JPH0571624B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel reinforced rubber composition with excellent productivity and processability, as well as excellent strength and modulus of the vulcanizate, and a method for producing the same. Conventionally, reinforcing rubber compositions used in various parts of tires have been manufactured by blending short fibers such as nylon, polyester, vinylon, etc. with vulcanizable rubber. However, the reinforced rubber composition obtained in this way has a large fiber diameter and does not have a bond between the fibers and the rubber, and therefore the strength and modulus of the vulcanizate, especially the modulus and strength at high elongation, are insufficient. There is a desire to develop a reinforced rubber composition that provides a vulcanizate with even greater modulus and strength. Therefore, an elastomer strengthening method and a reinforced elastomer composition have been proposed in which a polymer having fiber-forming ability and rubber are kneaded and then the kneaded product is extruded (Japanese Patent Application Laid-Open No. 8682/1982). However, even with this method, thick fibers and films are produced, and because there is no bond between rubber and polymer (fibers) at the fiber interface, the tensile strength of the vulcanizate, the modulus at high elongation, etc. The peel strength, which indicates the adhesive force with the seed base material, is low, making it impossible to obtain a reinforced rubber composition that can be used as a tire member. Japanese Patent Publication No. 55-41652 describes a method for producing a reinforced rubber composition by kneading vulcanizable rubber and powdered 1,2-polybutadiene, extruding the kneaded product, and then rolling it with rolls. There is. In the reinforced rubber composition obtained by this method, the vulcanizate exhibits high elasticity, high elongation, high strength, and high peel strength, but the strength of the fibers formed from 1,2-polybutadiene is low. Fibers are cut during gum processing, particularly during carbon black kneading, resulting in short fiber lengths and have the disadvantage that stress is small when the vulcanizate is at low elongation. Therefore, in order to improve the drawbacks of the conventionally known reinforced rubber compositions, the present inventors melt-extruded a composition in which a block copolymer of liquid diene rubber and nylon was blended into vulcanizable rubber. proposed a method for manufacturing a reinforced rubber composition by making nylon into fibers and crafting vulcanizable rubber and liquid diene rubber (Japanese Patent Application No. 117044/1983).
However, this production method has problems in practice because the reproducibility of block polymerization is not very good and the cost is high. The inventors completed this invention as a result of intensive research aimed at providing a reinforced rubber composition and a method for producing the same that do not have the above-mentioned drawbacks. That is, in this invention, 100 parts by weight of vulcanizable rubber contains

1 to 100 parts by weight of fine short fibers of a thermoplastic polymer having a [formula] group and a melting point of 190 to 235°C are embedded, and the polymer and vulcanizable rubber are bonded at the interface of the fibers. is grafted via an initial condensate of a novolak type phenol formaldehyde resin, a vulcanizable rubber, and a molecular weight
in less than 200,000 polymer molecules

[Formula] A thermoplastic polymer having a group and having a melting point of 190 to 235°C,
0.2 to 5 parts by weight of an initial condensate of novolac-type phenol formaldehyde resin (hereinafter also simply referred to as novolak) per 100 parts by weight of the total amount of these rubbers and thermoplastic polymers, and a compound that can generate formaldehyde when heated. are kneaded at a temperature above the melting point of the thermoplastic polymer and below 270°C, and the resulting kneaded product is mixed so that the ratio of rubber and thermoplastic polymer in the kneaded product is 1 to 100 parts by weight of thermoplastic polymer per 100 parts by weight of rubber. When the amount is 100 parts by weight, the ratio of rubber and thermoplastic polymer in the kneaded material is 1 part by weight per 100 parts by weight of rubber.
When the amount exceeds 1 part by weight, additional vulcanizable rubber is added to the kneaded mixture so that the thermoplastic polymer is 1 to 100 parts by weight per 100 parts by weight of the total rubber.
Furthermore, the temperature must be above the melting point of the thermoplastic polymer and 270℃.
A method for producing a reinforced rubber composition, which comprises kneading at the following temperature, extruding at a temperature above the melting point of the thermoplastic polymer and below 270°C, and stretching the extrudate at a temperature below the melting point of the thermoplastic polymer. It is related to. The reinforced rubber composition of the present invention has excellent productivity and processability, and can provide a vulcanizate with excellent modulus, tensile strength, and adhesion at low and high elongations. Further, according to the method of the present invention, in the vulcanizable rubber, polymer molecules having a molecular weight of less than 200,000

[Formula] A thermoplastic polymer with a melting point of 190 to 235°C, an initial condensate of novolak-type phenol formaldehyde resin (novolak), and a compound that can generate formaldehyde when heated. Vulcanized with excellent physical properties. A reinforced rubber composition that provides a product can be produced with good reproducibility through simple operations. As the vulcanizable rubber in this invention, all rubbers that give a rubber elastic body by vulcanization can be used, such as natural rubber,
Examples include cis-1,4-polybutadiene, polyisoprene, polychloroprene, styrene-butadiene copolymer rubber, isoprene-isobutylene copolymer, ethylene-propylene-nonconjugated diene terpolymer, and mixtures thereof. .
Among these rubbers, vulcanizable rubber and molecules

[Formula] group and a mixture of a thermoplastic polymer with a melting point of 190 to 235°C, novolak, and a compound that can generate formaldehyde when heated,
Natural rubber is preferred because it hardly gels when the kneaded product is extruded. The reinforced rubber composition of the present invention includes 100 parts by weight of the above-mentioned vulcanizable rubber and

1 to 100 parts by weight, preferably 1 to 70 parts by weight, particularly preferably 30 to 70 parts by weight of fine short fibers of a thermoplastic polymer having a [formula] group and having a melting point of 190 to 235°C are embedded. The polymer and the vulcanizable rubber are grafted (bonded) via a novolac at the interface of the fiber. The fine short fibers of the thermoplastic polymer are nylon 6, nylon, having a melting point of 190-235°C, preferably 190-225°C, particularly preferably 200-220°C.
In polymer molecules such as nylon such as 610, nylon 12, nylon 611, and nylon 612, polyurea such as polyheptamethylene urea, polyundecamethylene urea, and polyurethane.

[Formula] It is formed from a thermoplastic polymer having a group, preferably nylon, and has an average diameter of 0.05 to 0.8 μ, a circular cross section, the shortest fiber length is preferably 1 μ or more, and molecules are arranged in the fiber axis direction. It is embedded in vulcanizable rubber in the form of fine short fibers. Moreover, at the interface of the fibers, there is a

A thermoplastic polymer having the formula [formula] and a vulcanizable rubber are grafted via a novolak. The above-mentioned novolacs are catalysts known per se,
For example, soluble and fusible substances obtained by condensing phenols such as phenol and bisphenols with formaldehyde (or paraformaldehyde) using an acid such as sulfuric acid, hydrochloric acid, phosphoric acid, or oxalic acid as a catalyst. These are resins and their modified products. As a novolac, for example,
Novolak type phenol formaldehyde initial condensate, novolak type lactam-bisphenol F
-Formaldehyde initial condensates, novolak-type styrenated phenol-phenol-formaldehyde initial condensates, etc. can be suitably used. In the reinforced rubber composition of this invention, in the polymer molecules embedded in the vulcanizable rubber,

[Formula] The strength of the fine short fibers of the thermoplastic polymer having the group is high, and since the thermoplastic polymer and the vulcanizable rubber are graft-bonded via novolac at the interface of the fibers, the elongation is low. It is possible to obtain a reinforced rubber composition that provides a vulcanizate that has excellent modulus and tensile strength at high elongation and high elongation, and also has excellent adhesion to rubber vulcanizates such as natural rubber vulcanizates and to members such as steel. It can be done. In addition, the above-mentioned graft bond can be applied to vulcanizable rubber or polymer molecules.

[Formula] It is not possible to say conclusively about the reaction mode of the thermoplastic polymer having the group, novolak, and a compound that can generate formaldehyde when heated, which is a formaldehyde donor, but formaldehyde generated from the formaldehyde donor acts on the novolak first. At least two methylol groups are generated in the novolac, and a dehydration reaction between one hydroxyl group of the plurality of methylol groups and a hydrogen atom of a methylene group in a polymer molecule of the vulcanizable rubber, and a thermoplastic polymer. in the molecule

It is thought to be produced by a dehydration reaction between the hydrogen atom of the [Formula] group and the hydroxyl group of the remaining methylol group of the novolak bonded to the vulcanizable rubber. In the reinforced gum compositions of this invention, in the polymer molecules embedded in the vulcanizable rubber,

The proportion of fine short fibers of the thermoplastic polymer having the group [Formula] is 1 to 100 parts by weight, preferably 1 to 70 parts by weight, particularly preferably 30 to 70 parts by weight, per 100 parts by weight of vulcanizable rubber. Parts by weight. If the proportion of fibers embedded in vulcanizable rubber is less than the above-mentioned lower limit, the strength and modulus of the vulcanizate will not be improved, and the proportion of fibers embedded in vulcanizable rubber will be lower than the above-mentioned upper limit. When the amount is larger than this, the adhesiveness of the vulcanizate decreases. Furthermore, in the reinforced rubber composition of the present invention, the weight of the fine short fibers of the thermoplastic polymer embedded in the vulcanizable rubber may be grafted to the thermoplastic polymer via a novolac at the interface of the fibers. The fibers are used in such a way that the grafting rate, expressed as a proportion of the weight of vulcanizable rubber (vulcanizable rubber/fine short fibers of thermoplastic polymer), is 3 to 25% by weight, especially 5 to 20% by weight. Preferably, the thermoplastic polymer to be formed and the vulcanizable rubber are graft-bonded via a novolak. The reinforced rubber composition of the present invention having the above-mentioned characteristics includes, for example, vulcanizable rubber and molecular weight
in less than 200,000 polymer molecules

[Formula] A thermoplastic polymer having a group, an initial condensate of a novolak type phenol formaldehyde resin of 0.2 to 5 parts by weight per 100 parts by weight of the total amount of these rubbers and the thermoplastic polymer, and a formaldehyde donor are combined into a thermoplastic polymer. The resulting kneaded product is kneaded at a temperature above the melting point of If the ratio of rubber and thermoplastic polymer in the kneaded material is more than 1 part by weight of thermoplastic polymer per 100 parts by weight of rubber, add additional vulcanizable rubber per 100 parts by weight of total rubber. The thermoplastic polymer is added to the kneaded material in an amount of 1 to 100 parts by weight, and then kneaded at a temperature above the melting point of the thermoplastic polymer and below 270°C, and then at a temperature above the melting point of the thermoplastic polymer and below 270°C. extruded at a temperature of
It can be made by stretching the extrudate at a temperature below the melting point of the thermoplastic polymer. In the method of this invention, first, the above-mentioned vulcanizable rubber and a molecular weight (number average molecular weight) of less than 200,000,
Preferably in 10,000 to 100,000 of the aforementioned polymer molecules

[Formula] Thermoplastic polymer having a group, total amount of these rubbers and thermoplastic polymer
0.2 to 5 parts by weight per 100 parts by weight, preferably rubber
0.5 to 5 parts by weight per 100 parts by weight, particularly preferably
0.5 to 3 parts by weight of the aforementioned novolak and preferably 0.02 to 1 part by weight of formaldehyde donor per 100 parts by weight of rubber are kneaded at a temperature above the melting point of the thermoplastic polymer and below 270°C. As the formaldehyde donor, a compound that generates formaldehyde upon heating is used. For example, as a formaldehyde donor, hexamethylenetetramine, acetaldehyde ammonia:

[Formula] Examples include paraformaldehyde, α-polyoxymethylene, polyvalent methylol melamine derivatives, oxazolidine derivatives, polyvalent methylol acetylene urea, and the like. In the vulcanizable rubber and polymer molecules mentioned above.

[Formula] The ratio of the thermoplastic polymer having the group is not particularly limited, but it is usually vulcanizable rubber 100%
1 to 2000 parts by weight of thermoplastic polymer per part by weight,
Preferably 1 to 100 parts by weight, particularly preferably 1 to 100 parts by weight
It is 70 parts by weight. in vulcanizable rubber and polymer molecules

[Formula] The thermoplastic polymer having the group, the novolac, and the formaldehyde donor are kneaded at a temperature above the melting point of the thermoplastic polymer and below 270°C, preferably 5°C below the melting point of the thermoplastic polymer.
At temperatures above 260°C and above 260°C, the mixture of vulcanizable rubber, thermoplastic polymer, novolac and formaldehyde donor is carried out in a kind of molten state. The above-mentioned components are preferably kneaded for 1 to 15 minutes using a Brabender Plastograph, Banbury mixer, roll, extruder, etc.
There are no particular restrictions on the method of adding and kneading each of the above components into a kneading device such as a Brabender Plastograph, but first, vulcanizable rubber and, if necessary, an anti-aging agent are added to the kneading device and masticated. , then into the polymer molecule

[Formula] A thermoplastic polymer having a group is added and kneaded, the thermoplastic polymer is melted, and the thermoplastic polymer is dispersed in the rubber.
A method preferably employed is to then add novolak and knead, and finally add the formaldehyde donor and knead for 1 to 15 minutes to knead each component. The method of this invention utilizes the novolac and formaldehyde donor described above to form vulcanizable rubbers and polymers in vulcanizable rubber and polymer molecules.

[Formula] By kneading the thermoplastic polymer having the group, the novolac, and the formaldehyde donor as described above, the vulcanizable rubber and the thermoplastic polymer are graft-bonded via the novolac, and The thermoplastic polymer is finely dispersed in the sulfurable rubber (the particle size of the dispersed thermoplastic polymer is usually 1
~2μ. ) can be uniformly dispersed. If the amount of the novolac is less than the lower limit, the graft reaction between the vulcanizable rubber and the thermoplastic polymer through the novolac will be difficult to occur, resulting in the formation of thick fibers or films of the thermoplastic polymer, and Since the bond between the thermoplastic polymer and the rubber at the fiber interface is weak, the strength, adhesiveness, fatigue properties, etc. of the vulcanizate obtained by vulcanizing this reinforced rubber composition are reduced. Furthermore, if the amount of novolak is greater than the above upper limit, gelation of the thermoplastic polymer due to the novolak will occur, and fiber formation of the thermoplastic polymer will be reduced. Strength and modulus decrease. In the method of this invention, in the polymer molecule, as the polymer forming the fiber,

It is necessary to use thermoplastic polymers having the formula Even with polymers that can form fibers, there are

[Formula] In thermoplastic polymers that do not have groups, the particle size of the thermoplastic polymer dispersed in the rubber becomes large, forming thick fibers or films, and graft bonding between the thermoplastic polymer and the rubber occurs at the fiber interface. Therefore, it cannot be used in the method of this invention. In the method of this invention, an anti-aging agent, for example N-
(3-methacryloyloxy-2-hydroxypropyl)-N'-phenyl-p-phenyldiamine, phenyl-α-naphthylamine, phenyl-β-naphthylamine, N,N'-diphenyl-
p-phenylenediamine, N-isopropyl-
N'-phenyl-p-phenylenediamine, N-
Cyclohexyl-N'-phenyl-p-phenylenediamine, 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-α-dimethylamino-p-cresol, 2,2'- Dihydroxy-3,3'-bis(α-methylcyclohexyl)
It is preferable to incorporate a low volatility anti-aging agent such as -5,5'-dimethyl diphenylmethane. In the method of this invention, the kneaded product obtained by kneading each component as described above is added to the rubber and polymer molecules in the kneaded product.

[Formula] When the ratio of the thermoplastic polymer to the group-containing thermoplastic polymer is 1 to 100 parts by weight, preferably 1 to 70 parts by weight, particularly preferably 30 to 70 parts by weight, per 100 parts by weight of rubber, it is left as is. When the ratio of the thermoplastic polymer to the rubber in the extruded and kneaded portion is more than 1 part by weight of the thermoplastic polymer per 100 parts by weight of rubber, additional vulcanization selected from the above-mentioned vulcanizable rubbers is added. Add the available rubber to the kneaded product in an amount of 1 to 100 parts by weight, preferably 1 to 70 parts by weight, particularly preferably 30 to 70 parts by weight of thermoplastic polymer per 100 parts by weight of the total rubber, and further a temperature above the melting point of the thermoplastic polymer and below 270°C;
Preferably 5°C below the melting point of the thermoplastic polymer.
After kneading at a temperature higher than 260°C and lower than 260°C, the mixture is pushed back. If the proportion of the thermoplastic polymer in the kneaded product when extruding the kneaded product is less than the lower limit, it will not be possible to obtain a reinforced rubber composition that provides a vulcanizate with excellent strength and modulus, and the kneaded product will not be extruded. If the proportion of nylon in the kneaded material at the time of discharge is higher than the above upper limit,
It becomes difficult to obtain a reinforced rubber composition that provides a vulcanizate with excellent adhesion. The kneaded material can be extruded into a string (or sheet) through a die having a circular or rectangular discharge opening, such as a circular die or a rectangular die. When using a circular die, the inner diameter of its discharge port should be 0.1
~5mm, the ratio of the length of the outlet to the inner diameter of the outlet (L/
D) is preferably 1 to 20, and when using a rectangular die, the slit gap is 0.1 to 5 mm,
It is preferable that the width is 0.2 to 200 mm and the length of the die land is 10 to 20 mm. Among the various dies described above, it is preferable to use circular dies. As the circular die, one having one discharge port or one having multiple discharge ports (multi-hold type) can be used. For extrusion of the kneaded material, a known extruder such as a screw type extruder is used, and the temperature of the screw tip is set to a temperature above the melting point of the thermoplastic polymer and below 270°C, and the temperature of the die is set to a temperature above the melting point of the thermoplastic polymer and below 270°C. It is preferable to extrude the kneaded material at a temperature that is higher than the melting point of the polymer and lower than 270°C, particularly higher than the melting point of the thermoplastic polymer by 5°C or higher and lower than 260°C. In the method of this invention, by extruding the kneaded material as described above, the thermoplastic polymer in the vulcanizable rubber of the extrudate obtained is in a fibrous form, and the fibrous thermoplastic polymer interface In this case, a thermoplastic polymer and a vulcanizable rubber are grafted together via a novolak. In the reinforced rubber composition of the present invention, the above extrudate is air-cooled, preferably under continuous tension.
The melting point of thermoplastic polymers is reduced by water cooling, cooling with inert organic solvents for rubber and thermoplastic polymers such as chilled methanol, or by increasing the distance from the die to the take-up (also called winder). Cooled to a lower temperature and placed on a winding machine, such as a bobbin or a winding roll, in a manner known per se.
It can be obtained by winding at a winding speed of m/min, preferably 20 to 40 m/min, and then rolling using a pair of rolling rolls or uniaxially stretching using a stretching roll. can. The temperature of the winder when taking off the extrudate is preferably 0 to 100°C.
If the extrudate is wound up without being cooled, a portion of the fibrous thermoplastic polymer will become flat (in extreme cases, film-like), and good results may not be obtained. The temperature of rolling with the above-mentioned rolling rolls is 0~
100°C is preferred. Further, it is preferable that the stretching using the stretching rolls be carried out at a stretching ratio of 1.1 to 10. In the method of the present invention, by stretching the extrudate as described above, the thermoplastic polymer in the vulcanizable rubber of the resulting reinforced rubber composition is converted into a fibrous structure through molecular orientation of the fibers. This results in fine short fibers with high strength. The reinforced rubber composition obtained by the method of this invention contains 1 to 100 parts by weight of polymer molecules per 100 parts by weight of vulcanizable rubber.

[Formula] contains a thermoplastic polymer having a group, the thermoplastic polymer is fine short fibers, and the thermoplastic polymer and vulcanizable rubber are graft-bonded via novolac at the interface of the fibers. It can be used alone or blended with vulcanizable rubber to produce vulcanizates with excellent modulus at low and high elongations, tensile strength, adhesion to various materials, and fatigue properties. can give. By utilizing its excellent properties, the reinforced rubber composition of the present invention can be applied to tire internal parts such as belts, carcass, and beads, tire external parts such as treads and sidewalls, industrial products such as belts and hoses, and footwear materials. It can be used for the following purposes. Next, examples, comparative examples, and reference examples will be shown. Physical property tests of vulcanizates conducted to evaluate the (reinforced) rubber compositions obtained in Examples, Comparative Examples, and Reference Examples were measured in accordance with JISK6301. Examples of the production of novolak used in Examples are shown below. In the following description, parts indicate parts by weight. A Novolac-type phenol-formaldehyde initial condensate (hereinafter sometimes simply referred to as Novolac A) Softening point obtained by condensing phenol and paraformaldehyde using oxalic acid as a catalyst
Novolac-type phenol-formaldehyde initial condensate (manufactured by Meiwa Kasei Co., Ltd., trade name 550PL), which is a powder crystal with a moisture content of 0.12% by weight and a free phenol content of 0.13% by weight at 106°C.B Novolac-type lactam-bisphenol F-
Formaldehyde initial condensate (hereinafter sometimes simply referred to as Novolac B) 141 parts of ε-caprolactam and 55.6 parts of paraformaldehyde with a purity of 81% were reacted at 120°C for 5 hours to form an addition reaction product of ε-caprolactam and formaldehyde. An addition reaction solution was obtained.
The entire amount of this addition reaction solution was added to bisphenol F315.
32 parts of water and 1.6 parts of 35% hydrochloric acid were gradually added dropwise to cause a condensation reaction between the ε-caprolactam-formaldehyde adduct and bisphenol F, and then the reaction mixture was distilled under reduced pressure ( 180° C., 10 mmHg) to obtain 469 parts of a novolac-type lactam-bisphenol F-formaldehyde initial condensate. C Novolac type styrenated phenol-phenol-formaldehyde initial condensate (hereinafter sometimes simply referred to as Novolac C) 1041 parts of styrene was gradually dropped into a mixed solution of 1412 parts of phenol and 40.3 parts of hydrochloric acid with a concentration of 35%,
The phenol was styrenated by mixing at 130℃ for 2 hours, and the reaction mixture was distilled under reduced pressure (180℃, 40mm
Hg) to obtain styrenated phenol. Formalin is added to the total amount of this styrenated phenol.
1426 parts and 87 parts of 40% sodium hydroxide were added and mixed at 80°C for 5 hours to add formaldehyde (methylolation) to the styrenated phenol. Phenol 1653 is added to the total amount of this addition reaction product.
1 part and 123 parts of oxalic acid were added, and the methylolated styrenated phenol and phenol were subjected to a condensation reaction at 100°C for 2 hours. The reaction mixture was distilled under reduced pressure (100→180℃, 40mmHg) to determine the softening point.
2959 parts of a styrenated phenol-phenol-formaldehyde initial condensate at 73°C (ring and ball method) was obtained. Example 1 100 parts of natural rubber (NR) having a viscosity of 1 x ¹⁰⁶ poise and N-(3-methacryloyloxy-2-hydroxypropyl)-N'- were placed in a Brabender Plastograph set at 220°C and 50 rpm. Phenyl-p-phenylenediamine
1. Add 1.0 part of Ouchi Shinko Kagaku Kogyo Co., Ltd., and add 30
After mastication for seconds, 50 parts of 6-nylon (trade name: 1030B, manufactured by Ube Industries, Ltd., melting point 221°C, molecular weight 30000) was added and kneaded for 4.5 minutes, then 2.25 parts of Novolak A was added and kneaded for 3 minutes. After kneading, 0.225 parts of hexamethylenetetramine was added and kneaded for 3.5 minutes (during which time the temperature in the Brabender rose to 230°C) to obtain a kneaded product. The obtained kneaded material was passed through a circular die with a nozzle inner diameter of 2 mm and a length to inner diameter ratio (L/D) of 2.
Using a 20mmφ extruder (manufactured by Hoake), the extrudate was extruded into a string at a die setting temperature of 235°C, and the extrudate was placed in a funnel located vertically below the nozzle. Water is supplied and the supplied cooling water flows through the funnel and down into a cooling water storage vessel located vertically below the funnel, from where the cooling water is pumped and piped into the funnel. 35 with a draft ratio of 9 to the bobbin after passing through the guide roll.
It was wound up at a speed of m/min. After vacuum-drying this roll for a day and night at room temperature to remove adhering water, approximately
Bundle 500 pieces into a sheet (thickness: approx. 2 mm, width: approx. 150 mm)
mm), and roll this sheet material with a roll gap of 0.2 mm.
A reinforced rubber composition (masterbatch) was obtained by rolling the material about 10 times with a pair of rolling rolls at a temperature of 60°C. Fractionation and graft ratio measurement 2 g of the reinforced rubber composition obtained in Example 1 was added to 200 ml of benzene at room temperature to dissolve the rubber content in the reinforced rubber composition, and the resulting slurry was centrifuged at room temperature to dissolve the divided into a precipitated portion and a precipitated portion. After repeating the above operation seven times for the precipitated portion, the precipitated portion was dried to obtain nylon fibers.
This nylon fiber was dissolved in a mixed solvent of phenol and orthone dichlorobenzene at a ratio of 1:3 (weight ratio), analyzed by ¹ H nuclear magnetic resonance spectroscopy (NMR) (internal standard: tetramethylsilane), and analyzed from an NMR chart. The peaks of the methyl group and methylene group originating from natural rubber, the methylene group adjacent to the CO group originating from 6-nylon, the methylene group adjacent to the NH group, and the other three methylene groups were determined by the cut area method. The graft ratio was calculated by determining the molar ratio of 6-nylon and natural rubber.
In addition, the shape of the nylon fiber was changed to about 200
The book was measured using a scanning microscope at a magnification of 10,000 times. The fibers were extremely thin short fibers with a circular cross section. The results are summarized in Table 1. Evaluation Test The reinforced rubber composition obtained in Example 1 was vulcanized at 150° C. for 40 minutes according to the formulation shown in Table 2, and its physical properties were measured. The results are shown in Table 2. Example 2 30 parts of 6-nylon, 1.93 parts of Novolak A,
The same procedure as in Example 1 was conducted except that 0.193 parts of hexamethylenetetramine and hexamethylenetetramine were used. The results are summarized in Tables 1 and 2. Example 3 40 parts of 6-nylon, 2.10 parts of Novolak A,
The same procedure as in Example 1 was conducted except that 0.21 parts of hexamethylenetetramine and hexamethylenetetramine were used. The results are summarized in Tables 1 and 2. Example 4 70 parts of 6-nylon, 2.55 parts of Novolak A,
The same procedure as in Example 1 was conducted except that 0.255 parts of hexamethylenetetramine and hexamethylenetetramine were used. The results are summarized in Tables 1 and 2. Example 5 The same procedure as in Example 1 was carried out except that 0.75 part of Novolak A and 0.075 part of hexamethylenetetramine were used. The results are summarized in Tables 1 and 2.
Shown in the table. Example 6 The same procedure as in Example 1 was carried out except that 1.88 parts of Novolak A and 0.188 parts of hexamethylenetetramine were used. The results are summarized in Tables 1 and 2.
Shown in the table. Comparative Example 1 The same procedure as Example 1 was carried out except that Novolak A and hexamethylenetetramine were not added. The results are summarized in Tables 1 and 2. Example 7 The same procedure as in Example 1 was carried out except that Novolac B was used in place of Novolac A. The results are summarized in Tables 1 and 2. Example 8 An example was carried out in the same manner as in Example 1, except that Novolac C was used in place of Novolac A. The results are summarized in Tables 1 and 2. Example 9 α-polyoxymethylene (n>100, manufactured by Katayama Chemical Industry Co., Ltd.) was used instead of hexamethylenetetramine.
The same procedure as in Example 1 was carried out except that 0.225 part was used.
Others are summarized in Tables 1 and 2. Example 10 100 parts of NR in a Brabender plastograph set at 220°C and 50 rpm.
After masticating for 30 seconds, 50 parts of 6-nylon (1030B) was added, and after kneading for 4 minutes, 0.75 parts of Novolak A was added. After kneading for 1 minute, 0.075 parts of hexamethylenetetramine was added. , kneading for 2 minutes (during this time, the temperature inside the Brabender rose to 230℃)
Then, 0.75 part of Novolak A was added, and after kneading for 1 minute, 0.075 part of hexamethylenetetramine was added, and after kneading for 2 minutes (the temperature in the Brabender during this time was 230°C), 0.75 part of Novolak A was added. , after kneading for 1 minute, hexamethylenetetramine
0.075 part was added and kneaded for 2 minutes (the temperature inside the Brabender during this time was 230°C). The obtained kneaded product was extruded, wound and rolled in the same manner as in Example 1 to obtain a reinforced rubber composition. The results are summarized in Tables 1 and 2. Example 11 100 parts of NR and Notsukrak G- were placed in a Banbury mixer (manufactured by Minamisenju) set at 150°C and 150 rpm.
After masticating for 1 minute, 50 parts of 6-nylon (1030B) was added and kneaded for 4 minutes. During this time, the temperature inside the mixer rose to 230℃, and 6-
The nylon was melted. Next, 2.25 parts of Novolak A was added and kneaded for 7 minutes, and then 0.225 parts of hexamethylenetetramine was added and kneaded for 2.5 minutes (during which time the temperature inside Banbury was 230°C). The obtained kneaded product was extruded, wound and rolled in the same manner as in Example 1 to obtain a reinforced rubber composition. The results are summarized in Tables 1 and 2. Note that during 6 hours of continuous extrusion and winding, the extrudate did not break even once. The fiber length of the nylon fibers embedded in the reinforced rubber compositions obtained in each example was approximately
It was less than 200μ (according to calculated values).

【table】

【table】

[Table] The stress-strain curve of the vulcanizates obtained from each of the reinforced rubber compositions of Examples 1 to 11 has a smooth "inverted S-shape"
It was hot. In contrast, the stress-strain curve of the vulcanizate obtained from the reinforced rubber composition of Comparative Example 1 shows a strain of 50
Wave-like disturbances occurred from around %. Further, the physical properties of the vulcanizates obtained from the reinforced rubber compositions of Example 1, Example 7, Example 8, and Comparative Example 1 were measured. Pico wear test
Fatigue test in air at 100°C according to ASTM D2228
50% modulus retention and tensile rupture strength retention after being stretched 1×10 ⁴ times at a constant load of 3 kg/cm ² [(value after fatigue test/fatigue test)] (previous value) x 100, %], and the number of times it was pulled until tensile breakage (fatigue life) was determined at a constant load of 50 kg/cm ² . The results are shown in Table 4.

[Table] (A): Vulcanization time of the composition: 40 minutes (B): Vulcanization time of the composition: 30 minutes The results shown in Table 3 show that the reinforced rubber composition of the present invention was This shows that a vulcanizate with extremely excellent properties can be obtained.

Claims (1)

[Scope of Claims] 1 (a) 100 parts by weight of vulcanizable rubber; (b) fiber length of a thermoplastic polymer having -CONH- groups in the polymer molecule and having a melting point of 190 to 235°C; 1 to 100 parts by weight of fine fibers having an average fiber diameter of 3 μm or more and 0.05 to 0.8 μm are embedded,
and (c) a reinforced rubber composition in which the polymer and vulcanizable rubber are grafted at the interface of the fibers via an initial condensate of a novolac type phenol formaldehyde resin, and the grafting ratio is 3% or more. thing. 2 (a) in a vulcanizable rubber; (b) in a polymer molecule with a molecular weight of less than 200,000 -
Total amount of a thermoplastic polymer having a CONH- group and a melting point of 190 to 235°C, and (c) these rubber thermoplastic polymers.
0.2 to 5 parts by weight per 100 parts by weight of an initial condensate of a novolak type phenol formaldehyde resin, and (d) a compound capable of generating formaldehyde when heated, at a temperature equal to or higher than the melting point of the thermoplastic polymer and at 270°C.
(a) When the ratio of rubber and thermoplastic polymer in the kneaded product is 1 to 100 parts by weight of thermoplastic polymer per 100 parts by weight of rubber, (b) If the proportion of rubber and thermoplastic polymer in the kneaded mixture is more than 1 part by weight of thermoplastic polymer per 100 parts by weight of rubber, add additional vulcanizable rubber to the heat per 100 parts by weight of total rubber. Add the kneaded material so that the plastic polymer is 1 to 100 parts by weight,
A method for producing a reinforced rubber composition, characterized by extruding at a temperature of 270° C. or lower, and stretching the extrudate at a temperature lower than the melting point of the thermoplastic polymer.