Low-impurity constant Mooney viscosity environmentally friendly natural rubber and preparation method thereof

Abstract

The present invention discloses an environmentally friendly natural rubber with low impurities and constant Mooney viscosity and a preparation method thereof, belonging to the technical field of natural rubber processing. The method comprises adding a certain proportion of a constant viscosity agent, hydrazine ethanol, to WF rubber and then filtering the rubber with a rubber filter. The production method of the present invention is simple, low-cost, and high-efficiency. The obtained natural rubber with low impurities and constant Mooney viscosity has a low impurity content and excellent mechanical properties; the Mooney viscosity is stable, and it can be directly mixed with other materials without mastication to prepare low-impurity rubber products. The rubber can be widely used in various thin-walled rubber products and high-end rubber products, and has high promotion value.

Description

Technical Field

[0001] The present invention relates to the technical field of natural rubber processing, and in particular to a low-impurity, constant-Mooney viscosity, environmentally friendly natural rubber with low impurity content, constant Mooney viscosity, and good performance consistency, and a preparation method thereof. Background Art

[0002] Rubber production includes both natural rubber production and recycled rubber production from waste rubber products. Recycled rubber is typically produced using a rubber strainer, a type of rubber filter extruder. Waste rubber products often contain impurities such as iron pins and nylon rope. Therefore, when using waste rubber for production, the raw material must be filtered before extrusion. The waste rubber feedstock enters the barrel through the strainer's feeding system, where it undergoes a series of processing steps, including shearing and mixing. Pressure pushes the rubber toward the filter screen at the front end of the extruder barrel, where the rubber passes through the screen while the impurities are retained on the other side, achieving the desired filtration effect.

[0003] Impurities in natural rubber are primarily foreign substances introduced during the collection and processing of latex or other rubber products. Some of these impurities are caused by unclean tapping trunks, rubber cups, rubber tongues, and rubber drums, as well as by wind, rain, low-line tapping, and improper collection and handling. Some are introduced by dilution water during processing, and some are contaminated during drying, packaging, transportation, and storage. These impurities can cause defects in finished products, reducing their performance, such as tear resistance, abrasion resistance, and high heat generation. They are particularly harmful to thin-walled products like bladders, often causing leaks or explosions. Therefore, natural rubber with high impurity levels cannot be directly used in products requiring high performance, making it difficult for factories producing these products to source suitable natural rubber.

[0004] Mooney viscosity is an indicator of rubber processing performance, molecular weight, and distribution. Generally speaking, a high Mooney viscosity indicates relatively high hardness and physical strength, making uniform mixing and extrusion difficult. A low Mooney viscosity indicates a low molecular weight, making processing easier but prone to sticking to rollers. Excessively low Mooney viscosity results in low tensile strength in the vulcanized product, impacting product performance. Latex is an agricultural product. Depending on the tapping time and processing method, the Mooney viscosity of natural rubber produced from latex varies. Furthermore, the Mooney viscosity of this natural rubber remains constant for a short time, affecting its processing performance and making it difficult for factories to control the process during the production of natural rubber plastic compounds. Therefore, researchers have developed a new type of natural rubber—Constant Mooney Rubber (CV). Currently, Constant Mooney Rubber (CV) is typically produced using the waterline method by adding a constant viscosity agent to the latex, or using a dry mill with a constant viscosity agent. The dry mixer operates on the principle that helically arranged moving blades mounted on a rotating shaft and stationary blades mounted on the housing move relative to each other, shearing and squeezing the rubber materials within the machine, resulting in a uniform blend of the various rubber materials. The waterline method is complex and inefficient. The Hengmoney rubber produced by the dry mixer has a high impurity content and cannot meet the requirements of rubber for products with higher performance requirements. Summary of the Invention

[0005] After in-depth research, the inventors of the present invention found that by filtering WF rubber with a rubber filter, selecting a suitable filter screen, and completing the filtration within a certain period of time, natural rubber with a low impurity content can be obtained. At the same time, during the filtration process, the WF rubber is also sheared, which is equivalent to plasticizing, and the Mooney value also drops to an appropriate range. The inventors further found that the low-impurity environmentally friendly natural rubber prepared above is then treated with a constant viscosity agent hydrazine ethanol. The resulting low-impurity constant Mooney viscosity environmentally friendly natural rubber not only has a low impurity content, but also has a very stable Mooney viscosity. The Mooney viscosity change value within 12 months after leaving the factory is less than 10, and no plasticizing is required, and it can be directly used in mixing production. Based on these research results, protection of the following technical solutions is requested:

[0006] A method for preparing environmentally friendly natural rubber with low impurities and constant Mooney viscosity comprises the following steps:

[0007] (1) crushing and weighing natural rubber;

[0008] (2) spraying the constant viscosity agent hydrazine alcohol onto the product obtained in the above step (1);

[0009] (3) adding the product obtained in step (2) into a rubber filter and filtering;

[0010] (4) The product obtained in step (3) is subjected to conventional briquetting, cooling, and classification processes to obtain environmentally friendly natural rubber with low impurities and constant Mooney viscosity.

[0011] The natural raw rubber is SCRWF rubber.

[0012] The specific method of filtration in step (3) is as follows: the product obtained in step (2) is placed into the feed port of the rubber filter, the machine is turned on, the head temperature is controlled between 70-100 ° C, the screw speed is controlled at about 40-52 r / min, the mesh size of the filter installed in the rubber filter is 80-120 mesh, the screw diameter of the rubber filter is 150-250 mm, the aspect ratio is 4.5-5.5, and the filtration time in the rubber filter is 3-6 min.

[0013] Preferably, in step (3), the screw speed is controlled at about 50 r / min, the screw diameter of the rubber filter is 200 mm, and the aspect ratio is 5.

[0014] Preferably, the filter mesh number of the rubber filter is 100 meshes.

[0015] Preferably, in step (3), 100 kg of rubber is filtered out every 3-6 minutes, and the filter screen is replaced every time 1000 kg of rubber is filtered.

[0016] Preferably, based on the amount of natural rubber, the amount of the constant viscosity agent hydrazinoethanol is 2‰-6‰.

[0017] Preferably, based on the amount of natural rubber, the amount of the constant viscosity agent hydrazine ethanol is 4‰.

[0018] A low-impurity, constant-Mooney-viscosity, environmentally friendly natural rubber is prepared by any of the above methods.

[0019] Preferably, the low-impurity constant Mooney viscosity environmentally friendly natural rubber has an impurity content of less than 0.02%, a Mooney viscosity ML(1+4) at 100°C that can be controlled between 50-70, and a Mooney viscosity change value of less than 10 within 12 months.

[0020] Rubber strainers are generally used in the production process of mixed rubber, which belongs to the wet rubber making process; while the equipment used for the normal dry production of natural rubber or constant Mooney natural rubber is a dry mixer, which does not require a rubber strainer. At present, WF rubber is mainly used in the waterline process. The present invention is the first to use a rubber strainer instead of a dry mixer for the dry production of natural rubber. This replacement does not add additional steps and does not generate pollution. It not only reduces the impurity content, but also plasticizes the WF rubber, further reducing the Mooney of the WF rubber. By adding a constant viscosity agent, the Mooney of the WF rubber is made constant, and it can be directly mixed subsequently, avoiding the risk of introducing impurities in the conventional plasticizing process. It kills two birds with one stone and breaks the confinement of traditional dry rubber making. The process of the present invention only needs to replace the dry mixer in the existing natural rubber dry line processing production process with a rubber strainer, and does not require changing other equipment and processes. It is currently the best method for producing low-impurity constant Mooney natural rubber and is of great significance for the development of high-performance thin-walled natural rubber products.

[0021] The low-impurity, constant Mooney viscosity, environmentally friendly natural rubber produced by the present invention features low impurity content, minimal Mooney viscosity variation, and excellent performance consistency, making it ideal for the production of high-end, thin-walled natural rubber products. The constant viscosity agent, hydrazine ethanol, used in the production of this low-impurity, constant Mooney viscosity natural rubber is safe, environmentally friendly, and does not corrode rubber filters. The entire processing process generates no dust or wastewater, making it very friendly to both personnel and the environment.

[0022] The low-impurity constant Mooney viscosity environmentally friendly natural rubber prepared by the method of the present invention has the properties of low impurity content, small Mooney viscosity change, and good performance consistency. The impurity content is less than 0.02%, and its Mooney viscosity ML(1+4) at 100°C can be controlled between 50 and 70. The change value of the Mooney viscosity within 12 months is less than 10. DETAILED DESCRIPTION

[0023] The present invention is further described below with reference to specific examples, and the protection content of the present invention is not limited to the following examples. Without departing from the spirit and scope of the invention, changes and advantages that can be thought of by those skilled in the art are included in the present invention, and are protected by the appended claims. The experimental methods for which specific conditions are not specified in the following examples are generally based on conventional conditions. The materials used in the following examples, unless otherwise specified, can be obtained from commercial channels. The experimental methods in the examples, unless otherwise specified, are all conventional methods; the percentages in the examples, unless otherwise specified, are all weight percentages.

[0024] Description of materials used in the examples:

[0025] Hydrazinoethanol, CAS No. 109-84-2, is commercially available.

[0026] Natural raw rubber brand: SCRWF rubber, WF rubber is a standard rubber processed from fresh latex and is commercially available.

[0027] The rubber strainer used in each embodiment of the present invention is an XJL-200 type rubber strainer, which is a screw type with equal depth and equal spacing, a screw diameter of 200 mm, and an aspect ratio of 5.

[0028] The method for preparing the low-impurity constant Mooney viscosity environmentally friendly natural rubber of the present invention comprises the following steps:

[0029] (1) Take the natural raw rubber, crush it, weigh it and set aside.

[0030] (2) Spraying the constant viscosity agent hydrazine alcohol onto the product obtained in the above step (1).

[0031] (3) Add the product obtained in step (2) to a rubber filter and filter:

[0032] ①Preparation before operation

[0033] Before starting the machine, open the machine head and check whether there is any residual glue or impurities in the machine. If there is, clean it up in time. Then stick a wire filter of appropriate mesh size on the filter plate, and then close the machine head and lock it.

[0034] ②Operation method

[0035] Place the cut WF rubber into the strainer's feed port. Turn on the machine, and the screw will push the material toward the strainer head. While the machine is running, the strainer's cooling water system should be turned on to ensure the head temperature remains between 70-100°C to avoid overheating. Keep the screw speed at approximately 50 rpm, ensuring that 100 kg of WF rubber can be filtered every 3-6 minutes (depending on the mesh size). Replace the filter screen every 1000 kg to ensure optimal straining quality.

[0036] (4) The product obtained in step (3) is subjected to conventional briquetting, cooling, and classification processes to obtain environmentally friendly natural rubber with low impurities and constant Mooney viscosity.

[0037] Example 1

[0038] Crumble the WF rubber and weigh it for later use. Weigh 5‰ of the WF rubber's weight as a constant viscosity agent, hydrazine ethanol, and spray it on the surface of the rubber block. Then, filter it through a rubber strainer without a filter for 4 minutes. After cooling and briquetting, you'll obtain environmentally friendly natural rubber with a constant Mooney viscosity.

[0039] Example 2

[0040] The process was carried out according to Example 1, but an 80-mesh filter was installed on the filter.

[0041] Example 3

[0042] Crumble the WF rubber and weigh it for later use. Weigh 2‰ of the WF rubber's weight as a constant viscosity agent, hydrazine ethanol, and spray it onto the surface of the rubber block. Then, filter it through a rubber strainer with an 80-mesh filter for 3 minutes. After cooling and briquetting, you'll obtain environmentally friendly natural rubber with low impurities and constant Mooney viscosity.

[0043] Example 4

[0044] Crumble the WF rubber and weigh it for later use. Weigh 6‰ of the WF rubber's weight as a constant viscosity agent, hydrazine ethanol, and spray it onto the surface of the rubber block. Then, filter it through a rubber strainer fitted with a 120-mesh filter for 6 minutes. After cooling and briquetting, you'll obtain environmentally friendly natural rubber with low impurities and constant Mooney viscosity.

[0045] Example 5

[0046] Crumble the WF rubber and weigh it for later use. Spray 4‰ of the WF rubber's weight with hydrazine alcohol, a constant viscosity agent, onto the surface of the rubber block. Then, filter the rubber block through a rubber strainer fitted with a 100-mesh filter for 4 minutes. After cooling and briquetting, you'll obtain environmentally friendly natural rubber with low impurities and constant Mooney viscosity.

[0047] Example 6

[0048] Crumble the WF rubber and weigh it for later use. Spray 4‰ of the WF rubber's weight with hydrazine alcohol, a constant viscosity agent, onto the surface of the rubber block. Then, filter it through a rubber strainer with a 70-mesh filter for 2 minutes. After cooling and briquetting, you'll obtain environmentally friendly natural rubber with low impurities and constant Mooney viscosity.

[0049] Example 7

[0050] Crumble the WF rubber and weigh it for later use. Spray 4‰ of the WF rubber's weight with hydrazine alcohol, a constant viscosity agent, onto the surface of the rubber block. Then, filter it through a rubber strainer fitted with a 130-mesh filter for 7 minutes. After cooling and briquetting, you'll obtain environmentally friendly natural rubber with low impurities and constant Mooney viscosity.

[0051] Comparative Example

[0052] Standard natural rubber (WF)

[0053] Performance Testing

[0054] Inspection basis:

[0055] GB / T 8086-2019 Determination of impurity content of natural raw rubber

[0056] GB / T 1232.1-2000 Determination of Mooney viscosity of unvulcanized rubber

[0057] The impurity content and Mooney viscosity of the products in Examples 1-7 were tested, as shown in Table 1. Examples 2-5 all met the requirements for environmentally friendly natural rubber with low impurities and constant Mooney viscosity. The impurity content of Example 1, the impurity content and Mooney viscosity of Example 6, and the Mooney viscosity of Example 7 all failed to meet the requirements for environmentally friendly natural rubber with low impurities and constant Mooney viscosity.

[0058] Table 1

[0059]

[0060] The products in Examples 1-5 and the comparative example were tested for Mooney viscosity every month (M represents month) for one year after leaving the factory. The Mooney viscosity of the products in Examples 1-5 was stable, and the Mooney viscosity showed little change compared to standard natural rubber, as shown in Table 2.

[0061] Table 2

[0062]

Claims

1. A method for preparing low-impurity constant Mooney viscosity environmentally friendly natural rubber, characterized in that: The steps include: (1) Take natural raw rubber WF rubber, crush it, weigh it and set aside; (2) spraying the constant viscosity agent hydrazine alcohol onto the product obtained in the above step (1); based on the amount of natural rubber, the amount of the constant viscosity agent hydrazine alcohol is 2‰-6‰; (3) Adding the product obtained in step (2) to a rubber filter for filtration: placing the product obtained in step (2) into the feed port of the rubber filter, turning on the machine, controlling the head temperature between 70-100° C., controlling the screw speed at about 40-52 r / min, the screw diameter of the rubber filter being 150-250 mm, the aspect ratio being 4.5-5.5, and the filtration time in the rubber filter being 3-6 min; and the mesh size of the filter screen installed in the rubber filter being 80-120 meshes; (4) The product obtained in step (3) is subjected to conventional briquetting, cooling, and classification processes to obtain environmentally friendly natural rubber with low impurities and constant Mooney viscosity.

2. The preparation method according to claim 1, wherein: In step (3), the screw speed is controlled at about 50 r / min, the screw diameter of the rubber filter is 200 mm, and the aspect ratio is 5.

3. The preparation method according to claim 1, wherein: The filter mesh number of the rubber filter is 100 mesh.

4. The preparation method according to claim 1, wherein: In step (3), ensure that 100 kg of rubber is filtered out every 3-6 minutes, and replace the filter screen every time 1000 kg of rubber is filtered.

5. The preparation method according to claim 1, wherein: Based on the amount of natural raw rubber, the amount of constant viscosity agent hydrazine ethanol is 4‰.

6. An environmentally friendly natural rubber with low impurities and constant Mooney viscosity, characterized by: It is prepared by the method according to any one of claims 1 to 5.

7. The low-impurity constant Mooney viscosity environmentally friendly natural rubber according to claim 6, characterized in that: The impurity content is less than 0.02%, the Mooney viscosity ML (1+4) at 100°C can be controlled between 50-70, and the change value of the Mooney viscosity within 12 months is less than 10.

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