Block copolymer with excellent vibration damping properties over a wide temperature range and method for producing the same

Abstract

This invention provides a block copolymer that exhibits excellent vibration damping properties over a wide temperature range, and a method for producing the same. [Solution] The block copolymer of the present invention consists of at least two styrene blocks and at least one styrene-myrcene copolymer block, and satisfies the following a) to c): a) the random bonding rate of the styrene-myrcene copolymer blocks is 15 to 90 mol%; b) the amount of myrcene contained in the styrene-myrcene copolymer block is 35 to 75 wt%; c) at a measurement frequency of 10 Hz, the tanδ peak temperature is in the range of -15 to 55°C and its peak value is 0.4 or higher; d) at a measurement frequency of 10 Hz, the temperature range in which tanδ is 0.4 or higher is 45°C or higher.

Description

TECHNICAL FIELD

[0001] The present invention relates to a block copolymer having excellent vibration damping properties over a wide temperature range and a method for producing the same.

BACKGROUND ART

[0002] Vibration damping refers to a phenomenon that suppresses vibration by converting the vibration energy of a solid surface into heat and attenuating the vibration. Materials used for the purpose of vibration damping are referred to as vibration damping materials, which are used in automobiles, railways, home appliances, precision equipment, housing and the like for purposes such as improving comfort and protecting equipment. Representative vibration damping materials include metals, elastomers, plastics and asphalt. Among them, elastomers are particularly widely used because they have viscoelasticity and a high vibration attenuation effect.

[0003] As a criterion for judging vibration damping properties, the value of tanδ obtained by dynamic viscoelasticity measurement is generally used as an indicator, and the higher the tanδ value, the higher the vibration attenuation effect. As described above, due to the characteristic of having viscoelasticity, elastomers are often used as vibration damping materials. Among them, block copolymers composed of styrene and isoprene produced by living anionic polymerization have a high degree of freedom in molecular design, and the tanδ peak value and peak temperature can be easily adjusted. Therefore, various such copolymers have been developed according to the target to which vibration damping properties are to be imparted.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0004]

PATENT DOCUMENT 1

PATENT DOCUMENT 2

PATENT DOCUMENT 3

PATENT DOCUMENT 4

PATENT DOCUMENT 5

[0005] For example, Patent Document 1 reports an example of a block copolymer composed of a block made of two or more aromatic vinyl compounds and a block made of one or more isoprene or isoprene-butadiene, while Patent Document 2 reports an example of a block copolymer having a block made of aromatic vinyl compounds and a block made of a mixture of isoprene and styrene. In both cases, the temperature at which vibration damping is maximized is adjusted by controlling the vinyl bond content of the constitutive conjugated diene monomers (isoprene, butadiene). However, Patent Document 1 only describes the main dispersion peak temperature of tanδ of the block copolymer, and does not mention its absorption intensity or the temperature range of its absorption intensity. Furthermore, Patent Document 2 describes the tanδ absorption intensity in the range of 30 to 70°C, but the value is 0.2 or higher, which leaves room for improvement from the perspective of achieving vibration damping.

[0006] Patent Document 3 describes obtaining a polymer block in which at least two polystyrene blocks and at least one isoprene and styrene randomly bonded together. Such a polymer has been found to have high vibration damping properties in the room temperature range (0 to 30°C) and a very wide temperature range. The monomers used in this polymer are isoprene and styrene, and the production of block copolymers using other monomers has not been investigated. In recent years, from a sustainability perspective, the importance of reducing the use of petroleum-derived monomers and switching to biomass-derived monomers has increased, and the use of myrcene produced from biomass resources available on an industrial scale is promising. Furthermore, the use of β-myrcene is being considered not only as a substitute for petroleum-derived monomers, but also to obtain polymers with unprecedented material properties. In this disclosure, β-myrcene will be simply referred to as myrcene.

[0007] For example, Patent Document 4 describes a block copolymer of an aromatic vinyl compound and myrcene, showing that it is useful as an adhesive by limiting the aromatic vinyl compound content to 50% by weight or less. Furthermore, Patent Document 5 reports a block copolymer containing up to 40% by weight of myrcene, achieving improved impact resistance and moldability while maintaining the rigidity of the resin. Such improvements in impact resistance and moldability have also been confirmed in Patent Document 6 (block polymer containing 20-70% by weight of myrcene) and Patent Document 7 (resin composition with a myrcene content of 30% or more).

[0008] However, the block copolymers disclosed in Patent Documents 4 and 5 are copolymers consisting of a styrene block - a conjugated diene block (myrcene, butadiene, or both) - a styrene block, and no study has been conducted on introducing styrene into the conjugated diene block. Furthermore, while Patent Documents 6 and 7 describe the synthesis of randomly polymerized blocks of myrcene and styrene, the random bonding properties are not discussed, and the structure is not specified. Moreover, the block copolymers obtained in Patent Documents 4 to 7 have not been evaluated for viscoelasticity, making their applicability as vibration damping materials unclear, and no block copolymers with high vibration damping properties over a wide temperature range have been obtained. [Means for solving the problem]

[0009] As a result of studies conducted by the inventors, the present invention was completed by setting the random bonding ratio within a specific range and using myrcene as the conjugated diene monomer in a block copolymer comprising a polymer block mainly composed of aromatic vinyl monomers and a polymer block in which at least one conjugated diene monomer and aromatic vinyl monomers are randomly bonded.

[0010] In other words, the present invention includes the following embodiments in order to solve the above-mentioned problems. (1) Consists of at least two aromatic vinyl monomer blocks and polymer blocks in which at least one aromatic vinyl monomer and myrcene are randomly bonded, as described in a)~ d Block copolymers that satisfy the following conditions: a) The random bonding rate of aromatic vinyl monomers in polymer blocks in which aromatic vinyl monomers are randomly bonded to myrcene is 15-90 mol%; b) The amount of myrcene contained in the aromatic vinyl monomer-myrcene copolymer block is 35-75% by weight; c) At a measurement frequency of 10 Hz, the tanδ peak temperature is in the range of -15 to 55°C, and its peak value 0.4 That's all; d) At a measurement frequency of 10 Hz, the temperature range in which tanδ is 0.4 or greater is 45°C or greater. (2) The block copolymer according to (1), wherein the myrcene content in the block copolymer is 25 to 60% by weight. (3) The block copolymer according to (1) and (2), wherein the weight-average molecular weight of the block copolymer is 100,000 to 300,000. (4) A method for producing a block copolymer comprising at least two aromatic vinyl monomer blocks and at least one aromatic vinyl monomer-myrcene copolymer block, A first step of generating a polymer block mainly composed of at least two aromatic vinyl monomers, A second step involves generating a polymer block obtained in the first step by randomly bonding at least one myrcene and an aromatic vinyl monomer to the polymer block obtained in the first step, and a third step of forming at least two polymer blocks mainly composed of aromatic vinyl monomers on the polymer block obtained in the second step, The method for producing a block copolymer according to any one of (1) to (3), wherein the polymerization is carried out in the presence of 2,2-di(tetrahydrofuryl)propane at least in the second step. (5) The method according to (4), wherein the addition amount of 2,2-di(tetrahydrofuryl)propane is 0.4 to 0.6 equivalents relative to the organolithium compound. (6) The method according to (4), wherein the polymerization temperature range is 35 to 80°C.

Effects of the Invention

[0011] According to the present invention, a block copolymer having excellent vibration damping properties in a wide temperature range can be obtained.

Brief Description of the Drawings

[0012] [Figure 1] Figure 1 is a graph showing the results of viscoelasticity measurement obtained in Examples. [Figure 2] Figure 2 is a graph showing the results of viscoelasticity measurement obtained in Comparative Examples.

Modes for Carrying Out the Invention

[0013] Hereinafter, the present invention will be described in detail. The block copolymer of the present invention comprises at least two styrene blocks and at least one styrene-myrcene copolymer block, and satisfies the following a) to d ) A block copolymer that satisfies: a) the random bonding ratio of the styrene-myrcene copolymer block is 15 to 90 mol%; b) the amount of myrcene contained in the styrene-myrcene copolymer block is 35 to 75% by weight; c) at a measurement frequency of 10 Hz, the tanδ peak temperature is in the range of -15 to 55°C and the peak value is 0.4 or more; d) at a measurement frequency of 10 Hz, the temperature range where tanδ is 0.4 or more is 45°C or more. A representative example of the present invention is represented by the following general formula. Ar1-D-Ar2 (A)

[0014] In the above general formula (A), Ar1 and Ar2 are polymer blocks mainly composed of an aromatic vinyl monomer. The number average molecular weights of the polymer blocks Ar1 and Ar2 may be the same or different from each other. Examples of the aromatic vinyl monomer include styrene, t-butylstyrene, α-methylstyrene, p-methylstyrene, o-methoxystyrene, p-methoxystyrene and the like, among which styrene is particularly preferred.

[0015] In the above general formula (A), D is a polymer block mainly composed of myrcene. Examples of the conjugated diene monomer that can be mixed into the polymer block D include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, myrcene, ocimene, farnesene, chloroprene and the like. It should be noted that by introducing an aromatic vinyl monomer into this polymer block (D) to form a conjugated diene copolymer with myrcene, the value of tan δ becomes the average value of styrene and the conjugated diene block, so that a polymer having a target tan δ can be obtained by adjusting the content ratio and randomness, the rigid terminal aromatic vinyl polymer blocks can be shortened, the hardness of the polymer can be reduced accordingly, resulting in improved processability, and the aromatic vinyl in the terminal polymer blocks (Ar1 and Ar2) and the aromatic vinyl in the conjugated diene polymer block (D) are compatible with each other during heating, which is considered to make it possible to lower the processing temperature as a result.

[0016] In the block polymer of the present invention, it is desirable that the bonding pattern of aromatic vinyl monomers in polymer block D in the above general formula (A) be random. The random bonding rate of polymer block D can be estimated by measuring 1H-NMR and using the intensity (integral value) of the peak caused by hydrogen around the aromatic ring in the units derived from aromatic vinyl monomers. In order to set the tanδ peak temperature in the range of -15 to 55°C and the temperature range of tanδ value 0.4 or higher to 45°C or higher, it is preferable to set the random bonding rate to 15 to 90 mol%, and more preferably to 18 to 90 mol%.

[0017] In the block copolymer according to this embodiment, the myrcene content in the block copolymer is 20 to 80% by weight, preferably 25 to 60% by weight, and the myrcene content in the polymer block D described above is 30 to 80% by weight, preferably 35 to 75% by weight. By controlling the myrcene content within this range, the temperature range in which tanδ is 0.4 or higher becomes 45°C or higher, and vibration damping properties can be provided over a wide temperature range. Furthermore, since the tanδ peak temperature of such a block copolymer appears within the range of -15 to 55°C, vibration damping properties can be exhibited at practical temperatures.

[0018] Furthermore, the peak value of tanδ is preferably 0.5 or higher, and more preferably 0.6 or higher, from the viewpoint of the block copolymer exhibiting sufficient vibration damping properties.

[0019] The weight-average molecular weight of the block copolymer is 100,000 to 400,000, preferably 150,000 to 300,000. If the polymerization average molecular weight is too low, the stickiness of the block copolymer will increase significantly, making industrial production difficult due to adhesion to the drying process. On the other hand, if it is too high, the viscosity of the polymerization solution is expected to become extremely high, which may cause the stirring equipment and pumps to fail due to overload. By setting the polymerization average molecular weight within the above range, a block copolymer with an excellent balance of both stickiness and viscosity can be obtained. The weight-average molecular weight is the value measured by the method described later.

[0020] The vinyl bond content (total of 1,2- and 3,4-bonds) of myrcene and conjugated diene monomers (hereinafter also simply referred to as "vinyl content") is usually 40 mol% or less, preferably 15-40 mol%, because if it is too high, crosslinking reactions of vinyl groups are more likely to occur during heating, which can reduce heat resistance. The vinyl bond content (mol%) can be estimated by measuring 1H-NMR and using the intensity (integral value) of the peaks caused by hydrogen in the units derived from the carbon chains of the conjugated diene monomer. This vinyl bond content can be adjusted by the type of polymerization initiator, polymerization temperature, and, if a randomizing agent is used, the type and amount of the randomizing agent used.

[0021] The melt flow rate of the block copolymer (150°C, 21.2N (equivalent to a 2.16 kg load)) is preferably 0.1 to 20, and more preferably 1 to 15, from the viewpoint of processability and other factors. The melt flow rate (150°C, 21.2N) is a value measured by the method described later. The molecular weight and melt flow rate of the block copolymer are adjusted by the amount of polymerization initiator added, for example, sec-butyllithium.

[0022] The polymerization method for block copolymers according to this embodiment includes a first step of generating a polymer block (Ar1) mainly composed of at least two aromatic vinyl monomers; a second step of generating a polymer block (D) obtained by randomly bonding at least one myrcene and an aromatic vinyl monomer to the polymer block obtained in the first step; and a third step of generating a polymer block (Ar2) mainly composed of at least two aromatic vinyl monomers to the polymer block obtained in the second step.

[0023] Furthermore, while the polymerization method is not particularly limited, including continuous and coupling methods, polymers polymerized by the coupling method may contain a certain amount of diblock copolymer, unreacted coupling agent, and impurities associated with the coupling reaction. Since these components can cause a decrease in the strength and degradation of the block copolymer, a continuous polymerization method is preferred. In addition, the random bonding of myrcene and aromatic vinyl monomers in polymer block D can be adjusted by the timing of the addition of each monomer, but from the viewpoint of improving reaction efficiency and shortening the reaction time, it is preferable to add a randomizing agent to the polymerization system. Generally, the reaction rate of conjugated diene monomers is higher than that of aromatic vinyl monomers. Therefore, as a randomizing agent, one that acts to increase the reaction rate of aromatic vinyl monomers can be used. For example, ethers such as tetrahydrofuran, tetrahydropyran, 1,2-dimethoxyethane, 1,2-diethoxyethane, 2,2-di(tetrahydrofuryl)propane, and 18-crown-6, as well as amines such as triethylamine, N,N-dimethylaniline, and N,N,N',N'-tetramethylethylenediamine can be used. Among these, 2,2-di(tetrahydrofuryl)propane is preferred for stable control of the randomization rate.

[0024] Furthermore, while the polymerization reaction by the continuous method is carried out in a single pot, the randomizing agent may be added during the initial styrene block polymerization or during the second step of polymerization to produce the myrcene / aromatic vinyl monomer polymer block (D).

[0025] These can be used individually or in combination of two or more. By using a randomizing agent, it is possible to suppress the preferential reaction between conjugated diene monomers, and as a result, the randomization of the reactions between conjugated diene monomers and aromatic vinyl monomers is promoted.

[0026] The amount of randomizing agent added is preferably 0.4 to 0.6 equivalents relative to the organolithium compound, but it can be arbitrarily adjusted to control the structure of polymer block D. For example, if it is necessary to broaden the temperature range in which the tanδ value is 0.4 or higher, this can be achieved by increasing the amount of randomizing agent within the above range.

[0027] Examples of polymerization solvents include aliphatic hydrocarbons such as n-pentane, isopentane, n-hexane, isohexane, heptane, octane, methylcyclopentane, cyclohexane, and methylcyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene; ethers such as diethyl ether, 1,4-dioxane, tetrahydrofuran, tetrahydropyran, and 2-methyltetrahydrofuran; and tertiary amines such as triethylamine and tri(n-propyl)amine. However, from the viewpoint of suppressing and adjusting the vinyl content of the conjugated diene monomer, it is preferable to select aliphatic and aromatic hydrocarbons as polymerization solvents. These solvents may be used individually or in mixtures of two or more types.

[0028] Examples of the above-mentioned organoalkali metal compounds used as polymerization initiators include organolithium compounds, organosodium compounds, and organocatum compounds, with organolithium compounds being particularly preferred. Specific examples of organolithium compounds include methyllithium, ethyllithium, n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, and tert-butyllithium.

[0029] Polymerization reactions are preferably carried out within a predetermined temperature range because the reaction rates of both monomers and the 1,4- / 3,4- / 1,2-bond content of myrcene, a conjugated diene monomer, vary with temperature. Furthermore, if the temperature is too low, the polymerization time becomes very long, while if it is too high, it becomes difficult to control the reaction and side reactions such as crosslinking due to reactions with double bonds in the polymer block containing the conjugated diene are more likely to occur. Therefore, the reaction is usually carried out at 30 to 100°C, preferably 35 to 80°C. Polymerization may be carried out under controlled constant temperature, or it may be carried out at an increasing temperature without heat removal.

[0030] Furthermore, polymerization inhibitors may be used to complete the polymerization reaction. Examples of such polymerization inhibitors include alcohols and water, such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol.

[0031] The resulting polymerization solution can be desolvented using known methods such as steam stripping to obtain a block copolymer. Additives such as antioxidants may be added to the block copolymer as needed.

[0032] The block copolymer of the present invention can be hydrogenated as needed, with hydrogenation added to the remaining unsaturated bonds of the conjugated diene monomer of polymer block D. There are no particular restrictions on the hydrogenation method or reaction conditions, and the hydrogenation is carried out under hydrogen pressure and in the presence of a hydrogenation catalyst. The hydrogenation rate can be appropriately adjusted by changing the amount of hydrogenation catalyst, the hydrogen pressure during the hydrogenation reaction, the reaction time, etc. There are no restrictions on the type of hydrogenation catalyst used in the hydrogenation reaction, and any or a mixture of commonly known heterogeneous or homogeneous catalysts can be used.

[0033] The block copolymer of the present invention can be used alone as a molded article, but it can also be blended with other polymers and used as a composition. Other polymers that can be blended include thermoplastic resins such as polystyrene, polyphenylene oxide, polypropylene, ethylene-vinyl acetate copolymer, polyamide, polyester, and polylactic acid, or elastomers such as natural rubber, isoprene rubber, butyl rubber, SBR, EPDM, and isoprene-butadiene copolymer, which can be used to improve their properties.

[0034] The block copolymer of the present invention may contain compounding agents commonly used in rubber formulations, such as plasticizers and softeners like oil, reinforcing agents like carbon black and silica, and fillers like calcium carbonate, talc, and mica. [Examples]

[0035] The embodiments of this application will be described in more detail by the examples and comparative examples described below.

[0036] The block copolymers obtained in the following examples and comparative examples were analyzed using the following methods. The various physical properties of the obtained block copolymer were measured as follows. (1) Weight average molecular weight (Mw) For weight-average molecular weight measurement, a gel permeation chromatography system (HLC-8320) manufactured by Tosoh Corporation was used, with a Waters Ultrabondagel E750A column. Tetrahydrofuran was used as the solvent, and the measurement conditions were 45°C, 1.0 mL / min flow rate, 0.1% sample concentration, and 20 μL injection volume. The values ​​were converted to standard polystyrene. (2) Microstructure of block copolymer (by weight or molar %) ¹H-NMR (Bruker AVANCE III HD500) was measured using 1,1,2,2-tetrachloroethane-d2 as the solvent. The obtained integral values ​​were converted to values ​​per hydrogen atom in each structure, and then the styrene content (wt%), vinyl bond content (vinyl content (mol%)), and random bond rate of bonded styrene (mol%) were calculated. Below, the relationship between the chemical shift of interest (TMS standard: δ=0), the assignment of hydrogen to each chemical shift, and the structure in which that hydrogen is involved is shown. In the calculation formulas for each value, all hydrogens are treated as having the same intensity (integral value), and A to D indicate the intensity (integral value) at each chemical shift, respectively. In addition, the molecular weight of styrene was set to 104, the molecular weight of isoprene to 68, and the molecular weight of myrcene to 136 during the calculation. It is known that the peak of 1,2-polymyrcene appears around 5.6 to 5.8 ppm, but this peak was not detected in the block copolymer obtained in the examples. Therefore, calculations for polymers containing polymyrcene are performed excluding the parts related to 1,2-bonds.

[0037] [Table 1]

[0038] Value per hydrogen atom in each structure • 1,4-Polymyrcene: (BA / 2) / 2 • 3,4-Polymyrcene: A / 2 • Block styrene (BS): C / 2 Random Styrene (RS): Total hydrogen intensity around the aromatic ring of random styrene ÷ 5 =[(Intensity of all hydrogen around the aromatic ring of styrene other than the ortho position of block styrene)-(Intensity of hydrogen around the aromatic ring of block styrene other than the ortho position)]÷5 =[D-3×BS]÷5 =[D-3×C / 2] / 5

[0039] • 1,4-Polymyrcene content (mol%): [1,4-Myrcene / Total Myrcene] × 100 =[{(BA / 2) / 2} / [{(BA / 2) / 2}+A / 2]]×100 • Vinyl bond content = 3,4-polymyrcene content (mol%): [1-1,4-myrcene] × 100 Styrene content (weight %): {(BS+RS)×10⁴} / {(BS+RS)×10⁴+Total myrcene×13⁶}×100 • Random binding ratio (mol%): [RS / (BS+RS)] × 100

[0040] [Table 2]

[0041] Value per hydrogen atom in each structure · 1,4-Polyisoprene: B-2C 3,4-Isoprene:A / 2 • 1,2-Isoprene:C • Block styrene (BS): D / 2 Random Styrene (RS): Total hydrogen intensity around the aromatic ring of random styrene ÷ 5 =[(Intensity of all hydrogen around the aromatic ring of styrene other than the ortho position of block styrene)-(Intensity of hydrogen around the aromatic ring of block styrene other than the ortho position)]÷5 =[E-3×BS]÷5 =[E-3×D / 2] / 5

[0042] (3) Dynamic viscoelasticity measurement of block copolymers Measurements were taken using a UBM viscoelasticity analyzer (Rheogel E-4000) under conditions of a frequency of 10 Hz and a heating rate of 5°C / min. (4) Meltflow rate [MFR] (g / 10 min) Measurements were performed using an Automelt Indexer (TP-404 model) manufactured by Tester Sangyo Co., Ltd., in accordance with JIS K7210. For block copolymers containing myrcene, measurements were performed under conditions of 150°C and 21.2N, and for block copolymers containing isoprene, measurements were performed under conditions of 190°C and 21.2N.

[0043] (Example 1) Polymerization of block copolymer 1 650 mL of cyclohexane was placed in a thoroughly dried 1 L glass container and heated in an oil bath to bring the reaction system to 40°C. Next, 0.63 mL of a 10% by weight sec-butyllithium cyclohexane solution and 0.93 mL of a 10% by weight 2,2-di-(2-tetrahydrofuryl)propane solution were added and stirred for 1 minute. Then, 10 g of styrene was added to initiate polymerization. After 30 minutes of reaction, a mixed solution of 50 g of myrcene and 30 g of styrene was added and the mixture was reacted for 60 minutes. Subsequently, another 10 g of styrene was added and the mixture was reacted for 30 minutes. After the reaction was complete, methanol was added to stop the reaction and obtain block copolymer 1. The myrcene used was a commercially available product that was treated with activated alumina to remove antioxidants and then purified to a purity of 86.5% or higher. The amount of myrcene added was set assuming that the purified myrcene was 100% pure. No difference in the reaction behavior of myrcene was observed in the purity range of 86.5% or higher.

[0044] (Example 2) Polymerization of block copolymer 2 Block copolymer 2 was obtained by following the same procedure as in Example 1, except that the amount of 10% by weight of 2,2-di-(2-tetrahydrofuryl)propane added was changed to 1.02 mL.

[0045] (Example 3) Polymerization of block copolymer 3 Block copolymer 3 was obtained by following the same procedure as in Example 1, except that the amounts of myrcene and styrene added in the second polymerization step were changed to 60g and 20g, respectively.

[0046] (Example 4) Polymerization of block copolymer 4 Block copolymer 4 was obtained by following the same procedure as in Example 1, except that the amount of myrcene / styrene added in the second polymerization step was changed to 40g / 40g, respectively.

[0047] (Example 5) Polymerization of block copolymer 5 Block copolymer 4 was obtained by following the same procedure as in Example 1, except that the amounts of myrcene and styrene added in the second polymerization step were changed to 30g and 50g, respectively.

[0048] (Comparative Example 1) Polymerization of block copolymer 6 After thoroughly purging a 5L stainless steel polymerization vessel equipped with a jacket and stirrer with nitrogen, 3.3L of cyclohexane was added, and the reaction system was brought to 55°C by passing warm water through the jacket. Next, 3.0 mL of 10% by weight sec-butyllithium cyclohexane solution and 2.6 mL of 10% by weight 2,2-di-(2-tetrahydrofuryl)propane were added and stirred for 1 minute, then 50 g of styrene was added to start polymerization. After 30 minutes of reaction, 250 g of isoprene and 150 g of styrene were added in two equal parts and reacted for a total of 60 minutes. Subsequently, another 50 g of styrene was added and reacted for 30 minutes. After the reaction was complete, methanol was added to stop the reaction and block copolymer 6 was obtained.

[0049] (Comparative Example 2) Polymerization of block copolymer 7 Block copolymer 7 was obtained by following the same procedure as in Comparative Example 1, except that the amount of sec-butyllithium cyclohexane solution added was changed to 2.7 mL and 10% by weight of 2,2-di-(2-tetrahydrofuryl)propane was changed to 3.1 mL, and the amounts of isoprene / styrene added were changed to 240 g / 160 g, respectively.

[0050] (Comparative Example 3) Polymerization of block copolymer 8 Block copolymer 8 was obtained by following the same procedure as in Comparative Example 1, except that the amount of sec-butyllithium cyclohexane solution added was changed to 2.7 mL and 10% by weight of 2,2-di-(2-tetrahydrofuryl)propane was changed to 3.9 mL.

[0051] (Comparative Example 4) Polymerization of block copolymer 9 Block copolymer 9 was obtained by following the same procedure as in Comparative Example 1, except that the amount of sec-butyllithium cyclohexane solution added was changed to 2.2 mL and 10% by weight of 2,2-di-(2-tetrahydrofuryl)propane was changed to 3.9 mL, and the amounts of isoprene / styrene added were changed to 225 g / 175 g, respectively.

[0052] (Comparative Example 5) Polymerization of block copolymer 10 Block copolymer 10 was obtained by following the same procedure as in Comparative Example 1, except that the amount of sec-butyllithium cyclohexane solution added was changed to 2.5 mL and 10% by weight of 2,2-di-(2-tetrahydrofuryl)propane was changed to 3.0 mL.

[0053] Table 3 shows the physical properties of the block copolymer obtained by the method of the example, and Table 4 shows the physical properties of the block copolymer obtained by the method of the comparative example.

[0054] [Table 3]

[0055] [Table 4]

[0056] Table 3 shows that all block copolymers obtained in the examples have a tanδ peak temperature in the range of -15 to 55°C and a temperature range of 45°C or more where the tanδ is 0.4 or higher, indicating that they maintain their vibration damping properties even when the peak temperature fluctuates somewhat. Furthermore, since the tanδ peak value is 0.6 or higher, they are suitable as vibration damping materials.

[0057] On the other hand, the block copolymer obtained according to the comparative example, as shown in Table 4, has a tanδ peak value of 0.54 or higher, and is considered applicable as a vibration damping material. However, since the temperature range in which tanδ is 0.4 or higher is narrower than that of the examples, the range of application as a vibration damping material is narrower, thus limiting its uses.

[0058] Figure 1 shows the viscoelasticity measurement results of the block copolymer obtained in the example, and Figure 2 shows the viscoelasticity measurement results of the block copolymer obtained in the comparative example. Comparing Figure 1 and Figure 2, the temperature range in which tanδ is 0.4 or higher is wider for the example (Figure 1) than for the comparative example (Figure 2), suggesting a wider range of application as a vibration damping material.

Claims

1. A block copolymer consisting of at least two styrene blocks and at least one styrene-myrcene copolymer block, satisfying the following a) to d): a) The random bonding rate of the styrene-myrcene copolymer block is 15-90 mol%; b) The amount of myrcene contained in the styrene-myrcene copolymer block is 35 to 75% by weight; c) At a measurement frequency of 10 Hz, the tanδ peak temperature is in the range of -15 to 55°C and its peak value is 0.4 or greater; d) At a measurement frequency of 10 Hz, the temperature range in which tanδ is 0.4 or greater is 45°C or greater.

2. The block copolymer according to claim 1, wherein the myrcene content in the block copolymer is 25 to 60% by weight.

3. The block copolymer according to claim 1, wherein the weight-average molecular weight of the block copolymer is 100,000 to 300,000.

4. A method for producing a block copolymer comprising at least two styrene blocks and at least one styrene-myrcene copolymer block, A first step of generating a polymer block mainly composed of at least two aromatic vinyl monomers, A second step involves generating a polymer block obtained in the first step by randomly bonding at least one myrcene and an aromatic vinyl monomer to the polymer block obtained in the first step, and The process includes a third step of generating a polymer block mainly composed of at least two aromatic vinyl monomers from the polymer block obtained in the second step, A method for producing a block copolymer according to any one of claims 1 to 3, wherein polymerization is carried out in the presence of 2,2-di(tetrahydrofuryl)propane in at least the second step.

5. The method according to claim 4, wherein the amount of 2,2-di(tetrahydrofuryl)propane added is 0.4 to 0.6 equivalents relative to the organolithium compound.

6. The method according to claim 4, wherein the polymerization temperature range is 35 to 80°C.

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