under these conditions for 6 - 8 hours and then discharge. Wash the product twice with 100 mL of 75% ethanol solution, and then place it in a vacuum drying oven at 60 - 80 °C to dry to constant weight to obtain a brown viscous liquid poly (dodecahydroxystearic acid) (PHS). ② Prepare a 5 - 10% ethanol aqueous solution of 5 - 8 g of γ-aminopropyltriethoxysilane (KH550) and hydrolyze it at room temperature for 1 - 2 hours. After hydrolysis, place it in a three-necked flask with 3 - 6 g of MCC and react at 70 - 80 °C for 6 - 8 hours. After the reaction, cool, filter, wash, and place it in a vacuum drying oven at 60 - 80 °C to dry to constant weight to obtain light yellow amino-functionalized sisal cellulose microcrystals (KH550-g-MCC) powder. ③ Take 60 - 100 mL of xylene, 10 - 15 g of PHS, and 3 - 6 g of KH550-g-MCC and add them to a 250 mL three-necked flask. Add 0.3 - 0.4 g of triphenylphosphine and 0.5 - 2.0 mL of pyridine as catalysts. Heat to 130 - 140 °C under N2 protection and react for 6 - 8 hours. After the reaction, filter the product, wash it repeatedly with xylene to remove unreacted substances, and then extract the product with anhydrous ethanol to remove residual xylene. Place the product in a vacuum drying oven at 60 - 80 °C to dry to constant weight to obtain dark yellow poly (dodecahydroxystearic acid) grafted sisal cellulose microcrystals (PHS-g-MCC) powder. (3) Preparation method of PHS-g-MCC / natural rubber composite Add 90 - 100 g of natural rubber into a two-roll mill, plasticize for 5 - 7 minutes, and then add 4 - 6 g of zinc oxide, 2 - 3 g of stearic acid, 1 - 2 g of antioxidant, 5 - 10 g of PHS-g-MCC, 20 - 30 g of white carbon black, 0.5 - 1 g of accelerator, and 1 - 3 g of insoluble sulfur in sequence; cut the mixed rubber 6 - 10 times on both the left and right sides, then alternately roll and make triangular packages, and take out the sheet; after 24 hours, test the vulcanization characteristics of the rubber compound to obtain the optimum vulcanization time t90, and after hot forming the mixed rubber by flat vulcanization, the PHS-g-MCC / natural rubber composite material is obtained. The chemical structural formula of the said PHS-g-MCC is: 。 2. The preparation method according to claim 1, characterized in that, The antioxidant in the said step (3) includes tetramethylthiuram disulfide (accelerator TMTD), or N-cyclohexyl-2-benzothiazole sulfenamide (accelerator CZ), or dibenzothiazole disulfide (accelerator DM).

3. The preparation method according to claim 1, characterized in that, The accelerator in the said step (3) includes tetramethylthiuram disulfide (accelerator TMTD), or N-cyclohexyl-2-benzothiazole sulfenamide (accelerator CZ), or dibenzothiazole disulfide (accelerator DM).

4. The preparation method of hydrophobic sisal cellulose microcrystal reinforced natural rubber according to any one of claims 1-3, and hydrophobic sisal cellulose microcrystal reinforced natural rubber is prepared.

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