Preparation method of cationic polymeric resin capable of regulating and controlling softening point, cationic polymeric resin and application

Abstract

The invention belongs to the technical field of rubber additives, and particularly discloses a preparation method and application of cationic polymerization resin with an adjustable softening point, and the preparation method comprises the following steps: adding a solvent and a catalyst into a reaction kettle, and adding a monomer into a high-position dropwise adding tank; cooling the solvent in the reaction kettle to a specified temperature, setting the dropping speed according to the softening point requirement of the target polymer, and starting to drop the overhead tank monomer; along with continuous dropwise adding of the monomer, the viscosity of the system is gradually increased, the viscosity is monitored on line, when the viscosity of the system reaches 150CP, the monomer is continuously dropwise added, meanwhile, the viscosity of the system is controlled to be 150-400CP, when the viscosity is greater than 400CP, the solvent is automatically replenished in the system to dilute the reaction liquid, the softening point of the resin is regulated and controlled by controlling the viscosity of the system to be 150-400CP, and the temperature fluctuation range in the whole dropwise adding process is + / -5 DEG C; the heat preservation temperature is consistent with the dropwise adding temperature, reacting for 6-10 hours, and then desolventizing and granulating. The regulation and control method and the control mechanism of the softening point of the resin in the polymerization stage are defined, so that the resin with the adjustable and controllable softening point is produced through process control.

Description

Technical Field

[0001] The present invention belongs to the technical field of rubber additives, relates to the preparation of cationic polymerization resins, and particularly relates to a preparation method of a cationic polymerization resin with adjustable softening point, a cationic polymerization resin, and its application in the preparation of rubber. Background Art

[0002] In 2023, the total sales volume of automobiles exceeded 30 million, showing a year-on-year increase of about 12% compared with 2022. With the popularization of new energy vehicles and the reduction of vehicle use costs, the sales volume of automobiles will gradually increase. For the general public, the driving safety and use cost of automobiles are the two most important points. As the only component of the automobile that contacts the ground, the tire has a significant impact on driving safety. Especially on wet ground, it is prone to skidding during driving, and accidents are likely to occur, causing casualties. At the same time, during driving, the tire is constantly subjected to external forces, resulting in compression deformation of the tire. The movement of molecular segments consumes energy, and the heat generation of the tire increases, leading to an increase in fuel consumption and an increase in vehicle use costs. However, improving the wet skid resistance of the tire will increase the heat generation of the tire, that is, it is difficult to achieve both wet road surface safety and vehicle use cost. Therefore, how to improve the wet skid resistance of the tire while having a relatively low heat generation is a research hotspot at home and abroad.

[0003] Research has found that the addition of functional resins in the tire formula can improve the balance of tire wet skid performance and heat generation. For a resin to improve the wet skid resistance of the tire, the core is that the resin has a relatively high Tg. By adding the resin, the Tg of the rubber compound can be effectively improved. At the same time, the Tg of the resin is closely related to the softening point during the polymerization process of the resin itself. When the resin structure remains unchanged, the higher the softening point of the resin, the higher the Tg. Adding it to the rubber system can increase the Tg of the overall rubber compound, thereby improving the wet skid resistance. However, in actual applications, the rubber mixing temperature and time are basically fixed. At the same mixing temperature and time, a higher softening point will result in poor dispersion in the rubber system, leading to uneven dispersion of the resin, which will instead affect its physical properties and dynamic properties. Therefore, how to regulate the softening point of the functional resin through the polymerization process is a key difficulty for balancing the application performance of the tire.

[0004] Currently, resins commonly used in tires, such as methyl styrene resins, terpene resins, and copolymerized petroleum resins, are produced by cationic polymerization processes by resin manufacturers at home and abroad due to the relatively large electron cloud density of their monomer structures. However, due to the harsh cationic polymerization conditions, fluctuations in process conditions and different system environments will affect chain termination and chain transfer during polymerization, thereby affecting the molecular weight and molecular weight distribution of the resin, and further resulting in large fluctuations in the softening point of the resin, making it impossible to precisely regulate the softening point of the resin.

[0005] For example, Patent CN111072835B prepares a methyl styrene copolymer resin by cationic polymerization. However, in its process, the initiating solvent is added dropwise to the mixed monomers. Although the resin can be synthesized finally, it is difficult to control its molecular weight (softening point). When the initiating solvent is added dropwise to the mixed monomers during the polymerization process, there is an excess of monomers in the early stage. After adding the initiator, the active centers will carry out chain growth until polymerization is no longer possible. The initiator added in the early stage will form long chains (high softening point). In the later stage, due to the increase in the system viscosity, the monomers are wrapped inside, reducing the collision probability between the monomers and the initiator, resulting in uncontrollable molecular weight of the final polymer and uncontrollable softening point of the resin.

[0006] Patent CN103897087B discloses a cationic polymerization method for an α-methylstyrene / styrene copolymer. In the preparation process of this method, a semi-continuous feeding method needs to be used for feeding, the steps are complex and difficult to control. Moreover, the reaction initiation system is complex and four compounds, namely boron trifluoride ethyl ether complex, ethanol, anhydrous phosphoric acid and phenetole, are required. The post-treatment in industrial production is complex and the cost is high. At the same time, the molecular weight of the final product obtained by this reaction is low and the molecular weight is uncontrollable, resulting in uncontrollable softening point. Summary of the Invention

[0007] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a preparation method of a cationic polymerization resin with adjustable softening point, to solve the problems of the complexity of the cationic polymerization process and the uncontrollability of the softening point of the cationic polymerization resin produced by existing resin manufacturers. Starting from the polymerization mechanism, the present invention clarifies the core influencing factors of the softening point and the process control method, and provides a method for adjusting the softening point of the resin and realizing industrial production. This resin can be used to improve the wet skid resistance and heat generation of tires.

[0008] The present invention is realized through the following technical solutions:

[0009] A preparation method of a cationic polymerization resin with adjustable softening point, comprising the following steps:

[0010] 1) Raw material preparation: Add the solvent and catalyst to the reaction kettle, and add the monomers to the high-level dropping tank;

[0011] 2) Cooling of the polymerization system: Cool the solvent in the reaction kettle to the specified temperature, and start dropping the monomers in the high-level tank;

[0012] 3) Control the viscosity of the system and the dropping rate for dropping: Set the dropping rate according to the softening point of the target polymer, and simultaneously monitor the viscosity online. As the monomer is continuously dropped, the viscosity of the system gradually increases. When the viscosity of the system reaches 150 CP, continue to drop the monomer while controlling the viscosity of the system between 150 - 400 CP. When the viscosity > 400, the system automatically adds solvent to dilute the reaction solution and controls the viscosity of the system between 150 - 400 CP to regulate the softening point of the resin. The temperature fluctuation range during the whole dropping process is within ±5°C;

[0013] 4) Heat preservation and granulation: After the dropping is completed, conduct a heat preservation reaction. The heat preservation temperature is the same as the dropping temperature, and the reaction lasts for 6 - 10 h, and then solvent removal and granulation are carried out.

[0014] A further improvement scheme of the present invention is:

[0015] The solvent is one or a mixture of two or more of toluene, xylene, mesitylene, cyclohexane, dichloroethane, or dichloromethane.

[0016] Further, the initial dosage of the solvent is 40 - 80 wt% of the monomer.

[0017] Further, the catalyst is one or a mixture of two or more of aluminum trichloride, boron trifluoride, boron trifluoride complex, boron trichloride, titanium tetrachloride, or tin tetrachloride.

[0018] Further, the dosage of the catalyst is 0.3 - 10 wt% of the monomer.

[0019] Further, the monomer is one or a mixture of two or more of methylstyrene, p-methylstyrene, styrene, α-methylstyrene, α-pinene, or β-pinene.

[0020] Further, the set dropping rate of the monomer is controlled within the range of 600 - 1500 L / h and is dropped at a constant speed.

[0021] Further, maintain the temperature within the range of -10 - 30°C when dropping the monomer.

[0022] A further improvement scheme of the present invention is:

[0023] For the cationic polymerization resin prepared by the above method, the softening point of the resin is 80°C - 140°C, and the Tg value is 33°C - 90°C. A further improvement scheme of the present invention is:

[0024] Application of the above cationic polymerization resin in the preparation of rubber.

[0025] The softening point is related to the number of long chains and short chains formed in the polymerization system during the polymerization stage, that is, Mw and Mn, and both jointly affect the softening point of the resin. Therefore, the core of controlling the softening point of the resin is to control the probabilities of chain growth, chain transfer, and chain termination in the polymerization system during the polymerization stage, so as to control the Mw and Mn of the resin, and ultimately control the softening point of the resin. The Mw of the resin is greatly affected by the monomer dropping rate. The main mechanism is to control the chain growth stage of the polymerization system to control Mw. The catalyst is added to the solvent to form a catalytic system, and the monomer is dropped to form an active carbocation. Cationic polymerization is non-active polymerization, and the lifetime of the active center carbocation is limited. The speed of dropping actually controls the contact concentration between the carbocation and the monomer during the active maintenance stage. During the active maintenance stage, the faster the monomer dropping rate, the larger the monomer dropping amount, the longer the molecular chain grows, and the larger the Mw. Conversely, Mw decreases. Mn is regulated by controlling the viscosity. The main mechanism is that the greater the viscosity, on the one hand, it will cause the heat inside the polymerization solution to be unable to be discharged, resulting in large temperature fluctuations in the polymerization system. Too high a temperature will cause an increase in cationic chain transfer and termination, making Mn uncontrollable; on the other hand, a large viscosity will limit the movement of the chain segments, causing the carbocation to be embedded, and the carbocation cannot contact the monomer for chain growth, and finally terminates to form oligomers, making Mn difficult to regulate. In summary, from the perspective of process adjustment, adjusting the viscosity of the polymerization system can solve the above problem of uncontrollable Mn. Therefore, from the process perspective, by controlling the dropping rate and the viscosity of the system, Mw and Mn can be regulated, so as to produce a resin with a controllable softening point.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (1) The present invention sets different monomer dropping rates to control the contact concentration between the carbocation and the monomer during the active maintenance stage. The faster the dropping rate, the more chain growth can be carried out by the carbocation at the end of the chain segment during the active maintenance stage, so as to control the Mw of the resin, and further control the softening point of the resin at 80°C - 140°C;

[0028] (2) By maintaining the polymerization system within a certain viscosity range, on the one hand, it can avoid the poor heat dispersion inside the polymerization system at high viscosity, thus avoiding the uncontrollable Mn caused by the increased chain transfer and chain termination due to the relatively high local temperature of the system; on the other hand, it can avoid the hindrance of the molecular chain segments caused by high viscosity, thereby reducing the collision probability between the carbocation and the monomer, and finally avoiding the problem of uncontrollable Mn. Through an on-line viscometer, the viscosity range of the system is controlled at 150 CP - 400 CP to control the Mn of the resin, and further control the softening point of the resin at 80°C - 140°C;

[0029] (3) The present invention regulates the Tg of the resin by controlling the softening point of the resin through process adjustment, and further regulates the wet skid resistance of the tire. At the same time, by producing resins with different gradient softening points, the relationship between the softening point and the dispersion degree in rubber can be studied to achieve the purpose of balancing physical properties and dynamic performance. Detailed Embodiments

[0030] The present invention will be introduced in detail below in conjunction with specific embodiments.

[0031] Example 1

[0032] Add 800 kg of xylene and 40 kg of titanium tetrachloride catalyst into the reaction kettle. Cool down to 15 °C through brine, and start to dropwise add the styrene / p-methylstyrene mixed monomer (a total of 2000 kg). Control the dropping rate at 600 L / h, and the dropping temperature fluctuation range is 10 - 20 °C. At the same time, control the system viscosity at 340 - 400 CP. After the dropping is completed, keep the temperature at 10 - 20 °C for heat preservation reaction for 7 h, then distill off the solvent and granulate to obtain resin A.

[0033] The softening point of resin A is 80 °C, and the Tg is 33 °C.

[0034] Example 2

[0035] Add 800 kg of toluene and 40 kg of titanium tetrachloride catalyst into the reaction kettle. Cool down to 15 °C through brine, and start to dropwise add the styrene / p-methylstyrene mixed monomer (a total of 2000 kg). Control the dropping rate at 950 L / h, and the dropping temperature fluctuation range is 10 - 20 °C. At the same time, control the system viscosity at 280 - 340 CP. After the dropping is completed, keep the temperature at 10 - 20 °C for heat preservation reaction for 7 h, then distill off the solvent and granulate to obtain resin B.

[0036] The softening point of resin B is 98 °C, and the Tg is 54 °C.

[0037] Example 3

[0038] Add 800 kg of mesitylene and 40 kg of titanium tetrachloride catalyst into the reaction kettle. Cool down to 15 °C through brine, and start to dropwise add the styrene / p-methylstyrene mixed monomer (a total of 2000 kg). Control the dropping rate at 1200 L / h, and the dropping temperature fluctuation range is 10 - 20 °C. At the same time, control the system viscosity at 220 - 280 CP. After the dropping is completed, keep the temperature at 10 - 20 °C for heat preservation reaction for 7 h, then distill off the solvent and granulate to obtain resin C.

[0039] The softening point of resin C is 124 °C, and the Tg is 76 °C.

[0040] Example 4

[0041] Add 800 kg of mesitylene to the reaction kettle, add 40 kg of titanium tetrachloride catalyst, cool down to 15 °C through brine, start to dropwise add the styrene / p-methylstyrene mixed monomer (a total of 2000 kg), control the dropping rate at 1500 L / h, the dropping temperature fluctuation range is 10 - 20 °C, and at the same time control the system viscosity at 150 - 220 CP. After the dropping is completed, keep the temperature at 10 - 20 °C for heat preservation reaction for 7 h, distill off the solvent and granulate to obtain resin D.

[0042] The softening point of resin D is 134 °C, and the Tg is 84 °C.

[0043] Comparative Example 1

[0044] Add 800 kg of xylene to the reaction kettle, add 40 kg of titanium tetrachloride catalyst, cool down to 15 °C through brine, start to dropwise add the styrene / methylstyrene mixed monomer (a total of 2000 kg), control the dropping rate at 500 L / h, the dropping temperature fluctuation range is 10 - 20 °C, and at the same time control the system viscosity at 400 - 470 CP. After the dropping is completed, keep the temperature at 10 - 20 °C for heat preservation reaction for 7 h, distill off the solvent and granulate to obtain resin E.

[0045] The softening point of resin E is 72 °C, and the Tg is 26 °C.

[0046] Comparative Example 2

[0047] Add 800 kg of xylene to the reaction kettle, add 40 kg of titanium tetrachloride catalyst, cool down to 15 °C through brine, start to dropwise add the styrene / methylstyrene mixed monomer (a total of 2000 kg), control the dropping rate at 1600 L / h, the dropping temperature fluctuation range is 10 - 20 °C, and at the same time control the system viscosity at 90 - 150 CP. After the dropping is completed, keep the temperature at 10 - 20 °C for heat preservation reaction for 7 h, distill off the solvent and granulate to obtain resin F.

[0048] The softening point of resin F is 144 °C, and the Tg is 95 °C.

[0049] Example 5: Preparation of rubber composition

[0050] In order to test the application performance of different modified petroleum resins prepared by the present invention, the resins of Comparative Examples 1 - 2 and the cationic polymerization resins prepared in Examples 1, 2, and 3 are selected and added to the rubber. The specific formula is shown in Table 1. Rubber compositions A - E are prepared by mixing.

[0051] The rubber mixing process is as follows:

[0052] Mix according to the following mixing sequence, two-stage mixing:

[0053] First, mixing is carried out in a 2000 mL Haake mixer with a filling coefficient of 0.75, a rotation speed of 60 revolutions, and a temperature of 110 °C. After adding the raw rubber (NR, SSBR, and BR) into the mold cavity and mixing for 60 s, ZnO-80, SA, 4020, 9332F, TDAE, and slip resin are added and mixed for 120 s. Then, 833MP and Si69 are added in two portions with an interval of 60 s, and the mixing time is 300 s. After that, the mixed rubber is taken out. It is passed through the two-roll mill thinly for 4 - 5 times and left to stand for 4 h. A first-stage mixed rubber is obtained.

[0054] The first-stage mixed rubber is placed on a two-roll mill for second-stage mixing in a 2000 mL Haake mixer with a filling coefficient of 0.75, a rotation speed of 60 revolutions, and a temperature of 70 °C. The first-stage mixed rubber, S-80, NS-80, and DPG-80 are added, and the mixing time is 150 s. Then, the mixed rubber is taken out and passed through the two-roll mill thinly for 4 - 5 times to obtain the final mixed rubber. The final mixed rubber is placed on a flat vulcanizer at 160 °C and 15 Mpa for vulcanization, and the vulcanization time is T90, which is obtained from the vulcanization curve. Finally, a rubber composite material is obtained.

[0055] Example 6: Rubber property testing

[0056] The specific method is as follows: The commonly used characterization method for the wet skid resistance of rubber is dynamic thermomechanical analysis (DMA), which is generally carried out by testing the vulcanized rubber using a dynamic mechanical analyzer. In dynamic thermomechanical analysis, the larger the tanδ value at 0 °C, the better the wet skid resistance of the rubber compound; the smaller the tanδ value at 60 °C, the lower the heat generation value of the rubber compound. The specific test results are shown in Table 2.

[0057] Table 1 Rubber composition formula

[0058]

[0059]

[0060] Table 2 Test results of rubber composition properties

[0061]

[0062] For the resins used in Compositions A - E, their softening points and Tg increase in turn. From the application performance data, it can be seen that:

[0063] (1) In terms of processability, the Mooney viscosity of compositions A - E shows an increasing trend, mainly due to the increasing trend of the softening point of the resins used in compositions A - E. As the softening point increases, the longer the molecular chain, and there is a decreasing trend in the plasticizing and lubricating effect on the rubber molecular chain, so the Mooney viscosity shows an increasing trend. Among them, the Mooney viscosity of composition E increases significantly, resulting in a decline in processability. Besides the above reasons, it is mainly because the softening point is too high, leading to uneven dispersion of the resin during the rubber mixing process, thus reducing its plasticizing ability. Although the increase in the resin softening point leads to an increase in the molecular chain length, it is still very small compared to the high - molecular rubber polymer. Therefore, the processability of compositions A - D is basically at the same level.

[0064] (2) In terms of mechanical properties, the modulus at a specified elongation and strength of compositions A - E also basically show an increasing trend with the increase of the resin softening point. The reason is also that the different softening points of the resins lead to differences in plasticizing and lubricating properties, but they are overall at the same level.

[0065] (3) In terms of dynamic properties, with the increase of the resin softening point and Tg, the tanδ at 0℃ first increases and then decreases. The wet - skid resistance of composition C is the best (16% higher than A). The reason is that in the early stage, with the increase of the softening point and Tg, the Tg of the resin composition is also increased, so the wet - skid resistance of the composition is improved; the wet - skid resistance of compositions D and E shows a decreasing trend in the later stage because the softening point is too high, resulting in uneven dispersion of the resin under the same rubber mixing process, so the overall Tg value of the rubber composition decreases, leading to a decreasing trend in the wet - skid resistance of the composition; from the heat - build - up data, it can be seen that with the increase of Tg, the heat - build - up of the composition shows an increasing trend. Among them, the heat - build - up of composition C increases by 5% compared to composition A, and the heat - build - up of compositions D and E increases more significantly. Therefore, considering the dynamic properties comprehensively, composition C has both high wet - skid resistance and low heat - build - up, with the best performance.

[0066] In summary, the resin softening point can affect the processability and mechanical properties, and the trend of property changes shows a regular variation with the trend of the softening point. In terms of dynamic properties, the softening point and Tg of the resin have a comprehensive influence. Dynamic properties reflect driving safety and vehicle - using costs. Therefore, in this patent, the softening point of the resin is regulated by the dropping rate and the viscosity data of the polymerization system, thereby regulating Tg, and regulating the processability, mechanical properties, and dynamic properties of the composition, which is very meaningful for balancing driving safety and vehicle - using costs.

[0067] The above - mentioned embodiments are only for illustrating the technical concept and characteristics of the present invention, and their purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a cationic polymer resin with adjustable softening point, characterized in that: The following steps are involved: 1) Raw material preparation: Add the solvent and catalyst into the reactor, and add the monomer into the high-position dropping tank; 2) Cooling down the polymerization system: Cool the solvent in the reactor to the specified temperature and start adding the monomer from the high-level tank; 3) Control the viscosity of the system and the dripping speed for dripping: set the dripping speed according to the softening point of the target polymer, and monitor the viscosity online. With the continuous dripping of the monomer, the viscosity of the system gradually increases. When the viscosity of the system reaches 150CP, continue to drip the monomer while controlling the viscosity of the system between 150-400CP. When the viscosity is greater than 400CP, the system automatically adds solvent to dilute the reaction solution and controls the viscosity of the system between 150-400CP to adjust the softening point of the resin. The temperature fluctuation range of the whole dripping process is ±5℃; 4) Insulation and granulation: After the dropwise addition is completed, the reaction is insulated. The insulation temperature is consistent with the dropwise addition temperature. The reaction is carried out for 6-10 hours, and then desolventization and granulation are carried out.

2. The method for preparing a cationic polymer resin with adjustable softening point according to claim 1, characterized in that: The solvent is one or a mixture of two or more of toluene, xylene, trimethylbenzene, cyclohexane, dichloroethane or dichloromethane.

3. The method for preparing a cationic polymer resin with adjustable softening point according to claim 2, characterized in that: The initial amount of the solvent used is 40-80 wt % of the monomer.

4. The method for preparing a cationic polymer resin with adjustable softening point according to claim 1, characterized in that: The catalyst is one or a mixture of two or more of sulfuric acid, aluminum trichloride, boron trifluoride, boron trifluoride complex, titanium tetrachloride, boron trichloride and tin tetrachloride.

5. The method for preparing a cationic polymer resin with adjustable softening point according to claim 1, characterized in that: The amount of the catalyst used is 0.3-10 wt % of the monomer.

6. The method for preparing a cationic polymer resin with adjustable softening point according to claim 1, characterized in that: The monomer is one or a mixture of two or more of methyl styrene, p-methyl styrene, styrene, α-methyl styrene, α-pinene or β-pinene.

7. The method for preparing a cationic polymer resin with adjustable softening point according to claim 1, characterized in that: The set dropping speed of the monomer is controlled within the range of 600-1500 L / h, and the dropping speed is maintained at a uniform rate.

8. The method for preparing a cationic polymer resin with adjustable softening point according to claim 1, characterized in that: When the monomer is added dropwise, the temperature is maintained within the range of -10-30°C.

9. The cationic polymer resin obtained by the method according to any one of claims 1 to 8, characterized in that: The resin has a softening point of 80°C-140°C and a Tg value of 33°C-90°C.

10. Use of the cationic polymer resin according to claim 9 in the preparation of rubber.

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