Modified liquid diene polymer and method for producing the same

Abstract

To provide a diene polymer excellent in silica adsorption and a production method thereof.SOLUTION: There is provided a modified liquid diene polymer that is a liquid diene polymer or a liquid aromatic vinyl-diene copolymer having a specific functional group in the main chain, which is at least one functional group selected from the group consisting of a functional group represented by formula (1) below and another functional group represented by formula (2) below. In the formula (1) and the formula (2), R1 and R2 each independently indicate an alkylene group of 1-6 carbons, X1 indicates a carboxyl group, X2 and X3 each independently indicate a hydrogen atom or a carboxyl group, and "*" indicates a bond position. At least one of X2 and X3 is a carboxyl group.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a modified liquid diene polymer and a method for producing the same. [Background technology]

[0002] Diene polymers having adsorptivity to silica (silica adsorptivity) have been proposed (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 044893 Summary of the Invention [Problem to be solved by the invention]

[0004] Under these circumstances, the present inventors have studied the diene polymer described in Patent Document 1 and have found that further improvement in silica adsorption is desirable in view of various applications.

[0005] In view of the above circumstances, an object of the present invention is to provide a diene polymer having excellent silica adsorption properties and a method for producing the same. [Means for solving the problem]

[0006] As a result of extensive research into the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by a diene polymer having a specific functional group in the main chain, and have arrived at the present invention. That is, the present inventors have found that the above problems can be solved by the following configuration.

[0007] (1) A modified liquid diene polymer, which is a liquid diene polymer or a liquid aromatic vinyl-diene copolymer, having in its main chain a specific functional group, which is at least one functional group selected from the group consisting of a functional group represented by formula (1) described below and a functional group represented by formula (2) described below. (2) The liquid diene polymer is at least one liquid polymer selected from the group consisting of butadiene and isoprene, or The modified liquid diene polymer according to (1) above, wherein the liquid aromatic vinyl-diene copolymer is a liquid copolymer of styrene and at least one selected from the group consisting of butadiene and isoprene. (3) The modified liquid diene polymer according to (1) or (2) above, which has a weight-average molecular weight of 1,000 to 100,000. (4) The specific functional group is a functional group represented by the formula (2), The modified liquid diene polymer according to any one of the above (1) to (3), wherein in the above formula (2), R2 is a methylene group, and X2 and X3 are carboxy groups. (5) The modified liquid diene polymer according to any one of (1) to (4) above, wherein the average number of the specific functional groups per molecule is 1 to 10. (6) a liquid diene polymer or a liquid aromatic vinyl-diene copolymer; a radical initiator; A method for producing a modified liquid diene polymer, comprising reacting a compound represented by formula (1A) described below with a specific compound which is at least one compound selected from the group consisting of a compound represented by formula (1A) described below and a compound represented by formula (2A) described below, to obtain the modified liquid diene polymer described in (1) above. (7) The liquid diene polymer is at least one liquid polymer selected from the group consisting of butadiene and isoprene, or The method for producing a modified liquid diene polymer according to (6) above, wherein the liquid aromatic vinyl-diene copolymer is a liquid copolymer of styrene and at least one selected from the group consisting of butadiene and isoprene. (8) The method for producing a modified liquid diene polymer according to (6) or (7) above, wherein the modified liquid diene polymer has a weight average molecular weight of 1,000 to 100,000. (9) The method for producing a modified liquid diene polymer according to any one of (6) to (8) above, wherein the specific compound is mercaptosuccinic acid. (10) The method for producing a modified liquid diene polymer according to any one of (6) to (9) above, wherein the average number of the specific functional groups per molecule of the modified liquid diene polymer is 1 to 10. [Effects of the Invention]

[0008] As will be described below, the present invention can provide a diene polymer having excellent silica adsorption properties and a method for producing the same. DETAILED DESCRIPTION OF THE INVENTION

[0009] The modified liquid diene polymer of the present invention and its production method will be described below. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In addition, in this specification, each component may be used alone or in combination of two or more. When two or more components are used in combination, the amount of each component refers to the total amount unless otherwise specified. In addition, in this specification, the term "liquid" means that the substance is in a liquid state at 20°C and 1 atmosphere.

[0010] [Modified liquid diene polymer] The modified liquid diene polymer of the present invention (hereinafter also referred to as "polymer of the present invention") is The modified liquid diene polymer is a liquid diene polymer or a liquid aromatic vinyl-diene copolymer having, in its main chain, a specific functional group which is at least one functional group selected from the group consisting of a functional group represented by formula (1) described below and a functional group represented by formula (2) described below.

[0011] The reason why the polymer of the present invention has excellent silica adsorption properties is not clear, but since sufficient silica adsorption properties are not observed when the functional group of the main chain has an alkoxysilyl group instead of a carboxy group (Comparative Example 1 described later) or when the functional group of the main chain has a carboxy group but does not have a specific structure (sulfur atom, etc.), it is speculated that excellent silica adsorption properties are exhibited when the functional group (specific functional group) of the main chain has a carboxy group and a specific structure (sulfur atom, etc.).

[0012] The polymer of the present invention will be described in detail below.

[0013] [Skeleton] The skeleton (main chain structure) of the polymer of the present invention is not particularly limited as long as it is a liquid diene polymer (liquid diene polymer) or a liquid aromatic vinyl-diene copolymer (liquid aromatic vinyl-diene copolymer). Hereinafter, "liquid diene polymer" and "liquid aromatic vinyl-diene copolymer" will also be collectively referred to as "liquid diene polymer." The diene polymer is a polymer of a diene (particularly a conjugated diene). The diene polymer may be a homopolymer or a copolymer, but is preferably a homopolymer because the effects of the present invention are more excellent. An aromatic vinyl-diene copolymer is a copolymer of an aromatic vinyl and a diene (particularly a conjugated diene). The copolymer may be a random copolymer or a block copolymer. The skeleton is preferably a diene polymer because the effects of the present invention are more excellent.

[0014] Specific examples of the diene of the diene polymer include butadiene, isoprene, chloroprene, etc. The diene is preferably butadiene or isoprene, more preferably butadiene, because the effects of the present invention are more excellent. Specific examples of the aromatic vinyl in the aromatic vinyl-diene copolymer include styrene. Specific examples and preferred embodiments of the diene in the aromatic vinyl-diene copolymer are the same as those of the diene polymer.

[0015] Specific examples of the liquid diene polymer include liquid butadiene polymers (BR), isoprene polymers (IR), chloroprene polymers (CR), isoprene-butadiene copolymers (IBR), styrene-butadiene copolymers (SBR), and isoprene-styrene copolymers.

[0016] <Preferred embodiment> The liquid diene polymer is preferably at least one liquid polymer selected from the group consisting of butadiene and isoprene, or a copolymer of at least one liquid polymer selected from the group consisting of butadiene and isoprene with styrene, more preferably at least one liquid polymer selected from the group consisting of butadiene and isoprene, and even more preferably a liquid butadiene polymer.

[0017] <Molecular weight> The preferred embodiment of the molecular weight of the liquid diene polymer is the same as the molecular weight of the polymer of the present invention described below.

[0018] [Specific functional group] The polymer of the present invention has, in its main chain, a specific functional group which is at least one type of functional group selected from the group consisting of functional groups represented by the following formula (1) and functional groups represented by the following formula (2). The specific functional group is preferably a functional group represented by formula (2) because the effects of the present invention are more excellent.

[0019] [ka]

[0020] [ka]

[0021] In formula (1) and formula (2), R1 and R2 each independently represent an alkylene group having 1 to 6 carbon atoms; X1 represents a carboxy group; X2 and X3 each independently represent a hydrogen atom or a carboxy group; * indicates the bond position. However, at least one of X2 and X3 is a carboxy group.

[0022] R1 and R2 are preferably alkylene groups with 1 to 3 carbon atoms, and more preferably alkylene groups with 1 to 2 carbon atoms, because this provides better effects of the present invention.

[0023] It is preferable that both X2 and X3 are carboxy groups, since this will result in better effects of the present invention.

[0024] <Number of main chain functional groups> The number of main chain functional groups of the polymer of the present invention is preferably 1 to 10, more preferably 2 to 8, and even more preferably 3 to 6, for reasons of better effects of the present invention. Here, the number of main chain functional groups refers to the number of specific functional groups that the polymer of the present invention has in the main chain (average number per molecule).

[0025] <Degeneration rate> The modification rate of the polymer of the present invention is preferably 1.0 to 10.0 mol %, more preferably 2.0 to 5.0 mol %, because the effects of the present invention are more excellent. Here, the modification ratio refers to the ratio of the number of specific functional groups (average number per molecule) in the main chain of the polymer of the present invention to the degree of polymerization of the polymer of the present invention, which is calculated from the weight-average molecular weight (Mw) of the polymer of the present invention and the molecular weight of the repeating unit constituting the polymer of the present invention.

[0026] [Molecular weight] The weight average molecular weight (Mw) of the polymer of the present invention is preferably from 1,000 to 100,000, more preferably from 5,000 to 50,000, and even more preferably from 8,000 to 20,000, because the effects of the present invention are more excellent. The number average molecular weight (Mn) of the polymer of the present invention is preferably from 1,000 to 100,000, more preferably from 5,000 to 50,000, and even more preferably from 8,000 to 20,000, because the effects of the present invention are more excellent. In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) are values ​​calculated as standard polystyrene obtained by gel permeation chromatography (GPC) measurement under the following conditions. Solvent: Tetrahydrofuran Detector: RI detector

[0027] [Liquid] The polymer of the present invention is liquid at 20° C. and 1 atmosphere.

[0028] [Method of producing the polymer of the present invention] The method for producing the polymer of the present invention is not particularly limited. However, in order to improve the silica adsorption property of the resulting polymer of the present invention, the following method is preferred: a liquid diene polymer or a liquid aromatic vinyl-diene copolymer (liquid diene polymer); a radical initiator; A method for obtaining the polymer of the present invention by reacting a specific compound, which is at least one compound selected from the group consisting of a compound represented by formula (1A) described below and a compound represented by formula (2A) described below (hereinafter also referred to as "Production Method 1") is preferred. In the above-mentioned production method 1, a hydrogen atom is abstracted from the α-carbon atom of the double bond of the liquid diene-based polymer by a radical initiator, and the specific compound reacts with the hydrogen atom to introduce the above-mentioned specific functional group into the main chain of the liquid diene-based polymer. The reaction in the above Production Method 1 is preferably carried out in bulk or in an organic solvent, since the resulting polymer of the present invention has better silica adsorption properties. Hereinafter, "the silica adsorption property of the obtained polymer of the present invention is superior" will also be referred to as "the effect of the present invention is superior."

[0029] Each component used in Production Method 1 will be described below.

[0030] [Liquid Diene Polymer] The definition, specific examples and preferred embodiments of the liquid diene polymer are the same as those of the polymer skeleton of the present invention described above.

[0031] [Radical initiator] The radical initiator is not particularly limited, and specific examples thereof include benzoyl peroxide, t-butyl peroxybenzoate, dicumyl peroxide, t-butylcumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, 2,5-dimethyl-2,5-di-t-butylperoxy-3-hexyne, 2,4-dichloro-benzoyl peroxide, di-t-butylperoxy-di-isopropylbenzene, 1,1-bis(t-butylperoxy)-3,3,5-trimethyl-cyclohexane, n-butyl-4,4-bis(t-butyl and organic peroxides such as 2,2-bis(t-butylperoxy)valerate and 2,2-bis(t-butylperoxy)butane; radical generators such as azodicarbonamide, azobisisobutyronitrile (AIBN), 2,2'-azobis-(2-amidinopropane) dihydrochloride, dimethyl 2,2'-azobis(isobutyrate), azobis-cyanovaleric acid, 1,1'-azobis-(cyclohexane-1-carbonitrile), 2,2'-azobis-(2,4-dimethylvaleronitrile), azobismethylbutyronitrile, and 2,2'-azobis-(4-methoxy-2,4-dimethylvaleronitrile). The radical initiator is preferably azobisisobutyronitrile (AIBN) because this provides a better effect of the present invention.

[0032] <Amount added> The amount of the radical initiator added is not particularly limited, but in order to obtain better effects of the present invention, it is preferably 0.1 to 10% by mass, and more preferably 1 to 5% by mass, relative to the liquid diene polymer.

[0033] [Specific compound] As described above, in Production Method 1, a specific compound is used, which is at least one compound selected from the group consisting of compounds represented by formula (1A) and compounds represented by formula (2A). The specific compound is preferably a compound represented by formula (2A) because the effects of the present invention are more excellent.

[0034] [ka]

[0035] [ka]

[0036] In formula (1A) and formula (2A), R1 and R2 each independently represent an alkylene group having 1 to 6 carbon atoms; X1 represents a carboxy group; X2 and X3 each independently represent a hydrogen atom or a carboxy group. However, at least one of X2 and X3 is a carboxy group.

[0037] Specific examples and preferred embodiments of each symbol in formula (1A) and formula (2A) are the same as those in formula (1) and formula (2) described above.

[0038] <Example> Specific examples of the compound represented by formula (1A) include mercaptoacetic acid, mercaptopropionic acid, etc. Among these, mercaptoacetic acid is preferred because it provides better effects of the present invention. Specific examples of the compound represented by formula (2A) include mercaptosuccinic acid, 2-mercaptoglutaric acid, 2-mercaptoadipic acid, etc. Among these, mercaptosuccinic acid is preferred because it provides better effects of the present invention.

[0039] <Amount added> The amount of the specific compound added is not particularly limited, but in order to obtain better effects of the present invention, it is preferably 1 to 50% by mass, more preferably 5 to 40% by mass, and even more preferably 15 to 30% by mass relative to the liquid diene polymer.

[0040] [Preferred embodiment] The above-mentioned production method 1 is preferably a method including the following steps (1) and (2) (hereinafter also referred to as "production method 2"), because the effects of the present invention are more excellent.

[0041] (1) Monomer polymerization process A step of polymerizing a diene-containing monomer using an organolithium compound to obtain a liquid diene-based polymer. (2) Main chain modification process A step of obtaining the polymer of the present invention by reacting the liquid diene polymer with a radical initiator and the specific compound described above.

[0042] Each step of the manufacturing method 2 will be described below.

[0043] <Monomer polymerization process> The monomer polymerization step is a step in which a diene-containing monomer is polymerized using an organolithium compound to obtain a liquid diene-based polymer.

[0044] (Diene-containing monomers) Regarding the diene-containing monomer, specific examples and preferred embodiments of the diene (particularly the conjugated diene) are the same as those of the liquid diene polymer having the skeleton of the polymer of the present invention described above. The above-mentioned monomers may contain an aromatic vinyl as a monomer other than the diene. Specific examples and preferred embodiments of the aromatic vinyl are the same as those of the diene polymer having the skeleton of the polymer of the present invention.

[0045] (organolithium compounds) The organolithium compound is not particularly limited, and specific examples thereof include monoorganolithium compounds such as n-butyllithium, sec-butyllithium, tert-butyllithium, n-propyllithium, isopropyllithium, 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-tirithiobenzene, and 1,3,5-tirithio-2,4,6-triethylbenzene. Among these, the monoorganolithium compounds n-butyllithium, sec-butyllithium, and tert-butyllithium are preferred, and n-butyllithium is more preferred, due to the superior effects of the present invention.

[0046] The amount of the organolithium compound used is not particularly limited, but is preferably 0.001 to 10 mol % relative to the monomer, because this provides a better effect of the present invention.

[0047] <Main chain modification process> The main chain modification step is a step of reacting the liquid diene polymer with a radical initiator and the specific compound described above to introduce the specific functional group into the main chain of the liquid diene polymer, thereby obtaining the polymer of the present invention. The main chain modification step is the same as in the above-mentioned production method 1.

[0048] [Application] The polymer of the present invention is suitably used for rubber compositions, tires, conveyor belts, hoses, vibration-proof materials, rubber rolls, outer covers of railway vehicles, etc. In particular, it is suitably used for tires (particularly treads). [Example]

[0049] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0050] [Production of modified liquid diene polymer] A modified liquid diene polymer was produced as follows. The modified liquid diene polymers of Examples 1 to 3 are liquid diene polymers having a specific functional group in the main chain, and therefore fall within the scope of the present invention, whereas the modified liquid diene polymer of Comparative Example 1 is a liquid diene polymer not having a specific functional group in the main chain, and therefore does not fall within the scope of the present invention.

[0051] Example 1 The modified liquid diene polymer of Example 1 was produced as follows.

[0052] (Monomer polymerization process) 1,200 mL of 1,3-butadiene, 30 mL of n-butyllithium, and 0.1 mL of 2,2-di(2-tetrahydrofuryl)propane were added to 4.2 kg of cyclohexane and heated and stirred (60°C, 24 hours) to polymerize 1,3-butadiene. Then, 40 mL of methanol was added and stirred (room temperature, 2.0 hours) to terminate the polymerization. The polymerization solution was then added to a large amount of methanol for purification, and vacuum dried at 50°C for 24 hours to obtain a liquid butadiene polymer with a molecular weight of 10,000.

[0053] (Main chain modification process) 200 g of the obtained liquid butadiene polymer, 40 g of mercaptoacetic acid (corresponding to the compound represented by formula (1A) above), and 2.5 g of AIBN (azobisisobutyronitrile) were added to 200 mL of MEK (methyl ethyl ketone), and the mixture was heated and stirred (80°C, 24 hours). The reaction solution was added to a large amount of methanol for purification, and then vacuum dried at 50°C for 24 hours to obtain a modified liquid butadiene polymer (Mw: 10,000) that is a liquid butadiene polymer having a functional group represented by the above formula (1) (wherein R1 is a methylene group) in its main chain. The number of the above functional groups in the main chain (average number per molecule) in the obtained modified liquid butadiene polymer was 5.

[0054] <Example 2> A modified liquid butadiene polymer was obtained by the same procedure as in Example 1, except that 40 g of mercaptosuccinic acid (corresponding to the compound represented by the above formula (2A)) was used instead of 40 g of mercaptoacetic acid in the main chain modification step. The obtained modified liquid butadiene polymer was a modified liquid butadiene polymer (Mw: 10,000) that is a liquid butadiene polymer having in its main chain a functional group represented by the above formula (2) (wherein, in formula (2), R2 is a methylene group, and X2 and X3 are both carboxy groups). In the obtained modified liquid butadiene polymer, the number of the above functional groups in the main chain (average number per molecule) was 5.

[0055] Example 3 A modified liquid butadiene polymer was obtained according to the same procedure as in Example 2, except that 20 g of mercaptosuccinic acid was used instead of 40 g of mercaptosuccinic acid in the main chain modification step. The obtained modified liquid butadiene polymer was a modified liquid butadiene polymer (Mw: 10,000) that is a liquid butadiene polymer having a functional group represented by the above formula (2) (wherein, in formula (2), R2 is a methylene group, and X2 and X3 are both carboxy groups) in the main chain. In the obtained modified liquid butadiene polymer, the number of the above functional groups in the main chain (average number per molecule) was 4.

[0056] <Comparative Example 1> A modified liquid butadiene polymer was obtained following the same procedure as in Example 1, except that 50 g of 3-mercaptopropyltriethoxysilane (a compound not falling under the above-mentioned specific compounds) was used instead of 40 g of mercaptoacetic acid in the main chain modification step. The obtained modified liquid butadiene polymer was a modified liquid butadiene polymer (Mw: 10,000) that is a liquid butadiene polymer having a functional group represented by *-S-C3H6-Si(OC2H5)3 (where * indicates a bonding position) (a functional group not falling under the above-mentioned specific functional groups) in its main chain. The obtained modified liquid butadiene polymer had 5 such functional groups in its main chain (average number per molecule).

[0057] [Silica adsorption rate] 1.5 g of the resulting modified liquid 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, and 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 modified liquid diene polymer used for evaluation) x 100 (unit: %) The results are shown in the following Table 1. A higher silica adsorption rate indicates better silica adsorption ability.

[0058] [Table 1]

[0059] In Table 1, the number of main chain functional groups represents the number of functional groups in the main chain (average number per molecule), and the modification ratio represents the ratio of the number of functional groups in the main chain of a polymer (average number per molecule) to the degree of polymerization of the polymer.

[0060] As can be seen from Table 1, the modified liquid diene polymers of Examples 1 to 3 having specific functional groups exhibited superior silica adsorption properties compared to the modified liquid diene polymer of Comparative Example 1 having no specific functional groups in the main chain. Among them, Examples 2 and 3 in which the specific functional group was a functional group represented by formula (2) (wherein X2 and X3 are both carboxy groups) exhibited even superior silica adsorption properties. Furthermore, a comparison between Examples 2 and 3 (comparison between embodiments differing only in the number of main chain functional groups) shows that Example 2, in which the number of main chain functional groups is more than 4, exhibits superior silica adsorption properties.

Claims

1. Silica, A rubber composition containing a liquid diene polymer or a modified liquid diene polymer that is a liquid aromatic vinyl-diene copolymer, having a specific functional group represented by the following formula (2) in its main chain: 【Chemical 1】 In formula (2), R ２ represents an alkylene group having 1 to 6 carbon atoms, X ２ and X ３ represents a carboxy group, * indicates the bond position.

2. The liquid diene polymer is at least one liquid polymer selected from the group consisting of butadiene and isoprene, or The rubber composition according to claim 1, wherein the liquid aromatic vinyl-diene copolymer is a liquid copolymer of styrene and at least one selected from the group consisting of butadiene and isoprene.

3. A rubber composition according to claim 1 or 2, wherein the weight average molecular weight of the modified liquid diene polymer is 1,000 to 100,000.

4. In the formula (2), R ２ The rubber composition according to any one of claims 1 to 3, wherein is a methylene group.

5. A rubber composition described in any one of claims 1 to 4, wherein the average number of the specific functional groups per molecule of the modified liquid diene-based polymer is 1 to 10.

6. A method for producing a rubber composition, comprising the steps of: The modified liquid diene polymer is a liquid diene polymer or a liquid aromatic vinyl-diene copolymer; a radical initiator; A method for producing a rubber composition by reacting a specific compound represented by the following formula (2A): 【Chemistry 2】 In formula (2A), R ２ represents an alkylene group having 1 to 6 carbon atoms, X ２ and X ３ represents a carboxy group.

7. The liquid diene polymer is at least one liquid polymer selected from the group consisting of butadiene and isoprene, or The method for producing a rubber composition according to claim 6, wherein the liquid aromatic vinyl-diene copolymer is a liquid copolymer of styrene and at least one selected from the group consisting of butadiene and isoprene.

8. The method for producing a rubber composition according to claim 6 or 7, wherein the weight average molecular weight of the modified liquid diene polymer is 1,000 to 100,000.

9. The method for producing a rubber composition according to any one of claims 6 to 8, wherein the specific compound is mercaptosuccinic acid.

10. The method for producing a rubber composition according to any one of claims 6 to 9, wherein the average number of the specific functional groups per molecule of the modified liquid diene polymer is 1 to 10.

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