JPH0158212B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a rubber composition that has excellent processability, an improved vulcanization rate, and provides excellent vulcanizable properties. In recent years, rubber has been used in a wide variety of applications, and its required performance has become more complex. In response to this trend, various new types of rubber and auxiliary materials for rubber have appeared. Among these, various liquid rubbers have been proposed as plasticizers (modifiers) for solid rubber, and are currently being used in some applications. For example, various liquid rubbers without functional groups have been proposed as reactive plasticizers for solid rubber, and liquid rubbers with carboxyl groups and acid anhydride groups in the branch chain have been proposed as reactive plasticizers to improve adhesion. . Each of these liquid rubbers has its own characteristics, and although they are useful as rubber plasticizers (modifiers), they are not necessarily fully satisfactory for all uses.
That is, although the former liquid rubber has an excellent plasticizing effect on solid rubber, it cannot be expected to improve the modulus and hardness when made into a vulcanized product, while the latter liquid rubber has an effect of improving the modulus and hardness. However, the plasticizing effect is generally small, and the vulcanization rate during vulcanization is slow. The present inventors have made intensive studies to improve the drawbacks of the conventional rubber plasticizers (modifiers) mentioned above and to obtain an excellent vulcanized rubber composition. It was discovered that when used as an agent, it has excellent plasticity and therefore processability, and when vulcanized, it has excellent vulcanized physical properties such as modulus and hardness, and the vulcanization rate is improved, and the present invention was completed. I came to the point. According to the present invention, the above-mentioned object is to provide a solid rubber composition containing a plasticizer, in which the plasticizer is a low molecular weight diene rubber having a molecular weight of 6,000 to 100,000 and a vinyl bond content of 35% or less. General formula () as a chain (Here, R represents a hydrocarbon residue having up to 20 carbon atoms in which an oxygen atom or a sulfur atom may be interposed in the main chain, and A is

[Formula] (R ¹ or R ² represents a hydrocarbon residue having up to 20 carbon atoms) or a heterocyclic residue containing a tertiary nitrogen atom as a heteroatom) This is achieved by using a modified low molecular weight diene rubber containing 0.1 to 10 moles of a succinimide derivative residue containing a group having a tertiary amino group at the N-position, per 100 monomer units in the rubber. Ru. In addition, in the general formula (), hydrogen in the succinimide ring, especially 2 bonded to the carbon atom
Any one of the hydrogen atoms may be eliminated to form a single bond with the rubber main chain molecule. That is, the general formula () is It may take the form of The solid rubber used in the present invention is a diene rubber having a molecular weight of 200,000 or more, examples of which include natural rubber, synthetic polyisoprene rubber, butadiene-isoprene copolymer rubber, styrene-butadiene copolymer rubber, and styrene-based rubber. Isoprene copolymer rubber, butadiene-acrylonitrile copolymer,
Examples include isoprene-acrylonitrile copolymer rubber, chloroprene rubber, butyl rubber, and ethylene-propylene-diene copolymer rubber. The modified low molecular weight diene rubber used in the present invention is obtained by (a) adding a maleic acid compound such as maleic anhydride, maleic acid, maleic acid monoester, or maleic diester to a low molecular weight diene rubber by an addition reaction; , succinyl residues such as succinic anhydride, succinic acid, succinic monoester (succinate), and succinic diester (succinate) residues are introduced as side chains. Then, the general formula () H ₂ N-R-A (where R represents a hydrocarbon residue having up to 20 carbon atoms in which an oxygen atom or a sulfur atom may be interposed in the main chain, and A is ,

[Formula] (R ¹ or R ² represents a hydrocarbon residue with up to 20 carbon atoms)
(indicates an amino residue represented by or a heterocyclic residue containing a tertiary nitrogen atom as a heteroatom)
After reacting with the amine represented by, a (succinyl)imide ring is formed by dehydration or dealcoholization, or (b) a low molecular weight diene rubber is formed with the general formula (). (Here, R and A are each the same as those shown in the general formula ().) It is produced by adding a maleimide derivative represented by the following by an addition reaction, or by the following steps. Examples of the low molecular weight diene rubber that is the base of the modified low molecular weight diene rubber used in the present invention include polybutadiene, polyisoprene, butadiene-isoprene copolymer, butadiene-styrene copolymer, isoprene-styrene copolymer, and butadiene-styrene copolymer. Examples include acrylonitrile copolymer and isoprene-acrylonitrile copolymer.
Among these, polymers mainly composed of isoprene, particularly polyisoprene, are preferred. If the molecular weight of these low molecular weight diene rubbers is too low, there will be no problem with the plasticizing effect when the finally obtained modified low molecular weight diene rubber is blended into solid rubber, but the physical properties will deteriorate when vulcanized. On the other hand, if it is too high, problems will arise in the reaction for modification, and when the obtained modified low molecular weight diene rubber is blended into solid rubber, a sufficient plasticizing effect will not be observed. From this point of view, the molecular weight needs to be 6,000 to 100,000, preferably 15,000 to 70,000. Note that the molecular weight here means a viscosity average molecular weight, which is determined from the intrinsic viscosity measured in toluene at 30°C. If the amount of vinyl bonds in low molecular weight diene rubber is too large, the viscosity of the low molecular weight diene rubber itself becomes high, which not only impairs handling efficiency during the modification reaction, but also makes it difficult to use solid rubber as modified low molecular weight diene rubber. If it is added to the vulcanizate, the plasticizing effect will be reduced and the physical properties of the vulcanizate will also be deteriorated. Therefore, it is essential that the vinyl bond amount is 35% or less, preferably 20% or less. Note that vinyl bonds here include 1, 2 bonds and 3, 4 bonds.
It means a bond, and the vinyl bond amount refers to a value measured by infrared absorption spectrum. Such low molecular weight diene rubbers are produced by Ziegler polymerization, anionic polymerization or radical polymerization using conjugated dienes such as butadiene monomers and isoprene monomers. It can also be produced by reducing the molecular weight of a high molecular weight polymer such as the conjugated diene mentioned above or natural rubber by, for example, a thermal decomposition method. In the present invention, when producing the modified low molecular weight diene rubber by the method (a) above, the amine to be reacted with the low molecular weight diene rubber to which maleic anhydride, maleic acid, maleic acid monoester or maleic acid diester has been added is , is represented by the general formula () H ₂ N-R-A, where R is (a) an alkylene residue having up to 20 carbon atoms, which may be branched, and (b) a cycloalkylene residue having up to 20 carbon atoms. (c) General formula (-R ³ -Z) - _o R ⁴ (where R ³ and R ⁴ are the same or different alkylenes selected from the group consisting of ethylene group, lower alkyl-substituted ethylene group, and propylene group) a heteroatom-containing hydrocarbon residue having up to 20 carbon atoms, Z is an oxygen atom or a sulfur atom, and n is an integer of 1 or more; (d) an aromatic group having up to 20 carbon atoms; or (e) an aromatic hydrocarbon residue having up to 20 carbon atoms and containing a heteroatom such as an oxygen atom or a sulfur atom. Among these, alkylene residues such as ethylene, propylene, butylene, isobutylene, and pentylene, cycloalkylene residues such as cyclopentylene and cyclooctylene, and ethoxyethylene and ethoxypropylene are selected from the viewpoint of economy and availability. Oxygen atom-containing alkylene residues such as oxyalkylene residues are preferred.
A is a general formula such as (i) dialkylamino residue having up to 20 carbon atoms, (ii) diarylamino residue having up to 20 carbon atoms, (iii) dialkylamino residue having up to 20 carbon atoms, etc.

Amino residue represented by [Formula], or (iv) 5 containing a tertiary nitrogen atom as a heteroatom
membered ring or 6-membered ring heterocyclic residues, etc. Among them, dicyclo, which is represented by dialkylamino residues such as dimethylamino, diethylamino, dibutylamino, diisobutylamino, and dipentylamino, and dicyclopentylamino residues. Alkylamino residues are preferred. Typical examples of such amines include (dialkylamino)alkylamines, (N,N-dialkylaminoalkoxy)alkylamines, amines in which the alkoxy moiety of the amines is polyalkoxy, p-N,N- dialkylaminomethylbenzylamine, p-N,N-dialkylphenylamine, N-aminoalkylpiperidine, N-aminoalkylpipecoline, N-aminoalkylmorpholine, 1-aminoalkyl-4-
Alkylpiperazine, aminoalkylpyridine,
Examples include picolylamine. Among these, (dimethylamino)ethylamine, (dimethylamino)ethylamine, (dipropylamino)ethylamine, (dimethylamino)propylamine, (diethylamino)propylamine, (dimethylamino)butylamine, (diethylamino)butylamine, (dimethyl amino)
(dialkylamino)alkylamines, such as hexylamine or (dimethylamino)decylamine;
(N,N-dimethylamino)ethoxyethylamine (N,N-dimethylamino)ethoxypropylamine, and also α-(3-aminopropyl)-w
-(3-dimethylamino)propyl)oxy-poly(oxy-1,2-ethanediyl) ( However, (n is an integer from 1 to 7) etc.
N-alkylamino)alkoxyalkylamines are preferably used. In addition, when polyethyleneimine, amino alcohol, or N,N'-diphenyl-p-phenylenediamine is used instead of the above-mentioned amine, the desired effect of the present invention can be achieved as described in the comparative example below. Purpose not achieved. Furthermore, the maleimide derivative used in producing the modified low molecular weight diene rubber used in the present invention by the method (b) above has the general formula () where R and A are respectively the same as defined in general formula () or (). Maleimide derivatives preferably used in the present invention include N-(β-dimethylamino)
Ethylmaleimide, N-(β-diethylamino)
Ethylmaleimide, N-(γ-dimethylamino)
Propylmaleimide, N-(γ-diethylamino)
Propylmaleimide, N-(δ-dimethylamino)
Butylmaleimide, N-(δ-diethylamino)
N-(dialkylamino) such as butylmaleimide
Examples include alkylmaleimides. Various known methods can be used to add a maleic acid compound such as maleic anhydride, maleic acid, maleic acid monoester, maleic diester, or maleimide derivative represented by the general formula () to a low molecular weight diene rubber. For example, a heat addition method in which a low molecular weight diene rubber and a maleic acid compound are mixed and stirred under high heat is preferably employed. In this case, it is possible to use radical initiation catalysts such as peroxides and azo compounds. Examples include benzoyl peroxide and azobisisobutylnitrile. It is also possible to use inert hydrocarbon solvents such as hexane, toluene or benzene. The reaction temperature is preferably 60 to 250°C, particularly 100 to 200°C, and the reaction time is preferably 1 to 20 hours. The reaction in which the amine represented by the general formula () is reacted with a low molecular weight diene rubber to which maleic anhydride, maleic acid, maleic acid monoester or maleic acid diester is added is carried out at a temperature of 0 to 220°C.
The duration ranges from 0.1 minute to 20 hours. In this reaction, an acid anhydride group or a carbonyl group is first amidated, and then imidized by dehydration or dealcoholization. In addition to the above-mentioned succinimide derivative residues, the functional groups added to the low molecular weight diene rubber include small amounts of acid anhydride groups, carboxyl groups, carboxylic acid residues, and carboxylic acid residues as long as they do not adversely affect physical properties. There is no problem even if other functional groups such as amide residues or acrylamide residues are present. In this way, a modified low molecular weight diene rubber containing a succinimide derivative residue represented by the general formula () in the side chain is obtained, but if the content is too small, the modified low molecular weight diene rubber becomes a solid rubber. When these are blended together and vulcanized, improvements in vulcanization rate and vulcanized physical properties such as hardness and modulus cannot be realized. On the other hand, if the content is too large, the compatibility with solid rubber will deteriorate, and when blended into solid rubber, the physical properties of the final vulcanized rubber will be greatly reduced. Therefore, the content of the succinimide derivative residue is 0.1 to 20 moles per 100 monomer units in the low molecular weight diene rubber (hereinafter simply referred to as content),
In particular, it is preferably in the range of 1 to 10 moles. The modified low molecular weight diene rubber used in the present invention exhibits an excellent plasticizing effect when blended with solid rubber, and when the solid rubber composition is vulcanized, the vulcanization rate increases, and the vulcanized material properties are improved. In particular, the modulus and hardness are significantly improved. The modified low-molecular-weight diene rubber of the present invention improves the vulcanization rate as described above, so it is possible to reduce the amount of vulcanization accelerator used, and in some cases, it is possible to reduce the amount of vulcanization accelerator used. It may not be used at all. The reduction of vulcanization accelerator is
Since it leads to a reduction in the bloom phenomenon of the vulcanization accelerator, it is advantageous in terms of adhesion of the rubber composition during unvulcanization, provides a preferable appearance of the rubber product, and furthermore has the advantage of reducing variations in product physical properties. will occur. When blending modified low molecular weight diene rubber into solid rubber, the blending ratio is: modified low molecular weight diene rubber/modified low molecular weight diene rubber/
The weight ratio of solid rubber is 3/97 to 60/80, more preferably 5/95 to 35/65. When blending the modified low molecular weight diene rubber into solid rubber, various rubber compounding chemicals that are commonly used in the production of rubber products are used as necessary.
Examples include vulcanizing agents such as sulfur and peroxide, vulcanization aids such as zinc oxide and stearic acid, vulcanization accelerators, anti-aging agents, carbon black (soft carbon black, hard carbon black),
Fillers such as silica, calcium carbonate or clay, softeners (oils), resins such as rosin resins, terpene resins, petroleum resins, phenolic resins, epoxy resins or polyester resins are included. The solid rubber composition containing the modified low molecular weight diene rubber of the present invention can be used in various parts of automobile tires such as treads, carcass, beads, bead fillers, rim strips, conveyor belts, V-belts, etc.
It is used for manufacturing industrial products such as hoses, anti-vibration materials, and rubber rolls, as well as rubber products such as rubberized cloth, rubber thread, rubber bands, rubber footwear, and sponge rubber. EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples in any way. The physical properties of the rubber in the examples were evaluated in accordance with JISK-6301. Furthermore, "parts" and "%" in the examples are based on weight unless otherwise specified. Example 1 Low molecular weight polyisoprene rubber with a vinyl bond content of 14% and a molecular weight of 31,000 obtained by polymerizing isoprene monomer using butyllithium as a catalyst (abbreviated as LIR-A in Table 1) ) and maleic anhydride at 180° C. for 7 hours to obtain a first modified low molecular weight polyisoprene rubber. The isoprene monomer unit in the rubber was determined by infrared absorption spectroscopy.
Modified low molecular weight polyisoprene rubber with 3.2 mol of succinic anhydride residue added per 100 ml (see Table 1)
(abbreviated as LIR-B). In addition,
Identification and quantification of succinic anhydride residues were performed using the carbonyl of the acid anhydride group at 1790 cm ^-1 and 1870 cm ^-1 . After reacting modified low molecular weight polyisoprene rubber containing succinic anhydride residues (LIR-B) with N,N-dimethylaminopropylamine at 100°C,
A second modified low molecular weight polyisoprene rubber was obtained by heating at 160°C. When the rubber was examined by infrared absorption spectrography, it was found that
Almost all of the acid anhydride groups in the modified low molecular weight polyisoprene rubber react with the primary amino groups in N,N-dimethylaminopropylamine, resulting in N-(γ
It was found that a modified low molecular weight polyisoprene rubber (hereinafter abbreviated as LIR-D in Table 1) to which a -dimethylamino)propyl succinimide residue was added was produced. The identification and quantification of N-(γ-dimethylamino)propyl succinimide is based on the extinction of the absorption attributable to the carbonyl of the acid anhydride group near 1790 cm ^-1 or 1870 cm ^-1 and the absorption at 1700 cm -1.
This was based on the generation of absorption attributable to the carbonyl of succinimide near ^-1 or 1770 cm ^-1 . In addition, by reacting ethyl alcohol at 100°C with modified low molecular weight polyisoprene rubber (LIR-B) to which succinic anhydride residues have been added, modified low molecular weight polyisoprene rubber (LIR-B) to which monomethyl succinate residues have been added is produced. (abbreviated as LIR-C in Table 1) was obtained. Using each of the above-mentioned four (modified) low molecular weight polyisoprene rubbers, a natural rubber composition was prepared using a Banbury mixer according to the formulation shown in Table 1,
The plasticizing effect and vulcanization accelerating effect of various low molecular weight polyisoprene rubbers and the vulcanized physical properties of the rubber compositions were evaluated. The plasticizing effect is measured by the viscosity at 100℃ measured with a Mooney viscometer (for the test method, refer to "Rubber Test Methods" published by the Japan Rubber Association in 1981).
(see page 140), the vulcanization accelerating effect is the vulcanization rate at 145°C, which is the time T ₉₀ required to reach a degree of vulcanization of 90% as measured by a JSR culastometer.
(For the test method, refer to "Rubber Test Method" 213 above.
(see page), and the vulcanized physical properties were evaluated according to JISK-6301.

[Table] As is clear from Table 1, N-
Only when a modified low molecular weight polyisoprene rubber containing (γ-dimethylamino)propyl succinimide residues is used, an extremely large plasticizing effect can be achieved.
A remarkable effect of accelerating vulcanization and improvement of the properties of vulcanized materials are simultaneously achieved. Example 2 A butadiene polymerization block (abbreviated as B) and an isoprene polymerization block (abbreviated as I) were synthesized into B-I by polymerizing butadiene monomer and isoprene monomer using butyllithium as a catalyst.
A low molecular weight butadiene-isoprene block copolymer rubber (abbreviated as LBIR-A) connected in the form -B-I-B-I-B was prepared. The rubber is
The molecular weight is 18000, the vinyl bond is 18%,
The proportion of I in the rubber was 40%. This rubber was obtained by heating and reacting maleic anhydride at 180°C for 7 hours to obtain a modified low molecular weight copolymer rubber. When examined by infrared absorption spectrography, the modified low molecular weight copolymer rubber was found to be a modified low molecular weight butadiene-isoprene block copolymer containing 7.2 moles of succinic anhydride residues as side chains per 100 monomer units in the rubber. It was a polymeric rubber (abbreviated as LBIR-B). After reacting the rubber with N,N-diethylaminopropylaminopropylamine at 100°C, the rubber was reacted under reduced pressure.
Dehydration was performed by heating at 160°C. The thus obtained modified low molecular weight butadiene-isoprene block copolymer rubber was examined by infrared absorption spectrography and was found to be a modified copolymer rubber in which N-(γ-diethylamino)propyl succinimide residues are present in the side chain. (LBIR-C). Using each of the above two types of modified low molecular weight butadiene-isoprene block copolymers, a rubber composition was prepared in the same manner as in Example 1 according to the formulations shown in Table 2, and the rubber composition had a plasticizing effect, a vulcanization accelerating effect and The effect of improving vulcanized physical properties was evaluated. The results are shown in Table 2.

[Table] Modified low molecular weight butadiene-isoprene copolymer rubber containing N-(γ-diethylamino)propyl succinimide derivative residues in the side chain is added to natural rubber.
A large plasticizing effect, vulcanization acceleration effect, and improvement effect on the vulcanizate were observed by adding 10%. Furthermore, if a forehead-modified low molecular weight copolymer rubber is used, even if the vulcanization accelerator is reduced by 40%, the vulcanization rate will still be higher than that of the control example, which contains natural rubber alone, and the hardness of the vulcanizate will also be higher. Example 3 N,N-dimethyl was added to a low molecular weight polyisoprene rubber (LIR-E) with a vinyl bond content of 12% and a molecular weight of 40,000 obtained by polymerizing isoprene monomer using butyllithium as a catalyst. Two types of modified low molecular weight polyisoprene rubbers were prepared by heating and reacting aminopropylmaleimide and N-propylmaleimide at 190°C.
The product reacted with N,N-dimethylaminopropylmaleimide was found to contain 2.7 moles of N-(γ-dimethylamino)propyl succinimide residue per 100 isoprene monomer units in the rubber as an example chain, as determined by infrared absorption spectroscopy. It was found to be a modified low molecular weight polyisoprene rubber (LIR-F). Note that this infrared absorption spectrum graph was almost the same as that of LIR-D of Example 1. On the other hand, those reacted with N-propyl maleimide have N-propyl succinimide residues as side chains at a rate of 2.9 per 100 isoprene monomer units in the rubber.
It was found to be a modified low molecular weight polyisoprene rubber (LIR-G) containing mol. Using each of the three types of low molecular weight polyisoprene rubbers mentioned above, rubber compositions were prepared according to the formulations shown in Table 3, and the effects of using the low molecular weight polyisoprene rubbers were investigated. The results are shown in Table 3.

【table】

[Table] Example 4 Pyrolysis of cis-1,4-polyisoprene rubber with a molecular weight of 840,000 and a cis-1,4 bond content of 98% obtained by polymerizing isoprene monomer using a Ziegler catalyst. molecular weight 53000,
A low molecular weight polyisoprene rubber having a vinyl bond content of 9% was prepared. Using this rubber, a modification reaction was carried out in the same manner as in Example 1 to prepare a modified low molecular weight polyisoprene rubber. According to infrared absorption spectrography, the modified rubber has N-(γ
The rubber was found to be a modified low molecular weight polyisoprene rubber containing 5.8 moles of -dimethylamino)propyl succinimide residue per 100 isoprene monomer units in the rubber. Using the obtained modified rubber, rubber compositions were prepared according to the formulations shown in Table 4 without containing the vulcanization accelerator.

【table】

[Table] These rubber compositions were vulcanized at 155°C for 20 minutes.
A rubber composition using a modified low molecular weight polyisoprene rubber containing N-(γ-dimethylamino)propyl succinimide residue as a side chain is as follows:
Sufficient degree of vulcanization was achieved, with a tensile strength of 242 kg/
cm ² and elongation of 600%, a rubber composition consisting only of natural rubber as a rubber component was extremely insufficiently vulcanized under the above vulcanization conditions, and a satisfactory vulcanization was not achieved. No sulfur properties were obtained.

Claims (1)

[Claims] 1. In a solid rubber composition containing a plasticizer,
The plasticizer is a low molecular weight diene rubber with a molecular weight of 6,000 to 100,000 and a vinyl bond content of 35% or less, and the side chain of the rubber has the general formula () (Here, R represents a hydrocarbon residue having up to 20 carbon atoms in which an oxygen atom or a sulfur atom may be interposed in the main chain, and A is [Formula] (R ¹ or R ² each has up to 20 carbon atoms. (represents a hydrocarbon residue) or a heterocyclic residue containing a tertiary nitrogen atom as a heteroatom) containing a group having a tertiary amino group at the N-position A rubber composition characterized in that a modified low molecular weight rubber containing 0.1 to 20 moles of succinimide derivative residue per 100 monomer units in the rubber is used.