CN106188675A - Anti-old white carbon and preparation method thereof and the application in natural rubber - Google Patents

Abstract

The invention discloses an anti-aging white carbon black, a preparation method thereof and an application in natural rubber. The present invention adopts a two-step synthesis route, grafting γ-aminopropyltriethoxysilane and 3,5-di-tert-butyl-4-hydroxyphenylacetic acid onto the surface of white carbon black to functionalize the white carbon black , which not only improves the surface properties of silica, so that it has better dispersibility, but also makes it have a certain anti-aging function, and can also inhibit the volatilization and migration of anti-aging agents in rubber. Moreover, such a method will not affect the environment, is non-toxic, and is safe and reliable. The invention is simple and easy to implement, low in cost and good in use effect.

Description

Anti-aging white carbon black and its preparation method and application in natural rubber

technical field

The invention belongs to the technical field of material science, in particular to anti-aging white carbon black, its preparation method and its application in natural rubber.

Background technique

Carbon black and silica are currently the most widely used reinforcing agents in the rubber industry. With the increasing shortage of non-renewable resources such as oil and natural gas, and the harm caused by carbon black to the environment and human health during use, the application of carbon black is limited. The use of white carbon black to completely replace carbon black has become a research hotspot in the field of rubber today. Silica is a chain branched aggregate whose chemical composition is mainly amorphous silica. Its surface contains a large amount of silanol, which is hydrophilic and easy to agglomerate, resulting in poor compatibility with the rubber matrix and poor dispersion in the rubber. In addition, during the rubber vulcanization process, the weakly acidic silica on the surface is easy to adsorb the compounding agents in the rubber, delaying vulcanization and causing problems such as a decrease in crosslinking density, which seriously affects its reinforcing performance. In order to solve this problem, silica needs to be modified before it is used. Currently the most used is the silane coupling agent Si69, which bonds silica to the rubber molecular chain through a sulfur bond.

In addition to the reinforcing performance of rubber, the thermo-oxidative aging performance is also an important indicator to measure the quality of rubber products. Thermal oxygen aging belongs to free radical chain autocatalytic oxidation reaction, which is an irreversible reaction, which will eventually lead to the destruction of the internal structure of rubber and lose its use value. Therefore, when preparing rubber products, it is often necessary to add an appropriate amount of anti-aging agent to prolong the service life of the rubber. Most of the antioxidants currently used in rubber belong to diphenylamines, which have low toxicity. In addition, during the use of rubber, it is necessary to pay attention to the fact that the anti-aging agent will volatilize and migrate from the rubber product, reducing its protective effect.

Phenol antiaging agent is a kind of non-toxic and has good resistance to thermal oxygen aging and environmental protection. There are few reports on the grafting of phenolic antioxidants onto the surface of silica. Moreover, the research on the thermo-oxidative aging properties of phenolic antioxidant grafted silica/natural rubber composites has not been carried out systematically.

Contents of the invention

The object of the present invention is: provide a kind of anti-aging white carbon black and its preparation method and the application in natural rubber, it has good dispersibility, and also has anti-aging function, also suppressed anti-aging agent in rubber simultaneously Volatilization and migration to overcome the deficiencies of the prior art.

The present invention is achieved in this way: anti-aging white carbon black, calculated by weight parts, includes 20-30 parts of white carbon black, 2-3 parts of silane coupling agent KH550, 1-1.5 parts of N,N'-dicyclohexyl Carbodiimide and 1.5-2 parts of 3,5-di-tert-butyl-4-hydroxyphenylacetic acid are the raw materials for preparation.

The preparation method of anti-aging white carbon black, according to the above mass fraction, mix white carbon black with 90% ethanol solution by mass percentage, after ultrasonic oscillation for 45 minutes, heat the mixed solution to 55-65°C, and adjust the pH value to 6 ~7, dropwise add the pre-hydrolyzed silane coupling agent KH550, reflux and condense for 3~5h under stirring conditions; then raise the temperature to 95~100°C, and add N,N'-dicyclohexyl carbon after the temperature is stable Diimine and 3,5-di-tert-butyl-4-hydroxyphenylacetic acid, react for 2-4 hours; finally wash with absolute ethanol and perform suction filtration, and dry the filtrate in a vacuum oven at 85-95°C 10-15h, get anti-aging white carbon black.

The pH was adjusted with glacial acetic acid.

The solid-liquid ratio of white carbon black to ethanol solution is 25:200, and the unit is g/mL.

The pre-hydrolyzed silane coupling agent KH550 specifically includes adding the silane coupling agent KH550 into water for ultrasonic hydrolysis; the ratio of solid to liquid for hydrolysis is 2.5:10-15, and the unit is g/mL.

For the application of anti-aging silica in natural rubber processing, anti-aging silica is used as a reinforcing filler and anti-aging agent, and the mass ratio of anti-aging silica to natural rubber is 1:2.

The reaction principle of the present invention is as follows:

Owing to having adopted above-mentioned technical scheme, compared with prior art, the present invention adopts the synthetic route of two-step method, and γ-aminopropyltriethoxysilane and 3,5-di-tert-butyl-4-hydroxyphenylacetic acid Grafting to the surface of silica to functionalize silica, which not only improves the surface properties of silica, makes it have better dispersibility, but also makes it have a certain anti-aging function, and can also inhibit the aging of the anti-aging agent in the rubber. volatilization and migration. Moreover, such a method will not affect the environment, is non-toxic, and is safe and reliable. The invention is simple and easy to implement, low in cost and good in use effect.

Description of drawings

Accompanying drawing 1 is the infrared spectrogram of silica before and after modification;

Accompanying drawing 2 is the TGA collection of illustrative plates of silica before and after modification;

Accompanying drawing 3 is the storage modulus G' of silica/natural rubber composite material under 60 ℃ and the relationship curve of strain

Accompanying drawing 4 is the relation of elongation at break rate of change after thermo-oxidative aging of white carbon black/natural rubber composite material;

Accompanying drawing 5 is the relation of the rate of change of tensile strength after thermal oxygen aging of white carbon black/natural rubber composite material;

Accompanying drawing 6 is the hardness retention rate relation after the thermo-oxidative aging of white carbon black/natural rubber composite material;

Accompanying drawing 7 is the thermal oxygen stability of white carbon black/natural rubber vulcanizate under air atmosphere;

Accompanying drawing 8 is the thermal cracking property of white carbon black/natural rubber vulcanizate under nitrogen atmosphere;

Accompanying drawing 9 is the TG-DSC figure of comparative example 1 white carbon black/natural rubber vulcanizate;

Accompanying drawing 10 is the TG-DSC figure of comparative example 2 silica/natural rubber vulcanizate;

Accompanying drawing 11 is the TG-DSC figure of embodiment 2 white carbon black/natural rubber vulcanizates;

Accompanying drawing 12 is different formula white carbon black/natural rubber apparent activation energy and the relationship curve of thermal weight loss rate.

detailed description

In the following implementation, white carbon black is selected from precipitated white carbon black, model TS-180, Changzhou Lehuan Chemical Co., Ltd.; rubber oil, model KN4010, Guangzhou Peirui Chemical Co., Ltd.; natural rubber (NR), zinc oxide, stearin Acid, sulfur, accelerator D, accelerator M, accelerator DM, accelerator TDTM, anti-aging agent 4020 are provided by Guizhou Tire Factory; silane coupling agent Si69, Dongguan City Changping Yuxin Plasticization Business Department; silane coupling agent KH550 , Dongguan City Changping Yuxin Plasticization Business Department; absolute ethanol, analytically pure, Chongqing Chuandong Chemical Co., Ltd.; glacial acetic acid, analytically pure, Tianjin Fuyu Fine Huagong Co., Ltd.; N,N'-dicyclohexyl carbon di Imine, analytically pure, Aladdin Reagent (Shanghai) Co., Ltd.; 3,5-di-tert-butyl-4-hydroxyphenylacetic acid, analytically pure, Aladdin Reagent (Shanghai) Co., Ltd.

Embodiment 1 of the present invention: the preparation of anti-aging white carbon black, 25g of white carbon black and 200ml mass percent of 90% alcohol aqueous solution are blended in a 500ml three-necked flask, fully ultrasonically oscillated for 45min, and the frequency of the ultrasonic instrument is 40KHZ, The power is 200W; after moving it into the oil bath, when the temperature reaches 60°C, adjust the pH value to 6-7 with glacial acetic acid, and add 2.5g of pre-hydrolyzed silane coupling agent KH550 dropwise; the whole reaction process is under reflux Proceed for 4 hours under the condenser and mechanical stirring, then raise the temperature to 97°C, and add 1.5g of N,N'-dicyclohexylcarbodiimide (DCC) after the temperature is stable, and the molar ratio of reaction with KH550 is 1 :1 Add 3,5-di-tert-butyl-4-hydroxyphenylacetic acid (approximately 2.96g), react for 3h; finally wash with absolute ethanol several times, filter with suction, put the white carbon black powder into 90 ℃ vacuum Dry in a drying oven for 12 hours to obtain white carbon black powder with anti-aging function.

Embodiment 2 of the present invention: the application of anti-aging white carbon black in natural rubber processing,

Add natural rubber into the internal mixer, set the initial temperature of the internal mixer to 90°C, and the rotor speed to 80r/min. After masticating for 1 minute, add white carbon black and rubber oil successively, and perform internal mixing for 5 minutes to prepare the masterbatch. Put the masterbatch well mixed into the open mill and practice. After the masterbatch is covered with rolls, add zinc oxide, stearic acid, accelerators D, M, DM, TDTM, anti-aging agent 4020 and sulfur in sequence. After mixing evenly, pack three times on the left and right sides, pass five times on the thin pass, and adjust the roller distance to 2mm to exit the roller to prepare the mixed rubber. Place the mixed rubber at normal temperature for 24 hours, and after using a vulcanizer to test its positive vulcanization time, vulcanize it on a flat vulcanizer. The vulcanization temperature is 145 ° C. In this embodiment, the mass ratio of natural rubber to white carbon black is 2: 1.

In order to verify the technical effect of the present invention, the applicant has also carried out a comparative test, and the formula adopted in the experiment is as shown in Table 1.

Table 1 (unit: parts by mass)

1. Material testing and characterization

1.1 Structural characterization of anti-aging silica

The infrared structure of silica before and after modification was characterized by Nicolet 6700 Fourier infrared spectrometer of Thermo Fisher Corporation of the United States, and the measurement range was 4000～400cm ^-1 ; Excellent thermal stability, the temperature range is 70-700°C, and the heating rate is 20°C/min.

1.2 Vulcanization characteristic test

The MD-3000A rheometer of Taiwan High Speed Rail Technology Co., Ltd. was used to test the vulcanization characteristics of the compound rubber. The test temperature was 145°C and the test time was 15 minutes;

1.3 RPA test

Use the rubber processing analyzer RPA2000 of American Alpha Company to carry out strain scanning on the mixed rubber: temperature 60 ℃, frequency 1Hz, strain amplitude 0.7-400%;

1.4 Testing of mechanical properties

The Insekt10 universal testing machine of Germany Huibo Material Testing Company is used to test the tensile strength, elongation at break and constant elongation of the vulcanized sample according to GB/T528-1998, and the test speed is 500mm min ^-1 ; according to GB/T529- Test the tear strength of the sample in 1999; test the Shore A hardness of the sample according to GB/T531-1999;

1.5 Thermal Oxygen Aging Performance Test

The JZ401A aging test box of Yangzhou Jingzhuo Test Machinery Factory was used to measure the heat and oxygen aging resistance of vulcanized rubber according to GB/T3512-2001. After the end, place the sample for 10 hours to measure its related properties;

1.6 Thermal oxygen decomposition kinetics test

The NETZSCH209 thermal analyzer (Germany Netzsch) was used to test the vulcanizate of composite materials. The temperature range was from room temperature to 700 ° C, the heating rate was 5, 10, 20, and 30 ° C/min, and the atmosphere was nitrogen or air.

2. Results and Discussion

2.1 Infrared spectrum of anti-aging silica

Figure 1 is the infrared spectrum of silica before and after modification. In the figure, 1104cm-1 is the antisymmetric stretching vibration peak of Si—O—Si, 958cm—1 is the stretching vibration peak of Si—OH on the surface of white carbon black, and 801cm—1 and 475cm—1 are respectively the symmetrical stretching and stretching of Si—O—Si The vibration peak and bending vibration peak, the absorption peak at 3404cm-1 is caused by the adsorption of water on the surface of silica. Compared with the infrared spectrum of unmodified silica, the modified anti-aging silica has a stretching vibration peak of —CH ₂ — at 2932cm-1, and amide groups (CONH ) CO stretching vibration absorption peak and NH bending vibration absorption peak, indicating that the silica modification was successful.

2.2 Thermal stability of anti-aging silica

Figure 2 is the TGA spectrum of silica before and after modification. Before the thermogravimetric experiment, the samples were placed in an oven at 70 °C for 1 h to remove the adsorbed water on the surface of the silica. It can be seen from the figure that before 150°C, the weight loss rate of unmodified silica is greater than that of modified silica, and this part of the weight loss is caused by the residual adsorbed water on the surface of silica; after 150°C, the unmodified The decrease in the weight loss rate of permanent silica is due to the condensation and dehydration of Si-OH on its surface. The hydrophilicity of the two kinds of modified silica is weakened, and the weight loss rate is lower than that of unmodified silica before 150 °C. For the white carbon black modified by the anti-aging agent, in the range of 150°C to 230°C, the decrease in thermal weight loss is due to the low molecular volatilization of the residual coupling agent left during the experiment; after 230°C, the modified white carbon The weight loss rate of black further decreased, and the decrease was relatively large, which was partly caused by the anti-aging agent grafted and coated on the surface of silica. It can be seen from the figure that the weight loss rates of unmodified silica, KH550 modified silica and antioxidant modified silica are 5.70%, 7.11%, and 9.74%, respectively, that is, the grafted amount of KH550 is about 1.41%. , the grafting amount of anti-aging agent is about 2.63%.

2.3 Vulcanization characteristics of silica/natural rubber composites

Table 2

Table 2 shows the vulcanization characteristics of silica/natural rubber composites. It can be seen that the scorch time of the four samples has little change, but the difference in the normal vulcanization time is relatively large. Since antioxidant 4020 contains some amine groups, which can promote vulcanization, the positive vulcanization time of formula b with 4020 anti-aging agent is reduced by 12.1% compared with comparative example 1; the positive vulcanization time of formula c is reduced by 51.1% compared with comparative example 1 In addition to the role of amine groups on the anti-aging agent 4020, the main reason is that the addition of Si69 greatly improves the polarity of the silica surface, weakens the adsorption of the silica to the accelerator, and thus greatly shortens the curing time ; The positive vulcanization time of formula d was reduced by 35.4%. It can be seen from Comparative Examples 2 and 3 that after the silica is treated with a silane coupling agent, the normal vulcanization time can be greatly shortened and the production cost can be reduced. M _L is the minimum torque of vulcanization, and its size can indirectly reflect the interaction between fillers. The smaller M _L is, the weaker the interaction between fillers is. It can be seen from the samples of Comparative Examples 1 and 2 that the addition of anti-aging agent 4020 has little change in _ML . Compared with the minimum torque of the sample of Example 2 of the present invention, the minimum torque of the sample of Comparative Example 2 has decreased by 15.05%, while the formula c with Si69 added, the minimum torque M _L has decreased by 45.77%, indicating that Si69 modified white Carbon black disperses best in natural rubber.

2.4 Mechanical properties of silica/natural rubber composites

table 3

The Shore A hardness is related to the degree of crosslinking of the composite. For comparative examples 1 and 2, due to the adsorption and adsorption effect of white carbon black on the accelerator, the vulcanization is not complete, and the degree of crosslinking of natural rubber is low, resulting in the lowest hardness. And formula comparative example 3 and embodiment 2, after silica is modified by coupling agent, the degree of crosslinking all increases, and wherein the hardness of comparative example 3 is the highest because -S ₄ - in Si69 participates in vulcanization, crosslinking to the greatest extent.

300% modulus stress is often used as the basis for judging the interaction between rubber and filler. It can be seen from the above table that Comparative Example 3 and Example 2 have higher dispersibility and higher 300% modulus than Comparative Examples 1 and 2 of unmodified SiO ₂ /NR due to the reduced degree of agglomeration of modified silica. The 300% modulus of Comparative Example 3 is greater than that of Example 2, because the Si69-modified silica can be bonded to the rubber macromolecular chain during the vulcanization process.

Tensile strength and tear strength are important indicators for evaluating the mechanical properties of rubber composites. It can be seen from the table that the tensile strength of formula d grafted to the surface of silica is increased by 15.44% and the tear strength is increased by 11.2% compared with formula b, but both are lower than the increase of formula c. From formulations a and b, it can be seen that the antiaging agent 4020 has no significant effect on the elongation at break of natural rubber composites. The SiO ₂ /NR modified by Si69 has the smallest elongation at break, and the elongation at break of SiO ₂ /NR grafted with anti-aging agent also drops significantly, reaching 789%. This shows that the use of Si69 and anti-aging coupling agent can improve the performance of vulcanizate.

2.5 Dynamic viscoelastic analysis of silica/natural rubber composites

Generally, the phenomenon that the storage modulus decreases sharply with the increase of strain is called the Payne effect. The Payne effect can reflect the dispersibility of the filler in the rubber. The more obvious the Payne effect, the stronger the interaction between the fillers and the worse the dispersibility. Fig. 3 is a graph showing the relationship between the storage modulus G' and the strain of the silica/natural rubber composite material at 60°C. It can be seen from Figure 3 that when the strain reaches 400%, the storage modulus G' of all the curves basically tends to the same. The Payne effect of the sample of comparative example 1 without 4020 added to unmodified silica and the sample of comparative example 2 with 4020 added to unmodified silica did not change much, indicating that the anti-aging agent 4020 has an effect on silica in natural rubber. The dispersibility of the unmodified silica has little effect, and the storage modulus G' of the two samples of unmodified silica under small strain is higher than that of other samples, which is because the unmodified silica particles The interaction is larger and the degree of reunion is more serious. It can also be seen from the figure that the sample of Example 2, due to the increase of surface organic components after the modification of silica, the weakening of surface polarity, and the weakening of the agglomeration phenomenon between fillers, etc., under small strains, the energy storage mode The amount G' is smaller than the samples of Comparative Examples 1 and 2 of unmodified silica. However, the sample of Comparative Example 3 that is larger than Si69 modified silica shows that the dispersibility of silica grafted with anti-aging agent on the surface is improved in natural rubber, but its effect is lower than that of Si69 modified silica. This is consistent with the analytical results of M _L in the vulcanization characteristics.

2.6 Thermo-oxidative aging properties of silica/natural rubber composites

Figure 4 is the relationship between the change rate of elongation at break of the silica/natural rubber composite material after thermo-oxidative aging. It can be seen from Figure 4 that the change rate of elongation at break of SiO ₂ /NR without modification and without 4020 drops the most, which is caused by the thermal degradation of rubber molecular chains during the thermo-oxidative aging process; Si69 modified SiO ₂ After aging for one _day , the elongation at break of /NR first increased and then decreased, which may be due to the fact that Si69 has anti-reversion property and can play a better balanced vulcanization effect; After 2 days, the rate of change of elongation at break remained basically unchanged, indicating that the antioxidant grafted onto the surface of silica had better heat-oxidative aging resistance.

Figure 5 is the relationship between the change rate of tensile strength of silica/natural rubber composites after thermo-oxidative aging. Unmodified SiO ₂ /NR without adding 4020 anti-aging agent, after aging for 1 day, the change rate of tensile strength decreased greatly, and then the rate of decrease slowed down. Among the four formulations, the rate of change of tensile strength decreased the most. In comparative example 3 of Si69 modified silica, after aging for 2 days, the change in tensile strength first increases and then decreases, and the anti-aging performance is the best. And the comparative example 2 that has added 4020 after aging for 2 days, its rate of change of tensile strength is less than the embodiment 2 of grafting anti-aging agent, illustrates that after aging for 2 days, anti-aging agent 4020 is compared to the synthetic anti-aging white carbon black to SiO ₂ /NR has better tensile strength retention.

Figure 6 is the relationship between the hardness retention rate of silica/natural rubber composites after thermo-oxidative aging. It can be seen from Figure 6 that before aging for 2 days, the hardness of all formulations has increased. This is because during the thermo-oxidative aging process, subsequent vulcanization occurs inside the vulcanizate samples of each formulation, and the degree of vulcanization increases, resulting in the hardness of the vulcanizate. Increased hardness. After aging for 2 days, due to long-term aging, the rubber undergoes thermal degradation, the molecular chains are broken, and the crosslinking density decreases, resulting in a decrease in the hardness of the samples of unmodified silica comparative examples 1 and 2. On the contrary, due to the balanced vulcanization of Si69 in Comparative Example 3, the hardness continued to increase; the hardness of Example 2 continued to increase and then remained unchanged, probably because the anti-aging agent grafted to the surface of silica is not easy to volatilize and can effectively prevent natural rubber The thermal degradation shows that the phenolic anti-aging agent grafted on the surface of silica has better anti-aging effect.

2.7 Thermo-oxidative stability and thermal cracking stability of silica/natural rubber composites

It can be seen from Figure 7 that during the thermo-oxidative aging process, the thermal weight loss curve of silica/natural rubber vulcanizate is divided into two stages, the first stage is 200-420°C, and the second stage is 420-420°C. 520°C. When the anti-aging agent was added, the thermal weight loss temperature of silica/natural rubber vulcanizate increased. The thermal weight loss temperature of Example 2 grafted onto the surface of silica is 13.4°C higher than that of Comparative Example 1 without any anti-aging agent, but lower than that of Comparative Examples 2 and 3 with the addition of anti-aging agent 4020. The thermo-oxidative aging process of natural rubber is an autocatalytic oxidation process, which belongs to the free radical chain reaction and generates a large number of oxygen-containing free radicals. For Example 2, these oxygen-containing free radicals first capture the hydrogen atom on the phenolic hydroxyl group of the anti-aging agent and terminate, lose their reactivity, and form new phenolic oxygen free radicals and then couple with other free radicals to terminate, finally inhibiting the white carbon black / Thermal-oxidative aging process of natural rubber vulcanizates.

Under a nitrogen atmosphere, as shown in Figure 8, the thermogravimetric curves of silica/natural rubber vulcanizate have a high coincidence, and the addition of anti-aging agent does not change the thermogravimetric curve much. Compared with the air atmosphere, the thermogravimetric curve in the pyrolysis process has only one step. The thermal cracking reaction of natural rubber vulcanizate is carried out by free radical mechanism, and the random chain scission reaction mainly occurs. It can be seen from Fig. The thermal oxygen aging process has a certain slowing effect, but has no effect on the random chain scission reaction of natural rubber vulcanizate thermal cracking.

2.8 Thermal oxidation activation energy of silica/natural rubber composites

2.8.1 Kissinger method (differential method)

The Kissinger method is a method for kinetic analysis of the data points on a thermal analysis curve measured by the reaction at the same scan rate. The Kissinger equation is expressed as follows:

$\begin{array}{cc}\mathrm{<span\; class="notranslate">\; l</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; l</span>}\mathrm{<span\; class="notranslate">\; no</span>}\frac{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; R</span>}}{\mathrm{<span\; class="notranslate">\; E.</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; E.</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}}& \mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; ...</span>}\mathrm{<span\; class="notranslate">\; L</span>}\end{array}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula: β is the heating rate; T _p is the temperature value corresponding to the peak of the thermal analysis curve; A is the pre-exponential factor; R is the thermodynamic constant; E is the thermal oxidation activation energy. Through ln(β/T _p ² )～1/T _p as a relationship diagram, E can be obtained from the slope of the line, and A can be obtained from the intercept. The calculation results are shown in Table 1.

Table 4

The size of the activation energy marks the difficulty of thermal degradation of the sample. The greater the activation energy, the greater the energy required for the degradation reaction, that is, the less likely the sample is to be thermally degraded. Table 4 shows the thermal oxidation activation energy of different formulations of vulcanizates at different stages. It can be seen from the table that the thermal oxidation activation energy of the vulcanized rubber added with anti-aging agent is significantly higher than that of the vulcanized rubber without anti-aging agent. Among them, the thermal oxidation activation energy of the grafted phenolic anti-aging agent increased by 10.41kJ/mol in the first stage, and increased by 14.29kJ/mol in the second stage, but both stages were lower than the thermal oxidation activation energy of 4020, indicating that the grafted The anti-aging effect of the phenolic anti-aging agent on the surface of the silica is lower than that of the anti-aging agent 4020.

2.8.1 Flynn-Wall-Ozawa method (integral method)

The Flynn-Wall-Ozawa method is a method of multiple scanning rates, that is, analyzing multiple thermal analysis curves measured at different heating rates to obtain relevant kinetic parameters. This method can avoid possible errors caused by different assumptions of the reaction mechanism function, and can directly calculate the activation energy. The thermal oxidation activation energy E of the silica/natural rubber composite vulcanizate can be calculated by the Flynn-Wall-Ozawa method. The calculation formula is:

$\mathrm{<span\; class="notranslate">\; lg</span>}\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; lg</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; E.</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; G</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2.315</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.4567</span>}\frac{\mathrm{<span\; class="notranslate">\; E.</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

In the formula: β is the heating rate; R is the thermodynamic constant; A is the thermal oxidation reaction conversion rate; E is the thermal oxidation activation energy; α is the thermal weight loss rate.

Under the same reaction depth α (G(α) is a constant value at this time), there are corresponding temperatures Ti for different heating rates βi, and each set of data (β _i , T _i ) is brought into (2 ), a set of linear equations can be obtained. The linear equation can finally be fitted to obtain a straight line related to _lgβi and 1/Ti, and the activation energy E can be obtained from its slope, and the relationship between the activation energy and the reaction depth α can also be obtained. In actual calculation, the values of α are 0.15, 0.175, 0.2, 0.225, 0.25, 0.275, 0.3, 0.325, 0.35. The calculation results are shown in Table 5.

table 5

It can be seen from Table 5 and Figure 12 that with the increase of the thermal weight loss rate, the thermal oxidation activation energy of silica/natural rubber vulcanizate is divided into two stages: the first stage is from the beginning to the weight loss rate of 0.3, which is In the first stage, with a weight loss rate of 0.2 as the boundary, before 0.2, the range of thermal oxidation activation energy changes little, and after 0.2, the range of thermal oxidation activation energy changes sharply, which may correspond to the automatic acceleration process of thermal oxidation; the second The stage is the weight loss rate of 0.3-0.35, and the thermal oxidation activation energy gradually increases, corresponding to the decomposition of thermal oxidation products and the intensification of thermal oxidation process. It can be seen from the figure that the thermal oxidation activation energy of the anti-aging silica vulcanizate under different thermal weight loss is higher than that of the vulcanizate without any anti-aging agent, but lower than that of the 4020 vulcanizate with the addition of anti-aging agent. It can be seen that the new anti-aging agent grafted on the surface of silica has a certain slowing effect on the thermal-oxidative aging process, but the effect is weaker than that of anti-aging agent 4020, which is consistent with the result of the Kissinger method.

3. Conclusion

The present invention uses silane KH550 as a bridge, and grafts 3,5-di-tert-butyl-4-hydroxyphenylacetic acid onto the surface of silica through the reaction of amino and carboxyl groups, so that the silica has dual effects, that is, it improves the efficiency of silica. Dispersion and endow it with certain anti-aging function. Applying this anti-aging silica to natural rubber, it is found that the scorch time of the anti-aging silica/natural rubber composite material has little change, the positive vulcanization time is shortened, and the minimum torque is reduced; the ratio of tensile strength to tear strength has not changed. Modified silica/natural rubber without 4020 increased by 15.0% and 16.4% respectively, but the increase was lower than the tensile strength and tear strength of Si69 modified silica/natural rubber; after thermal oxygen aging, each The properties of all kinds of composite materials show a downward trend, among which the unmodified silica/natural rubber without 4020 has the most obvious downward trend, while the anti-aging silica/natural rubber and Si69 modified silica/natural rubber can maintain a relatively high good performance.

Claims (6)

1. An anti-aging white carbon black, characterized in that: calculated in parts by weight, comprising 20 to 30 parts of white carbon black, 2 to 3 parts of silane coupling agent KH550, 1 to 1.5 parts of N,N'-bicyclic Hexylcarbodiimide and 2.5-3 parts of 3,5-di-tert-butyl-4-hydroxyphenylacetic acid are the raw materials for preparation. 2. a kind of preparation method of anti-aging white carbon black as claimed in claim 1 is characterized in that: by above-mentioned mass fraction, white carbon black and mass percent are 90% ethanol solution mixing, after ultrasonic vibration 45min, with Heat the mixed solution to 55-65°C, adjust the pH value to 6-7, add the pre-hydrolyzed silane coupling agent KH550 dropwise, reflux and condense for 3-5 hours under stirring conditions; then raise the temperature to 95-100°C , after the temperature is stable, add N,N'-dicyclohexylcarbodiimide and 3,5-di-tert-butyl-4-hydroxyphenylacetic acid, react for 2-4h; finally wash fully with absolute ethanol and carry out suction filtration , drying the filtrate in a vacuum oven at 85-95° C. for 10-15 hours to obtain anti-aging white carbon black. 3. preparation method according to claim 2 is characterized in that: adopt glacial acetic acid to adjust pH value. 4. The preparation method according to claim 2, characterized in that: the solid-liquid ratio of white carbon black and ethanol solution is 25:200, and the unit is g/mL. 5. The preparation method according to claim 2, characterized in that: the pre-hydrolyzed silane coupling agent KH550 is specifically, adding the silane coupling agent KH550 into water for ultrasonic hydrolysis; the hydrolyzed solid-liquid ratio is 2.5 : 10～15, the unit is g/mL. 6. an application of anti-aging white carbon black in natural rubber processing as claimed in claim 1, is characterized in that: using anti-aging white carbon black as reinforcing filler and anti-aging agent, the quality of anti-aging white carbon black and natural rubber The ratio is 1:2.