A rubber composition and a high-hardness and low-creep rubber prepared therefrom

Abstract

The present invention provides a rubber composition which, by weight parts, comprises: 100 parts of natural rubber, 4 - 7 parts of zinc oxide, 1 - 3 parts of stearic acid, 2.5 - 3.5 parts of di-n-hexyl di-n-hexyloxysilane, 2.5 - 3.5 parts of pentaerythritol tetrakis(mercapto propionate), 0.01 - 0.09 parts of bis(dihexylthiocarbamoyl) disulfide, 1 - 4 parts of microcrystalline wax, 1 - 3 parts of N-cyclodecabromohexane-N'-phenyl-p-phenylenediamine, 25 - 45 parts of carbon black, 45 - 55 parts of white carbon black, and 10 - 20 parts of nano silver-plated glass fiber. The present invention also provides a high-hardness and low-creep rubber prepared from the rubber composition and its application in a shock absorber.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer rubber, and particularly relates to a new rubber composition, a method for preparing a high-hardness and low-creep rubber therefrom, and applications of the rubber. Background Art

[0002] Rubber has many excellent properties, such as high elasticity and viscoelasticity, large elastic deformation, small elastic modulus, impact resistance, and the stiffness and hardness can be adjusted through formulation design, etc. Therefore, rubber dampers are widely used in industries such as railways, automobiles, ships, and machinery. For rubber used in dampers, especially when applied to high-speed trains, high comprehensive performance of the rubber is required. Generally, it is required that the rubber has both high hardness, high elasticity, fatigue resistance and low creep. Therefore, there have been various attempts in the prior art to design different formulations in order to obtain rubber with ideal properties. For example, the rubber composition disclosed in the invention patent application "A high-strength damping rubber" with publication number CN109749150A is: 100 parts of natural rubber, 8 - 15 parts of carbon black, 6 - 10 parts of silica, 1 - 3 parts of glycerol methacrylate, 4 - 6 parts of zinc oxide, 1 - 2 parts of stearic acid, 1 - 3 parts of 3-aminopropyltrimethoxysilane, 0.5 - 2 parts of 2-mercaptobenzothiazole, 0.5 - 0.9 parts of dibenzothiazole disulfide, 1.2 - 1.5 parts of N-cyclohexyl-2-benzothiazole sulfenamide, 10 - 20 parts of chlorosulfonated polyvinyl chloride, 4 - 6 parts of butyl benzyl phthalate, 3 - 5 parts of sodium dihydrogen pyrophosphate, 1 - 2 parts of tert-butyl hydroperoxide, 2 - 6 parts of polyvinyl alcohol, 1 - 3 parts of calcium stearate, 0.5 - 0.8 parts of sodium carboxymethyl cellulose, 0.8 - 1.5 parts of antioxidant, 1 - 2 parts of 3-aminopropyltrimethoxysilane, 2 - 3 parts of silane coupling agent KH-560. The invention patent application "A rubber composition for an upper support of an automobile damper" with publication number CN106397864A discloses that the rubber composition includes 70 - 85 parts of natural rubber; 15 - 30 parts of cis-butadiene rubber; 2 - 3.5 parts of amine antioxidant; 1 - 2 parts of dihydroquinoline antioxidant; 2.5 - 3.5 parts of physical antioxidant; 11 - 15 parts of activator; 3 - 5 parts of coupling agent; 40 - 65 parts of reinforcing agent; 4 - 8 parts of plasticizer; 1.5 - 2.5 parts of vulcanizing agent; 1.8 - 3 parts of accelerator. Zhao Fei et al. reported that when the blending ratio of natural rubber and cis-butadiene rubber is 40 / 60, the dosage ratio of sulfur to accelerator NOBS is 4:1.6, and the dosages of sulfur and accelerator are increased, with 3 parts of phenylenediamine antioxidant 4010NA, 1 part of zinc oxide, and N330 as the reinforcing agent, the hardness of the prepared vulcanized rubber can reach 80±1 on the Shore A scale, the tensile strength is not less than 13 Mpa, the elongation at break is not less than 500%, and the number of flexing cycles at the first crack is at least 800,000 times (Zhao Fei, et al. Influence of formulation factors on the dynamic flexing performance of high-hardness rubber [J]. World Rubber Industry, 2012, 39(6): 10 - 13).

[0003] However, when designing the formula of vibration damping rubber, the phenomenon of losing one thing while gaining another often occurs. In order to obtain high hardness, some rubber formulas use hardening resins or plastics (such as high styrene, polyethylene, polypropylene, polyvinyl chloride, etc.). Due to the large creep of these raw materials, the resilience and compression permanent deformation properties are seriously affected. Some rubber formulas use the method of adding more reinforcing agents or fillers. However, this will deteriorate the physical properties, such as short rubber elongation, large fatigue heat generation, large compression permanent deformation, and short tensile fatigue life. At the same time, there are also problems such as large heat generation of the rubber, short scorch time, and unsafe processing. Some rubber formulas use the method of adding more sulfur and other vulcanizing agents. This will increase the cross-linking density, resulting in a shorter rubber elongation and poor flexural fatigue performance; in addition, due to the small bond energy of polysulfide bonds, the compression permanent deformation of this vulcanized rubber at high temperatures is also poor. Some other rubber formulations use a variety of rubbers in combination, such as natural rubber and butadiene rubber, ethylene propylene rubber, styrene butadiene rubber, chloroprene rubber, nitrile rubber, etc., which will lead to poor fatigue properties (such as heat generation performance and flex cracking performance).

[0004] Therefore, the existing rubber cannot fully meet the performance requirements of vibration damping rubber. Summary of the invention

[0005] In order to overcome the deficiencies of the prior art, the present invention provides a new rubber composition and a rubber prepared therefrom and the application of the rubber. The rubber prepared therefrom has excellent properties such as high hardness, low creep, fatigue resistance, etc., has good physical and mechanical properties and processing properties, and is particularly suitable for making high-hardness rubber shock absorbers.

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

[0007] A rubber composition, comprising, by weight:

[0008] 100 parts of natural rubber, 4-7 parts of zinc oxide, 1-3 parts of stearic acid, 2.5-3.5 parts of di-n-hexyl di-n-hexyloxysilane, 2.5-3.5 parts of pentaerythritol tetramercaptopropionate, 0.01-0.09 parts of bis(dihexylthiocarbamoyl) disulfide, 1-4 parts of microcrystalline wax, 1-3 parts of N-cyclodecabromohexane-N'-phenyl-p-phenylenediamine, 25-45 parts of carbon black, 45-55 parts of white carbon black, and 10-20 parts of nano-silver-plated glass fiber.

[0009] Preferably, the rubber composition comprises, by weight:

[0010] 100 parts of natural rubber, 5 - 6 parts of zinc oxide, 1.5 - 2.5 parts of stearic acid, 2.7 - 3.3 parts of di-n-hexyl di-n-hexyloxysilane, 2.7 - 3.3 parts of pentaerythritol tetrakis(mercapto propionate), 0.04 - 0.06 parts of bis(dihexylthiocarbamoyl) disulfide, 2 - 3 parts of microcrystalline wax, 1.7 - 2.3 parts of N-cyclodecabromohexane-N'-phenyl-p-phenylenediamine, 36 - 38 parts of carbon black, 46 - 50 parts of silica, 14 - 16 parts of nano silver-plated glass fiber.

[0011] Another object of the present invention is to provide a high-hardness and low-creep rubber, which is prepared by a conventional method in the art using the above rubber composition as a raw material.

[0012] Specifically, the high-hardness and low-creep rubber is prepared by the following method:

[0013] I. Prepare each raw material according to parts by weight;

[0014] II. Modification of silica and nano silver-plated glass fiber

[0015] Put silica and nano silver-plated glass fiber into a high-speed stirring modifier, stir and heat, then add di-n-hexyl di-n-hexyloxysilane, and continue to stir for 0.5 - 1 hour to obtain modified silica and nano silver-plated glass fiber;

[0016] III. Mixing

[0017] Add natural rubber, zinc oxide, stearic acid, microcrystalline wax and N-cyclodecabromohexane-N'-phenyl-p-phenylenediamine to an internal mixer, mix for 60 - 90 seconds, then add carbon black, the modified silica and nano silver-plated glass fiber prepared in step II, mix for 6 - 8 minutes, and finally add pentaerythritol tetrakis(mercapto propionate) and bis(dihexylthiocarbamoyl) disulfide, and mix for 60 - 90 seconds to obtain.

[0018] The third object of the present invention is to provide the application of the above high-hardness and low-creep rubber in a vibration damping device.

[0019] The vibration damping device is applied to railway trains, motor vehicles and / or the mechanical field.

[0020] In the specification of this application, the "parts by weight" of each component represents the relative weight ratio between components, rather than the actual weight. 1 part by weight can be any weight. For example, according to the actual situation, 1 part by weight can be 1 g, 5 g, 10 g, 100 g, 250 g, 500 g, 1 kg, 10 kg, and so on.

[0021] The rubber composition provided by the present invention uses carbon black, silica and nano silver-plated glass fiber together to improve hardness and can also reduce the fatigue temperature rise of the shock absorber.

[0022] In order to improve processability, silica and nano silver-plated glass fibers are modified with di-n-hexyl di-n-hexyloxysilane to enhance the interfacial bonding force between silica, nano silver-plated glass fibers and rubber, promote the dispersion of components in rubber, and achieve the effects of increasing hardness and reducing compression set.

[0023] Pentaerythritol tetrakis(mercapto propionate) and bis(dihexylthiocarbamoyl) disulfide are used in combination. Among them, bis(dihexylthiocarbamoyl) disulfide generates free radicals to promote the reaction of pentaerythritol tetrakis(mercapto propionate) with double bonds in rubber molecules, thereby endowing the rubber composition with a special crosslinked structure. This crosslinked network has the following advantages: 1) The crosslinking bond has a large bond energy and good heat resistance; 2) Good compression set and small creep; 3) Large tear strength and large tensile strength; 4) Good fatigue resistance, especially good flex fatigue and tensile fatigue performance; 5) Long crosslinking bond length between crosslinking points and large elongation at break; 6) High scorch temperature and good safety.

[0024] N-cyclodecyl bromohexane-N'-phenyl-p-phenylenediamine and microcrystalline wax are used in combination. Among them, N-cyclodecyl bromohexane-N'-phenyl-p-phenylenediamine has the effect of scavenging free radicals and anti-aging, and has good compatibility with rubber; microcrystalline wax plays a role in physical anti-aging. The two complement each other to improve the aging resistance and ozone resistance of the rubber composition of the present invention.

[0025] The rubber composition provided by the present invention has the following excellent properties and fully meets the requirements of rubber for vibration damping equipment:

[0026] 1. The hardness (Shore A) reaches 80 - 83, the elongation at break is greater than 350%, the compression set is less than 25%, the compression creep increment is less than 0.02 mm / mm, the change in static stiffness after fatigue is less than 10%, and the number of tensile fatigue fractures is greater than 100,000 times.

[0027] 2. The scorch time is up to more than 270 seconds, the processing performance is good, and the scrap rate can be effectively reduced.

[0028] 3. Good heat air aging resistance, and the retention rate after heat air aging is greater than 60%.

[0029] 4. Good ozone resistance and no ozone cracking. Specific Embodiments

[0030] The present invention will be described below with reference to specific embodiments. Those skilled in the art can understand that these embodiments are only used to illustrate the present invention and do not limit the scope of the present invention in any way.

[0031] In the following examples, the experimental methods are conventional methods unless otherwise specified. The raw materials, reagent materials, etc. used in the following examples are commercially available products unless otherwise specified. Among them, the purchase situations of some reagents and raw materials are as follows:

[0032] Natural rubber: SCR 5, product of Hainan State Farms Rubber Industry Company;

[0033] Carbon black: N330, product of Cabot Corporation.

[0034] In the following examples, the specific national standards on which the measurement methods of each performance parameter are based are as follows:

[0035] Tensile strength and elongation at break: Measured in accordance with GB / T 528;

[0036] Hardness: Measured in accordance with GB / T 531;

[0037] Compression set at 70°C for 24 hours: Measured in accordance with GB / T 7759, compression ratio 25%;

[0038] Hot air aging properties at 100°C for 72 hours: Measured in accordance with GB / T 3512;

[0039] Compression creep increment: Measured in accordance with GB / T 19242, Type A specimen, 70°C, 3 days, initial compression amount 25%;

[0040] Change rate of static stiffness before and after fatigue: Measured in accordance with TB / T 2843;

[0041] Elongation fatigue performance: Measured in accordance with GB / T 1688, frequency 5HZ, elongation ratio 2;

[0042] Ozone resistance: Measured in accordance with GB / T 7762, elongation 20%, 40°C, ozone concentration 50*10 -8 Volume fraction, relative humidity 40%-60%;

[0043] Vulcanization characteristics: Measured in accordance with GB / T 16584, temperature 150°C.

[0044] Examples 1-5 A high-hardness and low-creep rubber

[0045] The raw materials of the high-hardness and low-creep rubber in Examples 1-5 are the compositions shown in Table 1, where 1 part by weight = 1 kg.

[0046] The rubber composition is prepared into a high-hardness and low-creep rubber by the following method:

[0047] I. Prepare each component of the rubber composition according to the parts by weight shown in Table 1;

[0048] II. Modification of silica and nano silver-plated glass fiber

[0049] Put silica and nano silver-plated glass fiber into a high-speed stirring modifier, stir and heat, then add di-n-hexyl di-n-hexyloxysilane, and continue stirring for 0.5 - 1 hour to obtain modified silica and nano silver-plated glass fiber;

[0050] III. Kneading

[0051] Add natural rubber, zinc oxide, stearic acid, microcrystalline wax and N-cyclodecabromohexane-N'-phenyl-p-phenylenediamine into an internal mixer, knead for 60 - 90 seconds, then add carbon black, the modified silica and nano silver-plated glass fiber prepared in step II, knead for 6 - 8 minutes, and finally add pentaerythritol tetrakis(mercapto propionate) and bis(dihexylthiocarbamoyl) disulfide, knead for 60 - 90 seconds to obtain the product.

[0052] Comparative Example 1 - 2 A kind of rubber

[0053] The raw materials of the rubber in Comparative Example 1 - 2 are the rubber compositions shown in Table 1, where 1 part by weight = 1 kg.

[0054] Prepare the rubber in Comparative Example 1 - 2 according to the same steps as in Example 1.

[0055] Table 1 Raw material composition (parts by weight) of the rubber compositions in Examples 1 - 5 and Comparative Examples 1 - 2

[0056]

[0057] Comparative Example 3 The rubber disclosed in CN109749150A

[0058] According to the formula in Example 1 of CN109749150A (1 part = 1 kg), prepare the rubber in this comparative example by the following method:

[0059] Put natural rubber into an internal mixer, add other additives except 2-mercaptobenzothiazole, dibenzothiazole disulfide, N-cyclohexyl-2-benzothiazole sulfenamide, butyl benzyl phthalate, disodium dihydrogen pyrophosphate, carbon black and silica, knead for 60 - 90 seconds, then add carbon black and silica, and continue kneading for 6 - 8 minutes; finally add 2-mercaptobenzothiazole, dibenzothiazole disulfide, N-cyclohexyl-2-benzothiazole sulfenamide, butyl benzyl phthalate and disodium dihydrogen pyrophosphate, knead for 60 - 90 seconds to obtain the product.

[0060] Test Example 1 Performance determination of the rubbers in Examples 1 - 5 and Comparative Examples 1 - 3

[0061] The hardness (Shore A), tensile strength (MPa), elongation at break (%), compression set (%), compression creep increment (mm / mm), change rate of static stiffness after fatigue (%), number of tensile fatigue fracture times (10,000 times), elongation at break retention rate (%) after hot air aging, ozone resistance, and scorch time (seconds) of the rubbers of Examples 1-5 and Comparative Examples 1-3 were measured respectively. The measurement results are shown in Table 2.

[0062] Table 2 Measurement results of the properties of the rubbers of each example and comparative example

[0063]

[0064] The data in Table 2 show that:

[0065] The rubber prepared from the rubber composition of the present invention has better properties in all aspects than the comparative examples, especially high hardness, low creep, long scorch time, and good processing performance.

Claims

1. A rubber composition, by weight, consists of: 100 parts of natural rubber, 4 - 7 parts of zinc oxide, 1 - 3 parts of stearic acid, 2.5 - 3.5 parts of di-n-hexyl di-n-hexyloxysilane, 2.5 - 3.5 parts of pentaerythritol tetrakis(mercapto propionate), 0.01 - 0.09 parts of bis(dihexylthiocarbamoyl) disulfide, 1 - 4 parts of microcrystalline wax, 1 - 3 parts of N-cyclodecabromohexane-N'-phenyl-p-phenylenediamine, 25 - 45 parts of carbon black, 45 - 55 parts of white carbon black, 10 - 20 parts of nano silver-plated glass fiber.

2. The rubber composition according to claim 1, wherein By weight, consists of: 100 parts of natural rubber, 5 - 6 parts of zinc oxide, 1.5 - 2.5 parts of stearic acid, 2.7 - 3.3 parts of di-n-hexyl di-n-hexyloxysilane, 2.7 - 3.3 parts of pentaerythritol tetrakis(mercapto propionate), 0.04 - 0.06 parts of bis(dihexylthiocarbamoyl) disulfide, 2 - 3 parts of microcrystalline wax, 1.7 - 2.3 parts of N-cyclodecabromohexane-N'-phenyl-p-phenylenediamine, 36 - 38 parts of carbon black, 46 - 50 parts of white carbon black, 14 - 16 parts of nano silver-plated glass fiber.

3. A high-hardness and low-creep rubber, using the rubber composition described in claim 1 or 2 as raw materials, is prepared by the following method: I. Prepare each raw material by weight. II. Modification of white carbon black and nano silver-plated glass fiber Place white carbon black and nano silver-plated glass fiber into a high-speed stirring modifier, stir and heat, then add di-n-hexyl di-n-hexyloxysilane, and continue to stir for 0.5 - 1 hour to obtain modified white carbon black and nano silver-plated glass fiber. III. Mixing Add natural rubber, zinc oxide, stearic acid, microcrystalline wax, and N-cyclodecabromohexane-N'-phenyl-p-phenylenediamine into an internal mixer, mix for 60 - 90 seconds, then add carbon black, the modified white carbon black and nano silver-plated glass fiber prepared in step II, mix for 6 - 8 minutes, and finally add pentaerythritol tetrakis(mercapto propionate) and bis(dihexylthiocarbamoyl) disulfide, and mix for 60 - 90 seconds to obtain.

4. Application of the high-hardness and low-creep rubber described in claim 3 in a damping device.

5. The application according to claim 4, wherein The damping device is applied to railway trains, motor vehicles, and / or the mechanical field.

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