CN107474343B - Method for preparing sea squirt nano microcrystalline cellulose/rubber nano composite material by one-pot method - Google Patents
Method for preparing sea squirt nano microcrystalline cellulose/rubber nano composite material by one-pot method Download PDFInfo
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Abstract
The invention discloses a method for preparing a sea squirt nano microcrystalline cellulose/rubber nano composite material by a one-pot method. Diluting natural latex at room temperature, and slowly dripping an emulsifier; blending the sea squirt nano microcrystalline cellulose suspension with the emulsified natural latex to obtain a premix; slowly dripping formic acid into the premix, and then slowly adding hydrogen peroxide to react; after the reaction is finished, adjusting the pH value to 6-8, solidifying, rinsing, dehydrating and drying to obtain a sea squirt nano microcrystalline cellulose/rubber mixture; mixing the obtained mixture with a vulcanizing agent on an open mill, standing, and vulcanizing and molding. The invention overcomes the problem of poor strength caused by only physical interaction between the interfaces in the prior art, and the prepared rubber nano composite material has excellent performances of high strength, high modulus, high wear resistance and the like, and can more fully exert the reinforcing effect of the nano microcrystalline cellulose.
Description
Technical Field
The invention belongs to the technical field of rubber, and particularly relates to a sea squirt nano microcrystalline cellulose/rubber nano composite material prepared by a one-pot method process.
Background art:
carbon black and white carbon black are the most commonly used reinforcing fillers in the rubber industry, but have the defects of high pollution, high energy consumption, dependence on petroleum resources and the like which are difficult to avoid, so that the development of the green reinforcing fillers capable of being developed continuously is of great significance.
Cellulose is a polysaccharide biological material widely existing in nature, and the yield is very rich. The rodlike nano microcrystalline Cellulose (CNs) can be prepared after a series of treatments, has the advantages of large specific surface area, high strength, wide sources, reproducibility and the like, is used as a novel green reinforcing filler of rubber, is used as a supplement or partial substitute of traditional reinforcing fillers such as carbon black, white carbon black and the like, and can bring great economic and environmental benefits to the rubber industry. Chinese invention patent CN102002173B discloses a method for reinforcing rubber by combining nano microcrystalline cellulose and white carbon black, mixing nano microcrystalline cellulose suspension with natural latex, then mixing white carbon black and modifier by an open mill, and improving the interface interaction between CNs and white carbon black and natural rubber mainly by means of silane or titanate coupling agent, zinc (magnesium) methacrylate, rubber adhesive and other modifiers;
the Chinese invention patent application CN 104530504A discloses a method for preparing a rubber composite material of nano microcrystalline cellulose based on waste cotton materials, which comprises the steps of firstly reacting CNs with a modifier, then mixing the CNs with natural latex, and finally adding white carbon black through an open mill, wherein the interface interaction of the CNs with the white carbon black and the natural rubber is improved by the same means of the modifiers such as a coupling agent and the like;
the Chinese patent application CN 105419002A discloses a preparation method of bagasse nanocellulose and a rubber composite material thereof, which comprises the steps of adding a (silane and titanate coupling agent) and a m-methyl white system into a nanocellulose suspension, mixing the nanocellulose suspension with natural latex, and finally mixing the natural latex with white carbon black through an open mill.
As can be seen from the above, the rubber nanocomposites prepared as described above are obtained only by simply modifying the CNs with a coupling agent and then mixing with natural latex. The prepared composite material only has physical interaction between the filler and the rubber, and the high reinforcing effect of the nano microcrystalline cellulose cannot be fully reflected. Meanwhile, in the prior art, the nano microcrystalline cellulose is only used for partially replacing carbon black or white carbon black, the consumption of high-pollution fillers such as carbon black and white carbon black is still large, and the problems of high pollution, high energy consumption, high density and the like in the current market cannot be fundamentally solved. Furthermore, the above mentioned nanocrystallme celluloses used as reinforcing fillers for rubbers are all derived from terrestrial plants, such as cotton, wood, hemp, etc., and these resources are also of significant use in other respects, which may lead to an increase in the cost of extracting the nanocrystallme celluloses therefrom.
The invention content is as follows:
the invention aims to provide a more efficient, economic and environment-friendly nano microcrystalline cellulose/rubber nano composite material and a preparation method thereof aiming at the problems in the prior art, and the method can overcome the problem of weak interface bonding force between rubber and nano microcrystalline cellulose in the prior simple physical blending technology, so that the nano microcrystalline cellulose can exert more excellent reinforcing effect.
The inventors have noted that cellulose can be extracted from tunicates (tunicates) present in marine sources. Sea squirts sometimes adhere to the bottom of ships, affecting ship speed and adversely affecting the aquaculture industry. When the sea squirts are used as food, the sea squirts are thrown away as garbage, and cellulose is mainly contained in the sea squirts, so that the sea squirts are changed into valuable things, and the sea squirts have important economic and environmental benefits.
In the rubber/nano microcrystalline cellulose composite material prepared by a physical blending method, only simple physical interaction exists between rubber and nano microcrystalline cellulose, the interface bonding force is weak, and peeling is easy to occur under the action of external force, so that damage is generated. If the preparation process is improved, the interfacial chemical bonding of the nano microcrystalline cellulose and the rubber is realized, and the dispersion of the nano microcrystalline cellulose in the rubber is improved, the high reinforcing effect of the nano microcrystalline cellulose can be fully exerted.
The purpose of the invention is realized by the following technical scheme:
the one-pot method for preparing the ascidian nano microcrystalline cellulose/rubber nano composite material comprises the following steps:
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;
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.
In order to further achieve the purpose of the invention, the sea squirt nano microcrystalline cellulose is preferably a rod-shaped crystalline product which is extracted from tunicates of Halocynthia Roretzi or Halocynthia pipiens and has the diameter of 10-20 nm, the length of 500 nm-2 μm and the length-diameter ratio of 70-80.
Preferably, the mass concentration of the diluted natural latex in the step 1) is 20-40%, preferably 30%.
Preferably, the emulsifier is polyoxyethylene lauric ether or polyethylene glycol octyl phenyl ether. The amount of emulsifier used is from 5 to 10%, preferably 8%, by weight of the dry gum in the latex.
Preferably, the preparation method of the ascidian 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; and 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 the ascidian nano microcrystalline cellulose suspension.
Preferably, the mass concentration of the hydrogen peroxide is 30-50%.
Preferably, the reaction temperature is 30-50 ℃, preferably 30 ℃, the reaction time is 10-40 h, and magnetic or mechanical stirring is carried out in the reaction process.
Preferably, the coagulation is a co-flocculation with a chemical agent, the chemical agent being 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.
Preferably, the dehydration is to remove the surface moisture by wiping with filter paper or vacuum filtration.
Preferably, 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 ℃.
Compared with the prior art, the invention has the following advantages:
1. the nano composite material is prepared by adopting a one-pot process, and an epoxidation reagent initiates a natural epoxidation reaction to generate epoxidized natural rubber and also initiates an oxidation reaction of hydroxyl on the surface of the sea squirt nano microcrystalline cellulose to generate aldehyde groups, carboxyl groups and other groups; in the reaction process, the free epoxidized natural rubber radicals and the free ascidian nano microcrystalline cellulose radicals collide, or the hydroxyl and the carboxyl undergo a condensation reaction to form covalent bonds, so that the covalent bonds have a transmission function similar to a bridge. The invention solves the problem that the interface bonding force is weak due to the physical action only in the composite material prepared by the segmented blending method, namely the natural latex is firstly epoxidized and then blended with the sea squirt nano microcrystalline cellulose suspension. The tensile strength, the tearing strength and the 300 percent stress at definite elongation of the composite material prepared by the one-pot process are respectively improved by 3.0MPa, 4.8kN/m and 2.7MPa compared with the segmented blending method by adding 10 parts of t-CNs.
2. In the nano composite material prepared by the invention, compared with nano microcrystalline cellulose (c-CNs) from other sources such as cotton and the like, nano microcrystalline cellulose (t-CNs) extracted from sea squirt tunica has higher length, larger length-diameter ratio and higher crystallinity and molecular weight, and the prepared nano composite material has more excellent mechanical property. the maximum weight loss rate decomposition temperature of the t-CNs is 336 ℃, which is improved by about 20 ℃ compared with 317 ℃ of the c-CNs. Meanwhile, the tensile strength, the tearing strength and the 300% stress at definite elongation of the composite material containing 10 parts of t-CNs are respectively improved by 4.3MPa, 6.7kN/m and 3.5MPa compared with the composite material containing 10 parts of c-CNs by adopting a one-pot process.
3. In the nano composite material prepared by the invention, the epoxidation degree of ENR can be controlled by regulating and controlling the reaction time, the dosage of a reaction reagent and the like, and the regulation and control of the interface binding force are realized through the interface grafting reaction and the hydrogen bond action between an epoxy group and a hydroxyl group, so that the mechanical property of the composite material is regulated and controlled;
4. the sea squirt used in the invention has rich resources, wide distribution and easy acquisition, and meanwhile, the nano microcrystalline cellulose is derived from the sea squirt tunic thrown away as garbage, thereby realizing the reutilization of waste and having good economic and environmental benefits.
Drawings
FIG. 1 is a Scanning Electron Microscope (SEM) photograph of the sea squirt nano microcrystalline cellulose used in examples 1 to 4 and comparative example 1.
Fig. 2 is a Scanning Electron Microscope (SEM) photograph of the cotton nanocrystallite cellulose used in comparative example 2.
FIG. 3 is an Atomic Force Microscope (AFM) photograph of the sea squirt nano microcrystalline cellulose used in examples 1 to 4 and comparative example 1.
FIG. 4 is an Atomic Force Microscope (AFM) photograph of the cotton nanocrystallite cellulose used in comparative example 2.
FIG. 5 is a graph showing the thermogravimetric curves of the ecthyma nano-microcrystalline cellulose and the cotton nano-microcrystalline cellulose used in examples 1 to 4 and comparative example 1.
FIG. 6 is a thermogravimetric differential curve of ascidian nanocrystallme cellulose and cotton nanocrystallme cellulose used in examples 1-4 and comparative example 1.
Detailed Description
The present invention will be described in further detail with reference to examples, but it should be understood that the present invention is not limited to the examples.
Examples 1 to 4
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 deg.C for 24 hr to remove protein and lipid contained therein; then, the protein and lipid-removed tunicate is reacted in bleaching solution prepared from glacial acetic acid and sodium hypochlorite for 6h at 50 ℃, and the reaction is repeated for 2 times, wherein the previous bleaching solution needs to be replaced each time until the tunicate turns white; drying the bleached powdery cellulose crystals in a forced air drying oven at the temperature of 30 ℃, and crushing the powdery 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 ℃, the acidolysis time is 5 hours, adding a large amount of deionized water after the reaction is finished, diluting the solution, and reducing the temperature to terminate the reaction; and 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 10min to obtain the ascidian nano microcrystalline cellulose suspension.
Placing natural rubber latex containing 100g of dry rubber into a beaker according to the formula in the table 1, slowly adding 5g of polyethylene glycol octyl phenyl ether, and stabilizing for 2 hours at room temperature; then slowly adding the ascidian nano microcrystalline cellulose suspension liquid with different parts in the table 1 into the natural latex, and mechanically stirring in the adding process; after the addition is finished, deionized water is used for adjusting the solid content of the natural rubber to be 30%; then the emulsion is poured into a flask and placed in a magnetic stirrer at 30 ℃, formic acid is used for adjusting the pH value of the emulsion to be 2, 50g of hydrogen peroxide is slowly added dropwise, and the reaction is finished for 18h (the epoxidation degree of ENR is about 20%);
adjusting the pH value of the emulsion to 7 by adopting ammonia water, pouring the emulsion into a beaker, coagulating the emulsion by using ethanol, repeatedly washing flocculate by using deionized water until the flocculate is neutral, and drying the flocculate to constant weight in a forced air drying oven at 50 ℃ to obtain an ENR/t-CNs mixture prepared by a one-pot process;
mixing the mixture on a double-roll open mill, and sequentially adding 5 parts of zinc oxide, 2 parts of stearic acid, 1.5 parts of accelerator NS (N-tert-butyl-2-benzothiazole sulfonamide) and 1.5 parts of sulfur to obtain ENR/t-CNs rubber compound;
and finally, vulcanizing for 10 minutes at 145 ℃ to obtain the ENR/t-CNs nano composite material prepared by the one-pot method.
As a comparison of the one-pot process employed in the present invention, a segmented blending process was employed, i.e., natural latex was first epoxidized with an epoxidizing agent and then blended with ascidian nanocrystaline cellulose suspension to prepare a composite material, as shown in comparative example 1 below.
Comparative example 1
A segmented blending method: placing natural latex containing 100g of dry glue in a beaker, adjusting the solid content to 30% by using deionized water, slowly adding 5g of polyethylene glycol octyl phenyl ether, and stabilizing at room temperature for 2 hours; then pouring the latex into a flask, placing the flask in a magnetic stirrer at 30 ℃, adjusting the pH of the emulsion to be 2 by using formic acid, slowly dropwise adding 50g of hydrogen peroxide, and finishing the reaction for 18h (the epoxidation degree of ENR is about 20%);
adjusting the pH of the emulsion to 7 with ammonia water, then slowly adding a suspension containing 10g of ascidian nano microcrystalline cellulose (see examples 1-4) and stirring uniformly;
pouring the emulsion into a beaker, coagulating the emulsion with ethanol, repeatedly washing flocculate with deionized water until the flocculate is neutral, and drying the flocculate in a forced air drying oven at 50 ℃ until the weight of the flocculate is constant to obtain an ENR/t-CNs mixture prepared by a segmented blending process;
the mixture was then mixed on a two-roll mill, and the various adjuvants 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 rubber compound;
and finally, vulcanizing for 10 minutes at 145 ℃ to obtain the ENR/t-CNs nano composite material prepared by the segmented blending process.
The ascidian nano microcrystalline cellulose (t-CNs) adopted by the invention has more excellent reinforcing effect than cotton nano microcrystalline cellulose (c-CNs), and the cotton nano microcrystalline cellulose composite material is prepared by adopting a one-pot process as shown in the following comparative example 2.
Comparative example 2
Placing natural latex containing 100g of dry glue in a beaker, slowly adding 5g of polyethylene glycol octyl phenyl ether, and stabilizing at room temperature for 2 h; then the suspension containing 10g of cotton nanocrystallme cellulose (see examples 1-4) was slowly added to the natural latex with mechanical stirring during the addition; after the addition is finished, deionized water is used for adjusting the solid content of the natural rubber to be 30%; then the emulsion is poured into a flask and placed in a magnetic stirrer at 30 ℃, formic acid is used for adjusting the pH value of the emulsion to be 2, 50g of hydrogen peroxide is slowly added dropwise, and the reaction is finished for 18h (the epoxidation degree of ENR is about 20%);
adjusting the pH value of the emulsion to 7 by adopting ammonia water, pouring the emulsion into a beaker, coagulating the emulsion by using ethanol, repeatedly washing flocculate by using deionized water until the flocculate is neutral, and drying the flocculate to constant weight in a forced air drying oven at 50 ℃ to obtain an ENR/c-CNs mixture prepared by a one-pot process;
the mixture was then mixed on a two-roll mill, and the various adjuvants 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 rubber compound;
and finally, vulcanizing for 10 minutes at 145 ℃ to obtain the ENR/c-CNs nano composite material prepared by the one-pot method.
TABLE 1 formulation for preparing rubber nanocomposites with different t-CNs content using one-pot process
Note: the t-CNs, sulfur, zinc oxide, stearic acid and NS in the table are all contained in parts per 100 parts of rubber; ENR-20 is ENR with 20 percent of epoxidation degree, namely reaction for 18 h.
In table 2 below, the test methods for tensile strength, stress at definite elongation, and elongation at break refer to the national standards: GB/T528-2009: the determination of the tensile stress strain properties of the vulcanized rubber or thermoplastic rubber is carried out; tear strength test reference national standard: GB/T529 and 2008: the determination of the tear strength of the vulcanized rubber or thermoplastic rubber is carried out.
TABLE 2 mechanical properties of examples 1 to 4 and comparative examples 1 to 2
As can be seen from Table 1, in comparative example 2 and comparative example 1, the tensile strength, 300% stress at definite elongation and tear strength of the nanocomposite prepared by the one-pot process of the present invention are respectively improved by 3.0MPa, 2.7MPa and 4.8kN/m compared with those of the nanocomposite prepared by the segmented blending method; compared with a segmented blending method, the one-pot method improves the interface interaction between the nano microcrystalline cellulose and the rubber, so that the reinforcing effect of the nano microcrystalline cellulose is more fully exerted.
FIG. 1 is a Scanning Electron Microscope (SEM) photograph of the starting material t-CNs. FIG. 2 is a Scanning Electron Microscope (SEM) photograph of the starting material c-CNs. FIG. 3 is an Atomic Force Microscope (AFM) photograph of the starting t-CNs. As can be seen from the figure, the t-CNs have a diameter of about 10-20 nm, a length of about 500 nm-2 μm, and an aspect ratio of about 75; FIG. 4 is an Atomic Force Microscope (AFM) photograph of the raw material c-CNs. The figure shows that the diameter of the c-CNs is about 10-20 nm, the length is about 150-300 nm, and the length-diameter ratio is about 15;
FIG. 5 is a thermogravimetric plot of the starting materials t-CNs and c-CNs. It can be seen that t-CNs are more thermally stable than c-CNs;
FIG. 6 is a thermogravimetric differential curve of the raw materials t-CNs and c-CNs. the maximum weight loss rate temperatures of t-CNs and c-CNs were 336 ℃ and 317 ℃ respectively.
Comparing the example 2 with the comparative example 2, and simultaneously combining the attached drawings 1-6, it can be seen that the tensile strength, 300% stress at definite elongation and tearing strength of the composite material containing ascidian nano microcrystalline cellulose prepared by the one-pot process are respectively improved by 4.3MPa, 3.5MPa and 6.7kN/m compared with the composite material containing cotton nano microcrystalline cellulose; the sea squirt nano microcrystalline cellulose with larger length-diameter ratio has more excellent reinforcing effect than the cotton nano microcrystalline cellulose with smaller length-diameter ratio; and with the increase of the dosage of the sea squirt nano microcrystalline cellulose, the mechanical property is further improved;
as can be seen by comparing example 1 with comparative example 2, even if the composite material prepared by the one-pot process only contains 5 parts of t-CNs, the tensile strength, 300 percent stress at definite elongation and the tearing strength of the composite material containing 10 parts of c-CNs are respectively improved by 1.5MPa, 1.9MPa and 3.6 kN/m; further illustrates that the ascidian nano microcrystalline cellulose used by the invention has more excellent reinforcing effect than the cotton nano microcrystalline cellulose;
comparing example 1 with comparative example 1, it can be seen that the tensile strength, 300% stress at definite elongation, and tear strength of the composite material prepared by the one-pot process of the present invention are improved compared with those of the composite material containing 10 parts of t-CNs by the segmented blending method even if the composite material only contains 5 parts of t-CNs. The one-pot method process of the invention can fully exert the reinforcing effect of the nano microcrystalline cellulose.
Meanwhile, under the same filler dosage, the tensile strength and 300% stress at definite elongation of the material prepared by the technology are obviously superior to those of the material prepared by the technology of combining the nano microcrystalline cellulose and the carbon black or the white carbon black adopted in the Chinese patent application CN101412825B, the Chinese patent application CN 104530504A and the Chinese patent application CN 104356434A. For example, in the patent of the invention, when the dosage of the ascidian nano microcrystalline cellulose is 20 parts, the tensile strength and 300% stress at definite elongation are respectively 33.5MPa and 16.5MPa, which are higher than the maximum tensile strength of 31.6MPa and the maximum stress at definite elongation of 300% of the total dosage of the nano microcrystalline cellulose and the white carbon black of 30 parts in the patent CN101412825B of the Chinese invention; meanwhile, the maximum tensile strength, the tear strength and the 300% stress at definite elongation of the material prepared by adopting the cotton nano microcrystalline cellulose and the white carbon black in the Chinese patent application CN104356434A are respectively 26.5MPa, 29kN/m and 4.5MPa, and the maximum tensile strength, the tear strength and the 300% stress at definite elongation are equivalent to the mechanical properties of 10 parts of ascidian nano microcrystalline cellulose added in the embodiment of the invention, and particularly for the 300% stress at definite elongation, the maximum tensile strength, the tear strength and the 300% stress at definite elongation are far lower than the minimum stress at 300% stress at definite elongation of 7.3.
It should be noted that, in the above cited patent of the invention, only the nano microcrystalline cellulose is used to partially replace carbon black or white carbon black, and the problems of high pollution, high energy consumption, high density and the like existing at present cannot be fundamentally solved. The invention completely adopts the green reinforcing filler nano microcrystalline cellulose, has wide raw material source, is renewable, does not have the problems of pollution, high energy consumption and the like, and can bring great economic and environmental benefits for the rubber industrial market.
Examples 5 to 8
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 60 deg.C for 12 hr to remove protein and lipid contained therein; then, the tunica vaginalis without protein and lipid is reacted in bleaching solution prepared from glacial acetic acid and sodium hypochlorite for 12h at 90 ℃, and the reaction is repeated for 6 times, wherein the previous bleaching solution needs to be replaced each time until the tunica vaginalis becomes white; drying the bleached powdery cellulose crystals in a forced air drying oven at the temperature of 30 ℃, and crushing the powdery 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 60 ℃, the acidolysis time is 0.5h, adding a large amount of deionized water after the reaction is finished, diluting the solution and reducing the temperature to terminate the reaction; and 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 50min to obtain the ascidian nano microcrystalline cellulose suspension.
Placing natural rubber latex containing 100g of dry rubber into a beaker according to the formula in the table 3, slowly adding 5g of polyethylene glycol octyl phenyl ether, and stabilizing for 2 hours at room temperature; slowly adding the suspension containing 5g of ascidian nano microcrystalline cellulose into the natural latex, and mechanically stirring in the adding process; after the addition is finished, deionized water is used for adjusting the solid content of the natural rubber to be 30%; then pouring the emulsion into a flask, placing the flask in a magnetic stirrer at 30 ℃, adjusting the pH of the emulsion to be 4 by formic acid, slowly dropwise adding 50g of hydrogen peroxide, and reacting for 8h, 18h, 30h and 42h respectively;
adjusting the pH value of the emulsion to 7 by adopting ammonia water, pouring the emulsion into a beaker, coagulating the emulsion by using ethanol, repeatedly washing flocculate by using deionized water until the flocculate is neutral, and drying the flocculate to constant weight in a forced air drying oven at 50 ℃ to obtain a mixture of ENR/t-CNs with different epoxidation degrees prepared by a one-pot process;
then mixing the mixture on a double-roller open mill, and adding 1.5 parts of vulcanizing agent DCP (dicumyl peroxide) to obtain ENR/t-CNs rubber compound;
and finally, vulcanizing for 8 minutes at the temperature of 170 ℃ to obtain the ENR/t-CNs nano composite materials with different epoxidation degrees, which are prepared by a one-pot method.
ENR-10, ENR-20, ENR-30 and ENR-40 in the formula table respectively represent ENR with epoxidation degree of 10% (reaction time of 8h), 20% (reaction time of 18h), 30% (reaction time of 30h) and 40% (reaction time of 42 h).
TABLE 3 formulation for preparing ENR/t-CNs composite materials with different epoxidation degrees by one-pot process
Note: the t-CNs and DCP in the tables are the parts per 100 parts of rubber.
In table 4, the test methods for tensile strength, stress at definite elongation, and elongation at break refer to the national standards: GB/T528-2009: the determination of the tensile stress strain properties of the vulcanized rubber or thermoplastic rubber is carried out; tear strength test reference national standard: GB/T529 and 2008: the determination of the tear strength of the vulcanized rubber or thermoplastic rubber is carried out.
TABLE 4 mechanical properties of examples 5 to 8
As can be seen from comparison of example 1 and examples 5 to 8, the composite materials prepared exhibited a tendency to gradually increase in mechanical properties with the increase in epoxidation reaction time. The reason is that the probability of the graft reaction between ENR and t-CNs is improved along with the prolonging of the reaction time, and more chemical bonds are formed between the interfaces of ENR and t-CNs; on the other hand, ENR molecular chains generate more epoxy groups, even a small amount of epoxy groups open rings to generate polar groups such as hydroxyl, carboxyl and the like at high epoxidation degree, and the polar groups and the hydroxyl on the surface of t-CNs form stronger hydrogen bond action. The ENR and the t-CNs jointly improve the interface bonding force between the ENR and the t-CNs, and when the ENR and the t-CNs are acted by the outside, stress can be well transferred between the interfaces of the ENR and the t-CNs, so that the ENR and the t-CNs can bear larger damage macroscopically. The method shows that the one-pot method process can obviously improve the interface interaction between the rubber and the nano microcrystalline cellulose by regulating and controlling reaction conditions, thereby realizing the regulation and control of the final material performance.
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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