Anti-chip carcass compound composition for giant earthmover tire and method for preparing the same

Abstract

The present application relates to the technical field of rubber, in particular to a kind of giant engineering machinery tire anti-split body rubber composition and preparation method thereof. With 100 parts by weight of natural rubber component as benchmark, further comprising the following components: natural rubber 100 parts, carbon black 40-50 parts, zinc oxide 6-8 parts, cobalt salt 0.2-0.4 parts, antioxidant 2246 0.5-1 part, antioxidant S-TMQ 0.2-1.0 parts, N,N'-4,4'-diphenyl methane bismaleimide 0.5-1.5 parts, insoluble sulfur 8-12 parts, accelerator 0.3-0.7 parts, anti-scorching agent 0.05-0.15 parts. The present application solves the shortcomings of lower adhesive property of body rubber and insufficient anti-splitting ability of existing technology under harsh road conditions and hot and humid, steam, salt water environment, greatly reduces the occurrence probability of body delamination and bead bulging under hot and humid environment in Southeast Asia, improves the anti-splitting ability of body rubber, and ensures the service life of giant tire under high load operation.

Description

Technical Field

[0001] This invention relates to the field of rubber technology, specifically to a crack-resistant tire carcass composition for giant engineering machinery tires and its preparation method. Background Technology

[0002] As is well known, giant construction machinery tires have extremely high requirements for technical design. Improving the durability of 57-inch and larger products has become the main research direction for super-large tires. The tire carcass bears most of the tire's stress. When the tire deforms, a large amount of heat is generated due to hysteresis loss. Therefore, the tire carcass rubber compound is required to have characteristics such as heat resistance, fatigue resistance, crack and crack growth resistance, good initial adhesion with steel cord, and high adhesion retention rate after aging and corrosion. This is to reduce the probability of tire carcass delamination and bead bulging in the hot and humid environment of Southeast Asia and ensure the service life of giant tires under high load operation. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a crack-resistant carcass rubber composition for giant engineering machinery tires and its preparation method. This invention improves upon the previous formulation design, which, due to the high cobalt salt content, promoted the formation of a large amount of inactive copper sulfide and accelerated rubber aging, as well as the effects on adhesion and tensile strength after steam and salt water aging, and thermal aging. It also solves the shortcomings of the prior art, such as low adhesion performance and insufficient crack resistance of the carcass rubber composition under harsh road conditions and in humid, hot, steam, and salt water environments, thereby improving the durability of the tire.

[0004] The technical solution adopted by the present invention to solve the above-mentioned technical problems is: a crack-resistant tire carcass composition for giant engineering machinery tires, characterized in that, based on 100 parts by weight of natural rubber component, it further comprises the following components: 100 parts of natural rubber, 40-50 parts of carbon black, 6-8 parts of zinc oxide, 0.2-0.4 parts of cobalt salt, 0.5-1 parts of antioxidant 2246, 0.2-1.0 parts of antioxidant S-TMQ, 0.5-1.5 parts of N,N'-4,4'-diphenylmethane bismaleimide, 8-12 parts of insoluble sulfur, 0.3-0.7 parts of accelerator, and 0.05-0.15 parts of scorch inhibitor.

[0005] The natural rubber mentioned is Thai No. 1 or Thai No. 3 smoked sheet rubber.

[0006] The carbon black described is a low-structure, high-abrasion-resistant carbon black.

[0007] The cobalt salt is preferably cobalt borate, cobalt stearate, or cobalt decanoate with a content of 14.2%.

[0008] The insoluble sulfur mentioned is HDOT20-80 rubber predispersed masterbatch.

[0009] The accelerator mentioned is sulfenamide accelerator DZ.

[0010] The anti-scorching agent is pre-dispersed masterbatch CTP-80.

[0011] A method for preparing a crack-resistant carcass rubber compound composition for giant engineering machinery tires, characterized by comprising the following steps:

[0012] A mixing process:

[0013] Start the internal mixer with a ZZ2 rotor. Set the rotor speed to 50-60 rpm. Add No. 3 smoked sheet plasticizer and carbon black, and mix for 30-40 seconds. Then add zinc oxide, stearic acid, resin, cobalt salt, antioxidant and other small materials and continue mixing until 130℃. Adjust the speed to 40-50 rpm and perform lifting and pressing every 40 seconds. When the rubber compound temperature reaches 160℃, discharge the rubber.

[0014] First settling: Cool the mixed rubber compound to room temperature;

[0015] Two-stage mixing:

[0016] Mix a section of masterbatch at 40-50 rpm, and lift and press the mixture every 40 seconds. When the temperature of the rubber compound reaches 140-145℃, discharge the rubber.

[0017] Second settling: Cool the rubber compound after the second stage of mixing to room temperature;

[0018] Three-stage mixing:

[0019] The two-stage masterbatch is mixed at a speed of 40-50 rpm, and the mixture is lifted and pressed every 40 seconds. When the temperature of the rubber compound reaches 135-140℃, the rubber is discharged.

[0020] Third settling: Cool the three-stage mixed rubber compound to room temperature;

[0021] Final Refinement:

[0022] Start the internal mixer with a ZZ2 rotor. Set the internal mixer rotor speed to 16-20 rpm. Add the first stage of masterbatch, insoluble sulfur, accelerator, zinc oxide and anti-scorching agent and mix for 140-240 seconds, with two intermediate lifting and pressing cycles. The rubber discharge temperature is 90-105℃.

[0023] The beneficial effects of this invention are that it solves the shortcomings of existing technologies in terms of low adhesion performance of tire carcass rubber and insufficient crack resistance under harsh road conditions and humid, hot, steam, and salt water environments. It greatly reduces the probability of tire carcass delamination and bead bulging in humid and hot environments in Southeast Asia, improves the crack resistance of tire carcass rubber, and ensures the service life of giant tires under high load operation. Detailed Implementation

[0024] The present invention will be further described below with reference to embodiments:

[0025] The specific embodiments and comparative examples of the present invention, as well as the formulation and physical properties of the anti-cracking carcass rubber, are shown in Tables 1 and 2, respectively:

[0026] Table 1: The formulation table of the invention composition is as follows (the unit of each raw material content is: parts by weight):

[0027]

[0028] The preparation methods of the anti-cracking carcass rubber compositions in the examples and comparative examples include the following steps:

[0029] A mixing process:

[0030] Start the internal mixer with a ZZ2 rotor. Set the rotor speed to 50-60 rpm. Add No. 3 smoked sheet plasticizer and carbon black, and mix for 30-40 seconds. Then add zinc oxide, stearic acid, resin, cobalt salt, antioxidant and other small materials and continue mixing until 130℃. Adjust the speed to 40-50 rpm and perform lifting and pressing every 40 seconds. When the rubber compound temperature reaches 160℃, discharge the rubber.

[0031] First settling: Cool the mixed rubber compound to room temperature;

[0032] Two-stage mixing:

[0033] Mix a section of masterbatch at 40-50 rpm, and lift and press the mixture every 40 seconds. When the temperature of the rubber compound reaches 140-145℃, discharge the rubber.

[0034] Second settling: Cool the rubber compound after the second stage of mixing to room temperature;

[0035] Three-stage mixing:

[0036] The two-stage masterbatch is mixed at a speed of 40-50 rpm, and the mixture is lifted and pressed every 40 seconds. When the temperature of the rubber compound reaches 135-140℃, the rubber is discharged.

[0037] Third settling: Cool the three-stage mixed rubber compound to room temperature;

[0038] Final Refinement:

[0039] Start the internal mixer with a ZZ2 rotor. Set the internal mixer rotor speed to 16-20 rpm. Add the first stage of masterbatch, insoluble sulfur, accelerator, zinc oxide and anti-scorching agent and mix for 140-240 seconds, with two intermediate lifting and pressing cycles. The rubber discharge temperature is 90-105℃.

[0040] The rubber compositions of the comparative example and the embodiment were vulcanized using a flat vulcanizing machine at 145℃ for 60 min, and their performance was tested according to national standards. The test results are shown in Table 2.

[0041] Table 2: Physical Properties of the Formulation

[0042]

[0043]

[0044] Dynamic crack propagation was tested using the DMA+NG device manufactured by Metravib, France, at a temperature of 80℃ and a frequency of 6Hz.

[0045] Comparing Examples 1 and 2 with the control example, it can be seen that the performance retention rate and crack resistance are improved after aging, but the elongation and tear strength decrease.

[0046] Comparing Examples 3 and 4 with the control example, it can be seen that when different amounts of antioxidant 2246, antioxidant S-TMQ, diphenylmethane bismaleimide, and cobalt borate are added to the anti-cracking carcass formulation, the key properties of the rubber compound are significantly improved, and other properties do not decline. Compared with the control example, Example 4 shows an increase of 16.9% in tear strength, 14.7% in D-tear strength, 8.5% in tensile volume, 21% in performance retention after aging, 22% in flexural strength, 42% in crack propagation resistance, and 17% in adhesive strength.

[0047] Conclusion: In preferred embodiment 4, the performance retention rate after aging is improved by 21%, the flexural strength is improved by 22%, the crack propagation resistance is improved by 42%, and the adhesive strength is improved by 17%.

[0048] Regardless of the type of organic cobalt salt product, cobalt ions are the primary agents promoting adhesion. Before vulcanization, rubber and brass plating in cobalt salt-containing rubber compounds only have simple contact, with a monotonous distribution of rubber, zinc oxide, and copper plating at the interface. After vulcanization, a new material layer can be observed between the rubber and brass plating, particularly a metallic vulcanization layer, namely, stoichiometric cuprous sulfide (CuXS) and zinc sulfide (ZnS). Only cuprous sulfide (CuXS) is the true adhesive layer; it can diffuse to the interface layer and form a cuprous sulfide-rubber vulcanization (CuX-S-SY-Rub) through a sulfur bridge with the rubber sulfide (Rub-SY). The chemical bonding in this process results in an adhesive reaction between the rubber and the brass plating. While there are no cobalt atoms or carboxyl groups in the adhesive bond between the rubber and the brass plating, the presence of cobalt accelerates rubber aging and negatively impacts the adhesive strength after steam aging and the tensile strength after thermal aging. This invention uses borylated cobalt and reduces the amount of cobalt salt, while simultaneously using antioxidant 2246 and anti-aging agent S-TMQ to provide better anti-aging effects on the rubber and cord. The application of diphenylmethane bismaleimide effectively prevents vulcanization reversion at high temperatures, improving the fatigue performance of the tire carcass and the performance of the rubber after aging. Increasing the amount of carbon black improves the crack resistance of the rubber compound.

[0049] The raw rubber system of this invention uses Thai No. 3 smoked sheets, which ensures a high molecular weight and a narrow molecular weight distribution, excellent wet strength, and excellent G'.

[0050] This invention utilizes antioxidant 2246 (2,2-methylenebis-4-methyl-6-tert-butylphenol), a strong bisphenol antioxidant, which acts as a hydrogen donor and reacts with peroxide free radicals to form hydroperoxides, thereby preventing hydrogen extraction from the polymer backbone. It provides protection against aging caused by oxygen or heat, and also protects against ozone decomposition of rubber under both static and dynamic conditions. It features high thermal stability, good antioxidant effect, no pollution, no blooming, and no loss of energy. It has a significant protective effect against thermo-oxidative aging, effectively inhibiting the oxidation reaction of rubber in the presence of oxygen at high temperatures. Simultaneously, it reduces flexural aging under repeated bending and deformation of tires. It also provides protection against the corrosion of variable valence metals, protecting rubber products from the effects of cobalt ions and maintaining stable performance.

[0051] This invention uses N,N'-4,4'-diphenylmethane bismaleimide, which has the characteristics of high temperature resistance, resistance to damp heat aging, improved adhesion between rubber and steel wire, and improved modulus of vulcanizate. In NR, it can promote the cross-linking reaction between rubber molecules to form a stable network structure. The maleimide active groups and unsaturated bonds it contains enable it to undergo polymerization reaction at high temperature to generate high-strength heat-resistant materials. At the same time, it can prevent vulcanization reversion at high temperature. The polysulfide bonds in the cross-linking network make the vulcanizate have good fatigue resistance. Under temperature and repeated stress, the breaking and rearrangement of polysulfide bonds alleviate the stress.

Claims

1. A crack-resistant tire carcass rubber composition for giant engineering machinery tires, characterized in that, Based on 100 parts by weight of natural rubber, it also contains the following components: 100 parts natural rubber, 40-50 parts carbon black, 6-8 parts zinc oxide, 0.2-0.4 parts cobalt salt, 0.5-1 parts antioxidant 2246, 0.2-1.0 parts antioxidant S-TMQ, 0.5-1.5 parts N,N'-4,4'-diphenylmethane bismaleimide, 8-12 parts insoluble sulfur, 0.3-0.7 parts accelerator, and 0.05-0.15 parts scorch inhibitor.

2. The anti-cracking carcass rubber composition for giant engineering machinery tires according to claim 1, wherein the natural rubber is Thai No. 1 or Thai No. 3 smoked sheet rubber.

3. The anti-cracking carcass rubber composition for giant engineering machinery tires according to claim 1, characterized in that the carbon black is a low-structure, high-abrasion-resistant carbon black.

4. The anti-cracking carcass rubber composition for giant engineering machinery tires according to claim 1, wherein the cobalt salt is preferably cobalt borate, cobalt stearate, or cobalt decanoate with a content of 14.2%.

5. The anti-cracking carcass rubber composition for giant engineering machinery tires according to claim 1, characterized in that the insoluble sulfur is rubber pre-dispersed masterbatch HDOT20-80.

6. The anti-cracking carcass rubber composition for giant engineering machinery tires according to claim 1, wherein the accelerator is sulfenamide accelerator DZ.

7. The anti-cracking carcass rubber composition for giant engineering machinery tires according to claim 1, wherein the anti-scorching agent is pre-dispersed masterbatch CTP-80.

8. A method for preparing the anti-cracking carcass rubber composition for giant engineering machinery tires as described in claim 1, characterized in that: Includes the following steps: A mixing process: Start the internal mixer with a ZZ2 rotor. Set the rotor speed to 50-60 rpm. Add No. 3 smoked sheet plasticizer and carbon black, and mix for 30-40 seconds. Then add zinc oxide, stearic acid, resin, cobalt salt, antioxidant and other small materials and continue mixing until 130℃. Adjust the speed to 40-50 rpm and perform lifting and pressing every 40 seconds. When the rubber compound temperature reaches 160℃, discharge the rubber. First settling: Cool the mixed rubber compound to room temperature; Two-stage mixing: Mix a section of masterbatch at 40-50 rpm, and lift and press the mixture every 40 seconds. When the temperature of the rubber compound reaches 140-145℃, discharge the rubber. Second settling: Cool the rubber compound after the second stage of mixing to room temperature; Three-stage mixing: The two-stage masterbatch is mixed at a speed of 40-50 rpm, and the mixture is lifted and pressed every 40 seconds. When the temperature of the rubber compound reaches 135-140℃, the rubber is discharged. Third settling: Cool the three-stage mixed rubber compound to room temperature; Final Refinement: Start the internal mixer with a ZZ2 rotor. Set the internal mixer rotor speed to 16-20 rpm. Add the first stage of masterbatch, insoluble sulfur, accelerator, zinc oxide and anti-scorching agent and mix for 140-240 seconds, with two intermediate lifting and pressing cycles. The rubber discharge temperature is 90-105℃.

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