JPH0461001B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a rubber material for vulcanization by modifying cis-1,4-polyisoprene rubber, and more specifically, to cis-1,4-polyisoprene rubber, adding a tertiary amino group-containing hydrocarbon to cis-1,4-polyisoprene rubber. The present invention relates to a method for producing a rubber material for vulcanization by adding a succinimide group having a group at the N-position as a side chain. Synthetic cis-1,4-polyisoprene rubber (hereinafter abbreviated as IR) has the same molecular structure as natural rubber (hereinafter abbreviated as NR), and is the most NR-friendly among various synthetic rubbers. It has similar properties and exhibits excellent processability and vulcanizate physical properties, and is used as a substitute for NR in various fields such as automobile tires, rubber industrial products, and rubber footwear as one of the representative general-purpose synthetic rubbers. . Furthermore, since IR is a synthetic product, there are far fewer contaminants such as impurities and foreign substances than NR, making it possible to reduce problems such as defective products due to these. It is used for awards. However, IR has the disadvantage that its green strength is considerably inferior to that of NR, and for example, it may cause cold flow during storage, or various problems such as those mentioned when manufacturing rubber products. . That is, when the unvulcanized fabrics of various parts of the tire are pasted together to form the unvulcanized fabric, the unvulcanized fabric may sag or denature, and the arrangement of the tire cords embedded in the unvulcanized fabric may become disordered. This is like saying that uniform tires cannot be obtained. However, on the other hand,
The low green strength of IR also leads to its good fluidity, so IR is often blended with NR even at the cost of lower green strength. That is the reality. In other words, as tires have become more radial in recent years, the hardness and modulus of each part of the tire have been increasing. This means that sexuality is declining. Therefore, if NR is used alone in such cases, the fluidity will be poor and the process will be carried out at a temperature of, for example, 80 to 150°C.
The skin may not be smooth during calendering, extrusion molding, press vulcanization, etc.
This often causes various problems such as the engraving pattern not being clearly visible. For these reasons, ideally near room temperature
There is a demand for a rubber material for vulcanization that has high green strength like NR, exhibits excellent fluidity that is characteristic of IR at relatively high temperatures, and has excellent physical properties of vulcanizates. Conventionally, various attempts have been made to improve the green strength of the above-mentioned drawbacks of IR, and a typical example is a method of adding maleic anhydride to IR. This method is considered to be one of the most effective methods because the reaction is relatively easy and the resulting modified IR is highly economical. However, the unvulcanized strength of modified IR obtained by adding maleic anhydride is NR
However, it cannot be said that the fluidity during high-temperature processing is as excellent as that of IR, and the effect of improving the physical properties of the vulcanizate was not sufficient. In contrast, IR has been proposed as a method to improve green strength without deteriorating the physical properties of vulcanizates.
For synthetic rubber such as

[Formula] Also teeth

Maleamic acid or maleamide derivatives represented by the formula: (wherein R represents a hydrogen atom, an alkyl group, a phenyl group, a chlorphenyl group, a nitrophenyl group, a benzyl group, a formylaminophenyl group, or a cyclohexyl group), or maleamic acid The method of blending hydrazide was published in JP-A-Sho.
According to Example 1, the green strength at room temperature is improved, and the strength and elongation of the vulcanized product is also improved. The breaking strength of sulfur is
It is too strong (at least 1.6 times IR, the same level as NR, but higher), indicating that there are problems with fluidity and processability at high temperatures. In addition, as a similar method, it is known from JP-A-51-45198 to mix an alcohol, an amine, or an amine such as polyethyleneimine having three or more amine groups with a modified IR to which maleic anhydride has been added. However, although the method using alcohol amines improves green strength,
It does not have a high value as in the case of NR, and the breaking strength and hardness when made into a vulcanized product do not have as high values as in the case of NR. In addition, the method using polyethyleneimine had problems with fluidity during high-temperature processing (that is, the breaking strength at high temperatures was not as small as that of IR), and both problems were recognized. As described above, none of the conventional modified IRs has been able to satisfy all aspects of green strength, fluidity at high temperatures, processability, and the breaking strength and hardness of vulcanizates. Furthermore, in these conventional modification methods, even when the physical properties of the vulcanizate, such as breaking strength and hardness, are improved, there is an unavoidable tendency for the tear strength to generally decrease. The present invention aims to improve the drawbacks of the above-mentioned IR and modified IR, and its main purpose is to provide an unvulcanized material with excellent physical properties in both green strength near room temperature and fluidity during high temperature processing, and The object of the present invention is to provide a method for producing a rubber material for vulcanization, which exhibits high breaking strength and hardness comparable to or higher than NR in terms of physical properties of the vulcanizate, and which does not suffer from the conventional decrease in tear strength. According to the invention, the above-mentioned object is achieved by
A compound selected from the group consisting of () maleic anhydride, maleic acid, maleic acid monoester, and maleic acid diester is added to 1,4-polyisoprene rubber to form an isoprene monomer unit in the rubber.
After adding 0.01 to 10 moles per 100, the general formula () H ₂ N-R ¹ -A (where R ¹ is a carbon number up to 20 in which an oxygen atom or a sulfur atom may be interposed in the main chain) is added. represents a hydrocarbon residue, A has 20 carbon atoms
(representing a dihydrocarbylamino residue up to or a heterocyclic residue having up to 20 carbon atoms containing at least one tertiary nitrogen atom as a heteronitrogen atom), and then dehydration or dealcoholize or () general formula () (Here, R ¹ and A are as defined above.) This is achieved by adding 0.01 to 10 moles of a maleimide derivative represented by the formula (wherein R 1 and A are as defined above) per 100 isoprene monomer units in the rubber. Surprisingly, when the rubber material for vulcanization obtained by this method is vulcanized, its vulcanization rate is as fast as or faster than that of NR. The synthetic cis-1,4-polyisoprene rubber used in the present invention is a solid material with a cis-1,4 bond content of 80% or more obtained by polymerizing isoprene monomer using a Ziegler catalyst or an anionic catalyst. Rubber, and if the physical properties etc. are comprehensively evaluated, it is more preferable to use so-called high-cis-1,4-polyisoprene rubber, which has a cis-1,4-bond content of 95% or more and is obtained using a Ziegler catalyst. It will be done. Further, the molecular weight is not necessarily limited as long as the rubber remains solid, but if the range is specified, it is 200,000 to 2,000,000. In the general formula ()H ₂ NR ¹ -A representing the amine used in the method () of the present invention,
Examples of R ¹ include the following: (a) Alkylene residue with up to 20 carbon atoms which may be branched, (b) cycloalkylene residue with up to 20 carbon atoms, (c) General formula −(R ³ −Z) _o −R ⁴ − (here So, R ³ and
R ⁴ is the same or different group selected from the group consisting of an ethylene group, a lower alkyl-substituted ethylene group, and a proprene group, Z is oxygen or sulfur, and n is an integer of 1 or more. (d) an aromatic hydrocarbon residue having up to 20 carbon atoms selected from the group consisting of arylenealkaarylene groups and aralkarylene groups; (e) aryloxyarylene groups; heteroatom-containing aromatic hydrocarbon residues containing up to 20 carbon atoms, such as (oxygen, sulfur). Further, as A, general formulas such as () dialkylamino residue having up to 20 carbon atoms, () diarylamino residue having up to 20 carbon atoms, () dialkylamino residue having up to 20 carbon atoms, etc.

A dihydrocarbyl residue represented by the formula (R is a hydrocarbon residue), or a 5- or 6-membered heterocyclic residue containing at least one tertiary nitrogen atom as a heteronitrogen atom, etc. The following groups are mentioned. Note that R ¹ and A preferably have 20 or less carbon atoms, particularly 2 to 12 carbon atoms, in consideration of economic efficiency. Typical examples of such amines include (dialkylamino)alkylamines, (N,N-dialkylaminoalkoxy)alkylamines, amines in which the alkadiyloxy moiety of the amine has become poly(alkanediyloxy), p -N,N-dialkylaminomethylbenzylamine, p-N,
Examples include N-dialkylaminophenylamine, N-aminoalkylpiperidine, N-aminoalkylpipecoline, N-aminoalkylmorpholine, 1-aminoalkyl-4-alkylpiperazine, aminoalkylpyridine, picolylamine, and the like. In addition, in the above-mentioned (dialkylamino)alkylamine, the hydrogen of the alkylene residue present between the nitrogens may be substituted with a (dialkylamino)alkyl residue. Among these, (dimethylamino)ethylamine, (diethylamino)ethylamine, (dipropylamino)ethylamine, (dimethylamino)
(dialkylamino)alkylamines such as propylamine, (diethylamino)propylamine, (dimethylamino)butylamine, (diethylamino)butylamine, (dimethylamino)hexylamine or (dimethylamino)decylamine;
(N,N-dimethylamino)ethoxyethylamine, (N,N-dimethylamino)ethoxypropylamine, and even α-(3-aminopropyl)-
ω-(3-dimethylaminopropyl)oxy-poly(oxy-1,2-ethanediyl) ( (N,N-alkylamino)alkoxyalkylamines such as (n is an integer from 1 to 7) 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. In addition, the maleimide derivative used in the method () above has the general formula ()

It is a maleimide containing a hydrocarbon residue having a tertiary nitrogen atom at the N-position represented by the formula: R ¹ and A are as described above, and a particularly preferably used maleimide derivative is N-
(β-dimethylamino)ethylmaleimide, N-
(β-diethylamino)ethylmaleimide, N-
(γ-dimethylamino)propylmaleimide, N
-(γ-diethylamino)propylmaleimide,
N-(δ-dimethylamino)butylmaleimide,
Examples include N-(dialkylamino)alkylmaleimides such as N-(δ-diethylamino)butylmaleimide. Reaction of adding maleic anhydride, maleic acid, maleic acid monoester, maleic acid diester to IR [method of ()], and reaction of adding a maleimide derivative represented by general formula () to IR [method of ()] is carried out in solution or in the solid state. For reaction in a solution state (solution reaction), IR is dissolved in a solvent such as an aliphatic, alicyclic or aromatic hydrocarbon, the above maleic acid derivative is added, and a radical generating agent such as a peroxide or an azo compound is added. This is done by heating in the presence or absence of the reaction. Although reaction conditions are not particularly limited, the temperature is usually 25 to 250°C, preferably 50 to 250°C.
It is carried out at 200°C for 0.1 minute to 100 hours, preferably 0.5 to 30 hours. The reaction in the solid state is carried out by kneading IR and the maleic acid derivative using a roll mill, kneader, Banbury mixer, screw extruder, or the like. Usually, there is no need to use a catalyst such as a peroxide or an azo compound, but in some cases the reaction may be carried out using a catalyst. Reaction conditions are not particularly limited even in the solid state, and usually temperature
The treatment is carried out at 25 to 300°C, preferably 50 to 250°C, for 0.1 minute to 100 hours, preferably 0.5 minutes to 30 hours. When a maleic acid derivative obtained by adding maleic anhydride, maleic acid, maleic acid monoester, or maleic acid diester to IR is reacted with an amine represented by the general formula (), the amine is added to 1 mole of the maleic acid derivative. It is necessary to use 1 mol or more. The reaction temperature generally adopted in this amine reaction is 0 to 150℃.
and the reaction time is 0.1 minute to 20 hours. In this reaction, acid anhydride groups and carboxyl groups are first amidated, and then imidized by dehydration or dealcoholization. If this amine reaction is incomplete, monomaleamide carboxylic acid may partially remain. If the amount is small, there is no problem, but if the amount is large, the properties of the resulting rubber material for vulcanization may be impaired. It is better to perform the following processing. In the present invention, maleic anhydride for IR,
For maleic acid, maleic acid monoester, and maleic acid diester, the amount of the maleimide derivative represented by the general formula () added is important; if it is too small, almost no IR modification effect can be expected; on the other hand, if it is too large, The strength of the unvulcanized product becomes too high, which actually impairs workability at high temperatures. Therefore, the addition amount is 0.01 per 100 isoprene monomer units in the IR.
~10 mol, especially 0.01~2
It is preferably between 0.05 and 1.0 mol, especially between 0.05 and 1.0 mol. The rubber material for vulcanization obtained by the present invention not only has excellent strength of the unvulcanized product and processability of the unvulcanized product at high temperatures, but also has excellent vulcanization speed and physical properties of the vulcanized product. Therefore, it can be applied not only to fields where IR has traditionally been used, but also to other fields.
It can also be applied to other uses. In such applications, compounded chemicals used in the manufacture of rubber products are used. Examples include carbon black (soft carbon black, hard carbon black), white carbon, reinforcing agents such as calcium carbonate, fillers, vulcanizing agents such as sulfur and peroxide, and vulcanizing aids such as zinc oxide and stearic acid. Agents, vulcanization accelerators, anti-aging agents, softeners such as oils, and resins such as rosin resins, terpene resins, phenolic resins, epoxy resins, and polyester resins.
Further, as a rubber component, it is also possible to use natural rubber, untreated IR, synthetic rubber such as styrene-butadiene copolymer rubber, polybutadiene rubber, and optionally mixed with liquid polyisoprene, polybutadiene, etc. Note that when the vulcanized rubber material obtained by the present invention is mixed with unmodified IR, both should be mixed in a ratio of 5/95 to 95/5 (weight ratio) and vulcanized in the mixture. It is important to mix so that the amount of imide rings in the rubber material for sulfurization is 0.01 to 10 mol%. Suitable uses for the vulcanized rubber material obtained by the present invention include various parts of automobile tires such as treads, carcass, beads, beat fillers, and rim strips, conveyor belts, V-belts, hoses, anti-vibration materials, and rubber rolls. Examples include supplies, rubberized cloth, rubber shoes, rubber thread, rubber bands, sponge rubber, etc. 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. In addition, the evaluation method of the rubber in the examples was performed according to JIS K-6301. In addition, "part" and "%" in the examples indicate weight basis. Example 1 A synthetic cis-1,4-polyisoprene rubber IR with a cis-1,4 bond content of 98% and a molecular weight of 840,000 (IR using a Ziegler catalyst, trade name Kuraprene IR-10 manufactured by Clarei Soprene Chemical Co., Ltd.) was used. Dissolved in toluene to make a 10% IR solution. Maleic anhydride was added to the solution in an amount of 2.5 parts per 100 parts of IR, and heated at 180°C for 5 hours to obtain a modified IR solution to which maleic anhydride had been added. Modified IR was collected from the solution, purified, and the reaction rate of maleic anhydride was determined to be 12%. Using an infrared spectrophotometer (FTS-20% Fourier transform infrared spectrometer manufactured by Digilab), the modified IR obtained in this way was measured using total reflection spectroscopy (20 integrations at an incident angle of 70°). A spectrum graph shown in Figure 2 was obtained. Incidentally, a spectrum graph of unmodified IR is shown in FIG. As is clear from Figures 1 and 2, due to the addition of maleic anhydride, peaks derived from the carbonyl of the acid anhydride group were observed at 1790 cm ^-1 and 1870 cm ^-1 , indicating that a maleic anhydride adduct was produced. It turned out that there was. The amount of added maleic anhydride was determined from the absorption at 1790 cm ^-1 and 1870 cm ^-1 and was found to be 0.21 per 100 isoprene monomer units in IR.
It was mole. Prepare a 10% toluene solution of the maleic anhydride addition IR, heat it to 100°C, and add (dimethylamino)
Maleic anhydride addition of propylamine IR100
After stirring for 30 minutes, the temperature was raised again and further heated at 180°C for 3 hours. After cooling, the reaction product was poured into methanol, and the product was collected and dried under vacuum. Looking at the infrared absorption spectrum graph (Figure 3) of the above product, the absorption attributed to the carbonyl of the acid anhydride group around 1790 and 1870 cm ^-1 observed in the maleic anhydride addition IR disappeared, and a new
Absorption attributable to the carbonyl of maleimide appears near 1700 and 1770 cm ^-1 , and the maleic anhydride residue added to the IR has changed to an N-(γ-diethylamino)propylmaleimide residue, and the N
It was confirmed that a modified IR to which -(γ-dimethylamino)propylmaleimide was added (addition amount: 0.21 mol) was obtained. On the other hand, for comparison, instead of reacting (dimethylamino)propylamine with modified IR to which maleic anhydride was added, ethanolamine, di-n-propylamine, ethylenediamine, molecular weight
1200 polyethyleneimine (Nippon Shokubai Chemical Co., Ltd.)
PEI SP-012 (trade name) and N,N'-diphenyl-p-phenylenediamine (trade name antigen P, manufactured by Sumitomo Chemical Co., Ltd.) were each used in equimolar numbers with the (dimethylamino)propylamine. Various modified IRs were obtained in the same manner. Using the obtained denatured IR, undenatured IR, and NR, the first
A rubber compound was obtained by kneading according to the formulation shown in the table. Further, the rubber compound was press-vulcanized at 145° C. for 30 minutes to obtain a rubber vulcanizate. For the unvulcanized rubber compound thus obtained, a thickness of 2
A strip-shaped sheet with a width of 6 mm and a width of 6 mm was pulled at a tensile speed of 50 mm/min using an Instron tensile tester.
The yield value, stress at 300% elongation (hereinafter abbreviated as M300), breaking strength, and breaking elongation were measured at 25°C and 100°C. The M300, breaking strength, and breaking elongation of the vulcanizate were also measured at 25°C in the same manner as for the rubber compound. Hardness and tear strength were also measured. The results are shown in Table 2. Table 1 Rubber 100 parts HAF carbon black 45 Zinc white 5 Stearic acid 3 Sulfur 2 Vulcanization accelerator ¹⁾ 1 Anti-aging agent ²⁾ 1 1 N-oxydiethylene-2-benzothiazolylsulfenamide, large Manufactured by Uchishin Kagaku Kogyo Co., Ltd.
Product name: Noxela MAS 2 Poly(2,2,4-trimethyl-1,2-dihydroquinoline) Manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Product name: Noxelaku 224

【table】

[Table] As is clear from Table 2, N-
Modified IR to which (γ-dimethylamino)propylmaleimide has been added has improved breaking strength (i.e., green strength) at 25°C to that of NR, and its breaking strength at high temperatures is as small as that of IR, resulting in good fluidity. (This leads to good workability at high temperatures, as described in Example 3 below), and the hardness of the vulcanizate is also improved, and its breaking strength and elongation are comparable to NR. On the other hand, when ethanolamine is used as a modifier, the effect of improving the breaking strength at 25°C is small, and the breaking strength and hardness of the vulcanizate are reduced. Furthermore, when di-n-propylamine, ethylenediamine, polyethyleneimine, or N,N'-diphenyl-p-phelenediamine is used, the breaking strength at 100°C is significantly higher than the NR level, resulting in poor fluidity at high temperatures. In addition, the stress and hardness of the vulcanizate at 300% elongation also decrease. Example 2 N-(γ-
A modified IR with addition of dimethylamino)propylmaleimide was obtained. The amount added was 1.41 mol. On the other hand, for comparison, Example 1 was used except that monomethyl maleate was used instead of maleic anhydride.
Modified IR with monomethyl maleate was obtained using the same method as above. The amount added is 0.51 mol. Using the above two types of modified IR, IR and NR, an unvulcanized rubber compound having a Mooney viscosity of about 80 was prepared by the blending in Example 1, and then by the same method as in Example 1 at 25°C and 100°C. The stress-strain behavior at ℃ was investigated. FIG. 4 is a stress-strain curve at 25°C, and FIG. 5 is a stress-strain curve at 100°C. Note that the horizontal axis represents strain and the vertical axis represents stress. In FIGS. 4 and 5, A is N-(γ-
Modified IR with addition of dimethylamino)propylmaleimide (Mooney viscosity 78), B is modified IR with addition of monomethyl maleate (Mooney viscosity 79), NR
is natural rubber (Mooney viscosity 81), IR is synthetic cis-1,4-polyisoprene rubber (Mooney viscosity
80) are shown for stress-strain curves of unvulcanized rubber compounds using each of them. As is clear from FIGS. 4 and 5, N-(γ
Only the modified IR with -dimethylamino)propylmaleimide has high green strength at low temperatures (25°C) and the lowest yield stress and breaking strength at high temperatures (100°C). In particular, the latter fact indicates good workability at high temperatures. on the other hand,
25 for modified IR with addition of monomethyl maleate
Although the green strength at ℃ is improved, the yield stress at high temperatures is much higher than that of NR, which has processability problems, indicating extremely poor flowability at high temperatures. Example 3 100 parts of IR with a molecular weight of 570,000 prepared by masticating the IR (IR-10) used in Example 1 was dissolved in toluene, 3 parts of maleic anhydride was added, and the mixture was heated at 180°C.
It reacted for 10 hours. The obtained modified IR contained 0.3 mole of maleic anhydride as calculated from an infrared absorption spectrograph. Modifiers (g) ω-(N,N-dimethylamino)decylamine, (h) dimethylaminoethoxyethylamine, and (i) bis(γ,γ-dioctylamino)ethylpropylamine were each added to the obtained modified IR. An excess amount of the added maleic anhydride was added, and the mixture was reacted at 160° C. for 3 hours under reduced pressure. When we took an infrared absorption spectrum, we found that the absorptions attributed to the carbonyls of acid anhydride groups (absorptions at 1790cm ^-1 and 1870cm ^-1 ) disappeared, and the absorptions attributed to the carbonyls of maleimide (1700cm ^-1 and 1770cm ^-1 ) disappeared. ¹ absorption) was newly recognized. From this, when (g) is used, modification with N-(dimethylamino)decylmaleimide added
When IR is used (h), modified IR with N-(dimethylaminoethoxy)ethylmaleimide added
However, it was found that when (i) was used, modified IRs to which N-(bis(γ,γ-dioctylamino)ethyl)propylmaleimide was added were obtained. Three types of denatured IR and undenatured IR obtained in this way
The physical properties of the unvulcanized material at 25°C, the physical properties of the unvulcanized material at 100°C, and 25
The physical properties of the vulcanizate at °C were investigated. In addition, the compound was subjected to an extrusion test using a Brabender type test extruder, and those whose extrusion amount per unit time was equivalent to that of unmodified IR were evaluated as "good".
Those that showed performance comparable to NR were rated as "bad." These results are also shown in Table 4. Table 3 Compound Rubber 100 parts HAF carbon black 45 Zinc white 3 Stearic acid 1 Sulfur 2 Vulcanization accelerator 1 Anti-aging agent 1

【table】

【table】 /

_CH2 - _CH2 -N

\


(CH ₂ ) ₇ CH ₃
As is clear from Table 4, when modifying agents (g), (h), and (i) are further applied to the modified IR to which maleic anhydride has been added, the strength of the unvulcanized product at 25°C increases again at 25°C. ℃
The strength and hardness of the vulcanized product at 100°C are improved to the same level as NR, and the strength of the unvulcanized product at 100°C is as low as that of IR. Also, the extrusion characteristics are comparable to IR.
In addition, the extrusion characteristics at 100°C and the strength of the unvulcanized product at 100°C were also investigated in Example 1, and it was found that the strength of the unvulcanized product at 100°C was comparable to that of IR, and the extrusion properties were as good as that of IR. Characteristics, but 100
The unvulcanized material strength at ℃ is NR level.
It was found that the extrusion properties were only comparable to NR.
It was confirmed that the strength of the unvulcanized product at 100°C has a nearly parallel relationship with the extrusion properties at 100°C. Example 4 Synthetic cis-1,4-polyisoprene rubber IR with a good 98% of cis-1,4 bonds and a molecular weight of 840,000 (IR using a Ziegler catalyst, trade name Kuraprene IR-10 manufactured by Clareisoprene Chemical Co., Ltd.) Addition reactions were carried out by adding varying amounts of N-(γ-diethylamino)propylmaleimide. The reaction was carried out by mixing with a Brabender plasticorder, first at 100°C for 2 minutes, then at 220°C.
This was done by kneading for 5 minutes. When the resulting modified IR was subjected to an infrared spectrophotometer and a spectrum graph was obtained, the result is shown in Figure 3.
Clear absorptions (absorptions attributable to the carbonyl of maleimide) were observed at positions of 1700 cm ^-1 and 1770 cm ^-1 . When measured using the infrared absorption spectrum graph, N-(γ-
The amount of diethylamino)propylmaleimide added was as shown in Table 5. On the other hand, for comparison, N-(γ-diethylamino)
Modified IRs were prepared by using maleic anhydride or maleimide in place of propylmaleimide, and the amounts added were as shown in Table 5.

[Table] Using various modified IR, unmodified IR, and NR in Table 3,
A rubber compound was obtained by kneading according to the formulation shown in Table 6. Furthermore, the unvulcanized rubber compound is added to 145
Press vulcanization was performed at ℃ for 30 minutes to obtain a rubber vulcanizate. Regarding the thus obtained unvulcanized rubber compound, the yield value at 25°C and 100°C, stress at 300% elongation (M ₃₀₀ ), breaking strength, and breaking elongation were measured in the same manner as in Example 1. . The vulcanizate was also measured for stress at 300% elongation (M ₃₀₀ ), breaking strength, and breaking elongation at 25° C. in the same manner as for the rubber compound. Hardness and tear strength were also measured.
The results are shown in Table 6.

【table】

[Table] As shown in Table 6, modification with addition of N-(γ-diethylamino)propylmaleimide
IR(j) to (m) (Blend Nos. 1 to 4) exhibit performance equivalent to or better than natural rubber in both the strength and elongation characteristics of the unvulcanized product and the strength and elongation property of the vulcanized product. In other words, the green strength near room temperature is significantly improved compared to unmodified IR, and the breaking strength at high temperatures (100°C) is kept low, so it exhibits fluidity with a relatively small load. It was found that the processability was excellent, and the hardness and tear strength of the vulcanizate were also improved compared to conventional adducts of maleic anhydride and maleimide. On the other hand, the conventional method of adding maleic anhydride or maleimide improves green strength near room temperature, but also increases strength at high temperatures.
It was found that the fluidity deteriorated, and it was found that favorable physical properties were not obtained as a whole. Example 5 Synthetic cis-1,4-polyisoprene rubber IR (trade name: Kuraprene IR, manufactured by Clareisoprene Chemical Co., Ltd.)
-10) was dissolved in toluene to prepare a 10% IR solution. Next, N-(γ-dimethylamino)propylmaleimide was added to the solution, and the seventh
Added amount of N-(γ-dimethylamino) shown in the table
Propylmaleimide addition modified IR was obtained. said denaturation
When the amount of gel produced by IR was measured, the results shown in Table 7 were obtained. For the amount of gel, accurately weigh approximately 1 g of rubber, dissolve it in approximately 150 c.c. of toluene by shaking at room temperature for 12 hours, and then filter the insoluble matter through a 200-mesh wire mesh to separate the soluble and insoluble parts. After vacuum drying, it was weighed and calculated. On the other hand, for comparison, a modified IR with addition of maleic anhydride was prepared in the same manner as in the above method except that maleic anhydride was used instead of N-(γ-dimethylamino)propylmaleimide. The amount of maleic anhydride added and the amount of gel produced in the modified IR are shown in Table 7.

[Table] Using these modified IRs, rubber compounds were prepared according to the formulations in Table 6, and then vulcanized in the same manner as in Example 1. When the physical properties of these unvulcanized rubber compounds and vulcanized products were measured in the same manner as in Example 1, the results shown in Table 8 were obtained.

[Table] As shown in Table 8, N-(γ-
Modified IR(q) and (r) (Formulations No. 9 and 10) with addition of dimethylamino)propylmaleimide are IR
Modified IR(s) and (t) with maleic anhydride added to
Compared to (Blend No. 11 and 12), it is superior in the fluidity of the unvulcanized product at high temperatures, the hardness of the vulcanized product, and the tear strength. Example 6 Synthetic cis-1,4-polyisoprene rubber (IR
-10) 50 parts were dissolved in 405 parts of toluene, then 15 parts of maleic anhydride was added per 100 parts of the rubber, and the mixture was reacted at 180°C for 7 hours to obtain a modified IR. The amount of maleic anhydride added was 2.4 mol per 100 isoprene monomer units in the rubber. Next, dimethylaminopropylamine was added in an amount twice the molar amount of maleic anhydride introduced and reacted at 140° C. for 2 hours to obtain a modified IR containing 2.4 moles of N-(dimethylamino)propylmaleimide. Using the modified cis-1,4-polyisoprene rubber thus obtained, a rubber composition was prepared according to the formulation shown in Table 1, and the physical properties of the unvulcanized product and the vulcanized product were prepared in the same manner as in Example 1. and the vulcanization rate at 145°C. The results are shown in Table 9.

[Table] As is clear from Table 9, the modified IR obtained in this example exhibits values higher than NR in unvulcanized breaking strength at room temperature, modulus of vulcanized product, and hardness of vulcanized product.

[Brief explanation of the drawing]

Figures 1, 2 and 3 were used in Example 1, respectively.
IR, modified IR with maleic anhydride added, and modified IR with N-(γ-dimethylamino)propylmaleimide obtained by adding (dimethylamino)propylamine to the modified IR
It is an infrared absorption spectrum graph of IR. Fourth
Figures 5 and 5 show the N-
FIG. 2 shows stress-strain curves at 25° C. and 100° C. of an unvulcanized rubber compound containing modified IR to which (γ-dimethylamino)propylmaleimide is added as a rubber component. FIG. The stress-strain curves of NR, IR, and modified IR with only monomethyl maleate added are also shown. In the figure, A is a modified IR with N(γ-dimethylamino)propylmaleimide added;
B is modified IR with monomethyl maleate added;
N means the curve when using natural rubber, and I means the curve when using IR (unmodified).

Claims (1)

[Claims] 1. Synthetic cis-1,4-polyisoprene rubber,
() After adding 0.01 to 10 mol of a compound selected from the group consisting of maleic anhydride, maleic acid, maleic acid monoester, and maleic acid diester per 100 isoprene monomer units in the rubber, the general formula () H ₂ N−R ¹ −A (where,
R ¹ represents a hydrocarbon residue having up to 20 carbon atoms which may have an oxygen atom or a sulfur atom interposed in the main chain, and A represents a dihydrocarbylamino residue having up to 20 carbon atoms or a heteronitrogen atom. represents a heterocyclic residue containing at least one tertiary nitrogen atom and having up to 20 carbon atoms) and then dehydration or dealcoholization, or A rubber material for vulcanization, characterized in that 0.01 to 10 mol of a maleimide derivative represented by R ¹ and A are as defined above is added per 100 isoprene monomer units in the rubber. manufacturing method.