JPH07258473A - Production of vulcanized rubber having excellent hardness and dynamic elastic modulus - Google Patents

Abstract

PURPOSE:To obtain vulcanized rubber having excellent scorch resistance free from reduction in rubber strength by blending raw material rubber such as natural rubber with carbon black and a specific flavan-based compound in a high-temperature kneading process and vulcanizing in the presence of a vulcanizing agent. CONSTITUTION:(A) Raw material rubber selected from among natural rubber, styrene-butadiene copolymer rubber, butadiene rubber, isoprene rubber, acrylonitrile-butadiene copolymer rubber, chloroprene rubber, butyl rubber and halogenated butyl rubber is blended with (B) carbon black and (C) a flavan-based compound of the formula (R<1> to R<5> each is H, a 1-6C aliphatic group and in the case of R<1>, R<2>, R<4> and R<5> each is a chained aliphatic group, R<1> may be bonded to R<2> and R<4> may be boned to R<5> to form rings, respectively; X and Y each is OH or a 1-18C aliphatic group) (preferably 2,4,4-trimethyl-2',4'-7- trihydroxyflavan) in a high-temperature kneading process and then vulcanized in the presence of a vulcanizing agent to give the objective rubber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a vulcanized rubber, and more specifically, by adding a specific compound at a specific stage, it is possible to improve hardness and dynamic elastic modulus. The present invention relates to a method for producing a vulcanized rubber and a tire produced by the method.

[0002]

2. Description of the Related Art In rubber products such as tires, hoses and rubber belts, it is often required to improve the hardness and dynamic elastic modulus of vulcanized rubber. For example, of the rubber material for tires, in the tread portion and undertread portion that make a large contribution to rolling resistance, heat generation (hysteresis loss) of rubber due to periodic (dynamic) deformation during tire rolling.
It is an important issue to reduce fuel consumption from the viewpoint of reducing fuel consumption. In addition, in the coating rubber used for the carcass part and the bead part, since the coating rubber is prevented from being broken (separation) due to cyclic (dynamic) deformation during tire rolling and the separation promotion due to hysteresis loss is suppressed, the heat generation property is reduced. There is a demand for a rubber material that is low and has low destructiveness. Such hysteresis loss and breaking strength largely depend on the hardness and dynamic elastic modulus of rubber, and in order to improve these physical properties, it is required to increase the hardness and dynamic elastic modulus of rubber. There is.

Conventionally, a method of increasing the amount of a reinforcing agent such as carbon black and a method of increasing the amount of sulfur or a vulcanization accelerator to increase the vulcanized state in order to increase the hardness and dynamic elastic modulus of rubber. It has been known. However, all of these methods have disadvantages that are not desirable.
In other words, the increase of carbon black is
This is not preferable because it causes an increase in loss, causes a problem of increasing heat generation, reduces the fracture strength such as blowout resistance and cut growth resistance, and causes scorch. On the other hand, increasing the amount of sulfur or the like has a problem that the flex cracking resistance and the heat aging resistance are significantly reduced. For these reasons, it is difficult to further improve the hardness and dynamic elastic modulus of the vulcanized rubber by simply increasing the amount of the reinforcing agent, the vulcanizing agent, and the vulcanization accelerator.

Therefore, there is known a method of adding resorcin in order to achieve high hardness and high dynamic elastic modulus without sacrificing heat resistance and blowout resistance.
Resorcin improves the hardness and dynamic elastic modulus of the rubber, makes the rubber tough (tough), reduces the loss coefficient during dynamic deformation of the vulcanized rubber, and is also effective in improving heat resistance. Therefore, it has been widely used in the past. However, resorcin has been a major social problem because it sublimes significantly during rubber processing such as kneading and is not preferable in terms of environmental hygiene. Further, in unvulcanized rubber containing resorcin, it also has processing defects such as resorcin blooming on the rubber surface to cause a decrease in adhesion between unvulcanized rubbers and scorch. It was Further, there is a problem that strength properties such as tensile properties of the vulcanized rubber are deteriorated as compared with the vulcanized rubber to which resorcin is not added. Therefore, improvement of these problems has been strongly demanded.

JP-A-58-147444 discloses 2, 4, 4
A rubber composition containing a compound capable of donating a methylene group when heated together with -trimethyl-2 ', 4', 7-trihydroxyflavan is disclosed. This rubber composition is intended for adhesion with a reinforcing material such as nylon, polyester or steel cord. In the examples, first, carbon black, sulfur and the like are added to the rubber and kneaded, and then the methylene acceptor is added. 2,4,4-trimethyl-2 ', 4', 7-trihydroxyflavan and methylene donor are added together with the vulcanization accelerator.

[0006]

DISCLOSURE OF THE INVENTION The present inventors do not have the problem of transpiration which resorcin has, and further
The present invention has been completed as a result of various studies in order to produce a vulcanized rubber that can obtain high hardness and high dynamic elastic modulus without sacrificing strength properties such as tensile properties.

Therefore, one of the objects of the present invention is to provide a method for producing a vulcanized rubber having a high hardness and a high dynamic elastic modulus.

Another object of the present invention is to compound a compound which does not show transpiration in a processing step such as rubber kneading so that the rubber strength such as tensile properties, tear resistance and flex crack resistance is hardly reduced, It is to provide a method for producing a vulcanized rubber having excellent scorch resistance.

A further object of the present invention is to provide a tire manufactured by such a method and having excellent hardness and dynamic elastic modulus.

Still another object of the present invention is to provide a method for improving the hardness and dynamic elastic modulus of a vulcanized rubber by compounding a specific compound into a rubber at a specific stage and then vulcanizing the compound. It is in.

[0011]

That is, the present invention is directed to a raw rubber selected from natural rubber, styrene-butadiene copolymer rubber, butadiene rubber, isoprene rubber, acrylonitrile-butadiene copolymer rubber, chloroprene rubber, butyl rubber and halogenated butyl rubber. , With carbon black, formula (I)

[0012]

(Wherein R ¹ , R ² , R ³ , R ⁴ and R
⁵ are each independently hydrogen or an aliphatic group having 1 to 6 carbon atoms, and when R ¹ , R ² , R ⁴ and R ⁵ are all chain aliphatic groups, R ¹ and R ² And R ⁴ and R ⁵ may combine to form a ring respectively; X
And Y are each independently hydrogen, a hydroxyl group, or an aliphatic group having 1 to 8 carbon atoms) are blended in a kneading step at high temperature, and then vulcanized in the presence of a vulcanizing agent. Provide a method for producing a vulcanized rubber.

The present invention also provides a tire manufactured by such a method, and further provides a method for improving the hardness and dynamic elastic modulus of a vulcanized rubber by adopting the steps as described above. .

The raw material rubber used in the present invention is selected from natural rubber, styrene-butadiene copolymer rubber, butadiene rubber, isoprene rubber, acrylonitrile-butadiene copolymer rubber, chloroprene rubber, butyl rubber and halogenated butyl rubber, each of which is a single rubber. Or a blend of two or more rubbers.

The flavan type compound compounded in the raw rubber is represented by the above formula (I). In the formula, R ¹ , R ² ,
R ³ , R ⁴ and R ⁵ are each independently hydrogen or an aliphatic group having 1 to 6 carbon atoms, and when R ¹ , R ² , R ⁴ and R ⁵ are all chain aliphatic groups Is R ¹ and R
² may combine, and R ⁴ and R ⁵ may combine to form a ring. The aliphatic group can usually be alkyl. When R ¹ and R ² are bonded to each other to form one of the condensed rings and when R ⁴ and R ⁵ are bonded to each other to form one of the spiro rings, the ring thus formed has, for example, 4 to 8 carbon atoms. It can be a cycloalkane ring to the extent, most commonly a cyclohexane ring. X and Y are each independently hydrogen, a hydroxyl group or 1 to 8 carbon atoms.
Is an aliphatic group. The aliphatic group in this case can also usually be alkyl.

Flavan compounds of formula (I) are disclosed in
It can be produced according to known methods described in JP-A 5-139375, JP-A-61-27980 and the like. For example, resorcin or a 4- and / or 5-substituted compound thereof and a ketone, α, β-unsaturated ketone, β-hydroxyketone, α, β-unsaturated aldehyde or β-hydroxyaldehyde are present in the presence of an acid catalyst. It can be obtained by a condensation reaction under an inert solvent.

Specific examples of flavan compounds represented by the formula (I) and suitable for use in the present invention include the following.

2 ', 4', 7-trihydroxyflavan, 2,4,4-trimethyl-2 ', 4', 7-trihydroxyflavan, 4-ethyl-2,3,4-trimethyl-2 ', 4 ', 7-trihydroxyflavan, 2,4
-Diethyl-4-methyl-2 ', 4', 7-trihydroxyflavan, 2,4,4-triethyl-3-methyl-
2 ', 4', 7-trihydroxyflavan, 2,4-dimethyl-3-isopropyl-4-isobutyl-2 ',
4 ', 7-trihydroxyflavan, 2,4-diisobutyl-4-methyl-2', 4 ', 7-trihydroxyflavan, 6-hydroxy-4a- (2,4-dihydroxyphenyl) -1,2, 3,4,4a, 9a- hexahydroxoplatinate Santen 9-spiro-1'-cyclohexane [i.e., in formula (I), ^{X = Y = R 3 = H} , R 1
And R ² combine to form tetramethylene, and R ⁴ and R ⁵
A compound in which pentamethylene is bonded to each other], 2,
4,4,5,6'-pentamethyl-2 ', 4', 7-trihydroxyflavan, 2,4,4-trimethyl-
2 ', 4', 5 ', 6,7-pentahydroxyflavan, 2,4,4-trimethyl-2', 4 ', 5,6',
7-pentahydroxy flavan, 2,4,4-trimethyl-5 ', 6-di-tert-butyl-2', 4 ', 7-trihydroxy flavan and the like.

Of the flavan compounds represented by the formula (I), those in which X and Y are each hydrogen are preferably used in terms of rubber performance. Above all, 2,4,4-trimethyl-2 ', 4', 7-trihydroxyflavan obtained by condensation of resorcin and acetone is preferable in view of raw material circumstances. All of the flavan compounds represented by the formula (I) solve the problem of transpiration in the rubber processing step as compared with resorcin.

There is no particular limitation on the amount of flavan compound added, but generally 0.5 to 1 per 100 parts by weight of rubber.
A range of 0 parts by weight is preferred. Hereinafter, the parts by weight of the compounding components per 100 parts by weight of the rubber will be expressed in units of phr. If the amount of the flavan compound is too small, the improving effect will be insufficient, and if it is too large, it will be uneconomical. Preferably, this compound is used in the range of 0.5 to 3 phr.

The carbon black used in the present invention is of the type commonly used in the rubber industry, such as SAF, ISAF, HAF, FEF, SRF, GPF,
It can be MT or the like. The amount of carbon black compounded is not particularly limited, but is preferably in the range of 20 to 150 phr from the viewpoints of reinforcing properties, rubber hardness, heat resistance, dynamic durability and the like. Further, if necessary, a filler other than carbon black can be included. As such a filler, various ones usually used in the rubber industry,
Examples thereof include inorganic fillers such as silica, clay and calcium carbonate. In particular, in a rubber composition that is involved in adhesion to a reinforcing material such as a coating rubber of a carcass part of a tire member, it is preferable to incorporate hydrous silica in order to improve adhesion to a cord such as an organic fiber. When using hydrous silica, the compounding amount is 5 to 40 phr.
Is preferred.

In the present invention, the time of addition of the flavan compound is important. Generally, when compounding agents are compounded in rubber, the compounding is basically carried out in two steps. That is, carbon black and other fillers, process oils,
Stearic acid or the like is added in the first step at a relatively high rubber temperature of about 120 to 180 ° C., and a vulcanizing agent such as sulfur, a vulcanization accelerator, a vulcanization retarder, and a crosslinking agent are added.
The rubber is added in the second step at a relatively low temperature of 40 to 120 ° C.

According to the present invention, the flavan compound is blended with the raw rubber in the first step at a high temperature in which carbon black or the like is blended. As a result, it is possible to achieve a great improvement effect in rubber physical properties such as hardness and dynamic elastic modulus, as compared with the case of adding in the second step at low temperature. In addition, the temperature at which the flavan compound is compounded is generally 130 to 180 because the higher the temperature, the greater the effect of improving the rubber physical properties.
The range of ° C is preferred. In this way, after blending carbon black and flavan compounds in the high temperature kneading process,
A vulcanizing agent such as sulfur is mixed at a low temperature, for example, about 40 to 120 ° C., and if necessary, a vulcanization accelerator is mixed and vulcanized. When sulfur is used, it is usually added in the range of about 1 to 10 phr.

There is no particular limitation on the mixer used in the first kneading step and the second kneading step, and those commonly used in the rubber industry, such as Banbury mixer,
A kneader or open mill can be used. of course,
Different mixers may be used in the first step and the second step.

In the present invention, further, if necessary,
A methylene donor can be included. The methylene donor can be any of those commonly used in the rubber industry with methylene acceptors such as resorcin. For example, condensates of melamine and formaldehyde, such as dimethylol melamine, trimethylol melamine, tetramethylol melamine, hexamethylol melamine, condensates of melamine, formaldehyde and methanol, that is, hexakis (methoxymethyl) melamine, pentakis (methoxy). Those such as methyl) methylol melamine, and further hexamethylene tetramine can be applied. Among these, a condensate of melamine, formaldehyde and methanol is preferable. When a methylene donor is used, the compounding amount is generally in the range of about 0.5 to 6 phr. If the amount of the methylene donor is less than 0.5 phr, the effect of improving the hardness of the rubber is small even if it is added. On the other hand, if it is more than 6 phr, the elongation at break, the tensile strength and the tensile stress of the rubber are lowered, and further the tensile strength after heat aging and the retention rate of the tensile stress are remarkably lowered, which is not preferable. When a methylene donor is used, it is usually incorporated in the second step at a low temperature.

In the present invention, various rubber chemicals usually used in the rubber industry, for example, antioxidants such as antioxidants and ozone deterioration inhibitors, crosslinking agents, vulcanization accelerators, and vulcanization retardants are used. Agent, deflocculant, tackifier, processing aid,
It goes without saying that one kind or two or more kinds of wax, oil, stearic acid and the like may be used in combination if necessary. Depending on the intended use of the rubber composition, each of these rubber chemicals may be used in an amount within the range normally used in the rubber industry.

In particular, at least one selected from N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinoline polymer as an antioxidant. It is preferable to mix seeds. When an antiaging agent is added, it is usually used in the range of 0.5 to 3 phr. Anti-aging agents
Although it may be compounded in either the high temperature first step or the low temperature second step, it is usually compounded in the first step.

Thus, in vulcanizing the rubber composition in which the flavan compound is blended together with carbon black and, if necessary, further blended with other compounding agents, it is appropriate to vary depending on the type of base rubber and various compounding agents. Conditions are adopted. The vulcanization conditions themselves may be those conventionally adopted generally, and are not particularly limited in the present invention.

The rubber composition thus blended and vulcanized imparts excellent performance to various members of tires and other rubber products. For example, when manufacturing various members such as a tread portion of a tire, a carcass portion, a sidewall portion, and a bead portion, by applying the method of the present invention,
High performance tires are manufactured.

[0031]

EXAMPLES Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. In the following examples,% representing the amount added or content
Unless otherwise specified, parts and parts are% by weight and parts by weight, respectively.

The flavan compounds or comparative compounds used in Examples and Comparative Examples are as follows, and are represented by respective symbols below.

B1: 2,4,4-trimethyl-2 ',
4 ', 7-trihydroxyflavan B2: 2,4-diethyl-4-methyl-2', 4 ',
7-trihydroxyflavan B3: 2,4,4-triethyl-3-methyl-2 ',
4 ', 7-trihydroxyflavan B4: 2,4-diisobutyl-4-methyl-2',
4 ', 7-trihydroxyflavan B5: 6-hydroxy-4a- (2,4-dihydroxyphenyl) -1,2,3,4,4a, 9a-hexahydroxanthene-9-spiro-1'-cyclohexane X : Resorcin

Example 1 <Compounding formulation> Natural rubber 100 parts HAF carbon black (N330) 45 parts Hydrous silica (Nipsil AQ manufactured by Nippon Silica Industry Co., Ltd.) 10 parts Stearic acid 3 parts Lead zinc 5 parts Anti-aging agent 2 Part (N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine) Test compound 2 parts Vulcanization accelerator 1 part (N-cyclohexyl-2-benzothiazylsulfenamide) Iou 2 Part Methoxylated methylol melamine resin 4 parts (Sumitanol 507 Sumikanol 507)

As a Banbury mixer, a 600 ml Labo Plastomill manufactured by Toyo Seiki Seisakusho Co., Ltd. was used, and the oil bath temperature was 150 ° C., based on the above-mentioned formulation, natural rubber,
Carbon black, hydrous silica, stearic acid, zinc white, antioxidant and test compound were added and kneaded for 15 minutes at a mixer rotation speed of 50 rpm. The rubber temperature at this time was 155 to 165 ° C.

Next, this compound was transferred to an open mill, and at a rubber temperature of 50 to 70 ° C., the vulcanization accelerator, sulfur and methoxylated methylolmelamine resin shown in the above compounding formulation were added and kneaded. For comparison, the test compound was not added in the first step using a Banbury mixer, and the test compound was added together with the vulcanization accelerator, sulfur and methoxylated methylol melamine resin in the second step using an open mill. Then, a sample kneaded at a low temperature was also prepared.

A part of the kneaded sample was subjected to the Mooney Scorch test. Further, the remaining samples were molded into a predetermined shape and vulcanized at 145 ° C. for 30 minutes to prepare test pieces for a dynamic viscoelasticity test, a hardness test and a tensile property test. Each test was conducted by the following method, and the results are shown in Table 1.

Mooney Scorch Test For the rubber compound before vulcanization, according to JIS K 6300,
The time until the temperature rises by 5 points from the minimum value at 125 ° C. is defined as Mooney scorch time (t ₅ ). A longer Mooney scorch time means less scorch and better workability.

Dynamic viscoelasticity test As a dynamic viscoelasticity test measuring instrument, a viscoelasticity spectrometer F-III manufactured by Iwamoto Seisakusho Co., Ltd. was used, and an initial load of 100 was used.
g, dynamic load 20 g, frequency 10 Hz, dynamic elastic modulus (E ′) and loss coefficient (tan δ) at 60 ° C. were measured. A larger value of the dynamic elastic modulus means a better toughening effect, and a smaller value of the loss coefficient means a better heat resistance and blowout resistance.

Hardness Test According to JIS K 6301, a 12.7 mm thick straight cylindrical test piece was used to measure the hardness with a spring type hardness tester (A type).

Tensile Property Test According to JIS K 6301, a dumbbell-shaped No. 3 test piece was used to measure M ₃₀₀ as tensile strength, breaking elongation and tensile stress. The larger the tensile strength, the elongation at break and the tensile stress, the better the tensile properties.

[0042]

[Table 1] ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Run Combination Mooney ・ Hardness at 60 ℃ Physical properties No.  ScorchDynamic viscoelasticity   Test compound Melamine time E'tan δ Tensile rupture M₃₀₀ Type (part) compound resin²t_Five Strength Growth period¹(Part) (Min) (MPa) (MPa) (%) (MPa) ───────────────────────────────── ──── The present invention 1 B1 2 1st 4 17.9 20.3 0.067 75 23.8 450 15.2 2 B2 2 1st 4 18.1 19.7 0.069 74 23.9 450 15.3 3 B3 2 1st 4 18.0 19.5 0.070 74 24.2 460 14.9 4 B4 2 1st 4 18.1 19.3 0.071 74 24.0 450 14.9 5 B5 2 Daiichi 4 18.1 20.1 0.069 74 24.0 450 15.1 ──────────────────────────────────── ─ Comparison 6 None--None 18.0 10.2 0.100 65 24.6 470 14.1 7 X 2 1st 4 13.0 19.0 0.071 74 21.6 410 15.0 8 B1 2 2nd 4 18.0 14.3 0.088 69 24.0 450 14.1 9 B2 2 2nd 4 18.2 13.5 0.094 68 23.8 450 14.0 10 B3 2 2nd 4 18.0 14.0 0.092 67 23.9 450 14.1 11 B4 2 2nd 4 18.2 14.1 0.089 68 23.7 440 14.0 12 B5 2 2nd 4 18.1 14.2 0.088 69 24.0 450 14.1 ━━━━━━━━━━━━ ━━━━━━━━━━━━━━━━━━━━━━━━━━ Note¹⁾Compounding time of test compound 1st: 1st process (Bamba
Lee mixer) Addition 2nd: Addition in 2nd step (open mill)²⁾ Melamine resin: methoxylated methylol melamine resin

Example 2 <Compounding formulation> Natural rubber 100 parts ISAF carbon black (N220) 50 parts Stearic acid 1 part Lead sinter 5 parts Aroma oil 5 parts Anti-aging agent 2 parts (2,2,4-trimethyl-1) , 2-dihydroquinoline polymer) Test compound 1.5 parts Vulcanization accelerator 1.25 parts (N, N-dicyclohexyl-2-benzothiazylsulfenamide) io 1.5 parts Methoxylated methylol melamine Resins listed in Table 2 (Sumitol Chemical Co., Ltd. Sumikanol 507)

As a Banbury mixer, 600 ml Labo Plastomill manufactured by Toyo Seiki Seisakusho Co., Ltd. was used, the oil bath temperature was 150 ° C., and natural rubber was prepared according to the above-mentioned formulation.
Carbon black, stearic acid, zinc white, aroma oil,
An antioxidant and a test compound were added and the mixture was kneaded at a mixer rotation speed of 50 rpm for 15 minutes. The rubber temperature at this time was 155 to 160 ° C.

Next, this compound was transferred to an open mill, and at a rubber temperature of 50 to 70 ° C., the vulcanization accelerator, sulfur and methoxylated methylolmelamine resin shown in the above compounding formulation were added and kneaded. For comparison, the test compound was not added in the first step using a Banbury mixer, and the test compound was added together with the vulcanization accelerator, sulfur and methoxylated methylol melamine resin in the second step using an open mill. Then, a kneaded sample was also prepared.

A part of the kneaded sample was subjected to the Mooney Scorch test. Further, the remaining samples were molded into a predetermined shape and vulcanized at 150 ° C. for 35 minutes to prepare test pieces for a dynamic viscoelasticity test, a hardness test and a tensile property test. The dynamic viscoelasticity test was carried out by the following method, and the Mooney scorch test was carried out in the same manner as in Example 1 except that the measurement temperature was 135 ° C.
A scorch test, hardness test and tensile property test were performed.
The results are shown in Table 2.

Dynamic Viscoelasticity Test As a dynamic viscoelasticity tester, a viscoelasticity spectrometer F-III manufactured by Iwamoto Seisakusho Co., Ltd. was used, and initial strain was 10%, dynamic strain amplitude was 0.5%, and frequency was 10 Hz. The dynamic elastic modulus (E ') and loss coefficient (tan δ) at 60 ° C were measured. A larger value of the dynamic elastic modulus means a better toughening effect, and a smaller value of the loss coefficient means a better heat resistance and blowout resistance.

[0048]

[Table 2] ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Run Combination Mooney ・ Hardness at 60 ℃ Physical properties No.  ScorchDynamic viscoelasticity   Test compound Melamine time E'tan δ Tensile rupture M₃₀₀ Type (part) compound resin²t_Five Strength Growth period¹(Part) (Min) (MPa) (MPa) (%) (MPa) ───────────────────────────────── ──── The present invention 1 B1 1.5 1st 2 49.9 17.5 0.117 69 22.5 480 12.5 2 B1 1.5 1st 4 49.3 19.6 0.113 73 22.7 460 14.0 3 B5 1.5 1st 2 50.3 17.3 0.119 69 22.4 480 12.4 ──────────── ───────────────────────── Comparison 4 None--None 50.5 9.7 0.132 60 22.2 510 10.7 5 X 1.5 1st 2 44.2 14.7 0.122 69 20.5 450 11.7 6 B1 1.5 2nd 2 49.7 13.2 0.127 64 22.5 480 11.0 7 B5 1.5 2nd 2 50.4 13.0 0.129 63 22.3 490 10.8 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Note¹⁾Compounding time of test compound 1st: 1st process (Bamba
Lee mixer) Addition 2nd: Addition in 2nd step (open mill)²⁾ Melamine resin: methoxylated methylol melamine resin

Example 3 (Evaluation of transpiration property) In order to evaluate the transpiration property of the flavan compounds B1 to B5 and the comparative compound X (resorcin) listed above, 3 g of each compound was placed in a sample bottle and placed in a thermostatic chamber at 145. The weight retention was measured after heating for 6 hours at ℃ and 180 ℃ respectively. The results are shown in Table 3.

[0050]

[Table 3] ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Heating test product temperature B1 B2 B3 B4 B5 X ───────────────────────────────── Weight retention rate 145 ℃ 100.0 100.0 100.0 100.0 100.0 98.1 (%) 180 ℃ 99.5 99.5 99.5 99.5 99.6 91.8 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

As can be seen from the above table, the flavan compounds specified in the present invention have a smaller transpiration property than resorcin.

[0052]

EFFECTS OF THE INVENTION A vulcanized rubber having a high hardness and a high dynamic elastic modulus is produced by using a specific flavan compound according to the present invention and compounding it with carbon black in a kneading process at a high temperature. can do. In addition, the problem of transpiration, which is a drawback of conventional resorcin, can be solved. Further, the vulcanized rubber obtained by the present invention,
Rubber strength, such as tensile properties, is hardly reduced, and scorch resistance is also excellent. Therefore, by adopting this method, a high-quality vulcanized rubber product can be manufactured.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hideo Nagasaki 3-98 Kasugadeka, Konohana-ku, Osaka Sumitomo Chemical Co., Ltd.

Claims (9)

[Claims] 1. A raw material rubber selected from natural rubber, styrene-butadiene copolymer rubber, butadiene rubber, isoprene rubber, acrylonitrile-butadiene copolymer rubber, chloroprene rubber, butyl rubber and halogenated butyl rubber, together with carbon black, together with formula (I). (In the formula, R ¹ , R ² , R ³ , R ⁴ and R ⁵ are each independently hydrogen or an aliphatic group having 1 to 6 carbon atoms,
When R ¹ , R ² , R ⁴ and R ⁵ are all chain aliphatic groups, R ¹ and R ² may be bonded to each other and R ⁴ and R ⁵ may be bonded to each other to form a ring. Well; X and Y are
Flavan compounds represented by hydrogen, a hydroxyl group or an aliphatic group having 1 to 8 carbon atoms are independently blended in a kneading step at a high temperature, and then vulcanized in the presence of a vulcanizing agent. Manufacturing method of vulcanized rubber. 2. The method according to claim 1, wherein a flavan compound in which X and Y in the formula (I) are each hydrogen is used. 3. The method according to claim 2, wherein the flavan compound is 2,4,4-trimethyl-2 ', 4', 7-trihydroxyflavan. 4. The method according to claim 1, wherein 20 to 150 parts by weight of carbon black and 0.5 to 10 parts by weight of the flavan compound are mixed with 100 parts by weight of the raw rubber. 5. The method according to claim 1, wherein the carbon black and the flavan compound are compounded into the raw rubber at a temperature of 130 to 180 ° C. and kneaded. 6. The method according to claim 5, wherein the vulcanizing agent is sulfur, the carbon black and the flavan compound are blended in the raw rubber and kneaded, and then the sulfur is blended at a temperature of 40 to 120 ° C. 7. N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine and 2,2,2.
The method according to any one of claims 1 to 6, wherein an antioxidant selected from a polymer of 4-trimethyl-1,2-dihydroquinoline is added. 8. A tire manufactured by the method according to claim 1. 9. A raw material rubber selected from natural rubber, styrene-butadiene copolymer rubber, butadiene rubber, isoprene rubber, acrylonitrile butadiene copolymer rubber, chloroprene rubber, butyl rubber and halogenated butyl rubber, together with carbon black, together with formula (I). (In the formula, R ¹ , R ² , R ³ , R ⁴ and R ⁵ are each independently hydrogen or an aliphatic group having 1 to 6 carbon atoms,
When R ¹ , R ² , R ⁴ and R ⁵ are all chain aliphatic groups, R ¹ and R ² may be bonded to each other and R ⁴ and R ⁵ may be bonded to each other to form a ring. Well; X and Y are
Flavan-based compounds represented by hydrogen, a hydroxyl group or an aliphatic group having 1 to 8 carbon atoms are independently blended in a high-temperature kneading step, and vulcanized in the presence of a vulcanizing agent. A method for improving hardness and dynamic elastic modulus of sulfur rubber.