Preparation and hydrogenation method of styrene copolymer

Abstract

According to the preparation and hydrogenation method of the styrene copolymer, the performance of the copolymer is remarkably improved through molecular structure optimization and process improvement. The preparation method comprises the following steps: mixing styrene, alpha-methyl styrene and analogues thereof with cyclohexane in proportion, and polymerizing under the action of an initiator. The hydrogenation method comprises the following steps: dissolving the copolymer in decahydronaphthalene, reacting under the action of a palladium catalyst, and partially or completely saturating a benzene ring into cyclohexyl. The rigidity and regularity of a molecular chain are remarkably enhanced by introducing alpha-position or para-position methyl, and the glass-transition temperature and heat resistance of the copolymer are improved. After hydrogenation modification, the oxidation resistance, the solvent resistance and the chemical stability of the material are remarkably improved, and the toughness and the impact strength are enhanced. The reaction efficiency is improved, the production cost is reduced, and the prepared copolymer and the hydrogenated product thereof can be widely applied to optical materials, structural materials and engineering plastics.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a preparation method of a styrene-based copolymer and a hydrogenation modification method thereof, which are used to improve the heat resistance, oxidation resistance and comprehensive mechanical properties of the styrene-based copolymer. Background Art

[0002] Styrene copolymer is one of the five most widely used general-purpose plastics. It has been widely used due to its excellent performance characteristics, such as high transparency, good insulation, water resistance and corrosion resistance. In addition, its superior coloring and printing properties make it outstanding in appearance design. At the same time, it has good processing fluidity and is easy to shape, which can produce beautiful products. Therefore, polystyrene has been widely used in the fields of electronics, communication equipment, optical instruments, transparent molds, food packaging materials and daily necessities.

[0003] Although styrene copolymers have many advantages, their inherent structural characteristics also lead to some performance deficiencies: such as high brittleness, lack of resistance to environmental stress cracking and solvent erosion; insufficient heat resistance, with a heat deformation temperature of only 70-98°C and a low glass transition temperature (about 105°C); low impact strength and poor antioxidant properties.

[0004] In order to improve these properties, researchers have proposed a variety of modification methods, one of which is to introduce polar functional groups through copolymerization. For example, styrene is copolymerized with monomers containing polar functional groups such as methacrylic acid, maleic anhydride or maleimide. This method can improve heat resistance by adjusting the composition of polar functional group monomers. However, this method has the following problems: when copolymers containing polar functional groups are used in a high temperature environment, due to side reactions of polar groups, the polymer chains are prone to cross-linking reactions, resulting in the formation of gel-like substances, which greatly increases the viscosity of the copolymer and reduces its molding and processing performance.

[0005] Another modification method is to improve the heat resistance by copolymerizing with monomers that do not contain polar functional groups, for example, the copolymer of styrene and α-methylstyrene. The glass transition temperature of this copolymer is higher than that of ordinary polystyrene, thus showing better heat resistance.

[0006] In addition, by hydrogenating styrene copolymers to partially or completely open the large π bonds in the benzene ring, the performance of the material can be significantly improved. For example, hydrogenated styrene copolymers exhibit higher glass transition temperature, stronger antioxidant properties, better heat resistance and regularity, as well as higher crystallinity and lower water absorption. This material overcomes the performance limitations of traditional polystyrene and opens up a new direction for its application in general thermoplastic resins. On this basis, the copolymer of styrene and α-methylstyrene is hydrogenated and modified, and its performance is even better.

[0007] In summary, although the current modification methods have improved the performance of styrene copolymers to a certain extent, there are still problems such as cross-linking and increased viscosity caused by side reactions. At the same time, how to further optimize the hydrogenation process of the copolymer to maximize the improvement of performance is still a technical difficulty. Therefore, it is necessary to provide a preparation method of polystyrene copolymers and a hydrogenation method thereof, aiming to overcome the deficiencies in the existing technology through scientific and reasonable preparation and hydrogenation processes, further improve the heat resistance, oxidation resistance and comprehensive mechanical properties of the material, and open up a new path for the high performance of styrene copolymers. Summary of the invention

[0008] According to the technical problems raised above, a method for preparing a styrene copolymer and a hydrogenation method thereof are provided.

[0009] The technical means adopted by the present invention are as follows:

[0010] A method for preparing a styrene-based copolymer comprises the following steps:

[0011] S11, 15-20 ml of styrene, 60-65 ml of α-methylstyrene and 10-30 ml of cyclohexane are purified by vacuum distillation and then added into a reaction kettle according to a preset ratio;

[0012] S12, adding a certain amount of initiator, heating to 30-150°C and stirring to react;

[0013] S13, after the reaction is completed, degassed methanol is added as a terminator;

[0014] S14. The polymerization solution is repeatedly eluted and dissolved to obtain a styrene copolymer.

[0015] Furthermore, the α-methylstyrene can be replaced by p-methylstyrene, m-methylstyrene, o-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene, p-ethylstyrene, m-ethylstyrene, o-ethylstyrene, and 1,1-diphenylethylene.

[0016] Furthermore, in step S12, the initiator is at least one of n-butyl lithium, tert-butyl lithium or sec-butyl lithium, and the added amount is 0.001-0.01 mol.

[0017] Furthermore, in step S12, the reaction temperature is 30-150° C., and the reaction time is 2-3 hours.

[0018] Furthermore, the amount of degassed methanol added is 2 ml, ethanol is used for polymer elution, and dichloromethane is used for dissolution.

[0019] The present invention also provides a method for hydrogenating a styrene copolymer, comprising the following steps:

[0020] S21, taking 1-20 g of the styrene copolymer prepared by the above preparation method and dissolving it in 80-120 ml of decahydronaphthalene;

[0021] S22, adding palladium catalyst (Pd / C) and placing in a high pressure reactor;

[0022] S23, replacing the air in the kettle with hydrogen, pressurizing it to 3-15 MPa, and setting the reaction temperature to 150-250°C;

[0023] S24. When the pressure stops decreasing, the heating is stopped and the temperature is lowered, and the copolymer is washed and dried to obtain a hydrogenated styrene copolymer.

[0024] Furthermore, the hydrogen pressure range is 5-8 MPa.

[0025] Furthermore, the reaction temperature is 160-200°C.

[0026] Furthermore, the amount of the palladium catalyst used is 0.1%-0.5% of the mass of the styrene copolymer.

[0027] Furthermore, the hydrogenation degree of the prepared hydrogenated styrene-based copolymer reaches more than 90%, and part or all of the benzene rings in the copolymer are saturated to a cyclohexane structure.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1. The present invention uses α-methylstyrene or p-methylstyrene, m-methylstyrene or o-methylstyrene as comonomers, and its molecular structure significantly enhances the rigidity of the molecular chain by introducing α-methyl or p-methyl. Among them, α-methylstyrene limits the free movement of the chain segments by increasing the steric hindrance of the main chain of the molecular chain; and p-methylstyrene improves the substitution symmetry of the benzene ring due to the introduction of the p-methyl, thereby enhancing the regularity of the molecular chain. These structural characteristics jointly increase the glass transition temperature (Tg) of the polystyrene copolymer, so that the copolymer exhibits excellent heat resistance and can adapt to the application requirements of high temperature environments.

[0030] 2. The hydrogenation reaction used in the present invention partially or completely saturates the benzene ring structure into cyclohexyl groups, eliminating the double bond structure of the benzene ring and making the molecule more stable. This modification effectively reduces the risk of polymer degradation under oxidative conditions, thereby improving the material's antioxidant capacity.

[0031] 3. The hydrogenated polymer of the present invention significantly reduces the interaction with polar solvents due to the non-polar characteristics of cyclohexyl groups, thereby enhancing its solvent resistance. At the same time, the stability of the saturated structure improves the chemical stability of the material in acidic, alkaline and oxidative environments, making it suitable for harsh chemical conditions.

[0032] 4. After hydrogenation, the brittle characteristics of the benzene ring are eliminated, and the flexibility of the molecular chain is enhanced, which significantly improves the toughness and impact strength of the copolymer and expands its application in fields with high mechanical performance requirements.

[0033] In summary, by optimizing the molecular structure, the copolymer prepared by the present invention has a high glass transition temperature, excellent chemical stability and mechanical properties, making it widely applicable to the fields of high-temperature structural materials, chemical corrosion-resistant packaging materials and high-performance engineering plastics. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] 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, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0035] Figure 1 It is a curve diagram showing the change of hydrogenation degree with pressure in the present invention.

[0036] Figure 2 It is a curve diagram showing the change of hydrogenation degree with temperature in the present invention. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] The present invention provides a method for preparing a styrene copolymer, comprising the following steps:

[0039] S11, 15-20ml styrene, 60-65ml α-methylstyrene (the α-methylstyrene can be Replaced with p-methylstyrene, m-methylstyrene, o-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene, p-ethylstyrene, m-ethylstyrene, o-ethylstyrene, 1,1-diphenylethylene) and 10-30 ml of cyclohexane are refined by vacuum distillation and then added into the reactor according to a preset ratio;

[0040] S12, adding 0.001-0.01 mol of an initiator, heating to 30-150° C. and stirring for reaction; the initiator is at least one of n-butyl lithium, tert-butyl lithium or sec-butyl lithium; the reaction temperature is 30-150° C., and the reaction time is 2-3 hours;

[0041] S13, after the reaction is completed, add 2 ml of degassed methanol as a terminator;

[0042] S14. The polymerization solution is repeatedly eluted and dissolved, ethanol is used for polymer elution, and dichloromethane is used for dissolution, to obtain a styrene copolymer.

[0043] The present invention also discloses a method for hydrogenating a styrene copolymer, comprising the following steps:

[0044] S21, taking 1-20 g of the styrene copolymer prepared by the above preparation method and dissolving it in 80-120 ml of decahydronaphthalene;

[0045] S22, adding palladium catalyst (Pd / C) and placing in a high pressure reactor; the amount of the palladium catalyst is 0.1%-0.5% of the mass of the polystyrene copolymer;

[0046] S23, replace the air in the kettle with hydrogen, pressurize to 3-15MPa, preferably 5-8MPa, set the reaction temperature to 150-250°C, preferably 160-200°C; (such as Figure 1 and Figure 2 As shown, the trend of hydrogenation degree changing with pressure and temperature is given)

[0047] S24. When the pressure stops decreasing, the heating is stopped and the temperature is lowered, and the copolymer is cleaned and dried to obtain a hydrogenated styrene copolymer. The degree of hydrogenation of the prepared hydrogenated styrene copolymer reaches more than 90%, and part or all of the benzene rings in the copolymer are saturated to a cyclohexane structure.

[0048] Example 1

[0049] 20 mL of styrene, 60 mL of α-methylstyrene and 20 mL of cyclohexane were added to the reactor, and then 0.01 mol of n-butyl lithium was added, heated to 62°C and stirred for 3 hours. After the reaction, 2 mL of degassed methanol was added. The polymerization solution was repeatedly eluted with ethanol and dissolved in dichloromethane, and dried to obtain a copolymer of styrene and α-methylstyrene.

[0050] Example 2

[0051] 15 mL of styrene, 65 mL of α-methylstyrene and 25 mL of cyclohexane were added to the reactor, and then 0.005 mol of n-butyl lithium was added, heated to 62°C and stirred for 3 hours. After the reaction, 2 mL of degassed methanol was added. The polymerization solution was repeatedly eluted with ethanol and dissolved in dichloromethane, and dried to obtain a copolymer of styrene and α-methylstyrene.

[0052] Example 3

[0053] 20 mL of styrene, 60 mL of α-methylstyrene and 15 mL of cyclohexane were added to the reactor, and then 0.008 mol of n-butyl lithium was added, heated to 75°C and stirred for 2 hours. After the reaction, 2 mL of degassed methanol was added. The polymerization solution was repeatedly eluted with ethanol and dissolved in dichloromethane, and dried to obtain a copolymer of styrene and α-methylstyrene.

[0054] Example 4

[0055] 8 g of the copolymer was dissolved in 100 mL of decahydronaphthalene, and added to a high-pressure reactor with 0.1 g of palladium catalyst (Pd / C). The air in the reactor was replaced with hydrogen, and the hydrogen was pressurized to 5 MPa. The temperature was set to 160°C. When the pressure no longer dropped, the heating was stopped and the temperature was lowered. The copolymer was washed and dried to obtain a hydrogenated polystyrene copolymer.

[0056] Example 5

[0057] Take 10g of the copolymer and dissolve it in 100mL of decahydronaphthalene, add it into a high-pressure reactor with 0.1g of palladium catalyst (Pd / C), replace the air in the reactor with hydrogen, pressurize the hydrogen to 8MPa, set the temperature to 160°C, stop heating and cool when the pressure no longer drops, wash and dry the copolymer, and obtain a hydrogenated polystyrene copolymer.

[0058] Example 6

[0059] Take 6 g of the copolymer and dissolve it in 100 mL of decahydronaphthalene, add it into a high-pressure reactor with 0.1 g of palladium catalyst (Pd / C), replace the air in the reactor with hydrogen, pressurize the hydrogen to 5 MPa, set the temperature to 200°C, stop heating and cool when the pressure no longer drops, wash and dry the copolymer, and obtain a hydrogenated polystyrene copolymer.

[0060] Comparative Example 1

[0061] 20 mL of styrene, 60 mL of p-methylstyrene and 15 mL of cyclohexane were added to the reactor, and then 0.008 mol of n-butyl lithium was added, heated to 75°C and stirred for 2 hours. After the reaction, 2 mL of degassed methanol was added. The polymerization solution was repeatedly eluted with ethanol and dissolved in dichloromethane, and dried to obtain a copolymer of styrene and p-methylstyrene.

[0062] Comparative Example 2

[0063] Take 10g of polystyrene and dissolve it in 100mL of decahydronaphthalene, add it into a high-pressure reactor with 0.1g of palladium catalyst (Pd / C), replace the air in the reactor with hydrogen, pressurize the hydrogen to 5MPa, set the temperature to 160°C, stop heating and cool when the pressure no longer drops, wash and dry the copolymer, and obtain a hydrogenated polystyrene copolymer.

[0064] The following test conditions were used to test the effects of the above Examples 1-6 and Comparative Examples 1 and 2:

[0065] The glass transition temperature is measured in accordance with the national standard GB / T 40396-2021 “Determination of the glass transition temperature of polymer materials” using a differential scanning calorimeter (DSC).

[0066] The light transmittance is measured in accordance with the national standard GB / T 2410-2008 “Determination of light transmittance and haze of transparent plastics”.

[0067] The melt index is tested according to the method in the national standard GBT 3682-2018 "Determination of Melt Flow Rate of Thermoplastic Plastics".

[0068] The elongation at break is measured in accordance with ASTM D638 “Standard Test Method for Tensile Properties of Plastics”.

[0069] Degree of hydrogenation: The content of benzene rings in the solution before and after the hydrogenation reaction is measured using a UV-spectrophotometer to calculate the conversion rate of the reaction.

[0070] Table 1 Performance test data of each embodiment and comparative example

[0071]

[0072] It can be seen from the data in Table 1 that with the optimization of the preparation conditions and the adjustment of the molecular structure, Tg is gradually increased from 122°C in Example 1 to 165°C in Example 6, which reflects that the present invention improves the rigidity and regularity of the molecular chain and enhances the heat resistance by introducing α-methylstyrene or its analogues.

[0073] The light transmittance is between 89% and 91%, which is close to or even higher than that of the comparative example, indicating that the copolymer prepared by the present invention can maintain high heat resistance while taking into account excellent optical properties.

[0074] The melt index ranges from 2.8 g / 10 min to 3.6 g / 10 min. Compared with Comparative Example 1, the performance is more balanced. The precise control of the reaction conditions and the amount of catalyst used in the invention avoids the problem of decreased processing performance caused by the excessively high melt index (5.2 g / 10 min) in Comparative Example 2.

[0075] The elongation at break gradually increased from 60% (Example 1) to 90% (Example 6), which is significantly higher than the comparative example. This shows that saturating the benzene ring structure to cyclohexyl groups through hydrogenation not only improves the toughness and flexibility of the material, but also expands its application field.

[0076] The hydrogenation degrees of Examples 4-6 reached 91%, 93% and 95%, respectively, which are much higher than those of the comparative example, indicating that the hydrogenation method of the present invention can significantly improve the degree of hydrogenation, eliminate the double bond structure of the benzene ring, and enhance the chemical stability and weather resistance of the material.

[0077] In summary, the present invention synthesizes a copolymer of styrene and α-methylstyrene by a one-step method, which is easy to operate; the hydrogenation method is used to further improve its performance, that is, by optimizing the molecular structure and reaction conditions, the glass transition temperature, melt flow rate, toughness and chemical stability of the styrene copolymer are significantly improved, while maintaining excellent optical properties and processing properties. Compared with the comparative example, the material of the present invention is more suitable for high temperature, high mechanical strength and chemical corrosion resistance, and shows a wide range of industrial application prospects.

[0078] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, a person of ordinary skill in the art should understand that any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a styrene copolymer, characterized in that: The following steps are involved: S11, 15-20 ml of styrene, 60-65 ml of α-methylstyrene and 10-30 ml of cyclohexane are purified by vacuum distillation and then added into a reaction kettle according to a preset ratio; S12, adding a certain amount of initiator, heating to 30-150°C and stirring to react; S13, after the reaction is completed, degassed methanol is added as a terminator; S14. The polymerization solution is repeatedly eluted and dissolved to obtain a styrene copolymer.

2. The preparation method according to claim 1, characterized in that: The α-methylstyrene can be replaced by p-methylstyrene, m-methylstyrene, o-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene, p-ethylstyrene, m-ethylstyrene, o-ethylstyrene, and 1,1-diphenylethylene.

3. The preparation method according to claim 1, characterized in that: In the step S12, the initiator is at least one of n-butyl lithium, tert-butyl lithium or sec-butyl lithium, and the added amount is 0.001-0.01 mol.

4. The preparation method according to claim 1, characterized in that: In the step S12, the reaction temperature is 30-150° C. and the reaction time is 2-3 hours.

5. The preparation method according to claim 1, characterized in that: The amount of degassed methanol added was 2 ml, ethanol was used for polymer elution, and dichloromethane was used for dissolution.

6. A method for hydrogenating a styrene copolymer, characterized in that: The following steps are involved: S21, taking 1-20 g of the styrene copolymer prepared by the preparation method according to any one of claims 1 to 5 and dissolving it in 80-120 ml of decahydronaphthalene; S22, adding palladium catalyst (Pd / C) and placing in a high pressure reactor; S23, replacing the air in the kettle with hydrogen, pressurizing it to 3-15 MPa, and setting the reaction temperature to 150-250°C; S24. When the pressure stops decreasing, the heating is stopped and the temperature is lowered, and the copolymer is washed and dried to obtain a hydrogenated styrene copolymer.

7. The hydrogenation method according to claim 6, characterized in that The hydrogen pressure range is 5-8 MPa.

8. The hydrogenation method according to claim 6, characterized in that The reaction temperature is 160-200°C.

9. The hydrogenation method according to claim 6, characterized in that The dosage of the palladium catalyst is 0.1%-0.5% of the mass of the styrene copolymer.

10. The hydrogenation method according to claim 9, characterized in that The hydrogenation degree of the prepared hydrogenated styrene-based copolymer reaches more than 90%, and part or all of the benzene rings in the copolymer are saturated to a cyclohexane structure.

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