High-elasticity oxidation-resistant rubber mixing process

Abstract

The process comprises the following steps: preparing raw materials including 30 parts of gutta-percha, 70 parts of natural rubber, 2 parts of stearic acid, 4 parts of zinc oxide, 2.5 parts of sulfur, 50 parts of carbon black, 2 parts of an anti-aging agent and 1.2 parts of an accelerant; plastifying the natural rubber by using an open mill at room temperature; plasticating the gutta-percha; uniformly mixing to obtain mixed rubber, and adding the mixed gutta-percha and natural rubber into an open mill; after the materials are uniformly mixed, the roller spacing is adjusted to be small, triangular bags are packed for 5-7 times, the roller spacing is adjusted to be 2-3 mm, sheets are discharged, standing is conducted for 12 h, a vulcanization curve of the rubber compound is measured in a vulcanizer, and the positive vulcanization time is determined according to the vulcanization curve; and S6, vulcanizing on a plate vulcanizing machine, setting the temperature of the plate vulcanizing machine to be 145 DEG C and the vulcanizing pressure to be 10MPa, and preparing the rubber compound into the oxidation-resistant vulcanized rubber. The preparation method solves the problem that the eucommia ulmoides / natural blend rubber is unstable in performance all the time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rubber preparation, in particular to a high-elasticity oxidation-resistant rubber mixing process. BACKGROUND

[0002] Mixing is a process of mixing plasticized raw rubber and compounding agents into mixed rubber by a rubber mixing machine. The purpose of mixing is two-fold: one is to improve and enhance the physical and mechanical properties and chemical properties of the rubber sample, and the other is to improve the processing and molding process to reduce the manufacturing cost of rubber products. Generally, we add various compounding agents to the raw rubber, and then mix them on an open mill or an internal mixer to uniformly disperse all the added compounding agents and ensure the best performance. The key is to uniformly disperse the various compounding agents in the raw rubber or plasticized rubber in the mixing process.

[0003] The mixing process generally includes four steps: feeding, dispersion, mixing, and plasticization. The raw rubber is mainly subjected to shearing force and tensile force in the rubber mixing machine, and under the action of the two forces, the rubber macromolecular chain is broken and fragmented, the molecular weight is reduced, and the rubber plasticity is increased. All the compounding agents added to the rubber are uniformly dispersed. This step is called the powder feeding stage. Then, under the action of mechanical force, the compounding agents mixed into the rubber are further dispersed into smaller microparticles, improving the uniformity of the mixed rubber. This step is called micro-dispersion. Mixing refers to improving the dispersion uniformity of the compounding agents in the mixed rubber, and the diameter of the particles does not change. Therefore, this step is also called macro-dispersion or simple mixing. The general process flow of mixed rubber preparation is as follows: compounding agent supplement processing, raw rubber and compounding agent weighing, mixing, and quality testing. Mixing is one of the most important production processes in rubber processing. Once the mixing is problematic, the rubber compound will exhibit various undesirable conditions such as scorching, blooming, etc., causing the calendering, extruding, coating, and vulcanization processes to be difficult to operate normally, ultimately leading to a decrease in the performance of the rubber products and rendering them unusable.

[0004] China's rubber industry has developed steadily and rapidly, and environmental protection has become the main concern of the public. In addition to enjoying the high speed and comfort of car tires, people have also made strict regulations on the energy saving and environmental protection of tires. Natural eucommia rubber, mainly composed of trans-1,4-polyisoprene, is a renewable polymer material with low dynamic heat generation, small rolling resistance, excellent wear resistance, and dynamic fatigue resistance, and has considerable application prospects in the tire industry. However, there is a problem of unstable performance of eucommia / natural rubber blend.

[0005] Based on this, the present application provides a high-elasticity oxidation-resistant rubber mixing process. SUMMARY

[0006] The present application provides a high-elasticity oxidation-resistant rubber mixing process. The problem of unstable performance of eucommia / natural rubber blend has been solved.

[0007] According to an aspect of the present disclosure, there is provided a high-elasticity oxidation-resistant rubber mixing process, comprising: S1, preparing raw materials, including: 30 parts of eucommia ulmoides gum, 70 parts of natural rubber, 2 parts of stearic acid, 4 parts of zinc oxide, 2.5 parts of sulfur, 50 parts of carbon black, 2 parts of antioxidant, and 1.2 parts of accelerator; S2, plasticizing the natural rubber at room temperature by using an open mill; S3, plasticizing the eucommia ulmoides gum; S4, obtaining the mixed rubber after uniform mixing, and adding the mixed eucommia ulmoides gum and natural rubber into the open mill; S5, adjusting the nip to 2-3 mm after mixing, discharging the sheet, and stopping for 12 h, and determining the vulcanization curve of the mixed rubber by using a vulcanization instrument, and determining the optimum vulcanization time according to the vulcanization curve; S6, vulcanizing on a flat vulcanization machine, setting the temperature of the flat vulcanization machine to 145 DEG C, and setting the vulcanization pressure to 10 MPa, and vulcanizing the mixed rubber into oxidation-resistant vulcanized rubber.

[0008] In a possible implementation, the plasticizing of the eucommia ulmoides gum comprises: after plasticizing, appropriately increasing the nip, adding carbon black and naphthenic oil, plasticizing the eucommia ulmoides gum at a roller temperature of 65 DEG C, appropriately thinning, and wrapping the roller, increasing the nip of the open mill, and mixing zinc oxide, stearic acid and other additives in sequence.

[0009] In a possible implementation, the step S4 further comprises: generating different mixing temperatures by controlling the flow of cooling water, and determining the temperature by inserting a probe thermometer into the inside of the mixed rubber after mixing.

[0010] In a possible implementation, the process further comprises: performing dynamic mechanical property testing and analysis of the blended vulcanized rubber at different mixing temperatures.

[0011] Compared with the prior art, the present application has the following beneficial effects: By using a conventional vulcanization system, the mixing temperature is changed to investigate the conventional mechanical properties and dynamic mechanical properties of the mixed vulcanized rubber. With the increase of the mixing temperature, the crystallinity of the eucommia ulmoides gum gradually decreases, the crosslinking density, tensile strength and elongation at break of the blended vulcanized rubber increase, and the hardness and modulus slightly decrease.

[0012] At different mixing temperatures, T10 and T90 increase with the increase of the mixing temperature, which indicates that appropriately reducing the mixing temperature is beneficial to reducing the vulcanization time without affecting the processing safety.

[0013] When the mixing temperature is lower than 50℃, the hindering of crystallization to the dispersion of carbon black decreases with the increase of the mixing temperature, and the sulfur in the eucommia ulmoides gum can also spread to the whole system better, so the comprehensive performance of the vulcanized rubber is relatively good when the mixing temperature is in the range of 40℃-50℃.

[0014] With the decrease of the mixing temperature, the crystallinity of the mixed rubber and the vulcanized rubber gradually increases, and the hardness of the vulcanized rubber gradually increases. The hardness of the mixed rubber decreases greatly, which is beneficial to the processing and molding. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 A high-elasticity oxidation-resistant rubber mixing process flowchart according to an embodiment of the present disclosure is shown.

[0016] Figure 2 A vulcanization property analysis (crosslinking density and Mooney viscosity change with temperature) result graph according to an embodiment of the present disclosure is shown.

[0017] Figure 3 A vulcanization property analysis (vulcanization time and torque change with time) result graph according to an embodiment of the present disclosure is shown.

[0018] Figure 4 A stress-strain curve graph of the EUG / NR blend vulcanized rubber according to an embodiment of the present disclosure is shown.

[0019] Figure 5 A stress-strain curve graph of the EUG / NR blend vulcanized rubber according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0020] Various exemplary embodiments, features, and aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. The same reference numbers in the drawings represent the same elements or similar elements. Although various aspects of the embodiments are illustrated in the drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

[0021] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations.

[0022] In addition, for the sake of brevity, a number of specific details are not described in detail herein. Those skilled in the art should understand that the present disclosure can be practiced with the elements and acts modified as to the specific details. In some instances, well-known methods, structures and techniques have not been described in detail in order to avoid obscuring the subject matter of the present disclosure.

[0023] Firstly, the test ratio is designed, and the natural rubber is plasticized by the open mill at room temperature. After plasticizing, the roller gap is appropriately increased, and carbon black and naphthenic oil are added. At the same time, the eucommia ulmoid gum is plasticized at the roller temperature of 65°C. After appropriate thinning, the roller is wrapped. The roller gap of the open mill is increased, and zinc oxide, stearic acid and other additives are mixed in sequence. After uniform mixing, the mixed eucommia ulmoid gum and natural rubber are added to the open mill. Different mixing temperatures are generated by controlling the flow of cooling water. After mixing, the temperature inside the mixed rubber is measured by inserting a probe thermometer. After mixing, the roller gap is adjusted to 2-3 mm, and the triangle is punched for 5-7 times. The mixed rubber is vulcanized on a vulcanization instrument to determine the vulcanization curve. The vulcanization time is determined according to the vulcanization curve, and then the mixed rubber is vulcanized on a flat vulcanizing machine. The temperature of the flat vulcanizing machine is set to 145°C, and the vulcanization pressure is 10 MPa. The mixed rubber is vulcanized into a standard sample.

[0024] Example 1 First, the natural rubber is plasticized on a double roller open mill (cold roller), and thinned for about 10 times. Then, the eucommia ulmoid gum is plasticized on a double roller open mill (hot roller), and thinned for about 10 times until the roller is wrapped. Then, the plasticized natural rubber is added to the wrapped eucommia ulmoid gum and mixed uniformly. The compounding agents are added in sequence, and the roller gap is adjusted to 2-3 mm after mixing. The mixed rubber is vulcanized after 12 hours of storage.

[0025] Example 2: First, the natural rubber is plasticized on a double roller open mill (cold roller), and thinned for about 10 times until the roller is wrapped. Then, the eucommia ulmoid gum is plasticized on a double roller open mill (hot roller), and thinned for about 10 times. The cooled eucommia ulmoid gum is then added to the wrapped natural rubber and uniformly blended. The compounding agents are added in sequence, and the roller gap is adjusted to 2-3 mm after mixing. The mixed rubber is vulcanized after 12 hours of storage.

[0026] Example 3: First, the natural rubber is plasticized on a double roller open mill (cold roller), and thinned for about 10 times. Carbon black and plasticizer are then added and mixed uniformly. Then, the eucommia ulmoid gum is plasticized on a double roller open mill (hot roller), and thinned for about 10 times. The compounding agents are added in sequence, and the roller gap is adjusted to 2-3 mm after mixing. The mixed rubber is cooled at room temperature after being thinned. Then, the cooled eucommia ulmoid gum is added to the wrapped natural rubber and uniformly blended. The roller gap is adjusted to 2-3 mm, and the mixed rubber is vulcanized after 12 hours of storage.

[0027] Example 4: First, plasticize the natural rubber on the two-roll open mill (cold roller), pass 10 times or so, add carbon black, plasticizer and 70% of the small material and mix evenly. Then plasticize the eucommia ulmoid gum on the two-roll open mill (hot roller), pass 10 times or so, add 30% of the small material in turn, mix evenly, then adjust the roller gap to 5-7 times of triangle bag, adjust the roller gap to 2-3 mm, after sheeting, cool at room temperature. Then add the cooled eucommia ulmoid gum compound to the natural rubber compound in the bag roller and mix evenly, adjust the roller gap to 2-3 mm, sheeting, and vulcanize after 12 hours.

[0028] Example 5: First, plasticize 40 phr of natural rubber on the two-roll open mill (cold roller), pass 10 times or so, add 40% of carbon black, plasticizer and 40% of small material and mix evenly. Then blend the eucommia ulmoid gum and 30 phr of natural rubber on the two-roll open mill (hot roller), add 60% of small material and 60% of carbon black in turn, mix evenly, then adjust the roller gap to 5-7 times of triangle bag, adjust the roller gap to 2-3 mm, after sheeting, cool at room temperature. Then add the cooled eucommia ulmoid gum compound to the natural rubber compound in the bag roller and mix evenly, adjust the roller gap to 2-3 mm, sheeting, and vulcanize after 12 hours.

[0029] Determine the curing curve of the compound by using a vulcanization instrument, determine the optimum curing time from the curing curve, and then vulcanize on a flat plate vulcanization machine. Set the temperature of the flat plate vulcanization machine to 145 ℃ and the vulcanization pressure to 10 MPa, and vulcanize the compound into a standard sample.

[0030] In one possible implementation, plasticizing the eucommia ulmoid gum includes: after plasticizing, appropriately increase the roller gap, add carbon black and naphthenic oil, and plasticize the eucommia ulmoid gum at a roller temperature of 65 ℃, appropriately pass, and then bag the roller. Increase the roller gap of the open mill, and mix zinc oxide, stearic acid and other additives in order.

[0031] In one possible implementation, step S4 further includes: generating different mixing temperatures by controlling the flow of cooling water, and measuring the temperature inside the compound with a probe thermometer after mixing is completed.

[0032] In one possible implementation, the process further includes: performing dynamic mechanical property testing and analysis of the blended vulcanized rubber at different mixing temperatures.

[0033] As Figure 2 and Figure 3As shown in the figure, it can be seen that with the increase of mixing temperature, T10 gradually increases, indicating that the increase of mixing temperature can make eucommia / natural rubber blend rubber have longer processing time, ensuring the safety of processing, and with the increase of mixing temperature, torque difference (AM = MH-ML) basically presents a slow rising trend. Analysis shows that when the amount of sulfur is certain, because the sulfur added in eucommia rubber before mixing is limited in the amorphous region of eucommia rubber by eucommia rubber crystallization, reducing its diffusion capacity, with the increase of mixing temperature, eucommia rubber crystallization gradually reduces, leading to the increase of the amount of sulfur diffused into natural rubber with the increase of mixing temperature, and then the overall crosslinking density of vulcanized rubber also increases. And the crystallization of eucommia rubber also hinders the dispersion of carbon black, with the increase of mixing temperature, the crystallization of eucommia rubber reduces, the carbon black aggregate and the "island structure" of eucommia rubber also gradually become smaller until disappear, leading to the increase of mooney viscosity and the increase of hardness of the rubber, and the decrease of processing performance. T90 increases with the increase of mixing temperature. The reason may be that the crystalline part of eucommia rubber decreases with the increase of mixing temperature, and the corresponding amorphous region increases, and the concentration of sulfur in the region decreases, so that the vulcanization time is prolonged.

[0034] Mechanical property analysis of blended vulcanized rubber at different mixing temperatures: Table 1 mechanical properties of EUG / NR vulcanized rubber , Table 1 shows that when the mixing temperature is in the range of 25-50℃, with the decrease of mixing temperature, the elongation at break and tensile strength show a downward trend; 100% modulus and 300% modulus show an upward trend. This is because under low stress, NR shows self-reinforcing, macromolecular chains are oriented and crystallized along the stress direction, with the decrease of mixing temperature, the internal eucommia rubber microcrystals also increase, so the resistance to deformation increases, and the modulus increases. Eucommia rubber molecular chain is a multiple rotational isomer, and eucommia rubber still has crystallization ability in the blended system, so under high stress, the existing microcrystals lead to the existence of two phases in the system, namely crosslinked part and uncrosslinked part, so the compatibility of eucommia rubber and natural rubber becomes poor, with the decrease of mixing temperature, the internal microcrystal content increases, stress concentration is easy to occur, and the tensile capacity decreases, resulting in the decrease of mechanical properties, that is, the decrease of tensile strength and elongation at break.

[0035] The hardness of vulcanized rubber in table 1 decreases with the increase of mixing temperature, the reason may be that the microcrystals in the system act as physical crosslinking points, limiting the movement of rubber molecular chain, thereby increasing the hardness. The hardness of the mixed rubber increases with the increase of mixing temperature, because with the increase of mixing temperature, the eucommia rubber and natural rubber gradually change from "island structure" to double continuous phase, the hardness of the rubber in "island structure" mainly depends on natural rubber, which is relatively soft, and the hardness of the rubber in double continuous phase depends on the interpenetrating network of the two matrices, which is relatively hard.

[0036] Figure 4 It can be seen that when the mixing temperature is lower than 50℃, the stress-strain curve shows an upward trend with the increase of the mixing temperature, which is due to the decrease of the internal crystalline content, the microcrystalline plays a role of physical crosslinking point, so that the hardness of the vulcanized rubber gradually decreases with the mixing temperature. The modulus gradually decreases. When the mixing temperature is higher than 50℃, the microcrystalline in the system is very small, at this time the dispersion of carbon black and the diffusion of sulfur are good, which leads to the increase of the modulus. Figure 5 is Figure 4 The local enlarged view. And under the condition of small strain, the increase of the crystalline content of eucommia rubber will make the hardness of the blended vulcanized rubber increase, and the stress is high, so a small step appears, which reflects the characteristics of elastic materials.

[0037] With the conventional vulcanization system, the conventional mechanical properties and dynamic mechanical properties of the blended vulcanized rubber are investigated by changing the mixing temperature. With the increase of the mixing temperature, the crystallinity of eucommia rubber gradually decreases, the tensile strength, crosslinking density and elongation at break of the blended vulcanized rubber increase, and the hardness and modulus decrease slightly. Under different mixing temperatures, T10 and T90 increase with the increase of the mixing temperature, which shows that under the condition of not affecting the processing safety, appropriately reducing the mixing temperature is beneficial to reducing the vulcanization time. When the mixing temperature is lower than 50℃, with the increase of the mixing temperature, the hindering of crystallization to the dispersion of carbon black decreases, and the sulfur in eucommia rubber can also diffuse better in the whole system, so when the mixing temperature is in the range of 40℃-50℃, the comprehensive performance of the vulcanized rubber is relatively good. With the decrease of the mixing temperature, the crystallinity of the mixed rubber and the vulcanized rubber gradually increases, and the hardness of the vulcanized rubber gradually increases. The hardness of the mixed rubber decreases greatly, which is beneficial to the processing and molding.

[0038] The above has described various embodiments of the present disclosure, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described embodiments. The selection of the terms used herein is intended to best explain the principles, practical applications or technical improvements in the market of the embodiments, or to enable other ordinary skilled persons in the art to understand the embodiments disclosed herein.

Claims

1. A high-elasticity oxidation-resistant rubber mixing process, characterized by, The process comprises: S1, preparing raw materials, comprising: 30 parts of eucommia rubber, 70 parts of natural rubber, 2 parts of stearic acid, 4 parts of zinc oxide, 2.5 parts of sulfur, 50 parts of carbon black, 2 parts of antioxidant, and 1.2 parts of accelerator; S2, plasticizing the natural rubber at room temperature by using an open mill; S3, plasticizing the eucommia rubber; S4, obtaining the rubber compound after uniform mixing, adding the mixed eucommia rubber and natural rubber into the open mill; S5, after mixing, adjusting the nip to 2-3mm, and out of the sheet, stopping for 12h, determining the curing curve of the rubber compound by using a curing instrument, and determining the optimum curing time according to the curing curve; S6, vulcanizing on a flat vulcanizing machine, setting the temperature of the flat vulcanizing machine to 145℃, and the vulcanizing pressure to 10MPa, and vulcanizing the rubber compound into the oxidation-resistant vulcanized rubber.

2. The high-elasticity oxidation-resistant rubber mixing process according to claim 1, wherein S3, plasticizing the eucommia rubber, comprising: after plasticizing, adjusting the nip to add carbon black and naphthenic oil, and plasticizing the eucommia rubber at a roller temperature of 65℃, thinning, and wrapping the roller, increasing the nip of the open mill, and mixing zinc oxide, stearic acid, and other additives in sequence.

3. The high-elasticity oxidation-resistant rubber mixing process according to claim 1, wherein S4, further comprising: generating different mixing temperatures by controlling the flow of cooling water, and measuring the temperature inside the rubber compound by using a probe thermometer after mixing.

4. A high elasticity oxidation resistant rubber mixing process according to claim 1, characterized in that, The process further comprises: testing and analyzing the dynamic mechanical properties of the blended vulcanized rubber at different mixing temperatures.

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