Rubber activator and preparation method thereof

Abstract

The invention belongs to the technical field of rubber vulcanization activators, and particularly relates to a rubber activator and a preparation method thereof. The rubber activator comprises the following raw materials by weight: 20-80 wt% of an organic zinc compound; 80-20 wt% of an activator complex salt; the organic zinc compound is a zinc salt of an aromatic compound or a zinc salt of an aliphatic compound; the zinc salt of the aromatic compound and the zinc salt of the aliphatic compound comprise one or more carboxyl groups; the activator complex salt comprises one or more of an inorganic zinc compound, an aryl-containing organic acid compound, a straight-chain aliphatic organic acid compound and an organic acid compound containing double bonds. The rubber activator provided by the invention has the advantages of low zinc content (lower than 40%), heavy metal content tending to zero, safety, environmental protection, low density and good dispersity, and the effect is superior to the experimental effect of zinc oxide.

Description

Technical Field

[0001] This invention belongs to the technical field of rubber vulcanization activators, specifically relating to a rubber activator and its preparation method. Background Technology

[0002] Activators, also known as accelerators, are added during the rubber vulcanization process to increase the activity of accelerators, thereby reducing the amount of accelerator needed, increasing the vulcanization speed, and shortening the vulcanization time. Since zinc oxide was first used as an activator in 1912, no completely substitute has been found. Although zinc oxide is important to the rubber industry, it is released into the environment as zinc ions during rubber production and use, which can have adverse effects on human health, especially on aquatic organisms. Furthermore, zinc oxide production is energy-intensive, costly, and expensive. Therefore, it is important and urgent to invent a more environmentally friendly, greener, more active, and economical alternative to zinc oxide that reduces its usage without compromising performance. Summary of the Invention

[0003] Technical problem solved: This invention provides a rubber activator and its preparation method, which can effectively solve the problem of adverse effects on human health and aquatic organisms during the traditional production and use of rubber.

[0004] In a first aspect, the present invention provides a rubber activator, which adopts the following technical solution:

[0005] A rubber activator, comprising the following raw materials by weight percentage: organic zinc compound: 20-80 wt%; activator compounding salt: 80-20 wt%;

[0006] Organozinc compounds are zinc salts of aromatic compounds or zinc salts of aliphatic compounds; the zinc salts of aromatic compounds and zinc salts of aliphatic compounds contain one or more carboxyl groups;

[0007] The activator complex salt includes one or more of the following: inorganic zinc compounds, aromatic organic acid compounds, straight-chain aliphatic organic acid compounds, and organic acid compounds containing double bonds.

[0008] As a preferred technical solution, a rubber activator includes one or more of the following: zinc salts of aromatic compounds: zinc benzoate, zinc salicylate, zinc para-aminobenzoate, and zinc naphthoate; and one or more of the following: zinc salts of aliphatic compounds: zinc acetate, zinc stearate, zinc oleate, zinc propionate, and zinc adipate.

[0009] As a preferred technical solution, a rubber activator comprises one or more of the following inorganic zinc compounds: zinc oxide, zinc sulfate, zinc chloride, zinc nitrate, basic zinc carbonate, zinc powder, zinc phosphate, and zinc sulfite.

[0010] As a preferred technical solution, a rubber activator includes an aromatic organic acid compound comprising one or more of salicylic acid, cinnamic acid, phthalic acid, and terephthalic acid.

[0011] As a preferred technical solution, a rubber activator comprises one or more linear aliphatic organic acid compounds, including formic acid, acetic acid, stearic acid, oleic acid, and linoleic acid.

[0012] As a preferred technical solution, a rubber activator includes one or more organic acid compounds containing double bonds, such as maleic acid, itaconic acid, and sorbic acid.

[0013] Secondly, the present invention provides a method for preparing a rubber activator, comprising the following steps:

[0014] Step 1: Synthesize organozinc compounds;

[0015] Organic acid or organic anhydride is mixed with zinc oxide in a molar ratio of 1:1 to 4:1, solvent A is added, the mixture is placed in an ice-water bath and stirred to cool it, and then sonicated for 10 min to 3 h. After that, the temperature is raised to 50 to 80 °C and reacted for 30 min to 3 h. After the reaction is completed, the mixture is dried at 80 °C to 130 °C for 1 to 12 h to obtain an organozinc compound.

[0016] Step 2: Prepare the activator complex salt;

[0017] At least one organic acid is mixed with a metal oxide, solvent B is added, the mixture is stirred and ultrasonically treated for 10-30 min at room temperature, reacted at 50-80℃ for 30 min-2 h, and dried at 90-120℃ for 8-12 h after the reaction is completed to obtain an activator complex salt.

[0018] Step 3: Mix;

[0019] The organozinc compound obtained in step 1 and the activator salt obtained in step 2 are mixed uniformly at a predetermined weight percentage, and then mixed, dried, ground and passed through a 350-mesh sieve to obtain the rubber activator.

[0020] As a preferred technical solution, in a method for preparing a rubber activator, in step 1, solvent A includes one or more of water, ethanol, methanol, dichloromethane, petroleum ether, ethyl acetate, n-propanol, n-butanol, isobutanol, and acetonitrile; in step 2, solvent B includes one or more of water, n-butanol, and ethyl acetate.

[0021] As a preferred technical solution, in a method for preparing a rubber activator, in step 1, the organic acid includes one or more of sorbic acid, citric acid, pyridine dicarboxylic acid and oleic acid; the organic acid anhydride includes one or more of acetic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride and pyromellitic dianhydride.

[0022] As a preferred technical solution, in a method for preparing a rubber activator, step 2 includes one or more of the following organic acids: sorbic acid, citric acid, pyridinedicarboxylic acid, and oleic acid; and the following metal oxides include one or more of the following: sodium oxide, calcium oxide, potassium oxide, and magnesium oxide.

[0023] Thirdly, the present invention provides a rubber comprising the above-mentioned rubber activator.

[0024] Beneficial effects: The rubber activator provided by this invention has a zinc content of less than 40% and a heavy metal content close to zero, making it safe and environmentally friendly; moreover, it has low density and good dispersibility, and the rubber samples prepared using it have better performance than those prepared with zinc oxide. Attached Figure Description

[0025] Figure 1 Comparison chart of Mooney viscosity of rubber samples;

[0026] Figure 2 Mooney scorch time curve of rubber sample;

[0027] Figure 3 : Curve of vulcanization characteristics (torque-time) of rubber sample;

[0028] Figure 4 Comparison chart of rubber sample densities;

[0029] Figure 5 Comparison chart of hardness of rubber samples;

[0030] Figure 6 Comparison of the resilience of rubber samples;

[0031] Figure 7 Comparison of volumetric wear of rubber samples;

[0032] Figure 8 : Tensile stress-strain curve of rubber specimen;

[0033] Figure 9 Comparison of tensile properties of rubber samples before and after wet heat aging;

[0034] Figure 10 Comparison chart of steel wire extraction performance of rubber samples;

[0035] Figure 11 Comparison of temperature rise during compression fatigue of rubber samples;

[0036] Figure 12 Comparison of compression set of rubber samples;

[0037] Figure 13 Comparison of flexural crack development in rubber samples. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0040] Example 1

[0041] In this embodiment, cinnamic acid was purchased from Hubei Qibu New Material Technology Co., Ltd., zinc oxide from Jiangsu Tiancheng Zinc Industry Technology Co., Ltd., sorbic acid from Shanghai Gaoming Chemical Co., Ltd., and sodium oxide from Shanghai Yuanye Biotechnology Co., Ltd.

[0042] This embodiment provides a method for preparing a rubber activator, specifically including the following steps:

[0043] (1) Preparation of product A: At room temperature, 72.6 kg of cinnamic acid and 23.8 kg of zinc oxide were mixed, and a mixed solvent consisting of 59.2 kg of ethanol and 25 kg of water was added. The mixture was placed in an ice-water bath and stirred (stirring speed of 200 r / min) to cool it. It was then sonicated for 1 h, and then reacted at 70 °C for 3 h. After the reaction was completed, it was dried at 120 °C for 12 h to obtain product A.

[0044] (2) Preparation of product B: Under normal temperature conditions, 71.4 kg of sorbic acid and 28.6 kg of sodium oxide were mixed, 10 kg of water was added, the mixture was stirred and ultrasonically treated for 10 min, and then reacted at 50 °C for 50 min. After the reaction was completed, the mixture was dried at 100 °C for 12 h to obtain product B.

[0045] (3) The product A obtained in step (1) and the product B obtained in step (2) are mixed at a mass ratio of 75:25, dried uniformly, ground and passed through a 350-mesh standard sieve to obtain the rubber activator.

[0046] Example 2

[0047] In this embodiment, lauric acid was purchased from Shandong Qiangsen Chemical Co., Ltd., zinc oxide from Jiangsu Tiancheng Zinc Industry Technology Co., Ltd., citric acid from Changsha Shengyang Chemical Materials Co., Ltd., and calcium oxide from Jiangxi Huancheng New Materials Co., Ltd.

[0048] This embodiment provides a method for preparing a rubber activator, specifically including the following steps:

[0049] (1) Preparation of product A: Under normal temperature conditions, 81.7 kg of lauric acid and 18.3 kg of zinc oxide were mixed, and a mixed solvent consisting of 30 kg of methanol and 70 kg of water was added. The mixture was placed in an ice-water bath and stirred (stirring speed of 200 r / min) to cool it down. It was then subjected to ultrasonic treatment for 30 min, and then reacted at 60 °C for 1 h. After the reaction was completed, it was dried at 120 °C for 12 h to obtain product A.

[0050] (2) Preparation of product B: At room temperature, 70.1 kg of citric acid and 29.9 kg of calcium oxide were mixed, 5 kg of n-butanol was added, the mixture was stirred and ultrasonically treated for 30 min, and then reacted at 80 °C for 2 h. After the reaction was completed, the mixture was dried at 120 °C for 12 h to obtain product B.

[0051] (3) Mix product A obtained in step (1) and product B obtained in step (2) at a mass ratio of 60:40 to obtain the rubber activator.

[0052] Example 3

[0053] In this embodiment, salicylic acid was purchased from Shandong Qiangsen Chemical Co., Ltd., zinc oxide from Jiangsu Tiancheng Zinc Industry Technology Co., Ltd., pyridine dicarboxylic acid from Liaoning Wanwusheng Chemical Co., Ltd., and potassium oxide from Henan Tianfu Chemical Co., Ltd.

[0054] This embodiment provides a method for preparing a rubber activator, specifically including the following steps:

[0055] (1) Preparation of product A: At room temperature, 77.3 kg of salicylic acid and 22.8 kg of zinc oxide were mixed, and a mixed solvent consisting of 40 kg of n-butanol and 60 kg of water was added. The mixture was placed in an ice-water bath and stirred (stirring speed of 200 r / min) to cool it down. It was then sonicated for 50 min and reacted at 70 °C for 1.5 h. After the reaction was completed, it was dried at 100 °C for 12 h to obtain product A.

[0056] (2) Preparation of product B: Under normal temperature conditions, 64 kg of pyridine dicarboxylic acid and 36 kg of potassium oxide were mixed, 5 kg of ethyl acetate was added, stirred and ultrasonically treated for 20 min, and then reacted at 80 °C for 30 min. After the reaction was completed, the mixture was dried at 90 °C for 12 h to obtain product B.

[0057] (3) The product A obtained in step (1) and the product B obtained in step (2) are mixed at a mass ratio of 80:20, dried uniformly, ground and passed through a 350-mesh standard sieve to obtain the rubber activator.

[0058] Example 4

[0059] In this embodiment, succinic acid was purchased from Shanghai Yuanye Biotechnology Co., Ltd., zinc oxide from Jiangsu Tiancheng Zinc Industry Technology Co., Ltd., oleic acid from Shandong Chuangying Chemical Co., Ltd., and magnesium oxide from Sichuan Huayuanshengtai Biotechnology Co., Ltd.

[0060] This embodiment provides a method for preparing a rubber activator, specifically including the following steps:

[0061] (1) Preparation of product A: At room temperature, 59.2 kg of succinic acid and 40.8 kg of zinc oxide were mixed, and a mixed solvent consisting of 92.5 kg of isobutanol and 7.5 kg of water was added. The mixture was placed in an ice-water bath and stirred (stirring speed of 200 r / min) to cool it down. It was then sonicated for 1 h, and then reacted at 80 °C for 1 h. After the reaction was completed, it was dried at 100 °C for 12 h to obtain product A.

[0062] (2) Preparation of product B: Under normal temperature conditions, 94 kg of oleic acid and 6 kg of magnesium oxide were mixed, 20 g of ethyl acetate was added, the mixture was stirred and ultrasonically treated for 30 min, and then reacted at 80 °C for 2 h. After the reaction was completed, the mixture was dried at 100 °C for 12 h to obtain product B.

[0063] (3) The product A obtained in step (1) and the product B obtained in step (2) are mixed at a mass ratio of 50:50, dried evenly, ground and passed through a 350-mesh standard sieve to obtain the rubber activator.

[0064] Example 5

[0065] In this embodiment, itaconic acid was purchased from Shanghai Yuanye Biotechnology Co., Ltd., and zinc oxide was purchased from Jiangsu Tiancheng Zinc Industry Technology Co., Ltd.

[0066] This embodiment provides a method for preparing a rubber activator, specifically including the following steps:

[0067] (1) Preparation of product A: Under normal temperature conditions, 61.5 kg itaconic acid and 38.5 kg zinc oxide were mixed, and a mixed solvent consisting of 87.67 kg methanol and 12.33 kg water was added. The mixture was placed in an ice-water bath and stirred (stirring speed of 200 r / min) to cool it down. It was then subjected to ultrasonic treatment for 1.5 h, and then reacted at 75 °C for 2 h. After the reaction was completed, it was dried at 100 °C for 12 h to obtain product A.

[0068] (2) In this embodiment, product B is zinc oxide.

[0069] (3) The product A obtained in step (1) and the product B obtained in step (2) are mixed at a mass ratio of 60:40, dried uniformly, ground and passed through a 350-mesh standard sieve to obtain the rubber activator.

[0070] Example 6

[0071] This embodiment provides a comparative experiment on the application of a rubber activator, with the following specific steps: A control group and three experimental groups are set up:

[0072] The control group used conventional zinc oxide (ZnO) as an activator, while the experimental groups used the rubber activators prepared in Examples 1 to 3, respectively.

[0073] 6.1 Test formulation

[0074] The four groups of activators were applied to rubber formulations for comparative experiments. Rubbers containing activators prepared according to the methods in Examples 1, 2, and 3 were labeled as 1#, 2#, 3#, and 4#, respectively. Specific experimental formulations are shown in Table 1.

[0075] Table 1

[0076]

[0077] In Table 1, the amounts of all components are expressed in phr, which is based on 100 parts by weight of raw rubber (RM001). All raw materials used in this experiment are conventional commercially available products in the rubber industry, including: RM001 raw rubber, RM003 carbon black, RA008 a commonly used rubber softening plasticizer, RA002 sulfur, RA003 a rubber antioxidant, RA001 a conventional zinc oxide activator, organic zinc (the rubber activator provided in this invention), RA004 a rubber flame retardant, and RA005 a rubber antistatic agent. Those skilled in the art can select the above-mentioned conventional products to complete this experiment according to the requirements of conventional rubber formulation design.

[0078] 6.2 Test Methods

[0079] Samples of the obtained rubber grades 1#, 2#, 3#, and 4# were taken and their performance was tested according to the following standard methods:

[0080] (1) Mooney viscosity test: Tested according to GB / T 1232.1-2016 standard, test temperature: 100℃, test time: 1 min preheating, 4 min test.

[0081] (2) Mooney scorch test: Tested according to GB / T 16584-1996 standard, test temperature: 120℃.

[0082] (3) Vulcanization characteristics test: Tested according to GB / T 16584-1996 standard, using a vulcanizing apparatus. The test temperature is 150℃, the rotation angle is ±1°, and the test time is 30min.

[0083] (4) Density: Tested according to GB / T 533-2008 standard.

[0084] (5) Hardness: Tested according to GB / T 531.1-2008 standard, test type: Shore A.

[0085] (6) Resilience test: Tested according to GB / T 1681-2009 standard.

[0086] (7) Volumetric wear: Tested according to GB / T 9867-2008 standard, load: 5N.

[0087] (8) Tensile property test: Tested according to GB / T 528-2008 standard, using an electronic testing machine, with a speed of 500 mm / min and a test temperature of room temperature.

[0088] (9) Tear strength: Tested according to GB / T529-2008 standard.

[0089] (10) Damp heat aging performance test: Aging was performed according to GB / T 15905-1995 standard, aging temperature: 40℃, humidity: 93%, aging time: 72h, and after aging, the product was dried and the tensile properties were tested according to GB / T 528-2008.

[0090] (11) Steel wire pull-out test: Tested according to GB / T 3513-2018 standard. Steel wire type: tire bead wire.

[0091] (12) Compression fatigue heat generation test: Tested according to GB / T 1687.3-2016 standard, test temperature: 55℃, test time: 25min.

[0092] (13) Flexural crack test: Tested according to GB / T 13934-2006 standard.

[0093] 6.3 Data Results and Analysis

[0094] 6.3.1 Mooney viscosity and Mooney scorch

[0095] Table 2 shows the comparison of Mooney scorch and Mooney viscosity of the four groups of rubber samples.

[0096] Table 2

[0097]

[0098] The t5~t35 values ​​of the Mooney scorch test represent the time it takes for the Mooney minimum to rise by 5~35 Mooney values.

[0099] according to Figure 1 The Mooney viscosity comparison bar chart and Table 2 show the test results. The Mooney viscosities of samples 2#, 3#, and 4# using organic zinc activator were all lower than those of the control sample 1# using conventional zinc oxide. Specifically, at the same addition amount, the Mooney viscosity of sample 2# was reduced by approximately 3.25 units compared to sample 1#. The results for samples 2# to 4# show that the Mooney viscosity gradually increased with decreasing organic zinc dosage, but remained lower than the control group.

[0100] according to Figure 2 According to the Mooney-time curves and Table 2, in the Mooney scorch test at 120℃, the curves of all organic zinc samples (2#, 3#, 4#) reached the test endpoint (increasing by 35 Mooney values) before approximately 25 minutes, while the curve of the zinc oxide control group (1#) lasted until 35 minutes. The organic zinc samples were significantly shorter than the control group, indicating that their vulcanization start time was earlier and the scorch time was significantly shortened, which has a certain impact on the processing safety performance of the rubber compound.

[0101] 6.3.2 Vulcanization characteristics

[0102] The test results of the vulcanization characteristics of the four groups of samples are shown in Table 3.

[0103] Table 3

[0104]

[0105] From Table 3 and Figure 3 It can be seen that the minimum torque (ML) of the samples using the organic zinc activator (2#, 3#, 4#) is similar to that of the control group (1#), while the maximum torque (MH) is significantly higher than that of the control group, indicating an improved degree of sulfidation. Meanwhile, the scorch time (t10) and positive sulfidation time (t90) of the organic zinc samples are significantly shorter than those of the control group, indicating a faster sulfidation rate. Specifically, the t90 of the organic zinc samples is approximately 10 minutes shorter than that of the control group.

[0106] In the vulcanization curves, the torque of all samples initially increased and then leveled off with increasing vulcanization time. The equilibrium torque of the control group (1#) was approximately 15 dN·m, while the equilibrium torque of the organic zinc samples (2#, 3#, and 4#) was approximately 20 dN·m, and the curves remained stable after reaching equilibrium. Variations in the amount of organic zinc (from 4.8 phr to 8.0 phr) had little effect on the vulcanization characteristic parameters.

[0107] The pattern of scorch time t10 measured by the vulcanizer in Table 3 is consistent with the scorch time measured by Mooney scorch in Table 2.

[0108] The results showed that organic zinc shortened the scorch time during NR vulcanization by approximately 50 seconds, and slightly advanced the sulfur initiation time. The addition of organic zinc accelerated the torque increase rate during NR vulcanization, resulting in a significant increase in the equilibrium torque after vulcanization. However, with further extension of the vulcanization time, the torque showed a decreasing trend. This indicates that while organic zinc can improve the vulcanization speed and degree of NR, it is crucial to control the vulcanization time to avoid potential performance degradation due to over-vulcanization.

[0109] 6.3.3 Density, hardness, resilience, and volumetric wear

[0110] The vulcanized rubber density, hardness, resilience, and volumetric abrasion of the four rubber samples are shown in Table 4.

[0111] Table 4

[0112]

[0113] According to the data in Table 4 and the corresponding graphs, we can see that:

[0114] like Figure 4 As shown, compared with the sample with zinc oxide activator (1#), the density of NR vulcanizate was reduced after adding organic zinc activator (2#, 3#, 4#), but the amount of organic zinc added was small, so the reduction in density was limited.

[0115] like Figure 5 As shown, the two types of organic zinc enhance the crosslinking degree of NR vulcanizate, resulting in a significant increase in the hardness of the vulcanizate. The effects of 4.8 phr and 8 phr organic zinc dosages on the NR hardness are comparable, remaining around 65 degrees.

[0116] like Figure 6 As shown, compared to zinc oxide, the addition of organic zinc resulted in a decrease in the resilience of the vulcanizate, with an impact rebound reduction of 4%. Figure 7 As shown, increasing the hardness of the vulcanizate is more beneficial to its wear resistance.

[0117] 6.3.4 Tensile and tear properties

[0118] The tensile and tear properties of the vulcanized rubber of the four groups of rubber samples are shown in Table 5.

[0119] Table 5

[0120]

[0121] From Table 5 and Figure 8It can be seen that, compared with the rubber sample (1#) with zinc oxide activator, the addition of organic zinc in the other three groups has a greater effect on the degree of vulcanization of NR vulcanizates, resulting in an increase in the tensile stress at each level of the NR vulcanizates, a slight decrease in the tensile elongation, and little change in the tensile strength. Overall, organic zinc and zinc oxide have a comparable effect on improving the tensile properties of NR.

[0122] In terms of tear performance, the addition of organic zinc improves the tear strength of NR, and the tear strength gradually increases with the increase of organic zinc dosage.

[0123] 6.3.5 Damp heat aging performance test

[0124] The results of the physical and mechanical properties of the four groups of rubber vulcanizates after wet heat aging are shown in Table 6.

[0125] Table 6

[0126]

[0127] After 72 hours of damp heat aging at 40℃ and 93% relative humidity, the hardness of the vulcanized rubber was generally improved, with an increase of about 2 degrees.

[0128] like Figure 9 As shown, after hygrothermal aging, samples (2#, 3#, and 4#) with added organic zinc activator showed an increase in tensile strength and elongation, except for sample 2# which showed a slight decrease in tensile strength. Compared to sample 1# with added zinc oxide activator, the addition of organic zinc still increased the stress at a constant elongation under small deformations, but the tensile strength and breaking productivity remained comparable. With the addition of organic zinc, the performance changes of the samples before and after hygrothermal aging decreased continuously; the change rates of tensile strength and elongation of sample 2# after aging were only -0.9% and 2.7%, respectively.

[0129] 6.3.6 Wire Pull-out Performance Test

[0130] The steel wire extraction performance of the vulcanized rubber samples of the four groups is shown in Table 7.

[0131] Table 7

[0132]

[0133] From Table 7 and Figure 10 It can be seen that, in terms of wire extraction performance, compared with the control group (1#) with added zinc oxide, the maximum wire extraction force of the samples (2#, 3#, 4#) using organic zinc activator all decreased.

[0134] 6.3.7 Compression fatigue heat generation properties

[0135] The test results of the compression fatigue heat generation performance of the four groups of samples are shown in Table 8.

[0136] Table 8

[0137]

[0138] As shown in Table 8, compared with the control group (1#) using conventional zinc oxide, the samples (2#, 3#, and 4#) using organic zinc activator exhibited higher final fatigue temperature rise and greater compression set during compression fatigue. This indicates that, under the experimental conditions, replacing zinc oxide with organic zinc leads to a decrease in the compression fatigue heat generation performance of NR vulcanizates.

[0139] However, as Figure 11 , Figure 12 As shown in Table 8, when comparing samples within the organic zinc group, from 4.8 phr for #4 to 8.0 phr for #2, the final fatigue temperature rise and compression set both showed a decreasing trend with increasing organic zinc dosage. This indicates that in systems using organic zinc as an activator, appropriately increasing its dosage helps improve the compression fatigue properties of vulcanizates.

[0140] 6.3.8 Flexural cracking test

[0141] The following criteria were used to rate four groups of rubber samples after a certain number of flexing cycles.

[0142] Grade 1: The sample shows visible "pinhole"-like cracks, and the number of these cracks does not exceed 10 (including 10).

[0143] Level 2: The number of the above-mentioned cracks exceeds 10, or although there are fewer than 10, one or more of the cracks have expanded beyond the "needle point" stage. The crack depth is very shallow and has a noticeable length, but the length is still less than 0.5 mm.

[0144] Grade 3: One or more cracks expand into obvious cracks, with a noticeable length and a small depth, the length being greater than 0.5 mm but less than 1 mm.

[0145] Grade 4: The length of the largest crack is greater than 1 mm but less than 1.5 mm.

[0146] Grade 5: The length of the largest crack is greater than 1.5mm and less than 3.0mm.

[0147] Grade 6: The length of the largest crack is greater than 3.0 mm.

[0148] like Figure 13As shown, compared with the control group (No. 1) using zinc oxide, the samples (No. 2, No. 3, and No. 4) using organic zinc activator exhibited fewer crack initiations and slower crack propagation rates during flexure. This difference became more pronounced when the number of flexure cycles reached 100,000, with sample No. 2, which had an organic zinc addition of 8.0 phr, showing the slowest crack propagation rate.

[0149] The above embodiments are merely illustrative of the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solutions based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A rubber activator, characterized by, The rubber activator comprises the following raw materials in percentage by weight: organic zinc compound: 20-80wt%; activator complex salt: 80-20wt%; The organic zinc compound is a zinc salt of aromatic compound or a zinc salt of aliphatic compound; the zinc salt of aromatic compound and the zinc salt of aliphatic compound contain one or more carboxyl groups; The activator complex salt comprises one or more of inorganic zinc compound, aromatic group-containing organic acid compound, straight-chain aliphatic organic acid compound and double-bond-containing organic acid compound.

2. The rubber activator of claim 1, wherein, The zinc salt of aromatic compound comprises one or more of zinc benzoate, zinc salicylate, zinc p-aminobenzoate and zinc naphthoate; the zinc salt of aliphatic compound comprises one or more of zinc acetate, zinc stearate, zinc oleate, zinc propionate and zinc adipate.

3. The rubber activator of claim 1, wherein, The inorganic zinc compound comprises one or more of zinc oxide, zinc sulfate, zinc chloride, zinc nitrate, basic zinc carbonate, zinc powder, zinc phosphate and zinc sulfite.

4. The rubber activator of claim 1, wherein, The aromatic group-containing organic acid compound comprises one or more of salicylic acid, cinnamic acid, phthalic acid and terephthalic acid.

5. The rubber activator of claim 1, wherein, The straight-chain aliphatic organic acid compound comprises one or more of formic acid, acetic acid, stearic acid, oleic acid and linoleic acid.

6. The rubber activator of claim 1, wherein, The double-bond-containing organic acid compound comprises one or more of maleic acid, itaconic acid and sorbic acid.

7. A process for the preparation of a rubber activator as claimed in any one of claims 1 to 6, characterized in that, The method comprises the following steps: Step 1: synthesis of organic zinc compound; Mixing the organic acid or organic anhydride with zinc oxide in a molar ratio of 1:1-4:1, adding solvent A, placing in an ice water bath to start stirring to cool, and ultrasonic treatment for 10-3h, then warming to 50-80℃ for 30min-3h, drying at 80-130℃ for 1-12h after the reaction is completed to obtain the organic zinc compound; Step 2: preparation of activator complex salt; Mixing at least one organic acid with metal oxide, adding solvent B, stirring at room temperature and ultrasonic treatment for 10-30min, reacting at 50-80℃ for 30min-2h, drying at 90-120℃ for 8-12h after the reaction is completed to obtain the activator complex salt; Step 3: mixing; Mixing the organic zinc compound obtained in step 1 with the activator complex salt obtained in step 2 in a predetermined percentage by weight, mixing, drying, grinding and passing through a 350-mesh sieve to obtain the rubber activator.

8. The production method according to claim 7, characterized by, In step 1, the solvent A comprises one or more of water, ethanol, methanol, dichloromethane, petroleum ether, ethyl acetate, n-propanol, n-butanol, isobutanol and acetonitrile; In step 2, the solvent B comprises one or more of water, n-butanol and ethyl acetate.

9. The preparation method according to claim 7, characterized in that, In step 1, the organic acid comprises one or more of cinnamic acid, lauric acid, salicylic acid, succinic acid and itaconic acid; the organic anhydride comprises one or more of acetic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride and pyromellitic dianhydride. In step 2, the organic acid includes one or more of sorbic acid, citric acid, dipicolinic acid, and oleic acid; and the metal oxide includes one or more of sodium oxide, calcium oxide, potassium oxide, and magnesium oxide.

10. A rubber, characterized by, The rubber activator as claimed in any one of claims 1 to 6.

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