Controllable cross-linked graphene-modified natural rubber with high vulcanization efficiency and low heat generation and its streamlined preparation process by aqueous phase synergistic coagulation

Abstract

The present invention belongs to the technical field of graphene and functional rubber composite materials, specifically a controllable cross-linked graphene-modified natural rubber with high vulcanization efficiency and low heat generation and its water phase synergistic coagulation streamlined preparation process. The nano-sulfur / vulcanization accelerator @ graphene oxide that simultaneously loads nano-sulfur and vulcanization accelerator on the surface of the present invention improves the dispersibility of the vulcanizer and the vulcanization accelerator and the contact area with the natural rubber matrix to improve the vulcanization efficiency and the cross-linking density of the obtained vulcanized rubber and the uniformity of the cross-linking network while controlling the cross-linking site, and by reducing the friction between the filler-filler and the filler-matrix, the natural rubber vulcanized rubber is given low heat generation performance. The nano-sulfur / vulcanization accelerator @ graphene oxide that simultaneously loads nano-sulfur and vulcanization accelerator on the surface prepared by the water phase synergistic coagulation streamlined process of the present invention has the advantages of effectively improving the vulcanization efficiency of natural rubber and giving the vulcanized rubber low heat generation performance.

Description

Technical Field

[0001] The invention belongs to the technical field of graphene and functional rubber composite materials, and specifically relates to a controllably cross-linked graphene-modified natural rubber with high vulcanization efficiency and low heat generation, and a water-phase coordinated coagulation and simplified preparation process thereof. Background Art

[0002] With the rapid development of modern three-dimensional transportation, the key role of rubber composites has become increasingly prominent. Natural rubber (NR) is widely used in many fields such as tires, conveyor belts and rubber gloves used in transportation, aerospace, agriculture and daily life due to its excellent mechanical properties, tear resistance and elasticity. However, despite years of research and application, extending the service life of NR and improving its stability in use remains a challenging task. As a poor conductor of heat, thermal damage is the main factor causing NR's performance degradation that cannot be ignored. Therefore, reducing the heat generation of rubber products has become one of the most important challenges. By developing new rubber composites and their preparation technologies to reduce heat generation, not only can the stability and durability of rubber products be improved, but other properties can also be further optimized.

[0003] In addition, the body strength of NR is low and cannot meet most application scenarios. Therefore, it is crucial to improve the strength to expand the application field and scope. Adding nanofillers with small particle size and large specific surface area has become one of the most effective and convenient ways to improve the strength of NR. Among them, clay, carbon black, carbon nanotubes, graphene and its derivatives are ideal fillers, especially graphene derivatives - graphene oxide (GO), which has been widely used due to its excellent high thermal conductivity, electrical conductivity and mechanical strength, and the rich oxygen-containing functional groups on the surface provide more possibilities for NR performance improvement and function endowment.

[0004] Mechanical damage, fatigue damage and thermal damage during rolling of tires molded with nanofillers reinforced NR are the main reasons for the reduction in their service life. Among them, reducing the heat generation of NR is particularly important. From the perspective of the material itself, the heat generation of rubber mainly comes from the friction between filler-filler, filler-matrix and matrix-matrix. Therefore, reducing friction plays a vital role in reducing heat generation and thus extending the service life of rubber tires. The friction of rubber composites is mainly related to two factors: the dispersion of fillers and the interfacial interaction between rubber and fillers. The better the dispersion and the stronger the interfacial interaction between fillers and rubber, the less friction and the lower the heat generation. Summary of the invention

[0005] In order to improve the low heat generation performance of NR and thereby extend the service life of the tire by reducing the thermal damage under the driving condition of the natural rubber tire, the present invention provides a controllable cross-linked graphene-modified natural rubber with high vulcanization efficiency and low heat generation and a streamlined preparation process of the water phase synergistic coagulation thereof.

[0006] The present invention is realized by the following technical scheme: a controllably cross-linked graphene-modified natural rubber with high vulcanization efficiency and low heat generation, characterized in that it comprises natural rubber, rubber additives, reinforcing fillers and nano-sulfur / vulcanization accelerator@graphene oxide on the surface of which nano-sulfur and vulcanization accelerator are simultaneously loaded; the natural rubber is 100 parts by mass, the rubber additive is 8 to 15 parts by mass, the reinforcing filler is 30 to 90 parts by mass, and the nano-sulfur / vulcanization accelerator@graphene oxide is such that the graphene oxide contained in it reaches 0.4 to 2 parts by mass;

[0007] The mass ratio of nanosulfur: vulcanization accelerator: graphene oxide in the nanosulfur / vulcanization accelerator@graphene oxide is 3-7:3-7:10; the nanosulfur / vulcanization accelerator@graphene oxide improves the dispersibility of the vulcanizer and the vulcanization accelerator and the contact area with the natural rubber matrix, improves the vulcanization efficiency and the crosslinking density of the obtained vulcanized rubber and the uniformity of the crosslinking network, and controls the crosslinking sites at the same time, and gives the natural rubber vulcanized rubber low heat generation performance by reducing the friction between fillers and fillers and fillers and matrix.

[0008] As a further improvement of the technical solution of the present invention, the rubber additives include an antioxidant, an antioxidant, a vulcanization accelerator, an activator, and a softener, and the mass ratio of the antioxidant, antioxidant, vulcanization accelerator, activator, and softener is 2:2:1.3 to 1.85:5:2.

[0009] As a further improvement of the technical solution of the present invention, the vulcanization accelerator is at least one of N-tert-butyl-2-benzothiazole sulfenamide, N-cyclohexyl-2-benzothiazole sulfenamide and N-(diethylene oxide)-2-benzothiazole sulfenamide; the antioxidant is at least one of 2,6-di-tert-butyl-4-methylphenol, 2,2,4-trimethyl-1,2-dihydroquinoline polymer and 2-thiol benzoimidazole; the antioxidant is at least one of N-(1-methylisopentyl)-N'-phenyl-p-phenylenediamine and p-phenylaniline or dilauryl dipropionate sulfide; the activator is at least one of zinc gluconate, zinc oxide and magnesium oxide; the softener is at least one of stearic acid, dibutyl titanate and dioctyl adipate; the vulcanizing agent is sulfur; and the reinforcing filler is carbon black.

[0010] A water-phase synergistic coagulation streamlined preparation process of controllably cross-linked graphene-modified natural rubber with high vulcanization efficiency and low heat generation comprises the following steps:

[0011] (1) Acidic solution and sulfur source solution are added to the graphene oxide aqueous dispersion at a temperature T 1 Lower reaction time t 1 , to obtain a nano-sulfur-loaded graphene oxide aqueous dispersion; then deionized water and an ethanol solution of a vulcanization accelerator are added in sequence, and the temperature is T2 Lower reaction time t 2 , dispersed in deionized water after centrifugation to obtain nano-sulfur / vulcanization accelerator@graphene oxide aqueous dispersion;

[0012] (2) adding deionized water to natural rubber latex, mixing well, then adding the nano-sulfur / vulcanization accelerator @ graphene oxide aqueous dispersion obtained in step (1), mixing well, then adding a flocculant, so that the negative charge repulsion between particles that keeps the rubber latex stable is reduced and flocculation occurs, and the rubber particles with the damaged protective layer and the nano-sulfur / vulcanization accelerator @ graphene oxide are mutually adsorbed by the force to form bound particles; the bound particles and the rubber particles are orderly aggregated in the aqueous phase and precipitated out in coordination; the obtained raw rubber is washed with water for multiple times and then dried after dehydration to obtain a nano-sulfur / vulcanization accelerator @ graphene oxide modified natural rubber masterbatch;

[0013] (3) adding deionized water to natural rubber latex, mixing well, and then adding graphene oxide aqueous dispersion, mixing well, and then adding flocculant, because the negative charge repulsion between particles that keeps the rubber latex stable is reduced, flocculation occurs, and the rubber particles with the damaged protective layer and the graphene oxide will be adsorbed to each other through the force to form combined particles; the combined particles and rubber particles are orderly aggregated in the water phase and precipitated out in coordination; the obtained raw rubber is washed with water for multiple times and then dried after dehydration, so as to obtain the graphene oxide modified natural rubber masterbatch;

[0014] (4) placing the natural rubber block or the graphene-modified natural rubber masterbatch obtained in step (3) in an internal mixer at a temperature T 3 Lower mixing time t 3 The rubber material is discharged, and rubber additives and reinforcing fillers are added during the process; the discharged rubber material is cooled to room temperature and then heated on the open mill at a temperature of T 4 Next refining time t 4 During this period, a vulcanizing agent and the nano-sulfur / vulcanization accelerator @ graphene oxide modified natural rubber masterbatch obtained in step (2) are added, mixed evenly, and thinly passed until the rubber material has no bubbles to obtain a mixed rubber; the mixed rubber is heated at a temperature T 5 Placement time t 5 After the mold temperature T 6 And the vulcanization time t under a certain pressure 6 , a controllably cross-linked graphene-modified natural rubber with high vulcanization efficiency and low heat generation is obtained.

[0015] As a further improvement of the technical solution of the present invention, in step (1), at least one of dilute hydrochloric acid, ascorbic acid, formic acid, citric acid and sulfuric acid is used to prepare the acidic solution; at least one of sodium sulfate, sodium thiosulfate, sodium persulfate and sodium thiosulfate pentahydrate is used to prepare the sulfur source solution; the reaction temperature T for preparing the nano-sulfur-loaded graphene oxide aqueous dispersion is 1= room temperature ~ 50 ° C, reaction time t 1 = 1 to 5 h; Reaction temperature T for preparing nano-sulfur / vulcanization accelerator @ graphene oxide aqueous dispersion 2 =50~90℃, reaction time t 2 =1~4h.

[0016] As a further improvement of the technical solution of the present invention, in step (1), the concentration of the graphene oxide aqueous dispersion is 1 to 10 mg / mL; the concentration of the acidic solution is 0.01 to 0.1 mol / L; the concentration of the sulfur source solution is 100 to 200 mg / mL; the solubility of the ethanol solution of the vulcanization accelerator is 20 to 60 mg / mL; and the concentration of the nano-sulfur / vulcanization accelerator@graphene oxide aqueous dispersion is 1 to 10 mg / mL.

[0017] As a further improvement of the technical solution of the present invention, in steps (2) and (3), the amount of deionized water added is such that the concentration of the prepared natural rubber latex emulsion is 15 to 35 wt.%.

[0018] As a further improvement of the technical solution of the present invention, in step (2), the flocculant is selected from at least one of calcium chloride, formic acid, hydrochloric acid, sodium chloride and potassium chloride solutions; and the drying temperature of the raw rubber is 40-80°C.

[0019] As a further improvement of the technical solution of the present invention, in step (3), the concentration of the added graphene oxide aqueous dispersion is 1 to 10 mg / mL; the flocculant is selected from at least one of calcium chloride, formic acid, hydrochloric acid, sodium chloride and potassium chloride solutions; and the drying temperature of the raw rubber is 40 to 80°C.

[0020] As a further improvement of the technical solution of the present invention, in step (4), T 3 =100~120℃,t 3 =10~16min; T 4 =50~70℃,t 4 =10~15min; T 5 = room temperature, t 5 =20~30h; T 6 =140~160℃, vulcanization pressure 10~20MPa, t 6 =5~15min.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] ① The nanosulfur / vulcanization accelerator@graphene oxide prepared by the simplified process of the present invention, which simultaneously loads nanosulfur and vulcanization accelerator on the surface, can undergo cross-linking reaction with rubber macromolecules, and has the advantages of effectively improving the vulcanization efficiency of NR and improving the low heat generation of vulcanized rubber.

[0023] ② The nano-sulfur / vulcanization accelerator @ graphene oxide of the present invention improves the dispersibility of the vulcanizer and the vulcanization accelerator and the contact area with the natural rubber matrix, improves the vulcanization efficiency, the cross-linking density of the obtained vulcanized rubber and the uniformity of the cross-linking network, and controls the cross-linking sites at the same time, and gives the natural rubber vulcanized rubber low heat generation performance by reducing the friction between fillers and fillers and fillers and matrix.

[0024] ③ The preparation process of the present invention is simple, has no strict requirements, involves conventional equipment, and is easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 SEM photos of nano-sulfur@graphene oxide (a) and commercial sublimated sulfur (b) prepared in Example 1 of the present invention.

[0028] Figure 2 These are SEM photos of the brittle fracture surfaces of the modified natural rubber composite materials prepared in Examples 1 to 2 of the present invention and Comparative Examples 1 to 3.

[0029] Figure 3 It is a vulcanization curve diagram of the modified natural rubber composite material prepared in Examples 1 to 2 of the present invention and Comparative Examples 1 to 3.

[0030] Depend on Figure 1 It can be seen that in the nano-sulfur@graphene oxide particles prepared by the present invention, the in-situ deposited sulfur is of nanometer level (about 50-100 nm), while the commercial sublimated sulfur is of micrometer level (about 1-10 μm).

[0031] Depend on Figure 2 It can be seen that, compared with Comparative Examples 1 to 3, the fillers in the rubber composite materials prepared in Examples 1 to 2 of the present invention are more evenly dispersed.

[0032] Depend on Figure 3 It can be seen that compared with comparative examples 1 to 3, the curing rate of the hot curing period of examples 1 to 2 of the present invention is faster and M H -M LThe value (maximum torque value minus minimum torque value) is the largest, indicating that the nano-sulfur / vulcanization accelerator @ graphene oxide of the present invention can indeed significantly improve the crosslinking density and vulcanization efficiency of NR. DETAILED DESCRIPTION

[0033] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0034] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

[0035] The present invention provides a specific embodiment of a water-phase synergistic coagulation streamlined preparation process of a controllably cross-linked graphene-modified natural rubber with high vulcanization efficiency and low heat generation, comprising the following steps:

[0036] (1) Acidic solution and sulfur source solution are added to the graphene oxide aqueous dispersion at a temperature T 1 Lower reaction time t 1 , to obtain a nano-sulfur-loaded graphene oxide (nano-sulfur@graphene oxide) aqueous dispersion; then deionized water and an ethanol solution of a vulcanization accelerator are added in sequence, and the temperature is T 2 Lower reaction time t 2 , dispersed in deionized water after centrifugation to obtain a nano-sulfur / vulcanization accelerator @ graphene oxide aqueous dispersion; in step (1), the concentration of the graphene oxide aqueous dispersion is 1 to 10 mg / mL; the concentration of the acidic solution is 0.01 to 0.1 mol / L; the concentration of the sulfur source solution is 100 to 200 mg / mL; the solubility of the ethanol solution of the vulcanization accelerator is 20 to 60 mg / mL; the concentration of the nano-sulfur / vulcanization accelerator @ graphene oxide aqueous dispersion is 1 to 10 mg / mL.

[0037] Furthermore, in step (1), at least one of dilute hydrochloric acid, ascorbic acid, formic acid, citric acid and sulfuric acid is used to prepare the acidic solution; at least one of sodium sulfate, sodium thiosulfate, sodium persulfate and sodium thiosulfate pentahydrate is used to prepare the sulfur source solution.

[0038] Reaction temperature T for preparing aqueous dispersion of graphene oxide loaded with nano-sulfur 1 = room temperature ~ 50 ° C, reaction time t 1 = 1 to 5 h; Reaction temperature T for preparing nano-sulfur / vulcanization accelerator @ graphene oxide aqueous dispersion 2 =50~90℃, reaction time t2 =1~4h.

[0039] (2) adding deionized water to natural rubber latex, mixing well, then adding the nano-sulfur / vulcanization accelerator @ graphene oxide aqueous dispersion obtained in step (1), mixing well, then adding a flocculant, so that the negative charge repulsion between particles that keeps the rubber latex stable is reduced and flocculation occurs, and the rubber particles with the damaged protective layer and the nano-sulfur / vulcanization accelerator @ graphene oxide are mutually adsorbed by the force to form bound particles; the bound particles and the rubber particles are orderly aggregated in the aqueous phase and precipitated out in coordination; the obtained raw rubber is washed with water for multiple times and then dried after dehydration to obtain a nano-sulfur / vulcanization accelerator @ graphene oxide modified natural rubber masterbatch;

[0040] In step (2), the flocculant is selected from at least one of calcium chloride, formic acid, hydrochloric acid, sodium chloride and potassium chloride solutions; and the drying temperature of the raw rubber is 40-80°C.

[0041] (3) adding deionized water to natural rubber latex, mixing well, and then adding graphene oxide aqueous dispersion, mixing well, and then adding flocculant, because the negative charge repulsion between particles that keeps the rubber latex stable is reduced, flocculation occurs, and the rubber particles with the damaged protective layer and the graphene oxide will be adsorbed to each other through the force to form combined particles; the combined particles and rubber particles are orderly aggregated in the water phase and precipitated out in coordination; the obtained raw rubber is washed with water for multiple times and then dried after dehydration, so as to obtain the graphene oxide modified natural rubber masterbatch;

[0042] In step (3), the concentration of the added graphene oxide aqueous dispersion is 1 to 10 mg / mL; the flocculant is selected from at least one of calcium chloride, formic acid, hydrochloric acid, sodium chloride and potassium chloride solutions; and the drying temperature of the raw rubber is 40 to 80°C.

[0043] In steps (2) and (3), the amount of deionized water added is such that the concentration of the prepared natural rubber latex emulsion is 15 to 35 wt.%.

[0044] (4) placing the natural rubber block or the graphene-modified natural rubber masterbatch obtained in step (3) in an internal mixer at a temperature T 3 Lower mixing time t 3 The rubber material is discharged, and rubber additives and reinforcing fillers are added during the process; the discharged rubber material is cooled to room temperature and then heated on the open mill at a temperature of T 4 Next refining time t 4 During this period, a vulcanizing agent and the nano-sulfur / vulcanization accelerator @ graphene oxide modified natural rubber masterbatch obtained in step (2) are added, mixed evenly, and thinly passed until the rubber material has no bubbles to obtain a mixed rubber; the mixed rubber is heated at a temperature T 5 Placement time t 5 After the mold temperature T 6 And the vulcanization time t under a certain pressure6 , a controllably cross-linked graphene-modified natural rubber with high vulcanization efficiency and low heat generation is obtained.

[0045] In one embodiment provided by the present invention, in step (4), T 3 =100~120℃,t 3 =10~16min; T 4 =50~70℃,t 4 =10~15min; T 5 = room temperature, t 5 =20~30h; T 6 =140~160℃, vulcanization pressure 10~20MPa, t 6 =5~15min.

[0046] The specific embodiments of the present invention are described in detail below.

[0047] Embodiment 1:

[0048] A controllable cross-linked graphene-modified natural rubber with high vulcanization efficiency and low heat generation and a streamlined preparation process thereof by aqueous phase synergistic coagulation, specifically comprising the following steps:

[0049] ① Add 0.1 mol / L hydrochloric acid and 160 mg / mL sodium thiosulfate pentahydrate solution to a 2.5 mg / mL graphene oxide aqueous dispersion, and react at room temperature (temperature 25°C) for 3 hours, wherein the volume ratio of the graphene oxide aqueous dispersion, hydrochloric acid, and sodium thiosulfate pentahydrate solution is 8:6:1; obtain nanosulfur@graphene oxide aqueous dispersion.

[0050] ② The nanosulfur @ graphene oxide aqueous dispersion prepared in step ① was formulated into 2.64 mg / mL, and then a 40 mg / mL ethanol solution of a vulcanization accelerator N-cyclohexyl-2-benzothiazolesulfonyl (CZ) was added, and the mixture was reacted at 70° C. for 2 h, wherein the volume ratio of the nanosulfur @ graphene oxide aqueous dispersion to the vulcanization accelerator CZ ethanol solution was 2:1; the mixture was centrifuged at 6000 rpm and dispersed in deionized water to obtain a 2.77 mg / mL nanosulfur / vulcanization accelerator @ graphene oxide aqueous dispersion.

[0051] ③ Deionized water is added to the natural latex emulsion to control the concentration to 30wt.%; 2.77mg / mL of the nano-sulfur / vulcanization accelerator @ graphene oxide aqueous dispersion prepared in step ② is added and mechanically stirred for 30min; 10wt% calcium chloride solution is added to flocculate the latex, wherein the volume ratio of the natural latex emulsion, the nano-sulfur / vulcanization accelerator @ graphene oxide aqueous dispersion, and the calcium chloride solution is 167:100:30; the obtained raw rubber is soaked in water and changed with water for many times, and then dried at 60°C to constant weight to obtain a nano-sulfur / vulcanization accelerator @ graphene oxide modified natural rubber masterbatch with a nano-sulfur / vulcanization accelerator @ graphene oxide content of 1.04wt%, wherein the mass ratio of nano-sulfur:vulcanization accelerator:graphene oxide is 56:52:100.

[0052] ④ Deionized water is added to the natural rubber latex emulsion to control the concentration to 30wt.%; a graphene oxide aqueous dispersion with a concentration of 5mg / mL is added and mechanically stirred for 30min; a 10wt% calcium chloride solution is added to flocculate the latex, wherein the volume ratio of the natural rubber latex emulsion, the graphene oxide aqueous dispersion and the calcium chloride solution is 167:50:30; the obtained raw rubber is soaked in water and dehydrated for multiple times, and then dried at 60°C to constant weight to obtain a graphene oxide-modified natural rubber masterbatch with 0.5wt% of graphene oxide.

[0053] ⑤ The graphene oxide modified natural rubber masterbatch prepared in step ④ with a natural rubber content of 80 phr was added to a 110° C. internal mixer and kneaded for 4 min, and then 2 phr of an antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (4020), 2 phr of an antioxidant 2,2,4-trimethyl-1,2-dihydroquinoline polymer (RD) and 1.74 phr of a vulcanization accelerator CZ were added. After kneading for 4 min, 5 phr of an activator zinc oxide, 2 phr of a softener stearic acid and 1 phr of a curing agent were added. 8phr of N330 carbon black was added, and kneaded for 4 minutes. Finally, 17phr of N330 carbon black was added, and the rubber was discharged after kneading for 4 minutes. The discharged rubber was cooled to room temperature and then kneaded on a 60℃ open mill for 10 minutes. During this period, nano-sulfur / vulcanization accelerator @ graphene oxide modified natural rubber masterbatch with a natural rubber content of 20phr and 1.72phr of sulfur were added. After being mixed evenly, the rubber was thinly passed until there were no bubbles in the rubber to obtain a mixed rubber. The mixed rubber was placed at room temperature for 24 hours and then put into a vulcanization mold. At 15MPa and 150℃, the mixture was heated to t c90 Vulcanization 6min(t c90 measured by a rubber process analyzer).

[0054] Embodiment 2:

[0055] ①~⑤ are the same as ①~⑤ of Example 1, except that 2.77 mg / mL of nano-sulfur / vulcanization accelerator@graphene oxide aqueous dispersion is replaced by 5.54 mg / mL of nano-sulfur / vulcanization accelerator@graphene oxide aqueous dispersion, and the amounts of sulfur and accelerator CZ added are 1.44 phr and 1.48 phr, respectively.

[0056] Comparative Example 1:

[0057] A preparation process for graphene oxide modified natural rubber, wherein the contents of the components in the obtained modified natural rubber composite material are exactly the same as those in Example 1 (see Table 1), specifically comprises the following steps:

[0058] ①Same as ④ in Example 1.

[0059] ② is the same as ⑤ in Example 1, except that the nano-sulfur / vulcanization accelerator @ graphene oxide modified natural rubber masterbatch in Example 1 is not added, and the addition amount of CZ and sulfur is 2phr. Specifically, the graphene oxide modified natural rubber masterbatch prepared in step ① with a natural rubber content of 100phr is added to a 110°C internal mixer and kneaded for 4 minutes, and then 2phr of antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (4020), 2phr of antioxidant 2,2,4-trimethyl-1,2-dihydroquinoline polymer (RD) and 2phr of vulcanization accelerator CZ are added. After kneading for 4 minutes, 5phr of 100mg of activator zinc oxide, 2phr of softener stearic acid and 18phr of N330 carbon black were added and kneaded for 4min, and finally 17phr of N330 carbon black was added. After kneading for 4min, the rubber was discharged; the discharged rubber was cooled to room temperature and then kneaded on a 60℃ open mill for 10min, during which 2phr of sulfur was added. After mixing evenly, the rubber was thinly passed until there were no bubbles in the rubber to obtain a rubber mix; the rubber mix was placed at room temperature for 24h and then put into a vulcanization mold. At 15MPa and 150℃, the mixture was heated to t c90 Vulcanization 7min(t c90 measured by a rubber process analyzer).

[0060] Comparative Example 2:

[0061] A preparation process of a vulcanization accelerator @ graphene oxide modified natural rubber, wherein the contents of the components in the obtained modified natural rubber composite material are exactly the same as those in Example 1 (see Table 1), specifically comprising the following steps:

[0062] ① is the same as ② in Example 1, except that the nanosulfur @ graphene oxide in Example 1 is replaced with graphene oxide. Specifically, the graphene oxide aqueous dispersion is prepared into 2.5 mg / mL, and then a 40 mg / mL ethanol solution of a vulcanization accelerator CZ is added, and the reaction is carried out at 70° C. for 2 hours, wherein the volume ratio of the graphene oxide dispersion and the accelerator CZ ethanol solution is 2:1; the dispersion is dispersed in deionized water after centrifugation at a speed of 6000 rpm to obtain a 2.64 mg / mL vulcanization accelerator @ graphene oxide aqueous dispersion.

[0063] ② is the same as ③ in Example 1, except that the nano-sulfur / vulcanization accelerator @ graphene oxide in Example 1 is replaced with vulcanization accelerator @ graphene oxide. Specifically: deionized water is added to the natural latex emulsion to control the concentration to 30wt.%; 2.64mg / mL of the vulcanization accelerator @ graphene oxide aqueous dispersion prepared in step ① is added and mechanically stirred for 30min; 10wt% calcium chloride solution is added to flocculate the latex, wherein the volume ratio of the natural latex emulsion, the vulcanization accelerator @ graphene oxide aqueous dispersion, and the calcium chloride solution is 167:100:30; the obtained raw rubber is soaked in water and changed with water for many times, and then dried at 60°C to constant weight to obtain a vulcanization accelerator @ graphene oxide modified natural rubber masterbatch.

[0064] ③Same as ④ in Example 1.

[0065] ④ is the same as ⑤ in Example 1, except that the nano-sulfur / vulcanization accelerator@graphene oxide in Example 1 is replaced with vulcanization accelerator@graphene oxide, and the amount of sulfur added is 2 phr. Specifically, 80 phr of the graphene oxide modified natural rubber masterbatch prepared in step ③ was added to a 110°C internal mixer and mixed for 4 minutes, and then 2 phr of antioxidant 4020, 2 phr of antioxidant RD and 1.72 phr of vulcanization accelerator CZ were added. After mixing for 4 minutes, 5 phr of activator zinc oxide, 2 phr of softener stearic acid and 18 phr of N330 carbon black were added, and mixed for 4 minutes. Finally, 17 phr of N330 carbon black was added, and the rubber was discharged after mixing for 4 minutes; the discharged rubber was cooled to room temperature and then mixed on a 60°C mixing mill for 10 minutes, during which a vulcanization accelerator @graphene oxide modified natural rubber masterbatch with a natural rubber content of 20 phr and 2 phr of sulfur were added, mixed evenly, and thinned until the rubber was free of bubbles to obtain a mixed rubber; the mixed rubber was placed at room temperature for 24 hours and then put into a vulcanization mold, and at 15 MPa and 150°C, the mixture was heated to t c90 Vulcanization 7min(t c90 measured by a rubber process analyzer).

[0066] Comparative Example 3:

[0067] A preparation process of nano-sulfur@graphene oxide modified natural rubber, wherein the contents of the components in the obtained modified natural rubber composite material are exactly the same as those in Example 1 (see Table 1), specifically comprising the following steps:

[0068] ①Same as ① in Example 1.

[0069] ② is the same as ③ in Example 1, except that the nano-sulfur / vulcanization accelerator @ graphene oxide in Example 1 is replaced with nano-sulfur @ graphene oxide. Specifically, deionized water is added to the natural latex emulsion to control the concentration to 30wt.%; 2.65mg / mL of the nano-sulfur @ graphene oxide aqueous dispersion prepared in step ① is added and mechanically stirred for 30min; 10wt% calcium chloride solution is added to flocculate the latex, wherein the volume ratio of the natural latex emulsion, the nano-sulfur @ graphene oxide aqueous dispersion, and the calcium chloride solution is 167:100:30; the obtained raw rubber is soaked in water and changed with water for many times, and then dried at 60°C to constant weight to obtain the nano-sulfur @ graphene oxide modified natural rubber masterbatch.

[0070] ③Same as ④ in Example 1.

[0071] ④ is the same as ⑤ in Example 1, except that the nano-sulfur / vulcanization accelerator@graphene oxide in Example 1 is replaced with nano-sulfur@graphene oxide, and the added amount of CZ is 2 phr. Specifically, 80 phr of the graphene oxide modified natural rubber masterbatch prepared in step ③ was added to a 110°C internal mixer and mixed for 4 minutes, and then 2 phr of antioxidant 4020, 2 phr of antioxidant RD and 2 phr of vulcanization accelerator CZ were added. After mixing for 4 minutes, 5 phr of activator zinc oxide, 2 phr of softener stearic acid and 18 phr of N330 carbon black were added, and mixed for 4 minutes. Finally, 17 phr of N330 carbon black was added, and the rubber was discharged after mixing for 4 minutes; the discharged rubber was cooled to room temperature and then mixed on a 60°C mixing mill for 10 minutes, during which 20 phr of nano-sulfur@graphene oxide modified natural rubber masterbatch with a natural rubber content of 1.71 phr of sulfur was added, and after being mixed evenly, the rubber was thinly passed until there were no bubbles in the rubber to obtain a mixed rubber; the mixed rubber was placed at room temperature for 24 hours and then put into a vulcanization mold, and at 15 MPa and 150°C, the mixture was heated to t c90 Vulcanization 6min(t c90 measured by a rubber process analyzer).

[0072] The natural rubber composite materials obtained in Examples 1 to 2 and Comparative Examples 1 to 3 were subjected to performance tests. The test standard for tensile properties was GB / T 528-2009, and the tensile rate was 500 mm / min. The test standard for tear properties was GB / T 529-2008. The test standard for hardness was GB / T531.1-2008. The test standard for abrasion properties was GB / T 9867-2008. The test standard for crosslink density was GB / T 533-2008. The test standard for heat generation properties was GB / T1687.1-2016.

[0073] Table 1 Formula table of Examples 1 to 2 and Comparative Examples 1 to 3

[0074]

[0075] Table 2 Comprehensive performance of Examples 1 to 2 and Comparative Examples 1 to 3

[0076] sample Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Tensile strength(MPa) 25.08 26.2 27.0 28.3 27.8 Tear strength (N / mm) 71.2 78.5 84.3 97.5 92.4 Hardness(HA) 60.5 61 62 63 66.5 <![CDATA[Wear volume (mm 3 )]]> 94.3 85.5 88.2 82.9 83.4 <![CDATA[Crosslink density (*10 -4 )]]> 6.032 7.061 7.445 7.772 7.332 Calorific value (℃) 12.2 10.5 10.2 9.7 9.5

[0077] It can be seen from Table 2 that compared with the graphene oxide modified natural rubber composite materials of Comparative Examples 1 to 3, the tensile strength, tear strength, hardness, dynamic compression heat generation performance, wear resistance and crosslinking density of the controllable cross-linked graphene modified natural rubber composite materials with high vulcanization efficiency and low heat generation of the present invention (Examples 1 to 2) are improved.

[0078] The above is only a specific implementation of the present invention, which enables those skilled in the art to understand or implement the present invention. Although detailed descriptions are given with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments, and they should all be covered by the protection scope of the claims.

Claims

1. A controllably cross-linked graphene-modified natural rubber with high vulcanization efficiency and low heat generation, characterized in that: The invention comprises natural rubber, rubber additives, reinforcing fillers and nano-sulfur / vulcanization accelerator@graphene oxide with nano-sulfur and vulcanization accelerator simultaneously loaded on the surface; the natural rubber is 100 parts by mass, the rubber additive is 8 to 15 parts by mass, the reinforcing filler is 30 to 90 parts by mass, and the nano-sulfur / vulcanization accelerator@graphene oxide contains 0.4 to 2 parts by mass of graphene oxide; The mass ratio of nanosulfur: vulcanization accelerator: graphene oxide in the nanosulfur / vulcanization accelerator@graphene oxide is 3-7:3-7:10; the nanosulfur / vulcanization accelerator@graphene oxide improves the dispersibility of the vulcanizer and the vulcanization accelerator and the contact area with the natural rubber matrix, improves the vulcanization efficiency and the crosslinking density and uniformity of the crosslinked network of the obtained vulcanized rubber, and controls the crosslinking sites at the same time, and gives the natural rubber vulcanized rubber low heat generation performance by reducing the friction between fillers and fillers and fillers and matrix.

2. The controllably cross-linked graphene-modified natural rubber with high vulcanization efficiency and low heat generation according to claim 1, characterized in that: The rubber additives include an antioxidant, an antioxidant, a vulcanization accelerator, an activator, and a softener, and the mass ratio of the antioxidant, the antioxidant, the vulcanization accelerator, the activator, and the softener is 2:2:1.3-1.85:5:

2.

3. The controllably cross-linked graphene-modified natural rubber with high vulcanization efficiency and low heat generation according to claim 2, characterized in that: The vulcanization accelerator is at least one of N-tert-butyl-2-benzothiazole sulfenamide, N-cyclohexyl-2-benzothiazole sulfenamide and N-(diethylene oxide)-2-benzothiazole sulfenamide; the antioxidant is at least one of 2,6-di-tert-butyl-4-methylphenol, 2,2,4-trimethyl-1,2-dihydroquinoline polymer and 2-thiol benzoimidazole; the antioxidant is at least one of N-(1-methylisoamyl)-N'-phenyl-p-phenylenediamine and p-phenylaniline or dilauryl dipropionate sulfide; the activator is at least one of zinc gluconate, zinc oxide and magnesium oxide; the softener is at least one of stearic acid, dibutyl titanate and dioctyl adipate; the vulcanizer is sulfur; and the reinforcing filler is carbon black.

4. A water phase synergistic coagulation streamlined preparation process of controllably cross-linked graphene-modified natural rubber with high vulcanization efficiency and low heat generation according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) adding an acidic solution and a sulfur source solution to a graphene oxide aqueous dispersion, reacting at a temperature of T1 for a time of t1, to obtain a graphene oxide aqueous dispersion loaded with nano-sulfur; then sequentially adding deionized water and an ethanol solution of a vulcanization accelerator, reacting at a temperature of T2 for a time of t2, centrifuging and dispersing in deionized water, to obtain a nano-sulfur / vulcanization accelerator@graphene oxide aqueous dispersion; (2) adding deionized water to natural rubber latex, mixing well, then adding the nano-sulfur / vulcanization accelerator @ graphene oxide aqueous dispersion obtained in step (1), mixing well, then adding a flocculant, flocculating due to the reduction of negative charge repulsion between particles to keep the rubber latex stable, and the rubber particles with the damaged protective layer and the nano-sulfur / vulcanization accelerator @ graphene oxide will be mutually adsorbed to form bound particles through the interaction force; the bound particles and the rubber particles are orderly aggregated in the aqueous phase and precipitated out in coordination; the obtained raw rubber is washed with water for multiple times and dehydrated and then dried to obtain the nano-sulfur / vulcanization accelerator @ graphene oxide modified natural rubber masterbatch; (3) adding deionized water to natural rubber latex, mixing well, and then adding graphene oxide aqueous dispersion, mixing well, and then adding flocculant, so that the negative charge repulsion between particles that keeps the rubber latex stable is reduced and flocculation occurs, and the rubber particles with the damaged protective layer and the graphene oxide will be adsorbed to each other through the force to form combined particles; the combined particles and the rubber particles are orderly aggregated in the water phase and precipitated out in coordination; the obtained raw rubber is washed with water for multiple times and then dried after dehydration, so as to obtain the graphene oxide modified natural rubber masterbatch; (4) placing the graphene-modified natural rubber masterbatch obtained in step (3) in an internal mixer, and discharging the rubber material after internal mixing at a temperature of T3 for a time of t3, during which time rubber additives and reinforcing fillers are added; after the discharged rubber material is cooled to room temperature, it is mixed on an open mixer at a temperature of T4 for a time of t4, during which time a vulcanizing agent and the nano-sulfur / vulcanization accelerator @ graphene oxide-modified natural rubber masterbatch obtained in step (2) are added, and after being uniformly mixed, the rubber material is thinly passed until there are no bubbles in the rubber material to obtain a mixed rubber; after the mixed rubber material is placed at a temperature of T5 for a time of t5, it is vulcanized in a mold at a temperature of T6 and a certain pressure for a time of t6, thereby obtaining a controllably cross-linked graphene-modified natural rubber with high vulcanization efficiency and low heat generation.

5. The aqueous phase synergistic coagulation streamlined preparation process of a controllably cross-linked graphene-modified natural rubber with high vulcanization efficiency and low heat generation according to claim 4, characterized in that: In step (1), at least one of dilute hydrochloric acid, ascorbic acid, formic acid, citric acid and sulfuric acid is used to prepare the acidic solution; at least one of sodium sulfate, sodium thiosulfate, sodium persulfate and sodium thiosulfate pentahydrate is used to prepare the sulfur source solution; the reaction temperature T1 for preparing the nano-sulfur-loaded graphene oxide aqueous dispersion is room temperature to 50°C, and the reaction time t1 is 1 to 5 h; the reaction temperature T2 for preparing the nano-sulfur / vulcanization accelerator @ graphene oxide aqueous dispersion is 50 to 90°C, and the reaction time t2 is 1 to 4 h.

6. The aqueous phase synergistic coagulation streamlined preparation process of a controllably cross-linked graphene-modified natural rubber with high vulcanization efficiency and low heat generation according to claim 4, characterized in that: In step (1), the concentration of the graphene oxide aqueous dispersion is 1-10 mg / mL; the concentration of the acidic solution is 0.01-0.1 mol / L; the concentration of the sulfur source solution is 100-200 mg / mL; the concentration of the ethanol solution of the vulcanization accelerator is 20-60 mg / mL; and the concentration of the nano-sulfur / vulcanization accelerator@graphene oxide aqueous dispersion is 1-10 mg / mL.

7. The water-phase synergistic coagulation streamlined preparation process of a controllably cross-linked graphene-modified natural rubber with high vulcanization efficiency and low heat generation according to claim 4, characterized in that: In steps (2) and (3), the amount of deionized water added is such that the concentration of the prepared natural rubber latex emulsion is 15-35 wt.%.

8. The aqueous phase synergistic coagulation streamlined preparation process of a controllably cross-linked graphene-modified natural rubber with high vulcanization efficiency and low heat generation according to claim 4, characterized in that: In step (2), the flocculant is selected from at least one of calcium chloride, formic acid, hydrochloric acid, sodium chloride and potassium chloride solution; and the drying temperature of the raw rubber is 40-80°C.

9. The water-phase synergistic coagulation streamlined preparation process of a controllably cross-linked graphene-modified natural rubber with high vulcanization efficiency and low heat generation according to claim 4, characterized in that: In step (3), the concentration of the added graphene oxide aqueous dispersion is 1-10 mg / mL; the flocculant is selected from at least one of calcium chloride, formic acid, hydrochloric acid, sodium chloride and potassium chloride solution; and the drying temperature of the raw rubber is 40-80°C.

10. The water phase synergistic coagulation streamlined preparation process of a controllably cross-linked graphene-modified natural rubber with high vulcanization efficiency and low heat generation according to claim 4, characterized in that: In step (4), T3=100~120°C, t3=10~16 min; T4=50~70°C, t4=10~15 min; T5=room temperature, t5=20~30 h; T6=140~160°C, vulcanization pressure 10~20 MPa, t6=5~15 min.

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