Low-zinc rubber composition with high vulcanization activity and preparation method therefor

Abstract

The present invention belongs to the technical field of rubber composite materials, and discloses a low-zinc rubber composition with high vulcanization activity and a preparation method therefor. The rubber composition is composed of the following components in parts by weight: 100 parts of rubber, 0-110 parts of white carbon black, 5-80 parts of carbon black, 0-8 parts of a silane coupling agent, 3-7 parts of an anti-aging agent, 0-5 parts of a Rhin plastic component, 2-20 parts of a rubber processing oil, 0-5 parts of zinc oxide, 0-2 parts of stearic acid, 1-7 parts of an organic zinc ion complex, 1-2.5 parts of a vulcanizing agent and 1-4 parts of a vulcanization accelerator. By introducing the organic zinc ion complex to partially or completely replace zinc oxide and stearic acid, the content of zinc in the rubber composition can be reduced by up to 95%, and other active substances do not need to be additionally combined and used.

Description

A low-zinc rubber composition with high vulcanization activity and preparation method thereof Technical Field

[0001] The present invention relates to a rubber composition and a preparation method thereof, in particular to a low-zinc rubber composition with high vulcanization activity and a preparation method thereof, belonging to the technical field of rubber composite materials. Background Art

[0002] The vulcanization system for tire rubber products primarily consists of sulfur, accelerators, and activators. The activator improves the vulcanization efficiency of the rubber. In sulfur vulcanization systems, zinc oxide and stearic acid are typically used as activators. During the rubber vulcanization process, zinc oxide reacts with stearic acid to form a soluble zinc salt. This soluble zinc salt then reacts with polysulfide radicals in the system to form zinc sulfide and disulfide. The disulfide then crosslinks with the rubber macromolecules, ultimately forming a three-dimensional crosslinked network. Wear debris from tires during operation releases significant amounts of zinc into the environment. However, long-term monitoring in Europe confirmed in 2003 that zinc oxide poses an environmental pollution hazard. It was classified as Category N in the list of hazardous substances in EU Regulation 2003 / 105 / EC, meaning it is very harmful to aquatic life and can have long-term adverse effects on aquatic ecosystems. Consequently, research into zinc reduction technologies is becoming increasingly widespread in the rubber products industry.

[0003] According to the reaction mechanism of zinc oxide and stearic acid, the substance that activates the rubber vulcanization process is a soluble zinc salt. Currently, the most effective technology for reducing zinc in the rubber industry is to use organic zinc salts to replace zinc oxide and stearic acid. For example, Chinese patent CN107652489A uses fatty acid zinc compounds to completely replace zinc oxide and stearic acid, reducing the zinc content by 85%. However, the zinc content in the fatty acid zinc salt is too low and the reaction activity is low. Therefore, it is necessary to introduce organic fatty acid rare earth metal salts to improve the activity of the fatty acid zinc salt, thereby ensuring the comprehensive physical properties of the vulcanized rubber.

[0004] It can be seen that in the current effective zinc reduction technology solutions, due to the insufficient activity of organic zinc salts, in order to improve their reaction activity, it is necessary to compound and use fatty acid rare earth metal salt compounds, which will inevitably increase the formulation cost of rubber. Summary of the Invention

[0005] To address the deficiencies of the prior art, the present invention aims to provide a low-zinc rubber composition and its preparation method which does not require the use of additional active substances such as fatty acid rare earth metal salt compounds, has a low formulation cost, and has high vulcanization activity.

[0006] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0007] A low-zinc rubber composition with high vulcanization activity, comprising the following components in parts by weight:

[0008] 100 parts of rubber, 0-110 parts of white carbon black, 5-80 parts of carbon black, 0-8 parts of silane coupling agent, 3-7 parts of antioxidant, 0-5 parts of Rhine plastic, 2-20 parts of rubber processing oil, 0-5 parts of zinc oxide, 0-2 parts of stearic acid, 1-7 parts of organic zinc ion complex, 1-2.5 parts of vulcanizing agent, and 1-4 parts of vulcanization accelerator.

[0009] Preferably, the rubber composition consists of the following components:

[0010] 100 parts of rubber, 65 parts of white carbon black, 15 parts of carbon black, 5.2 parts of silane coupling agent, 6 parts of antioxidant, 3 parts of Rhine plastic, 9 parts of rubber processing oil, 0-2 parts of zinc oxide, 0-1.33 parts of stearic acid, 1-3 parts of organic zinc ion complex, 2 parts of vulcanizing agent, and 3.5 parts of vulcanization accelerator.

[0011] Preferably, the rubber is a mixture of any one or more of natural rubber, polyisoprene rubber, solution-polymerized styrene-butadiene rubber, emulsion-polymerized styrene-butadiene rubber, polybutadiene rubber, ternary integrated rubber, functionalized modified styrene-butadiene rubber and functionalized modified polybutadiene rubber.

[0012] Preferably, the vulcanization accelerator is any one of a sulfenamide accelerator, a thiazole accelerator and a diphenylguanidine accelerator, or a mixture of two of them.

[0013] Preferably, the molecular structure of the organic zinc ion complex is [Zn(R') n ](RCOO)2, R is selected from a linear, branched, cyclic or non-cyclic alkyl group, aryl group, aralkyl group or alkaryl group having 1 to 16 carbon atoms, R' is selected from a promoter group containing a nitrogen atom, a sulfur atom or an oxygen atom, n=1, 2, 3 or 4; more preferably, the promoter group containing a nitrogen atom, a sulfur atom or an oxygen atom includes: thiazole, sulfonamide, thiuram, dithiocarbamic acid, guanidine, aldehyde amine and xanthate group; most preferably, the molecular structure of the organic zinc ion complex is [Zn(R')2](RCOO)2, R is a linear alkyl group having 4 carbon atoms, and R' is dibenzothiazole disulfide.

[0014] A method for preparing the aforementioned low-zinc rubber composition with high vulcanization activity comprises the following steps:

[0015] Step 1: Set the initial temperature in the internal mixer to 90°C and plasticize the rubber in the internal mixer for 40 to 90 seconds;

[0016] Step 2: Lift the top bolt into place, add carbon black, white carbon black, Rheinland plastic fraction, rubber processing oil, zinc oxide, stearic acid, organic zinc ion complex, silane coupling agent and antioxidant into the internal mixer and mix until the temperature in the internal mixer reaches 125°C;

[0017] Step 3: Lift the top bolt for 5 seconds, then press it down. When the temperature in the internal mixer reaches 145°C, lift the top bolt again and press it down after 5 seconds. When the temperature of the rubber compound in the internal mixer reaches 155°C, maintain 155°C for a total of 120 seconds, and discharge the rubber to obtain a mixed rubber.

[0018] Step 4: Cool the obtained rubber mix at room temperature;

[0019] Step 5: Add the vulcanizing agent and vulcanization accelerator on a two-roll mill and mix until all components are dispersed into the rubber compound;

[0020] Step 6: Roll the rubber mix, adjust the roller distance, and make a thin pass before discharging the sheet to obtain a low-zinc rubber composition with high vulcanization activity.

[0021] The benefits of the present invention are as follows: by introducing an organic zinc ion complex (as an activator) to partially or completely replace zinc oxide and stearic acid, the zinc content in the rubber composition can be reduced by up to 95%. The organic zinc ion complex has excellent compatibility with the rubber matrix, and the coordination of the promoting group in the molecular structure can significantly increase the reactivity of the zinc ion, greatly improving its vulcanization activity. There is no need to additionally use other active substances such as fatty acid rare earth metal salt compounds. Under vulcanization conditions, the present invention can intensify the S8 ring rupture and the cracking of the accelerator in the vulcanization system, thereby generating more sulfur-containing active bodies and diradical active sulfur, accelerating the formation of the rubber vulcanization network structure, and simultaneously reducing the formulation cost of the rubber composition. DETAILED DESCRIPTION

[0022] The present invention is described in detail below with reference to specific embodiments.

[0023] 1. Preparation of low-zinc rubber compositions with high vulcanization activity

[0024] The low-zinc rubber composition with high vulcanization activity provided by the present invention is composed of the following components in parts by weight:

[0025] 100 parts of rubber, 0-110 parts of white carbon black, 5-80 parts of carbon black, 0-8 parts of silane coupling agent, 3-7 parts of antioxidant, 0-5 parts of Rhine plastic, 2-20 parts of rubber processing oil, 0-5 parts of zinc oxide, 0-2 parts of stearic acid, 1-7 parts of organic zinc ion complex, 1-2.5 parts of vulcanizing agent, and 1-4 parts of vulcanization accelerator.

[0026] in:

[0027] (1) Rubber: any one or more of natural rubber, polyisoprene rubber, solution-polymerized styrene-butadiene rubber, emulsion-polymerized styrene-butadiene rubber, polybutadiene rubber, ternary integrated rubber, functionalized modified styrene-butadiene rubber and functionalized modified polybutadiene rubber can be used;

[0028] (2) Vulcanization accelerator: any one of sulfonamide accelerators, thiazole accelerators and diphenylguanidine accelerators or a mixture of two of them can be selected;

[0029] (3) Organic zinc ion complex: The molecular structure is [Zn(R') n ](RCOO)2, R represents a hydrocarbon group, which is selected from a linear, branched, cyclic or non-cyclic alkyl group, aryl group, aralkyl group or alkaryl group having 1 to 16 carbon atoms, R' represents a accelerator group containing a nitrogen atom, a sulfur atom or an oxygen atom, including but not limited to thiazoles, sulfonamides, thiurams, dithiocarbamic acids, guanidines, aldehyde amines, xanthates and the like, the nitrogen, sulfur or oxygen in these groups can form coordination with zinc ions, n represents the coordination number, n=1, 2, 3 or 4, the coordination of the R' group can significantly increase the reactivity of the zinc ion, and thereby increase the vulcanization activity of the organic zinc ion complex.

[0030] The preparation method of the low-zinc rubber composition with high vulcanization activity is specifically as follows:

[0031] Set the speed of the internal mixer to 80rpm and the starting temperature of the internal mixer to 90℃. Plasticate the rubber in the internal mixer for 65s (can be adjusted within the range of 40 to 90s). After the top bolt is raised, carbon black, white carbon black, Rhine plastic fraction, rubber processing oil, zinc oxide, stearic acid, organic zinc ion complex, silane coupling agent and antioxidant are added to the internal mixer for mixing. When the temperature in the internal mixer reaches 125℃, raise the top bolt for 5s, then press the top bolt down. When the temperature in the internal mixer reaches 145℃, When the temperature of the rubber compound in the internal mixer reaches 155°C, reduce the speed of the internal mixer to 50 rpm and maintain 155°C for a total of 120 seconds. The rubber is discharged to obtain a rubber mix. After the rubber mix is ​​cooled at room temperature for 8 hours, vulcanizing agent and vulcanization accelerator are added on a two-roll open mill. After mixing until all components are dispersed into the rubber compound, the rubber mix is ​​rolled up 5 times, the roller distance is adjusted to 2 mm, and thin-passed 5 times before discharging the sheet to obtain a low-zinc rubber composition with high vulcanization activity.

[0032] In this specific embodiment, the rubber used is a mixture of natural rubber and solution-polymerized styrene-butadiene rubber (SBR), both of which are mixed in equal amounts. The vulcanization accelerator used is a thiazole-based accelerator. The molecular structure of the organic zinc ion complex used is [Zn(R')2](RCOO)2, where R is a linear alkyl group having four carbon atoms and R' is dibenzothiazyl disulfide. Six rubber composition samples were prepared using the above method. The corresponding formulas for each sample are shown in Table 1.

[0033] Table 1 Recipes of 6 rubber composition samples (parts by weight)

[0034] Raw materials Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Example 5 Natural rubber / solution-polymerized styrene-butadiene rubber 100100100100100100100 White carbon black 656565656565 Carbon black 151515151515 Silane coupling agent 5.25.25.25.25.25.2 Rubber processing oil 999999 Antiaging agent 666666 Rhine Plastics 333333 Stearic acid 21.3310.6700 Zinc oxide 321.5100 Organic zinc ion complex 011.5233 Vulcanization accelerator 3.53.53.53.53.52 Vulcanizing agent (sulfur) 222222 Total 213.7213.03212.7212.37211.7210.2

[0035] 2. Testing the performance parameters of each rubber composition sample

[0036] The six rubber composition samples were tested using a Norman MDR-S3 rheometer at 151° C. for 60 minutes. The test results are shown in Table 2.

[0037] Table 2 Rheometer test results of 6 rubber composition samples

[0038] Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Example 5 Mooney viscosity [ML(1+4) 100℃] 54.63 52.51 51.84 50.77 52.34 56.49 Scorch time T5 (127℃) / min 24.88 21.00 20.56 18.42 13.08 25.14 ML / (dN•m) 1.83 1.80 1.70 1.66 1.83 2.40 MH / (dN•m) 15.14 15.06 14.44 14.33 14. 4014.95MH-ML / (dN·m)13.3113.2612.7412.6712.5712.55T10 / min5.324.604.784.222 .622.19T25 / min6.445.505.685.013.276.73T90 / min16.5214.6714.2512.997.1016.72

[0039] From the data in Table 2 we can see that:

[0040] (1) Compared with the rubber composition of comparative example 1, as the amount of zinc oxide and stearic acid replaced by the organic zinc ion complex increases until they are completely replaced, the scorch time T5 and the positive vulcanization time T90 of the rubber composition of Examples 1 to 4 are gradually shortened, and the crosslinking density MH-ML is slightly reduced, with the maximum reduction being 5.56%, which is basically at the same level. This shows that the vulcanization activity of the organic zinc ion complex is significantly higher than that of the composite activation system of zinc oxide and stearic acid. The organic zinc ion complex has excellent compatibility with the rubber matrix. The promoting groups containing sulfur, nitrogen or oxygen in the molecular structure coordinate with the zinc ion, which greatly improves the reaction activity of the zinc ion, aggravates the S8 ring rupture and the cracking of the vulcanization accelerator in the vulcanization system under vulcanization conditions, and generates more sulfur-containing active bodies and diradical active sulfur, which effectively accelerates the formation of the rubber vulcanization network structure;

[0041] (2) Considering that the vulcanization speeds of the rubber compositions of each half of the tire need to be matched during the tire manufacturing process, the rubber composition of Example 5 uses an organic zinc ion complex to completely replace zinc oxide and stearic acid, and at the same time reduces the amount of vulcanization accelerator to extend the vulcanization time of the rubber composition. The positive vulcanization time T90 of the rubber composition of Example 5 is equivalent to the positive vulcanization time T90 of the rubber composition of Comparative Example 1, ensuring that the vulcanization speed of the rubber composition of Example 5 is equivalent to the vulcanization speed of the rubber composition of Comparative Example 1. That is, when using an organic zinc ion complex with high vulcanization activity as a vulcanization activator of the rubber composition, the amount of vulcanization accelerator can be dynamically adjusted according to the actual requirements of the vulcanization speed of the product components.

[0042] The six rubber composition samples were vulcanized at 151° C. for 30 min, and then the mechanical properties and wear resistance of each rubber composition sample were tested. The test results are shown in Table 3.

[0043] Table 3 Mechanical properties and wear resistance test results of 6 rubber composition samples

[0044] Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Example 5 Shore A hardness / degree 64.865.164.164.96265.3 Tensile strength / MPa16.316.215.616.218.016.9 Elongation at break / %452448439459540452M100 / Mpa2.32.62.52.42.02.4M300 / Mpa9.610.010.09.58.410.0DIN wear volume / (mm 3 / 40m)156.5138.4135.2122.8111.3122.9

[0045] From the data in Table 3 we can see that:

[0046] (1) Compared with the rubber composition of Comparative Example 1, the hardness, M100 and M300 of the rubber compositions of Examples 1 to 4 all show a trend of first increasing and then gradually decreasing as the amount of zinc oxide and stearic acid replaced by the organic zinc ion complex increases until the organic zinc ion complex completely replaces them, that is, the modulus of the rubber composition gradually decreases; the DIN wear volume of the rubber composition gradually decreases, and the smaller the wear volume, the better the wear resistance of the rubber composition, that is, as the amount of zinc oxide and stearic acid replaced by the organic zinc ion complex increases until the organic zinc ion complex completely replaces them, the wear resistance of the rubber composition gradually improves, with the maximum increase reaching 28.89%;

[0047] (2) Compared with the rubber composition of Comparative Example 1, the rubber composition of Example 5 uses an organic zinc ion complex to completely replace zinc oxide and stearic acid, and at the same time reduces the amount of vulcanization accelerator. On the premise that the vulcanization speed of the rubber composition is equivalent to that of the rubber composition of Comparative Example 1, the mechanical hardness, tensile strength, M100 and M300 of the rubber composition of Example 5 are slightly improved, that is, the modulus of the rubber composition is slightly improved; in addition, the DIN wear volume of the rubber composition of Example 5 is reduced by 21.47%, that is, the wear resistance of the rubber composition is improved by 21.47%.

[0048] Comprehensive analysis of the data in Table 2 and Table 3 shows that:

[0049] The present invention introduces an organic zinc ion complex as an active agent into the rubber composition, partially replacing or completely replacing traditional active agents zinc oxide and stearic acid. While maintaining relatively higher vulcanization activity, the zinc content in the rubber composition can be reduced by up to 95%. The mechanical modulus of the rubber composition is slightly reduced, but the wear resistance is significantly improved, with the wear resistance increase reaching 28.89%.

[0050] In summary, the low-zinc rubber composition with high vulcanization activity provided by the present invention has excellent wear resistance while maintaining excellent mechanical properties, and can be applied to the tread, sidewall, bead, apex, support rubber and other parts of the tire.

[0051] It should be noted that the above embodiments are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications may be made based on the above description. It is not possible to enumerate all embodiments here. Any obvious variations or modifications arising from the technical solution of the present invention remain within the scope of protection of the present invention.

Claims

1. A low-zinc rubber composition with high vulcanization activity, characterized in that: The rubber composition is composed of the following components in parts by weight: 100 parts of rubber, 0-110 parts of white carbon black, 5-80 parts of carbon black, 0-8 parts of silane coupling agent, 3-7 parts of antioxidant, 0-5 parts of Rhine plastic, 2-20 parts of rubber processing oil, 0-5 parts of zinc oxide, 0-2 parts of stearic acid, 1-7 parts of organic zinc ion complex, 1-2.5 parts of vulcanizing agent, and 1-4 parts of vulcanization accelerator.

2. The low-zinc rubber composition with high vulcanization activity according to claim 1, characterized in that The rubber composition is composed of the following components in parts by weight: 100 parts of rubber, 65 parts of white carbon black, 15 parts of carbon black, 5.2 parts of silane coupling agent, 6 parts of antioxidant, 3 parts of Rhine plastic, 9 parts of rubber processing oil, 0-2 parts of zinc oxide, 0-1.33 parts of stearic acid, 1-3 parts of organic zinc ion complex, 2 parts of vulcanizing agent, and 3.5 parts of vulcanization accelerator.

3. The low-zinc rubber composition with high vulcanization activity according to claim 1 or 2, characterized in that: The rubber is selected from any one or more of natural rubber, polyisoprene rubber, solution-polymerized styrene-butadiene rubber, emulsion-polymerized styrene-butadiene rubber, polybutadiene rubber, ternary integrated rubber, functionalized modified styrene-butadiene rubber and functionalized modified polybutadiene rubber.

4. The low-zinc rubber composition with high vulcanization activity according to claim 1 or 2, characterized in that: The vulcanization accelerator is selected from any one of sulfenamide accelerators, thiazole accelerators and diphenylguanidine accelerators, or a mixture of two of them.

5. The low-zinc rubber composition with high vulcanization activity according to claim 1 or 2, characterized in that: The molecular structure of the organic zinc ion complex is [Zn(R') n ](RCOO)2, R is selected from a linear, branched, cyclic or non-cyclic alkyl, aryl, aralkyl or alkaryl group having 1 to 16 carbon atoms, R' is selected from a promoter group containing a nitrogen atom, a sulfur atom or an oxygen atom, and n=1, 2, 3 or 4.

6. The low-zinc rubber composition with high vulcanization activity according to claim 5, characterized in that: The accelerator groups containing nitrogen atoms, sulfur atoms or oxygen atoms include thiazoles, sulfenamides, thiurams, dithiocarbamic acids, guanidines, aldehyde amines and xanthates.

7. The low-zinc rubber composition with high vulcanization activity according to claim 5, characterized in that: The molecular structure of the organic zinc ion complex is [Zn(R')2](RCOO)2, where R is a straight-chain alkyl group having 4 carbon atoms and R' is dibenzothiazole disulfide.

8. A method for preparing the low-zinc rubber composition with high vulcanization activity according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1: Set the initial temperature in the internal mixer to 90°C and plasticize the rubber in the internal mixer for 40 to 90 seconds; Step 2: Lift the top bolt into place, add carbon black, white carbon black, Rheinland plastic fraction, rubber processing oil, zinc oxide, stearic acid, organic zinc ion complex, silane coupling agent and antioxidant into the internal mixer and mix until the temperature in the internal mixer reaches 125°C; Step 3: Lift the top bolt for 5 seconds, then press it down. When the temperature in the internal mixer reaches 145°C, lift the top bolt again and press it down after 5 seconds. When the temperature of the rubber compound in the internal mixer reaches 155°C, maintain 155°C for a total of 120 seconds, and discharge the rubber to obtain a mixed rubber. Step 4: Cool the obtained rubber mix at room temperature; Step 5: Add the vulcanizing agent and vulcanization accelerator on a two-roll mill and mix until all components are dispersed into the rubber compound; Step 6: Roll the rubber mix, adjust the roller distance, and make a thin pass before discharging the sheet to obtain a low-zinc rubber composition with high vulcanization activity.