A preparation method of light-colored high-strength low-constant viscosity rubber

Abstract

The invention discloses a kind of preparation method of light-colored high-strength low-constant-viscosity rubber, the preparation method comprises the following steps:Step (1) prepares hydroxylamine constant-viscosity solution and accelerator solution;Step (2) peptizer is mixed with fresh latex and is made into mother liquor;Step (3) adds accelerator solution in latex, while adding and stirring, then adds hydroxylamine constant-viscosity solution, then adds mother liquor in latex, continues stirring 3 10min;Step (4) sampling and detection mixes the concentration of latex, then calculates coagulation acid amount;The latex solution after stirring is added to long groove together with coagulating acid and flow and solidifies, slaking;The clot of slaking is dehydrated through tabletting machine and granulator combination and then low temperature shallow layer is dried, obtains light-colored high-strength low-constant-viscosity rubber.The rubber performance obtained by the present invention is excellent, and color is light, odorless, is suitable for downstream product enterprise to make kind of product.

Description

Technical Field

[0001] The present invention relates to the field of constant viscosity rubber, and in particular to a method for preparing light-colored, high-strength, low-constant viscosity rubber. Background Art

[0002] The Mooney viscosity of natural rubber is an indicator of the rubber's processing performance, molecular weight, and distribution range. Generally speaking, a high Mooney viscosity indicates a high molecular weight, a wide distribution range, and high relative hardness and physical strength, making it difficult to mix and extrude the rubber.

[0003] Natural rubber (NR) typically undergoes transportation and storage during the process from raw rubber to rubber products. This is primarily due to the presence of aldehyde groups in the rubber's molecular chains, which crosslink the rubber during storage. This increased Mooney viscosity causes the rubber to harden and crystallize, making it difficult to cut and process the raw rubber, increasing the difficulty of plasticizing. This also impacts the mixing and extrusion processes, prolonging mixing time, resulting in poor product consistency and low production efficiency, increasing production and processing costs for tire and rubber product manufacturers.

[0004] The problem of increased Mooney viscosity can be effectively solved by introducing a constant viscosity agent into natural rubber to inhibit the cross-linking effect caused by aldehyde groups. However, due to the addition of the constant viscosity agent, the tensile strength of the product after vulcanization is low, affecting the product performance.

[0005] Constant viscosity products are widely used in the sealing and shock absorbing parts industries due to their low heat generation, high rebound and constant Mooney viscosity.

[0006] The constant viscosity products currently on the market are manufactured from three types of raw materials: fresh latex, solid base rubber block, and standard rubber. The constant viscosity rubbers produced from these three raw materials have obvious differences in product performance. The constant viscosity rubber from fresh latex is light in color, low in impurity content, and has good heat generation performance, but has low tensile strength (less than 17%); the constant viscosity rubber made from rubber block raw materials is dark in color, has a bad odor, poor heat generation, high in impurity content, and high in tensile strength, but has low elongation at break (less than 750%), and cannot be used in product industries that have requirements for odor and color; the constant viscosity rubber made from standard rubber raw materials has poor storage hardening value and insufficient constant viscosity stability.

[0007] CN108440800A discloses a natural rubber with a low Mooney viscosity and a preparation method thereof. The constant viscosity rubber is produced by dry mixing using a mixing process with standard rubbers of different qualities and a low molecular weight rubber synthetic rubber with a low Mooney viscosity as a plasticizer. The constant viscosity rubber produced by this patent has low tensile strength and elongation at break.

[0008] CN103627044A discloses a constant-viscosity natural rubber and a preparation method thereof. The method comprises adding ≥2.5% of a hydroxylamine constant-viscosity solution and ≥8.0% of a hydrazine hydrate solution to fresh latex. Due to the toxicity of hydrazine hydrate, there are safety hazards during operation. The stirring time during the production process is as long as 20 minutes or more, and the latex is prone to deterioration before solidification. Due to the negative impact of hydroxylamine constant-viscosity agents on the physical properties of natural rubber, the natural rubber processed by this method has low tensile strength, which cannot meet the needs of downstream product customers. Summary of the Invention

[0009] In view of the shortcomings of the existing technology, the present invention provides a method for preparing light-colored, high-strength, low-constant viscosity rubber. The present invention mainly focuses on constant viscosity rubber made from fresh latex. Constant viscosity agents, accelerators and plasticizers are applied to latex to produce low-Mooney, high-performance, light-colored constant viscosity products. The produced constant viscosity rubber has high tensile strength and elongation at break.

[0010] To solve the above technical problems, the technical solution of the present invention is as follows: a method for preparing light-colored, high-strength, low-constant-viscosity rubber, the preparation method comprising the following steps:

[0011] Step (1) preparing a hydroxylamine constant viscosity agent solution and an accelerator solution;

[0012] Step (2) mixing the peptizer and the fresh latex to form a mother liquor;

[0013] Step (3) adding the hydroxylamine viscosity-stabilizing agent solution to the mother liquor while stirring, and then adding the accelerator solution to the mother liquor, and continuing stirring for 3-10 minutes;

[0014] Step (4) sampling and testing the concentration of the mixed latex, and then calculating the amount of coagulation acid; adding the stirred latex solution and the coagulation acid into a long tank for coagulation and maturation; dehydrating the matured clot by a tablet press and a granulator combination and then shallow drying at 105-110° C. to obtain a light-colored, high-strength, low-constant-viscosity rubber.

[0015] Preferably, the hydroxylamine constant viscosity agent is added to water and dissolved to prepare a hydroxylamine constant viscosity agent solution with a concentration of 4-10%. The amount of the hydroxylamine constant viscosity agent added is 0.5-1.0% of the dry rubber content in the latex.

[0016] Preferably, the hydroxylamine constant viscosity agent is neutral hydroxylamine sulfate.

[0017] Preferably, the accelerator is dissolved in 1.5-2.5% ammonia water at a concentration of 0.1-0.3% to prepare an accelerator solution; the amount of the accelerator added is 0.08-0.15% of the dry rubber content in the latex.

[0018] Preferably, the accelerator is N-cyclohexyl-2-benzothiazolesulfenamide (CBS).

[0019] Preferably, the added amount of the peptizer (plasticizer) accounts for 0.05-0.1% of the dry rubber content in the fresh latex, and the mass ratio of the peptizer to the latex in the mother liquor is: 0.05-0.1:1.5-2.5; the peptizer is pentachlorothiophenol, and the peptizer is pre-added to the fresh latex to make a mother liquor to improve the dispersion.

[0020] Preferably, after stirring in step (4), sampling is taken to detect the dry rubber content, and water is added to dilute it to 20-23% to ensure the continuous stability of the product quality, and then stirring is continued for 1-3 minutes; 2-4% concentration of formic acid or 3-5% concentration of acetic acid solution is added and put into a long tank for coagulation; after the aging time is 10-15 hours, the material is dehydrated and torn by a tablet press and a granulator, and shallowly dried at 105-110° C. to obtain a light-colored, high-strength, low-constant-viscosity rubber.

[0021] The present invention features the following: The present invention utilizes a combination of a constant viscosity agent, an accelerator, and a plasticizer to modify rubber; the constant viscosity agent primarily functions to reduce the Mooney content of natural rubber, while also affecting the decline in plasticity, and is characterized by a significant impact on the product's physical properties, namely, tensile strength, reducing tensile strength; the accelerator also primarily functions to reduce the Mooney content of natural rubber, and has a stabilizing effect without significantly reducing the product's physical properties. The plasticizer primarily maintains the initial plasticity value and enhances physical properties. The constant viscosity rubber product produced by the present invention is light in color, odorless, and suitable for downstream product manufacturers to manufacture such products.

[0022] In addition, the rubber prepared by the present invention has excellent performance: the Mooney viscosity of the rubber product after the constant viscosity agent, accelerator and plasticizer act together is between 45 and 60, and it has high tensile strength and elongation at break, good heat generation performance, and meets the requirements of shock-absorbing products for tensile strength greater than 20%, elongation at break greater than 800%, and plasticity retention rate greater than 90; in terms of performance, it has far exceeded CN103627044 B / 103627044A, a constant viscosity natural rubber and its preparation method. The product not only meets the needs of shock-absorbing products, but also meets the needs of natural rubber materials for sealing products.

[0023] If only a single product is used, such as hydroxylamine-based constant viscosity agents, the tensile strength of the product is low, only 14-15%, and the highest is only 16%, which cannot meet the requirement of strength greater than 20%;

[0024] If hydroxylamine + plasticizer, or hydroxylamine + accelerator is used, the plasticity and Mooney viscosity of the product are too low, and the initial plasticity value P0 is only between 16-20 (the initial plasticity value P0 of normal hydroxylamine constant viscosity adhesive is greater than 26, and the initial plasticity value of environmentally friendly constant viscosity adhesive is greater than 30), which affects the use of downstream products (sticky roller);

[0025] Furthermore, after numerous tests, we discovered that the order in which the three additives are added affects the ability to produce a constant-viscosity rubber that meets the required standards. Adding the three additives in the wrong order can negatively impact the quality of the latex. If the additives are not added in the correct order, the latex will deteriorate and flocculate before the other coagulants are added, making it impossible to produce a constant-viscosity product. Therefore, we first add the alkaline accelerator solution, followed by the constant-viscosity solution, and finally the mother liquor.

[0026] Compared with the prior art, the present invention has the following beneficial effects: the present invention adopts three constant viscosity agents + plasticizer + accelerator to modify rubber, the various amounts used are the lowest, and the overall cost is the lowest; using a single constant viscosity agent, the amount used is far more than double the current amount; none of the three constant viscosity agents are hazardous chemicals and do not harm employees during production and use; the rubber produced by the present invention has excellent performance, light color, and no odor, and is suitable for downstream product companies to produce various products. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the experimental result after the wrong order of adding materials. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and specific examples, but the present invention is not limited to the following technical solution. In the following examples, 1 ton of latex corresponds to 6-9 kg of 85% formic acid or 85% acetic acid, and the high-concentration formic acid or acetic acid is diluted to a specified concentration.

[0029] Example 1

[0030] 1. Take 300kg of latex with a dry rubber content of 30%, add 0.09kg of hydroxylamine sulfate at a rate of 0.1%, and stir to dissolve the hydroxylamine sulfate in 1kg of water; add 0.15% CBS, 0.135kg, and dissolve it in 0.5kg of 2% ammonia water; add 0.072kg of pentachlorothiophenol at a rate of 0.08% and prepare a mother liquor with 2kg of latex.

[0031] Add CBS ammonia solution to the latex while stirring, then add hydroxylamine sulfate solution, and gradually add the prepared peptizer mother solution, stirring for 5 minutes. If the hydroxylamine sulfate solution is added first in this step, the stirring time is less than 5 minutes, and flocculation occurs, such as Figure 1 shown.

[0032] 2. After stirring, take a sample to test the dry glue content, dilute it with water to 23%, and stir for another minute;

[0033] 3. Place it in a long tank together with 3% formic acid solution for solidification;

[0034] 4. After 12 hours of aging, the material is passed through a tabletting machine (≤6mm) and a granulator (3-5mm) for dehydration and tearing, and then dried at a shallow low temperature of 108°C to obtain a constant viscosity block.

[0035] Example 2

[0036] 1. Take 300 kg of latex with a dry rubber content of 30%, add 0.072 kg of hydroxylamine sulfate (calculated as 0.08%), and stir to dissolve the hydroxylamine sulfate in 1 kg of water; add 0.15% CBS (calculated as 0.135 kg) and dissolve it in 0.5 kg of 2% ammonia water; add 0.08% pentachlorothiophenol (calculated as 0.072 kg) and prepare a mother liquor with 2 kg of latex.

[0037] 2. Add CBS ammonia solution to the latex while stirring, then add hydroxylamine sulfate solution, and gradually add the prepared peptizer mother solution, stirring for 5 minutes;

[0038] 3. After stirring, take a sample to test the dry glue content, dilute it with water to 23%, and stir for another minute;

[0039] 4. Place it in a long tank together with 3% formic acid solution for solidification;

[0040] 5. After 12 hours of aging, the material was dehydrated and torn by a tablet press and granulator, and then dried at 106°C in a shallow layer to obtain a constant viscosity block; Example 3

[0041] 1. Take 300 kg of latex with a dry rubber content of 30%, add 0.045 kg of hydroxylamine sulfate (calculated at 0.05%), and stir to dissolve the hydroxylamine sulfate in 1 kg of water; add 0.09 kg of CBS (calculated at 0.10%) and dissolve it in 0.5 kg of 2% ammonia water; add 0.072 kg of pentachlorothiophenol (calculated at 0.08%) and prepare a mother liquor with 2 kg of latex.

[0042] 2. Add CBS ammonia solution to the latex while stirring, then add hydroxylamine sulfate solution, and gradually add the prepared peptizer mother solution, stirring for 10 minutes;

[0043] 3. After stirring, take a sample to test the dry glue content, dilute it with water to 23%, and stir for another minute;

[0044] 4. Place it in a long tank together with 2.5% formic acid solution for solidification;

[0045] 5. After 13 hours of aging, the material was dehydrated and torn by a tablet press and granulator, and then shallowly dried at 108°C to obtain a constant viscosity block; Example 4

[0046] 1. Take 300kg of latex with a dry rubber content of 30%, add 0.09kg of hydroxylamine sulfate (calculated as 0.10%), and stir to dissolve the hydroxylamine sulfate in 1kg of water; add 0.12% CBS (calculated as 0.108kg) and dissolve it in 0.5kg of 2% ammonia water; add 0.09kg of pentachlorothiophenol (calculated as 0.1%) and prepare a mother liquor with 2kg of latex.

[0047] 2. Add CBS ammonia solution to the latex while stirring, then add hydroxylamine sulfate solution, and gradually add the prepared peptizer mother solution, stirring for 8 minutes;

[0048] 3. After stirring, take a sample to test the dry glue content, dilute it with water to 23%, and stir for another minute;

[0049] 4. Place it in a long tank together with 2% formic acid solution to solidify;

[0050] 5. After 12 hours of aging, the material was dehydrated and torn by a tablet press and granulator, and then shallowly dried at 108°C to obtain a constant viscosity block; Example 5

[0051] 1. Take 300 kg of latex with a dry rubber content of 30%, add 0.072 kg of hydroxylamine sulfate (calculated as 0.08%), and stir to dissolve the hydroxylamine sulfate in 1 kg of water; add 0.08% CBS (calculated as 0.072 kg) and dissolve it in 0.5 kg of 2% ammonia water; add 0.08% pentachlorothiophenol (calculated as 0.072 kg) and prepare a mother liquor with 2 kg of latex.

[0052] 2. Add CBS ammonia solution to the latex while stirring, then add hydroxylamine sulfate solution, and gradually add the prepared peptizer mother solution, stirring for 5 minutes;

[0053] 3. After stirring, take a sample to test the dry glue content, dilute it with water to 23%, and stir for another minute;

[0054] 4. Place it in a long tank together with 3.5% formic acid solution for solidification;

[0055] 5. After 14 hours of aging, the material is dehydrated and torn by a tablet press and granulator, and then shallowly dried to obtain a constant viscosity block;

[0056] Data analysis confirmation

[0057] The Mooney test was performed using an Alpha MV-2000 Mooney machine. The vulcanized rubber formula used was a pure rubber formula, as shown in Table 1. The test method and experimental results are shown in Table 2.

[0058] Table 1 ACS1 natural rubber pure rubber formula

[0059]

[0060] Table 2

[0061]

[0062]

[0063] From the analysis results in Table 2, it can be seen that by combining the three constant viscosity agents, the Mooney value can be controlled between 45-60, the Mooney storage hardening value is within 5 values, the P0 storage hardening value is within 3 values, the tensile strength is greater than 20, and the elongation at break is greater than 800. Both the tensile strength and the elongation at break meet the requirements of the product customers. However, the tensile strength produced by ordinary constant viscosity agents is reduced. By combining the three constant viscosity agents, the plasticity retention rate is increased, indicating that the antioxidant performance is improved. The other operating methods of Comparative Examples 1 to Comparative Examples 4 are the same as those of Example 1.

[0064] The product can be obtained by adjusting the proportion of constant viscosity agent according to the customer's Mooney demand range (low Mooney demand, increase the dosage, high Mooney demand, reduce the dosage). In order to reduce production costs, the proportion of constant viscosity agent used is based on the minimum amount to achieve the desired effect.

[0065] The above disclosure is merely a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention still fall within the scope of the present invention.

Claims

1. A method for preparing light-colored, high-strength, low-constant-viscosity rubber, characterized in that: The preparation method comprises the following steps: Step (1) preparing a hydroxylamine constant viscosity agent solution and an accelerator solution; the hydroxylamine constant viscosity agent is neutral hydroxylamine sulfate; Step (2) mixing a peptizer with fresh latex to prepare a mother liquor, wherein the peptizer is pentachlorothiophenol; Step (3) adding the accelerator solution to the latex while stirring, then adding the hydroxylamine viscosity constant agent solution, and then adding the mother liquor to the latex, and continuing to stir for 3-10 minutes; the accelerator is N-cyclohexyl-2-benzothiazole sulfenamide; Step (4) sampling and testing the concentration of the mixed latex, and then calculating the amount of coagulation acid; adding the stirred latex solution and the coagulation acid into a long tank for coagulation and maturation; dehydrating the matured clot by a tablet press and a granulator combination and then shallow drying at 105-110° C. to obtain a light-colored, high-strength, low-constant-viscosity rubber.

2. The method for preparing the light-colored, high-strength, low-constant-viscosity rubber according to claim 1, characterized in that: The hydroxylamine constant viscosity agent is added into water and dissolved to prepare a hydroxylamine constant viscosity agent solution with a concentration of 4-10%. The added amount of the hydroxylamine constant viscosity agent is 0.5-1.0‰ of the dry glue content in the latex.

3. The method for preparing the light-colored, high-strength, low-constant-viscosity rubber according to claim 1, characterized in that: The accelerator is dissolved in 1.5-2.5% ammonia water at a concentration of 0.1-0.3% to prepare an accelerator solution; the added amount of the accelerator is 0.08-0.15% of the dry rubber content in the latex.

4. The method for preparing light-colored, high-strength, low-constant-viscosity rubber according to claim 1, characterized in that: The added amount of the peptizer accounts for 0.05-0.1% of the dry rubber content in the fresh latex, and the mass ratio of the peptizer to the latex in the mother liquor is: 0.05-0.1:1.5-2.

5.

5. The method for preparing light-colored, high-strength, low-constant-viscosity rubber according to claim 1, characterized in that: Step (4) After stirring, sampling is performed to detect the dry rubber content, and water is added to dilute the mixture to 20-23%, and the mixture is stirred for 1-3 minutes; the mixture is placed in a long tank together with a 2-4% concentration of formic acid or a 3-5% concentration of acetic acid solution for coagulation; after a aging time of 10-15 hours, the mixture is dehydrated and torn by a tablet press and a granulator, and shallowly dried at 105-110° C. to obtain a light-colored, high-strength, low-constant-viscosity rubber.

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