Modified liquid diene polymers and rubber compositions

Abstract

To provide a diene polymer excellent in silica adsorption and a rubber composition containing the diene polymer.SOLUTION: A modified liquid diene polymer has a structure derived from a compound represented by formula (1) at a terminal and has a weight average molecular weight of 500-50,000. In the formula (1), X represents a C1-12 alkylene group, a C2-12 alkenylene group or a C6-12 aromatic group; and A1, A2, A3, Y and Z each independently represent an alkyl group, an alkoxy group or a hydroxyl group.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a modified liquid diene polymer and a rubber composition.

Background Art

[0002] Conventionally, a diene polymer that improves its dispersibility by interacting with silica or the like has been proposed (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Under such circumstances, when the inventors of the present invention examined the diene polymer described in Patent Document 1, it became clear that further improvement in silica adsorption is desirable in view of applications to various uses.

[0005] Therefore, in view of the above circumstances, an object of the present invention is to provide a diene polymer excellent in silica adsorption and a rubber composition containing the above diene polymer.

Means for Solving the Problems

[0006] As a result of intensive studies on the above problems, the inventors of the present invention have found that the above problems can be solved by a modified liquid diene polymer having a structure derived from a specific compound having a silicon atom and a phosphorus atom at its terminal and having a weight average molecular weight of 500 to 50,000, and have arrived at the present invention. That is, the inventors of the present invention have found that the above problems can be solved by the following constitution.

[0007] (1) A modified liquid diene polymer having a structure at its terminal end derived from the compound represented by formula (1) described later, and having a weight-average molecular weight of 500 to 50,000. (2) The modified liquid diene polymer described in (1) above, having a viscosity of 2,000 Pa·s or more. (3) The modified liquid diene polymer according to (1) or (2) above, wherein the diene constituting the modified liquid diene polymer is 1,3-butadiene or isoprene. (4) The modified liquid diene polymer according to any one of (1) to (3) above, wherein the monomer constituting the modified liquid diene polymer includes aromatic vinyl as a monomer other than diene. (5) A rubber composition containing 100 parts by mass of rubber, 5 to 200 parts by mass of silica, and 1 to 50 parts by mass of a modified liquid diene polymer as described in any of (1) to (4) above. [Effects of the Invention]

[0008] As shown below, the present invention provides a diene polymer with excellent silica adsorption properties and a rubber composition containing the above diene polymer. [Brief explanation of the drawing]

[0009] [Figure 1] This is the 31P NMR (nuclear magnetic resonance) spectrum of specific modified polymer 1. [Figure 2] This is the 1H NMR spectrum of specific modified polymer 1. [Modes for carrying out the invention]

[0010] The modified liquid diene polymer of the present invention will be described below. In this specification, a numerical range represented by "~" means a range that includes the numbers written before and after "~" as the lower and upper limits, respectively. Furthermore, in this specification, each component may be used alone or in combination of two or more. Here, when two or more components are used in combination, the quantity of each component refers to the total quantity unless otherwise specified. Furthermore, in this specification, hydrocarbon groups (alkyl groups, alkylene groups, alkyl groups in alkoxy groups, etc.) may have heteroatoms, and their shape (linear, branched, cyclic) is not particularly limited. Furthermore, in this specification, the term "excellent effects of the present invention" also refers to the excellent silica adsorption properties, as well as the excellent silica dispersibility, low heat generation, abrasion resistance, wet performance, ice performance, and mechanical properties when used in rubber compositions.

[0011] [1] Specific Modified Polymers The modified liquid diene polymer of the present invention (hereinafter also referred to as "specific modified polymer") is This is a modified liquid diene polymer having a structure at its terminal end derived from the compound represented by formula (1) described later, and having a weight-average molecular weight of 500 to 50,000.

[0012] It is believed that the desired effect is obtained because the specific modified polymer adopts this structure. Although the reason is not clear, it is speculated that the phosphine oxide acts as a catalyst for the reaction between the silyl group and the silanol group of silica, resulting in extremely excellent adsorption to silica.

[0013] [Body structure] The backbone (main chain structure) of the specific modified polymer is not particularly limited as long as it is a diene polymer. A diene polymer is a polymer of monomers containing a diene. A diene polymer may be a homopolymer or a copolymer, but a homopolymer is preferred because it provides superior effects in the present invention.

[0014] [Jien] Specific examples of the above diene include butadiene (especially 1,3-butadiene), isoprene, chloroprene, and the like. From the reason that the effects of the present invention are more excellent, the above diene is preferably butadiene (especially 1,3-butadiene) or isoprene, and more preferably butadiene (especially 1,3-butadiene).

[0015] 〔Monomers other than diene〕 The monomer containing the above diene may contain monomers other than the diene. The monomers other than the above diene are not particularly limited, and examples include aromatic vinyl (preferably styrene), acrylonitrile, ethylene, propylene, butene (preferably isobutylene), and the like. From the reason that the effects of the present invention are more excellent, the monomers other than the above diene are preferably aromatic vinyl, and more preferably styrene.

[0016] 〔Content〕 The content of the diene in all the monomers constituting the above diene-based polymer is not particularly limited, but from the reason that the effects of the present invention are more excellent, it is preferably 10% by mass or more, more preferably 50% by mass or more, and further preferably 90% by mass or more. The content of the diene in all the monomers is not particularly limited and is 100% by mass.

[0017] When the monomer containing the above diene contains aromatic vinyl as a monomer other than the diene, the content of the diene in all the monomers constituting the above diene-based polymer is preferably 10 to 99% by mass, more preferably 30 to 95% by mass, further preferably 50 to 90% by mass, and particularly preferably 60 to 80% by mass from the reason that the effects of the present invention are more excellent. Furthermore, if the monomer containing the diene also contains aromatic vinyl as a monomer other than the diene, the content of aromatic vinyl in the total monomer constituting the diene polymer is preferably 1 to 90% by mass, more preferably 5 to 70% by mass, even more preferably 10 to 50% by mass, and particularly preferably 20 to 40% by mass, for reasons that the effects of the present invention are superior.

[0018] [Specific examples] Specific examples of the above-mentioned diene polymers include butadiene polymer (BR), isoprene polymer (IR), chloroprene polymer (CR), isoprene-butadiene copolymer (IBR), butadiene-styrene copolymer (SBR), acrylonitrile-butadiene copolymer (NBR), isobutylene-isoprene copolymer, and the like. Among these, BR, IR, and SBR are preferred, BR and SBR are more preferred, and BR is even more preferred, due to the superior effects of the present invention.

[0019] [Preferred Embodiment] The diene constituting the above-mentioned diene polymer is preferably 1,3-butadiene or isoprene, and more preferably 1,3-butadiene, for the reasons that the effects of the present invention are superior.

[0020] [End] As described above, the specific modified polymer has a structure at its terminal that originates from the compound represented by the following formula (1). Typically, the specific modified polymer has a structure in which one of A1, A2, A3, Y, and Z in formula (1) is replaced by a diene polymer in the backbone. The specific modified polymer may have a structure derived from the compound represented by formula (1) at only one end, or at multiple ends.

[0021] [Compound represented by formula (1)]

[0022] [ka]

[0023] In formula (1), X represents an alkylene group having 1 to 12 carbon atoms, an alkenylene group having 2 to 12 carbon atoms, or an aromatic group having 6 to 12 carbon atoms, and A1, A2, A3, Y, and Z each independently represent an alkyl group, an alkoxy group, or a hydroxyl group.

[0024] <x> As described above, in formula (1), X represents an alkylene group having 1 to 12 carbon atoms, an alkenylene group having 2 to 12 carbon atoms, or an aromatic group having 6 to 12 carbon atoms. X is preferably an alkylene group having 1 to 12 carbon atoms because it provides superior effects of the present invention.

[0025] <A1、A2、A3> As described above, in formula (1), A1, A2, and A3 each independently represent an alkyl group (particularly having 1 to 12 carbon atoms), an alkoxy group (particularly having 1 to 12 carbon atoms), or a hydroxyl group. A1, A2, and A3 are preferably alkoxy groups for the reasons that the effects of the present invention are superior. At least one of A1, A2, and A3 is preferably an alkoxy group for the reasons that the effects of the present invention are superior.

[0026] <Y、Z> As described above, in formula (1), Y and Z each independently represent an alkyl group (particularly having 1 to 12 carbon atoms), an alkoxy group (particularly having 1 to 12 carbon atoms), or a hydroxyl group. Y and Z are preferably alkoxy groups for the reasons that the effects of the present invention are superior. At least one of Y and Z is preferably an alkoxy group for the reasons that the effects of the present invention are superior.

[0027] [Molecular weight] As described above, the weight-average molecular weight (Mw) of the specific modified polymer is 500 to 50,000. The above Mw is preferably 1,000 to 30,000, and more preferably 10,000 to 20,000, for reasons that the effects of the present invention are superior.

[0028] Furthermore, the number-average molecular weight (Mn) of the specific modified polymer is preferably 500 to 50,000, more preferably 1,000 to 30,000, and even more preferably 10,000 to 20,000, for reasons that the effects of the present invention are superior.

[0029] In this specification, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) are standard polystyrene equivalent values ​​obtained by gel permeation chromatography (GPC) measurement under the following conditions. • Solvent: tetrahydrofuran • Detector: RI detector

[0030] [viscosity] The viscosity of the specific modified polymer is preferably 2,000 Pa·s or higher for reasons that the effects of the present invention are superior. The upper limit of the viscosity is not particularly limited, but it is preferably 100,000 Pa·s or less, and more preferably 10,000 Pa·s or less, for reasons that the effects of the present invention are superior.

[0031] In this specification, viscosity shall be measured using a cone-plate viscometer under conditions of 40°C, in accordance with JIS K5600-2-3.

[0032] [Degeneration rate] The modification rate of the specific modified polymer is not particularly limited, but for reasons that the effects of the present invention are superior, it is preferably 0.01 to 10 mol%, more preferably 0.1 to 5.0 mol%, even more preferably 1.0 to 4.0 mol%, and particularly preferably 2.0 to 3.0 mol%. The above denaturation rate represents the proportion (mol%) of the structure derived from the compound represented by formula (1) relative to the total number of repeating units.

[0033] [Manufacturing method] The method for producing the specific modified polymer is not particularly limited, but a method comprising the following polymerization step and the following end modification step is preferred because the effects of the present invention are superior in the obtained specific modified polymer. Hereafter, the superior effects of the present invention in the obtained specific modified polymer will also simply be referred to as "superior effects of the present invention." (1) Polymerization process A process to obtain a diene-based polymer having an active end by polymerizing a diene-containing monomer by anionic polymerization. (2) Terminal degeneration process A process to obtain a modified liquid diene polymer (specific modified polymer) having a structure derived from the compound represented by formula (1) at its terminus and a weight-average molecular weight of 500 to 50,000, by reacting the diene polymer having active terminus obtained in the above polymerization step with the compound represented by formula (1).

[0034] The following details each step.

[0035] [Polymerization process] The polymerization process involves polymerizing a diene-containing monomer by anionic polymerization to obtain a diene-based polymer having an active end (anionic species).

[0036] <Monomer> Specific examples and preferred embodiments of diene-containing monomers used in the polymerization process are the same as the skeleton of the specific modified polymer described above.

[0037] <Anionic polymerization> Anionic polymerization is not particularly limited, but it is preferable to use anionic polymerization using an organolithium compound because it offers superior effects compared to the present invention.

[0038] (Organolithium compounds) The organolithium compounds are not particularly limited, but specific examples include monoorganolithium compounds such as n-butyllithium (n-BuLi), sec-butyllithium, tert-butyllithium, n-propyllithium, iso-propyllithium, and benzyllithium; and polyfunctional organolithium compounds such as 1,4-dilithiobutane, 1,5-dilithiopentane, 1,6-dilithiohexane, 1,10-dilithiodecane, 1,1-dilithiodiphenylene, dilithiopolybutadiene, dilithiopolyisoprene, 1,4-dilithiobenzene, 1,2-dilithio-1,2-diphenylethane, 1,4-dilithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene, and 1,3,5-trilithio-2,4,6-triethylbenzene. Among these, monoorganolithium compounds of n-butyllithium, sec-butyllithium, and tert-butyllithium are preferred, and n-butyllithium is more preferred, for reasons that the effects of the present invention are superior.

[0039] The amount of organolithium compound used is not particularly limited, but it is preferably 0.001 to 10 mol% relative to the monomer, for reasons that the effects of the present invention are superior.

[0040] <Diene polymers with active ends> The preferred range for the diene polymer having active ends obtained in the polymerization process is the same as that for the specific modified polymer skeleton described above. Furthermore, the preferred ranges for the molecular weight and viscosity of the diene polymer having active ends are the same as those for the specific modified polymer described above.

[0041] [End-level modification process] The end-modification step involves reacting the diene polymer having active ends obtained in the polymerization step described above with a compound represented by formula (1) to obtain a modified liquid diene polymer (specific modified polymer) having a structure derived from the compound represented by formula (1) at its ends and a weight-average molecular weight of 500 to 50,000. Since the compound represented by formula (1) is electrophilic, it acts as an inhibitor (electrophile) of the diene polymer having active ends.

[0042] <Compound represented by formula (1)> The compound represented by formula (1) is as described above.

[0043] [Application] Specific modified polymers are useful in silica-containing compositions (especially rubber compositions (for tires, conveyor belts, hoses, etc., especially for tires)).

[0044] [2] Rubber composition The rubber composition of the present invention (hereinafter also referred to as "the composition of the present invention") is This rubber composition contains 100 parts by mass of rubber, 5 to 200 parts by mass of silica, and 1 to 50 parts by mass of the above-mentioned modified liquid diene polymer (specific modified polymer).

[0045] [rubber] As described above, the composition of the present invention contains rubber. The above-mentioned rubber is not particularly limited. However, the above-mentioned rubber does not include the specified modified polymers mentioned above.

[0046] The rubber mentioned above is preferably a diene-based rubber because it provides superior effects and other benefits of the present invention. Specific examples of the above-mentioned diene rubbers include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), and chloroprene rubber (CR). The above-mentioned rubber is preferably natural rubber, isoprene rubber, butadiene rubber, or styrene-butadiene rubber, for reasons that it provides superior effects of the present invention.

[0047] [Molecular weight]

[0048] <Weight average molecular weight> The weight-average molecular weight (Mw) of the above rubber is not particularly limited, but for reasons that the effects of the present invention are superior, it is preferably greater than 50,000, more preferably between 100,000 and 10,000,000, and even more preferably between 200,000 and 2,000,000.

[0049] <Number average molecular weight> The number-average molecular weight (Mn) of the above-mentioned rubber is not particularly limited, but it is preferably 50,000 to 5,000,000, and more preferably 100,000 to 1,000,000, for reasons that the effects of the present invention are superior.

[0050] [silica] As described above, the composition of the present invention contains silica. The silica mentioned above is not particularly limited, and any conventionally known silica can be used. Examples of the above-mentioned silica include wet silica, dry silica, fumed silica, and diatomaceous earth. The above-mentioned silica may be used alone or in combination of two or more types of silica.

[0051] [CTAB] The specific surface area of ​​the above silica for adsorption of cetyltrimethylammonium bromide (CTAB) (hereinafter, "CTAB adsorption specific surface area" will also be simply referred to as "CTAB") is not particularly limited, but for reasons that the effects of the present invention are superior, 100 to 300 m is preferred. 2 It is preferable that the amount be / g, and 150-200m 2 It is more preferable that it be / g. Here, the CTAB adsorption specific surface area is the value obtained by measuring the amount of CTAB adsorbed onto the silica surface according to JIS K6217-3:2001 "Part 3: Method for determining specific surface area - CTAB adsorption method".

[0052] [Content] In the composition of the present invention, the silica content is 5 to 200 parts by mass per 100 parts by mass of the rubber described above. The silica content is preferably 10 to 150 parts by mass, and more preferably 30 to 100 parts by mass, per 100 parts by mass of the rubber described above, for reasons that the effects of the present invention are superior.

[0053] [Specific Modified Polymers] As described above, the composition of the present invention contains the modified liquid diene polymer (specific modified polymer) described above. The specific modified polymer is as described above. In the composition of the present invention, the specific modified polymer is considered to act as a silica dispersant.

[0054] [Content] In the composition of the present invention, the content of the specific modified polymer is 1 to 50 parts by mass per 100 parts by mass of the rubber described above. Preferably, the content of the specific modified polymer is 2 to 10 parts by mass per 100 parts by mass of the rubber described above, for reasons that the effects of the present invention are superior.

[0055] In the composition of the present invention, the content of the specific modified polymer is preferably 1 to 20% by mass, and more preferably 5 to 15% by mass, relative to the silica content, for reasons that the effects of the present invention are superior.

[0056] [Optional ingredients] The composition of the present invention may optionally contain components other than those described above (optional components). Examples of such components include fillers other than silica (preferably carbon black), silane coupling agents, terpene resins (preferably aromatically modified terpene resins), thermally expandable microcapsules, zinc oxide, stearic acid, antioxidants, waxes, processing aids, process oils, liquid polymers, thermosetting resins, vulcanizing agents (e.g., sulfur), vulcanization accelerators, vulcanization activators, and various other additives commonly used in rubber compositions.

[0057] [Silane coupling agent] The composition of the present invention preferably contains a silane coupling agent because it provides superior effects and other benefits.

[0058] The silane coupling agent is not particularly limited as long as it is a silane compound having a hydrolyzable group and an organic functional group. The above hydrolyzable group is not particularly limited, but examples include alkoxy groups, phenoxy groups, carboxyl groups, and alkenyloxy groups. Among these, an alkoxy group is preferred for the reasons that the effects of the present invention are superior. When the hydrolyzable group is an alkoxy group, the number of carbon atoms in the alkoxy group is preferably 1 to 16, and more preferably 1 to 4, for the reasons that the effects of the present invention are superior. Examples of alkoxy groups with 1 to 4 carbon atoms include methoxy groups, ethoxy groups, and propoxy groups.

[0059] The above organic functional groups are not particularly limited, but are preferably groups that can form chemical bonds with organic compounds. Examples include epoxy groups, vinyl groups, acryloyl groups, methacryloyl groups, amino groups, sulfide groups, mercapto groups, and blocked mercapto groups (protected mercapto groups) (e.g., octanoylthio groups). Among these, sulfide groups (especially disulfide groups and tetrasulfide groups), mercapto groups, and blocked mercapto groups are preferred because they offer superior effects compared to the present invention. Silane coupling agents may be used individually or in combination of two or more types.

[0060] The silane coupling agent described above is preferably a sulfur-containing silane coupling agent because it provides superior effects and other benefits of the present invention.

[0061] Specific examples of the silane coupling agents mentioned above include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazoletetrasulfide, triethoxysilylpropyl-methacrylate-monosulfide, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl-tetrasulfide, and 3-octanoylthio-1-propyltriethoxysilane. One of these may be used alone, or two or more may be used in combination.

[0062] <Content> In the composition of the present invention, the content of the silane coupling agent is not particularly limited, but for reasons that the effects of the present invention are superior, it is preferably 1 to 20 parts by mass, and more preferably 2 to 10 parts by mass, per 100 parts by mass of the rubber mentioned above.

[0063] Furthermore, in the composition of the present invention, the content of the silane coupling agent is preferably 1 to 20% by mass, and more preferably 5 to 15% by mass, relative to the silica content, for reasons that the effects of the present invention are superior.

[0064] [Carbon Black] The composition of the present invention preferably contains carbon black for reasons that the effects of the present invention are superior. The carbon black may be one type of carbon black used alone, or two or more types of carbon black may be used in combination. The carbon black mentioned above is not particularly limited, and various grades such as SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, FEF, GPF, and SRF can be used.

[0065] <n2sa> The nitrogen adsorption specific surface area (N2SA) of the carbon black described above is not particularly limited, but for reasons that the effects of the present invention are superior, it is 50 to 200 m². 2 It is preferable that the value be / g, and 70-150m 2 It is more preferable that it be / g. Here, the nitrogen adsorption specific surface area (N2SA) is the value obtained by measuring the amount of nitrogen adsorbed onto the carbon black surface according to JIS K6217-2:2001 "Part 2: Method for determining specific surface area - Nitrogen adsorption method - Single point method".

[0066] In the composition of the present invention, the carbon black content is not particularly limited, but for reasons that the effects of the present invention are superior, it is preferably 1 to 100 parts by mass, and more preferably 2 to 10 parts by mass, per 100 parts by mass of the rubber described above.

[0067] [Application] The compositions of the present invention are suitably used in, for example, tires, conveyor belts, hoses, vibration damping materials, rubber rolls, and railway vehicle hoods. They are particularly suitable for use in tires (especially treads). [Examples]

[0068] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0069] [Synthesis of diene polymers] The following diene polymers were synthesized.

[0070] [Specific Modified Polymer 1] The specific modified polymer 1 was synthesized as follows.

[0071] <Polymerization process> 1150 mL of 1,3-butadiene, 100 mL of n-butyllithium, and 2,2-di(2-tetrahydrofuryl)propane were added to cyclohexane and heated and stirred (60°C, 24 hours) to obtain a butadiene polymer with active ends.

[0072] <End Degeneration Process> Next, 3-(triethoxysilyl)propylphosphonic acid diethyl (a compound represented by formula (1a) below) (a compound represented by formula (1), where X represents a propylene group and A1, A2, A3, Y and Z represent ethoxy groups) (100 mL) was added as a stopping agent (electrophile) to stop the polymerization. The polymerization solution was purified by adding it to a large amount of methanol and vacuum-dried at 50°C for 24 hours.

[0073] [ka]

[0074] As a result, a liquid butadiene polymer was obtained having a structure derived from the compound represented by formula (1a) at its terminal end and having a weight-average molecular weight of 15,000. The obtained liquid butadiene polymer is also called "specifically modified polymer 1". The viscosity of specificly modified polymer 1 was 2000 Pa·s, and the modification rate was 2.3 mol%. 31 P NMR (nuclear magnetic resonance) spectrum and 1 The 1H NMR spectra are shown in Figures 1 and 2.

[0075] [Specific Modified Polymer 2] A butadiene polymer was obtained by following the same procedure as for the specific modified polymer 1 described above, except that the amount of n-butyllithium was reduced during the polymerization process.

[0076] The obtained butadiene polymer was a liquid butadiene polymer having a structure derived from the compound represented by formula (1a) at its terminal end and a weight-average molecular weight of 40,000. The obtained liquid butadiene polymer is also called "specifically modified polymer 2". The viscosity of specificly modified polymer 2 was 4000 Pa·s, and the modification rate was 0.9 mol%.

[0077] [Unmodified polymer] Butadiene polymers were obtained by following the same procedure as for specific modified polymer 1 described above, except that methanol was used instead of 3-(triethoxysilyl)propylphosphonate diethyl in the terminal modification step.

[0078] The obtained butadiene polymer was a liquid butadiene polymer with unmodified ends and a weight-average molecular weight of 15,000. The obtained liquid butadiene polymer is also called an "unmodified polymer."

[0079] [Comparative Modified Polymer 1] A butadiene polymer was obtained by following the same procedure as for the specific modified polymer 2 described above, except that the amount of n-butyllithium was further reduced in the polymerization process.

[0080] The obtained butadiene polymer was a solid butadiene polymer having a structure derived from the compound represented by formula (1a) at its terminal end and a weight-average molecular weight of 100,000. The obtained butadiene polymer is also referred to as "comparatively modified polymer 1". The viscosity of comparatively modified polymer 1 was 6000 Pa·s, and the modification rate was 0.3 mol%.

[0081] [Comparative Modified Polymer 2] Butadiene polymers were obtained by following the same procedure as for the specific modified polymer 1 described above, except that methyltriethoxysilane was used instead of 3-(triethoxysilyl)propylphosphonate diethyl in the terminal modification step.

[0082] The obtained butadiene polymer was a liquid butadiene polymer having methyldiethoxysilyl groups at its termini and a weight-average molecular weight of 15,000. The obtained liquid butadiene polymer is also referred to as "comparatively modified polymer 2".

[0083] [Silica adsorption rate] 1.5 g of the obtained diene polymer and 3.0 g of silica were dissolved in 15 g of xylene, and the mixture was heated and stirred at 140°C for 20 minutes. The mixture was then filtered, recovered, and vacuum-dried at 80°C for 24 hours, after which the mass (final mass) was measured. The silica adsorption rate was then calculated using the following formula. (Silica adsorption rate) = (Final mass - Mass of silica used for evaluation) / (Mass of diene polymer used for evaluation) × 100 (Unit: %) The results are shown in Table 1 below. A higher silica adsorption rate indicates superior silica adsorption. In practical terms, a rate of 10% or higher is preferable.

[0084] [Table 1]

[0085] As can be seen from Table 1, compared to the unmodified polymer, which is a liquid diene polymer with unmodified ends, the modified liquid diene polymers (specific modified polymers) 1 and 2, which have a structure derived from the compound represented by formula (1) at their ends and have a weight-average molecular weight of 500 to 50,000, showed superior silica adsorption. In particular, specific modified polymer 1, which has a weight-average molecular weight of 30,000 or less, showed even better silica adsorption. Comparative Modified Polymer 1, a modified liquid diene polymer having a structure derived from the compound represented by formula (1) at its terminus but with a weight-average molecular weight exceeding 50,000, and Comparative Example Modified Polymer 2, a modified liquid diene polymer having a weight-average molecular weight of 500 to 50,000 but with a structure derived from methyltriethoxysilane (a compound other than the compound represented by formula (1)) at its terminus, exhibited insufficient silica adsorption.

[0086] [Preparation of rubber composition] The components shown in Table 2 below were blended in the proportions (parts by mass) shown in the table. Specifically, first, the components shown in Table 2 below were heated to approximately 150°C using a 1.7-liter sealed Banbury mixer, mixed for 5 minutes, then released and cooled to room temperature to obtain a masterbatch. Furthermore, using the same Banbury mixer, a vulcanization accelerator and sulfur were mixed into the obtained masterbatch to obtain a rubber composition. In Table 2, the parts by mass of SBR refers to the net amount of rubber (amount excluding oil).

[0087] [evaluation] The following evaluations were performed on the obtained rubber composition.

[0088] [The effects of pain] For the obtained rubber composition (unvulcanized), the strain shear modulus G' at a strain of 0.28% and the strain shear modulus G' at a strain of 30.0% were measured using a strain shear stress measuring instrument (RPA2000, manufactured by α-Technology Co., Ltd.), and the Payne effect (unvulcanized) was determined from the difference G'0.28 (MPa) - G'30.0 (MPa). Furthermore, the obtained rubber composition (unvulcanized) was press-vulcanized in a mold (15cm × 15cm × 0.2cm) at 160°C for 15 minutes to produce a vulcanized rubber sheet. The same measurements were then performed on the obtained vulcanized rubber sheet to determine the Payne effect (after vulcanization). The results are shown in Table 2. The results are expressed as an index with Comparative Example 1 set to 100. A smaller index indicates superior silica dispersibility.

[0089] [tanδ(60℃)] For the vulcanized rubber sheet prepared as described above, the loss tangent tanδ(60°C) was measured at a temperature of 60°C using a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.) under the conditions of initial strain of 10%, amplitude of ±2%, and frequency of 20Hz. The results are shown in Table 2. The results are expressed as an index with Comparative Example 1 set to 100. A smaller index indicates superior low heat generation.

[0090] [Table 2]

[0091] The details of each component in Table 2 are as follows: • SBR: TUFDENE E581 (SBR, glass transition temperature: -36°C, styrene content: 35.6% by mass, vinyl bond content: 41.3%, oil-expanded product (oil expansion amount: 37.5% by mass), manufactured by Asahi Kasei Chemicals Corporation) • BR: NIPOL BR1220 (BR, manufactured by Nippon Zeon Co., Ltd.) • Specific Modified Polymers 1-2: Specific modified polymers 1-2 synthesized as described above. • Unmodified polymer: Unmodified polymer synthesized as described above. • Comparative Modified Polymers 1-2: Comparative modified polymers 1-2 synthesized as described above. ·Silica: ZEOSIL 1165MP (CTAB adsorption specific surface area: 159m 2 (Manufactured by Rhodia) • Silane coupling agent: Si69 (bis(3-triethoxysilylpropyl)tetrasulfide, manufactured by Evonik DeGussa) • Carbon Black: Show Black N339 (manufactured by Cabot Japan Co., Ltd.) Process oil: Process oil • Anti-aging agent: Amine-based anti-aging agent (Santoflex 6PPD, manufactured by Flexis) Zinc oxide: Zinc oxide • Vulcanization accelerator (DPG): 1,3-diphenylguanidine (Noxellar DPG, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) • Vulcanization accelerator (CZ): N-cyclohexyl-2-benzothiazolyl sulfenamide (Noxellar CZ-G, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Sulfur: Sulfur

[0092] As can be seen from Table 2, Examples 1 and 2, which contain the specific modified polymer, showed superior silica dispersibility and low exothermic properties compared to Comparative Examples 1 to 4, which do not contain the specific modified polymer. < / x>

Claims

1. A modified liquid diene polymer having a structure derived from the compound represented by formula (1) at its terminal end, and having a weight-average molecular weight of 500 to 50,000. 【Chemistry 1】 In formula (1), X represents an alkylene group having 1 to 12 carbon atoms, an alkenylene group having 2 to 12 carbon atoms, or an aromatic group having 6 to 12 carbon atoms, and A １ A ２ A ３ Y and Z each independently represent an alkyl group, an alkoxy group, or a hydroxyl group.

2. The modified liquid diene polymer according to claim 1, wherein the viscosity is 2,000 Pa·s or more.

3. The modified liquid diene polymer according to claim 1 or 2, wherein the diene constituting the modified liquid diene polymer is 1,3-butadiene or isoprene.

4. The modified liquid diene polymer according to any one of claims 1 to 3, wherein the monomer constituting the modified liquid diene polymer includes aromatic vinyl as a monomer other than diene.

5. A rubber composition comprising 100 parts by mass of rubber having a weight-average molecular weight of 100,000 or more, 5 to 200 parts by mass of silica, and 1 to 50 parts by mass of a modified liquid diene polymer according to any one of claims 1 to 4.

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