Natural rubber raw material curing process

Abstract

The invention provides a natural rubber raw material curing process which comprises the following steps: (1) sorting and crushing collected cup rubber, adding an oxalic acid solution of which the mass is 10-12% of that of the cup rubber, stirring, transferring to a wet stirrer for primary rubbing, and then adding an oxalic acid solution of which the mass is 5-8% of that of the cup rubber for secondary rubbing to obtain a pretreated rubber raw material; and (2) carrying out multi-stage crepe pressing on the pretreated rubber raw material, and then carrying out stockpiling and curing treatment to obtain the cured rubber raw material. The natural rubber curing process is subjected to segmented treatment, and after the natural rubber is smashed in a rubber cup and impurities are removed, an oxalic acid solution is added for stirring and rubbing, and multiple times of crepe pressing treatment are performed; the rubber cup is crushed, impurities of the rubber raw materials are fully removed, all the rubber raw materials are in the same physical property state after multiple times of crepe pressing, and the performance of the rubber raw materials can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of rubber processing, in particular to a natural rubber raw material ripening process. Background Art

[0002] Natural rubber is irreplaceable in national fields such as military equipment, aerospace, and marine engineering, and is an important strategic material. From the perspective of the rubber products market size, the natural rubber industry chain has huge room for value-added.

[0003] China's natural rubber harvesting faces the current situation of difficult work for rubber tappers and a significant gap in personnel supply; after the natural rubber is harvested and becomes "cup rubber", there is a problem of poor storage process, resulting in significant loss of raw materials; and in the process of removing impurities and dehydrating natural rubber, there is a problem of no standardized equipment and process, which affects both production capacity and the quality of process products (such as rubber crepes). Ultimately, the output and quality of primary processed rubber products, such as various grades of rubber TSR (Technical Specified Rubber), will be affected by the above multiple factors.

[0004] After natural rubber is tapped and collected to become cup rubber (Cup Lump), the stacking position will cause different pressures, temperatures and humidity on each rubber cup, which will lead to different degrees of maturation of natural rubber in different rubber cups. Even in the same rubber cup, there will be different maturation. In the traditional rubber making process, after the cup rubber is crushed, it will be processed later, causing rubber raw materials with different maturation degrees to enter the primary processing process. Ultimately, the quality of the primary processed finished product standard rubber (TSR) will vary, resulting in a waste of natural rubber raw materials. Even if the output standard rubber passes the inspection, there is a phenomenon that key indicators (such as: plasticity retention coefficient PRI) are significantly reduced after long-term placement; affecting the quality of the finished product of mixed rubber produced with this as raw material in the later stage. Summary of the invention

[0005] In view of this, the present invention proposes a natural rubber raw material aging process, which can make the rubber raw materials in the same physical property state, facilitate the subsequent aging and long-distance transportation of the rubber raw materials, thereby improving the product quality of crude rubber processing.

[0006] The technical solution of the present invention is achieved in this way:

[0007] A natural rubber raw material ripening process comprises the following steps:

[0008] (1) sorting and crushing the collected cup rubber, adding 10-12% oxalic acid solution of the cup rubber mass, stirring, moving to a wet mixer for primary kneading, and then adding 5-8% oxalic acid solution of the cup rubber mass for secondary kneading to obtain a pretreated rubber raw material;

[0009] (2) The pretreated rubber raw material is subjected to multi-stage creping in sequence using a deep-grain crepe machine, a medium-grain crepe machine, and a shallow-grain crepe machine, and then subjected to a stacking and aging treatment to obtain an aged rubber raw material.

[0010] Furthermore, the concentration of the oxalic acid solution is 0.5-2.0 wt %.

[0011] Furthermore, in step (1), the stirring process is: first stirring at a speed of 200-500 r / min for 15-30 min, standing for 6-8 min, then stirring at a speed of 600-800 r / min for 12-16 min, standing for 6-8 min, and finally stirring at a speed of 200-300 r / min for 10-12 min, standing for 20-30 min.

[0012] Furthermore, in step (1), the kneading process is: kneading for 4 to 8 minutes at a wet mixer speed of 300 to 600 r / min, then turning on the spray water at 6 to 10 L / min·m to knead and clean for 10 to 15 minutes, and repeating 2 to 3 times.

[0013] Furthermore, in step (1), the secondary kneading process is: kneading for 3 to 6 minutes at a wet mixer speed of 600 to 800 r / min, then turning on the spray water at 3 to 5 L / min·m to knead and clean for 8 to 12 minutes, and repeating 2 to 3 times.

[0014] Furthermore, in step (2), the creping thickness of the deep-grain crepe machine is 2 to 3 cm, and the creping is repeated 2 to 3 times; the creping thickness of the medium-grain crepe machine is 1.2 to 1.8 cm, and the creping is repeated 2 to 3 times; the creping thickness of the shallow-grain crepe machine is 0.5 to 0.8 cm, and the creping is repeated 3 to 4 times.

[0015] Furthermore, the stacking and aging process is: the rubber raw materials after creping are stacked and aged at 40-50° C. for 1-3 days.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. Natural rubber is produced into cup rubber by tapping and collecting. The present invention adopts a method of adding oxalic acid solution to the sorted and broken rubber cups for stirring, kneading and multi-stage creping, so that the rubber raw materials can be mixed more evenly and maintain a uniform degree of maturation, thereby improving the quality of the rubber raw materials and facilitating subsequent processing or transportation.

[0018] 2. The present invention processes the natural rubber maturation process in stages. After the rubber cup is crushed and impurities are removed, oxalic acid is added and stirred, and then kneaded and creped several times. After creping, it is stored and matured. Since the rubber cup is broken, the raw materials can be fully impurities removed. After several crepings, all rubber raw materials are in the same physical property state, so that the rubber raw materials are stored and matured or transported over long distances, which will not affect the relevant physical property indicators of the rubber rough processing process products (crepe sheets). In addition, the standard rubber (TSR) processed from the matured process products (crepe sheets) of the present invention has stable physical property indicators, and the quality of the mixed rubber can be guaranteed.

[0019] 3. In the process of treating the rubber raw materials, the present invention adds oxalic acid solution and sets different stirring conditions for the rubber cup raw materials, which can promote the penetration of oxalic acid solution into the rubber raw materials, improve the stability of the rubber raw materials, and facilitate the changes in the molecular chains of the rubber raw materials during storage. At the same time, it also effectively improves the structural performance, so that the physical properties of the rubber raw materials are uniform, and at the same time, the physical properties of the raw materials are improved, especially the antioxidant capacity is improved, which is convenient for subsequent processing; then the stirred rubber raw materials are placed in a wet mixer for kneading, and through the first kneading, the second kneading and spraying, the ash and impurities in the rubber raw materials can be cleaned and removed, the purity of the rubber raw material product and the consistency of the material are improved, and the rubber raw materials have good softness and hardness, which is convenient for crimping, thereby improving the quality of the rubber; the multi-stage crimping method can effectively improve the quality of the rubber raw materials.

[0020] 4. The present invention stirs, kneads and crepes the cup rubber several times under different process conditions, which can improve the performance of the rubber raw material and also make the performance of the rubber raw material consistent, which is convenient for subsequent processing and transportation of the rubber raw material. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Flow chart of the rubber raw material ripening process of the present invention. DETAILED DESCRIPTION

[0022] In order to better understand the technical content of the present invention, specific embodiments are provided below to further illustrate the present invention.

[0023] Unless otherwise specified, the experimental methods used in the embodiments of the present invention are all conventional methods.

[0024] Unless otherwise specified, the materials, reagents, etc. used in the embodiments of the present invention can be obtained from commercial sources.

[0025] Embodiment 1:

[0026] The natural rubber raw material ripening process of this embodiment comprises the following steps:

[0027] (1) The collected cup rubber is sorted and crushed, and an oxalic acid solution with a concentration of 0.5wt% of 10% of the mass of the cup rubber is added, and the mixture is stirred at a speed of 200r / min for 15min, and then allowed to stand for 6min. Then, the mixture is stirred at a speed of 600r / min for 12min, and allowed to stand for 6min. Finally, the mixture is stirred at a speed of 200r / min for 10min, and allowed to stand for 20min. The mixture is then moved to a wet mixer and kneaded at a speed of 300r / min for 4min, and sprayed with water at 6L / min·m for kneading and washing for 10min, and the mixture is repeated twice. Then, an oxalic acid solution with a concentration of 0.5wt% of 5% of the mass of the cup rubber is added, and the mixture is kneaded at a speed of 600r / min for 3min, and sprayed with water at 3L / min·m for kneading and washing for 8min, and the mixture is repeated twice to obtain a pretreated rubber raw material;

[0028] (2) The pretreated rubber raw material is creped in turn using a deep-grain crepe machine, a medium-grain crepe machine, and a shallow-grain crepe machine, wherein the creping thickness of the deep-grain crepe machine is 2 cm, and the creping is repeated twice; the creping thickness of the medium-grain crepe machine is 1.2 cm, and the creping is repeated twice; the creping thickness of the shallow-grain crepe machine is 0.5 cm, and the creping is repeated three times; and then the raw material is stacked and aged at 40°C for 1 day to obtain an aged rubber raw material.

[0029] Embodiment 2:

[0030] The natural rubber raw material ripening process of this embodiment comprises the following steps:

[0031] (1) The collected cup rubber is sorted and crushed, and an oxalic acid solution with a concentration of 2.0wt% of the cup rubber mass is added, and the mixture is stirred at a speed of 500r / min for 30min, and then stirred at a speed of 800r / min for 16min, and then stirred at a speed of 300r / min for 12min, and then stirred at a speed of 300r / min for 30min, and then moved to a wet mixer for kneading at a speed of 600r / min for 8min, and then the spray water is turned on to knead and wash for 15min at 10L / min·m, and the mixture is repeated 3 times, and then an oxalic acid solution with a concentration of 2.0wt% of 8% of the cup rubber mass is added at a speed of 800r / min for kneading for 6min, and then the spray water is turned on to knead and wash for 12min at 5L / min·m, and the mixture is repeated 3 times to obtain a pretreated rubber raw material;

[0032] (2) The pretreated rubber raw material is creped in turn using a deep-grain crepe machine, a medium-grain crepe machine, and a shallow-grain crepe machine, wherein the crepe thickness of the deep-grain crepe machine is 3 cm, and the crepe pressing is repeated 3 times; the crepe thickness of the medium-grain crepe machine is 1.8 cm, and the crepe pressing is repeated 3 times; the crepe thickness of the shallow-grain crepe machine is 0.8 cm, and the crepe pressing is repeated 4 times; and then the raw material is stacked and aged at 50°C for 3 days to obtain an aged rubber raw material.

[0033] Embodiment 3:

[0034] The natural rubber raw material ripening process of this embodiment comprises the following steps:

[0035] (1) The collected cup rubber is sorted and crushed, and an oxalic acid solution with a concentration of 1.5wt% of the mass of the cup rubber is added, and the mixture is stirred at a speed of 300 r / min for 20 min, and then stirred at a speed of 700 r / min for 15 min, and then stirred at a speed of 700 r / min for 7 min, and finally stirred at a speed of 200 r / min for 10 min, and then stirred at a speed of 200 r / min for 20 min, and then moved to a wet mixer for kneading at a speed of 500 r / min for 6 min, and then the spray water is turned on to knead and clean for 12 min at 7 L / min·m, and the mixture is repeated 3 times, and then an oxalic acid solution with a concentration of 7% of the mass of the cup rubber is added at a speed of 800 r / min, and the mixture is kneaded for 5 min, and then the spray water is turned on to knead and clean for 10 min at 4 L / min·m, and the mixture is repeated 2 times to obtain a pretreated rubber raw material;

[0036] (2) The pretreated rubber raw material is creped in turn using a deep-grain crepe machine, a medium-grain crepe machine, and a shallow-grain crepe machine, wherein the crepe thickness of the deep-grain crepe machine is 2 cm, and the crepe pressing is repeated 3 times; the crepe thickness of the medium-grain crepe machine is 1.5 cm, and the crepe pressing is repeated 2 times; the crepe thickness of the shallow-grain crepe machine is 0.6 cm, and the crepe pressing is repeated 4 times; and then the raw material is stacked and aged at 40°C for 2 days to obtain an aged rubber raw material.

[0037] Comparative Example 1:

[0038] The difference between this comparative example and Example 3 is that no oxalic acid solution is added for stirring and kneading, and the specific steps are as follows:

[0039] (1) The collected cup rubber is sorted and crushed, and then stirred at a speed of 300 r / min for 20 min, and then allowed to stand for 6 min. Then, it is stirred at a speed of 700 r / min for 15 min, and then allowed to stand for 7 min. Finally, it is stirred at a speed of 200 r / min for 10 min, and then allowed to stand for 20 min. Then, the latex is transferred to a wet mixer and kneaded at a speed of 500 r / min for 6 min, and the spray water is turned on to knead and wash for 12 min at 7 L / min·m, and the kneading is repeated 3 times. At a speed of 800 r / min, it is kneaded for 5 min, and the spray water is turned on to knead and wash for 10 min at 4 L / min·m, and the kneading is repeated 2 times to obtain a pretreated rubber raw material;

[0040] (2) The pretreated rubber raw material is creped in turn using a deep-grain crepe machine, a medium-grain crepe machine, and a shallow-grain crepe machine, wherein the crepe thickness of the deep-grain crepe machine is 2 cm, and the crepe pressing is repeated 3 times; the crepe thickness of the medium-grain crepe machine is 1.5 cm, and the crepe pressing is repeated 2 times; the crepe thickness of the shallow-grain crepe machine is 0.6 cm, and the crepe pressing is repeated 4 times; and then the raw material is stacked and aged at 40°C for 2 days to obtain an aged rubber raw material.

[0041] Comparative Example 2:

[0042] The difference between this comparative example and Example 3 is that the kneading process is different.

[0043] (1) The collected cup rubber is sorted and crushed, and a 1.5wt% oxalic acid solution of 12% of the mass of the cup rubber is added, and the mixture is stirred at a speed of 300 r / min for 20 min, and then allowed to stand for 6 min. The mixture is then stirred at a speed of 700 r / min for 15 min, and then allowed to stand for 7 min. Finally, the mixture is stirred at a speed of 200 r / min for 10 min, and then allowed to stand for 20 min. The mixture is then moved to a wet mixer and kneaded at a speed of 200 r / min for 10 min. The mixture is sprayed with water at a speed of 12 L / min·m and kneaded and cleaned for 8 min. This is repeated 3 times to obtain a pretreated rubber raw material.

[0044] (2) The pretreated rubber raw material is creped in turn using a deep-grain crepe machine, a medium-grain crepe machine, and a shallow-grain crepe machine, wherein the crepe thickness of the deep-grain crepe machine is 2 cm, and the crepe pressing is repeated 3 times; the crepe thickness of the medium-grain crepe machine is 1.5 cm, and the crepe pressing is repeated 2 times; the crepe thickness of the shallow-grain crepe machine is 0.6 cm, and the crepe pressing is repeated 4 times; and then the raw material is stacked and aged at 40°C for 2 days to obtain an aged rubber raw material.

[0045] Comparative Example 3:

[0046] The difference between this comparative example and Example 3 is that the deep-line creping process is missing during the creping process. The specific steps are as follows:

[0047] (1) The collected cup rubber is sorted and crushed, and an oxalic acid solution with a concentration of 1.5wt% of the mass of the cup rubber is added, and the mixture is stirred at a speed of 300 r / min for 20 min, and then stirred at a speed of 700 r / min for 15 min, and then stirred at a speed of 700 r / min for 7 min, and finally stirred at a speed of 200 r / min for 10 min, and then stirred at a speed of 200 r / min for 20 min, and then moved to a wet mixer for kneading at a speed of 500 r / min for 6 min, and then the spray water is turned on to knead and clean for 12 min at 7 L / min·m, and the mixture is repeated 3 times, and then an oxalic acid solution with a concentration of 7% of the mass of the cup rubber is added at a speed of 800 r / min, and the mixture is kneaded for 5 min, and then the spray water is turned on to knead and clean for 10 min at 4 L / min·m, and the mixture is repeated 2 times to obtain a pretreated rubber raw material;

[0048] (2) The pretreated rubber raw material is creped using a medium-grain crepe machine and a light-grain crepe machine in turn, wherein the crepe thickness of the medium-grain crepe machine is 1.5 cm, and the crepe pressing is repeated twice; the crepe thickness of the light-grain crepe machine is 0.6 cm, and the crepe pressing is repeated four times; and then the raw material is piled up and aged at 40°C for 2 days to obtain an aged rubber raw material.

[0049] Comparative Example 4:

[0050] The difference between this comparative example and Example 3 is that the middle grain crepe treatment is lacking during the crepe treatment process. The specific steps are as follows:

[0051] (1) The collected cup rubber is sorted and crushed, and an oxalic acid solution with a concentration of 1.5wt% of the mass of the cup rubber is added, and the mixture is stirred at a speed of 300 r / min for 20 min, and then stirred at a speed of 700 r / min for 15 min, and then stirred at a speed of 700 r / min for 7 min, and finally stirred at a speed of 200 r / min for 10 min, and then stirred at a speed of 200 r / min for 20 min, and then moved to a wet mixer for kneading at a speed of 500 r / min for 6 min, and then the spray water is turned on to knead and clean for 12 min at 7 L / min·m, and the mixture is repeated 3 times, and then an oxalic acid solution with a concentration of 7% of the mass of the cup rubber is added at a speed of 800 r / min, and the mixture is kneaded for 5 min, and then the spray water is turned on to knead and clean for 10 min at 4 L / min·m, and the mixture is repeated 2 times to obtain a pretreated rubber raw material;

[0052] (2) The pretreated rubber raw material is creped using a deep-grain crepe machine and a shallow-grain crepe machine in turn, wherein the creping thickness of the deep-grain crepe machine is 2 cm, and the creping is repeated 3 times; the creping thickness of the shallow-grain crepe machine is 0.6 cm, and the creping is repeated 4 times; and then the raw material is piled up and aged at 40°C for 2 days to obtain an aged rubber raw material.

[0053] Comparative Example 5:

[0054] The difference between this comparative example and Example 3 is that the shallow grain creping process is lacking during the creping process. The specific steps are as follows:

[0055] (1) The collected cup rubber is sorted and crushed, and an oxalic acid solution with a concentration of 1.5wt% of the mass of the cup rubber is added, and the mixture is stirred at a speed of 300 r / min for 20 min, and then stirred at a speed of 700 r / min for 15 min, and then stirred at a speed of 700 r / min for 7 min, and finally stirred at a speed of 200 r / min for 10 min, and then stirred at a speed of 200 r / min for 20 min, and then moved to a wet mixer for kneading at a speed of 500 r / min for 6 min, and then the spray water is turned on to knead and clean for 12 min at 7 L / min·m, and the mixture is repeated 3 times, and then an oxalic acid solution with a concentration of 7% of the mass of the cup rubber is added at a speed of 800 r / min, and the mixture is kneaded for 5 min, and then the spray water is turned on to knead and clean for 10 min at 4 L / min·m, and the mixture is repeated 2 times to obtain a pretreated rubber raw material;

[0056] (2) The pretreated rubber raw material is creped using a deep-grain crepe machine and a medium-grain crepe machine in turn, wherein the creping thickness of the deep-grain crepe machine is 2 cm, and the creping is repeated 3 times; the creping thickness of the medium-grain crepe machine is 1.5 cm, and the creping is repeated 2 times; and then the raw material is piled up and aged at 40°C for 2 days to obtain an aged rubber raw material.

[0057] The performance of the aged rubber raw materials prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 4 was tested, wherein the initial value of plasticity (P0) was measured according to GB / T3510-2006; the plasticity retention rate (PRI) was measured according to GB / T3517-2022; and the Mooney viscosity (ML) was measured according to GB / T 1232.1-2016. The test results are shown in Table 1 below.

[0058] Table 1 Performance test results of matured rubber raw materials

[0059]

[0060] The above results show that the initial plasticity value (P0) of the matured rubber raw materials of Examples 1 to 3 prepared by the method of the present invention is 37.24 to 39.07, the plasticity retention rate (PRI) is 52.61 to 54.32, and the Mooney viscosity (ML) is 67.35 to 70.01, while in the preparation process of Comparative Examples 1 to 5, no oxalic acid solution is added for stirring and kneading, or the processing methods are different and the multi-stage creping treatment is not adopted, so that the performance of the matured rubber raw materials is reduced. The prepared matured rubber raw materials have an initial plasticity value (P0) of 32.03 to 35.41, a plasticity retention rate (PRI) of 21.53 to 26.24, and a Mooney viscosity (ML) of 56.53 to 59.04. The present invention adds oxalic acid solution to the cup rubber for stirring and kneading and performs multi-stage creping combined treatment, so that the rubber raw materials can be fully impurity-free, the rubber raw materials can be mixed more evenly, and a uniform degree of maturation can be maintained, all the rubber raw materials are in the same physical property state, thereby improving the quality of the rubber raw materials.

[0061] 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 principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A natural rubber raw material aging process, characterized in that: The following steps are involved: (1) sorting and crushing the collected cup rubber, adding 10-12% oxalic acid solution of the mass of the cup rubber, stirring, moving to a wet mixer for primary kneading, and then adding 5-8% oxalic acid solution of the mass of the cup rubber for secondary kneading to obtain a pretreated rubber raw material; (2) The pretreated rubber raw material is subjected to multi-stage creping in sequence using a deep-grain crepe machine, a medium-grain crepe machine, and a shallow-grain crepe machine, and then subjected to a stacking and aging treatment to obtain an aged rubber raw material.

2. The natural rubber raw material aging process according to claim 1, characterized in that: The concentration of the oxalic acid solution is 0.5-2.0 wt %.

3. The natural rubber raw material ripening process according to any one of claims 1 or 2, characterized in that: In step (1), the stirring process is: first stirring at a speed of 200-500 r / min for 15-30 min, standing for 6-8 min, then stirring at a speed of 600-800 r / min for 12-16 min, standing for 6-8 min, and finally stirring at a speed of 200-300 r / min for 10-12 min, standing for 20-30 min.

4. The natural rubber raw material ripening process according to any one of claims 1 or 2, characterized in that: In step (1), the kneading process is as follows: kneading for 4 to 8 minutes at a wet mixer speed of 300 to 600 r / min, spraying water at 6 to 10 L / min·m for kneading and cleaning for 10 to 15 minutes, and repeating 2 to 3 times.

5. The natural rubber raw material ripening process according to any one of claims 1 or 2, characterized in that: In step (1), the secondary kneading process is: kneading for 3 to 6 minutes at a wet mixer speed of 600 to 800 r / min, then turning on the spray water at 3 to 5 L / min·m to knead and clean for 8 to 12 minutes, and repeating 2 to 3 times.

6. The natural rubber raw material ripening process according to claim 1, characterized in that: In step (2), the creping thickness of the deep-grain crepe machine is 2 to 3 cm, and the creping is repeated 2 to 3 times; the creping thickness of the medium-grain crepe machine is 1.2 to 1.8 cm, and the creping is repeated 2 to 3 times; the creping thickness of the shallow-grain crepe machine is 0.5 to 0.8 cm, and the creping is repeated 3 to 4 times.

7. The natural rubber raw material ripening process according to claim 1, characterized in that: The stacking and aging process is as follows: the rubber raw materials after creping are stacked and aged at 40-50° C. for 1-3 days.

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