CN107474343B - One-pot method for preparing ascidian nanocrystalline cellulose/rubber nanocomposites - Google Patents

Abstract

The invention discloses a method for preparing ascidian nano-microcrystalline cellulose/rubber nano composite material by one-pot method. In the method, the natural latex is diluted at room temperature, and the emulsifier is slowly added dropwise; the ascidian nano-microcrystalline cellulose suspension is blended with the obtained emulsified natural latex to obtain a premix; formic acid is slowly added dropwise to the premix , and then slowly add hydrogen peroxide to react; after the reaction, adjust the pH value to 6-8, solidify, rinse, dehydrate, and dry to obtain ascidian nanocrystalline cellulose/rubber mixture; the obtained mixture and vulcanizing agent are put on the mill. After kneading, vulcanization molding after standing. The invention overcomes the problem of poor strength due to only physical interaction between the two interfaces in the prior art, and the prepared rubber nano-composite material has excellent properties such as high strength, high modulus, high wear resistance, etc. Give full play to the reinforcing effect of nanocrystalline cellulose.

Description

One-pot method for preparing ascidian nanocrystalline cellulose/rubber nanocomposites

technical field

The invention belongs to the technical field of rubber, and in particular relates to a one-pot process for preparing ascidian nano-microcrystalline cellulose/rubber nano-composite material.

Background technique:

Carbon black and silica are the most commonly used reinforcing fillers in the rubber industry, but they have unavoidable defects such as large pollution, high energy consumption, and dependence on petroleum resources. Therefore, it is of great significance to develop sustainable green reinforcing fillers.

Cellulose is a polysaccharide biomaterial that exists widely in nature and is very abundant. After a series of treatments, rod-shaped nanocrystalline cellulose (CNs) can be obtained, which has the advantages of large specific surface area, high strength, wide source, and renewable. It can be used as a new type of green reinforcing filler for rubber and as carbon Complementary or partial replacements for traditional reinforcing fillers such as black and silica can bring enormous economic and environmental benefits to the rubber industry. Chinese invention patent CN102002173B discloses a method of using nanocrystalline cellulose and white carbon black to reinforce rubber. First, the nanocrystalline cellulose suspension is mixed with natural latex, and then the white carbon black and modified It mainly relies on modifiers such as silane or titanate coupling agent, zinc (magnesium) methacrylate, and rubber adhesives to improve the interfacial interaction between CNs and silica and natural rubber;

Chinese invention patent application CN104530504 A discloses a preparation method of a nano-microcrystalline cellulose rubber composite material based on waste cotton material. First, CNs is reacted with a modifier, then mixed with natural latex, and finally white is added through an open mill. Carbon black is obtained, which also relies on modifiers such as coupling agents to improve the interfacial interaction between CNs and silica and natural rubber;

Chinese invention patent application CN105419002 A discloses a preparation method of bagasse nanocellulose and its rubber composite material, firstly adding (silane, titanate coupling agent) and methylene white system into the nanocellulose suspension, and then mixing with The natural rubber latex is mixed, and finally it is obtained by mixing silica with an open mill. This material also relies on a coupling agent to increase the combination of CNs and natural rubber.

It can be seen from the above that the rubber nanocomposites prepared above are obtained by simply modifying CNs with a coupling agent and then mixing them with natural latex. There is only physical interaction between filler and rubber in the prepared composite material, and the high reinforcing effect of nanocrystalline cellulose cannot be fully reflected. At the same time, the above-mentioned prior art only partially replaces carbon black or white carbon black with nanocrystalline cellulose, and the amount of high-polluting fillers such as carbon black and white carbon black is still relatively large, which cannot fundamentally solve the high pollution and high energy existing in the current market. consumption and high density. In addition, the above-mentioned nanocrystalline cellulose used as rubber reinforcing fillers are all derived from terrestrial plants, such as cotton, wood, hemp, etc., and these resources also have important use value in other aspects, which may lead to Among them, the cost of extracting nanocrystalline cellulose should be increased.

Invention content:

The object of the present invention is to provide a more efficient, economical and environmentally friendly nano-microcrystalline cellulose/rubber nano-composite material and its preparation method, which can overcome the current simple physical The problem of weak interfacial bonding between rubber and nanocrystalline cellulose in the mixing technology makes nanocrystalline cellulose play a more excellent reinforcing effect.

The inventors have noticed that cellulose can be extracted from tunicates, tunicates, which are present in marine resources. Ascidians sometimes attach to the bottom of ships, affecting their speed and adversely affecting the aquaculture industry. When the sea squirt is used as food, its tunic is thrown away as garbage, and cellulose mainly exists in its tunic, so how to "turn waste into treasure" has important economic and environmental benefits.

In the rubber/nano-microcrystalline cellulose composite materials usually prepared by physical blending method, there is only a simple physical interaction between the rubber and the nano-microcrystalline cellulose, and the interface bonding force is weak, and it is easy to peel off when subjected to external force. , resulting in damage. If the preparation process is improved, the interfacial chemical combination of nanocrystalline cellulose and rubber is realized, and its dispersion in rubber is improved, it is possible to fully exert the high reinforcing effect of nanocrystalline cellulose.

The object of the present invention is achieved through the following technical solutions:

A one-pot method for preparing ascidian nanocrystalline cellulose/rubber nanocomposite, comprising the following steps:

1) Dilute the natural latex at room temperature, slowly add the emulsifier dropwise, and stir to stabilize for 1 to 3 hours;

2) blending the ascidian nano-microcrystalline cellulose suspension with the emulsified natural latex obtained in step 1) to obtain a premix; wherein the mass ratio of the ascidian nano-microcrystalline cellulose to the natural latex is 3:100～30: 100;

3) Slowly add formic acid dropwise to the premix to adjust the pH to 2 to 4, then slowly add hydrogen peroxide to react; the molar ratio of hydrogen peroxide to natural rubber is 3:1 to 1:1;

4) after the reaction is completed, the pH value of the mixed solution is adjusted to 6～8 with ammonia water, solidified, rinsed, dehydrated and dried to obtain the ascidian nanocrystalline cellulose/rubber mixture;

5) The mixture obtained in step 4) and the vulcanizing agent are kneaded on an open mill, placed and vulcanized to form, to obtain ascidian nanocrystalline cellulose/rubber nanocomposite.

In order to further achieve the purpose of the present invention, preferably, the ascidian nano-microcrystalline cellulose is extracted from ascidian or ascidian tunicate with a diameter of 10 to 20 nm, a length of 500 nm to 2 μm, and an aspect ratio of 70- 80's rod-like crystalline product.

Preferably, the mass concentration of the natural latex after dilution in step 1) is 20-40%, preferably 30%.

Preferably, the emulsifier is polyoxyethylene laurate or polyethylene glycol octyl phenyl ether. The dosage of the emulsifier is 5-10%, preferably 8%, of the dry rubber weight in the latex.

Preferably, the preparation method of the ascidian nanocrystalline cellulose suspension is as follows: soaking and washing the ascidian and dissecting to leave the capsule; soaking the capsule in strong alkali at 40-60°C for 12-24 hours to remove The proteins and lipids contained in it; and then at 50-90 ℃, the taucus from which the proteins and lipids were removed was reacted in a bleaching solution made of glacial acetic acid and sodium hypochlorite for 6-12 hours, and repeated 2-6 times. The previous bleaching solution needs to be replaced every time until the capsules turn white; the bleached powder cellulose crystals are dried in a blast drying oven at 30-60 °C, and pulverized to micron or millimeter scale ; The pulverized powdered cellulose crystals are subjected to acid hydrolysis with sulfuric acid with a concentration of 55-65 wt%, the acid hydrolysis temperature is 40-60 ° C, and the time is 0.5-5 h. After the reaction is completed, a large amount of deionized water is added to dilute the solution and reduce the temperature. to terminate the reaction; then the obtained mixed solution was centrifuged at high speed, the supernatant was discarded, repeated 3 times, and finally the medium and low speed centrifugation was carried out to obtain the upper layer suspension, which was the ascidian nanocrystalline cellulose suspension, and then put it into Dialysis is carried out in a dialysis bag to make the suspension neutral or weakly acidic, and finally ultrasonic dispersion is performed for 10-50 min to obtain the ascidian nanocrystalline cellulose suspension.

Preferably, the mass concentration of the hydrogen peroxide is 30%-50%.

Preferably, the reaction temperature is 30-50° C., preferably 30° C., the reaction time is 10-40 h, and magnetic or mechanical stirring is performed during the reaction.

Preferably, the coagulation is co-flocculation using chemical reagents, and the chemical reagents are one or more of ethanol, formic acid and acetic acid; the rinsing is to repeatedly rinse the coagulated product with tap water until the Neutral.

Preferably, the dehydration is drying with filter paper or vacuum filtration to remove surface moisture.

Preferably, the drying is to use a vacuum drying oven or a blast drying oven with a temperature of 40-60° C. to dry the product to a constant weight.

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

1. The nanocomposite material is prepared by a one-pot process. On the one hand, the epoxidation reagent triggers a natural epoxidation reaction to generate epoxidized natural rubber, and at the same time triggers the oxidation reaction of the hydroxyl group on the surface of the ascidian nanocrystalline cellulose to generate an aldehyde group, Carboxyl and other groups; in the reaction process, the free epoxidized natural rubber free radical and the sea squirt nanocrystalline cellulose free radical collide, or a condensation reaction occurs between the hydroxyl group and the carboxyl group to form a covalent bond, between the two It acts as a bridge-like transmission between them. The invention solves the problem of weak interfacial bonding force caused by only physical action in the composite material prepared by the segmented blending method, that is, the natural latex is first epoxidized and then blended with the ascidian nanocrystalline cellulose suspension. With the addition of 10 parts of t-CNs, the tensile strength, tear strength and 300% tensile stress of the composites prepared by the one-pot process were increased by 3.0MPa, 4.8kN/m and 2.7MPa respectively compared with the segmented blending method.

2. In the nanocomposite material prepared by the present invention, the nanocrystalline cellulose (t-CNs) extracted from the ascidian capsule has a higher length than the nanocrystalline cellulose (c-CNs) from other sources such as cotton. , larger aspect ratio, higher crystallinity and molecular weight, the prepared nanocomposites have more excellent mechanical properties. The maximum weight loss rate decomposition temperature of t-CNs is 336 °C, which is nearly 20 °C higher than that of c-CNs, which is 317 °C. At the same time, using the one-pot process, the tensile strength, tear strength and 300% tensile stress of the composite containing 10 parts of t-CNs were increased by 4.3MPa, 6.7kN/m, 3.5%, respectively, compared with the composite containing 10 parts of c-CNs. MPa.

3. In the nanocomposite material prepared by the present invention, the epoxidation degree of ENR can be controlled by adjusting the reaction time, the amount of reagents, etc., and the epoxidation degree of ENR can be controlled through the interface grafting reaction and the hydrogen bond between the epoxy group and the hydroxyl group. The regulation of interfacial binding force, thereby regulating the mechanical properties of composite materials;

4. The sea squirt resources used in the present invention are very rich, widely distributed, and easy to obtain. At the same time, the nano-microcrystalline cellulose is derived from the sea squirt capsules that are thrown away as garbage, which realizes the reuse of waste, and has good economic and economic benefits. environmental benefits.

Description of drawings

1 is a scanning electron microscope (SEM) photograph of the ascidian nanocrystalline cellulose used in Examples 1-4 and Comparative Example 1.

FIG. 2 is a scanning electron microscope (SEM) photograph of cotton nanocrystalline cellulose used in Comparative Example 2. FIG.

FIG. 3 is an atomic force microscope (AFM) photograph of the ascidian nanocrystalline cellulose used in Examples 1-4 and Comparative Example 1. FIG.

FIG. 4 is an atomic force microscope (AFM) photograph of cotton nanocrystalline cellulose used in Comparative Example 2. FIG.

FIG. 5 is the thermogravimetric curve of the ascidian nanocrystalline cellulose and cotton nanocrystalline cellulose used in Examples 1-4 and Comparative Example 1. FIG.

FIG. 6 is the thermal weight loss differential curve of the ascidian nanocrystalline cellulose and cotton nanocrystalline cellulose used in Examples 1-4 and Comparative Example 1. FIG.

Detailed ways

The present invention will be further described in detail below with reference to the embodiments, but it should be noted that the embodiments do not constitute a limitation on the protection scope of the present invention.

Examples 1 to 4

The preparation method of the ascidian nanocrystalline cellulose suspension is as follows: soak and wash the ascidian and dissect the capsule; soak the capsule in a strong alkali at 40° C. for 24 hours to remove the proteins and lipids contained in it; then At 50°C, the protein and lipid-removed capsules were reacted in a bleaching solution made of glacial acetic acid and sodium hypochlorite for 6 hours, repeated twice, and the previous bleaching solution had to be replaced each time until the capsules turned white. ; Dry the bleached powdered cellulose crystals in a blast drying oven at 30°C, and pulverize them to a micron or millimeter scale; use the pulverized powdered cellulose crystals with a concentration of 55-65wt% sulfuric acid Acidolysis was carried out at a temperature of 40°C for 5h. After the reaction was completed, a large amount of deionized water was added to dilute the solution and reduce the temperature to terminate the reaction; then the obtained mixture was centrifuged at high speed, the supernatant was discarded, and the process was repeated for 3 Second, finally carry out medium-low speed centrifugation to obtain the upper suspension which is the ascidian nanocrystalline cellulose suspension, then put it into a dialysis bag for dialysis to make the suspension neutral or weakly acidic, and finally ultrasonically disperse for 10 min to obtain Ascidian nanocrystalline cellulose suspension.

Place the natural latex containing 100g of dry glue in a beaker according to the formula in Table 1, slowly add 5g of polyethylene glycol octyl phenyl ether, and stabilize at room temperature for 2h; The microcrystalline cellulose suspension was slowly added to the natural rubber latex with mechanical stirring during the addition; after the addition was completed, the solid content of the natural rubber was adjusted to 30% with deionized water; then the emulsion was poured into a flask and placed at 30°C In the magnetic stirrer, adjust the pH of the emulsion to 2 with formic acid, slowly drop 50g of hydrogen peroxide, and finish the reaction in 18h (ENR epoxidation degree is about 20%);

The pH of the emulsion was adjusted to 7 with ammonia water, then the emulsion was poured into a beaker for coagulation with ethanol, and then the flocs were repeatedly washed with deionized water until neutral, and dried in a blast drying oven at 50 °C to constant weight. That is, the ENR/t-CNs mixture prepared by the one-pot process is obtained;

The mixture was kneaded on a two-roll mill, and 5 parts of zinc oxide, 2 parts of stearic acid, 1.5 parts of accelerator NS (N-tert-butyl-2-benzothiazole sulfenamide), and 1.5 parts of sulfur were added successively. parts, that is, ENR/t-CNs rubber compound;

Finally, vulcanization was carried out at 145 °C for 10 minutes to obtain ENR/t-CNs nanocomposites prepared by one-pot method.

As a comparison with the one-pot process adopted in the present invention, a segmented blending method is adopted, that is, the natural latex is first epoxidized by using an epoxidizing agent, and then blended with the ascidian nanocrystalline cellulose suspension to prepare the composite material , as shown in Comparative Example 1 below.

Comparative Example 1

Segmented blending method: put the natural latex containing 100g of dry rubber in a beaker, adjust the solid content to 30% with deionized water, and slowly add 5g of polyethylene glycol octyl phenyl ether, and stabilize at room temperature for 2 hours; Then the latex was poured into the flask and placed in a magnetic stirrer at 30°C, the pH of the emulsion was adjusted to 2 with formic acid, 50g of hydrogen peroxide was slowly added dropwise, and the reaction was completed in 18h (ENR epoxidation degree was about 20%);

The pH of the emulsion was adjusted to 7 with ammonia water, and then the suspension containing 10 g of ascidian nano-microcrystalline cellulose (see Example 1-4) was slowly added and stirred evenly;

The emulsion was poured into a beaker and coagulated with ethanol, and then the flocs were repeatedly washed with deionized water until they became neutral, and dried to constant weight in a blast drying oven at 50 °C to obtain ENR/EPR prepared by segmented blending process. t-CNs mixture;

Then the mixture was mixed on a two-roll mill, and various additives were added in sequence: 5 parts of zinc oxide, 2 parts of stearic acid, 1.5 parts of accelerator NS, and 1.5 parts of sulfur to obtain ENR/t-CNs mixture rubber refining;

Finally, vulcanization was carried out at 145 °C for 10 minutes to obtain ENR/t-CNs nanocomposites prepared by staged blending process.

The sea squirt nanocrystalline cellulose (t-CNs) used in the present invention has more excellent reinforcing effect than cotton nanocrystalline cellulose (c-CNs), and the cotton nanocrystalline cellulose composite is also prepared by a one-pot process. materials, as shown in Comparative Example 2 below.

Comparative Example 2

The natural latex containing 100g of dry glue was placed in a beaker, 5g of polyethylene glycol octyl phenyl ether was slowly added, and stabilized for 2h at room temperature; then the suspension containing 10g of cotton nanocrystalline cellulose (see Example 1-4) Slowly add into the natural rubber latex, and stir mechanically during the addition; after the addition is completed, adjust the solid content of the natural rubber to 30% with deionized water; then pour the emulsion into a flask and place it in a magnetic stirring at 30°C In the device, the pH of the emulsion was adjusted to 2 with formic acid, and 50 g of hydrogen peroxide was slowly added dropwise, and the reaction was completed in 18 hours (ENR epoxidation degree was about 20%);

The pH of the emulsion was adjusted to 7 with ammonia water, then the emulsion was poured into a beaker for coagulation with ethanol, and then the flocs were repeatedly washed with deionized water until neutral, and dried in a blast drying oven at 50 °C to constant weight. That is, the ENR/c-CNs mixture prepared by the one-pot process is obtained;

Then the mixture was kneaded on a two-roll mill, and various additives were added in sequence: 5 parts of zinc oxide, 2 parts of stearic acid, 1.5 parts of accelerator NS, and 1.5 parts of sulfur to obtain ENR/c-CNs mixture. rubber refining;

Finally, the ENR/c-CNs nanocomposites prepared by one-pot method were obtained by vulcanization at 145 °C for 10 minutes.

Table 1. Formulations of rubber nanocomposites with different t-CNs contents prepared by one-pot process

Note: The t-CNs, sulfur, zinc oxide, stearic acid and NS described in the table are all parts per 100 parts of rubber; ENR-20 is ENR with epoxidation degree of 20%, that is, the reaction is 18h .

In Table 2 below, the test methods for tensile strength, tensile stress and elongation at break refer to the national standard: GB/T528-2009: Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber; tear strength test refers to the national standard : GB/T 529-2008: Determination of tear strength of vulcanized rubber or thermoplastic rubber is performed.

Table 2. Mechanical properties of Examples 1-4 and Comparative Examples 1-2

As can be seen from Table 1, in Comparative Example 2 and Comparative Example 1, the tensile strength, 300% tensile stress and tear strength of the nanocomposite prepared by the one-pot process of the present invention are respectively improved compared with the segmented blending method. Compared with the segmented blending method, the one-pot process improves the interfacial interaction between nanocrystalline cellulose and rubber, and makes the reinforcement of nanocrystalline cellulose The effect is more fully exerted.

Figure 1 is a scanning electron microscope (SEM) photograph of the raw t-CNs. Figure 2 is a scanning electron microscope (SEM) photograph of the raw material c-CNs. Figure 3 is an atomic force microscope (AFM) photograph of the raw material t-CNs. It can be seen from the figure that the diameter of t-CNs is about 10-20 nm, the length is about 500 nm-2 μm, and the aspect ratio is about 75; Figure 4 is the atomic force microscope (AFM) photo of the raw material c-CNs. It can be seen from the figure that the diameter of c-CNs is about 10-20 nm, the length is about 150-300 nm, and the aspect ratio is about 15;

Figure 5 shows the thermogravimetric curves of the raw materials t-CNs and c-CNs. It can be seen that the thermal stability of t-CNs is better than that of c-CNs;

Figure 6 shows the thermogravimetric differential curves of raw materials t-CNs and c-CNs. The maximum weight loss rate temperatures of t-CNs and c-CNs were 336 °C and 317 °C, respectively.

Comparative Example 2 and Comparative Example 2, combined with accompanying drawings 1-6, it can be seen that the one-pot process of the present invention is used to prepare the tensile strength, 300% tensile stress, Compared with the composite material containing cotton nanocrystalline cellulose, the tear strength was increased by 4.3MPa, 3.5MPa, and 6.7kN/m, respectively, indicating that the ascidian nanocrystalline cellulose with a larger aspect ratio was compared with cotton with a smaller aspect ratio. Nanocrystalline cellulose has better reinforcing effect; and with the increase of the amount of ascidian nanocrystalline cellulose, the mechanical properties are further improved;

Comparing Example 1 and Comparative Example 2, it can be seen that even if the composite material prepared by the one-pot process of the present invention only contains 5 parts of t-CNs, the tensile strength of the composite material containing 10 parts of c-CNs is higher than that of the composite material containing 300%. The tensile stress and tear strength were also increased by 1.5MPa, 1.9MPa, and 3.6kN/m respectively; it further explained that the sea squirt nanocrystalline cellulose used in the invention has a better reinforcing effect than cotton nanocrystalline cellulose;

Comparing Example 1 and Comparative Example 1, it can be seen that even if the composite material prepared by the one-pot process of the present invention only contains 5 parts of t-CNs, its tensile strength, 300% tensile stress and tear strength are better than those of the composite material prepared by the one-pot process of the present invention. The staged blending method improved the composites containing 10 parts of t-CNs. It shows that the one-pot process of the present invention can more fully exert the reinforcing effect of nanocrystalline cellulose.

At the same time, under the same amount of filler, the tensile strength and 300% tensile stress of the material prepared by this technology are obviously better than those used in Chinese invention patent CN101412825 B, Chinese invention patent application CN104530504 A and Chinese invention patent application CN104356434 A. The material prepared by the combination of nanocrystalline cellulose and carbon black or white carbon black. For example, in the patent of the present invention, when the amount of ascidian nano-microcrystalline cellulose is 20 parts, its tensile strength and 300% tensile stress are 33.5MPa and 16.5MPa respectively, which are higher than those in Chinese invention patent CN101412825B. When the total amount of white carbon black is 30 parts, the maximum tensile strength is 31.6MPa and the maximum 300% tensile stress is 13.5MPa; at the same time, in the Chinese invention patent application CN104356434A, cotton nanocrystalline cellulose and white carbon black are used in combination to prepare the maximum The tensile strength, tear strength and 300% tensile stress are 26.5MPa, 29kN/m and 4.5MPa respectively, which are comparable to the mechanical properties of adding 10 parts of ascidian nanocrystalline cellulose in the embodiment of the present invention, especially for 300% constant tensile strength. The tensile stress is far lower than the lowest 300% tensile stress of 7.3MPa in the present invention.

It should be pointed out that in the above-mentioned comparative invention patents, nanocrystalline cellulose is only partially replaced with carbon black or white carbon black, which cannot fundamentally solve the existing problems of high pollution, high energy consumption, and high density. However, the present invention completely adopts the green reinforcing filler nano-crystalline cellulose, which has a wide source of raw materials, is renewable, and does not have the problems of pollution and high energy consumption, which can bring huge economic and environmental benefits to the rubber industry market.

Examples 5 to 8

The preparation method of the ascidian nanocrystalline cellulose suspension is as follows: soaking and washing the ascidian, dissecting and leaving the capsule; soaking the capsule in a strong alkali at 60° C. for 12 hours to remove the proteins and lipids contained in it; then At 90°C, the protein and lipid-removed capsules were reacted in a bleaching solution made of glacial acetic acid and sodium hypochlorite for 12 hours, and repeated 6 times. The previous bleaching solution was replaced each time until the capsules turned white. ; Dry the bleached powdered cellulose crystals in a blast drying oven at 30°C, and pulverize them to a micron or millimeter scale; use the pulverized powdered cellulose crystals with a concentration of 55-65wt% sulfuric acid Acidolysis was carried out, the acidolysis temperature was 60°C, and the time was 0.5h. After the reaction was completed, a large amount of deionized water was added, the solution was diluted and the temperature was lowered to terminate the reaction; then the obtained mixture was centrifuged at high speed, the supernatant was discarded, and the process was repeated. 3 times, and finally carry out medium-low speed centrifugation to obtain the upper suspension, which is the ascidian nanocrystalline cellulose suspension, then put it into a dialysis bag for dialysis to make the suspension neutral or weakly acidic, and finally ultrasonically disperse for 50min, that is, The ascidian nanocrystalline cellulose suspension was obtained.

Place the natural latex containing 100g of dry glue in a beaker according to the formula in Table 3, slowly add 5g of polyethylene glycol octyl phenyl ether, and stabilize at room temperature for 2h; The liquid was slowly added to the natural rubber latex, and mechanically stirred during the addition; after the addition was completed, the solid content of the natural rubber was adjusted to 30% with deionized water; then the emulsion was poured into a flask and placed in a magnetic stirrer at 30°C , adjust emulsion pH=4 with formic acid, slowly add 50g hydrogen peroxide dropwise, and finish the reaction after 8h, 18h, 30h, 42h respectively;

The pH of the emulsion was adjusted to 7 with ammonia water, then the emulsion was poured into a beaker for coagulation with ethanol, and then the flocs were repeatedly washed with deionized water until neutral, and dried in a blast drying oven at 50 °C to constant weight. That is, ENR/t-CNs mixtures with different degrees of epoxidation prepared by one-pot process are obtained;

Then the mixture is mixed on a two-roll mill, and 1.5 parts of vulcanizing agent DCP (dicumyl peroxide) is added to obtain ENR/t-CNs mixed rubber;

Finally, vulcanization was carried out at 170 °C for 8 minutes to obtain ENR/t-CNs nanocomposites with different epoxidation degrees prepared by one-pot method.

In the formula table, ENR-10, ENR-20, ENR-30 and ENR-40 respectively indicate that the degree of epoxidation is 10% (reaction time is 8h), 20% (reaction time is 18h), 30% (reaction time is 30h) ), an ENR of 40% (42h reaction time).

Table 3. Formulations of ENR/t-CNs composites with different degrees of epoxidation prepared by one-pot process

Note: The t-CNs and DCP mentioned in the table are the parts per 100 parts of rubber.

In Table 4, the test methods of tensile strength, tensile stress and elongation at break refer to the national standard: GB/T 528-2009: Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber; tear strength test refers to the national standard : GB/T 529-2008: Determination of tear strength of vulcanized rubber or thermoplastic rubber is performed.

Table 4. Mechanical properties of Examples 5-8

Comparing Example 1 and Examples 5-8, it can be seen that with the prolongation of the epoxidation reaction time, the mechanical properties of the prepared composite materials all showed a trend of increasing gradually. This is because with the prolongation of the reaction time, on the one hand, the probability of the grafting reaction between ENR and t-CNs increases, and more chemical bonds are formed between the two interfaces; on the other hand, the ENR molecular chain generates more epoxy groups Even when the degree of epoxidation is high, a small amount of epoxy groups are ring-opened to generate polar groups such as hydroxyl and carboxyl groups, which form stronger hydrogen bonds with the hydroxyl groups on the surface of t-CNs. The two work together to enhance the interfacial bonding force between ENR and t-CNs. When subjected to external action, the stress can be well transferred between the two interfaces, so that it can withstand greater damage on a macroscopic scale. This shows that the one-pot process of the present invention can significantly improve the interfacial interaction between the rubber and the nanocrystalline cellulose by adjusting the reaction conditions, thereby realizing the regulation of the final material properties.

Claims (9)

1. The method for preparing the ascidian nano microcrystalline cellulose/rubber nano composite material by the one-pot method is characterized by comprising the following steps of:

1) diluting the natural latex at room temperature, slowly dropwise adding an emulsifier, and stirring for 1-3 h;

2) blending the sea squirt nano microcrystalline cellulose suspension with the emulsified natural latex obtained in the step 1) to obtain a premix; wherein the mass ratio of the sea squirt nano microcrystalline cellulose to the natural latex is 3: 100-30: 100; the preparation method of the sea squirt nano microcrystalline cellulose suspension comprises the following steps: soaking and cleaning ascidians, dissecting and keeping tunic; soaking the tunica vaginalis in strong alkali at 40-60 deg.C for 12-24 hr to remove protein and lipid contained therein; then, the tunicate with protein and lipid removed is reacted in bleaching solution prepared from glacial acetic acid and sodium hypochlorite for 6-12h at 50-90 deg.C, and repeated for 2-6 times, each time the previous bleaching solution is required to be replaced, until the tunicate turns white; drying the bleached powdered cellulose crystals in a forced air drying oven at the temperature of 30-60 ℃, and crushing the dried powdered cellulose crystals to a micrometer or millimeter level; carrying out acidolysis on the crushed powdered cellulose crystals by using 55-65 wt% sulfuric acid, wherein the acidolysis temperature is 40-60 ℃, the acidolysis time is 0.5-5h, adding a large amount of deionized water after the reaction is finished, diluting the solution, and reducing the temperature to terminate the reaction; then carrying out high-speed centrifugation on the obtained mixed solution, removing supernatant, repeating the centrifugation for 3 times, finally carrying out medium-low speed centrifugation treatment to obtain upper suspension, namely ascidian nano microcrystalline cellulose suspension, then putting the suspension into a dialysis bag for dialysis to enable the suspension to be neutral or weakly acidic, and finally carrying out ultrasonic dispersion for 10-50min to obtain ascidian nano microcrystalline cellulose suspension;

3) slowly dropwise adding formic acid into the premix to adjust the pH to 2-4, and then slowly adding hydrogen peroxide to react; the molar ratio of the hydrogen peroxide to the natural rubber is 3: 1-1: 1;

4) after the reaction is finished, adjusting the pH value of the mixed solution to 6-8 by using ammonia water, solidifying, rinsing, dehydrating and drying to obtain a sea squirt nano microcrystalline cellulose/rubber mixture;

5) mixing the mixture obtained in the step 4) with a vulcanizing agent on an open mill, standing, and vulcanizing and forming to obtain the sea squirt nano microcrystalline cellulose/rubber nano composite material.

2. The method of claim 1, wherein: the sea squirt nano microcrystalline cellulose is a rod-shaped crystalline product which is extracted from tunicates of Halocynthia Roretzi or Halocynthia Przewalskii and has the diameter of 10-20 nm, the length of 500 nm-2 mu m and the length-diameter ratio of 70-80.

3. The method of claim 1, wherein: the mass concentration of the diluted natural latex in the step 1) is 20-40%.

4. The method of claim 1, wherein: the emulsifier is polyoxyethylene lauric ether or polyethylene glycol octyl phenyl ether. The amount of emulsifier is 5-10% of the weight of the dry rubber in the latex.

5. The method of claim 1, wherein: the mass concentration of the hydrogen peroxide is 30-50%.

6. The method of claim 1, wherein: the reaction temperature is 30-50 ℃, the reaction time is 10-40 h, and magnetic or mechanical stirring is carried out in the reaction process.

7. The method of claim 1, wherein: the coagulation is to carry out co-flocculation by adopting a chemical reagent, wherein the chemical reagent is one or more of ethanol, formic acid and acetic acid; the rinsing is to repeatedly wash the solidified product by using tap water until the product is neutral.

8. The method of claim 1, wherein: and the dehydration is to remove the surface moisture by wiping with filter paper or vacuum filtration.

9. The method of claim 1, wherein: and the drying is to dry the product to constant weight by using a vacuum drying oven or an air blast drying oven with the temperature of 40-60 ℃.

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