A white carbon black wet glue and a preparation method thereof, and a vulcanized rubber

Abstract

The application belongs to the technical field of natural rubber and rubber products, and particularly relates to a white carbon black wet rubber, a preparation method thereof and a vulcanized rubber. The white carbon black, a phospholipid emulsion and a coagulase are mixed to obtain a white carbon black emulsion; the white carbon black emulsion and a natural rubber latex are mixed to obtain a paste; and the paste is sequentially subjected to standing coagulation and drying to obtain the white carbon black wet rubber. The preparation method provided by the application uses phospholipid as a dispersing agent, and simultaneously uses coagulase as a coagulant, so that the mechanical properties of the vulcanized rubber are improved, and the natural rubber latex does not need to be pre-emulsified, so that the production efficiency of the white carbon black wet rubber is improved and the cost is reduced.

Description

Technical Field

[0001] This invention belongs to the technical field of natural rubber and rubber products, specifically relating to a wet-process precipitated silica rubber and its preparation method, as well as a vulcanized rubber. Background Technology

[0002] In the rubber industry, silica is a common reinforcing agent, with a reinforcing effect exceeding that of any other white reinforcing agent. It imparts high tensile strength, stress at a given elongation, tear strength, and heat resistance to rubber compounds. The traditional dry mixing process for silica involves adding pretreated silica to a mixing plant and mixing it with rubber components under mechanical shear and agitation forces. The mixing is achieved by controlling process parameters such as temperature, time, and rotation speed. This process is energy-intensive and generates significant dust pollution. Furthermore, the dispersibility of silica is greatly limited by the process parameters, affecting the properties of the rubber compound.

[0003] Compared to traditional dry mixing processes, wet mixing offers significant advantages in terms of environmental friendliness, energy consumption, dispersion effect, production efficiency, and quality stability. However, existing wet-process rubbers made with silica require pre-emulsification of natural rubber latex, and silica still suffers from uneven dispersion, which affects the mechanical properties of the final vulcanized rubber. Summary of the Invention

[0004] The purpose of this invention is to provide a wet-process silica rubber, its preparation method, and a vulcanized rubber. The preparation method provided by this invention omits the pre-emulsification step of natural rubber latex, which can improve production efficiency; at the same time, the obtained vulcanized rubber has excellent mechanical properties and has industrial application value.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing wet-process silica adhesive, comprising the following steps:

[0007] A silica emulsion is obtained by mixing silica, phospholipid emulsion and coagulating enzyme.

[0008] The silica emulsion and natural rubber latex are mixed to obtain a paste;

[0009] The paste was subjected to static solidification and drying in sequence to obtain the wet-process silica adhesive.

[0010] Preferably, the silica includes one or more of fumed silica, hydrophilic silica, and oleophilic silica.

[0011] Preferably, the method for preparing the oleophilic silica includes the following steps:

[0012] Hydrophobic modification of fumed silica using a silane coupling agent yields oleophilic silica; the silane coupling agent accounts for 10-20% of the mass percentage of the fumed silica.

[0013] Preferably, the phospholipid emulsion comprises phospholipids and water, wherein the phospholipids include one or more of lecithin, phosphatidylethanolamine, and phosphatidylserine.

[0014] Preferably, the phospholipids in the phospholipid emulsion account for 1-5% of the mass percentage of the silica.

[0015] Preferably, the mass ratio of the dry rubber in the silica to the natural rubber latex is 1:2 to 3.

[0016] Preferably, the coagulating enzyme is a protease; the coagulating enzyme accounts for 0.1% to 1% of the dry rubber mass in the natural rubber latex.

[0017] Preferably, the settling time is 8 to 24 hours; the drying temperature is 100 to 120°C.

[0018] The present invention provides a wet-process silica adhesive prepared by the preparation method described in the above technical solution.

[0019] This invention provides a vulcanizate comprising the following raw materials in parts by weight:

[0020] The above technical solution contains 150-180 parts of wet-process silica, 3-5 parts of zinc oxide, 1-2 parts of stearic acid, 1-2 parts of antioxidant, 2-6 parts of coupling agent, 2-3 parts of accelerator, and 1-2 parts of sulfur.

[0021] This invention provides a method for preparing wet-process silica rubber, comprising the following steps: mixing silica, phospholipid emulsion, and coagulating enzyme to obtain a silica emulsion; mixing the silica emulsion with natural rubber latex to obtain a paste; and subjecting the paste to static coagulation and drying sequentially to obtain the silica wet-process rubber. This invention utilizes amphiphilic phospholipids in the phospholipid emulsion as a dispersant for silica, effectively improving the dispersion of silica in natural rubber, thereby enhancing the mechanical properties of the vulcanized rubber. Simultaneously, the phospholipids in the phospholipid emulsion also act as plasticizers, improving the processing performance of the resulting silica wet-process rubber (including mixing, calendering, and other processing operations). Furthermore, this invention introduces a coagulating enzyme with a longer coagulation time as a coagulant, thereby ensuring sufficient dispersion time of silica in natural rubber latex. Simultaneously, the dispersing effect of phospholipids ensures uniform dispersion of silica in the natural rubber latex. After rubber coagulation, the silica can fully encapsulate within the rubber molecules, not only improving the mechanical properties of vulcanizates obtained from silica wet-process rubber as raw rubber but also effectively reducing the processing loss rate of silica. In summary, the preparation method provided by this invention uses phospholipids as a dispersant and assists with coagulating enzymes as a coagulant, improving the mechanical properties of vulcanizates while eliminating the need for pre-emulsification of natural rubber latex, thus increasing the production efficiency of silica wet-process rubber and reducing costs. The results of the examples show that the vulcanizate prepared using the silica wet process rubber provided by the present invention has excellent comprehensive properties. The tested vulcanizate has a tensile strength of 28-32 MPa, a 300% constant elongation stress of 18-21 MPa, an ash content of 29-33%, a silica dispersion of 8-9, and a heat generation of 26-29°C. Detailed Implementation

[0022] This invention provides a method for preparing wet-process silica adhesive, comprising the following steps:

[0023] A silica emulsion is obtained by mixing silica, phospholipid emulsion and coagulating enzyme.

[0024] The silica emulsion and natural rubber latex are mixed to obtain a paste;

[0025] The paste was subjected to static solidification and drying in sequence to obtain the wet-process silica adhesive.

[0026] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0027] This invention involves mixing silica, phospholipid emulsion, and coagulating enzyme to obtain a silica emulsion. In this invention, the silica preferably comprises one or more of fumed silica, hydrophilic silica, and oleophilic silica. The hydrophilic silica is preferably REOLOSIL QS-102 type hydrophilic silica, purchased from Tokuyama Corporation. The preparation method of the oleophilic silica preferably includes the following steps: hydrophobically modifying fumed silica with a silane coupling agent to obtain oleophilic silica. The silane coupling agent is preferably KH-560. The mass percentage of the silane coupling agent in the fumed silica is preferably 10-20%, more preferably 10%. The hydrophobic modification preferably includes the following steps: dispersing the fumed silica in a silane coupling agent solution to perform the hydrophobic modification. The silane coupling agent solution preferably comprises a silane coupling agent, ethanol, and water. The mass percentage of the silane coupling agent in the solution is preferably 5-15%, more preferably 10%. The mass ratio of ethanol to water is preferably 8-9:1, more preferably 8:1. The hydrophobic modification temperature is preferably 50-60°C, and the time is preferably 6-8 hours. After the hydrophobic modification is completed, a modified solution is obtained. Preferably, the modified solution is subjected to solid-liquid separation, washing, and drying sequentially to obtain the oleophilic silica. The washing is preferably performed using alternating water and ethanol. The drying temperature is preferably 45-50°C.

[0028] In this invention, the phospholipid emulsion comprises phospholipids and water. The phospholipids preferably include one or more of lecithin, phosphatidylethanolamine, and phosphatidylserine, more preferably lecithin. This invention does not have specific requirements regarding the amount of water in the phospholipid emulsion. The phospholipids in the phospholipid emulsion preferably constitute 1-5% of the mass of the silica, and in the examples, this can be 2% or 4%. This invention uses phospholipids (preferably lecithin) as a dispersant for silica and simultaneously as a plasticizer for natural rubber. Compared to using surfactants (such as sodium dodecyl sulfonate or Triton), this invention uses phospholipids as a dispersant for silica, which does not adversely affect the coagulation of the natural rubber latex. Furthermore, by controlling the mass ratio of phospholipids to silica, this invention can obtain vulcanizates with excellent mechanical properties.

[0029] In this invention, the coagulating enzyme is preferably a protease, more preferably papain and / or bromelain. The coagulating enzyme's mass percentage in the dry rubber of the natural rubber latex is preferably 0.1% to 1%, and in the examples, it can be 0.1%. By controlling the mass ratio of the coagulating enzyme to the dry rubber in the natural rubber latex, this invention enables the natural rubber latex to have a suitable coagulation time, thereby ensuring that the silica is fully dispersed in the natural rubber latex. After the latex coagulates, it is fully encapsulated within the rubber molecules, resulting in a high-performance wet-process silica latex.

[0030] The present invention does not have special requirements for the specific implementation of the mixing of the silica, phospholipid emulsion and coagulating enzyme; simply stirring and mixing until uniform is achieved is sufficient.

[0031] After obtaining the silica emulsion, this invention mixes the silica emulsion with natural rubber latex to obtain a paste. In this invention, the mass ratio of dry silica to natural rubber latex is 1:2 to 3, and in the examples, it can be 1:2. This invention does not have special requirements for the specific implementation method of mixing the silica emulsion and natural rubber latex; stirring and mixing until a thick paste is reached is sufficient.

[0032] After obtaining the paste, the present invention sequentially subjects the paste to static solidification and drying to obtain the wet-process silica adhesive. In the present invention, the static solidification is carried out in a stainless steel tray at room temperature, and the static solidification time is preferably 8–24 hours. In the embodiments, it can be 12 hours. The drying temperature is preferably 100–120°C.

[0033] The present invention provides a wet-process silica adhesive prepared by the preparation method described in the above technical solution.

[0034] This invention provides a vulcanizate comprising the following raw materials in parts by weight:

[0035] The above technical solution contains 150-180 parts of wet-process silica, 3-5 parts of zinc oxide, 1-2 parts of stearic acid, 1-2 parts of antioxidant, 2-6 parts of coupling agent, 2-3 parts of accelerator, and 1-2 parts of sulfur.

[0036] The raw materials for preparing the vulcanizate provided by the present invention include 150-180 parts of the wet-process silica rubber described in the above technical solution, and in the examples, it can be 150 parts.

[0037] Based on the number of batches of the wet-process precipitated silica rubber, the raw materials for preparing the vulcanized rubber provided by the present invention include 3 to 5 parts of zinc oxide, and in the examples, it can be 5 parts.

[0038] Based on the number of batches of the wet-process precipitated silica rubber, the raw materials for preparing the vulcanized rubber provided by the present invention include 1 to 2 parts of stearic acid, which may be 1.5 parts in the examples.

[0039] Based on the production batch number of the wet-process precipitated silica rubber, the raw materials for preparing the vulcanizate provided by this invention include 1-2 parts of antioxidant, which may be 1.5 parts in the examples. In this invention, the antioxidant is preferably antioxidant 4010NA.

[0040] Based on the production batch number of the wet-process precipitated silica rubber, the raw materials for preparing the vulcanizate provided by this invention include 2 to 6 parts of coupling agent, and in the examples, it can be 5 parts. In this invention, the coupling agent is preferably KH-845-4.

[0041] Based on the production batch number of the wet-process precipitated silica rubber, the raw materials for preparing the vulcanizate provided by the present invention include 2 to 3 parts of accelerator, and in the examples, it can be 3 parts. In the present invention, the accelerator preferably includes accelerator CZ and accelerator D, and the mass ratio of accelerator CZ to accelerator D is preferably 2:1.

[0042] Based on the production batch of the wet-process precipitated silica rubber, the raw materials for preparing the vulcanized rubber provided by the present invention include 1 to 2 parts of sulfur, which may be 1.5 parts in the examples.

[0043] The vulcanizate provided by this invention uses the wet-process precipitate of silica described in the above technical solution as the raw rubber to prepare a compound, and the resulting vulcanizate has excellent mechanical properties.

[0044] The vulcanizate provided by this invention has a tensile strength of 28-32 MPa, a 300% constant tensile stress of 18-21 MPa, an ash content of 29-33%, a silica dispersion of 8-9, and a heat generation of 26-29°C.

[0045] In this invention, the method for preparing the vulcanizate preferably includes the following steps:

[0046] The wet-process precipitate of silica, coupling agent, zinc oxide, stearic acid, antioxidant, sulfur and accelerator are mixed to obtain the compounded rubber.

[0047] The compounded rubber is vulcanized to obtain the vulcanized rubber.

[0048] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0049] Example 1

[0050] 100g of silane coupling agent KH-560 was prepared into a KH-560 solution, which was prepared by mixing 10% silane coupling agent KH-560, 80% ethanol, and 10% water by mass. 550g of fumed silica (Shandong Aochuang Chemical Co., Ltd.) was dispersed in the KH-560 solution and stirred at 60℃ for 8 hours. After filtration, the silica was washed alternately with water and ethanol, and finally dried at 50℃ to obtain oleophilic fumed silica.

[0051] 10g of lecithin was dispersed in water by high-speed stirring to obtain a lecithin emulsion. 500g of lipophilic silica was added to the lecithin emulsion, and 1g of coagulating enzyme (papain) was added and stirred thoroughly to obtain an lipophilic silica emulsion.

[0052] The oleophilic silica emulsion was mixed with natural rubber latex containing 1000g of dry rubber and stirred thoroughly until it became a viscous paste. The mixture was then transferred to a stainless steel tray and allowed to stand and solidify for 12 hours. Finally, it was dried at 120°C to obtain the silica wet-process rubber.

[0053] Example 2

[0054] 10g of lecithin was dispersed in water by high-speed stirring to obtain a lecithin emulsion. 500g of hydrophilic silica (REOLOSIL QS-102 type, purchased from Tokuyama) was added to the lecithin emulsion, and 1g of coagulating enzyme (papain) was added and stirred thoroughly to obtain a hydrophilic silica emulsion.

[0055] The hydrophilic silica emulsion was mixed with natural rubber latex containing 1000g of dry rubber and stirred thoroughly until it became a thick paste. The mixture was then transferred to a stainless steel tray and allowed to stand and solidify for 12 hours. Finally, it was dried at 120°C to obtain the silica wet-process rubber.

[0056] Example 3

[0057] 20g of lecithin was dispersed in water by high-speed stirring to obtain a lecithin emulsion. 500g of hydrophilic silica (REOLOSIL QS-102 type, purchased from Tokuyama) was added to the lecithin emulsion and 1g of coagulating enzyme (papain) was added and stirred thoroughly to obtain a hydrophilic silica emulsion.

[0058] The hydrophilic silica emulsion was mixed with natural rubber latex containing 1000g of dry rubber and stirred thoroughly until it became a thick paste. The mixture was then transferred to a stainless steel tray and allowed to stand and solidify for 12 hours. Finally, it was dried at 120°C to obtain the silica wet-process rubber.

[0059] Comparative Example 1

[0060] 1g of coagulating enzyme (papain) was mixed with natural rubber latex containing 1000g of dry rubber, coagulated for 12 hours, and dried at 120℃ to obtain natural rubber.

[0061] Comparative Example 2

[0062] The commercially available silica wet-process rubber SF175-50 (manufacturer: Mengla County Manzhuang Rubber Co., Ltd.) was used for comparison.

[0063] Test case

[0064] Vulcanizates were prepared using the silica wet-process rubber prepared in Examples 1-3, the natural rubber prepared in Comparative Example 1, the commercially available silica wet-process rubber SF175-50 in Comparative Example 2, and the silica wet-process rubber prepared in Comparative Example 3.

[0065] The raw materials for preparing the vulcanizate compound are shown in Table 1 (the fumed silica used in the vulcanizate formulation of Comparative Example 1 was purchased from Shandong Aochuang Chemical Co., Ltd.). The vulcanization conditions for the vulcanizate were 145℃ × 30 min. The performance test results of the vulcanizates prepared from the fumed silica wet-process rubbers prepared in Examples 1-3 and the natural rubber prepared in Comparative Example 1 are shown in Table 2. In Table 2: the ash sample is the fumed silica wet-process rubber masterbatch, the sample with the optimal vulcanization time is the fumed silica wet-process rubber compound, and the samples for other items are fumed silica wet-process rubber vulcanizates.

[0066] Table 1. Compound formulations for Examples 1-3 and Comparative Examples 1-3

[0067] precipitated silica wet-process adhesive 0 150 150 150 150 150 natural rubber 100 0 0 0 0 0 Fumed silica 50 0 0 0 0 0 Zinc oxide 5 5 5 5 5 5 stearic acid 1.5 1.5 1.5 1.5 1.5 1.5 Anti-aging agent 4010NA 1.5 1.5 1.5 1.5 1.5 1.5 Coupling agent KH-845-4 5.0 5.0 5.0 5.0 5.0 5.0 Accelerator CZ 2.0 2.0 2.0 2.0 2.0 2.0 Accelerator D 1.0 1.0 1.0 1.0 1.0 1.0 sulfur 1.5 1.5 1.5 1.5 1.5 1.5

[0068] The specific steps of mixing the vulcanizates on the open mill in Examples 1-3 and Comparative Examples 2-3 are shown in Table 2:

[0069] Table 2 shows the specific steps of mixing on the open mill during the preparation of vulcanizates in Examples 1-3 and Comparative Examples 2-3.

[0070]

[0071]

[0072] The method for preparing the compounded rubber of the natural rubber prepared in Comparative Example 1 according to the compounded rubber formulation in Table 1 specifically includes: First, the natural rubber prepared in Comparative Example 1 is mixed with fumed silica in an internal mixer according to the method in Table 3, and then the mixing is started directly from step 2 of the open mill mixing in Table 2.

[0073] Table 3 shows the steps of preparing natural rubber in Comparative Example 1 by first mixing it with fumed silica in a mixer.

[0074]

[0075] The performance test results of the vulcanizates prepared from commercially available silica wet-process rubber SF175-50 (manufacturer: Mengla County Manzhuang Rubber Co., Ltd.) in Examples 1-3, Comparative Examples 1 and 2, and Comparative Example 3 are shown in Table 4. The silica dispersion was tested using a silica dispersion meter.

[0076] Table 4 Test Results

[0077]

[0078]

[0079] The test standards for each test item in Table 4 are shown in Table 5.

[0080] Table 5 Test Standards

[0081] Optimal vulcanization time, min GB / T9869-2014 Hardness, degree GB / T531.1-2008 300% constant tensile stress, MPa GB / T528-2009 Tensile strength, MPa GB / T528-2009 Elongation at break, % GB / T528-2009 Tear strength, kN / m GB / T529-2008 Compression fatigue heat generation, ℃ GB / T1687.3-2014 Ash content, % GB / T4498

[0082] Comparative Example 3

[0083] 10g of phosphatidylethanolamine was dispersed in water at high speed to obtain a lecithin emulsion. 500g of hydrophilic silica (REOLOSIL QS-102 type, purchased from Tokuyama) was added to the lecithin emulsion and 1g of coagulating enzyme (papain) was added and stirred thoroughly to obtain a hydrophilic silica emulsion.

[0084] The hydrophilic silica emulsion was mixed with natural rubber latex containing 1000g of dry rubber and stirred thoroughly until it became a thick paste. The mixture was then transferred to a stainless steel tray and allowed to stand and solidify for 12 hours. Finally, it was dried at 120°C to obtain the silica wet-process rubber.

[0085] Compared with Example 2, the lecithin in Example 2 was replaced with the surfactant "phosphatidylethanolamine" (Comparative Example 3). After adding phosphatidylethanolamine in Comparative Example 3, the coagulation time of natural rubber latex became longer and the coagulation effect became worse (incomplete coagulation). This is because phosphatidylethanolamine is weakly alkaline, which is not conducive to coagulation.

[0086] Example 4

[0087] The preparation method is basically the same as in Example 2, except that the "hydrophilic silica" used in Example 2 is replaced with "fumed silica". The specific steps are as follows:

[0088] 10g of lecithin was dispersed in water by high-speed stirring to obtain a lecithin emulsion. 500g of fumed silica was added to the lecithin emulsion and 1g of coagulating enzyme (papain) was added and stirred thoroughly to obtain a fumed silica emulsion.

[0089] The fumed silica emulsion was mixed with natural rubber latex containing 1000g of dry rubber and stirred thoroughly until it became a viscous paste. The mixture was then transferred to a stainless steel tray and allowed to stand and solidify for 12 hours. Finally, it was dried at 120°C to obtain wet fumed silica rubber.

[0090] In this embodiment, "fumed silica" was directly mixed with lecithin emulsion. Due to the hydrophilicity of the silanol groups on the surface of fumed silica, the prepared silica wet-process adhesive had good dispersibility. However, some agglomeration of the silica itself resulted in some precipitation in the silica wet-process adhesive. In contrast, Example 2 used "hydrophilic silica" as the raw material, and the resulting silica wet-process adhesive had significantly better dispersibility than the product prepared in Example 4. The hydrophilic silica itself did not agglomerate, and the silica wet-process adhesive obtained in Example 2 had no precipitation.

[0091] In Example 1, the precipitation phenomenon of the wet process silica gel prepared by mixing and emulsifying "oleophilic silica" with phospholipids was improved.

[0092] Comparative Example 4

[0093] 500g of fumed silica was dispersed in water, and 1g of coagulating enzyme (papain) was added and stirred thoroughly to obtain a fumed silica emulsion.

[0094] The fumed silica emulsion was mixed with natural rubber latex containing 1000g of dry rubber and stirred thoroughly until it became a viscous paste. The mixture was then transferred to a stainless steel tray and allowed to stand and solidify for 12 hours. Finally, it was dried at 120°C to obtain wet fumed silica adhesive.

[0095] Comparative Example 4 directly blended and coagulated fumed silica with natural rubber latex. After coagulation, a large amount of silica precipitated, indicating uneven mixing. During the processing and mixing process, some silica turned into dust.

[0096] As can be seen from the above embodiments, the present invention provides a method for preparing wet-process silica rubber, comprising the following steps: mixing silica, phospholipid emulsion, and coagulating enzyme to obtain silica emulsion; mixing the silica emulsion with natural rubber latex to obtain a paste; and subjecting the paste to static coagulation and drying sequentially to obtain the silica wet-process silica rubber. The preparation method provided by the present invention uses phospholipid as a dispersant and coagulating enzyme as an auxiliary coagulant, which improves the mechanical properties of the vulcanized rubber. Furthermore, it eliminates the need for pre-emulsification of the natural rubber latex, thereby increasing the production efficiency of the silica wet-process silica rubber and reducing costs.

[0097] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing wet-process silica adhesive, characterized in that, Includes the following steps: Hydrophilic silica, phospholipid emulsion and coagulating enzyme are mixed to obtain silica emulsion, wherein the coagulating enzyme is a protease, and the phospholipid emulsion includes phospholipid and water, wherein the phospholipid is lecithin. The silica emulsion and natural rubber latex are mixed to obtain a paste, wherein the coagulating enzyme accounts for 0.1% of the dry rubber mass in the natural rubber latex. The paste was subjected to static solidification and drying in sequence to obtain the wet-process silica adhesive.

2. The preparation method according to claim 1, characterized in that, The phospholipids in the phospholipid emulsion account for 1-5% of the mass percentage of the hydrophilic silica.

3. The preparation method according to claim 1, characterized in that, The mass ratio of the hydrophilic silica to the dry rubber in the natural rubber latex is 1:2~3.

4. The preparation method according to claim 1, characterized in that, The settling and solidification time is 8-24 hours; the drying temperature is 100-120℃.

5. The wet-process silica adhesive prepared by the preparation method according to any one of claims 1 to 4.

6. A vulcanizate, characterized in that, The preparation raw materials include the following parts by weight: The wet-process precipitate of silica as described in claim 5 contains 150-180 parts, zinc oxide 3-5 parts, stearic acid 1-2 parts, antioxidant 1-2 parts, coupling agent 2-6 parts, accelerator 2-3 parts, and sulfur 1-2 parts.

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