Low cis-polybutadiene rubber and preparation method thereof, and HIPS (high impact polystyrene) resin and preparation method thereof

Abstract

The invention relates to the field of synthetic rubber and modified resin, and discloses low cis-polybutadiene rubber and a preparation method thereof, and HIPS (High Impact Polystyrene) resin and a preparation method thereof. The number-average molecular weight of the low cis-polybutadiene rubber is in three-peak distribution, the first peak number-average molecular weight is 310,000 to 360,000 g / mol, the second peak number-average molecular weight is 120,000 to 150,000 g / mol, and the third peak number-average molecular weight is 36,000 to 48,000 g / mol; wherein the peak area of the first peak is 21%-44%, the peak area of the second peak is 51%-79%, and the peak area of the third peak is 0.4%-8%; the low cis-polybutadiene rubber is coupled low cis-polybutadiene rubber. The low cis-polybutadiene rubber provided by the invention is used as a flexibilizer for preparing HIPS (High Impact Polystyrene) resin, and rubber with different particle sizes can generate a synergistic effect, so that the HIPS resin has the characteristics of high surface glossiness and high impact strength.

Description

Technical Field

[0001] The invention relates to the field of synthetic rubber and modified resin, and in particular to a low-cis polybutadiene rubber and a preparation method thereof, and a HIPS resin and a preparation method thereof. Background Art

[0002] In the preparation of HIPS resin (i.e. high impact polystyrene), the rubber conventionally selected as a toughening agent may be low cis polybutadiene rubber, high cis polybutadiene rubber, butadiene-isoprene copolymer, solution polybutadiene styrene rubber, styrene-butadiene-styrene copolymer, especially low cis polybutadiene rubber and high cis polybutadiene rubber are the best. For low temperature toughness resin, low cis polybutadiene rubber and its derivative block butadiene styrene rubber are generally used for toughening. However, the molecular weight and distribution of the toughening rubber have a significant effect on the impact resistance of the continuous bulk HIPS resin. Usually, if the rubber molecular weight is too small, the toughening effect is poor; if the rubber molecular weight is too large, the gloss of the HIPS resin is poor. In the selection of toughening agents, it is necessary to match rubbers of different particle sizes so that rubbers of different particle sizes can work synergistically to achieve a balance between gloss and impact resistance, but this makes the polymerization process more complicated.

[0003] Functional groups with different particle sizes can be obtained by compounding coupling agents with different functional groups. However, the reaction activities of the compounded coupling agents are inconsistent, resulting in poor stability of the toughening agent. Summary of the invention

[0004] The purpose of the present invention is to overcome the problem that the existing aromatic vinyl resin toughening agent is difficult to achieve multi-level particle size matching, and to provide a low cis polybutadiene rubber and a preparation method thereof and a HIPS resin and a preparation method thereof. The low cis polybutadiene rubber has a trimodal molecular weight distribution, so that the rubber has a multi-level particle size distribution. When the low cis polybutadiene rubber is used as a toughening agent for the HIPS resin, the obtained HIPS resin has the characteristics of high gloss and high impact resistance.

[0005] In order to achieve the above-mentioned object, the first aspect of the present invention provides a low-cis polybutadiene rubber, wherein the number average molecular weight of the low-cis polybutadiene rubber is trimodal distribution, the first peak number average molecular weight is 310,000-360,000 g / mol, the second peak number average molecular weight is 120,000-150,000 g / mol, and the third peak number average molecular weight is 36,000-48,000 g / mol; wherein the peak area of ​​the first peak is 21%-44%, the peak area of ​​the second peak is 51%-79%, and the peak area of ​​the third peak is 0.4%-8%;

[0006] The low-cis polybutadiene rubber is coupled low-cis polybutadiene rubber.

[0007] A second aspect of the present invention provides a method for preparing low-cis polybutadiene rubber, wherein the method comprises the following steps:

[0008] Mixing a low-cis polybutadiene rubber solution BR1 and a low-cis polybutadiene rubber solution BR2, and removing the solvent to obtain the low-cis polybutadiene rubber;

[0009] The dosage of the low cis polybutadiene rubber solution BR1 and the low cis polybutadiene rubber solution BR2 is such that the number average molecular weight of the prepared low cis polybutadiene rubber presents a trimodal distribution, wherein the first peak number average molecular weight is 310,000-360,000 g / mol, the second peak number average molecular weight is 120,000-150,000 g / mol, and the third peak number average molecular weight is 36,000-48,000 g / mol; wherein the peak area of ​​the first peak is 21%-44%, the peak area of ​​the second peak is 51%-79%, and the peak area of ​​the third peak is 0.4%-8%;

[0010] The low-cis polybutadiene rubber is coupled low-cis polybutadiene rubber.

[0011] The third aspect of the present invention provides a method for preparing a HIPS resin, which comprises: in a benzene solvent, in the presence of a free radical initiator, polymerizing styrene and a toughening agent; wherein the toughening agent contains the above-mentioned low-cis polybutadiene rubber; wherein the benzene solvent is selected from at least one of unsubstituted or C1-C4 alkyl-substituted benzene.

[0012] A fourth aspect of the present invention provides a HIPS resin prepared by the above method.

[0013] Through the above technical scheme, the low-cis polybutadiene rubber and its preparation method and the HIPS resin and its preparation method provided by the present invention achieve the following beneficial effects.

[0014] The low cis polybutadiene rubber provided by the present invention has a trimodal number average molecular weight, and each peak has a specific peak area, so that the particle size of the low cis polybutadiene rubber of the present invention can be distributed in multiple levels, and a rubber with a suitable solution viscosity can be obtained, which is beneficial to the improvement of the glossiness and impact strength of the resin. The low cis polybutadiene rubber is used as a toughening agent to prepare the HIPS resin, and since rubbers of different particle sizes can produce a synergistic effect, the HIPS resin has the characteristics of high surface glossiness and high impact strength.

[0015] The invention mixes two low-cis polybutadiene rubber solutions so that the number average molecular weight of the low-cis polybutadiene rubber presents a trimodal distribution, and the number average molecular weight and peak area of ​​each peak meet the requirements of the low-cis polybutadiene rubber of the invention. DETAILED DESCRIPTION

[0016] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0017] The first aspect of the present invention provides a low-cis polybutadiene rubber, wherein the number average molecular weight of the low-cis polybutadiene rubber is trimodal, the first peak number average molecular weight is 310,000-360,000 g / mol, the second peak number average molecular weight is 120,000-150,000 g / mol, and the third peak number average molecular weight is 36,000-48,000 g / mol; wherein the peak area of ​​the first peak is 21%-44%, the peak area of ​​the second peak is 51%-79%, and the peak area of ​​the third peak is 0.4%-8%;

[0018] The low-cis polybutadiene rubber is coupled low-cis polybutadiene rubber.

[0019] In the present invention, the low cis polybutadiene rubber has a trimodal distribution of number average molecular weight, and each peak has a specific peak area. Such trimodal distribution of number average molecular weight and peak area can make the particle size of the low cis polybutadiene rubber of the present invention present a multi-level distribution, and can obtain a rubber with a suitable solution viscosity, which is beneficial to the improvement of the resin gloss. The low cis polybutadiene rubber is used as a toughening agent to prepare HIPS resin. Since rubbers of different particle sizes can produce a synergistic effect, the HIPS resin has the characteristics of high surface gloss and high impact strength.

[0020] In the present invention, the low cis polybutadiene rubber refers to a polybutadiene rubber having a cis 1,4 structure content of 30 wt% to 40 wt%.

[0021] In the present invention, the low-cis polybutadiene rubber can be a single type of low-cis polybutadiene rubber or a mixture of multiple low-cis polybutadiene rubbers, as long as the number average molecular weight of the single type of low-cis polybutadiene rubber or the mixture of multiple low-cis polybutadiene rubbers presents a trimodal distribution, and the number average molecular weight and peak area of ​​each peak meet the requirements of the present invention.

[0022] According to the present invention, preferably, in the low-cis polybutadiene rubber, the first peak number average molecular weight is 320,000-355,000 g / mol, preferably 330,000-350,000 g / mol; the peak area of ​​the first peak is 25%-40%, preferably 27%-36%.

[0023] According to the present invention, preferably, in the low-cis polybutadiene rubber, the second peak number average molecular weight is 125,000-145,000 g / mol, preferably 130,000-140,000 g / mol; the peak area of ​​the second peak is 57%-75%, preferably 62%-72%.

[0024] According to the present invention, preferably, in the low-cis polybutadiene rubber, the third peak number average molecular weight is 37,000-46,000 g / mol, preferably 38,000-45,000 g / mol; the peak area of ​​the third peak is 0.6%-5%, preferably 0.8%-3%.

[0025] According to the present invention, preferably, the viscosity of the 5wt% styrene solution of the low cis polybutadiene rubber at 25° C. is 80-130cp. When the solution viscosity is controlled within the above range, it is beneficial to obtain a HIPS resin with higher gloss and stronger impact resistance.

[0026] Furthermore, the viscosity of a 5 wt % styrene solution of the low cis polybutadiene rubber at 25° C. is 90-110 cp.

[0027] According to the present invention, the Mooney viscosity ML (1+4min, 100°C) of the low cis polybutadiene rubber is 40-55. When the Mooney viscosity of the rubber meets the above range, the low cis polybutadiene rubber has better processing performance and is easier to process and shape.

[0028] According to the present invention, the gel content of the low-cis polybutadiene rubber is not higher than 150 ppm. The lower the gel content, the more favorable it is to obtain HIPS resin with excellent performance.

[0029] Furthermore, the gel content of the low-cis polybutadiene rubber is not higher than 100 ppm.

[0030] Furthermore, the gel content of the low-cis polybutadiene rubber is not higher than 80 ppm.

[0031] According to the present invention, the vinyl content of the low-cis polybutadiene rubber is 8wt%-20wt%.

[0032] In the present invention, the vinyl content can also be referred to as the content of 1,2-structural units, which refers to the content of structural units formed by 1,2-polymerization of butadiene. When the vinyl content meets the range of the present invention, the grafting reaction of the continuous bulk HIPS resin and the subsequent moderate crosslinking can be guaranteed.

[0033] Furthermore, the vinyl content of the low-cis polybutadiene rubber is 10wt%-16wt%.

[0034] According to the present invention, low cis polybutadiene rubber can obtain lower chroma. Preferably, the chroma of 5 wt% styrene solution of the low cis polybutadiene rubber is less than or equal to 15 APHA, preferably less than or equal to 8 APHA, more preferably less than or equal to 5 APHA.

[0035] A second aspect of the present invention provides a method for preparing low-cis polybutadiene rubber, wherein the method comprises the following steps:

[0036] Mixing a low-cis polybutadiene rubber solution BR1 and a low-cis polybutadiene rubber solution BR2, and removing the solvent to obtain the low-cis polybutadiene rubber;

[0037] The dosage of the low cis polybutadiene rubber solution BR1 and the low cis polybutadiene rubber solution BR2 is such that the number average molecular weight of the prepared low cis polybutadiene rubber presents a trimodal distribution, wherein the first peak number average molecular weight is 310,000-360,000 g / mol, the second peak number average molecular weight is 120,000-150,000 g / mol, and the third peak number average molecular weight is 36,000-48,000 g / mol; wherein the peak area of ​​the first peak is 21%-44%, the peak area of ​​the second peak is 51%-79%, and the peak area of ​​the third peak is 0.4%-8%;

[0038] The low-cis polybutadiene rubber is coupled low-cis polybutadiene rubber.

[0039] In the present invention, two low-cis polybutadiene rubber solutions are mixed so that the number average molecular weight of the low-cis polybutadiene rubber presents a trimodal distribution, and the number average molecular weight and peak area of ​​each peak meet the requirements of the low-cis polybutadiene rubber of the present invention.

[0040] According to the present invention, the method for preparing the low-cis polybutadiene rubber solution BR1 comprises the following steps:

[0041] Under anionic polymerization conditions, butadiene 1 is first polymerized in an organic solvent in the presence of a first organic lithium initiator and a first structure regulator to obtain a polymerization solution 1; the polymerization solution 1 is contacted with a first coupling agent to perform a first coupling reaction, and then a first terminator is added to obtain a low-cis polybutadiene rubber solution BR1.

[0042] According to the present invention, the method for preparing the low-cis polybutadiene rubber solution BR2 comprises the following steps:

[0043] Under anionic polymerization conditions, butadiene 2 is subjected to a second polymerization in an organic solvent in the presence of a second organic lithium initiator and a second structure regulator to obtain a polymerization solution 2; the polymerization solution 2 is contacted with a second coupling agent to perform a second coupling reaction, and then a second terminator is added to obtain a low-cis polybutadiene rubber solution BR2.

[0044] According to the present invention, in the preparation process of the low-cis polybutadiene rubber solution BR1 of the present invention, the content of butadiene 1 is 10wt%-20wt%, preferably 10wt%-16wt%, based on the total weight of the organic solvent and butadiene 1. In the preparation process of the low-cis polybutadiene rubber solution BR2 of the present invention, the content of butadiene 2 is 10wt%-20wt%, preferably 10wt%-16wt%, based on the total weight of the organic solvent and butadiene 2. In the present invention, the content of butadiene 1 and the content of butadiene 2 may be the same or different.

[0045] In the present invention, in the process of preparing BR1 and BR2, the organic solvents used may be the same or different. The organic solvents may be various organic solvents conventionally used in the art. Preferably, the organic solvents are each independently one or more of an alkane solvent and a cycloalkane solvent. Among them, the alkane solvent is preferably one or more of a C4-C8 alkane solvent, more preferably one or more of n-pentane, n-hexane, n-heptane and isooctane. Among them, the cycloalkane solvent is preferably one or more of a C4-C8 cycloalkane solvent, more preferably one or more of cyclopentane, cyclohexane and cycloheptane.

[0046] In a preferred embodiment of the present invention, the organic solvents are each independently selected from a combination of cyclohexane and hexane in a weight ratio of 1:0.1-0.5.

[0047] According to the present invention, there is no particular limitation on the first organic lithium initiator and the second organic lithium initiator, and they may be the same or different. Various organic lithium initiators conventionally used in the preparation of polybutadiene rubber in the art may be used. Preferably, the organic lithium initiator is a compound shown in Formula I,

[0048] R 1Li Formula I

[0049] Among them, R 1 Selected from C1-C 10 More preferably, the organic lithium initiator is one or more of n-butyl lithium, sec-butyl lithium, isobutyl lithium and tert-butyl lithium, more preferably n-butyl lithium and / or sec-butyl lithium, and further preferably n-butyl lithium. The organic lithium initiator is added to the polymerization system in the form of a solution, and the solvent of the organic lithium initiator can be, for example, one or more of hexane, cyclohexane, heptane, etc., and the concentration is preferably 0.1-1 mol / L.

[0050] The amount of the first organic lithium initiator and the second organic lithium initiator of the present invention can be reasonably selected according to the amount of monomers and the molecular weight of the low cis polybutadiene rubber to be obtained, and the amount can vary within a wide range. Preferably, the molar ratio of the butadiene 1 to the first organic lithium initiator is 650-900:1, preferably 680-850:1, more preferably 700-830:1; the molar ratio of the butadiene 2 to the second organic lithium initiator is 2200-2800:1, preferably 2300-2700:1, more preferably 2400-2600:1.

[0051] In the present invention, the actual amount of the first organic lithium initiator and the second organic lithium initiator is the amount of the effective organic lithium initiator, which can be understood as the actual amount does not include the amount of the organic lithium initiator used to kill impurities.

[0052] In the present invention, the anionic solution polymerization reaction is carried out in the presence of a structure regulator, and the types of the first structure regulator and the second structure regulator can be conventionally selected in the art, and the first structure regulator and the second structure regulator can be the same or different. Preferably, the structure regulator is one or more of an ether compound structure regulator and an amine compound structure regulator.

[0053] Preferably, the ether compound structure regulator is one or more of aliphatic monoether, aliphatic polyether, aromatic ether and cyclic ether.

[0054] More preferably, the aliphatic monoether is one or more of aliphatic symmetric monoether and aliphatic asymmetric monoether, the aliphatic symmetric monoether is one or more of methyl ether, ethyl ether, propyl ether and butyl ether, and the aliphatic asymmetric monoether is methyl ethyl ether.

[0055] More preferably, the aliphatic polyether is one or more of an aliphatic symmetrical polyether and an aliphatic asymmetrical polyether, the aliphatic symmetrical polyether is one or more of ethylene glycol di-C1-C4 alkyl ether, diethylene glycol di-C1-C4 alkyl ether and diethylene glycol di-C1-C4 alkyl ether, preferably one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether and diethylene glycol diethyl ether, and the aliphatic asymmetric polyether is ethylene glycol methyl ethyl ether and / or diethylene glycol methyl ethyl ether.

[0056] Preferably, the aromatic ether is anisole and / or diphenyl ether.

[0057] Preferably, the cyclic ether is one or more of tetrahydrofuran, tetrahydrofurfuryl alcohol C1-C4 alkyl ether and 1,4-dioxetane, preferably one or more of tetrahydrofuran, tetrahydrofurfuryl methyl ether, tetrahydrofurfuryl ethyl ether, tetrahydrofurfuryl propyl ether, tetrahydrofurfuryl isopropyl ether, tetrahydrofurfuryl butyl ether and 1,4-dioxetane.

[0058] Preferably, the amine compound structure regulator is one or more of N,N,N',N'-tetramethylethylenediamine, N,N-dimethyltetrahydrofurfurylamine, triethylamine and tripropylamine.

[0059] In a preferred embodiment of the present invention, the structure regulator is one or more of tetrahydrofuran, tetrahydrofurfuryl methyl ether, tetrahydrofurfuryl ethyl ether, tetrahydrofurfuryl propyl ether, tetrahydrofurfuryl isopropyl ether, tetrahydrofurfuryl butyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether and diethylene glycol diethyl ether, more preferably one or more of tetrahydrofurfuryl methyl ether, tetrahydrofurfuryl ethyl ether and tetrahydrofurfuryl propyl ether, particularly preferably tetrahydrofurfuryl ethyl ether.

[0060] In the present invention, the molar ratio of the first structure regulator to the first organic lithium initiator is 0.02-2:1; the molar ratio of the second structure regulator to the second organic lithium initiator is 0.02-2:1. When the amount of the structure regulator is within the range specified in the present invention, the vinyl content of the prepared low cis-polybutadiene rubber can be within the range specified in the present invention, and the reaction rate can be increased.

[0061] According to the present invention, in the process of preparing BR1 and BR2, the anionic solution polymerization reaction will make the conversion rate of butadiene more than 98%; preferably, the conditions of the first polymerization include: temperature of 0-100°C, preferably 40-100°C, more preferably 50-100°C; time of 20-100min, preferably 30-60min. Preferably, the second polymerization conditions include: temperature of 0-100°C, preferably 40-100°C, more preferably 50-100°C; time of 20-100min, preferably 30-60min. Preferably, the second polymerization conditions include: temperature of 0-100°C, preferably 40-100°C, more preferably 50-100°C; time of 20-100min, preferably 30-60min.

[0062] In the present invention, the temperature of the first polymerization includes the initiation temperature of the first polymerization and the maximum temperature of the first polymerization; preferably, the difference between the maximum temperature of the first polymerization and the initiation temperature of the first polymerization is 35-50° C. The temperature of the second polymerization includes the initiation temperature of the second polymerization and the maximum temperature of the second polymerization; preferably, the difference between the maximum temperature of the second polymerization and the initiation temperature of the second polymerization is 35-50° C.

[0063] According to the present invention, the first coupling agent and the second coupling agent are each independently a silane coupling agent, preferably one or more of silicon tetrachloride, silicon tetrabromide and tin tetrachloride, more preferably silicon tetrachloride. Among them, silicon tetrachloride can control the coupling reaction more accurately, making the coupling reaction more stable and repeatable.

[0064] According to the present invention, in the process of preparing BR1 and BR2, the amount of the first coupling agent and the amount of the second coupling agent can vary within a certain range, and the molar ratio of the first coupling agent to the first organic lithium initiator is 0.2-0.3:1, preferably 0.21-0.26:1; the molar ratio of the second coupling agent to the second organic lithium initiator is 0.1-0.17:1; preferably 0.1-0.15:1.

[0065] Preferably, the conditions of the first coupling reaction include: temperature of 60-90°C, time of 20-40 min. The conditions of the second coupling reaction include: temperature of 60-90°C, time of 20-40 min.

[0066] According to the present invention, the coupling reaction can be terminated by adding a terminator to obtain a polymerization solution of low-cis polybutadiene rubber. In order to extract the low-cis polybutadiene rubber, the solvent can be removed after termination (for example, by steam condensation desolventization treatment) and dried to extract the low-cis polybutadiene rubber.

[0067] Preferably, the terminator is one or more of an alcohol, an organic acid and carbon dioxide of C1-C4, preferably one or more of isopropanol, stearic acid, citric acid and carbon dioxide, more preferably carbon dioxide. When carbon dioxide is used to terminate the reaction, carbon dioxide can form carbonate with the metal ions (Li, Mg, Al, Fe, Zn) in the polymerization system and separate from the polymer, thereby avoiding the color development reaction of the metal ions, making low cis-polybutadiene rubber have lower chroma. The carbon dioxide here can be passed into the reaction system in the form of gas (for example, passing into a carbon dioxide gas having a gauge pressure of 0.2-1MPa (for example, it can be 0.3-0.6MPa)), or can be introduced into the reaction system in the form of dry ice aqueous solution (for example, concentration is 0.1-5wt%).

[0068] In the present invention, there is no particular limitation on the amount of the terminator. Preferably, the amount of the first terminator is 0.05-0.2 parts by weight relative to 100 parts by weight of butadiene 1; and the amount of the second terminator is 0.05-0.2 parts by weight relative to 100 parts by weight of butadiene 2.

[0069] In order to improve the antioxidant property of the obtained low-cis polybutadiene rubber, an antioxidant may be introduced into the low-cis polybutadiene rubber. Preferably, after termination, an antioxidant is introduced into the reaction system obtained by termination, so that the obtained polymerization solution of the low-cis polybutadiene rubber may contain an antioxidant. If it is necessary to remove the low-cis polybutadiene rubber, a desolventizing treatment may be performed after the introduction of the antioxidant. The antioxidant in the present invention is not particularly limited and may be any conventional antioxidant in the art. For example, the antioxidant is one or more of 4,6-bis(octylthiomethyl)-o-cresol (trade name: antioxidant 1520), β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (trade name: antioxidant 1076), N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (trade name: antioxidant 4020), N-isopropylphenyl-N'-phenyl-p-phenylenediamine (trade name: antioxidant 4010NA) and N-phenyl-2-naphthylamine (trade name: antioxidant D), preferably a combination of antioxidant 1520 and antioxidant 1076, more preferably a combination of antioxidant 1520 and antioxidant 1076 in a weight ratio of 1:1-3.

[0070] Preferably, the weight ratio of the antioxidant to butadiene is 0.1-0.6:100.

[0071] According to the present invention, the dry rubber weight ratio of the low-cis polybutadiene rubber solution BR1 to the low-cis polybutadiene rubber solution BR2 is 1:2.5-4, preferably 1:2.8-3.5.

[0072] According to the present invention, a low-cis polybutadiene rubber solution BR1 and a low-cis polybutadiene rubber solution BR2 are mixed, and the solvent is removed to obtain the low-cis polybutadiene rubber; wherein the method for removing the solvent from the polymerization solution mixture of the low-cis polybutadiene rubber preferably comprises: first subjecting the mixture of BR1 and BR2 to steam condensation treatment, and then extruding dehydration and drying.

[0073] According to the present invention, the steam condensation treatment can substantially remove the organic solvent in the mixture of BR1 and BR2, and obtain colloid particles with an oil content of 1-2% by weight and a water content of 40-60% by weight. The present invention has no particular limitation on the steam condensation treatment, and the conventional steam condensation treatment method in the art can be used for the treatment.

[0074] According to the present invention, the extrusion dehydration can make the oil content of the rubber particles obtained by the steam condensation treatment reach less than 1 weight% and the water content reach 9-13 weight%, and then by drying (for example, first drying with an expansion dryer and then drying with a hot air oven) the low cis polybutadiene rubber of the present invention having a volatile matter of less than 1 weight% can be obtained.

[0075] Surprisingly, during the entire process of preparing the low-cis polybutadiene rubber by coagulation and drying, the feed is continuous and stable, without material blockage, leakage, screw slippage, puffing and ignition, discoloration of the rubber particles, and agglomeration and compaction of the rubber particles. It can be seen that the low-cis polybutadiene rubber provided by the present invention can be prepared relatively conveniently.

[0076] The third aspect of the present invention provides a method for preparing a HIPS resin, which comprises: in a benzene solvent, in the presence of a free radical initiator, polymerizing styrene and a toughening agent; wherein the toughening agent contains the above-mentioned low-cis polybutadiene rubber; wherein the benzene solvent is selected from at least one of unsubstituted or C1-C4 alkyl-substituted benzene.

[0077] In the present invention, since the number average molecular weight of the low cis polybutadiene rubber presents a trimodal distribution, the rubber particle size presents a multi-level distribution; and since the number average molecular weight and the peak area of ​​the trimodal distribution are controlled, the viscosity of the rubber solution is appropriate and the gel content is low; the low cis polybutadiene rubber is used as a toughening agent to prepare a HIPS resin, so that the HIPS resin has excellent surface gloss and impact strength.

[0078] In the present invention, the C1-C4 alkyl group is selected from at least one of methyl, ethyl, n-propyl, isopropyl and n-butyl; wherein, the C1-C4 alkyl-substituted benzene as the benzene solvent may be single-point substituted or multi-point substituted; preferably, the benzene solvent is selected from at least one of benzene, toluene, ethylbenzene and xylene.

[0079] In the present invention, the benzene solvent may be used in a conventional amount for preparing HIPS resin in the art. For example, based on the total weight of styrene, benzene solvent and toughening agent, the amount of the benzene solvent is 6 wt % to 18 wt %.

[0080] In the present invention, the toughening agent contains the low cis polybutadiene rubber obtained by the above method of the present invention to obtain a HIPS resin with high gloss and high impact resistance. In order to obtain a HIPS resin with better performance, the weight ratio of styrene to the toughening agent based on dry weight is 550-1900:100, preferably 600-1600:100, more preferably 800-1400:100, and further preferably 900-1300:100.

[0081] In the present invention, the free radical initiator can be a conventional initiator type for preparing HIPS resin in the art, for example, the free radical initiator can be one or more of thermal decomposition type initiators, preferably selected from peroxide initiators and / or azobisnitrile compound initiators, more preferably one or more of peroxy-2-ethylhexyl tert-butyl carbonate, diacyl peroxide, peroxydicarbonate, peroxycarboxylic acid ester, alkyl peroxide and azobisnitrile compounds, further preferably one or more of dibenzoyl peroxide, di-o-methylbenzoyl peroxide, tert-butyl perbenzoate, diisopropylbenzene peroxide, azobisisobutyronitrile and azobisisoheptonitrile. In the present invention, the weight ratio of the amount of styrene used to the amount of the free radical initiator used is 2500-12000:1, more preferably 3000-9500:1, more preferably 4000-9000:1, and further preferably 5000-8500:1.

[0082] In the present invention, various additives can be introduced into the polymerization reaction, so that HIPS has better comprehensive performance, that is, high surface gloss and impact resistance. Preferably, the additive is mineral oil. In the present invention, the amount of the mineral oil is 2-5 parts by weight relative to 100 parts by weight of styrene.

[0083] In the present invention, the polymerization reaction conditions include: temperature of 100-150° C. and time of 7-9 hours.

[0084] In a preferred embodiment of the present invention, the conditions of the polymerization reaction include: first reacting at 100-110°C for 1-3h, then reacting at a temperature of 115-125°C for 1-3h (e.g. 1-2h), then reacting at 130-140°C for 1-3h (e.g. 1-2h), and finally reacting at 145-155°C for 1-3h (e.g. 1-2.5h). More preferably, the conditions of the polymerization reaction include: first reacting at 105-110°C for 1.5-2.5h, then reacting at a temperature of 120-125°C for 1.5-2.5h, then reacting at 130-135°C for 1.5-2.5h, and finally reacting at 150-155°C for 1.5-2.5h. The polymerization reaction can be carried out under stirring, for example, under stirring at 100-400rpm.

[0085] A fourth aspect of the present invention provides a HIPS resin prepared by the above method.

[0086] According to the present invention, the content of the structural unit of styrene in the HIPS resin is 85wt%-95wt%, preferably 88wt%-94wt%.

[0087] In the present invention, the structural units of styrene are removed from the HIPS resin, and the remaining structural units are mainly structural units provided by butadiene. It can be understood that the remaining content is the content of butadiene structural units, that is, the content of the butadiene structural units is 5wt%-15wt%, preferably 6wt%-12wt%.

[0088] According to the present invention, the weight average molecular weight of the HIPS resin is 150,000-400,000 g / mol, preferably 200,000-300,000 g / mol.

[0089] According to the present invention, the molecular weight distribution coefficient of the HIPS resin is 2-2.9.

[0090] The HIPS resin prepared by the method of the present invention has high impact resistance and high gloss. Preferably, the Izod impact strength of the HIPS resin is 14 kJ / m 2 Above, preferably 15 kJ / m 2 More preferably 15-17 kJ / m 2 The surface gloss (60°) of the HIPS resin is above 69, preferably above 70, and more preferably above 75.

[0091] The present invention will be described in detail below through examples.

[0092] In the following examples and comparative examples, the monomer conversion rate is determined by the weight method, that is, the weight percentage of the polymer weight after solvent removal to the theoretical polymer yield.

[0093] The content of 1,2-polymerized structural units in low cis-polybutadiene rubber is to measure the vinyl content therein, which is determined by using an AVANCEDRX400MHz nuclear magnetic resonance spectrometer produced by BRUKER, wherein the frequency is 400MHz, the solvent is deuterated chloroform, and the built-in standard sample is tetramethylsilane.

[0094] The molecular weight and molecular weight distribution were determined using a HLC-8320 gel permeation chromatograph from Tosoh Corporation of Japan, where the test conditions included: the chromatographic column was TSKgel SuperMultiporeHZ-N, the standard column was TSKgelSuperMultiporeHZ, the solvent was chromatographic grade THF, the calibration standard was polystyrene, the sample mass concentration was 1 mg / mL, the injection volume was 10.00 μL, the flow rate was 0.35 mL / min, and the test temperature was 40°C.

[0095] The viscosity of a 5 wt % styrene solution of low cis polybutadiene rubber is measured at a constant temperature of 25° C. using a capillary viscometer.

[0096] The gel content of low cis-polybutadiene rubber is determined by a gravimetric method. After filtering through a 400-mesh (38 μm) sieve, the ratio of the weight of the residue to the amount of rubber is calculated.

[0097] The Mooney viscosity was measured using a GT-7080-S2 Mooney viscometer produced by Taiwan High Speed ​​Rail Corporation according to the method specified in the Chinese national standard GB / T1232.1-2016. The test conditions were: preheating time 1 min, rotation time 4 min, and test temperature 100 °C.

[0098] The APHA colorimetric test method is as follows: a low-cis polybutadiene rubber sample is prepared into a 5 wt% styrene solution and measured using a Lico620 colorimeter with a colorimetric tube having a diameter of 11 mm.

[0099] The mechanical properties of HIPS were tested using the British INSTRON 5567 universal material testing machine. Among them, the cantilever beam notched impact strength was measured according to the GB / T1843-2018 standard (kJ / m 2 ).

[0100] 60° gloss is measured according to ASTM D526 (60°).

[0101] In the following examples and comparative examples:

[0102] Antioxidant 1520 was purchased from Sinopharm Reagent Company, analytical grade;

[0103] Antioxidant 1076 was purchased from Inotech Reagent Company, analytical grade;

[0104] Tetrahydrofurfuryl ethyl ether was purchased from J&K Reagent Company, 99 wt%;

[0105] n-Butyl lithium was purchased from J&K Reagent Company and diluted to 0.4 mol / L with hexane;

[0106] Mineral oil was provided by Beijing Yanshan Petrochemical Company Chemical Plant No. 1, and its density was 0.85-0.88 g / ml.

[0107] Organic solvent A: a mixed solvent of cyclohexane and hexane in a mass ratio of 1:0.2.

[0108] Antioxidant A: a combination of antioxidant 1520 and antioxidant 1076 in a weight ratio of 1:2.

[0109] Antioxidant B: a combination of antioxidant 1520 and antioxidant 1076 in a weight ratio of 1:1.

[0110] Preparation Example 1A

[0111] Under nitrogen protection, an organic solvent, 1,3-butadiene monomer and a structure regulator are added to a reactor, and an organic lithium initiator is added after heating to the polymerization temperature, and then an anionic solution polymerization reaction is carried out at this temperature to obtain a polymerization solution 1, and the monomer conversion rate is shown in Table 1; then a first coupling agent is added to the polymerization solution 1 to carry out a coupling reaction under coupling conditions; a terminator is added to terminate the coupling reaction, and then an antioxidant is added for mixing, and finally a polymerization solution LCBR 1A of low cis polybutadiene rubber is obtained. The types and amounts of the coupling agent, terminator and antioxidant, as well as the conditions of the polymerization reaction and the coupling reaction are shown in Table 1.

[0112] Preparation Examples 2A-10A

[0113] The polymerization solutions LCBR 2A-LCBR10A of low-cis polybutadiene rubber were prepared according to the method described in Preparation Example 1A, except that the parameters shown in Table 1 were used for the reactions.

[0114] Preparation Examples 1B-10B

[0115] The polymerization solutions LCBR 1B to LCBR10B of low-cis polybutadiene rubber were prepared according to the method described in Preparation Example 1A, except that the parameters shown in Table 2 were used for the reactions.

[0116] Preparation Examples 1C-3C

[0117] The linear polymerization solutions of low cis polybutadiene rubber LCBR 1C-LCBR 3C were prepared according to the method described in Preparation Example 1A, except that the reaction was carried out using the parameters shown in Table 2. The number average molecular weights of the low cis polybutadiene linear polymers in LCBR 1C-LCBR 3C were 37,800 g / mol, 126,000 g / mol, and 336,000 g / mol, respectively.

[0118] Table 1

[0119]

[0120] Table 1

[0121]

[0122]

[0123] Note: The amounts listed in Table 1 are all based on pure compounds.

[0124] Table 2

[0125]

[0126] Table 2

[0127]

[0128]

[0129] Table 2

[0130]

[0131] Note: The amounts listed in Table 2 are all based on pure compounds.

[0132] Example 1

[0133] The low cis polybutadiene rubber LCBR1A solution and the low cis polybutadiene rubber LCBR1B were mixed at a dry rubber weight ratio of LCBR 1A to LCBR 1B of 1:3, and the organic solvent was removed by steam condensation treatment and dried to obtain the low cis polybutadiene rubber C1 of the present invention. The structure and properties of the low cis polybutadiene rubber C1 were measured. The results are shown in Table 3.

[0134] Example 2

[0135] The low cis polybutadiene rubber LCBR2A solution and the low cis polybutadiene rubber LCBR2B were mixed at a dry rubber weight ratio of LCBR 2A to LCBR 2B of 1:3, and the organic solvent was removed by steam condensation treatment and dried to obtain the low cis polybutadiene rubber C2 of the present invention. The structure and properties of the low cis polybutadiene rubber C2 were measured. The results are shown in Table 3.

[0136] Example 3

[0137] The low cis polybutadiene rubber LCBR3A solution and the low cis polybutadiene rubber LCBR3B were mixed at a dry rubber weight ratio of LCBR 3A to LCBR 3B of 1:3, and the organic solvent was removed by steam condensation treatment and dried to obtain the low cis polybutadiene rubber C3 of the present invention. The structure and properties of the low cis polybutadiene rubber C3 were measured. The results are shown in Table 3.

[0138] Example 4

[0139] The low cis polybutadiene rubber LCBR4A solution and the low cis polybutadiene rubber LCBR4B were mixed at a dry rubber weight ratio of LCBR 4A to LCBR4B of 1:3, and the organic solvent was removed by steam condensation treatment and dried to obtain the low cis polybutadiene rubber C4 of the present invention. The structure and properties of the low cis polybutadiene rubber C4 were measured. The results are shown in Table 3.

[0140] Example 5

[0141] A low-cis polybutadiene rubber LCBR5A solution and a low-cis polybutadiene rubber LCBR5B were mixed at a dry rubber weight ratio of LCBR 5A to LCBR 5B of 1:3, and the organic solvent was removed by steam condensation treatment and dried to obtain the low-cis polybutadiene rubber C5 of the present invention. The structure and properties of the low-cis polybutadiene rubber C5 were measured. The results are shown in Table 3.

[0142] Example 6

[0143] The low cis polybutadiene rubber LCBR6A solution and the low cis polybutadiene rubber LCBR6B were mixed at a dry rubber weight ratio of LCBR 6A to LCBR 6B of 1:3, and the organic solvent was removed by steam condensation treatment and dried to obtain the low cis polybutadiene rubber C6 of the present invention. The structure and properties of the low cis polybutadiene rubber C6 were measured. The results are shown in Table 3.

[0144] Example 7

[0145] The low cis polybutadiene rubber LCBR7A solution and the low cis polybutadiene rubber LCBR7B were mixed at a dry rubber weight ratio of LCBR 7A to LCBR7B of 1:3, and the organic solvent was removed by steam condensation treatment and dried to obtain the low cis polybutadiene rubber C7 of the present invention. The structure and properties of the low cis polybutadiene rubber C7 were measured. The results are shown in Table 3.

[0146] Example 8

[0147] The method described in Example 1 is used, except that low-cis polybutadiene rubber LCBR7B replaces LCBR1B in Example 1. The organic solvent is removed by steam condensation and dried to obtain low-cis polybutadiene rubber C8 of the present invention. The structure and properties of the rubber C8 are measured. The results are shown in Table 3.

[0148] Example 9

[0149] The method described in Example 1 is used, except that low-cis polybutadiene rubber LCBR7A replaces LCBR1A in Example 1, and the organic solvent is removed by steam condensation treatment and dried to obtain low-cis polybutadiene rubber C9 of the present invention. The structure and properties of the rubber are measured, and the results are shown in Table 3.

[0150] Example 10

[0151] The method described in Example 1 is different in that LCBR 1A and LCBR 1B are mixed at a dry rubber weight ratio of 1:2.5, the organic solvent is removed by steam condensation treatment and the rubber is dried to obtain the low-cis polybutadiene rubber C10 of the present invention, and the structure and properties of the low-cis polybutadiene rubber C10 are measured. The results are shown in Table 3.

[0152] Embodiment 11

[0153] The method described in Example 1 is different in that LCBR 1A and LCBR 1B are mixed at a dry rubber weight ratio of 1:3.5, the organic solvent is removed by steam condensation treatment and the rubber is dried to obtain the low-cis polybutadiene rubber C11 of the present invention. The structure and properties of the low-cis polybutadiene rubber C11 are measured. The results are shown in Table 3.

[0154] Example 12

[0155] The method described in Example 1 is different in that LCBR 1A and LCBR 1B are mixed at a dry rubber weight ratio of 1:4.5, the organic solvent is removed by steam condensation treatment and the rubber is dried to obtain the low cis polybutadiene rubber C12 of the present invention, and the structure and properties of the low cis polybutadiene rubber C12 are measured. The results are shown in Table 3.

[0156] Comparative Example 1

[0157] A low-cis polybutadiene rubber LCBR8A solution and a low-cis polybutadiene rubber LCBR8B were mixed at a dry rubber weight ratio of LCBR 8A to LCBR 8B of 1:3, and the organic solvent was removed by steam condensation treatment and dried to obtain the low-cis polybutadiene rubber DB1 of the present invention. The structure and properties of the low-cis polybutadiene rubber DB1 were measured, and the results are shown in Table 3.

[0158] Comparative Example 2

[0159] A low-cis polybutadiene rubber LCBR9A solution and a low-cis polybutadiene rubber LCBR9B were mixed at a dry rubber weight ratio of LCBR 9A to LCBR 9B of 1:3, and the organic solvent was removed by steam condensation treatment and dried to obtain the low-cis polybutadiene rubber DB2 of the present invention. The structure and properties of the low-cis polybutadiene rubber DB2 were measured. The results are shown in Table 3.

[0160] Comparative Example 3

[0161] A low-cis polybutadiene rubber LCBR10A solution and a low-cis polybutadiene rubber LCBR10B were mixed at a dry rubber weight ratio of LCBR 10A to LCBR10B of 1:3, and the organic solvent was removed by steam condensation treatment and dried to obtain the low-cis polybutadiene rubber DB3 of the present invention. The structure and properties of the low-cis polybutadiene rubber DB3 were measured, and the results are shown in Table 3.

[0162] Comparative Example 4

[0163] The low cis polybutadiene linear polymers in LCBR 1C, LCBR 1C and LCBR 3C were mixed at a dry rubber weight ratio of 1:52.9:23.1 to obtain a low cis polybutadiene rubber linear copolymer, and the structure and properties of the copolymer were measured. The results are shown in Table 3.

[0164] Table 3

[0165]

[0166]

[0167] Table 3

[0168]

[0169] It can be seen from Table 3 that the viscosity of the 5wt% styrene solution of the low cis polybutadiene rubber with trimodal molecular weight distribution obtained in the present invention is between 80-128cp, the gel content is not higher than 150ppm, and the chromaticity is low, so that the low cis polybutadiene rubber of the present invention is particularly suitable for HIPS modification.

[0170] Test Example 1

[0171] 100 g of low-cis polybutadiene rubber C1, 150 g of ethylbenzene and 1100 g of styrene monomer were mixed, and then 45 g of mineral oil and 0.2 g of tert-butyl peroxy-2-ethylhexyl carbonate were added and mixed, and polymerized at a stirring rate of 300 rpm and a polymerization temperature of 105° C. for 2 h, and then heated to 120° C. for polymerization for 2 h; at a stirring rate of 100 rpm, the temperature was raised to 135° C. for polymerization for 2 h, and finally the temperature was raised to 150° C. for polymerization for 2 h, and the reaction product was subjected to vacuum flash evaporation to remove unreacted monomers and solvents to obtain HIPS resin P1.

[0172] The HIPS resin P1 was dried and then its structure and performance were measured. The results are shown in Table 4.

[0173] Test Example 2

[0174] 120g of low-cis polybutadiene rubber C2, 120g of xylene and 1100g of styrene monomer were mixed, and then 50g of mineral oil and 0.2g of azobisisobutyronitrile were added and mixed, and the mixture was polymerized at a stirring rate of 350rpm and a polymerization temperature of 110°C for 1.5h, and then the mixture was heated to 120°C for polymerization for 2.5h; at a stirring rate of 200rpm, the mixture was heated to 130°C for polymerization for 1.5h, and finally the mixture was heated to 155°C for polymerization for 2h. The reaction product was subjected to vacuum flash evaporation to remove unreacted monomers and solvents to obtain HIPS resin P2.

[0175] The structure and performance of the HIPS resin P2 were measured after drying. The results are shown in Table 4.

[0176] Test Example 3-11

[0177] The method described in Test Example 1 is different in that low cis polybutadiene rubbers C3-C12 are used instead of low cis polybutadiene rubber C1, so that the reaction products are subjected to vacuum flash evaporation and unreacted monomers and solvents are removed to obtain HIPS resins P3-P12 respectively.

[0178] The HIPS resins P3-P12 were dried and then their structures and properties were measured. The results are shown in Table 4.

[0179] Comparative test examples 1-4

[0180] The method described in Test Example 1 is different in that low cis polybutadiene rubbers DC1-DC4 are used instead of low cis polybutadiene rubber C1, so that the reaction products are subjected to vacuum flash evaporation and unreacted monomers and solvents are removed to obtain HIPS resins DP1-DP4 respectively.

[0181] The HIPS resins DP1-DP4 were dried and then their structures and properties were measured. The results are shown in Table 4.

[0182] Comparative test examples 5-7

[0183] The method described in Test Example 1 is used, except that Asahi Chemical's low-cis polybutadiene rubber 720A, 35AE and 55AE are used instead of low-cis polybutadiene rubber C1, so that the reaction products are subjected to vacuum flash evaporation and unreacted monomers and solvents are removed to obtain HIPS resins DP5-DP7 respectively.

[0184] The HIPS resins DP5-DP7 were dried and then their structures and properties were measured. The results are shown in Table 4.

[0185] Table 4

[0186]

[0187] It can be seen from Table 4 that by using the low-cis polybutadiene containing the present invention as a toughening agent, a HIPS resin with strong impact resistance and high gloss can be obtained. The HIPS resin obtained by the present invention has greatly improved impact resistance and gloss compared to the HIPS resin obtained by using the popular toughening agent on the market.

[0188] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A low-cis polybutadiene rubber, characterized in that: The number average molecular weight of the low cis polybutadiene rubber presents a trimodal distribution, wherein the first peak number average molecular weight is 310,000-360,000 g / mol, the second peak number average molecular weight is 120,000-150,000 g / mol, and the third peak number average molecular weight is 36,000-48,000 g / mol; wherein the peak area of ​​the first peak is 21%-44%, the peak area of ​​the second peak is 51%-79%, and the peak area of ​​the third peak is 0.4%-8%; The low-cis polybutadiene rubber is coupled low-cis polybutadiene rubber.

2. The low-cis polybutadiene rubber according to claim 1, wherein The number average molecular weight of the first peak is 320,000-355,000 g / mol, preferably 330,000-350,000 g / mol; the peak area of ​​the first peak is 25%-40%, preferably 27%-36%; Preferably, the number average molecular weight of the second peak is 125,000-145,000 g / mol, preferably 130,000-140,000 g / mol; the peak area of ​​the second peak is 57%-75%, preferably 62%-72%; Preferably, the number average molecular weight of the third peak is 37,000-46,000 g / mol, preferably 38,000-45,000 g / mol; the peak area of ​​the third peak is 0.6%-5%, preferably 0.8%-3%.

3. The low-cis polybutadiene rubber according to claim 1 or 2, wherein The viscosity of the 5wt% styrene solution of the low cis polybutadiene rubber at 25°C is 80-130cp, preferably 90-110cp; Preferably, the Mooney viscosity ML (1+4min, 100°C) of the low cis polybutadiene rubber is 40-55; Preferably, the gel content of the low-cis polybutadiene rubber is not higher than 150 ppm, preferably not higher than 100 ppm, more preferably not higher than 80 ppm; Preferably, the vinyl content of the low-cis polybutadiene rubber is 8%-20wt%, preferably 10%-16wt%; Preferably, the chromaticity of a 5 wt % styrene solution of the low-cis polybutadiene rubber is less than or equal to 15 APHA, preferably less than or equal to 8 APHA, and more preferably less than or equal to 5 APHA.

4. A method for preparing low-cis polybutadiene rubber, characterized in that: The method comprises the following steps: Mixing a low-cis polybutadiene rubber solution BR1 and a low-cis polybutadiene rubber solution BR2, and removing the solvent to obtain the low-cis polybutadiene rubber; The dosage of the low cis polybutadiene rubber solution BR1 and the low cis polybutadiene rubber solution BR2 is such that the number average molecular weight of the prepared low cis polybutadiene rubber presents a trimodal distribution, wherein the first peak number average molecular weight is 310,000-360,000 g / mol, the second peak number average molecular weight is 120,000-150,000 g / mol, and the third peak number average molecular weight is 36,000-48,000 g / mol; wherein the peak area of ​​the first peak is 21%-44%, the peak area of ​​the second peak is 51%-79%, and the peak area of ​​the third peak is 0.4%-8%; The low-cis polybutadiene rubber is coupled low-cis polybutadiene rubber.

5. The preparation method according to claim 4, wherein The preparation method of the low-cis polybutadiene rubber solution BR1 comprises the following steps: Under anionic polymerization conditions, butadiene 1 is first polymerized in an organic solvent in the presence of a first organic lithium initiator and a first structure regulator to obtain a polymerization solution 1; the polymerization solution 1 is contacted with a first coupling agent to perform a first coupling reaction, and then a first terminator is added to obtain a low-cis polybutadiene rubber solution BR1.

6. The preparation method according to claim 4, wherein The preparation method of the low-cis polybutadiene rubber solution BR2 comprises the following steps: Under anionic polymerization conditions, butadiene 2 is subjected to a second polymerization in an organic solvent in the presence of a second organic lithium initiator and a second structure regulator to obtain a polymerization solution 2; the polymerization solution 2 is contacted with a second coupling agent to perform a second coupling reaction, and then a second terminator is added to obtain a low-cis polybutadiene rubber solution BR2.

7. The preparation method according to claim 5, wherein: The molar ratio of butadiene 1 to the first organic lithium initiator is 650-900:1, preferably 680-850:1, more preferably 700-830:1; Preferably, the molar ratio of the first coupling agent to the first organic lithium initiator is 0.2-0.3:1, preferably 0.21-0.26:

1.

8. The preparation method according to claim 6, wherein: The molar ratio of the butadiene 2 to the second organic lithium initiator is 2200-2800:1, preferably 2300-2700:1, more preferably 2400-2600:1; Preferably, the molar ratio of the second coupling agent to the second organic lithium initiator is 0.1-0.17:1, preferably 0.1-0.15:

1.

9. The preparation method according to any one of claims 4 to 8, wherein: The dry rubber weight ratio of the low-cis polybutadiene rubber solution BR1 to the low-cis polybutadiene rubber solution BR2 is 1:2.5-4, preferably 1:2.8-3.

5.

10. The preparation method according to any one of claims 5 to 9, wherein: The first organic lithium initiator and / or the second organic lithium initiator are each independently a compound represented by Formula I, R 1 Formula I of Li Among them, R 1 Selected from C1-C 10 The alkyl group; Preferably, the first organic lithium initiator and / or the second organic lithium initiator are each independently selected from at least one of n-butyl lithium, sec-butyl lithium, isobutyl lithium and tert-butyl lithium; more preferably n-butyl lithium and / or sec-butyl lithium, further preferably n-butyl lithium; Preferably, the first coupling agent and / or the second coupling agent are each independently a silane coupling agent, preferably at least one of silicon tetrachloride, silicon tetrabromide and tin tetrachloride, more preferably silicon tetrachloride.

11. The preparation method according to any one of claims 5 to 10, wherein: The first terminator and / or the second terminator are each independently selected from at least one of C1-C4 alcohols, organic acids and carbon dioxide; preferably selected from at least one of isopropanol, stearic acid, citric acid and carbon dioxide; more preferably carbon dioxide.

12. The preparation method according to any one of claims 5 to 11, wherein: The conditions of the first polymerization include: temperature of 0-100°C, preferably 40-100°C, more preferably 50-100°C; time of 20-100min, preferably 30-60min; Preferably, the conditions of the first coupling reaction include: temperature of 60-90°C and time of 20-40 min; Preferably, the conditions of the second polymerization include: temperature of 0-100°C, preferably 40-100°C, more preferably 50-100°C; time of 20-100 min, preferably 30-60 min; Preferably, the conditions of the second coupling reaction include: temperature of 60-90° C. and time of 20-40 min.

13. A method for preparing a HIPS resin, the method comprising: In a benzene solvent, styrene and a toughening agent are polymerized in the presence of a free radical initiator; wherein the toughening agent contains the low cis polybutadiene rubber described in any one of claims 1 to 3; wherein the benzene solvent is selected from at least one of unsubstituted or C1-C4 alkyl-substituted benzenes.

14. The method according to claim 13, wherein: Based on the total weight of styrene, benzene solvent and toughening agent, the amount of the benzene solvent is 6wt%-18wt%; Preferably, the weight ratio of styrene to toughening agent on a dry weight basis is 550-1900:100, preferably 600-1600:100, more preferably 800-1400:100, and even more preferably 900-1300:

100.

15. The method according to claim 13 or 14, wherein: The free radical initiator is at least one of diacyl peroxide, peroxydicarbonate, peroxycarboxylate, alkyl peroxide and azobisnitrile compounds, preferably at least one of peroxy-2-ethylhexyl tert-butyl tert-carbonate, dibenzoyl peroxide, di-o-methylbenzoyl peroxide, tert-butyl perbenzoate, diisopropylbenzene peroxide, azobisisobutyronitrile and azobisisoheptonitrile; Preferably, the weight ratio of the amount of styrene to the amount of the free radical initiator is 2500-12000:1, more preferably 3000-9500:1, more preferably 4000-9000:1, and further preferably 5000-8500:

1.

16. The method according to any one of claims 13 to 15, wherein: The polymerization reaction conditions include: temperature of 100-150°C and time of 7-9h; Alternatively, the polymerization reaction conditions include: first reacting at 100-110° C. for 1-3 h, then reacting at 115-125° C. for 1-3 h, then reacting at 130-140° C. for 1-3 h, and finally reacting at 145-155° C. for 1-3 h.

17. The preparation method according to claim 16, wherein: The polymerization conditions include: First react at 105-110°C for 1.5-2.5h, then react at 120-125°C for 1.5-2.5h, then react at 130-135°C for 1.5-2.5h, and finally react at 150-155°C for 1.5-2.5h.

18. A HIPS resin obtained by the method according to any one of claims 13 to 17.

19. The HIPS resin according to claim 18, wherein The content of the structural unit of styrene in the HIPS resin is 85wt%-95wt%, preferably 88wt%-94wt%; Preferably, the weight average molecular weight of the HIPS resin is 150,000-400,000 g / mol, preferably 200,000-300,000 g / mol; Preferably, the molecular weight distribution coefficient of the HIPS resin is 2-2.9; Preferably, the Izod impact strength of the HIPS resin is 14 kJ / m 2 Above, preferably 15 kJ / m 2 More preferably 15-17 kJ / m 2 ; Preferably, the surface glossiness of the HIPS resin at 60° is 69 or more, preferably 70 or more, and more preferably 75 or more.

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