A method for preparing white carbon black for rubber compound

Abstract

The invention develops a method for preparing white carbon black for rubber compound, wherein the fumed silica modified by acid hydrolysis of a silane coupling agent in a nucleating liquid is used as a core, and precipitated silica is coated in a water glass solution to form a composite white carbon black, and acrylic acid is used as a catalyst for acid hydrolysis of the silane coupling agent and a cross-linking agent in the subsequent rubber compound, thereby effectively improving the tensile strength and elongation at break of the rubber compound.

Description

Technical Field

[0001] The invention relates to a production process of white carbon black, in particular to a method for preparing white carbon black for rubber compounding. Background Art

[0002] As a commonly used functional additive, silica is widely used in many fields. In the field of silicone rubber, silica is mainly used as a filler, thickener, reinforcing agent, etc.

[0003] In the prior art, the application of silica in the silicone rubber field has the following problems: 1. The compatibility of silica with the silicone rubber system needs to be improved to enhance the dispersibility and stability of silica in the silicone rubber system; 2. Silica is added to silicone rubber as a reinforcing additive to ensure the hardness and tensile properties of the rubber mix, but as the amount added increases, the processing performance of the rubber mix decreases, and the time required to achieve uniform mixing is long, which restricts production efficiency; the density of the rubber mix increases, and at the same time, the rebound after stretching produces permanent deformation, which is very likely to occur in a low-temperature environment. Summary of the Invention

[0004] The present invention develops a method for preparing white carbon black for rubber mixes. The method uses fumed silica modified by acid hydrolysis with a silane coupling agent in a nucleating liquid as a core, and coats the core with precipitated silica in a water glass solution to form a composite white carbon black. Acrylic acid is used as a catalyst for the acid hydrolysis of the silane coupling agent and a crosslinking agent in the subsequent rubber mix, thereby effectively improving the tensile strength and elongation at break of the rubber mix.

[0005] A method for preparing white carbon black for rubber compounding, the preparation method being as follows:

[0006] 1. Preparation of Nucleation Solution A

[0007] (1) Dispersing fumed silica in water 5-8 times its mass, introducing ammonia to adjust the pH to 8.5-9.0, heating to 50-60°C, refluxing until most of the ammonia evaporates, cooling to room temperature, and reducing the pH to 7.2-7.5;

[0008] (2) then dropwise adding a silane coupling agent at a concentration of 10% to 15% by weight of the fumed silica, stirring evenly, and simultaneously adding an emulsifier at a concentration of 0.5% to 1.0% by weight of the fumed silica and acrylic acid at a concentration of 8% to 10% by weight of the fumed silica, and homogenizing and emulsifying at high speed to prepare an acidic nucleating solution A;

[0009] 2. Preparation of composite silica

[0010] (3) dissolving water glass in water at 50°C-55°C to prepare 1.25-1.28 g / mL water glass solution B;

[0011] (4) After dissolution is complete, dilute sulfuric acid is added dropwise to the water glass solution B until the pH reaches 5.0-5.5;

[0012] (5) adding nucleating solution A to water glass solution B in a volume ratio of 3-5:1, stirring continuously for 40-60 minutes, then allowing to stand for 20-30 minutes, filtering after settling, and washing with purified water to obtain wet material C;

[0013] (6) Dissolve the curing accelerator in 30-50 times the mass of ethanol, then add wet material C with a mass of 2-3 times the mass of ethanol, mix well and dry under reduced pressure to obtain composite white carbon black.

[0014] Furthermore, the particle size of the fumed silica is 7-15 nm.

[0015] Furthermore, the silane coupling agent is one or more of KH550, KH560, and KH570.

[0016] Furthermore, the emulsifier is one or more of OP-4, OP-7, and OP-10.

[0017] Furthermore, the modulus of the water glass is 3.1-3.3.

[0018] Furthermore, the dilute sulfuric acid is sulfuric acid with a mass fraction of 1%.

[0019] Furthermore, the curing accelerator is one or both of 2-methylimidazole and 2-phenylimidazole.

[0020] Furthermore, the particle size of the composite silica is 30-40 nm.

[0021] Advantages of the present invention:

[0022] 1. The present invention uses fumed silica modified by acidification and hydrolysis of a silane coupling agent in a nucleating liquid as a core, and coats it with precipitated silica in a water glass solution to form a composite white carbon black;

[0023] 2. The present invention uses acrylic acid as a silane coupling agent acidification hydrolysis catalyst and a crosslinking agent in the subsequent rubber mix, which can effectively improve the tensile strength and elongation at break of the rubber mix;

[0024] 3. On the basis of ensuring the tensile strength and elongation of the rubber mix, the amount of compounded silica in the raw rubber can be reduced by about 50%. After reducing the amount of compounded silica, the resilience of the rubber mix can be fully guaranteed and can be used at lower temperatures. Compounded silica can greatly improve the processing performance and dispersibility of the rubber mix, and also greatly improve the performance of the rubber mix products.

[0025] 4. Adding a curing accelerator to the composite silica in an ethanol system is beneficial to the subsequent cross-linking in the rubber mix. At the same time, it can remove moisture from the composite silica, avoiding the disadvantage that precipitated silica is not suitable for the rubber mix (water easily forms bubbles). DETAILED DESCRIPTION

[0026] Example 1

[0027] A method for preparing white carbon black for rubber compounding, the preparation method being as follows:

[0028] 1. Preparation of Nucleation Solution A

[0029] (1) Disperse fumed silica with a particle size of 7 nm in water at a mass multiple of 8 times, introduce ammonia gas to adjust the pH to 8.5, heat to 50°C, reflux until most of the ammonia gas evaporates, cool to room temperature, and reduce the pH to 7.2;

[0030] (2) Then, 15% of the mass of the fumed silica was added dropwise to the silane coupling agent KH550, and after stirring evenly, 1.0% of the mass of the fumed silica was added to the emulsifier OP-4 and 10% of the mass of the fumed silica was added to the mixture, and high-speed homogenization and emulsification were performed to prepare an acidic nucleating solution A;

[0031] 2. Preparation of composite silica

[0032] (3) Dissolve water glass with a modulus of 3.3 in 55°C water to prepare 1.28 g / mL water glass solution B;

[0033] (4) After dissolution is complete, add 1% by mass of dilute sulfuric acid to the water glass solution B until the pH reaches 5.5;

[0034] (5) adding nucleating solution A to water glass solution B in a volume ratio of 3:1, stirring continuously for 40 min, then allowing to stand for 30 min, filtering after settling, and washing with purified water to obtain wet material C;

[0035] (6) Dissolve the curing accelerator 2-methylimidazole in 30 times the mass of ethanol, then add wet material C with 3 times the mass of ethanol, mix well and dry under reduced pressure to obtain composite silica with a particle size of 40 nm.

[0036] Example 2

[0037] A method for preparing white carbon black for rubber compounding, the preparation method being as follows:

[0038] 1. Preparation of Nucleation Solution A

[0039] (1) Disperse 10 nm fumed silica in 6 times the mass of water, introduce ammonia to adjust the pH to 8.9, heat to 58°C, reflux until most of the ammonia evaporates, cool to room temperature, and reduce the pH to 7.3;

[0040] (2) Then, 12% by weight of the fumed silica was added dropwise to the silane coupling agent KH560, and after stirring evenly, 0.8% by weight of the fumed silica was added to the emulsifier OP-7 and 9% by weight of the fumed silica was added to the mixture, and high-speed homogenization and emulsification were performed to prepare an acidic nucleating solution A;

[0041] 2. Preparation of composite silica

[0042] (3) Dissolve water glass with a modulus of 3.3 in 55°C water to prepare 1.28 g / mL water glass solution B;

[0043] (4) After dissolution is complete, add 1% by mass of dilute sulfuric acid to the water glass solution B until the pH reaches 5.5;

[0044] (5) adding nucleating solution A to water glass solution B in a volume ratio of 4:1, stirring continuously for 45 minutes, then allowing to stand for 22 minutes, filtering after settling, and washing with purified water to obtain wet material C;

[0045] (6) Dissolve the curing accelerator 2-methylimidazole in 40 times the mass of ethanol, then add wet material C with 2.5 times the mass of ethanol, mix well and dry under reduced pressure to obtain composite silica with a particle size of 40 nm.

[0046] Example 3

[0047] A method for preparing white carbon black for rubber compounding, the preparation method being as follows:

[0048] 1. Preparation of Nucleation Solution A

[0049] (1) Disperse fumed silica with a particle size of 15 nm in water with a mass multiple of 5 times, introduce ammonia gas to adjust the pH to 9.0, heat to 60°C, reflux until most of the ammonia gas evaporates, cool to room temperature, and reduce the pH to 7.5;

[0050] (2) Then, 10% by weight of the fumed silica was added dropwise to the silane coupling agent KH570, and after stirring evenly, 0.5% by weight of the fumed silica was added to the emulsifier OP-10 and 8% by weight of the fumed silica was added to the mixture, and high-speed homogenization and emulsification were performed to prepare an acidic nucleating solution A;

[0051] 2. Preparation of composite silica

[0052] (3) Dissolve water glass with a modulus of 3.3 in 50°C water to prepare 1.25 g / mL water glass solution B;

[0053] (4) After dissolution is complete, add 1% by mass of dilute sulfuric acid to the water glass solution B until the pH reaches 5.0;

[0054] (5) adding nucleating solution A to water glass solution B in a volume ratio of 5:1, stirring continuously for 60 min, then allowing to stand for 20 min, filtering after settling, and washing with purified water to obtain wet material C;

[0055] (6) Dissolve the curing accelerator 2-phenylimidazole in 50 times the mass of ethanol, then add wet material C with a mass of 2 times that of ethanol, mix well and dry under reduced pressure to obtain composite white carbon black with a particle size of 40 nm.

[0056] Comparative Example 1

[0057] Fumed silica with a particle size of 40 nm was used for comparison.

[0058] Comparative Example 2

[0059] Equivalent amounts of fumed silica with a particle size of 40 nm, silane coupling agent KH560, emulsifier OP-7, acrylic acid, curing accelerator 2-methylimidazole, and water as in Example 2 were mixed and emulsified, and then an equal amount of 1% by mass dilute sulfuric acid was added, followed by freeze-drying to obtain modified fumed silica.

[0060] Comparative Example 3

[0061] A method for preparing white carbon black for rubber compounding, wherein the step (1) of activating fumed silica with an alkaline solution is omitted, and the rest of the steps are the same as those in Example 2.

[0062] Comparative Example 4

[0063] A method for preparing white carbon black for rubber compounding, wherein in step (2) of the preparation method, no silane coupling agent KH560 is added, and the rest is the same as in Example 2.

[0064] Comparative Example 5

[0065] A method for preparing white carbon black for rubber compounding, wherein no emulsifier OP-7 is added in step (2) of the preparation method, and the rest is the same as in Example 2.

[0066] Comparative Example 6

[0067] A method for preparing white carbon black for rubber compounding, wherein in step (2) of the preparation method, acrylic acid is replaced by an equal amount of dilute sulfuric acid with a mass fraction of 1%, and the rest is the same as in Example 2.

[0068] Comparative Example 7

[0069] A method for preparing white carbon black for rubber compounding, wherein no curing accelerator 2-methylimidazole is added in step (6) of the preparation method.

[0070] Comparative Example 8

[0071] A method for preparing white carbon black for rubber compounding, wherein in step (6) of the preparation method, a curing accelerator 2-methylimidazole is dissolved in water and freeze-dried to obtain composite white carbon black.

[0072] Detection and analysis:

[0073] Composite silica was prepared in a 50 L pilot reactor according to the preparation method of each embodiment and comparative example. The ingredients were prepared according to the ratio of 100 parts of methyl vinyl silicone rubber, 50 parts of composite silica, 8 parts of diphenylsilanediol, and 5 parts of vinyl hydroxy silicone oil prepared in each embodiment and comparative example, and mixed. The mixing conditions were unified at 180° C. and the treatment was 150 min.

[0074] 1. The Shore A hardness of the rubber mix was tested according to the test method of GB / T531-1999, and the tensile strength (MPa) and elongation at break (%) of the rubber mix were tested according to the test method of GB / T528-2009. The results are shown in Table 1.

[0075] 2. The mass fraction of the composite silica prepared in Example 2 in the rubber mix was reduced to 30 parts, and then compared with the rubber mix of Comparative Example 1. The results are shown in Table 2.

[0076] Table 1

[0077] Rubber compound Shore A hardness Tensile strength (MPa) Elongation at break (%) Example 1 52 11.8 553 Example 2 (50 parts of composite white carbon black) 52 12.1 562 Example 3 50 11.3 552 Comparative Example 1 46 9.0 505 Comparative Example 2 47 9.1 509 Comparative Example 3 50 11.1 540 Comparative Example 4 50 10.5 533 Comparative Example 5 49 10.3 516 Comparative Example 6 46 9.1 501 Comparative Example 7 48 9.9 521 Comparative Example 8 52 11.9 554

[0078] In Comparative Example 4, no silane coupling agent was added for surface modification, resulting in a long mixing time of 280 minutes. In Comparative Example 5, no emulsifier was added, resulting in difficulty in controlling the particle size of the obtained composite silica. The compound rubber obtained in Comparative Example 8 had a small amount of fine pores.

[0079] Table 2

[0080] Rubber compound Shore A hardness Tensile strength (MPa) Elongation at break (%) Example 2 (30 parts of composite white carbon black) 45 9.4 595 Comparative Example 1 46 9.0 505

[0081] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing white carbon black for rubber compound, characterized in that: The preparation method is as follows:

1. Preparation of Nucleation Solution A (1) dispersing fumed silica in water with a mass multiple of 5-8 times, introducing ammonia to adjust the pH to 8.5-9.0, heating to 50-60° C., refluxing until most of the ammonia is volatilized, cooling to room temperature, and reducing the pH to 7.2-7.5; (2) then dropwise adding 10% to 15% of the mass of the fumed silica in the form of a silane coupling agent, stirring evenly, and simultaneously adding 0.5% to 1.0% of the mass of the fumed silica in the form of an emulsifier and 8% to 10% of the mass of the fumed silica in the form of acrylic acid, and high-speed homogenization and emulsification to obtain an acidic nucleation liquid A; 2. Preparation of composite white carbon black (3) dissolving water glass in water at 50° C. to 55° C. to prepare 1.25-1.28 g / mL water glass solution B; (4) After the dissolution is completed, dilute sulfuric acid is added dropwise to the water glass solution B until the pH is 5.0-5.5; (5) adding nucleating liquid A to water glass solution B in a volume ratio of 3-5:1, stirring continuously for 40-60 min, then standing and aging for 20-30 min, filtering after sedimentation, and washing with purified water to obtain wet material C; (6) Dissolve the curing accelerator in 30-50 times the mass of ethanol, then add wet material C in an amount of 2-3 times the mass of ethanol, mix well, and dry under reduced pressure to obtain composite white carbon black.

2. The method for preparing white carbon black for rubber compound according to claim 1, characterized in that: The particle size of the fumed silica is 7-15 nm.

3. The method for preparing white carbon black for rubber compound according to claim 1, characterized in that: The silane coupling agent is one or more of KH550, KH560 and KH570.

4. The method for preparing white carbon black for rubber compound according to claim 1, characterized in that: The emulsifier is one or more of OP-4, OP-7 and OP-10.

5. The method for preparing white carbon black for rubber compound according to claim 1, characterized in that: The modulus of the water glass is 3.1-3.

3.

6. The method for preparing white carbon black for rubber compound according to claim 1, characterized in that: The dilute sulfuric acid is 1% by mass sulfuric acid.

7. The method for preparing white carbon black for rubber compound according to claim 1, characterized in that: The curing accelerator is one or both of 2-methylimidazole and 2-phenylimidazole.

8. The method for preparing white carbon black for rubber compound according to any one of claims 1 to 7, characterized in that: The particle size of the composite white carbon black is 30-40 nm.