Storage method and application of miscellaneous gum

Abstract

The invention provides a storage method and application of miscellaneous rubber, and belongs to the technical field of pretreatment of natural rubber. The storage method comprises the following steps: (1) carrying out crepe treatment on scrap glue to obtain crepes; and (2) storing the crepe for 2-3 days in a hanging manner. According to the method, different influence factors and conditions of the miscellaneous rubber crepe are analyzed, and the plasticity retention rate is taken as an index, so that the optimal crepe storage process is as follows: the thickness of the crepe is 7mm, the crepe number is 7, the crepe is washed with a small amount of water, and the crepe is stored for 2 days in a hanging form. Under the optimal process condition, the PRI value of the miscellaneous glue is optimized, the glue preparation standard of the No.10 glue is met, compared with the raw materials, the physicochemical indexes of the obtained miscellaneous standard glue are comprehensively improved, the thermal stability is better, the decomposition process of the glue material is similar, and a theoretical data basis can be provided for subsequent large-scale high-quality production of the miscellaneous standard glue.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pretreatment of natural rubber, and particularly relates to a storage method of miscellaneous rubber and application. BACKGROUND

[0002] At present, more than 2000 kinds of plants containing natural rubber are found, but only Hevea brasiliensis is a tree species with commercial value. Natural rubber not only has good insulation, wear resistance and air tightness, but also has high plasticity, elasticity and tensile resistance. These excellent properties are unmatched by synthetic rubber, and it is listed together with steel, coal and oil as the raw materials of the four major commodity industrial production. Due to its excellent performance, it is widely used in various fields such as industry, national defense, transportation, medical and health care, heavy automobile manufacturing and the like. Natural rubber raw materials are divided into fresh latex and miscellaneous rubber due to the difference in quality and collection method, and the miscellaneous rubber accounts for a certain proportion. Due to the large demand for natural rubber, improving the utilization rate and service life of miscellaneous rubber is of great significance to promote the development of rubber industry and alleviate the pressure of market demand for rubber.

[0003] Artificial tapping is the main way to collect natural rubber, and the working efficiency of this method is not high. In the process of collecting natural rubber, a large amount of miscellaneous rubber such as rubber mass, rubber thread and mud rubber is produced, which accounts for about 10% of the total output of natural rubber. Due to the limitation of the environment and geographical location of planting natural rubber, these miscellaneous rubber raw materials are often processed a long time after the collection of natural rubber, which causes the phenomenon that the collection of miscellaneous rubber raw materials is not timely. And after collection, it is generally stored for a long time before being processed uniformly, which makes the raw materials further oxidized and contaminated to a certain extent, and finally leads to the difficulty in improving the quality of natural rubber in the processing process.

[0004] At present, the methods for storing miscellaneous rubber include storing in a ventilated and humid environment, natural storage, storage in water and storage after drying, etc. The method of storing in a ventilated and humid environment is mostly used in industrial production, which is also the best storage method. However, some rubber farmers will keep the rubber for more than half a year before selling, which leads to large differences in the quality of miscellaneous rubber, poor quality stability of miscellaneous rubber, and further affects the factory's income.

[0005] Since there is no clear data to prove the crepe storage process of natural rubber so far, it is very important to provide a method for effectively processing and storing miscellaneous rubber, and further improving the thermal stability of natural rubber products for the wide application of miscellaneous rubber. SUMMARY

[0006] The present application aims to provide a storage method of miscellaneous rubber and application, which can improve the product quality of miscellaneous rubber and improve the quality stability of miscellaneous rubber.

[0007] In order to achieve the above-mentioned object of the application, the application provides the following technical solutions. The application provides a storage method of miscellaneous rubber, comprising the following steps: (1) crepe processing is performed on the miscellaneous rubber to obtain a crepe; (2) the crepe is stored in the form of hanging for 2-3 days.

[0008] Preferably, in step (1), the miscellaneous rubber is miscellaneous rubber stored for more than one week.

[0009] Preferably, in step (1), the number of times of crepe processing is 5-11 times.

[0010] Preferably, in step (1), the water flushing rate of crepe processing is 5-7 L / h.

[0011] Preferably, in step (1), the thickness of the crepe is 7-8 mm.

[0012] Preferably, in step (2), the method of hanging is that the crepe processed miscellaneous rubber is hung on a bamboo pole.

[0013] Preferably, in step (2), the storage temperature is 28-35 DEG C.

[0014] The application further provides application of the storage method in improving the thermal stability of miscellaneous rubber.

[0015] The application further provides application of the storage method in improving the physicochemical properties of miscellaneous rubber.

[0016] Compared with the prior art, the application has the following beneficial effects: The application analyzes different influencing factors and conditions of the crepe of miscellaneous rubber, takes the plastic retention rate as an index, and obtains the optimal process of crepe storage: the thickness of the crepe is 7 mm, the number of times of crepe processing is 7, a small amount of water is used for flushing, and the crepe is stored in the form of hanging for 2 days. Under the optimal process condition, the PRI value of the miscellaneous rubber is optimized to reach the rubber production standard of No. 10 rubber, the obtained miscellaneous rubber is compared with the raw material, the physicochemical indexes are comprehensively improved, the thermal stability performance is better, the decomposition process of the rubber is similar, and the theoretical data basis can be provided for subsequent large-scale high-quality production of miscellaneous rubber standard rubber.

[0017] In order to determine the influence of the best process on the heat stability of natural rubber, the application compares and analyzes the TG curves of two samples of natural rubber, and the analysis result shows that the storage of the best process has a certain influence on the TG curve of the rubber, the weight loss rate of the No. 13 sample is lower than that of the raw material sample rubber, the reaction temperature is higher, and the heat resistance of the No. 13 sample is better. By comparing and analyzing the DSC curves of the two samples of natural rubber, it is concluded that the exothermic reaction curve of the No. 13 sample is more gentle, and the aging resistance of the No. 13 sample is stronger than that of the raw material sample rubber, and the stability is better, and the service life is longer after being made into rubber products.

[0018] After comparing and analyzing the physical and chemical indexes of the raw material sample rubber and the No. 13 sample, it is concluded that the ash content, impurity content and volatile content of the No. 13 sample are lower than those of the raw material sample rubber, the plasticity initial value (P0) is increased by 23.1 percentage points, the plasticity retention rate (PRI) is increased by 128.8 percentage points, the Mooney viscosity and nitrogen content are slightly lower, which proves that the best process condition is of great significance to improve the physical and chemical indexes of natural rubber. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained according to these drawings without creative labor for those skilled in the art.

[0020] Figure 1 The experimental technical roadmap of the present application, wherein the water flushing amount refers to the water flushing rate; Figure 2 The TG curve comparison diagram of the No. 13 sample and the raw material sample, Figure 2 In the figure, A represents the No. 13 sample prepared in example 1, and B represents the rubber stored for one week after example 1; Figure 3 The DSC curve of sample A (No. 13 sample prepared in example 1) and sample B (rubber stored for one week after example 1). DETAILED DESCRIPTION

[0021] Now, various exemplary embodiments of the present application will be described in detail, which should not be considered as limiting the present application, but should be understood as a more detailed description of some aspects, characteristics and embodiments of the present application.

[0022] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Additionally, for a range of values, the use of upper limit and lower limit, unless specifically stated otherwise, is understood to include each intervening value and each subrange between any stated value or intervening value within the stated range. Each smaller range between any stated value or intervening value within the range and any other stated value or intervening value within the stated range is also included within the present application. The upper and lower limits of these smaller ranges can independently be included or excluded from the range.

[0023] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are cited. In case of conflict between the content of the specification and that of any document incorporated herein by reference, the content of the specification prevails.

[0024] Many modifications and variations of the present application described in the specification are possible without departing from the scope or spirit of the present application. Other implementations of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples are illustrative only.

[0025] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", "contains", "containing", or variations thereof, are intended to be open-ended terms that mean including, but not limited to.

[0026] The present application provides a storage method of miscellaneous glue, comprising the following steps: (1) crepe processing of miscellaneous glue, to obtain crepe; (2) the crepe is stored in the form of hanging piece for 2-3 days.

[0027] In the present application, the miscellaneous glue is preferably stored for one week or more; the number of times of crepe processing is preferably 5-11 times, further preferably 6-10 times, more preferably 7-9 times, and still more preferably 8 times; the water flushing rate of crepe processing is preferably 5-7 L / h, further preferably 5.5-6.5 L / h, and more preferably 6 L / h; the thickness after crepe processing is preferably 7-8 mm, further preferably 7.4-7.8 mm, and more preferably 7.5 mm; the method of hanging piece is preferably hanging the crepe-processed miscellaneous glue on a bamboo pole, and the hanging piece is performed in a shaded condition; the storage temperature is preferably 28-35℃, further preferably 30-34℃, and more preferably 32℃; and the storage time is preferably 2.5 days.

[0028] The application also provides application of the storage method in improving the thermal stability of the rubber.

[0029] The application also provides application of the storage method in improving the physical and chemical properties of the rubber.

[0030] Exploration of rubber storage process Rubber from Mengla County was used as natural rubber raw material (provided by Xishuangbanna Field Rubber Group Co., Ltd.) and stored in the open air with film cloth covering for one week. The rubber stored for one week (raw material sample) was prepared into crimped sheets of different thicknesses using a natural rubber primary processing machine crimping machine (NY / T262-2018, purchased from Zhanjiang Weida Machinery Industry Co., Ltd.). The effects of crimped sheet thickness, crimped sheet number, water amount, stacking method and stacking time on the storage effect of the rubber were explored using orthogonal tests, wherein the orthogonal test design table is shown in Table 1.

[0031] Table 1. Orthogonal test design table

[0032] Among them, the large water flushing rate is 15 L / h, and the small water flushing rate is 6 L / h; the plastic retention index (PRI) of the crimped sheet is determined according to the method recorded in “GB / T 3517-2014 Determination of plastic retention index (PRI) of natural rubber”, and the results are shown in Table 2.

[0033] Table 2. Effect of different crimping processes on PRI

[0034] The results show that the initial plastic retention index value of the raw material sample is 29.69, which does not reach the qualified line of No. 20 rubber in “GB / T 8081-2018 Natural rubber Technical classification of rubber (TSR) specification guide”, and belongs to unqualified rubber, but after the design and optimization of the crimping process, the plastic retention index value PRI of No. 13 sample reaches 67.93, which exceeds 60, reaches the qualified line of No. 10 rubber of the national standard, and the plastic initial value P0 is 52.70, which also meets the national standard. This shows that after crimping, the storage time, storage method, crimping number, crimping thickness and water amount in the processing process will affect the plastic retention index (PRI) of the rubber.

[0035] The number of crimping times relates to the impurity content and plastic retention index (PRI) of the raw material, and the crimping thickness affects the impurity content of the raw material, the uniformity of the raw material, the aging time, and then affects the plastic retention index (PRI) of the product. According to the above experimental results, crimping 7 times and crimping thickness of 7 mm have the smallest effect on the plastic retention index of the rubber, and can reduce the impurity content of the raw material.

[0036] At the same time, the size of the washing water in the crepe process will affect the impurity content of the dry glue, and the storage method of the crepe can ensure the ventilation effect of the sample and reduce the possibility of variation of the glue during storage. Because the raw material of the glue has been stored for a long time before processing, if it is stored for a long time during processing, the performance of the product will decrease and the physical and chemical properties will deteriorate. According to the above results, it can be known that the storage of 2d can reduce the probability of the glue being affected by adverse factors.

[0037] The plasticity initial value P0 of sample No. 17 is 50.60, and the plasticity retention rate PRI is 53.36, which is close to the value of sample No. 13 which is the best process sample, and the values of plasticity initial value P0 and plasticity retention rate PRI also meet the national standard No. 10 glue qualified line, reaching the standard of No. 10 glue. It shows that the crepe process of sample No. 17 is only second to sample No. 13, and the crepe process of sample No. 17 is that the crepe thickness is 7mm, the crepe times are 11 times, there is no water washing, and the storage form is rolling for 4d. That is, under the condition of 11 times of crepe and rolling storage for 4d, the plasticity retention rate (PRI) of the product can also be improved, but there is still a big gap compared with the crepe process of sample No. 13.

[0038] Example 2 Comparison of thermal properties of crepe storage glue and water washed glue 2.1 Thermogravimetric analysis, also known as thermal gravimetric analysis (TG), is a thermal analysis technique that measures the change of mass of a substance with temperature or time under program control. The TG curve can show the reaction stage of thermal oxidative degradation of the sample. The thermal gravimetric analysis (TG) of sample No. 13 crepe storage glue and raw material prepared in example 1 was carried out at a temperature range of 28℃-700℃ with a heating rate of 10℃ / min. The results are shown in Figure 2 and Table 3.

[0039] Table 3 Degradation characteristic temperature table of sample A and sample B

[0040] From Figure 2 It can be seen that the two samples have multiple turning points in the TG graph, indicating that sample No. 13 and the raw material sample show a multi-step thermal oxidative degradation reaction, rather than a one-step reaction. The weight loss process mainly occurs in the range of 340℃-440℃, and the weight loss rates of sample A and B in this range are 93% and 96% respectively. The peak value and specific temperature of the reaction of the two samples are also different. The reaction temperature of sample No. 13 is 386℃, and the reaction temperature of the raw material sample is 382℃.

[0041] Table 3 reflects the change of the characteristic temperature of the thermal oxidative degradation of the two samples during the degradation reaction. T0 represents the temperature at which the reaction starts to degrade, Tp T represents the temperature at which the reaction reaches its maximum degradation rate. f The values ​​indicate the temperatures at which the degradation reaction ends. Table 3 shows that sample 13 began to show significant degradation at 323℃, reached its maximum degradation rate at 386℃, and terminated degradation at 445℃. The raw material sample began to degrade at 280℃, reached its maximum degradation rate at 382℃, and terminated degradation at 464℃. The T0 and T2 values ​​for sample 13 are also shown. P The temperatures were all higher than those of the raw material sample, indicating that its thermal stability was better than that of the raw material sample.

[0042] 2.2 Differential Scanning Calorimetry (DSC) Differential scanning calorimetry (DSC) is a method of measuring the power difference between a sample and a reference material as a function of temperature under programmed temperature control. DSC can detect the exothermic degradation of natural rubber during aging and can be used to evaluate its aging resistance. Therefore, DSC was performed on the No. 13 crepe storage rubber and raw material samples prepared in Example 1 at a heating rate of 10℃ / min within a temperature range of 28℃-700℃. The results are as follows... Figure 3 As shown.

[0043] Depend on Figure 3 It is known that the degradation process of natural rubber is a gradually exothermic reaction. During the degradation of mixed rubbers, four exothermic peaks mainly appear: the first peak appears at 275℃, the second at around 360℃, the third at around 390℃, and the fourth at around 495℃. The heat released by the two samples differs in these four degradation steps, and the intensity of the reaction also differs. Taking the fourth exothermic step as an example, the intensity of the reaction is: Sample B > Sample A, meaning that the stability of Sample B is less than that of Sample A.

[0044] Example 3: Comparison of the physicochemical properties of crepe storage glue and miscellaneous glues The physical and chemical properties of the 13th crepe sheet storage glue prepared in Example 1 and the raw material sample in Example 1 were determined. The determination method is as follows: the plastic initial value (P0) of the rubber is determined according to GB / T 3510-2006 "Unvulcanized rubber Determination of plasticity index", the plasticity retention index (PRI) of the rubber is determined according to GB / T 3517-2014 "Natural rubber Determination of plasticity retention index (PRI)", the ash content of the rubber is determined according to GB / T 4498.1-2013 "Rubber Determination of ash content", the volatile content of the rubber is determined according to GB / T 24131.1-2018 "Raw rubber Determination of volatile content", the impurity content of the rubber is determined according to GB / T 8086-2008 "Natural rubber Determination of impurity content", the nitrogen content of the rubber is determined according to TG / T 3015-2006 "Natural rubber and natural rubber latex Determination of nitrogen content", and the Mooney viscosity of the rubber is determined according to GB / T 1232.1-2000 "Unvulcanized rubber Determination of Mooney viscosity".

[0045] The results show that the rubber (raw material sample) contains 0.54% ash, 0.046% impurities, 0.33% nitrogen, 0.36% volatile, the P0 value is 48.50, the PRI is 29.69, and the Mooney viscosity is 84.850ML 1+4 , 100℃; the 13th crepe sheet storage glue contains 0.39% ash, 0.038% impurities, 0.32% nitrogen, 0.35% volatile, the P0 value is 52.70, the PRI is 67.93, and the Mooney viscosity is 83.250ML 1+4 , 100℃.

[0046] The ash content is an important basis for optimizing the processing technology of natural rubber. The higher the ash content, the lower the aging value, and the poorer the product quality and performance. The lower the ash content, the higher the aging value, and the better the product quality and performance. The ash content in the raw rubber is derived from impurities in addition to its own strain characteristics. The above results show that after the optimization of the crepe sheet process, the ash content of the sample is significantly reduced, which indicates that the optimization of the rubber crepe sheet will affect the ash content, and then affect the aging value of the product, so that the PRI value is increased and the product performance is improved.

[0047] The plastic initial value (P0) is related to the relative molecular mass of natural rubber and is one of the indexes for grading rubber. The larger the P0, the smaller the influence of adverse factors on natural rubber during processing and storage. The above results show that the plastic initial value (P0) of the best process sample is increased by 4.2 compared with the rubber after storage in Example 1, which indicates that the average relative molecular mass of the 13th sample is higher, and the performance of the produced rubber products is better.

[0048] The plastic retention index (PRI) is also one of the important indicators for the classification of the rubber crumbs, which can reflect the oxidation resistance of the natural rubber. The higher the PRI value, the better the aging resistance of the natural rubber, and the more stable the natural rubber products are during the heating process. The above results show that the PRI of the No. 13 sample reached 67.93, which is more than twice the PRI of the rubber crumbs stored after Example 1, indicating that the optimal process of the crumb sheet can improve the PRI value of the sample and make it more resistant to oxidation.

[0049] The impurities are not only one of the important indicators for the classification of the rubber crumbs, but also can cause defects in the rubber products. Therefore, the raw materials with high impurity content generally cannot be used to manufacture products with high performance requirements. The above results show that the impurity content is different under different processing conditions. The impurity content of the No. 13 sample under the optimal process condition is lower than that of the rubber crumbs stored after Example 1, but both are within the impurity content range of the national standard No. 10 rubber.

[0050] The Mooney viscosity of the unvulcanized rubber directly affects the processing performance of the rubber and the physical and mechanical properties of the products. The Mooney viscosity of the natural rubber is negatively correlated with the plasticity. The higher the Mooney viscosity, the smaller the plasticity, and the smaller the Mooney viscosity, the greater the plasticity. Too high or too low Mooney viscosity can affect the physical and mechanical properties of the rubber products. The above results show that the Mooney viscosity values of the rubber crumbs stored after Example 1 and the No. 13 sample are not much different.

[0051] The volatile substances in the natural rubber are mainly water. When the volatile content in the natural rubber is too high, it is easy to mold and even moldy and smelly during storage and transportation. The above results show that the volatile content of the rubber crumbs stored after Example 1 is higher than that of the No. 13 sample, which shows that the No. 13 sample is more resistant to storage and more convenient for transportation after being processed as a rubber crumbs standard rubber.

[0052] The protein in the natural rubber is an important component of the protective layer of the rubber particles, and the nitrogen content of the protein is on average 16%. The higher the nitrogen content, the higher the protein content. Protein is a natural antioxidant that can delay the aging of rubber and make the rubber products more durable. The above results show that the nitrogen content of the rubber crumbs stored after Example 1 is not much different from that of the No. 13 sample, which is related to the amount of washing water during the processing. The water during the washing process not only removes impurities, but also removes part of the protein in the natural rubber.

[0053] In summary, changing the storage method and processing technology of the rubber crumbs has important significance for optimizing the physical and chemical indicators and thermal stability of the natural rubber, and has obvious advantages. Compared with the raw material sample rubber crumbs, it has been greatly improved. In the industrial production process, it is recommended to select the No. 13 process to process the rubber crumbs crumb sheet.

[0054] From the above embodiment, the application provides a storage method and application of the miscellaneous glue. The application innovates the storage method of the miscellaneous glue, deeply researches and analyzes the processing factors, and explores the influence of the crepe process on the performance of the miscellaneous glue. Specifically, the miscellaneous glue is first subjected to crepe processing, and the physical and chemical indexes PRI are used for characterization, so that the optimal processing process is obtained. Then, the TG, DSC and physical and chemical properties are analyzed, so that the optimal crepe storage process is obtained, and data support is provided for the crepe storage of the miscellaneous glue.

[0055] The above only describes the preferred embodiments of the application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the application, and these improvements and refinements should also be considered as the protection scope of the application.

Claims

1. A method for storing miscellaneous gums, characterized in that, Includes the following steps: (1) The impurities are processed into crepes to obtain crepes; (2) Store the crepes as hanging pieces for 2-3 days.

2. The storage method according to claim 1, characterized in that, In step (1), the miscellaneous glue is miscellaneous glue that has been stored for one week or more.

3. The storage method according to claim 1, characterized in that, In step (1), the crepe is processed 5-11 times.

4. The storage method according to claim 1, characterized in that, In step (1), the rinsing rate of the crepe treatment is 5-7 L / h.

5. The storage method according to claim 1, characterized in that, In step (1), the thickness of the crepe is 7-8 mm.

6. The storage method according to claim 1, characterized in that, In step (2), the method of hanging the piece is to hang the crepe-processed glue on the bamboo pole.

7. The storage method according to claim 1, characterized in that, In step (2), the storage temperature is 28-35℃.

8. The use of the storage method according to any one of claims 1-7 in improving the thermal stability of heterogeneous gums.

9. The use of the storage method according to any one of claims 1-7 in improving the physicochemical properties of impurities.

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