Method capable of controlling protein content of microbial coagulation natural latex and mixed coagulation aid

Abstract

The invention relates to the technical field of primary processing of natural rubber, in particular to a method capable of controlling the protein content of microbial coagulation natural latex and a mixed coagulation aid. Sulfonic acid has the characteristics of an anionic surfactant, can play a role in permeation and assistance, and can inactivate enzymes generated by microorganisms; sodium hypochlorite is decomposed under an acidic condition to release chlorine, so that microorganisms in latex can be killed; sodium chlorite is similar to sodium hypochlorite and also has the effect of killing microorganisms in latex; the trichloroacetic acid can enter an enzyme protein structure under the auxiliary action of the sulfonic acid, so that the conformation of the enzyme is changed, and the enzyme is inactivated. The mixed solidification auxiliary agent provided by the invention can regulate and control the content of protein in natural rubber, the content of the protein is fixed in a target range, and a natural rubber product with high performance and stable batch is produced.

Description

Technical Field

[0001] The present invention relates to the technical field of primary processing of natural rubber, and particularly relates to a method for controlling the protein content of natural rubber latex coagulated by microorganisms and a coagulation aid mixture. Background Art

[0002] Natural rubber is prepared by processing fresh latex collected from rubber trees through processes such as coagulation, creping, and drying. Fresh latex contains about 30% rubber hydrocarbon, about 60% water, and about 6% non-rubber components. Among the non-rubber components, protein accounts for about 1-2% of the total weight of the latex. Due to the influence of factors such as geographical environment, soil quality, rubber tree variety, tapping system, and production season, there are significant differences in different batches of fresh latex.

[0003] During the production process, there are many methods for coagulating natural fresh latex, including chemical coagulation, biological coagulation, physical coagulation, etc. The natural rubber obtained by the traditional acid coagulation process has a relatively high protein content, and the internal temperature will rise during dynamic use, resulting in a decrease in the service life of rubber products. Currently, in the industry, the content of free protein in natural rubber is mainly reduced by biological coagulation methods such as microorganisms or protease digestion to reduce the dynamic heat generation of natural rubber. However, the protein in natural rubber also contains substances that prevent aging and promote cross-linking of natural rubber, and its content is not the lower the better. For example, when the protein decreases, the anti-aging ability of natural rubber decreases, and the vulcanization time of the mixed rubber is prolonged; the lower the protein content, the longer the vulcanization time, which will affect the productivity, and the physical and mechanical properties of natural rubber also decrease. Therefore, the protein content in natural rubber is preferably controlled within a suitable range according to requirements.

[0004] In addition to being affected by factors such as fresh latex raw materials, temperature, and ammonia content, the action time of microorganisms is also an important influencing factor in microbial coagulation. The action of microorganisms on rubber starts from adding microorganisms to the latex, but it is not limited to the front end of the production process. Microorganisms still play a role in the mixing, latex coagulation, and subsequent creping and curing processes. Due to the uncertainty of the action time of microorganisms, it is difficult to control the degree of protein decomposition in rubber, and it is difficult to control indicators such as the softness and hardness of rubber, that is, the initial plasticity (P 0 ) and Mooney viscosity of rubber. The performance differences of natural rubber products in different batches are too large, which will seriously affect the use of downstream rubber product enterprises. Therefore, controlling the protein content in natural rubber is the key to preparing high-performance rubber and stable production. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a method for controlling the protein content of natural rubber latex by microbial coagulation and a mixed coagulation aid. By using the mixed coagulation aid provided by the present invention, the protein content in natural rubber can be regulated and fixed within the target range, and high-performance and batch-stable natural rubber products can be produced.

[0006] In order to achieve the above object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a mixed coagulation aid, which comprises 1-3% of sulfonic acid, 0.1-0.3% of sodium hypochlorite or sodium chlorite, 1-3% of trichloroacetic acid and the balance of water by mass percentage.

[0008] Preferably, the sulfonic acid comprises at least one of benzenesulfonic acid, linear alkylsulfonic acid and linear alkenylsulfonic acid.

[0009] Preferably, the linear alkylsulfonic acid comprises one or more of dodecylsulfonic acid, hexadecylsulfonic acid and octadecylsulfonic acid; the linear alkenylsulfonic acid comprises α-alkenylsulfonic acid and / or dodecenylsulfonic acid.

[0010] The present invention provides a method for controlling the protein content of natural rubber latex by microbial coagulation, which comprises the following steps: adding an acid solution to natural rubber latex to reduce the ammonia content in the latex to a content suitable for the action of a microbial preparation or a protease preparation, thereby obtaining low-ammonia latex;

[0011] adding a microbial preparation or a protease preparation to the low-ammonia latex to decompose the protein, and after the nitrogen content in the latex is reduced to a predetermined value, mixing the obtained low-protein latex with the mixed coagulation aid for coagulation.

[0012] Preferably, determining the dosage of the mixed coagulation aid comprises the following steps: calculating the dosage of the mixed coagulation aid according to the amount of acid used to neutralize the ammonia content in the low-ammonia latex and the amount of acid used for coagulation.

[0013] Preferably, the acid solution comprises at least one of sulfuric acid solution, phosphoric acid solution, citric acid solution, formic acid solution and acetic acid solution.

[0014] Preferably, the mass content of ammonia in the low-ammonia latex is 0.05-0.07%.

[0015] Preferably, before adding the acid solution to the natural rubber latex, the natural rubber latex is heated to a temperature suitable for the growth of microorganisms or the active temperature range of the protease preparation.

[0016] Preferably, the mixing of the low-protein latex and the mixed coagulation aid is co-current mixing.

[0017] Preferably, the low-protein latex has a nitrogen mass content of 0.15 to 0.25%.

[0018] The present invention provides a mixed coagulation aid, which, by mass percentage, includes 1 to 3% of sulfonic acid, 0.1 to 0.3% of sodium hypochlorite or sodium chlorite, 1 to 3% of trichloroacetic acid, and the balance of water. In the mixed coagulation aid, the sulfonic acid has the characteristics of an anionic surfactant, can play a role in penetration and assistance, and can inactivate the enzymes produced by microorganisms; sodium hypochlorite decomposes to release chlorine gas under acidic conditions, can kill the microorganisms in the latex, and has a bleaching effect on the rubber blocks. Since the usage amount in the mixed coagulation aid is relatively low, it is washed clean by water during the subsequent processing, and has no impact on the rubber properties; sodium chlorite is similar to sodium hypochlorite and also has the effect of killing the microorganisms in the latex; trichloroacetic acid can enter the interior of the enzyme protein structure with the assistance of sulfonic acid, change the conformation of the enzyme, and thus inactivate the enzyme. Therefore, for the mixed coagulation aid provided by the present invention, each component cooperates with each other, and its characteristics can not only coagulate the latex but also inactivate the microorganisms and enzymes in the latex, preventing the microorganisms or enzymes from continuing to play a role in the subsequent production process and resulting in uncontrollable protein content.

[0019] The present invention provides a method for controlling the protein content of microbially coagulated natural latex, which has the following advantages: by controlling the protein content in the latex, the performance of the raw rubber products can be controlled; by controlling the protein content in the latex, the performance fluctuations between batches of the raw rubber products can be reduced, meeting the requirements of downstream users; the mixed coagulation aid used is washed clean by water during the production process and has no adverse impact on the rubber properties; the process is simple, does not change the original process equipment, is easy to operate, and realizes controllable and stable production; the coagulation wastewater does not produce odor and does not affect the production workshop and working environment. Specific Embodiments

[0020] The present invention provides a mixed coagulation aid, which, by mass percentage, includes 1 to 3% of sulfonic acid, 0.1 to 0.3% of sodium hypochlorite or sodium chlorite, 1 to 3% of trichloroacetic acid, and the balance of water.

[0021] By mass percentage, the mixed coagulation aid provided by the present invention includes 1 to 3% of sulfonic acid, which can be 1%, 1.5%, 2%, 2.5%, or 3% in specific embodiments. In the present invention, the sulfonic acid preferably includes at least one of benzenesulfonic acid, linear alkylsulfonic acid, and linear alkenylsulfonic acid, and more preferably benzenesulfonic acid. In the present invention, the linear alkylsulfonic acid preferably includes one or more of dodecylbenzenesulfonic acid, hexadecylbenzenesulfonic acid, and octadecylbenzenesulfonic acid; the linear alkenylsulfonic acid preferably includes α-olefinsulfonic acid and / or dodecene sulfonic acid. In the present invention, the sulfonic acid has the characteristics of an anionic surfactant, can play a role in penetration and assistance, and can inactivate the enzymes produced by microorganisms.

[0022] In terms of mass percentage, the mixed coagulation aid provided by the present invention includes 0.1-0.3% of sodium hypochlorite or sodium chlorite, which can be 0.1%, 0.15%, 0.2%, 0.25% or 0.3% in specific embodiments. In the present invention, the sodium hypochlorite decomposes to release chlorine gas under acidic conditions, which can kill microorganisms in the latex and has a bleaching effect on the rubber blocks. Since the usage amount in the mixed coagulation aid solution is relatively low, it is washed clean with water during the later processing and has no impact on the rubber properties. Sodium chlorite is similar to sodium hypochlorite and also has the effect of killing microorganisms in the latex.

[0023] In terms of mass percentage, the mixed coagulation aid provided by the present invention includes 1-3% of trichloroacetic acid, which can be 1%, 1.5%, 2%, 2.5% or 3% in specific embodiments. In the present invention, the trichloroacetic acid can enter the interior of the enzyme protein structure with the assistance of sulfonic acid, change the conformation of the enzyme, and thus inactivate the enzyme.

[0024] The mixed coagulation aid provided by the present invention includes the balance of water, and the water is preferably deionized water.

[0025] The present invention provides a method for controlling the protein content in natural latex during coagulation, which includes the following steps: adding an acid solution to the natural latex to reduce the ammonia content in the latex to a content suitable for the action of a microbial preparation or a protease preparation, obtaining a low-ammonia latex;

[0026] Adding a microbial preparation or a protease preparation to the low-ammonia latex to decompose the protein. After the nitrogen content in the latex is reduced to a predetermined value, mixing the obtained low-protein latex with the mixed coagulation aid for coagulation.

[0027] In the present invention, unless otherwise specified, the raw materials used are all commercially available products well-known in the art.

[0028] The present invention adds an acid solution to the natural latex to reduce the ammonia content in the latex to a content suitable for the action of a microbial preparation or a protease preparation, obtaining a low-ammonia latex.

[0029] In the present invention, the natural latex is preferably natural latex after being centrifugally sedimented to remove impurities. The present invention preferably takes fresh natural latex (ammonia water is added to the latex as a latex preservative), detects the dry content, ammonia (NH 3 ) content and nitrogen content. After centrifugally sedimenting to remove impurities in the latex, the required natural latex is obtained. The present invention has no special requirements for the detection methods of the dry content, ammonia content and nitrogen content, and the well-known detection methods in the art can be used.

[0030] Before adding the acid solution to the natural latex, the present invention preferably first heats the natural latex to a temperature suitable for the growth of microorganisms or the active temperature range of the protease preparation, which is 36-40°C in specific embodiments.

[0031] The present invention preferably heats under stirring conditions.

[0032] In the present invention, the acid solution preferably includes at least one of sulfuric acid solution, phosphoric acid solution, citric acid solution, formic acid solution, and acetic acid solution. The present invention has no special requirements for the concentration of the acid solution, and the well-known concentration in the art can be used. When the acid solution is formic acid solution or acetic acid solution, the mass fraction of the formic acid solution or acetic acid solution is preferably 1-5%.

[0033] The present invention does not make special limitations on the addition amount of the acid solution, as long as the ammonia content in the latex can be reduced to a content suitable for the action of the microbial preparation or protease preparation. The present invention neutralizes the ammonia in the natural latex by adding an acid solution. Since microorganisms or enzymes are inactive in a high-ammonia state, the present invention enables the biological preparation in the latex to play a role by reducing ammonia.

[0034] In the present invention, the mass content of ammonia in the low-ammonia latex is preferably 0.05-0.07%, and can be 0.05%, 0.06%, or 0.07% in specific embodiments. At this time, the low-ammonia latex is in a state where microorganisms can grow and the latex does not coagulate.

[0035] The present invention preferably adds the acid solution to the natural latex under stirring conditions in a mixing tank.

[0036] In the present invention, the pH value of the low-ammonia latex after adding the acid solution is preferably 7.5-8.5.

[0037] After obtaining the low-ammonia latex, the present invention adds a microbial preparation or protease preparation to the low-ammonia latex to decompose proteins, and after the nitrogen content in the latex is reduced to a predetermined value, a low-protein latex is obtained.

[0038] The present invention does not make special requirements for the specific types of the microbial preparation and protease preparation, and any microbial preparation and protease preparation well-known in the art that can be used to degrade proteins are acceptable. The present invention does not make special limitations on the addition amounts of the microbial preparation and protease preparation. Different microbial preparations and protease preparations have different appropriate addition amounts, and they can be added according to the conventional amounts. In the examples of the present invention, the specific microbial preparation used is the bacillus licheniformis product purchased from Yuyuan Biotechnology Co., Ltd., Jining, Shandong; the specific protease preparation is the alkaline protease product produced by Nanning Dongheng Huadao Biotechnology Co., Ltd. Among them, the effective viable bacteria count of the microbial inoculum is 10 billion / g, and the enzyme activity of the protease preparation is 200,000 u / g. According to 0.15% (mass fraction) of the dry rubber content, the microbial preparation or protease preparation is added after being prepared into a 5% biological preparation solution by adding water in a batching tank.

[0039] The present invention preferably adds the microbial preparation or protease preparation under the condition of continuous stirring.

[0040] In the present invention, after adding the microbial preparation or protease preparation, the proteins in the low-ammonia latex will be decomposed, thereby resulting in a decrease in the nitrogen content. In the present invention, the protein content in the rubber is calculated according to the detected nitrogen content by a formula. It can also be considered that a certain nitrogen content represents a certain amount of protein. The present invention does not make special limitations on this. In short, the purpose of detecting the protein content is achieved through the detection of the nitrogen content. The present invention preferably samples and detects once every 1 hour.

[0041] The present invention does not make special requirements for the mass content of nitrogen in the low-protein latex. Those skilled in the art can set a reasonable content range according to actual needs. In the present invention, the recommended content is 0.15 - 0.25%.

[0042] After obtaining the low-protein latex, the present invention mixes the obtained low-protein latex with a mixed coagulation aid for coagulation.

[0043] In the present invention, the mixing is preferably co-current mixing. The present invention preferably flows the low-protein latex and the mixed coagulation aid into the coagulation tank in a co-current manner. The present invention has no requirements for the flow rate, as long as they flow in simultaneously (the time taken to flow out is the same).

[0044] The present invention preferably calculates the dosage of the mixed coagulation aid according to the amount of acid used to neutralize the ammonia content in the low-ammonia latex and the amount of acid used for coagulation. Specifically, first, the total dosage of sulfonic acid and trichloroacetic acid required is determined according to the amount of acid used to neutralize the ammonia content in the low-ammonia latex and the amount of acid used for coagulation. Then, the respective dosages are determined according to the mass percentage content ratio of the two. Finally, the dosage of the mixed coagulation aid is determined according to the proportion of sulfonic acid or trichloroacetic acid in the mixed coagulation aid.

[0045] In the present invention, the calculation processes of the acid used to neutralize the ammonia content in the low-ammonia latex and the acid used for coagulation belong to methods well-known in the art.

[0046] In a specific embodiment of the present invention, the calculation method for the addition amount of the mixed coagulation aid is as follows:

[0047] The calculation of the amount of neutralizing acid is shown in Equation 1:

[0048] Z = [M × N × (B × 9.30 + S × 9.61) / (B + S)] ÷ H Equation 1;

[0049] The calculation of the amount of solidifying acid is shown in Equation 2:

[0050] G = (M × K × 0.4%) ÷ H Equation 2;

[0051] In Equation 1 and Equation 2, Z: the amount of neutralizing acid; M: the amount of latex; N: the ammonia content of the latex; B: the proportion of benzenesulfonic acid in the mixed coagulant; S: the proportion of trichloroacetic acid in the mixed coagulant; H: the percentage content of acid in the mixed coagulant; G: the amount of solidifying acid; K: the dry content of the latex.

[0052] After adding the mixed coagulation aid in the present invention, the sulfonic acid plays a role in penetration and assistance, and can inactivate the enzymes produced by microorganisms; sodium hypochlorite decomposes under acidic conditions to release chlorine gas (after adding the mixed coagulation aid, the latex is acidic), which can kill the microorganisms in the latex and has a bleaching effect on the rubber blocks. Due to the low usage amount, it is washed clean by water during the subsequent processing process and has no impact on the rubber properties; sodium chlorite is similar to sodium hypochlorite and also has the effect of killing the microorganisms in the latex; trichloroacetic acid can enter the interior of the enzyme protein structure under the assistance of the sulfonic acid, change the conformation of the enzyme, and thus inactivate the enzyme. The mixed coagulation aid can not only coagulate the latex but also inactivate the microorganisms and enzymes in the latex, preventing the microorganisms or enzymes from continuing to play a role in the subsequent production process and resulting in uncontrollable protein content, thereby ensuring the stability of products in different batches.

[0053] In the present invention, the coagulation time is preferably 8 - 24 h, and in specific embodiments, it can be 8 h, 12 h, 16 h, 20 h or 24 h.

[0054] After completing the coagulation, the present invention preferably rolls, crepes, tears and dries the obtained coagulated latex in a conventional manner to obtain the raw rubber product.

[0055] The following examples are used to illustrate in detail the method for controlling the protein content of natural latex by microbial coagulation and the mixed coagulation aid provided by the present invention, but they should not be construed as limiting the protection scope of the present invention.

[0056] Example 1

[0057] 2000 kg of fresh latex retrieved from the rubber plantation was tested with a dry content of 31.2%, ammonia content of 0.21%, and nitrogen content of 0.45%. After centrifugal sedimentation to remove impurities in the latex, the latex flowed into the mixing tank. Under stirring, 289 kg of formic acid solution with a mass fraction of 3% was slowly added to adjust the ammonia content of the latex to 0.05%. 0.936 kg of a microbial preparation with an effective viable count of 10 billion / g was taken and formulated into a 5% biological preparation solution of 18.72 kg with water in the dosing tank, and then evenly added to the latex. The mixing tank was kept under stirring, and samples were taken and tested every 1 h until the nitrogen content was between 0.15% and 0.25%. Stirring was stopped, and the amounts of acid for neutralization and coagulation were calculated. The coagulation acid was calculated based on 0.4% of the dry content of the latex, and the usage amount of the mixed coagulation aid was calculated to be 597.55 kg. A mixed coagulation aid of benzene sulfonic acid 1%, sodium hypochlorite 0.1%, trichloroacetic acid 1%, and deionized water 97.9% was prepared in advance. When the detected nitrogen content reached the predetermined value, the flow rate was adjusted to simultaneously and co-currently feed the latex and the mixed coagulation aid into the coagulation tank to ensure uniform mixing, and left to coagulate for 16 h. Subsequently, it was pressed thinly, creped, granulated, and dried according to the conventional method to obtain the raw rubber finished product Example Sample 1.

[0058] Example 2

[0059] 2000 kg of fresh latex from the same batch of rubber plantation as in Example 1 was taken, and the treatment method was the same as that in Example 1. The difference was that a mixed coagulation aid of benzene sulfonic acid 1%, sodium chlorite 0.1%, trichloroacetic acid 1%, and deionized water 97.9% was prepared, and the raw rubber finished product Example Sample 2 was obtained.

[0060] Example 3

[0061] 2000 kg of fresh latex from the same batch of rubber plantation as in Example 1 was taken, and the treatment method was the same as that in Example 1. The difference was that a mixed coagulation aid of benzene sulfonic acid 3%, sodium chlorite 0.3%, trichloroacetic acid 3%, and deionized water 93.7% was prepared. The usage amount of the mixed coagulation aid was calculated to be 199.43 kg. The flow rate was adjusted to simultaneously and co-currently feed the latex and the mixed coagulation aid into the coagulation tank, and other treatment methods were the same as those in Example 1, and the raw rubber finished product Example Sample 3 was obtained.

[0062] Example 4

[0063] Take 2000 kg of fresh latex from a batch different from that in Example 1. The dry content is detected to be 30.6%, the ammonia content is 0.22%, and the nitrogen content is 0.51%. The treatment method is the same as that in Example 1, and the ratio of the mixed coagulation aid is the same as that in Example 1. Adjust the ammonia content of the latex to 0.05%, and use 307.13 kg of formic acid solution with a mass concentration of 3%; use 0.918 kg of a microbial preparation with an effective viable count of 10 billion / g, and the amount of the 5% microbial preparation solution prepared is 18.36 kg; calculate the usage amount of the mixed coagulant to be 595.15 kg; adjust the flow rate and put the latex and the mixed coagulation aid into the coagulation tank in parallel flow at the same time. Other treatment methods are the same as those in Example 1 to obtain the raw rubber finished product, Example sample 4.

[0064] Example 5

[0065] Take 2000 kg of fresh latex from a batch different from that in Example 1. The dry content is detected to be 31.5%, the ammonia content is 0.20%, and the nitrogen content is 0.47%. The treatment method is the same as that in Example 1, and the ratio of the mixed coagulation aid is the same as that in Example 1. Adjust the ammonia content of the latex to 0.05%, and use 271 kg of formic acid solution with a mass concentration of 3%; use 0.945 kg of a microbial preparation with an effective viable count of 10 billion / g, and the amount of the 5% microbial preparation solution prepared is 18.9 kg; calculate the usage amount of the mixed coagulation aid to be 598.75 kg; adjust the flow rate and put the latex and the mixed coagulation aid into the coagulation tank in parallel flow at the same time. Other treatment methods are the same as those in Example 1 to obtain the raw rubber finished product, Example sample 5.

[0066] Example 6

[0067] Take 2000 kg of fresh latex from the same rubber plantation batch as in Example 1. The treatment method is the same as that in Example 1. The difference is to prepare a mixed coagulation aid of 2% benzenesulfonic acid, 0.3% sodium chlorite, 2% trichloroacetic acid, and 95.7% deionized water. Calculate the usage amount of the mixed coagulation aid to be 298.78 kg. Adjust the flow rate and put the latex and the mixed coagulation aid into the coagulation tank in parallel flow at the same time. Other treatment methods are the same as those in Example 1 to obtain the raw rubber finished product, Example sample 6.

[0068] Example 7

[0069] Take 2000 kg of fresh latex from the same rubber plantation batch as in Example 1. The treatment method is the same as that in Example 1. The difference is to prepare a mixed coagulation aid of 2.5% benzenesulfonic acid, 0.3% sodium chlorite, 1.5% trichloroacetic acid, and 95.7% deionized water. Calculate the usage amount of the mixed coagulation aid to be 297.81 kg. Adjust the flow rate and put the latex and the mixed coagulation aid into the coagulation tank in parallel flow at the same time. Other treatment methods are the same as those in Example 1 to obtain the raw rubber finished product, Example sample 7.

[0070] Comparative Example 1

[0071] Comparative Example 1 adopted the traditional WF glue preparation process. Fresh latex from the same batch of rubber plantations as in Example 1 was taken, with a dry content of 31.2%, an ammonia content of 0.21%, and a nitrogen content of 0.45%. The impurities in the latex were removed by centrifugal sedimentation. 10 kg of the impurity-removed latex was taken and placed in a tray for sample preparation. 5.6 kg of water was added to dilute the latex to a dry content of 20%. After stirring evenly, the amounts of acid for neutralization and coagulation were calculated. The coagulation acid was calculated at 0.4% of the dry content of the latex. It was calculated that the amount of formic acid solution with a mass concentration of 3% to be used was 2.313 kg. The latex and the 3% formic acid solution were slowly added to the latex tray while stirring to ensure uniform mixing. It was left to coagulate for 16 h, and then it was conventionally pressed thinly, creped, granulated, and dried to obtain the raw rubber finished product Comparative Sample 1.

[0072] Comparative Example 2

[0073] 2000 kg of fresh latex from the same batch of rubber plantations as in Example 1 was taken, and the treatment method was the same as that in Example 1. The difference was that a mixed coagulation aid of 3% benzenesulfonic acid, 0.3% sodium chlorite, and 96.7% deionized water was prepared. The usage amount of the mixed coagulation aid was calculated to be 393.2 kg. The flow rate was adjusted to simultaneously and co-currently feed the latex and the mixed coagulation aid into the coagulation tank. Other treatment methods were the same as those in Example 1 to obtain the raw rubber finished product Comparative Sample 2.

[0074] Comparison of the properties of the samples in the examples and comparative examples

[0075] Using conventional methods, the physical and chemical properties and vulcanization properties of Examples 1 - 6 and Comparative Sample 1 were tested. The determination test of the rubber vulcanization properties was carried out according to the ACS I pure rubber formula (100.00 parts of natural rubber, 6.00 parts of zinc oxide, 3.50 parts of sulfur, 0.50 parts of stearic acid, 0.50 parts of MBT) specified in NY / T 1403 - 2007. The test results of the physical and chemical properties are shown in Table 1, and the test results of the vulcanized rubber properties are shown in Table 2. Key indicators (Mooney viscosity, tensile strength) were selected for comparison between product batches. When the coefficient of variation of the key indicators was less than 5%, the batch was considered stable.

[0076] The formula for the coefficient of variation is: C u = δ / μ; where C u : coefficient of variation; δ: standard deviation; μ: mean.

[0077] Table 1 Physical and chemical properties of the samples in the examples and comparative examples

[0078]

[0079] Table 2 Mechanical properties of the vulcanized rubber of the samples in the examples and comparative examples

[0080]

[0081] Note: The Mooney viscosity 1+4 in Table 1 refers to the test result after preheating for 1 minute and rotor rotation for 4 minutes, which belongs to a commonly used test method for Mooney viscosity.

[0082] According to the nitrogen content data in Table 1, it can be seen that the samples of the examples can all be effectively controlled. With the relative reduction of protein in natural rubber, the PRI value (plastic retention index) basically does not change significantly, indicating that controlling the protein content within the set range does not cause a decline in the anti-aging performance of the rubber.

[0083] It can be seen from Table 2 that the tensile strength and tear strength of the vulcanizates of the samples of the examples still maintain the advantages of the microbio-coagulation process. The comparison between batches is as follows:

[0084] By comparing Example Sample 1 and Example Sample 2, it can be known that the coefficient of variation of Mooney viscosity is 4.33%, and the coefficient of variation of tensile strength is 2.76%. The coefficient of variation of the indexes is less than 5%, indicating that the replacement of sodium hypochlorite with sodium chlorite in the mixed coagulation aid formulation has little impact on the product.

[0085] By comparing Example Samples 2, 3, 6, and 7, it can be known that as the acid content in the mixed coagulation aid increases, the mechanical properties of the samples decline, indicating that the change in the acid content in the mixed coagulation aid will affect the performance of the rubber product, and a lower acid content is beneficial to maintaining the performance of the rubber.

[0086] By comparing Example Sample 3 and Comparative Sample 2, the coefficient of variation of Mooney viscosity is 5.75%, and the coefficient of variation of the index is greater than 5%. The Mooney viscosity of Comparative Sample 2 is on the high side because the mixed coagulation aid in this example lacks trichloroacetic acid, indicating that the composition in the mixed coagulation aid has a cooperative effect, and the lack of one of its components will affect the performance of the experimental samples.

[0087] By comparing Example Samples 1, 4, and 5, the coefficient of variation of Mooney viscosity is 1.68%, and the coefficient of variation of tensile strength is 2.84%. The coefficient of variation of the indexes is less than 5%, indicating that when the process remains the same, by controlling the protein content in natural rubber, high-performance natural rubber can be stably prepared.

[0088] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A mixed coagulation aid, characterized in that: Calculated by mass percentage, it includes 1-3% sulfonic acid, 0.1-0.3% sodium hypochlorite or sodium chlorite, 1-3% trichloroacetic acid and the balance water.

2. The mixed coagulation aid according to claim 1, characterized in that: The sulfonic acid includes at least one of benzenesulfonic acid, a linear alkylsulfonic acid, and a linear olefinsulfonic acid.

3. The mixed coagulation aid according to claim 2, characterized in that: The linear alkyl sulfonic acid includes one or more of dodecyl sulfonic acid, hexadecyl sulfonic acid and octadecyl sulfonic acid; the linear olefin sulfonic acid includes α-olefin sulfonic acid and / or dodecenyl sulfonic acid.

4. A method for controlling the protein content of natural rubber latex coagulated by microorganisms, characterized in that: The following steps are involved: Adding an acid solution to natural rubber latex to reduce the ammonia content in the latex to a content suitable for the microbial preparation or the protease preparation to function, thereby obtaining a low-ammonia latex; A microbial preparation or a protease preparation is added to the low-ammonia latex to decompose the protein. After the nitrogen content in the latex is reduced to a predetermined value, the obtained low-protein latex is mixed with a mixed coagulation aid for coagulation.

5. The method according to claim 4, characterized in that Determining the amount of the mixed coagulation aid includes the following steps: calculating the amount of the mixed coagulation aid according to the amount of the acid used to neutralize the ammonia content in the low-ammonia latex and the amount of the coagulation acid.

6. The method according to claim 4, characterized in that The acid solution includes at least one of a sulfuric acid solution, a phosphoric acid solution, a citric acid solution, a formic acid solution and an acetic acid solution.

7. The method according to claim 4 or 5, characterized in that: The mass content of ammonia in the low-ammonia latex is 0.05-0.07%.

8. The method according to claim 4 or 6, characterized in that: Before adding the acid solution to the natural latex, the method further comprises heating the natural latex to a temperature suitable for the growth of microorganisms or to an active temperature range of the protease preparation.

9. The method according to claim 4, characterized in that The low-protein latex and the mixed coagulation aid are mixed in parallel flow.

10. The method according to claim 4 or 9, characterized in that: The mass content of nitrogen in the low-protein latex is 0.15-0.25%.

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