Asymmetric star-shaped hydrogenated block copolymer and preparation method and application thereof

Abstract

The present invention discloses an asymmetric star-shaped hydrogenated block copolymer and a preparation method and application thereof. The structural formula of the asymmetric star-shaped hydrogenated block copolymer is: (S1EBS2)nM. S1 represents a polymer segment of styrene monomer; S2 represents a polymer segment of styrene and divinylbenzene monomer copolymerization; and the molecular weight of the S1 polymer segment is greater than that of the S2 polymer segment; the polymer is mainly obtained by polymerization and coupling to obtain (S1BS2)nM, followed by a hydrogenation step. The present invention overcomes the technical difficulty of low styrene coupling efficiency at the end of the polymer arm, and prepares a sealing material with low compression deformation, high resilience and long service life, which is widely used in the field of sealing parts.

Description

Technical Field

[0001] The invention relates to an asymmetric hydrogenated star-shaped polystyrene-polyconjugated diene-b-polystyrene block copolymer having excellent weather resistance, low compression deformation and high resilience, and a preparation method and application thereof, belonging to the field of polymers. Background Art

[0002] The main functions of seals are shock absorption, noise reduction, heat insulation, sealing, dust and water resistance, so they must have good corrosion resistance, weather resistance, chemical resistance, low compression deformation and high resilience. Commonly used sealing strip materials include modified PVC, chloroprene rubber (CR), nitrile rubber (NBR), polyurethane elastomer (PU), thermoplastic vulcanizate (TPV), ethylene propylene rubber and thermoplastic elastomer rubber, as well as silicone sealing strips.

[0003] PVC sealing strips, chloroprene rubber, and nitrile rubber have poor ozone and weather resistance; polyurethane elastomers have poor hydrolysis resistance. In recent years, modified PVC sealing strips have a high market share in China. The key is that they are low in cost, raw materials are easily available, and they have good mechanical properties and resistance to aging, heat, oil, and chemical corrosion. However, modified PVC is not suitable for use at low temperatures, has poor storage stability, and is not environmentally friendly. It is not suitable for occasions with high requirements such as sealing and preserving food. Another commonly used sealing strip material is EPDM, which has excellent heat resistance, cold resistance, ozone resistance, UV resistance, and wear resistance, especially good rebound performance, but has the disadvantages of slow vulcanization speed and poor self-adhesion and mutual adhesion. Thermoplastic vulcanizates are not very resistant to compression deformation and abrasion. The mechanical strength of silicone sealing strips is the worst among rubber materials, and they are not oil resistant. Only thermoplastic elastomer rubbers have good elasticity and excellent wear resistance, weather resistance, chemical resistance and mechanical properties, and are recyclable and reusable materials. However, thermoplastic materials such as the common ordinary structure SBS and SEBS on the market have large compression deformation, are not oil resistant, and have poor weather resistance, and their aging resistance is far inferior to that of the latter, resulting in poor sealing performance and short service life of their products. Although the ordinary structure SEBS has improved weather resistance and excellent aging resistance, it has large compression deformation, and the resulting seals cannot meet the requirements of high sealing performance in areas.

[0004] Most of the patents for thermoplastic materials used in seals mention the use of a composition for preparation, such as CN1388813 of Mitsui Co., Ltd., which discloses a cross-linkable rubber composition. Specifically, a composition is disclosed, which includes ethylene / a-olefin / non-conjugated polyene random copolymer rubber, SiH compounds with two or more SiH groups, and if necessary, platinum catalysts, reaction inhibitors and / or silane coupling agents; and sealing compound rubber, packaging materials, and coating materials containing the composition. CN1388818 provides a sealant composition for plastic liquid crystal display elements, which can be applied to thin plate hot pressing bonding method and can produce plastic liquid crystal display elements with reliability in high temperature and high humidity environments.

[0005] Patents on SEBS focus on hydrogenation catalysts, hydrogenation aids, base rubber regulators and metal ion removal, such as CN01816364.5, CN201110008911.5.A, CN1062909A, CN1058269C, etc. Patents on SEBS structure are relatively few, such as CN1044107A mentions a linear alternating block copolymer B 1 -TA 1 -B 2 -A 2 , where B 1 , B 2 A is a block composed of ethylene-butene-1 copolymer or ethylene-propylene copolymer; 1 , A 2 is a polyvinyl aromatic block; T is a ternary copolymer chain segment formed by statistically connected ethylene-propylene-vinyl aromatic monomer units or ethylene-butene-1-vinyl aromatic monomer units, in which the ternary copolymer structure is difficult to control and the test results are difficult to repeat. For example, ZL201210469592.2 mentions a patent for a symmetrical star-shaped hydrogenated block polymer (SEBS) nM, in which the molecular weights of the polyvinyl aromatics in the two blocks are the same within the error range. In order to improve the coupling efficiency, a small amount of conjugated diene polymerization must be added to the fourth segment on the basis of the third segment of polystyrene, and the operation is more complicated.

[0006] Sealing strips, sealing rings and other seals made of SEBS as raw material can maintain good softness and elasticity when used for a long time in a wide temperature range. They are excellent in oxidation resistance, weather resistance and high temperature performance. In particular, the finished product has good self-adhesive properties and does not require adhesives during installation. They can be connected to each other, eliminating the connection process, and the scraps can be recycled and reused, meeting environmental protection requirements.

[0007] After the traditional block copolymer SEBS is processed into sealing strips, its mechanical properties are greatly reduced and the compression permanent deformation is large, which cannot meet the requirements of sealing strips. Summary of the invention

[0008] The object of the present invention is to provide an asymmetric star-shaped hydrogenated butadiene styrene block copolymer with high molecular weight and narrow molecular weight distribution.

[0009] Another object of the present invention is to provide a method for preparing the star-shaped hydrogenated butadiene styrene block copolymer.

[0010] The third object of the present invention is to provide the above-mentioned asymmetric star-shaped hydrogenated butadiene styrene block copolymer for use in preparing seals with low compression deformation, high resilience, excellent weather resistance and aging resistance.

[0011] The present invention provides an asymmetric star-shaped hydrogenated butadiene styrene block copolymer having a structure shown in Formula I:

[0012] (S 1 EBS 2 )nM

[0013] Formula I

[0014] S 1 EBS 2 is the polymer arm, where S 1 Represents a polymer chain segment of styrene monomer (styrene block);

[0015] S 2 represents a polymer segment of styrene and divinylbenzene monomer copolymerization (styrene / divinylbenzene copolymerization block); and S 1 The molecular weight of the polymer chain segment is greater than S 2 polymer segments;

[0016] EB is a hydrogenated polybutadiene polymer segment, wherein E represents a hydrogenated 1,2-polybutadiene polymer segment; B represents a hydrogenated 1,4-polybutadiene polymer segment;

[0017] M is the core of the star-shaped structure, and the core is the central atom or atom group linking the polymer arms;

[0018] n represents the number of arms of the star structure, and n is not less than 2.

[0019] The molecular weight of the polymer segment S1 of the present invention is greater than that of the polymer segment S2, and 2 The polymer chain segment is a polymer chain segment copolymerized with styrene and divinylbenzene monomers; the star polymer composed of asymmetric polymer arms with such structure and molecular weight arrangement has excellent aging resistance and good heat resistance and processing performance. It is used for sealing strips, sealing rings, sealing gaskets or sealants to prepare seals with excellent cold-resistant, heat-resistant, weather-resistant, ozone-resistant, UV-resistant properties and long service life.

[0020] The asymmetric star-shaped hydrogenated butadiene styrene block copolymer of the present invention is a polymer having a structural formula II before hydrogenation;

[0021] (S 1 BS 2 )nM

[0022] Formula II.

[0023] As a preference, S 1 The number average molecular weight is 6000-100000.

[0024] As a preference, S 2 The number average molecular weight is 6000-40000.

[0025] Preferably, the number average molecular weight of B is 10,000 to 150,000.

[0026] In the present invention, it is necessary to ensure that S 1 The molecular weight is greater than S 2 .

[0027] As a preference, S 1 :S 2 =9:1~1.5:1 (mass ratio).

[0028] S 1 EBS 2 In the arm, the mass content of styrene is 15% to 50%, preferably 20% to 40%, and more preferably 25% to 35%. The balance is butadiene, and its mass content is, for example, 50% to 85%; preferably 60% to 80%; and more preferably 65% ​​to 75%. If the mass content of the styrene monomer unit is less than 15%, the cross-linking density with polystyrene as the physical cross-linking point is too low, the tear strength of the obtained sealing strip is too low, and the sealing strip is easy to break; if the mass content is higher than 50%, the plasticity of the obtained sealing strip is too strong, the rubber property is poor, and its compression deformation and tear deformation are increased.

[0029] As a preference, S 1 EBS 2 The mass content of divinylbenzene in the arms is 0.2% to 2%, more preferably 0.5% to 1.5%.

[0030] As a preference, S 1 EBS 2 In the arms, the 1,2-structure content of butadiene is 10 to 75%, preferably 30 to 60%, of the butadiene chain segment.

[0031] Preferably, the degree of hydrogenation of the polybutadiene segments (EB) is not less than 95%, and the degree of hydrogenation of the vinyl aromatic segments (S1 and S2) is not more than 5%.

[0032] Preferably, M in the polymer structure is selected from Si, Sn, C 4～18 Alkyl or C 8～22 Aromatic group.

[0033] Preferably, n is an integer of 2 to 10, preferably 3 to 6; the coupling efficiency is 80 to 98%, preferably 85 to 92%.

[0034] In the present invention, an asymmetric structure is adopted, namely S 1 BS 2 Medium S 2 The molecular weight is less than S 1 , ensure S 2 The steric hindrance is less than that of S 1 , then in S 2 When other conditions are the same, compared with S 1 With S 2 When the molecular weight is the same, a higher coupling degree and coupling efficiency can be achieved.

[0035] Preferably, the number average molecular weight (M) of the asymmetric star-shaped hydrogenated block copolymer is n ) is 100000-640000; preferably 120000-640000, more preferably 160000-350000. The molecular weight distribution of the asymmetric star-shaped hydrogenated block copolymer is 1.00-1.20; preferably 1.01 to 1.20, more preferably 1.01 to 1.15, more preferably 1.01-1.10. At the preferred number average molecular weight, the asymmetric star-shaped hydrogenated block copolymer has better performance. When the number average molecular weight is lower than 120,000, the molecular weight of each PS and PB block is too small, the phase separation is incomplete, the PS segment cannot form physical crosslinking points, and even cold flow occurs, the mechanical properties are too poor, and it is not suitable for sealing parts; higher than 640,000, the physical crosslinking points aggregated with polystyrene are too large, the fluidity is poor, and its processing performance is not good.

[0036] In the present invention, in the polymerization S 2 A small amount of divinylbenzene is added to the styrene monomer in the segment. By utilizing the two vinyl groups on a divinylbenzene molecule, four polymer chains can be connected together to form a more complete cross-linked network, thereby improving the heat resistance of the resulting product.

[0037] In the copolymer of the present invention, S 1 EBS 2 The 1,2-structure content of butadiene in the arm was determined by H-NMR and calculated by the absorption peak area in the NMR spectrum.

[0038] Formula: 1,2-Structure%=I 1 / (I 1 / 2+I 2 +I3 )*100%, obtain.

[0039] in,

[0040] I 1 represents vinyl (=CH 2 ) on the area of ​​the hydrogen absorption peak;

[0041] I 2 It represents the hydrogen absorption peak area on the double bond (-CH=CH-) of polybutadiene;

[0042] I 3 It represents the hydrogen absorption peak area on the vinyl group (-CH=).

[0043] The present invention provides a method for preparing the above-mentioned asymmetric star-shaped hydrogenated butadiene styrene block copolymer, comprising the following steps:

[0044] Step (1): firstly add the solvent, activator and regulator into a reaction kettle, raise the temperature to a suitable temperature, add styrene monomer and initiator and initiate polymerization;

[0045] Step (2): after the reaction of step (1) is complete, butadiene monomer is added for polymerization;

[0046] Step (3): After the reaction of step (2) is completed, divinylbenzene and the remaining styrene monomer are mixed evenly and then added to the reactor. After the polymerization is completed, a coupling agent is added for coupling. After the coupling is completed, the rubber is pressed into a hydrogenation kettle, and a co-catalyst and a main catalyst are added to the kettle for catalytic hydrogenation. After the hydrogenation is completed, water is added to terminate the process, and an antioxidant is added to condense and dry the product.

[0047] This method can control the 1,2-structural unit in the polybutadiene unit in the polymer arm to be within a certain range and to be evenly distributed in the polybutadiene unit, so as to achieve better mechanical properties, smaller compression deformation and higher resilience when adding solid fillers, white oil and some additives to prepare seals. A small amount of divinylbenzene monomer is also added to the method for polymerization. The two vinyl groups on one molecule can be polymerized with four styrene monomers respectively. Compared with the polymerization of simple styrene monomers, a more complete three-dimensional cross-linked network can be formed to improve its heat resistance. The preparation of the asymmetric star-shaped hydrogenated block copolymer overcomes the difficulty of low coupling efficiency of the active polystyrene chain end on the basis of the symmetric (SEBS) nM. The two polystyrene chain ends are asymmetric, that is, one end has a large molecular weight of polystyrene and the other end has a small molecular weight of polystyrene. The coupling is carried out at the end with a small molecular weight by utilizing the advantage that its steric hindrance is smaller than that at the end with a large molecular weight, which can ensure a high coupling degree and coupling efficiency. Compared with the method of adding a fourth segment of polyconjugated diene on the basis of the third segment of polystyrene and then coupling, the operation is simple, and the coupling degree and coupling efficiency of the obtained polymer can reach a satisfactory level.

[0048] Preferably, in step (1), after adding the solvent, the temperature is controlled to be 30-100° C.; styrene monomer, activator, regulator and initiator are added and polymerization is initiated and then polymerized for 20-30 minutes.

[0049] Preferably, in step (2), after the styrene monomer in step (1) is completely reacted, butadiene monomer is added to control the reaction temperature at 65 to 75° C. and polymerize for another 20 to 40 minutes.

[0050] Preferably, in step (3), after the butadiene monomer in step (2) has reacted, a mixture of divinylbenzene and styrene monomers is added and polymerized for 20 to 40 minutes; after the polymerization is completed, a coupling agent is added and coupled for 10 to 30 minutes; the rubber is pressed into a hydrogenation kettle and hydrogen is passed; a co-catalyst and a main catalyst are added and catalytic hydrogenation is carried out for 60 to 150 minutes.

[0051] The activator is tetrahydrofuran, and the amount used is 20-1000 mg tetrahydrofuran / kg solvent by mass content in the solvent, preferably 40-200 mg tetrahydrofuran / kg solvent.

[0052] The regulator comprises: one or a combination of tetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, pentamethyldiethylenetriamine or furfurylamine, furfuryl ether and furfuryl alkane, and the dosage of the regulator is 30-500 mg / kg solvent.

[0053] The solvent includes: cyclohexane or normal hexane or a combination of the two, and the amount of the solvent used is 70-90% of the mass concentration of the reaction system.

[0054] The initiator is various organic lithium compounds for anionic polymerization, such as n-butyl lithium or sec-butyl lithium.

[0055] The coupling agent includes: silane, stannane, alkylene oxide, C 4～18 Unsaturated alkanes or C 8～22 Aromatic dienes; such as epoxidized soybean oil, divinylbenzene, etc.

[0056] The hydrogenation main catalyst includes Ziegler-Natta catalyst and metallocene catalyst, and the main catalyst dosage is 0.05-3.0 mmol / 100g polymer.

[0057] The hydrogenation catalyst comprises benzoic acid esters, and the amount of the catalyst is 0.02-1.0 mmol / 100 g polymer.

[0058] The invention sequentially polymerizes styrene-butadiene-styrene / divinylbenzene blocks on an active chain, couples them into a multi-arm star copolymer, and then hydrogenates them to obtain an asymmetric star hydrogenated block copolymer; that is, an asymmetric star hydrogenated block copolymer with excellent performance is obtained.

[0059] The asymmetric star-shaped polymer synthesized in the present invention has technical difficulties in synthesizing compared with the general star-shaped polymer. 1 BS 2 )nM The active chain end before coupling is a polystyrene / divinylbenzene block. Due to the large steric hindrance, the coupling degree and coupling efficiency after coupling are low. The present invention is designed in an asymmetric form, and coupling is carried out at the end with a small molecular weight, which is conducive to the coupling reaction, thereby improving the coupling degree and coupling efficiency. Further hydrogenation is performed to obtain (S 1 EBS 2 Secondly, by controlling the reaction temperature and the type and amount of the regulator, the proportion of 1,2-polymerized diene units in the polybutadiene unit to the total diene units is controlled within a certain range and is distributed more evenly.

[0060] This structure increases (S 1 EBS 2 )nM material, where a small amount of uncoupled S 1 EBS 2 The small molecules act as self-lubricants during the compression process, making the physical cross-linked network of SEBS difficult to be destroyed, thereby making it have low compression deformation and high resilience. When a small amount of divinylbenzene is added for copolymerization, the resulting structure is as shown in Formula III, while the common structure polymerization unit structure without divinylbenzene is as shown in Formula IV.

[0061]

[0062] Compared with Formula Ⅳ, Formula Ⅲ forms a more complete three-dimensional cross-linked network structure, which can limit the activity of the molecular chain to a certain extent and enhance the heat resistance of the material. By adjusting the agent and controlling the reaction temperature, the appropriate amount of 1,2-polymerization units in the diene polymerization unit is controlled and the 1,2-polymerization units are distributed more evenly in the entire diene polymerization unit. This structure can make the hydrogenated product have a certain elasticity.

[0063] The present invention measures the molecular weight before and after coupling and the mass percentage of coupled polymer and the mass percentage of uncoupled polymer by gel permeation chromatography, and then calculates the coupling degree and coupling efficiency according to the following formula.

[0064] Coupling degree = number average molecular weight after coupling / number average molecular weight before coupling

[0065] Coupling efficiency (%) = coupled polymer mass percentage / (coupled polymer mass percentage+uncoupled polymer mass percentage)*100%.

[0066] By controlling the amount of the regulator added and the polymerization temperature of the diene polymerization section, the 1,2-structure content can be controlled within the desired range and more evenly distributed in the entire diene polymerization section.

[0067] The asymmetric star-shaped hydrogenated butadiene styrene block copolymer prepared according to the method of the present invention has the structure (S 1 EBS 2 )nM, SiCl 4 or SnCl 4 When the coupling agent is divinylbenzene or other C 4～18 Unsaturated alkanes or C 8～22 When the aromatic diene is used as the coupling agent, the coupling degree can be arbitrarily adjusted between 2 and 10, preferably the coupling degree is 3 to 6, and the coupling efficiency is 80 to 98%.

[0068] The present invention provides an application of the above-mentioned asymmetric star-shaped hydrogenated butadiene styrene block copolymer, specifically an application of the asymmetric star-shaped hydrogenated butadiene styrene block copolymer as a preparation of seals, such as sealing strips, sealing rings and sealing gaskets, especially seals used in fields with high operating temperatures, long service life and high requirements for weather resistance and aging resistance.

[0069] The asymmetric star-shaped hydrogenated block copolymer of the present invention is used as a seal. The star-shaped hydrogenated copolymer of the present invention is mechanically blended with other blending materials according to the general process of seals, and then extruded and granulated by a twin-screw machine at high temperature without vulcanization and cold water cooling, and then directly injection molded by an injection molding machine to produce a sealing strip with low compression deformation, high resilience and long service life.

[0070] In the block copolymer of the present invention, the star-shaped hydrogenated styrene-butadiene block-styrene / divinylbenzene copolymer mainly exists in the polymer molecular chain in the form of blocks, and the PS phase and the PB phase can achieve good phase separation. 1 BS 2 Compared with the single-arm SB of ordinary star-shaped products, there is one more PS block. After coupling, each (S 1 BS 2 )nM molecules have n more PS blocks than (SB)nM, so the density of cross-linking points with PS as cross-linking points is significantly increased, and its mechanical properties are improved. 1 BS 2 The synthetic product does not contain SB, but is replaced by S 1 BS 2 And S 2 It contains polydivinylbenzene, and its cross-linking network is more complete and the network cross-linking density is higher, so that the cross-linking network will not be destroyed after filling with fillers or oil. Therefore, its compression permanent deformation is small and its resilience is large, and its mechanical properties do not decrease much, which is very suitable for use as seals.

[0071] In the present invention, the "low compression deformation" refers to the use of the present invention (S 1 EBS 2 )nM is used as a seal, and the compression permanent deformation of the seal is far lower than the standard of the seal. Specifically, the standard of "low compression deformation" is: the compression permanent deformation of the sealing strip tested by QC / T709-2004 standard is 12-36% (tested at 70℃ for 24h).

[0072] In the present invention, the "high resilience" refers to the (S 1 EBS 2 The specific standard of "high resilience" is: the permanent deformation at break of GB / T528-1998 standard test is 0-32%.

[0073] The term "coupling efficiency" in the present invention refers to the low molecular weight S 1 BS 2 Coupling to higher molecular weight (S 1 BS 2 )nM and the total low molecular weight S before adding coupling agent 1 BS 2 percentage. BRIEF DESCRIPTION OF THE DRAWINGS

[0074]

Figure 1

[0075]

Figure 2

[0076] The following examples are provided to illustrate the present invention but are not intended to limit the scope of the invention.

[0077] In the embodiments of the present invention, the molecular weight and molecular weight distribution were tested by Shimadzu LC-10AT series gel permeation chromatograph GPC; the degree of hydrogenation was tested by indirect iodine titration; the 1,2-structure content was measured by CDCl 3 As solvent, the Avance400 nuclear magnetic resonance instrument of Bruker of Switzerland was used for testing according to hydrogen nuclear magnetic resonance spectroscopy (HNMR); the tensile strength, tensile permanent deformation and tensile elongation were tested according to GB / T528-1998 standard; the compression permanent deformation was tested according to QC / T709-2004 standard.

[0078] The asymmetric star-shaped hydrogenated butadiene styrene block copolymer prepared by the method of the present invention has controllable molecular weight, 1,2-structure content of the polybutadiene segment can be controlled within a required range, the degree of hydrogenation can reach more than 98%, and both compression permanent deformation and tear permanent deformation are relatively low.

[0079] Table 1 Main properties of the asymmetric star-shaped hydrogenated butadiene styrene block copolymer of the present invention

[0080]

[0081] Example 1

[0082] Add 2.5 liters of cyclohexane and raffinate oil mixture (the mixing ratio of cyclohexane and raffinate oil is 9:1) into a 5 liter polymerization kettle purged with nitrogen, which contains 500 mg / kg of tetrahydrofuran solvent. Heat the mixture to 50°C, first add 67g of styrene and 0.20g of pentamethyldiethylenetriamine, and then add 3.57mmol of n-butyl lithium to initiate the reaction. After stirring and reacting for 20 to 30 minutes, add 150g of butadiene to the active polymer, control the reaction temperature at 65 to 75°C, stir and react for 20 to 40 minutes, then add 33g of styrene and 1.25g of divinylbenzene mixed monomer to the active polymer, stir and react for 20 to 30 minutes, then add 0.9mmol of coupling agent silicon tetrachloride, and stir and react for 10 to 30 minutes. After the polymerization is completed, the polymer is pressed into a 5-liter hydrogenation kettle, the temperature is controlled at 50-100°C, 68 mm g of methyl benzoate is added to the hydrogenation kettle, and the reaction is stirred for 5-20 minutes. Then 124 mm g of dicyclopentadiene titanium dichloride is added to the hydrogenation kettle, and the reaction is stirred for 60-120 minutes. 5 ml of water is added to terminate the reaction. 0.6% of an antioxidant based on the weight of the polymer is added to the reaction mixture and stirred for 5 minutes. Finally, the product is added to a mixture of steam and water, the solvent is evaporated, and the polymer is separated in a solid state and suspended in water. The solid is separated, the water is squeezed out with an extrusion dehydrator, and the volatilization is carried out in a drying oven to obtain an asymmetric star-shaped hydrogenated block copolymer (S 1 EBS 2 )nSi. The molecular weight of the copolymer is 220000 (Mn), the coupling degree is 3.11, the coupling efficiency is 88.9%, and the 1,2 structure content of the PB segment is 32.3%. The NMR spectrum is shown in Figure 1 .

[0083] Example 2

[0084] The implementation steps are the same as those in Example 1, except that the amount of each material added and the reaction temperature are changed. The amount of solvent is the same as that of tetrahydrofuran. In the first stage, 60 g of styrene and 0.25 g of tetramethylethylenediamine are added, and then 3.57 mmol of n-butyllithium is added to initiate the reaction. In the second stage, 175 g of butadiene is added, during which the reaction temperature is controlled at 50-65°C. In the third stage, a mixture of 15 g of styrene and 1.5 g of divinylbenzene is added to the active polymer, and then 0.9 mmol of coupling agent silicon tetrachloride is added for coupling. After the polymerization is completed, a hydrogenation reaction is carried out for 60-120 min, and 5 ml of water is added to terminate the reaction. 0.6% antioxidant based on the weight of the polymer is added to the reaction mixture. The solid is separated and devolatilized in a drying oven to obtain an asymmetric star-shaped hydrogenated block copolymer (S 1 EBS 2The molecular weight of the copolymer is 232000 (Mn), the coupling degree is 3.32, the coupling efficiency is 94.1%, and the 1,2-structure content of the PB segment is 53.6%.

[0085] Example 3

[0086] The steps and the amount of materials added are the same as those in Example 1 except for the regulator. The regulator is 0.48 g of tetrahydrofurfuryl alcohol ethyl ether, the coupling agent is divinylbenzene, and the amount of the coupling agent added is 1.4 g. The reaction temperature is controlled at 40 to 55° C., and the reaction is stirred for 40 to 60 minutes to obtain an asymmetric star-shaped hydrogenated block copolymer (S 1 EBS 2 )nDVB. The molecular weight of the copolymer is 347388 (Mn), the coupling degree is 6.15, the coupling efficiency is 83.57%, and the 1,2-structure content of the PB segment is 70.5%. The NMR spectrum is shown in Figure 2 .

[0087] Comparative Example 1

[0088] The steps and the amount of materials added are basically the same as those in Example 1, except that all the styrene monomers are added in one stage for polymerization, rather than being divided into two parts for polymerization in the first and third stages. After the polymerization of the conjugated diene monomers in the second stage is completed, a coupling agent is added to the third stage for coupling. The product is obtained by the same hydrogenation, termination, desolventization and drying methods as in Example 1. The obtained star-shaped hydrogenated block copolymer (SEB)nSi has a molecular weight of 240,000 (Mn), a coupling degree of 3.20, a coupling efficiency of 88.4%, and a 1,2-structure content of the PB segment of 33.5%.

[0089] Comparative Example 2

[0090] The steps and the amount of materials added are basically the same as those in Example 1, except that the styrene monomer is evenly divided into two parts, and the styrene monomer added in the first and third stages is the same. After the polymerization is completed, the same hydrogenation, termination, desolventization and drying methods as in Example 1 are adopted to obtain the product. The obtained symmetrical star-shaped hydrogenated block copolymer (SEBS)nSi has a molecular weight of 230,000 (Mn), a coupling degree of 2.89, a coupling efficiency of 80.4%, and a 1,2-structure content of the PB segment of 32.0%.

[0091] Comparative Example 3

[0092] The steps are basically the same as those in Example 1, except that the styrene monomer content is different, which is lower than 15% (13%). The product is obtained by the same hydrogenation, termination, desolvation and drying methods as in Example 1. The obtained star-shaped hydrogenated block copolymer (SEB)nSi has a molecular weight of 230,000 (Mn), a coupling degree of 3.18, a coupling efficiency of 89.4%, and a 1,2-structure content of the PB segment of 35.5%.

[0093] Comparative Example 4

[0094] The steps are basically the same as those in Example 1, except that the styrene monomer content is different and is higher than 50% (52%). The product is obtained by the same hydrogenation, termination, desolvation and drying methods as in Example 1. The obtained star-shaped hydrogenated block copolymer (SEB)nSi has a molecular weight of 230,000 (Mn), a coupling degree of 3.15, a coupling efficiency of 89.0%, and a 1,2-structure content of the PB segment of 35.9%.

[0095] Table 2 is a comparison of the PB segment 1,2-structure content, tensile strength, tearing permanent deformation and compression deformation of the examples and comparative examples. In the table, too low styrene monomer content leads to too low strength of the obtained product, while too high styrene monomer content leads to too large deformation of the obtained product.

[0096] Table 2 Permanent tearing deformation of examples and comparative examples

[0097]

[0098] It can be seen from Table 2 that compared with the comparative example, the comprehensive performance of the material prepared in the case of the present invention is excellent.

[0099] Example 4

[0100] 360g of the asymmetric star-shaped hydrogenated block copolymer prepared in Example 1 was mixed evenly with 120g of 140# polypropylene, 480g of 32# white oil, 200g of light calcium carbonate and 160g of LDPE (1C7A), added to a twin-screw extruder, extruded at high temperature using a suitable die, cooled in a cooling water tank for final shaping, and cut into corresponding finished sealing strips by a traction machine. The sealing strip is suitable for automobile window sealing strips or various industrial sealing pads.

[0101] Example 5

[0102] 360g of the asymmetric star-shaped hydrogenated block copolymer prepared in Example 1 was mixed evenly with 100g of 140# polypropylene, 480g of 32# white oil, 240g of light calcium carbonate and 80g of LDPE (1C7A), added to a twin-screw machine, extruded at high temperature using a suitable die, cooled in a cooling water tank for final shaping, and cut into corresponding finished sealing strips by a traction machine. The sealing strip is suitable for building door and window sealing strips or sealing pads.

[0103] Example 6

[0104] 300g of the asymmetric star-shaped hydrogenated block copolymer prepared in Example 1 is mixed evenly with 60g of 140# polypropylene, 600g of 32# white oil and 150g of light calcium carbonate, added into a twin-screw extruder, extruded at high temperature using a suitable die, cooled in a cooling water tank for final shaping, and cut into corresponding sealing strip products by a traction machine. The sealing strip is suitable for use as a fresh-keeping box sealing strip or other civilian sealing parts.

[0105] Example 7

[0106] Compared with Example 4, the difference is that the star-shaped hydrogenated block copolymer prepared in Example 2 is used.

[0107] Example 8

[0108] Compared with Example 4, the difference is that the star-shaped hydrogenated block copolymer prepared in Example 3 is used. Table 3 Performance of sealing strips made of the star-shaped hydrogenated block copolymer of the present invention and other fillers

[0109]

[0110] It can be seen from Table 3 that the star-shaped hydrogenated butadiene styrene block copolymer of the present invention can be used to prepare high-quality civil and industrial seals such as automobile window seals, building door and window seals, and fresh-keeping box seals according to different formulations.

Claims

1. An asymmetric star-shaped hydrogenated butadiene styrene block copolymer, characterized in that: It has the structure shown in formula I: (S1EBS2)nM Formula I S1 represents a polymer segment of styrene monomer; S2 represents a polymer chain segment of styrene and divinylbenzene monomers copolymerized; and the molecular weight of the S1 polymer chain segment is greater than that of the S2 polymer chain segment; E represents a hydrogenated 1,2-polybutadiene polymer segment; B represents a hydrogenated 1,4-polybutadiene polymer segment; M is the core of the star-shaped structure, and the core is the central atom or atom group linking the polymer arms; n represents the number of arms of the star structure, and n is not less than 2; The number average molecular weight of S1 is 6000-100000, the number average molecular weight of B is 10000-150000, and the number average molecular weight of S2 is 6000-40000; The mass ratio of S1:S2 is 9:1~1.5:1; In the S1EBS2 arm, the mass content of styrene is 15% to 50%; In the S1EBS2 arm, the mass content of divinylbenzene is 0.5% to 1.5%; The 1,2-structure content of butadiene is 10-75% of the butadiene chain segment; The degree of hydrogenation of polybutadiene chain segments is not less than 95%; M is selected from Si, Sn, C 4~ C 18 Alkyl or C 8~ C 22 Aromatic group; The coupling efficiency of the copolymer is 80-98%; The coupling degree of the copolymer is 3 to 6; The number average molecular weight of the asymmetric star-shaped hydrogenated butadiene styrene block copolymer is 100,000 to 640,000; The molecular weight distribution is 1.00~1.

20.

2. The asymmetric star-shaped hydrogenated butadiene styrene block copolymer according to claim 1, characterized in that: In the S1EBS2 arm, the mass content of styrene is 20~40%.

3. The asymmetric star-shaped hydrogenated butadiene styrene block copolymer according to claim 1, characterized in that: In the S1EBS2 arm, the mass content of styrene is 25~35%.

4. The asymmetric star-shaped hydrogenated butadiene styrene block copolymer according to claim 1, characterized in that: The 1,2-structure content of butadiene is 30~60% of the butadiene chain segment.

5. The asymmetric star-shaped hydrogenated butadiene styrene block copolymer according to claim 1, characterized in that: The coupling efficiency of the copolymer is 85-92%.

6. The asymmetric star-shaped hydrogenated butadiene styrene block copolymer according to claim 1, characterized in that: The number average molecular weight of the asymmetric star-shaped hydrogenated butadiene styrene block copolymer is 120,000 to 640,000; The molecular weight distribution is 1.01 to 1.

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7. The asymmetric star-shaped hydrogenated butadiene styrene block copolymer according to claim 1, characterized in that: The number average molecular weight of the asymmetric star-shaped hydrogenated butadiene styrene block copolymer is 160,000-350,000, and the molecular weight distribution is 1.01-1.

10.

8. A method for preparing the asymmetric star-shaped hydrogenated butadiene styrene block copolymer according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step (1): firstly add the solvent, activator and regulator into a reaction kettle, raise the temperature to a suitable temperature, add styrene monomer and initiator and initiate polymerization; Step (2): after the reaction of step (1) is complete, butadiene monomer is added for polymerization; Step (3): After the reaction of step (2) is completed, divinylbenzene and the remaining styrene monomer are mixed evenly and then added to the reactor. After the polymerization is completed, a coupling agent is added for coupling. After the coupling is completed, the rubber is pressed into a hydrogenation kettle, and a co-catalyst and a main catalyst are added to the kettle for catalytic hydrogenation. After the hydrogenation is completed, water is added to terminate the process, and an antioxidant is added to condense and dry the product.

9. The preparation method according to claim 8, characterized in that: The solvent includes: cyclohexane or n-hexane or a combination of the two, and the amount of the solvent is 70-90% of the mass concentration of the reaction system; The activator is tetrahydrofuran, and the amount used is 20-1000 mg tetrahydrofuran / kg solvent by mass content in the solvent; The regulator comprises: one or a combination of tetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, pentamethyldiethylenetriamine or furfurylamine, furfuryl ether, furfuryl alkane, and the amount of the regulator is 30-500 mg / kg solvent; The initiator is various organic lithium compounds for anionic polymerization; The coupling agent includes: silane, stannane, alkylene oxide, C 4~ C 18 Unsaturated alkanes or C 8~ C 22 Aromatic dienes; The hydrogenation main catalyst includes a Ziegler-Natta catalyst and a metallocene catalyst, and the main catalyst dosage is 0.05-3.0 mmol / 100g polymer; The hydrogenation co-catalyst includes benzoic acid esters, and the amount of the co-catalyst is 0.02-1.0 mmol / 100 g polymer.

10. The preparation method according to claim 8 or 9, characterized in that: In step (1), after adding the solvent, the temperature is controlled to be 30-100° C.; styrene monomer, activator, regulator and initiator are added and polymerization is initiated and then polymerized for 20-30 minutes; In step (2), after the styrene monomer in step (1) is completely reacted, butadiene monomer is added and the reaction temperature is controlled at 65-75° C. to polymerize for another 20-40 min; In step (3), after the butadiene monomer in step (2) is reacted, the mixed divinylbenzene and styrene monomers are added and polymerized for 20 to 40 minutes; after the polymerization is completed, a coupling agent is added and coupled for 10 to 30 minutes; the rubber is pressed into a hydrogenation kettle and hydrogen is passed; a co-catalyst and a main catalyst are added and catalytic hydrogenation is carried out for 60 to 150 minutes.

11. An application of an asymmetric star-shaped hydrogenated butadiene styrene block copolymer according to any one of claims 1 to 7, or an asymmetric star-shaped hydrogenated butadiene styrene block copolymer prepared by the preparation method according to any one of claims 8 to 10, characterized in that: Used as a seal.

12. A sealing member, characterized in that: The invention comprises an asymmetric star-shaped hydrogenated butadiene styrene block copolymer according to any one of claims 1 to 7, or an asymmetric star-shaped hydrogenated butadiene styrene block copolymer prepared by the preparation method according to any one of claims 8 to 10.

13. The seal according to claim 12, characterized in that The sealing member is at least one of a sealing strip, a sealing ring, a sealing gasket or a sealant.

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