Titanocene catalyst, preparation method and application thereof

Abstract

The present invention discloses a titanocene catalyst, a preparation method and an application thereof, and belongs to the field of catalyst technology. The structural formula of the titanocene catalyst provided by the present invention is shown in the following formula (I): In formula (I), R1 is a cyclopentadienyl group or a cyclopentadienyl group substituted by 1 to 5 C1 to C4 alkyl groups; R2 is a C6 to 10 aryl group; n1 is 1 to 5, and n2 is 0 to 4. The titanocene catalyst of the present invention adopts a trivalent titanium structure substituted with F or more. F has a strong polarization effect, which gives the catalyst high polymerization activity. The titanium in the catalyst is trivalent titanium, so there is no need to introduce a reducing co-catalyst, which is beneficial to reducing the co-catalyst content in the polymerization system, thereby effectively reducing the ash content in the product, and obtaining a syndiotactic polystyrene product with good comprehensive properties such as color, crystallinity, electrical properties and service life.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and in particular relates to a titanocene catalyst and a preparation method and application thereof. Background Art

[0002] In 1986, Ishihara et al. reported the synthesis of a new semi-crystalline form of polystyrene. Through a series of relevant characterizations, they found that the structure of this new polystyrene was different from that of atactic and isotactic polystyrene, confirming the first synthesis of syndiotactic polystyrene (sPS). Due to the excellent properties of sPS, such as heat resistance, solvent resistance, dimensional stability, and high crystallization rate, sPS was quickly commercialized and subsequently attracted widespread attention as a new type of thermoplastic engineering plastic. The synthesis of sPS generally uses metallocene compounds as the main catalyst. To improve the polymerization activity and the syndiotacticity of the product, co-catalysts alkylaluminoxane (such as methylaluminoxane MAO) and alkoxyaluminum (such as triisobutylaluminum TIBA) are also required during the polymerization. The catalytic activity of the metallocene compound used as the main catalyst is Ti>Zr>Hf, and titanium-based metallocene compounds have the highest polymerization activity and the highest synergy. The catalytic mechanism of titanium metallocene compounds is that the tetravalent titanocene compound (such as Cp*TiR3, R is the auxiliary ligand of the main catalyst) is reduced to trivalent titanium by TIBA, and then MAO alkylates it to form [Cp*TiCH3] + [RMAO] - Ion pair, followed by syndiotactic insertion of styrene into the titanium-carbon bond to obtain sPS. Therefore, TIBA reduces tetravalent titanium to trivalent titanium, providing the prerequisite for the formation of active centers. MAO alkylates trivalent titanium to form [RMAO] - The anion stabilizes the active centers of the trivalent titanium cation. In other words, the interaction between the primary catalyst and the cocatalyst determines the number and stability of the active centers formed, thereby affecting the polymerization activity, product syndiotacticity, and molecular weight (including molecular weight distribution) in syndiotactic styrene polymerization.

[0003] The catalyst components introduced during the syndiotactic polymerization of styrene will remain in the polyolefin product as solids, forming "ash." Post-processing to remove these catalyst components is often tedious and inefficient. Ash is used to describe residual catalyst, and is defined as the mass ratio of residual inorganic oxides after polymer calcination to the original material. For example, a titanium-based metallocene compound as the primary catalyst will form TiO2 upon calcination, while co-catalysts such as MAO and TIBA will form Al2O3 upon calcination. Ash content directly impacts the performance and application of sPS materials. It not only affects the color, crystallinity, and electrical properties of the sPS product, but the metal components in the ash can also accelerate oxidation and degradation of the sPS, impacting product performance and lifespan. According to GB / T9345.1-2008, an ash content of 100 ppm or greater is considered high, 60-100 ppm as medium, 35-60 ppm as low, and 20 ppm or less as ultra-low. Currently, there are no reports on the direct synthesis of sPS with low ash content. Summary of the Invention

[0004] In order to overcome at least one of the problems existing in the above-mentioned prior art, one of the objects of the present invention is to provide a titanocene catalyst, which has high catalytic activity, requires a small amount of co-catalyst, and the syndiotactic polystyrene produced by using the titanocene catalyst has a high yield and a low ash content.

[0005] A second object of the present invention is to provide a method for preparing the titanocene catalyst.

[0006] A third object of the present invention is to provide a catalyst composition comprising the above titanocene catalyst.

[0007] A fourth object of the present invention is to provide a method for preparing syndiotactic polystyrene.

[0008] A fifth object of the present invention is to provide syndiotactic polystyrene obtained by the above preparation method.

[0009] A sixth object of the present invention is to provide an application of the above-mentioned syndiotactic polystyrene in the fields of battery separators, capacitor films, baby products or household appliances.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is:

[0011] The first aspect of the present invention provides a titanocene catalyst, the structural formula of which is shown in formula (I):

[0012]

[0013] In formula (I), R1 is a cyclopentadienyl group or a cyclopentadienyl group substituted with 1 to 5 C1 to C4 alkyl groups; R2 is a C6 to C10 aryl group; n1 is 1 to 5, and n2 is 0 to 4;

[0014] The inventive concept of the present invention is that, from the perspective of polymerization mechanism, in order to reduce the amount of catalyst components remaining in the sPS, it is necessary to find a more efficient catalytic system. Using less catalyst components can produce more product, thereby reducing ash content. Therefore, the present invention introduces F as a coligand in the titanocene catalyst. This is because F has a strong electronegativity and a strong polarization effect, which facilitates F's replacement by MAO, thereby producing more [Cp*TiCH3] + [RMAO] - Active centers are formed to improve polymerization activity. On the other hand, in the catalyst composition used for syndiotactic polystyrene, the amount of main catalyst used is the smallest, and the largest proportion of the ash is the co-catalyst residue (such as alkylaluminoxane and aluminum alkoxide). Considering the effects and disadvantages of alkylaluminoxane and aluminum alkoxide, the present invention designs a titanocene catalyst containing trivalent titanium as the main catalyst. Without the need for the reducing effect of aluminum alkoxide, it can be combined with the alkylaluminoxane co-catalyst to carry out alkylation, thereby greatly saving the amount of co-catalyst used, achieving the purpose of reducing the ash content in the product and improving product performance.

[0015] In some specific embodiments of the present invention, in formula (I), R1 is a cyclopentadienyl group substituted by 1 to 5 C1 to C4 alkyl groups; in some more specific embodiments of the present invention, R1 is a cyclopentadienyl group substituted by 3 to 5 C1 to C2 alkyl groups; in some embodiments of the present invention, R1 is a pentamethylcyclopentadienyl group.

[0016] In some specific embodiments of the present invention, in formula (I), R2 is a C6-C8 aryl group; in some more specific embodiments of the present invention, R2 is a phenyl group, a methylphenyl group or an ethylphenyl group; in some embodiments of the present invention, R2 is a phenyl group.

[0017] In some specific embodiments of the present invention, in formula (I), n1+n2=5.

[0018] In some embodiments of the present invention, R2 of the titanocene catalyst is a phenyl group, and the H on the phenyl group is substituted by 1 to 5 F groups to form a F-monosubstituted, disubstituted, trisubstituted, tetrasubstituted or pentasubstituted benzene structure, and the specific substitution position can be arbitrary.

[0019] In some embodiments of the present invention, in formula (I), R1 is pentamethylcyclopentadienyl; R2 is phenyl; n1 is 1 to 5, n2 is 0 to 4, and n1+n2=5.

[0020] In some specific embodiments of the present invention, the structural formula of the titanocene catalyst is shown in the following formulas (1) to (5):

[0021]

[0022] The second aspect of the present invention provides a method for preparing the titanocene catalyst according to the first aspect of the present invention, comprising the following steps: reacting a compound represented by formula (II) in the presence of an organic lithium compound and an organic silicon compound to obtain the titanocene catalyst;

[0023]

[0024] R1, R2, n1, and n2 in formula (II) are defined the same as those in formula (I).

[0025] In some specific embodiments of the present invention, the organic lithium compound includes at least one of tert-butyl lithium, n-butyl lithium, isobutyl lithium, benzyl lithium or lithium diisopropylamide; in some more specific embodiments of the present invention, the organic lithium compound includes at least one of tert-butyl lithium, n-butyl lithium or isobutyl lithium; in some examples of the present invention, the organic lithium compound is selected from tert-butyl lithium.

[0026] In some specific embodiments of the present invention, the organosilicon compound includes at least one of trimethylchlorosilane, trimethylsilanol, trimethylsilyl ether, trimethylsilyl ester or trimethylsilylamine; in some more specific embodiments of the present invention, the organosilicon compound includes at least one of trimethylchlorosilane, trimethylsilanol or trimethylsilyl ether; in some embodiments of the present invention, the organosilicon compound is selected from trimethylchlorosilane.

[0027] In some specific embodiments of the present invention, the molar ratio of the compound represented by formula (II) to the organic lithium compound is 1: (0.5 to 2.5); in some more specific embodiments of the present invention, the molar ratio of the compound represented by formula (II) to the organic lithium compound is 1: (0.8 to 2.2); in some embodiments of the present invention, the molar ratio of the compound represented by formula (II) to the organic lithium compound is 1: (1 to 2).

[0028] In some specific embodiments of the present invention, the molar ratio of the compound represented by formula (II) to the organosilicon compound is 1:(0.8~3); in some more specific embodiments of the present invention, the molar ratio of the compound represented by formula (II) to the organosilicon compound is 1:(1~2.5); in some embodiments of the present invention, the molar ratio of the compound represented by formula (II) to the organosilicon compound is 1:(1.2~2.2).

[0029] In some specific embodiments of the present invention, the temperature of the redox reaction is -100 to 10°C; in some more specific embodiments of the present invention, the temperature of the redox reaction is -90 to 5°C; in some examples of the present invention, the temperature of the redox reaction is -80 to 0°C.

[0030] In some specific embodiments of the present invention, the oxidation-reduction reaction time is 1 to 20 hours; in some more specific embodiments of the present invention, the oxidation-reduction reaction time is 1.5 to 15 hours; in some examples of the present invention, the oxidation-reduction reaction time is 2 to 12 hours.

[0031] In the present invention, the compound represented by formula (II) can be obtained by conventional existing techniques and is therefore not particularly limited.

[0032] As an example, the compound represented by formula (II) of the present invention can be obtained by reacting trimethoxytitanium containing an R1 group with a fluorine-substituted compound containing an R2 group, followed by recrystallization.

[0033] In some specific embodiments of the present invention, the molar ratio of the trimethoxytitanium containing R1 group to the fluorine-substituted compound containing R2 group is 1:(3-3.5); further 1:(3.1-3.2).

[0034] In some specific embodiments of the present invention, the temperature for reacting the trimethoxytitanium containing an R1 group with the fluorine-substituted compound containing an R2 group is -75 to 5°C; further -80 to 0°C.

[0035] In some specific embodiments of the present invention, the reaction time of the trimethoxytitanium containing an R1 group and the fluorine-substituted compound containing an R2 group is 1 to 15 hours; further 2 to 12 hours.

[0036] In some specific embodiments of the present invention, the trimethoxytitanium containing an R1 group reacts with the fluorine-substituted compound containing an R2 group in a solvent; a non-limiting example of the solvent is dichloromethane.

[0037] In some specific embodiments of the present invention, after the trimethoxytitanium containing an R1 group reacts with the fluorine-substituted compound containing an R2 group in a solvent, the solvent used for recrystallization is a mixed solvent of dichloromethane and n-hexane.

[0038] In some specific embodiments of the present invention, the trimethoxytitanium containing R1 group is selected from pentamethylcyclopentadienyltrimethoxytitanium.

[0039] In some embodiments of the present invention, the fluorine-substituted compound containing an R2 group includes pentafluorophenol, 4-fluorophenol, 2,4-difluorophenol, 2,4,6-trifluorophenol or 2,3,4,6-tetrafluorophenol.

[0040] The third aspect of the present invention provides a catalyst composition comprising an alkylaluminoxane and the titanocene catalyst according to the first aspect of the present invention, wherein the structural formula of the alkylaluminoxane is shown in the following formula (III):

[0041]

[0042] In formula (III), R3 is a C1-C4 alkyl group; n3 is 6-40.

[0043] In some specific embodiments of the present invention, in formula (III), R3 is methyl, ethyl, or propyl; in some embodiments of the present invention, R3 is methyl. When R3 is methyl, the resulting compound of formula (III) is methylaluminoxane (MAO).

[0044] In some specific embodiments of the present invention, in formula (III), n3 is 10-30.

[0045] In some specific embodiments of the present invention, the molar ratio of Ti in the titanocene catalyst to Al in the alkylaluminoxane is (10-2000):1; in some more specific embodiments of the present invention, the molar ratio of Ti in the titanocene catalyst to Al in the alkylaluminoxane is (30-800):1; in some embodiments of the present invention, the molar ratio of Ti in the titanocene catalyst to Al in the alkylaluminoxane is (50-200):1.

[0046] The fourth aspect of the present invention provides a method for preparing syndiotactic polystyrene, comprising the following steps: subjecting a polymerization system containing a styrene monomer and the catalyst composition according to the third aspect of the present invention to a polymerization reaction to obtain the syndiotactic polystyrene.

[0047] In some specific embodiments of the present invention, the polymerization reaction temperature is 0-100°C; in some more specific embodiments of the present invention, the polymerization reaction temperature is 30-95°C; in some embodiments of the present invention, the polymerization reaction temperature is 50-90°C; non-limiting examples include 60°C, 70°C or 80°C.

[0048] In some specific embodiments of the present invention, the polymerization reaction time is 0.01 to 10 hours; in some more specific embodiments of the present invention, the polymerization reaction time is 0.05 to 5 hours; in some embodiments of the present invention, the polymerization reaction time is 0.1 to 2 hours; non-limiting examples include 0.h, 1h or 1.5h.

[0049] In some specific embodiments of the present invention, the concentration of the titanocene catalyst in the polymerization system is 10 -9 ~10 -3 mol / L; In some more specific embodiments of the present invention, in the polymerization system, the concentration of the titanocene catalyst is 10 -9 ~10 -7 mol / L; In some embodiments of the present invention, the concentration of the titanocene catalyst in the polymerization system is (0.5-1.5)×10 -8 mol / L.

[0050] The fifth aspect of the present invention provides a syndiotactic polystyrene prepared by the preparation method described in the fourth aspect of the present invention, wherein the ash content of the syndiotactic polystyrene is 30 to 150 ppm.

[0051] In some specific embodiments of the present invention, the ash content of the syndiotactic polystyrene is 35-120 ppm; in some more specific embodiments of the present invention, the ash content of the syndiotactic polystyrene is 40-100 ppm; in some embodiments of the present invention, the ash content of the syndiotactic polystyrene is 50-70 ppm.

[0052] The ash content of the syndiotactic polystyrene of the present invention refers to the mass ratio of the residual inorganic oxides in the calcined product of the syndiotactic polystyrene to the syndiotactic polystyrene before calcination, and is more specifically measured according to GB / T 9345.1-2008.

[0053] The sixth aspect of the present invention provides a use of the syndiotactic polystyrene according to the fifth aspect of the present invention in the fields of battery separators, capacitor films, baby products or household appliances.

[0054] The syndiotactic polystyrene obtained by the method of the present invention has a low ash content, and the product obtained has good color, crystallinity, electrical properties and service life, and can be applied to the manufacturing fields such as battery separators, capacitor films, baby products, and household appliances. For example, for capacitor films, polymer film is an insulating film as an insulating film between two conductors, and the catalyst ash residue in the polymer film can cause the electron density interference between the polymer main chain and the charge carriers, and the electrical conductivity is significantly increased, generating a large amount of heat so that the capacitor heats up. The temperature rise in the capacitor can increase the carrier concentration and accelerate the carrier mobility to cause the dielectric loss to increase, further aggravating the breakdown of the polymer film, and the breakdown strength is significantly reduced. During long-term operation, the polymer film is affected by the electric thermal field and breaks down, which can cause the capacitor capacity and life to decrease. This is an important reason for the failure or even explosion of the capacitor. And even if an antioxidant is added in the processing stage, the residual catalyst component in the polymer can also significantly promote the thermal oxidation degradation reaction, and produce a large number of chemical defects, causing the dielectric breakdown performance of the polymer to significantly deteriorate, increasing the probability of insulation failure. Therefore, introducing minimal catalyst components during the polymer synthesis stage and reducing catalyst residues are of great significance to the safety and reliability of polymers entering the high-end application market.

[0055] The beneficial effects of the present invention are as follows: the titanocene catalyst of the present invention adopts a trivalent titanium structure with F being monosubstituted or polysubstituted, F having a strong polarization effect, which gives the catalyst high polymerization activity, and the titanium in the catalyst is trivalent titanium, so there is no need to introduce a co-catalyst with reducing properties, which is beneficial to reducing the co-catalyst content in the polymerization system, thereby effectively reducing the ash content in the product, and obtaining a syndiotactic polystyrene product with comprehensive properties such as good color, crystallinity, electrical properties and service life.

[0056] Specifically, compared with the prior art, the present invention has the following advantages:

[0057] 1. Compared with other auxiliary ligands, the titanocene catalyst in the present invention is a trivalent titanium monotitanocenes compound substituted with F or more, and the catalyst composition formed by combining it with alkylaluminoxane has extremely high catalytic activity and can produce high yield of syndiotactic polystyrene.

[0058] 2. The titanocene catalyst of the present invention can effectively reduce the amount of alkylaluminoxane (such as MAO) used in the syndiotactic polystyrene polymerization system, and does not require the additional addition of alkylaluminum (such as TIBA) as a reducing agent, greatly reducing the residual catalyst components in the product and the ash content. The synthesized syndiotactic polystyrene has a low ash content.

[0059] 3. The amount of expensive alkylaluminoxane used in the catalyst composition of the present invention is greatly reduced, which effectively reduces the production cost of syndiotactic polystyrene. The obtained syndiotactic polystyrene has good comprehensive properties such as color, crystallinity, electrical properties and service life, and has a wide range of applications in battery separators, capacitor films, baby products or household appliances. DETAILED DESCRIPTION

[0060] The content of the present invention is further described in detail below through specific examples. It should be understood that the following examples are only used to further illustrate the present invention and cannot be interpreted as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the principles set forth in the present invention all fall within the scope of protection of the present invention. The specific process parameters and the like in the following examples are only examples within a suitable range, and those skilled in the art can make selections within a suitable range through the description herein, and are not limited to the specific data exemplified below. The raw materials, reagents or devices used in the following examples and comparative examples, unless otherwise specified, can be obtained from conventional commercial sources, or can be obtained by existing known methods.

[0061] In the following examples, application examples and comparative application examples, the compound of formula (III) is selected from methylaluminoxane (MAO).

[0062] Example 1

[0063] A titanocene catalyst, the structural formula of which is shown in formula (1):

[0064]

[0065] The compound represented by formula (1) comprises the following preparation steps:

[0066] In a dry 250 ml two-necked flask, nitrogen was evacuated three times, and 60 ml of anhydrous dichloromethane containing 1.0 g (3.6 mmol) of pentamethylcyclopentadienyltrimethoxytitanium was added. Then, a 60 ml anhydrous dichloromethane solution containing 1.26 g (11.2 mmol) of 4-fluorophenol was added dropwise over the solution. The mixture was allowed to drip over the solution over 40 minutes. After reacting at -80°C for 2 hours, the temperature was slowly raised to room temperature. The solvent was removed by distillation under reduced pressure, and the mixture was washed three times with anhydrous n-hexane and dried. The mixture was recrystallized three times from a mixed solution of anhydrous dichloromethane and anhydrous n-hexane and dried to obtain 1.70 g of yellow crystals with a yield of 92%.

[0067] 1.70 g (3.3 mmol) of the yellow crystals were added to a dry 250 ml two-necked flask. The flask was purged with nitrogen three times, and 45 ml of anhydrous dichloromethane was added to dissolve the crystals. The flask was cooled to -80°C, and 2.5 ml (3.3 mmol) of tert-butyl lithium was added. After stirring for 2 hours, a solution of 0.44 g (4.0 mmol) of trimethylsilyl chloride dissolved in 15 ml of anhydrous dichloromethane was added. The temperature was then slowly raised to room temperature, filtered, and the solvent was removed by distillation under reduced pressure. The crystals were washed three times, recrystallized, and dried to isolate red crystals (yield 52%) for use in the present invention.

[0068] The elemental analysis of the red crystals showed that: C 22 H 23 O2F2Ti. Specifically, Calcd.For (theoretical calculated value): C 65.20%, H 5.72%; Found (measured value): C 65.23%, H 5.74%. The structural formula of the compound synthesized in this example is shown in formula (1).

[0069] Application Example 1

[0070] A method for preparing syndiotactic polystyrene comprises the following steps:

[0071] In a dry 50 ml two-necked flask, high-purity nitrogen was pumped out three times, 20 ml of refined styrene monomer was added, and after electromagnetic stirring in a 70°C oil bath for 20 minutes, 0.20 ml of a toluene solution of MAO (wherein, MAO was 0.020 mmol) and 0.20 ml of a toluene solution of the titanocene catalyst prepared in Example 1 (wherein, the titanocene catalyst was 0.0001 mmol, and the aluminum-titanium ratio of MAO to the titanocene catalyst was 200) were injected with a syringe. After reacting for 1 hour, the reaction was terminated with ethanol and dried to obtain 17.1 g of a powdered solid.

[0072] According to GB / T 9345.1-2008, the calcined product has an ash content of 60.1 ppm.

[0073] Example 2

[0074] A titanocene catalyst, the structural formula of which is shown in formula (2):

[0075]

[0076] The compound represented by formula (2) comprises the following preparation steps:

[0077] In a dry 250 ml two-necked flask, nitrogen was evacuated three times, and 60 ml of anhydrous dichloromethane containing 1.0 g (3.6 mmol) of pentamethylcyclopentadienyltrimethoxytitanium was added. Then, a 60 ml dichloromethane solution containing 1.50 g (11.5 mmol) of 2,4-difluorophenol was added dropwise over the mixture. The mixture was allowed to drip over the mixture over the next 40 minutes. After reacting at -30°C for 6 hours, the mixture was slowly heated to room temperature. The solvent was removed by distillation under reduced pressure, and the mixture was washed three times with anhydrous n-hexane and dried. The mixture was recrystallized three times from a mixed solution of anhydrous dichloromethane and anhydrous n-hexane and dried to obtain 1.94 g of yellow crystals with a yield of 94%.

[0078] 1.94 g (3.4 mmol) of the yellow crystals were added to a dry 250 ml two-necked flask. The mixture was purged with nitrogen three times, and then dissolved in 45 ml of anhydrous dichloromethane. The flask was cooled to -30°C, and 3.9 ml (5.1 mmol) of tert-butyl lithium was added. After stirring for 6 hours, a solution of 0.56 g (5.1 mmol) of trimethylsilyl chloride dissolved in 15 ml of anhydrous dichloromethane was added. The mixture was then slowly warmed to room temperature, filtered, and the solvent was removed by distillation under reduced pressure. The mixture was washed three times, recrystallized, and dried to isolate red crystals (yield 60%) for use in the present invention.

[0079] The elemental analysis of the red crystals showed that: C 22 H 21 O2F4Ti. Specifically, Calcd. For (theoretical calculated value): C 59.88%, H 4.80%; Found (measured value): C 59.80%, H 4.74%. The structural formula of the compound synthesized in this example is shown in formula (2).

[0080] Application Example 2

[0081] A method for preparing syndiotactic polystyrene comprises the following steps:

[0082] In a dry 50 ml two-necked flask, high-purity nitrogen was used for 3 pumping, and 20 ml of refined styrene monomer was added. After electromagnetic stirring in a 70°C oil bath for 20 minutes, 0.20 ml of a toluene solution of MAO (wherein, MAO was 0.020 mmol) and 0.26 ml of a toluene solution of the titanocene catalyst prepared in Example 2 (wherein, the titanocene catalyst was 0.00013 mmol, and the aluminum-titanium ratio of MAO to the titanocene catalyst was 150) were injected with a syringe. After reacting for 1 hour, the reaction was terminated with ethanol and dried to obtain 17.2 g of a powdered solid.

[0083] According to GB / T 9345.1-2008, the calcined product has an ash content of 59.9 ppm.

[0084] Example 3

[0085] A titanocene catalyst, the structural formula of which is shown in formula (3):

[0086]

[0087] The compound represented by formula (3) comprises the following preparation steps:

[0088] In a dry 250 ml two-necked flask, nitrogen was evacuated three times, and 60 ml of anhydrous dichloromethane containing 1.0 g (3.6 mmol) of pentamethylcyclopentadienyltrimethoxytitanium was added. Then, a 60 ml anhydrous dichloromethane solution containing 1.70 g (11.5 mmol) of 2,4,6-trifluorophenol was added dropwise over the solution. The mixture was allowed to drip over the solution over 40 minutes. After reacting at 0°C for 12 hours, the temperature was slowly raised to room temperature. The solvent was removed by distillation under reduced pressure, and the mixture was washed three times with anhydrous n-hexane and dried. The mixture was recrystallized three times from a mixed solution of anhydrous dichloromethane and anhydrous n-hexane and dried to obtain 2.06 g of yellow crystals with a yield of 92%.

[0089] 2.06 g (3.3 mmol) of the yellow crystals were added to a dry 250 ml two-necked flask. The flask was purged with nitrogen three times, and 45 ml of anhydrous dichloromethane was added to dissolve the crystals. The flask was cooled to 0°C, and 5.1 ml (6.6 mmol) of tert-butyl lithium was added. After stirring for 12 hours, a solution of 0.80 g (7.3 mmol) of trimethylsilyl chloride dissolved in 15 ml of anhydrous dichloromethane was added. The temperature was then slowly raised to room temperature, filtered, and the solvent was removed by distillation under reduced pressure. The crystals were washed three times, recrystallized, and dried to isolate red crystals (yield 65%) for use in the present invention.

[0090] The elemental analysis of the red crystals showed that: C 22 H 19 O2F6Ti. Specifically, Calcd. For (theoretical calculated value): C 55.37%, H 4.01%; Found (measured value): C 55.44%, H 4.14%. The structural formula of the compound synthesized in this example is shown in formula (3).

[0091] Application Example 3

[0092] A method for preparing syndiotactic polystyrene comprises the following steps:

[0093] In a dry 50 ml two-necked flask, high-purity nitrogen was pumped out three times, 20 ml of refined styrene monomer was added, and after electromagnetic stirring in a 70°C oil bath for 20 minutes, 0.20 ml of a toluene solution of MAO (wherein, MAO was 0.020 mmol) and 0.3 ml of a toluene solution of the titanocene catalyst prepared in Example 3 (wherein, the titanocene catalyst was 0.00015 mmol, and the aluminum-titanium ratio of MAO to the titanocene catalyst was 130) were injected with a syringe. After reacting for 1 hour, the reaction was terminated with ethanol and dried to obtain 17.5 g of a powdered solid.

[0094] According to GB / T 9345.1-2008, the calcined product has an ash content of 59.0 ppm.

[0095] Example 4

[0096] A titanocene catalyst, the structural formula of which is shown in formula (4):

[0097]

[0098] The compound represented by formula (4) comprises the following preparation steps:

[0099] In a dry 250 ml two-necked flask, nitrogen was evacuated three times, and 60 ml of anhydrous dichloromethane containing 1.0 g (3.6 mmol) of pentamethylcyclopentadienyltrimethoxytitanium was added. Then, a 60 ml anhydrous dichloromethane solution containing 1.91 g (11.5 mmol) of 2,3,4,6-tetrafluorophenol was added dropwise from the above solution. The solution was added dropwise over 40 minutes. After reacting at -80°C for 2 hours, the temperature was slowly raised to room temperature. The solvent was removed by distillation under reduced pressure, and the solution was washed three times with anhydrous n-hexane and dried. The solution was recrystallized three times from a mixed solution of anhydrous dichloromethane and anhydrous n-hexane and dried to obtain 2.17 g of yellow crystals with a yield of 89%.

[0100] 2.17 g (3.2 mmol) of the yellow crystals were added to a dry 250 ml two-necked flask. The flask was purged with nitrogen three times, and 45 ml of anhydrous dichloromethane was added to dissolve the crystals. The flask was cooled to -30°C, and 2.5 ml (3.2 mmol) of tert-butyl lithium was added. After stirring for 2 hours, a solution of 0.41 g (3.8 mmol) of trimethylsilyl chloride dissolved in 15 ml of anhydrous dichloromethane was added. The temperature was then slowly raised to room temperature, filtered, and the solvent was removed by distillation under reduced pressure. The crystals were washed three times, recrystallized, and dried to isolate red crystals (yield 60%) for use in the present invention.

[0101] The elemental analysis of the red crystals showed that: C 22 H 17 O2F8Ti. Specifically, Calcd.For (theoretical calculated value): C 51.49%, H 3.34%; Found (measured value): C 51.42%, H 3.30%. The structural formula of the compound synthesized in this example is shown in formula (4).

[0102] Application Example 4

[0103] A method for preparing syndiotactic polystyrene comprises the following steps:

[0104] In a dry 50 ml two-necked flask, high-purity nitrogen was used for 3 times to evacuate the solution, 20 ml of refined styrene monomer was added, and after electromagnetic stirring in a 70°C oil bath for 20 minutes, 0.20 ml of a toluene solution of MAO (wherein, MAO was 0.020 mmol) and 0.40 ml of a toluene solution of the titanocene catalyst prepared in Example 4 (wherein, the titanocene catalyst was 0.0002 mmol, and the aluminum-titanium ratio of MAO to the titanocene catalyst was 100) were injected with a syringe. After reacting for 1 hour, the reaction was terminated with ethanol and dried to obtain 17.6 g of a powdered solid.

[0105] According to GB / T 9345.1-2008, the calcined product has an ash content of 58.9 ppm.

[0106] Example 5

[0107] A titanocene catalyst, the structural formula of which is shown in formula (5):

[0108]

[0109] The compound represented by formula (5) comprises the following preparation steps:

[0110] In a dry 250 ml two-necked flask, nitrogen was evacuated three times, and 60 ml of anhydrous dichloromethane containing 1.0 g (3.6 mmol) of pentamethylcyclopentadienyltrimethoxytitanium was added. Then, a 60 ml anhydrous dichloromethane solution containing 2.06 g (11.2 mmol) of pentafluorophenol was added dropwise over the mixture over 40 minutes. After reacting at -30°C for 6 hours, the temperature was slowly raised to room temperature. The solvent was removed by distillation under reduced pressure, and the mixture was washed three times with anhydrous n-hexane and dried. The mixture was recrystallized three times from a mixed solution of anhydrous dichloromethane and anhydrous n-hexane and dried to obtain 2.27 g of yellow crystals with a yield of 86%.

[0111] 2.27 g (3.1 mmol) of the yellow crystals were added to a dry 250 ml two-necked flask. The flask was purged with nitrogen three times, and 45 ml of anhydrous dichloromethane was added to dissolve the crystals. The flask was cooled to -80°C, and 4.8 ml (6.2 mmol) of tert-butyl lithium was added. After stirring for 6 hours, a solution of 0.74 g (6.8 mmol) of trimethylsilyl chloride dissolved in 15 ml of anhydrous dichloromethane was added. The temperature was then slowly raised to room temperature, filtered, and the solvent was removed by distillation under reduced pressure. The crystals were washed three times, recrystallized, and dried to isolate red crystals (yield 66%) for use in the present invention.

[0112] The elemental analysis of the red crystals showed that: C 22 H 15 O2F 10Ti. Specifically, Calcd. For (theoretical calculated value): C 48.11%, H 2.75%; Found (measured value): C 48.20%, H 2.76%. The structural formula of the compound synthesized in this example is shown in formula (5).

[0113] Application Example 5

[0114] A method for preparing syndiotactic polystyrene comprises the following steps:

[0115] In a dry 50 ml two-necked flask, high-purity nitrogen was used for 3 pumping, and 20 ml of refined styrene monomer was added. After electromagnetic stirring in a 70°C oil bath for 20 minutes, 0.15 ml of a toluene solution of MAO (wherein, MAO was 0.015 mmol) and 0.60 ml of a toluene solution of the titanocene catalyst prepared in Example 5 (wherein, the titanocene catalyst was 0.0003 mmol, and the aluminum-titanium ratio of MAO to the titanocene catalyst was 50) were injected with a syringe. After reacting for 1 hour, the reaction was terminated with ethanol and dried to obtain 17.0 g of a powdered solid.

[0116] According to GB / T 9345.1-2008, the calcined product has an ash content of 46.4 ppm. The powder is white after drying, and its crystallinity is 45% as determined by wide-angle X-ray diffraction. The dielectric constant of the pressed powder is 1.81, and the dielectric loss is 0.00029.

[0117] Application Examples 1 to 5 respectively use the titanocene catalyst synthesized in Examples 1 to 5 as the main catalyst and MAO as the main catalyst, and the catalyst composition formed is used to catalyze the polymerization of styrene monomer to form syndiotactic polystyrene. In Application Examples 1 to 5, the concentration of the titanocene catalyst is gradually increased, and the aluminum-titanium ratio of MAO and the titanocene catalyst is reduced, that is, the relative addition amount of MAO is reduced, and high activity can still be maintained to prepare syndiotactic polystyrene with a low ash content. The ash content of the product is low, and the product remains white after high-temperature drying. The tested dielectric constant is less than 2, and the dielectric loss is low, indicating that the syndiotactic polystyrene obtained in Application Examples 1 to 5 is an ideal material for high-end application markets, such as battery separators, capacitor films, baby products, household appliances, and other manufacturing fields.

[0118] Comparative Application Example 1

[0119] A method for preparing syndiotactic polystyrene is different from that of Application Example 5 in that the titanocene catalyst used in this example is a compound represented by formula (6):

[0120]

[0121] The dried powder yielded 4.8 g of solid powder. The calcined product had an ash content of 164.3 ppm, as determined by GB / T 9345.1-2008. The dried powder was yellowish in color, and wide-angle X-ray diffraction analysis revealed a crystallinity of 48%. After tableting, the powder exhibited a dielectric constant of 2.53 and a dielectric loss of 0.00185.

[0122] The structural difference between the compound represented by formula (5) in Application Example 5 and the compound represented by formula (6) in this example is that the titanium in the compound represented by formula (5) is trivalent titanium, while the titanium in the compound represented by formula (6) is tetravalent titanium. Trivalent titanium still has high catalytic activity in the case of low MAO addition, because trivalent titanium does not need TIBA for reduction, while tetravalent titanium has a significantly decreased catalytic activity relative to trivalent titanium in the absence of TIBA and with low MAO addition, the product decreases, the relative content of the catalyst component remaining in the system increases, and the ash content increases. The ash content is high, and the product turns yellow after high-temperature drying. This is because the presence of high ash content at high temperature promotes thermal oxidation degradation reaction. The presence of high ash content can promote heterogeneous nucleation and improve product crystallinity, but at the same time it will greatly increase the dielectric constant and dielectric loss of the product, making it unsuitable for application in high-end application markets. Because the presence of ash will cause electron density interference between the polymer main chain and the charge carriers, the conductivity will increase significantly, generating a large amount of heat to heat up the electrical appliance, aggravating the breakdown of the polymer film, resulting in a decrease in electrical capacity and life, and even causing safety accidents.

[0123] Application Comparative Example 2

[0124] A method for preparing syndiotactic polystyrene, which differs from Application Example 5 in that: first, the titanocene catalyst used in this example is the compound represented by formula (6); second, alkyl aluminum TIBA is additionally added as a co-catalyst to improve the polymerization activity. Specifically, 1.50 ml (0.150 mmol) of a toluene solution of TIBA is added, and the aluminum-titanium ratio of TIBA to the main catalyst is 500. Drying yields 15.1 g of a powder solid.

[0125]

[0126] According to GB / T 9345.1-2008, the calcined product has an ash content of 558.9 ppm.

[0127] In this example, the titanium in the compound represented by formula (6) is tetravalent titanium. Compared with Application Example 5, TIBA is additionally added as a co-catalyst in this example, which improves the catalytic activity. However, due to the introduction of a large amount of TIBA, the relative content of the catalyst components remaining in the system increases, and the ash content increases.

[0128] Application Comparative Example 3

[0129] A method for preparing syndiotactic polystyrene is different from that of Application Example 5 in that the titanocene catalyst used in this example is a compound represented by formula (7):

[0130]

[0131] The dried solid powder yielded 2.3 g. The calcined product had an ash content of 342.9 ppm according to GB / T 9345.1-2008.

[0132] The structural difference between the compound represented by formula (5) in Application Example 5 and the compound represented by formula (7) in this example is that the benzene ring in the compound represented by formula (5) is polysubstituted with F, while the benzene ring in the compound represented by formula (7) is polysubstituted with Cl. Both are trivalent titanium mono-titanocenes. F substitution still has high catalytic activity when the MAO addition amount is low, because F has a greater electronegativity than Cl, and F has a strong polarization effect, which is conducive to F substitution by MAO, thereby generating more active species and high catalytic activity. However, Cl substitution significantly reduces the catalytic activity compared to F substitution when the MAO addition amount is low, the product decreases, the relative content of the catalyst components remaining in the system increases, and the ash content increases.

[0133] Comparative Application Example 4

[0134] A method for preparing syndiotactic polystyrene is disclosed, which differs from Application Example 5 in that: first, the titanocene catalyst used in this example is the compound represented by formula (7); second, the amount of MAO added in this example is increased, specifically, 0.50 ml of a toluene solution of MAO (wherein the amount of MAO is 0.050 mmol, and the aluminum-titanium ratio of MAO to the monotantalum compound is 500) is injected with a syringe, and 8.9 g of a powder solid is obtained by drying.

[0135]

[0136] According to GB / T 9345.1-2008, the calcined product has an ash content of 862.2 ppm.

[0137] The titanium in the compound represented by formula (7) in this example is trivalent titanium, but the benzene ring is polysubstituted with Cl. Compared with Application Example 5, the amount of MAO added in this example is increased, and the catalytic activity is improved. However, due to the introduction of a large amount of MAO, the relative content of the catalyst components remaining in the system increases, and the ash content increases.

[0138] Application Comparative Example 5

[0139] A method for preparing syndiotactic polystyrene is different from that of Application Example 1 in that the titanocene catalyst used in this example is a compound represented by formula (8):

[0140]

[0141] The dried solid powder yielded 2.3 g. The calcined product had an ash content of 446.8 ppm according to GB / T 9345.1-2008.

[0142] The structural difference between the compound represented by formula (1) in Application Example 1 and the compound represented by formula (8) in this example is that the titanium in the compound represented by formula (1) is trivalent titanium and the auxiliary ligand is OC6H4F, while the titanium in the compound represented by formula (8) is tetravalent titanium and the auxiliary ligand is OCH3. The catalytic activity of the trivalent titanium and F-substituted titanocene catalyst in Application Example 1 is much higher than the tetravalent titanium and methoxy-substituted titanocene catalyst in this example. The titanocene catalyst in this example has low catalytic activity, produces little product, has a high relative content of catalyst components remaining in the system, and has a large ash content.

[0143] Application Comparative Example 6

[0144] A method for preparing syndiotactic polystyrene, which differs from Application Example 1 in that: first, the titanocene catalyst used in this example is the compound represented by formula (8); second, alkyl aluminum TIBA is additionally added as a co-catalyst to improve polymerization activity. Specifically, 0.10 ml (0.100 mmol) of a toluene solution of TIBA is added, and the aluminum-to-titanium ratio of TIBA to the titanocene catalyst is 1000. 8.7 g of a powder solid is obtained by drying.

[0145]

[0146] According to GB / T 9345.1-2008, the calcined product has an ash content of 704.4 ppm.

[0147] In this example, TIBA was additionally added as a co-catalyst, which improved the catalytic activity. However, compared with Application Example 1, a large amount of TIBA was introduced, and the relative content of the catalyst components remaining in the system increased, and the ash content increased.

[0148] Application Comparative Example 7

[0149] A method for preparing syndiotactic polystyrene is different from that of Application Example 1 in that the titanocene catalyst used in this example is a compound represented by formula (9):

[0150]

[0151] The dried solid powder had an ash content of 642.4 ppm according to GB / T 9345.1-2008.

[0152] The structural difference between the compound represented by formula (1) in Application Example 1 and the compound represented by formula (9) in this example is that the titanium in the compound represented by formula (1) is trivalent titanium and the auxiliary ligand is OC6H4F, while the titanium in the compound represented by formula (9) is tetravalent titanium and the auxiliary ligand is Cl. The catalytic activity of the trivalent titanium and F-substituted titanocene catalyst of Application Example 1 is much higher than that of the tetravalent titanium and Cl-substituted titanocene catalyst of this example. The titanocene catalyst of this example has low catalytic activity, produces little product, has a high relative content of catalyst components remaining in the system, and has a large ash content.

[0153] Comparative Application Example 8

[0154] A method for preparing syndiotactic polystyrene, which differs from Application Example 1 in that: first, the titanocene catalyst used in this example is the compound represented by formula (9); second, alkyl aluminum TIBA is additionally added as a co-catalyst to improve polymerization activity. Specifically, 1.00 ml (0.100 mmol) of a toluene solution of TIBA is added, and the aluminum-to-titanium ratio of TIBA to the titanocene catalyst is 1000. Drying yields 5.6 g of a powdered solid.

[0155]

[0156] According to GB / T 9345.1-2008, the calcined product has an ash content of 1094.3 ppm.

[0157] In this example, TIBA was additionally added as a co-catalyst, and the catalytic activity was improved. However, compared with Application Example 1, due to the introduction of a large amount of TIBA, the relative content of the catalyst components remaining in the system increased, and the ash content increased.

[0158] As can be seen from the above, compared with other auxiliary ligands, the titanocene catalyst in the embodiment of the present invention is a trivalent titanium mono-titanocenes compound of F mono- or poly-substituted, and the catalyst composition formed by its combination with alkylaluminoxane has extremely high catalytic activity, and the syndiotactic polystyrene yield obtained is high. The titanocene catalyst of the embodiment of the present invention can effectively reduce the alkylaluminoxane (such as MAO) consumption in the syndiotactic polystyrene polymerization system, and does not need to additionally add alkylaluminum (such as TIBA) as a reducing agent, greatly reducing the catalyst component residue in the product, reducing ash content, and the synthesized syndiotactic polystyrene has a low ash content. And, in the catalyst composition of the embodiment of the present invention, the consumption of expensive alkylaluminoxane is greatly reduced, effectively reducing the production cost of syndiotactic polystyrene, and the syndiotactic polystyrene obtained has the comprehensive properties such as good color, crystallinity, electrical properties and service life, and is widely used in battery separators, capacitor films, baby products or household appliances.

[0159] In summary, the titanocene catalyst of the present invention adopts a trivalent titanium structure with F being monosubstituted or polysubstituted. F has a strong polarizing effect, which gives the catalyst high polymerization activity. Moreover, the titanium in the catalyst is trivalent titanium, so there is no need to introduce a reducing co-catalyst, which is beneficial to reducing the co-catalyst content in the polymerization system, thereby effectively reducing the ash content in the product, and obtaining a syndiotactic polystyrene product with comprehensive properties such as good color, crystallinity, electrical properties and service life.

Claims

1. A titanocene catalyst, characterized in that The structural formula is shown in the following formula (I): （I）； In formula (I), R1 is a cyclopentadienyl group or a cyclopentadienyl group substituted with 1 to 5 C1 to C4 alkyl groups; R2 is a C6 to C10 aryl group; n1 is 1 to 5, and n2 is 0 to 4.

2. The titanocene catalyst according to claim 1, characterized in that The structural formula of the compound represented by formula (I) is shown in formulas (1) to (5): （1）； （2）； （3）； （4）； （5）。 3. A method for preparing the titanocene catalyst according to claim 1 or 2, characterized in that: The following steps are involved: subjecting the compound represented by formula (II) to an oxidation-reduction reaction under the action of an organic lithium compound and an organic silicon compound to obtain the titanocene catalyst; (II)。 4. The preparation method according to claim 3, characterized in that The organic lithium compound includes at least one of tert-butyl lithium, n-butyl lithium, isobutyl lithium, benzyl lithium or lithium diisopropylamide; and / or, the organosilicon compound comprises at least one of trimethylchlorosilane, trimethylsilanol, trimethylsilyl ether, trimethylsilyl ester or trimethylsilylamine; and / or, the molar ratio of the compound represented by formula (II) to the organic lithium compound is 1:(0.5-2.5); and / or, the molar ratio of the compound represented by formula (II) to the organosilicon compound is 1:(0.8-3); And / or, the temperature of the redox reaction is -100~10°C; And / or, the redox reaction time is 1 to 20 hours.

5. A catalyst composition, characterized in that The method comprises an alkylaluminoxane and the titanocene catalyst according to claim 1 or 2, wherein the structural formula of the alkylaluminoxane is shown in the following formula (III): (III); In formula (III), R3 is a C1-C4 alkyl group; n3 is 6-40.

6. The catalyst composition according to claim 5, characterized in that The molar ratio of Al in the alkylaluminoxane to Ti in the titanocene catalyst is (10-2000):

1.

7. A method for preparing syndiotactic polystyrene, characterized in that: The following steps are involved: A polymerization system containing styrene monomer and the catalyst composition according to claim 5 or 6 is subjected to a polymerization reaction to obtain the syndiotactic polystyrene.

8. The preparation method according to claim 7, characterized in that The polymerization reaction temperature is 0-100°C; And / or, the polymerization reaction time is 0.01 to 10 hours; And / or, in the polymerization system, the concentration of the titanocene catalyst is 10 -9 ~10 -3 mol / L.

9. The preparation method according to claim 7, characterized in that The ash content of the syndiotactic polystyrene is 30-150 ppm.

10. The preparation method according to claim 7, characterized in that The syndiotactic polystyrene is used in the fields of battery separators, capacitor films, baby products or household appliances.

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