Preparation method and application of special natural rubber particles

Abstract

The invention provides a preparation method and application of special natural rubber particles, and the preparation method comprises the following steps: filtering fresh latex twice, uniformly mixing, adding serine protease and water for dilution, stirring to obtain diluted latex, mixing a formic acid solution with the diluted latex to obtain a latex mixture, curing and solidifying the latex mixture, thinning and dehydrating, and crushing and granulating to obtain the special natural rubber particles. And boxing the latex particles, dripping water, discharging, drying, weighing, grading and packaging. According to the prepared special rubber, the rubber quality is improved, the elongation at break, the tensile strength and the stress at definite elongation of 500% are improved, the Mooney viscosity is larger than 85, the impurity content is smaller than 0.04%, the ash content is smaller than 0.4%, good physical performance is achieved, and the requirements of tire customers are met.

Description

Technical Field

[0001] The invention relates to the field of rubber preparation, and in particular to a preparation method and application of special natural rubber particles. Background Art

[0002] The invention discloses a preparation method and application of special natural rubber particles. At present, there are two main forms of raw materials for producing special natural rubber, one is liquid fresh latex and the other is solid coagulated rubber raw material coagulated naturally in the field or by rubber farmers adding part of acid. The products processed from these two raw materials have great differences in performance indicators. The other is a natural rubber product mixed with fresh latex raw materials. Its initial plasticity value (P0), plasticity retention index (PRI), impurity content and ash content are low. Although it can meet the requirements of ordinary tire factories, the tensile strength, elongation at break and 500% tensile stress of vulcanized rubber at 140℃×40min cannot meet the product requirements. In addition, the production of special natural rubber with coagulated rubber raw materials has large differences in each batch of coagulated rubber raw materials, and the impurity content of the produced rubber exceeds 0.05%. The initial plasticity value (P0) and plasticity retention index (PRI) are low and cannot meet the requirements of the manufacturing plant.

[0003] Special natural rubber refers to a standard rubber form used in the preparation of products. Compared with ordinary standard rubber, in addition to meeting general performance requirements, it has higher requirements in terms of Mooney viscosity of raw rubber and tensile strength of vulcanized rubber. In recent years, my country has carried out research on aircraft tire rubber, mainly by using technologies such as bio-coagulation and blending of supporting raw materials to improve the tensile properties of standard rubber to meet the needs of aircraft tire rubber production. However, this method has the disadvantages of poor consistency, large batch differences, high power consumption, high labor intensity, and high production costs. Summary of the invention

[0004] In view of this, the present invention develops a preparation method and application of special natural rubber particles.

[0005] The technical solution of the present invention is achieved in this way:

[0006] A method for preparing special natural rubber particles comprises the following steps:

[0007] S1. Filter the fresh latex twice, mix well, add water and enzyme to hydrolyze, stir to obtain diluted latex,

[0008] S2. mixing the formic acid solution with the diluted latex to obtain a latex mixture,

[0009] S3. The latex mixture is matured and coagulated, pressed and dehydrated, crushed and granulated to obtain latex particles,

[0010] S4. Pack the latex particles into boxes, drip water, unload the vehicle, dry, weigh, grade and package.

[0011] Furthermore, S1, the two filtrations are performed, the first filtration is performed through a 40-60 mesh screen, and the second filtration is performed through a filter, and the filter speed is 1000-1500 rpm.

[0012] Furthermore, S1, the dilution is performed by adding water so that the rubber content in the fresh latex after adding water is controlled at 21%-23%.

[0013] Furthermore, S1, the enzyme is serine protease, and the diluted enzymolysis further adds asparagine and adenine, the mass ratio of fresh latex to serine protease, asparagine and adenine is 100:(0.06-0.08):(0.003-0.005):(0.001-0.004), the enzymolysis temperature is 53-55°C, and the enzymolysis pH is 9-11.

[0014] Further, S2, the formic acid solution is mixed with the diluted latex, the mass fraction of the formic acid solution is 4-5wt%, and the mass ratio of the fresh latex to the formic acid solution is 100:(0.6-0.7).

[0015] Furthermore, S3, the aging and coagulation, the pH value of the latex mixture is adjusted to 7.5-8 using a formic acid solution, and the aging and coagulation time is 48-55h.

[0016] Furthermore, S3, the pressing and dehydration, pressing the matured and coagulated latex curd into a film with a thickness of 5-6 cm, and the film is pressed into a film with a thickness of 4-5 mm by three creping machines.

[0017] Furthermore, S4, the dripping makes the water content of the latex particles less than 32%, the drying time of the latex particles is 8-9 hours, the front end temperature of the dryer is 110-116°C, and the rear end temperature is 90-105°C, and the temperature of the glue when leaving the vehicle is lower than 50°C.

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

[0019] In the process of making the special natural rubber particles of the present invention, the purity of the fresh latex is further improved by two different filtrations and impurities removal, and the viability and activity of the serine protease are enhanced by adding asparagine and adenine to the serine protease, so that the serine protease reacts with the protein in the natural rubber to achieve a better deproteinization effect and significantly improve the performance of the rubber. The preparation method of the present invention improves the quality of the rubber, the elongation at break, the tensile strength and the 500% tensile stress of the rubber, the Mooney viscosity of the rubber is greater than 85, the impurity content is less than 0.04%, the ash content is less than 0.4%, the rubber has good physical properties, and can effectively improve the consistency and stability of the natural rubber. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 :Production flow chart of special natural rubber particles DETAILED DESCRIPTION

[0021] In order to better understand the technical content of the present invention, specific examples are provided below to further illustrate the present invention. The experimental methods used in the examples of the present invention are all conventional methods unless otherwise specified.

[0022] Unless otherwise specified, the materials, reagents, etc. used in the embodiments of the present invention can be obtained from commercial sources.

[0023] The raw materials of the fresh latex of the present invention are: produced by rubber trees of Reyan 7-33-97 strain;

[0024] The activity of serine protease is greater than 2 million U / mg, and the manufacturer is Shanghai Hongshun Biotechnology Co., Ltd.;

[0025] Asparagine, HPLC ≥ 98%, Hainan Xingshengfa Chemical Technology Co., Ltd.;

[0026] Adenine, purity 99.5%, Shanghai Yiyan Biotechnology Co., Ltd.

[0027] Example 1

[0028] A method for preparing special natural rubber particles is as follows:

[0029] (1) fresh latex produced by rubber trees of the 7-33-97 strain of Reyan is selected for pretreatment, and after the pretreatment, a water-line preparation process is adopted to obtain special natural rubber particles. The pretreatment comprises the following steps: after checking the appearance quality of the fresh latex, filtering the fresh latex without corruption and deterioration twice, filtering through a 40-mesh sieve and then filtering through a 1500 rpm filter, determining the dry rubber content and calculating the dilution water amount, the dry rubber content of the fresh latex is controlled at 21%, adding water and serine protease, and adding asparagine and adenine at the same time, stirring evenly, the enzymolysis temperature is 53° C., the pH value is 9, wherein the mass ratio of the fresh latex to the serine protease, asparagine and adenine is 100:0.06:0.003:0.001, and dilute latex is obtained.

[0030] (2) Sampling to determine the dry rubber content and ammonia content, and calculating the final amount of formic acid used for coagulation. The mass fraction of the formic acid solution is 4wt%. The formic acid solution is added to the diluted latex according to the mass ratio of fresh latex to formic acid solution of 100:0.6 to obtain a latex mixture.

[0031] (3) The latex mixture is added to a long tank and then coagulated, the pH value is 7.5, and the ripening and coagulation time is 48 hours. The matured coagulate is pressed into a 5-cm thick film by a double-roll thinning machine, and the film is pressed into a 4-mm film by three creping machines, and then crushed and granulated by a granulator to obtain latex particles.

[0032] (4) The latex particles are packed and dripped with water (water content 15%), and then dried for 8 hours (front end 110°C, rear end 90°C), and then taken out of the vehicle with a glue temperature of 20°C, weighed and packaged to obtain the finished product.

[0033] Example 2

[0034] A method for preparing special natural rubber particles is as follows:

[0035] (1) fresh latex produced by rubber trees of the Reyan 7-33-97 strain is selected for pretreatment, and after the pretreatment, a water-line preparation process is adopted to obtain special natural rubber particles. The pretreatment comprises the following steps: after checking the appearance quality of the fresh latex, filtering the fresh latex without corruption and deterioration twice, filtering through a 60-mesh sieve and then filtering through a 1000 rpm filter, determining the dry rubber content and calculating the amount of water added for dilution, the dry rubber content of the fresh latex is controlled at 23%, adding water and serine protease, and adding asparagine and adenine at the same time, stirring evenly, the enzymolysis temperature is 55° C., the pH value is 11, wherein the mass ratio of the fresh latex to the serine protease, asparagine and adenine is 100:0.08:0.003:0.001, and dilute latex is obtained.

[0036] (2) Sampling to determine the dry rubber content and ammonia content, and calculating the final amount of formic acid used for coagulation. The mass fraction of the formic acid solution is 5wt%. The formic acid solution is added to the diluted latex according to the mass ratio of fresh latex to formic acid solution of 100:0.7 to obtain a latex mixture.

[0037] (3) The latex mixture is added to a long tank and then coagulated, with a pH value of 8 and a ripening and coagulation time of 55 hours. The ripened coagulate is thinned to a 6-cm thick film by a double-roll thinning machine, and the film is thinned to a 5-mm film by three creping machines, and then crushed and granulated by a granulator to obtain latex particles.

[0038] (4) The latex particles are packed and dripped with water (water content 13%), and then dried for 9 hours (front end 116° C., rear end 105° C.), and then taken out of the vehicle with a glue temperature of 25° C., weighed and packaged to obtain the finished product.

[0039] Example 3

[0040] A method for preparing special natural rubber particles is as follows:

[0041] (1) fresh latex produced by rubber trees of the Reyan 7-33-97 strain is selected for pretreatment, and after the pretreatment, a waterline preparation process is used to obtain special natural rubber particles. The pretreatment comprises the following steps: after checking the appearance quality of the fresh latex, filtering the fresh latex without corruption and deterioration twice, filtering through a 50-mesh sieve and then filtering through a 1300 rpm filter, determining the dry rubber content and calculating the amount of water added for dilution, the dry rubber content of the fresh latex is controlled at 22%, adding water and serine protease, and adding asparagine and adenine at the same time, stirring evenly, the enzymolysis temperature is 54° C., the pH value is 11, wherein the mass ratio of the fresh latex to the serine protease, asparagine and adenine is 100:0.07:0.004:0.002, and a diluted latex is obtained.

[0042] (2) Sampling was performed to determine the dry rubber content and ammonia content, and the final amount of formic acid used for coagulation was calculated. The mass fraction of the formic acid solution was 4.5 wt %. The formic acid solution was added to the diluted latex according to the mass ratio of fresh latex to formic acid solution of 100:0.6 to obtain a latex mixture.

[0043] (3) The latex mixture is added to a long tank and then coagulated, the pH value is 7.8, and the ripening and coagulation time is 50 hours. The matured coagulate is pressed into a 5-cm thick film by a double-roll thinning machine, and the film is pressed into a 4-mm film by three creping machines, and then crushed and granulated by a granulator to obtain latex particles.

[0044] (4) The latex particles are packed and dripped with water (water content 15%), and then dried for 8 hours (front end 110°C, rear end 90°C), and then shipped out with the glue temperature of 15°C, and weighed and packaged.

[0045] Comparative Example 1

[0046] The main difference between Comparative Example 1 and Example 3 is that the second filtration is replaced by 1300 rpm filter filtration, and the 50-mesh sieve filtration is removed. All other preparation methods are the same as Example 3.

[0047] Comparative Example 2

[0048] The main differences between Comparative Example 2 and Example 3 are that the serine protease enzymatic hydrolysis and the step of adding asparagine and adenine by enzymatic hydrolysis are removed, and all other preparation methods are the same as those in Example 3.

[0049] Comparative Example 3

[0050] The main difference between Comparative Example 3 and Example 3 is that the formic acid solution is removed to adjust the pH value, and all other preparation methods are the same as Example 3.

[0051] Comparative Example 4

[0052] The main difference between Comparative Example 4 and Example 3 is that the operation step of thinning the film by the double-roll thinning machine is removed, and all other preparation methods are the same as those in Example 3.

[0053] test

[0054] The present invention uses the fresh latex raw material produced by the rubber tree of the Reyan 7-33-97 strain to process the special natural rubber product, and the rubber plantation management of the strain is strictly managed according to the special rubber plantation demonstration standard. The rubber powder produced by the method of embodiment 1-3 is measured for product performance, and the measurement index and measurement reference standard are shown in Table 1.

[0055] The maximum impurity content of the special natural rubber particles produced by the methods of Examples 1-3 is in the range of 0.038-0.040%, the maximum ash content is in the range of 0.39-0.40%, the volatile matter is lower than 0.8%, and the Mooney viscosity is higher than 85%. The special natural rubber particles produced by the methods of Examples 1-3 can effectively improve the consistency and stability of natural rubber and meet product requirements.

[0056] Table 1

[0057]

[0058] The rubber powder produced by the method of comparative examples 1-4 was tested for product performance, and the test indicators and test reference standards are shown in Table 2. The consistency and stability of the special natural rubber products produced by the method of comparative examples 1-4 are lower than those of examples 1-3, the maximum impurity content ranges from 0.052-0.064%, which is higher than 0.038-0.040% of examples 1-3, the maximum ash content ranges from 0.52-0.74%, which is higher than 0.39-0.40% of examples 1-3, and the minimum Mooney viscosity of 80% is far lower than 85%. The product requirements cannot be met.

[0059] Table 2

[0060]

[0061]

[0062] Test results: In the production of the special natural rubber particles of the present invention, sieve filtration and filter filtration are used in turn to remove impurities, which improves the purity of the fresh latex. The addition of serine protease reacts with the protein in the natural rubber. At the same time, asparagine and adenine are added to maintain the viability and activity of the serine protease, achieving a better deproteinization effect. The formic acid solution adjusts the pH value of the latex mixture, controls the aging and coagulation time, and the film is pressed into a 4-5mm film by 3 crepe machines. This combination of operation steps significantly improves the performance of the rubber. The special rubber prepared by the present invention improves the quality of rubber, the elongation at break, the tensile strength and the 500% tensile stress, the Mooney viscosity is greater than 85, the impurity content is less than 0.04%, the ash content is less than 0.4%, the volatile content is reduced, the physical properties are improved, the consistency and stability of the rubber are improved, and the high-quality tire customer needs can be met.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing special natural rubber particles, characterized in that: The production steps include: S1. The fresh latex was filtered twice, mixed evenly, water and enzyme were added, enzymatically hydrolyzed, and stirred to obtain diluted latex; S2. mixing the formic acid solution with the diluted latex to obtain a latex mixture; S3. The latex mixture is matured and coagulated, thinned and dehydrated, crushed and granulated to obtain latex particles; S4. Pack the latex particles into boxes, drip water, unload the vehicle, dry, weigh, grade and package.

2. The method for preparing special natural rubber particles according to claim 1, characterized in that: S1, the two filtrations, the first filtration is 40-60 mesh sieve filtration, the second filtration is filter filtration, the filter speed is 1000-1500 rpm.

3. The method for preparing special natural rubber particles according to claim 1, characterized in that: S1, the dilution is performed by adding water so that the rubber content in the fresh latex after adding water is controlled at 21%-23%.

4. The method for preparing special natural rubber particles according to claim 1, characterized in that: S1, the enzyme is serine protease, and asparagine and adenine are added after the enzyme is added, the mass ratio of fresh latex to serine protease, asparagine and adenine is 100:(0.06-0.08):(0.003-0.005):(0.001-0.004), the enzymolysis temperature is 53-55°C, and the enzymolysis pH is 9-11.

5. The method for preparing special natural rubber particles according to claim 1, characterized in that: S2, the formic acid solution is mixed with the diluted latex, the mass fraction of the formic acid solution is 4-5wt%, and the mass ratio of the fresh latex to the formic acid solution is 100:(0.6-0.7).

6. The method for preparing special natural rubber particles according to claim 1, characterized in that: S3, the ripening and coagulation, using formic acid solution to adjust the pH value of the latex mixture to 7.5-8, the ripening and coagulation time is 48-55h.

7. The method for preparing special natural rubber particles according to claim 1, characterized in that: S3, the pressing and dehydration, pressing the matured and coagulated latex clots into a film with a thickness of 5-6 cm, and pressing the film into a film with a thickness of 4-5 mm through three creping machines.

8. The method for preparing special natural rubber particles according to claim 1, characterized in that: S4, the dripping makes the water content of the latex particles less than 32%; the drying process: the latex particles are dried for 8-9 hours, the front end temperature of the dryer is 110-116°C, and the rear end temperature is 90-105°C; the glue temperature is lower than 50°C when the vehicle is discharged.

9. The special natural rubber particles prepared by the preparation method according to any one of claims 1 to 8 are used in rubber tires.

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