阅读说明：本技术 一种橡胶-改性淀粉复合材料及其制备方法 (Rubber-modified starch composite material and preparation method thereof ) 是由 杨昌金 夏文 赵鹏飞 廖双泉 彭政 于 2020-05-22 设计创作，主要内容包括：本发明属于橡胶技术领域,具体涉及一种天然橡胶-改性淀粉复合材料及其制备方法。本发明提供了一种天然橡胶-改性淀粉复合材料,包括如下质量份数的制备原料：天然橡胶100份；淀粉1～50份；环氧化天然橡胶0.1～10份；硫化加工助剂0.2～12份；所述天然橡胶和环氧化天然橡胶均以干胶计。在本发明中,环氧化天然橡胶中的环氧基能够和淀粉中的羟基反应,对淀粉进行改性,有利于提高淀粉在天然橡胶中的分散性,进而有利于改善橡胶-改性淀粉复合材料的力学性能和生热性能。实验结果表明,本发明提供的橡胶-改性淀粉复合材料拉伸强度达29.81MPa,撕裂强度达39.7MPa,力学性能优良；压缩疲劳温升低至19℃,生热低。(The invention belongs to the technical field of rubber, and particularly relates to a natural rubber-modified starch composite material and a preparation method thereof. The invention provides a natural rubber-modified starch composite material which comprises the following preparation raw materials in parts by mass: 100 parts of natural rubber; 1-50 parts of starch; 0.1-10 parts of epoxidized natural rubber; 0.2-12 parts of a vulcanization processing aid; the natural rubber and the epoxidized natural rubber are calculated by dry rubber. In the invention, the epoxy group in the epoxidized natural rubber can react with the hydroxyl group in the starch to modify the starch, which is beneficial to improving the dispersibility of the starch in the natural rubber and further beneficial to improving the mechanical property and the heat generation property of the rubber-modified starch composite material. Experimental results show that the tensile strength of the rubber-modified starch composite material provided by the invention reaches 29.81MPa, the tear strength reaches 39.7MPa, and the mechanical property is excellent; the compression fatigue temperature rises to 19 ℃ and the heat generation is low.)

1. The rubber-modified starch composite material is characterized by comprising the following preparation raw materials in parts by mass:

100 parts of natural rubber;

1-50 parts of starch;

0.1-10 parts of epoxidized natural rubber;

0.2-12 parts of a vulcanization processing aid;

the natural rubber and the epoxidized natural rubber are calculated by dry rubber.

2. The rubber-modified starch composite material according to claim 1, wherein the epoxidized natural rubber has an epoxidation degree of 2 to 50.

3. The rubber-modified starch composite of claim 1, wherein the starch is one or more of tapioca starch, corn starch, and rice starch.

4. The rubber-modified starch composite of claim 1, wherein the vulcanization processing aid is a mixture of sulfur, N-t-butyl-2-benzothiazolehypoxanthamide, zinc oxide, and stearic acid.

5. The rubber-modified starch composite material as claimed in claim 4, wherein the mass ratio of the sulfur, the N-tert-butyl-2-benzothiazole sulfonamide, the zinc oxide and the stearic acid is (1-3): (0.5-2): (3-5): (1-3).

6. A method for preparing a rubber-modified starch composite material as claimed in any one of claims 1 to 5, comprising the steps of:

mixing and modifying the starch aqueous solution and the epoxidized natural rubber to obtain modified starch aqueous dispersion;

mixing the modified starch aqueous dispersion and natural rubber, and then sequentially performing solidification treatment and drying to obtain a composite material precursor;

and mixing the composite material precursor with a vulcanization processing aid, and then vulcanizing to obtain the rubber-modified starch composite material.

7. The method according to claim 6, wherein the concentration of the aqueous starch solution is 10 to 20 wt.%.

8. The preparation method according to claim 6, wherein the temperature of the mixing modification is 40-80 ℃ and the time is 5-60 min; the mixing modification is carried out under the conditions of ultrasound and stirring; the power of the ultrasonic wave is 700-1000W; the rotating speed of the stirring is 200-400 rpm.

9. The method according to claim 6, wherein the coagulation treatment is acetic acid coagulation, formic acid coagulation, steam coagulation, or calcium chloride coagulation.

10. The method according to claim 6, wherein the vulcanization temperature is 140 to 150 ℃.

Technical Field

The invention belongs to the technical field of rubber, and particularly relates to a rubber-modified starch composite material and a preparation method thereof.

Background

Natural rubber is a natural high molecular compound with cis-1, 4-polyisoprene as a main component, and 91-94% of the natural rubber is rubber hydrocarbon (cis-1, 4-polyisoprene), and the balance is non-rubber substances such as protein, fatty acid, ash, saccharides and the like. Starch is a polyhydroxy polymer, and the surface hydroxyl activity of the starch is low, and the compatibility between the starch and rubber materials is poor, so that how to finely and uniformly disperse the starch in a rubber matrix and obtain firm interfacial bonding force is very important for whether the starch can be used as a reinforcing agent of rubber or not.

At present, the compatibility of a rubber matrix and starch can be improved and the divergence of the starch in the rubber matrix can be improved by modifying the starch (a silane coupling agent, a graft polymer, gelatinization of the starch and the like), but the methods for modifying the starch are either complex in preparation or not ideal in modification effect, and the obtained composite material is low in mechanical property and heat generation property.

Disclosure of Invention

In view of the above, the present invention aims to provide a rubber-modified starch composite material. The rubber-modified starch composite material provided by the invention has excellent mechanical properties and low heat generation; the invention also provides a preparation method of the rubber-modified starch composite material.

In order to achieve the purpose of the invention, the invention provides the following technical scheme:

the invention provides a rubber-modified starch composite material which comprises the following preparation raw materials in parts by mass:

100 parts of natural rubber;

1-50 parts of starch;

0.1-10 parts of epoxidized natural rubber;

0.2-12 parts of a vulcanization processing aid;

the natural rubber and the epoxidized natural rubber are calculated by dry rubber.

Preferably, the epoxidation degree of the epoxidized natural rubber is 2-50.

Preferably, the starch is one or more of tapioca starch, corn starch and rice starch.

Preferably, the vulcanization processing aid is a mixture of sulfur, N-tert-butyl-2-benzothiazole sulfonamide, zinc oxide and stearic acid.

Preferably, the mass ratio of the sulfur, the N-tert-butyl-2-benzothiazole xanthamide, the zinc oxide and the stearic acid is (1-3): (0.5-2): (3-5): (1-3).

The invention also provides a preparation method of the rubber-modified starch composite material, which comprises the following steps:

mixing and modifying the starch aqueous solution and the epoxidized natural rubber to obtain modified starch aqueous dispersion;

mixing the modified starch aqueous dispersion and natural rubber, and then sequentially performing solidification treatment and drying to obtain a composite material precursor;

and mixing the composite material precursor with a vulcanization processing aid, and then vulcanizing to obtain the rubber-modified starch composite material.

Preferably, the concentration of the starch aqueous solution is 10-20 wt.%.

Preferably, the temperature of the mixing modification is 40-80 ℃, and the time is 5-60 min; the mixing modification is carried out under the conditions of ultrasound and stirring; the power of the ultrasonic wave is 700-1000W; the rotating speed of the stirring is 200-400 rpm.

Preferably, the coagulation treatment is performed by acetic acid coagulation, formic acid coagulation, steam coagulation or calcium chloride coagulation.

Preferably, the vulcanization temperature is 140-150 ℃.

The invention provides a rubber-modified starch composite material which comprises the following preparation raw materials in parts by mass: 100 parts of natural rubber; 1-50 parts of starch; 0.1-10 parts of epoxidized natural rubber; 0.2-12 parts of a vulcanization processing aid; the natural rubber and the epoxidized natural rubber are calculated by dry rubber. In the invention, the epoxy group in the epoxidized natural rubber latex can react with the hydroxyl group in the starch to modify the starch, which is beneficial to improving the dispersibility of the starch in the natural rubber and further beneficial to improving the mechanical property and the heat generation property of the rubber-modified starch composite material.

Experimental results show that the tensile strength of the rubber-modified starch composite material is 27.86-29.81 MPa, the tear strength is 38.3-39.7 MPa, and the mechanical property is excellent; the compression fatigue temperature rise is 19-22 ℃, and the heat generation is low.

The invention also provides a preparation method of the rubber-modified starch composite material, the preparation method provided by the invention uses epoxidized natural rubber to modify starch, improves the dispersibility of the starch, and then mixes the obtained modified starch and the natural rubber for curing treatment to preliminarily form a disperse system composite material precursor with the uniform blending of the natural rubber and the modified starch; and finally, mixing and vulcanizing the obtained composite material precursor to obtain the rubber-modified starch composite material. The preparation method provided by the invention has the advantages of simple steps, low cost and easiness for large-scale production.

Detailed Description

The invention provides a rubber-modified starch composite material which comprises the following preparation raw materials in parts by mass:

100 parts of natural rubber;

1-50 parts of starch;

0.1-10 parts of epoxidized natural rubber;

0.2-12 parts of a vulcanization processing aid;

the natural rubber and the epoxidized natural rubber are calculated by dry rubber.

In the present invention, unless otherwise specified, commercially available products well known to those skilled in the art are used for each component in the preparation method.

The raw materials for preparing the rubber-modified starch composite material comprise 100 parts by mass of natural rubber. In the invention, the mass parts of the natural rubber are calculated by dry rubber. In the present invention, the natural rubber is preferably a milky natural rubber. In the invention, the solid content of the milky natural rubber is preferably 20-30%, and more preferably 23-27%. In the present invention, the natural rubber is a natural polymer compound containing cis-1, 4-polyisoprene as a main component, and the rubber hydrocarbon (cis-1, 4-polyisoprene) content thereof is 90% or more, and further contains a small amount of proteins, fatty acids, sugars, ash, and the like; the source of the natural rubber is not particularly required in the present invention, and natural rubber from sources well known to those skilled in the art, specifically, commercially available natural rubber, may be used. The invention adopts natural rubber as a base material.

The preparation raw materials of the rubber-modified starch composite material comprise 1-50 parts of starch, preferably 5-40 parts of starch, and more preferably 10-30 parts of starch by mass. In the present invention, the starch is preferably one or more of tapioca starch, corn starch and rice starch.

The preparation raw materials of the rubber-modified starch composite material comprise, by mass, 0.1-10 parts of epoxidized natural rubber, preferably 0.5-8 parts, and more preferably 1-6 parts of natural rubber. In the invention, the epoxidation degree of the epoxidized natural rubber is preferably 2-50, more preferably 10-40, and still more preferably 15-30. In the present invention, the mass parts of the epoxidized natural rubber are in terms of dry rubber. In the present invention, the epoxidized natural rubber is preferably a milky epoxidized natural rubber. In the invention, the solid content of the milky epoxidized natural rubber is preferably 10-20%, and more preferably 12-18%. In the invention, the epoxy group in the epoxidized natural rubber can react with the hydroxyl group in the starch, so that the reaction degree of the starch and the epoxy group in the epoxidized natural rubber is improved, the dispersibility of the starch in the natural rubber is favorably improved, and the mechanical property and the heat generation property of the rubber-modified starch composite material are favorably improved. The source of the epoxidized natural rubber is not particularly limited in the present invention so as to satisfy the epoxidation degree of the epoxidized natural rubber, and specifically, it is commercially available.

The preparation raw materials of the rubber-modified starch composite material comprise, by mass, 0.2-12 parts of a vulcanization processing aid, preferably 1-10 parts, and more preferably 3-7 parts. In the present invention, the vulcanization processing aid is preferably a mixture of sulfur, N-tert-butyl-2-benzothiazolesulfenamide (accelerator NS), zinc oxide and stearic acid. In the invention, the mass ratio of the sulfur, the N-tertiary butyl-2-benzothiazole xanthic amide, the zinc oxide and the stearic acid is preferably (1-3): (0.5-2): (3-5): (1-3), more preferably (1.5-2.5): (0.7-1.5): (4-4.5): (1.5-2). When the vulcanization processing aid is other combinations in the types, the proportion of the different vulcanization processing aids is not specially limited and can be any proportion. The invention utilizes the vulcanization processing aid to enable the natural rubber composite material to form a three-dimensional network structure, and ensures the basic structure and the mechanical property of the rubber-modified starch composite material. .

The invention also provides a preparation method of the rubber-modified starch composite material, which comprises the following steps:

mixing and modifying the starch aqueous solution and the epoxidized natural rubber to obtain modified starch aqueous dispersion;

mixing the modified starch aqueous dispersion and natural rubber, and then sequentially performing solidification treatment and drying to obtain a composite material precursor;

and mixing the composite material precursor with a vulcanization processing aid, and then vulcanizing to obtain the rubber-modified starch composite material.

In the invention, the components in the preparation method are consistent with those in the raw materials for preparing the rubber-modified starch composite material in the technical scheme, and are not described again.

The invention mixes and modifies starch aqueous solution and epoxidized natural rubber to obtain modified starch aqueous dispersion.

In the invention, the concentration of the starch aqueous solution is preferably 10-20 wt.%, and more preferably 12-18 wt.%.

In the present invention, the method for preparing the aqueous starch solution preferably comprises the steps of:

dispersing starch in water, and sequentially carrying out homogenization treatment and high-speed jet treatment to obtain a starch solution.

In the present invention, the water is preferably deionized water. In the present invention, the equipment for the homogenization treatment is preferably a high-pressure homogenizer. In the invention, the pressure of the homogenization treatment is preferably 40-60 MPa, and more preferably 43-57 MPa; the temperature is preferably 25-30 ℃, and more preferably 26-29 ℃; the time for each time is preferably 15-30 min, and more preferably 20-25 min. In the present invention, the number of homogenization treatments is preferably 1 to 3. In the present invention, the high-speed jet processing apparatus is preferably a high-speed jet machine. In the invention, the pressure of the high-speed jet flow treatment is preferably 200-240 MPa, more preferably 210-230 MPa, and the time is preferably 50-80 min/time, more preferably 55-75 min/time. In the invention, the number of times of the high-speed jet treatment is preferably 1 to 3. The invention destroys the structure of the starch by the mechanical acting force of the homogenization treatment and the high-speed jet flow treatment, improves the solubility of the starch, increases the granularity, further changes the particle shape and the crystal structure of the starch, is beneficial to improving the reactivity of hydroxyl in the starch and epoxy groups in the epoxidized natural rubber, and is beneficial to improving the dispersibility of the starch in the natural rubber.

In the invention, the mixing modification temperature is preferably 40-80 ℃, and more preferably 40-60 ℃; the time is preferably 5 to 60min, and more preferably 10 to 40 min. In the present invention, the mixing modification is preferably performed under the conditions of ultrasound and stirring. In the invention, the power of the ultrasonic wave is preferably 700-1000W, and more preferably 800-950W; the rotation speed of the stirring is preferably 200-400 rpm, and more preferably 250-350 rpm. In the present invention, the mixing modification is preferably performed under the condition of a water bath. The invention is mixed and modified under the conditions, which is beneficial to ensuring that all components are fully mixed, and the hydroxyl in the starch and the epoxy group in the epoxidized natural rubber are fully interacted in water, thereby being beneficial to improving the dispersibility of the starch in the natural rubber matrix.

After the modified starch aqueous dispersion is obtained, the modified starch aqueous dispersion and the natural rubber are mixed, and then are subjected to solidification treatment and drying in sequence to obtain the composite material precursor.

In the invention, the mixing temperature is preferably 40-80 ℃, and more preferably 40-60 ℃; the time is preferably 5 to 60min, and more preferably 10 to 40 min. In the present invention, the mixing is preferably performed under conditions of sonication and stirring. In the invention, the power of the ultrasonic wave is preferably 700-1000W, and more preferably 800-950W; the rotation speed of the stirring is preferably 200-400 rpm, and more preferably 250-350 rpm. The invention improves the dispersibility of the starch by mixing.

In the present invention, the coagulation treatment is preferably performed by acetic acid coagulation, formic acid coagulation, steam coagulation, or calcium chloride coagulation. In the invention, the volume concentration of acetic acid in the acetic acid coagulation is preferably 0.5-0.7%, and more preferably 0.55-0.65%. In the present invention, the mass of the natural rubber is calculated as dry rubber, and in the mixed system of the modified starch aqueous dispersion and the natural rubber, the mass ratio of the natural rubber to the acetic acid is preferably 100: (0.5 to 1), more preferably 100: (0.6-0.9). In the invention, the volume concentration of formic acid in the formic acid coagulation is preferably 0.6-1.0%, and more preferably 0.7-0.9%. In the present invention, the mass of the natural rubber is calculated as dry rubber, and in the mixed system of the modified starch aqueous dispersion and the natural rubber, the mass ratio of the natural rubber to formic acid is preferably 100: (0.3 to 0.5), more preferably 100: (0.35-0.45). In the present invention, the steam for steam coagulation is water vapor. In the invention, the mass percentage of the calcium chloride in the calcium chloride solidification is preferably 8-10%, and more preferably 8.5-9.5%. In the present invention, the mass of the natural rubber is calculated as dry rubber, and in the mixed system of the modified starch water dispersion and the natural rubber, the mass ratio of the natural rubber to the calcium chloride is preferably 100: (0.3 to 0.5), more preferably 100: (0.35-0.45). In the invention, the time of the solidification treatment is preferably 1 to 6 hours, and more preferably 2 to 5 hours.

In the present invention, the drying is preferably hot air drying. In the invention, the drying temperature is preferably 50-100 ℃, and more preferably 70-90 ℃; the time is preferably 2 to 48 hours, and more preferably 15 to 38 hours.

After the composite material precursor is obtained, the composite material precursor and a vulcanization processing aid are mixed and vulcanized to obtain the rubber-modified starch composite material.

The present invention is not particularly limited to the above-mentioned mixing, and mixing known to those skilled in the art may be employed.

In the invention, the vulcanization temperature is preferably 140-150 ℃, and more preferably 142-148 ℃. The invention preferably stands for 12 hours after the mixing is finished, measures the optimal vulcanization time of the obtained mixed material, and then vulcanizes the mixed material according to the determined vulcanization time; the method for measuring the optimum vulcanization time of the compounded material in the present invention is not particularly limited, and a method known to those skilled in the art may be used, specifically, the method is measured using a vulcanizer.

The modified starch aqueous dispersion and the natural rubber are mixed under a liquid condition, so that the interaction of groups in each component can be fully ensured, the modified starch is uniformly dispersed in the natural rubber, the mixed material of the modified starch aqueous dispersion and the natural rubber is solidified and dried to prepare a composite material precursor in a dry rubber state, and then the composite material precursor is mixed and vulcanized with a vulcanization processing aid, so that the starch in the finally obtained rubber-modified starch composite material is uniformly dispersed, the mechanical property of the rubber-modified starch composite material is favorably improved, and the heat generation property is reduced.

The rubber-modified starch composite material provided by the invention has excellent performances of low heat generation, high tear, fatigue resistance and the like, and can be used for preparing high-performance green tires, medical latex products or epoxidized natural rubber products such as soles and the like.

In order to further illustrate the present invention, the rubber-modified starch composite material and the preparation method thereof provided by the present invention will be described in detail with reference to the following examples, which should not be construed as limiting the scope of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.