Coagulation treatment method of styrene butadiene rubber latex

Abstract

The invention belongs to the technical field of synthetic rubber, and particularly relates to a coagulation treatment method of styrene butadiene rubber latex. According to the method, poly (diallyldimethylammonium chloride) is used as a coagulant, a sodium chloride aqueous solution is used as a coagulation mother solution, and sulfuric acid is used as a pH regulator; the method comprises the following steps: adding a coagulant into the coagulation mother liquor, adding styrene-butadiene rubber latex for multiple times, and adjusting the pH value with sulfuric acid to keep acidity; according to the invention, the cost is effectively reduced, the production efficiency is improved, and the stress at definite elongation of the raw rubber is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of synthetic rubber, and in particular relates to a coagulation treatment method for styrene-butadiene rubber latex. Background Art

[0002] Styrene butadiene rubber (SBR), also known as polystyrene butadiene copolymer, is close to natural rubber in physical structure, processing and product performance. Some properties such as wear resistance, heat resistance, aging resistance and vulcanization speed are better than natural rubber. It can be used with natural rubber and a variety of synthetic rubbers. It is widely used in the production of tires, tapes, hoses, wires and cables, medical equipment and various rubber products. It is the largest general synthetic rubber variety and one of the earliest rubber varieties to achieve industrial production.

[0003] Butadiene styrene rubber is generally produced by emulsion polymerization, with butadiene and styrene as the main monomers, and other auxiliary chemical raw materials. Under certain process conditions, butadiene styrene rubber slurry is first produced by emulsion polymerization, and after removing the unconverted monomers in the slurry, the product rubber is produced through processes such as coagulation and drying. Among them, the coagulation process has a certain impact on the production efficiency and the performance of the raw rubber.

[0004] The existing post-coagulation treatment method of styrene-butadiene rubber latex has been used since the 1980s. The coagulant used is a 10% dinitrile diamine formaldehyde condensate (CA for short) solution, and the 35-minute tensile stress of the raw rubber has always been at the lower limit of the specified index. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a coagulation treatment method for styrene-butadiene rubber latex, which effectively reduces the cost, improves the production efficiency, and increases the tensile stress of the raw rubber.

[0006] The coagulation treatment method of styrene-butadiene rubber latex of the present invention uses polydiallyldimethylammonium chloride (PDADMAC) as a coagulant, a sodium chloride aqueous solution as a coagulation mother liquid, and sulfuric acid as a pH regulator; First, a coagulant is added to the coagulation mother liquor, and then the styrene-butadiene rubber latex is added in multiple times, while the pH value is adjusted with sulfuric acid to maintain acidity.

[0007] Preferably, the present invention comprises the following steps: (1) Preparation of pH adjusting solution: prepare sulfuric acid solution by adding sulfuric acid as pH adjusting agent to obtain pH adjusting solution; (2) Preparation of coagulant solution: dilute polydiallyldimethylammonium chloride with desalted water to obtain a coagulant solution; (3) Preheating of styrene-butadiene rubber latex: Preheat styrene-butadiene rubber latex to 50-55°C; (4) Coagulation of latex: under stirring, add a coagulant solution to the coagulation mother liquor, then add the preheated styrene-butadiene rubber latex in multiple times, and add sulfuric acid solution to control the pH value at 3.0-6.0 until the number of latex particles no longer increases, thus obtaining wet latex particles after coagulation; (5) The wet rubber particles after condensation are sieved and dried to obtain the product styrene-butadiene rubber.

[0008] Preferably, the mass percentage of sulfuric acid in the pH adjustment solution is 1-20%; and the mass percentage of polydiallyldimethylammonium chloride in the coagulant solution is 7-12%.

[0009] Preferably, the mass ratio of the coagulant to the dry rubber in the styrene-butadiene rubber latex is (0.04-0.05):100.

[0010] Preferably, the preparation method of the coagulation mother solution is: dissolving sodium chloride in desalted water, and adjusting the pH value to 3.0-4.0 with sulfuric acid.

[0011] Preferably, the mass ratio of sodium chloride and desalted water in the coagulation mother liquor to the dry rubber in the styrene-butadiene latex is (2-3):200:100.

[0012] Preferably, the temperature of step (4) is 55-65°C.

[0013] Preferably, the stirring speed in step (4) is 640-680 rpm.

[0014] Preferably, the mesh size of the sieving in step (5) is 40-80 meshes.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The coagulation time of the present invention is shorter, which improves the production efficiency. The coagulation time of the present invention is 3 to 5 minutes, while the coagulation time of the traditional coagulant CA is 5 to 10 minutes; 2. The coagulant of the present invention has high efficiency. Under the conditions of the same styrene-butadiene rubber latex treatment amount and the same sulfuric acid solution consumption, the coagulant effect is good. The amount of the coagulant of the present invention is 80% of the amount of the traditional coagulant CA. 3. The present invention reduces the COD in the wastewater discharged from the styrene-butadiene rubber latex coagulation treatment unit; 4. The tensile stress of the product of the present invention is significantly higher than that of the traditional coagulant CA; 5. Since the new coagulant polydiallyldimethylammonium chloride is widely used in the field of water treatment and has a low cost, its unit price is only 10% of the traditional coagulant CA, and the production cost of the present invention is greatly reduced. DETAILED DESCRIPTION

[0016] The technical solution of the present invention will be clearly and completely described below in conjunction with embodiments.

[0017] Unless otherwise specified, all raw materials used in the examples are commercially available.

[0018] Example 1 The coagulation treatment method of styrene-butadiene rubber latex of the present invention uses polydiallyldimethylammonium chloride as a coagulant, a sodium chloride aqueous solution as a coagulation mother liquid, and sulfuric acid as a pH regulator; The steps include: (1) Preparation of pH adjusting solution: Prepare the pH adjusting agent sulfuric acid into a sulfuric acid solution with a mass percentage of 20%, thereby obtaining a pH adjusting solution; (2) Preparation of coagulant solution: dilute polydiallyldimethylammonium chloride with desalted water to a solid content of 10% to obtain a coagulant solution; (3) Preheating of styrene butadiene rubber latex: preheat 500 g of styrene butadiene rubber latex to 52°C; (4) Coagulation of latex: Using a BLENDER HGB550 (volume 2L), at 55°C and a stirring speed of 680rpm, add a coagulant solution to the coagulation mother liquor, then add the preheated styrene-butadiene rubber latex in multiple times, and simultaneously add sulfuric acid solution to control the pH value at 3.0-6.0 until the number of rubber particles no longer increases, thereby obtaining wet rubber particles after coagulation; The preparation method of the coagulation mother solution is as follows: dissolve 2g of sodium chloride in 200g of desalted water, and adjust the pH value to 3.0-4.0 with sulfuric acid.

[0019] (5) The wet rubber particles after condensation are passed through a 40-mesh sieve and dried at 105°C to obtain the product styrene-butadiene rubber.

[0020] Embodiment 2~5 The difference between Examples 2 to 5 and Example 1 is only in the dry rubber content of styrene-butadiene rubber latex and the amount of coagulant used. See Table 1 for details.

[0021] Example 6 The coagulation treatment method of styrene-butadiene rubber latex of the present invention uses polydiallyldimethylammonium chloride as a coagulant, a sodium chloride aqueous solution as a coagulation mother liquid, and sulfuric acid as a pH regulator; The steps include: (1) Preparation of pH adjusting solution: Prepare the pH adjusting agent sulfuric acid into a sulfuric acid solution with a mass percentage of 20%, thereby obtaining a pH adjusting solution; (2) Preparation of coagulant solution: dilute polydiallyldimethylammonium chloride with desalted water to a solid content of 10% to obtain a coagulant solution; (3) Preheating of styrene butadiene rubber latex: preheat 5000 g of styrene butadiene rubber latex to 52°C; (4) Coagulation of latex: using a coagulation machine (volume 50L) at 65°C and a stirring speed of 640rpm, add a coagulant solution to the coagulation mother liquor, then add the preheated styrene-butadiene rubber latex in multiple times, and add sulfuric acid solution to control the pH value at 3.0-6.0 until the number of particles no longer increases, thus obtaining wet particles after coagulation; The preparation method of the coagulation mother solution is as follows: dissolve 20g of sodium chloride in 2000g of desalted water, and adjust the pH value to 3.0-4.0 with sulfuric acid.

[0022] (5) The wet rubber particles after condensation are passed through an 80-mesh sieve and dried at 90°C to obtain the product styrene-butadiene rubber.

[0023] Comparative Example 1 The difference between this comparative example 1 and example 2 is that the coagulant used is a traditional coagulant dinitrile diamine formaldehyde condensate (CA for short), and the amount used is different from that of example 2.

[0024] Performance Testing The performance of the wastewater discharged from the coagulation treatment unit of Examples 1 to 6 and Comparative Example 1 was tested, and the results are shown in Table 1.

[0025] Table 1 Data table of Examples 1 to 6 and Comparative Example 1 The performance of the styrene-butadiene rubber obtained in Example 6 and Comparative Example 1 was tested. The results are shown in Table 2.

[0026] Table 2 Performance test table of Example 6 and Comparative Example 1 In Table 1, by comparing Examples 1 to 6 with Comparative Example 1, it is shown that the coagulation time of the present invention is shorter, and the production efficiency is improved. The coagulation time of the present invention is 3 to 5 minutes, while the coagulation time of the traditional coagulant CA is 5 to 10 minutes; In Table 1, by comparing Example 6 with Comparative Example 1, it can be seen that the present invention reduces the COD in the wastewater discharged from the styrene-butadiene rubber latex coagulation treatment unit. The COD content in the wastewater of the present invention is 696.38 mg / L, while when the traditional coagulant CA is used, the COD content in the wastewater is 1266.48 mg / L; the COD content in the wastewater of the present invention is significantly reduced; The coagulant of the present invention has high efficiency and maintains good coagulation effect under the same styrene-butadiene rubber latex processing amount. The coagulant consumption of the present invention is small, and the amount of the coagulant of the present invention is 80% of the amount of the traditional coagulant CA.

[0027] In Table 2, by comparing Example 6 and Comparative Example 1, it can be seen that the 35-min tensile stress of the styrene-butadiene rubber product of the present invention is 19.5 MPa, and the 35-min tensile stress of the raw rubber of the same styrene-butadiene rubber latex coagulated with the traditional coagulant CA is 19.1 MPa; the tensile stress of the product of the present invention is significantly improved compared with the traditional coagulant CA.

Claims

1. A coagulation treatment method for styrene-butadiene rubber latex, characterized in that: Polydiallyldimethylammonium chloride is used as a coagulant, sodium chloride aqueous solution is used as a coagulant mother solution, and sulfuric acid is used as a pH regulator; First, a coagulant is added to the coagulation mother liquor, and then the styrene-butadiene rubber latex is added in multiple times, while the pH value is adjusted with sulfuric acid to maintain acidity.

2. The coagulation treatment method of styrene-butadiene rubber latex according to claim 1, characterized in that: The steps include: (1) Preparation of pH adjusting solution: prepare sulfuric acid solution by adding sulfuric acid as pH adjusting agent to obtain pH adjusting solution; (2) Preparation of coagulant solution: dilute polydiallyldimethylammonium chloride with desalted water to obtain a coagulant solution; (3) Preheating of styrene-butadiene rubber latex: Preheat styrene-butadiene rubber latex to 50-55°C; (4) Coagulation of latex: under stirring, add a coagulant solution to the coagulation mother liquor, then add the preheated styrene-butadiene rubber latex in multiple times, and add sulfuric acid solution to control the pH value at 3.0-6.0 until the number of latex particles no longer increases, thus obtaining wet latex particles after coagulation; (5) The wet rubber particles after condensation are sieved and dried to obtain the product styrene-butadiene rubber.

3. The coagulation treatment method of styrene-butadiene rubber latex according to claim 2, characterized in that: The mass percentage of sulfuric acid in the pH adjustment solution is 1-20%; the mass percentage of polydiallyldimethylammonium chloride in the coagulant solution is 7-12%.

4. The coagulation treatment method of styrene-butadiene rubber latex according to claim 1, characterized in that: The mass ratio of the coagulant to the dry rubber in the styrene-butadiene rubber latex is (0.04~0.05):

100.

5. The coagulation treatment method of styrene-butadiene rubber latex according to claim 1, characterized in that: The preparation method of the coagulation mother liquor is as follows: dissolve sodium chloride in desalted water and adjust the pH value to 3.0-4.0 with sulfuric acid.

6. The coagulation treatment method of styrene-butadiene rubber latex according to claim 5, characterized in that: The mass ratio of sodium chloride and desalted water in the coagulation mother liquor to the dry rubber in the styrene-butadiene latex is (2~3):200:

100.

7. The coagulation treatment method of styrene-butadiene rubber latex according to claim 2, characterized in that: The temperature of step (4) is 55-65°C.

8. The coagulation treatment method of styrene-butadiene rubber latex according to claim 2, characterized in that: The stirring speed of step (4) is 640-680 rpm.

9. The coagulation treatment method of styrene-butadiene rubber latex according to claim 2, characterized in that: The mesh size of the sieve in step (5) is 40 to 80 meshes.

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