JP2013072024A - Rubber composite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composite excellent in resistance to compression.SOLUTION: The rubber composite is made by using a para-type wholly aromatic polyamide fiber as a reinforcing material and the para-type wholly aromatic polyamide fiber has a single yarn fineness of 10-50 dtex and a fiber length of not shorter than 30 mm, and the content of the para-type wholly aromatic polyamide fiber is 1-30 mass%.

Description

  The present invention relates to a rubber composite using para-type wholly aromatic polyamide fiber as a reinforcing material.

Conventionally, para-type wholly aromatic polyamide fibers mainly composed of an aromatic dicarboxylic acid component and an aromatic diamine component have characteristics such as high strength, high elastic modulus, and high heat resistance. Widely used.
Also in the field of reinforced rubber, para-type wholly aromatic polyamide fibers are suitably used (see Patent Document 1) and have responded to demands such as heat aging resistance. However, the para-type wholly aromatic polyamide fiber has a high tensile strength but a low compressive strength, so that there is a problem that a rubber composite having a sufficiently satisfactory compression resistance cannot be obtained.

  Therefore, for the purpose of improving the compressive strength of the resulting rubber composite, a wholly aromatic polyamide fiber is impregnated with a resin composition that is cured by ionizing radiation and / or a resin composition that is cured by heating, and the composition is B-stage. A method of using it as a reinforcing material after being cured is proposed (see Patent Documents 2 and 3). However, the method of impregnating a composition into a wholly aromatic polyamide fiber and curing it is complicated because the operation for obtaining the reinforcing material is complicated, and therefore a simpler method has been desired.

JP 62-104848 A JP-A-61-007335 JP 61-012980 A

  The present invention has been made against the background of such conventional techniques, and an object of the present invention is to provide a rubber composite excellent in compression resistance.

  The present inventor has intensively studied to solve the above problems. As a result, it has been found that a rubber composite having excellent compression resistance can be obtained by using a specific amount of para-type aromatic polyamide long fibers having a large single yarn fineness as a rubber reinforcing material, and the present invention has been completed. It was.

  That is, the present invention is a rubber composite using para-type wholly aromatic polyamide fiber as a reinforcing material, and the para-type aromatic polyamide fiber has a single yarn fineness of 10 to 50 dtex and a fiber length longer than 30 mm. This is a rubber composite having a fiber content of 5 to 30% by mass.

  The rubber composite using the para-type aromatic polyamide fiber of the present invention as a reinforcing material is excellent in compression resistance. Therefore, the rubber composite of the present invention can be suitably used in a field where compressive strength is required, such as a tire.

Hereinafter, embodiments of the present invention will be described in detail.
<Rubber composite>
The rubber composite of the present invention is one in which a specific amount of a specific para-type wholly aromatic polyamide fiber is blended as a reinforcing material. Below, the component of the rubber composite of this invention, etc. are demonstrated.

[Rubber]
There is no restriction | limiting in particular as rubber | gum used for the rubber composite of this invention, The well-known rubber | gum conventionally used for the fiber reinforced rubber | gum can be used. For example, natural rubber, styrene butadiene rubber, chloroprene rubber, isoprene rubber, ethylene propylene rubber, hydrogenated NBR or other synthetic rubber, or a mixture thereof can be used. In addition, carbon black, vulcanizing agents, vulcanization accelerators, anti-aging agents, inorganic fillers such as zinc white, rubber extender oils, and other rubber chemicals that are added to ordinary rubber compositions are also used as necessary. Can be added.

[Para-type wholly aromatic polyamide fiber]
The para-type wholly aromatic polyamide fiber used in the rubber composite of the present invention means a fiber mainly composed of para-type wholly aromatic polyamide. Here, the “main component” means that the para-type wholly aromatic polyamide is in the range of more than 50% by mass to 100% by mass with respect to the obtained para-type wholly aromatic polyamide fiber. In the present invention, the para-type wholly aromatic polyamide is particularly preferably 100% by mass.

  The para-type wholly aromatic polyamide constituting the fiber used in the rubber composite of the present invention is a polymer in which one or more divalent aromatic groups are directly linked by an amide bond at the para position. is there. As the aromatic group, two aromatic rings may be bonded through oxygen, sulfur, or an alkylene group. Further, these divalent aromatic groups may include a lower alkyl group such as a methyl group or an ethyl group, a halogen group such as a methoxy group, or a chloro group.

  Examples of such para-type wholly aromatic polyamides include polyparaphenylene terephthalamide, copolyparaphenylene 3,4 obtained by copolymerization of a terephthalic acid component, a 3,4′-diaminodiphenyl ether component, and a paraphenylenediamine component. '-Oxydiphenylene terephthalamide, copolyparaphenylene, phenylbenzimidazole, terephthalamide, etc., copolymerized with terephthalic acid component, aromatic diamine component having phenylbenzimidazole skeleton and paraphenidylenediamine component it can. In addition, the para type wholly aromatic polyamide constituting the fiber of the present invention may be used alone or in combination of two or more.

  Furthermore, in the present invention, since it is soluble in an amide solvent or the like, it is excellent in molding processability, and properties such as strength and elastic modulus can be remarkably improved by applying hot stretching. -It is preferable to use oxydiphenylene terephthalamide.

[Physical properties of para-type wholly aromatic polyamide fiber]
The physical properties of the para type wholly aromatic polyamide fiber used in the rubber composite of the present invention will be described.

(Single yarn fineness)
The single yarn fineness of the para-type wholly aromatic polyamide fiber is in the range of 10 to 50 dtex. When the single yarn fineness is less than 10 dtex, a rubber composite having sufficient compression resistance cannot be obtained. The single yarn fineness is preferably 15 dtex or more, and more preferably 20 dtex or more.

(Fiber length)
Moreover, when the fiber length of the para type wholly aromatic polyamide fiber to be used is short, sufficient alignment cannot be performed in the rubber composite, and it becomes difficult to develop uniform compression resistance. For this reason, it is essential that the length of the para-type wholly aromatic polyamide fiber is longer than 30 mm, preferably 40 mm or more, and most preferably 50 mm or more.

(Tensile strength)
The para-type wholly aromatic polyamide fiber used in the rubber composite of the present invention preferably has a tensile strength of 15 cN / dtex or more. A tensile strength of less than 15 cN / dtex is not preferable because a rubber composite having excellent compression resistance cannot be obtained. The tensile strength is more preferably 18 cN / dtex or more, and most preferably 20 cN / dtex or more.

(Initial elastic modulus)
The para type wholly aromatic polyamide fiber used in the rubber composite of the present invention preferably has an initial elastic modulus of 500 cN / dtex or more. When the initial elastic modulus is less than 500 cN / dtex, the rigidity of the yarn is lowered and the compressive strength is lowered, which is not preferable. The initial elastic modulus is more preferably 520 cN / dtex or more, and most preferably 540 cN / dtex or more.

[Content of para-type wholly aromatic polyamide fiber]
The content of the para-type wholly aromatic polyamide fiber in the rubber composite of the present invention is essential to be in the range of 1% by mass to 30% by mass with respect to the mass of the rubber material used, and 3% by mass to The range is preferably 25% by mass, and most preferably in the range of 5% by mass to 20% by mass. If it is less than 1% by mass, it is unsuitable because sufficient compression resistance cannot be obtained, and if it exceeds 30% by mass, a rubber composite cannot be formed, which is unsuitable.

[Method for producing para-type wholly aromatic polyamide]
The para type wholly aromatic polyamide constituting the fiber used in the rubber composite of the present invention can be produced according to a conventionally known method. For example, a polymer solution of an aromatic polyamide can be obtained by reacting an aromatic dicarboxylic acid chloride component and an aromatic diamine component in an amide polar solvent.

[Raw material for para-type wholly aromatic polyamide]
(Aromatic dicarboxylic acid dichloride component)
The aromatic dicarboxylic acid dichloride component used as the raw material for the para-type wholly aromatic polyamide is not particularly limited, and generally known compounds can be used. Examples thereof include terephthalic acid dichloride, 2-chloroterephthalic acid dichloride, 3-methylterephthalic acid dichloride, 4,4′-biphenyldicarboxylic acid dichloride, 2,6-naphthalenedicarboxylic acid dichloride, isophthalic acid dichloride, and the like. Among these, terephthalic acid dichloride is most preferable from the viewpoints of versatility and mechanical properties of the fiber.

  These aromatic dicarboxylic acid dichlorides can be used not only in one type but also in two or more types, and the composition ratio is not particularly limited. In the present invention, a small amount of a component such as isophthalic acid dichloride that forms a bond other than the para position may be contained.

(Aromatic diamine component)
Examples of the aromatic diamine component used as a raw material for the para-type wholly aromatic polyamide include paraphenylene diamine, 3,4′-diaminodiphenyl ether, parabiphenylene diamine, 5-amino-2- (4-aminophenylene) benzimidazole, Examples include 1,4-dichloroparaphenylenediamine, but are not limited thereto. A substituent may be present on the aromatic ring, or other heterocycles may be present.
Moreover, these can use not only one type but 2 or more types, The composition ratio is not specifically limited. In addition, in this invention, components, such as metaphenylenediamine which forms a bond other than para position, may be contained in a small amount.

In the present invention, it is preferable to use copolyparaphenylene-3,4'-oxydiphenylene-terephthalamide as the para-type wholly aromatic polyamide, so that the aromatic diamine component used as the raw material is paraphenylenediamine and 3 , 4′-diaminodiphenyl ether is preferably used in combination.
Although the composition ratio is not particularly limited, the composition of paraphenylene diamine and the composition of 3,4'-diaminodiphenyl ether are 30 to 70 mol% and 70 to 70, respectively, with respect to the total amount of aromatic diamine. It is preferably 30 mol%, more preferably 40 to 60 mol% and 60 to 40 mol%, respectively, most preferably 45 to 55 mol% and 55 to 45 mol%, respectively.

[Raw material composition ratio]
The ratio of the aromatic dicarboxylic acid chloride component to the aromatic diamine component, which is the raw material of the aromatic polyamide, is 0.90 or more and 1.10 or less as the molar ratio of the aromatic dicarboxylic acid chloride component to the aromatic diamine component. The range is preferable, and the range of 0.95 to 1.05 is more preferable. When the molar ratio of the aromatic dicarboxylic acid chloride component is less than 0.90 or exceeds 1.10, the reaction with the aromatic diamine component does not proceed sufficiently and a high degree of polymerization cannot be obtained, which is not preferable.

[Reaction conditions]
The reaction conditions for the aromatic dicarboxylic acid chloride component and the aromatic diamine component are not particularly limited. The reaction between acid chloride and diamine is generally rapid, and the reaction temperature is preferably in the range of −25 ° C. or higher and 100 ° C. or lower, and more preferably in the range of −10 ° C. or higher and 80 ° C. or lower. .

[Polymerization solvent]
Examples of amide solvents used for the production of para-type wholly aromatic polyamides include N-methyl-2-pyrrolidone (hereinafter also referred to as NMP), N, N-dimethylformamide, N, N-dimethylacetamide, dimethylimidazolide. Non etc. are mentioned. These solvents can be used alone or as a mixed solvent of two or more. Note that the solvent used is preferably dehydrated.
In the production of para-type wholly aromatic polyamide, it is most preferable to use N-methyl-2-pyrrolidone (NMP) from the viewpoints of versatility, harmfulness, handleability, solubility in para-type wholly aromatic polyamide, and the like. .

[Neutralization reaction]
After completion of the reaction, it is preferable to carry out a neutralization reaction by adding a basic inorganic compound such as sodium hydroxide, potassium hydroxide, calcium hydroxide, calcium oxide or the like, if necessary.

[Post-polymerization treatment, etc.]
The aromatic polyamide obtained by polymerization can be taken out into a non-solvent such as alcohol or water, precipitated, and taken out in the form of pulp. The extracted aromatic polyamide can be dissolved again in another solvent and then used for fiber molding, but the polymer solution obtained by the polymerization reaction should be used as it is as a spinning solution (dope). Is also possible. The solvent used for taking out once and then dissolving it again is not particularly limited as long as it dissolves the aromatic polyamide. However, the solvent used for the polymerization of the aromatic polyamide described above may be used. It is preferable for the reason.

[Method for producing para-type wholly aromatic polyamide fiber]
In the method for producing para-type wholly aromatic polyamide fibers used in the present invention, first, a spinning solution (polymer dope) containing para-type wholly aromatic polyamide and a solvent is discharged from a spinneret.

(Preparation of spinning solution (polymer dope))
The method for preparing the spinning solution (dope) containing the para-type wholly aromatic polyamide and the solvent is not particularly limited. As the solvent used for the preparation of the spinning solution (dope), it is preferable to use the solvent used for the polymerization of the para-type wholly aromatic polyamide. In addition, the solvent used may be one type alone or a mixed solvent obtained by mixing two or more types of solvents. The polymer can be used as it is without being isolated from the polymer solution obtained by the production of the para-type wholly aromatic polyamide.
Furthermore, an inorganic salt can also be used as a solubilizing agent for the purpose of increasing the solubility of para-type wholly aromatic polyamide in a solvent. Examples of the inorganic salt include calcium chloride and lithium chloride. Although the amount of the inorganic salt added to the polymer dope is not particularly limited, it is 1 to 10% by mass with respect to the polymer dope mass from the viewpoint of the effect of improving the polymer solubility and the solubility of the inorganic salt in the solvent. It is preferable that

Moreover, you may mix | blend other arbitrary components, such as an additive, in the range which does not exceed the summary of this invention in order to provide functionality etc. to a fiber. When an additive or the like is blended, it can be introduced in adjusting the dope. The method of introduction is not particularly limited, and for example, it can be introduced into the dope using a ruder or a mixer.
The polymer concentration in the spinning solution (dope), that is, the concentration of the para-type wholly aromatic polyamide is preferably in the range of 0.5 mass% to 30 mass%. When the polymer concentration in the spinning solution (dope) is less than 0.5% by mass, the entanglement of the polymer is small, so that the viscosity necessary for spinning cannot be obtained, and the ejection stability during spinning decreases. . On the other hand, when the polymer concentration exceeds 30% by mass, the viscosity of the dope increases abruptly, so that the discharge stability at the time of spinning decreases, and stable spinning becomes difficult due to the sudden increase in pressure in the spinning pack. Cheap.

(Spinning and coagulation process)
In the spinning / coagulation step, fibers are formed by a wet method, a semi-dry semi-wet method, or the like. For example, in the semi-dry semi-wet method, a spinning solution (dope) is discharged from a spinneret and solidified in a coagulation bath made of a poor solvent to obtain an undrawn yarn. The spinneret used is not particularly limited in terms of hole diameter, nozzle length, material, etc., as long as the single fiber fineness of the obtained fiber can be in the range of 10 to 50 dtex. It can be adjusted appropriately.
The temperature of the polymer dope when passing through the spinneret and the temperature of the spinneret are not particularly limited, but are preferably 80 to 120 ° C. from the viewpoint of spinnability and polymer dope discharge pressure. .

Next, the polymer dope discharged from the spinneret is solidified in a coagulating liquid. At this time, when the temperatures of the spinneret and the coagulating liquid are greatly different, when the spinneret and the coagulating liquid come into contact with each other, the respective temperatures change, and as a result, it becomes difficult to control the spinning process. Therefore, when the temperatures of the spinneret and the coagulating liquid are greatly different, it is preferable to perform semi-dry semi-wet spinning provided with an air gap. The length of the air gap is not particularly limited, but is preferably in the range of 5 to 15 mm from the viewpoints of temperature controllability, stringiness, and the like.
The coagulating liquid used here is, for example, an NMP aqueous solution, and its temperature and concentration are not particularly limited. As long as there is no problem in the solidified state of the formed yarn and the subsequent process passability, it can be adjusted as appropriate.

(Washing process)
Next, the coagulated yarn obtained above is washed with water. The purpose of the water washing step is to diffuse a solvent such as NMP contained in the yarn into the water and remove the solvent from the yarn. The fibers used in the present invention have a high fineness, but have little variation in the amount of residual solvent from filament to filament, and have the solvent removed at a high level. When the amount of the residual solvent in the yarn after passing through the water washing step is high, it is not preferable because the step passability in the subsequent step, the physical properties and quality of the obtained fiber are deteriorated.

In addition, since a fiber bundle passes continuously in a washing process, there exists a problem which the solvent concentration of a washing bath becomes high by it. For this reason, it is preferable to constantly supply water containing no solvent and keep the solvent concentration in the washing bath constant.
It is preferable to apply inorganic fine particles to the yarn after washing for the purpose of suppressing fusion of single fibers in the subsequent drying step and heat drawing step. The kind and adhesion amount of the inorganic fine particles to be imparted are not particularly limited as long as fusion between single fibers can be suppressed. In addition, the inorganic fine particles attached here can be removed by spraying a water shower or compressed air in the removing step after the hot stretching step.

(Drying process)
Next, in the drying step, the fiber from which the solvent has been removed is dried. The drying conditions are not particularly limited, and there is no problem as long as moisture attached to the fibers can be sufficiently removed. However, in consideration of workability and deterioration of the fibers due to heat, the temperature is in the range of 150 to 250 ° C. It is preferable. For drying, either a contact type drying apparatus such as a roller or a non-contact type drying apparatus such as passing a fiber through a drying furnace can be used.

(Heat drawing process)
Next, the dried fiber is hot-drawn. The purpose of this step is to highly orient the polymer molecules in the fiber and impart strength by hot drawing of the fiber. The heat stretching temperature at this time is preferably in the range of 300 to 600 ° C, more preferably 320 ° C to 580 ° C, and most preferably 350 to 550 ° C. When the heat drawing temperature is less than 300 ° C., the yarn cannot be sufficiently drawn, which is not preferable. On the other hand, when the temperature exceeds 600 ° C., the polymer is thermally decomposed, so that the fiber is deteriorated and it is difficult to obtain a high-strength yarn.
The draw ratio in the hot drawing step is preferably 5 to 15 times, but is not particularly limited to this range. Further, this hot stretching process may be performed in multiple stages as required, and there is no problem.

[Particle removal]
Next, when inorganic fine particles are provided in advance for the purpose of suppressing fusion between single fibers, it is preferable to remove them. Removal of inorganic fine particles can be omitted if necessary, but inorganic fine particles affect the hue of the fiber and cause scum, so remove excessively attached ones. It is preferable to do.
The removal method is not particularly limited, but excess inorganic fine particles can be removed by spraying water shower or compressed air.

(Take-up)
Then, if necessary, an oil agent is applied for the purpose of imparting charge suppression or lubricity to the fiber, and finally wound with a winder. The kind of oil agent to be applied, the amount to be applied, and the like are not particularly limited, and a known method can be applied as it is. Also, the winding method with a winder is not particularly limited, and the winding can be performed by appropriately adjusting the winding conditions using a known winder.

(cut)
The para type wholly aromatic polyamide fiber used in the present invention may be cut as long as it is longer than 30 mm. The cutting method is not particularly limited, and a known method can be adopted. For example, the method etc. which cut a fiber into predetermined fiber length using a guillotine cutter and a rotary disc cutter are mentioned.

<Method for making rubber composite>
As a method for producing the rubber composite, a known method can be used. For example, there is a method in which reinforcing long fibers are aligned and arranged on a plate of a rubber composition to be used, and the rubber composition is further poured thereon to obtain a rubber composite. Alternatively, a method of kneading a composition containing a cut para-type wholly aromatic polyamide fiber into a rubber composition as a matrix to obtain a final rubber composite, or including a cut para-type wholly aromatic polyamide fiber Examples thereof include a method in which a composition is prepared in advance and mixed with a small amount of a rubber composition to obtain a final rubber composite.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and the like, but the present invention is not limited to these unless it exceeds the gist.

<Measurement and evaluation method>
In Examples and Comparative Examples, the following items were measured and evaluated by the following methods.
(1) Compressive strength Measured according to JIS K7208, and the value at a distortion rate of 20% was determined.
(2) Fineness of fiber The obtained fiber was wound up by 100 m using a known measuring instrument, and its mass was measured. A value obtained by multiplying the obtained mass by 100 was calculated as a fineness (dtex) per 10,000 m.
(3) Tensile strength and initial elastic modulus of fiber Using a tensile tester (manufactured by INSTRON, trade name: INSTRON, model: 5565 type), using a yarn test chuck, based on the procedure of ASTM D885, under the following conditions Measurements were performed.
[Measurement condition]
Temperature: Room temperature Test piece: 75cm
Test speed: 250 mm / min Chuck distance: 500 mm

<Example 1>
[Production of para-type wholly aromatic polyamide]
50 parts by mass of paraphenylenediamine and 50 parts by mass of 3,4'-diaminodiphenyl ether are dissolved in NMP, and 100 parts by mass of terephthalic acid dichloride is added thereto, and a polycondensation reaction is performed. -A polymer solution (dope) of oxydiphenylene terephthalamide was obtained. At this time, the polymer concentration was 6% by mass, and the intrinsic viscosity (IV) of the polymer was 3.38.

[Production of para-type wholly aromatic polyamide fiber]
A spinneret with a hole diameter of 0.8 mm and a hole number of 200 was heated to 105 ° C., and then the polymer solution (dope) obtained above was heated to 105 ° C. and discharged through an air gap of 10 mm. By passing through a coagulation bath filled with 30% by mass of a 60 ° C. aqueous solution, a fiber bundle in which the polymer was coagulated was obtained.
Next, the coagulated fiber bundle was passed through a water washing bath adjusted to 60 ° C., and washed with water.
Subsequently, 2% by mass of talc and osmos was adhered to the mass of the fiber for the purpose of suppressing the fusion of the single yarns in the drying step and the heat drawing step.
The fiber to which talc and osmos were adhered was dried with a 200 ° C. drying roller, and then the first stage of thermal stretching was performed at 380 ° C. The draw ratio at this time was 2.4 times. Subsequently, the second stage of thermal stretching was performed at 530 ° C. The draw ratio at this time was 4 times.
Finally, the drawn fiber was wound around a paper tube with a winder to obtain a para-type wholly aromatic polyamide fiber having a single yarn fineness of 20 dtex. Table 1 shows the physical properties of the obtained fiber.
Subsequently, the obtained para-type wholly aromatic polyamide fiber was cut into 50 mm using a guillotine cutter.

[Create rubber composite]
The para-type wholly aromatic polyamide fibers having a fiber length of 50 mm obtained above are aligned on a plate of SBR rubber (JSR1506) and arranged in parallel. To obtain a rubber composite. At this time, the content of the para-type wholly aromatic polyamide fiber in the rubber composite was set to 5% by mass. Table 1 shows the compressive strength of the obtained rubber composite.

<Example 2>
A rubber composite was prepared in the same manner as in Example 1 except that the content of the para-type wholly aromatic polyamide fiber in the rubber composite was 30% by mass. Table 1 shows the compressive strength of the obtained rubber composite.

<Comparative Example 1>
A rubber composite was prepared in the same manner as in Example 1 except that the single yarn fineness of the para-type wholly aromatic polyamide fiber was 1.67 dtex and the fiber length was 40 mm. Table 1 shows the compressive strength of the obtained rubber composite.

<Comparative example 2>
A rubber composite was prepared in the same manner as in Example 1 except that the fiber length of the para-type wholly aromatic polyamide fiber was 10 mm. Table 1 shows the compressive strength of the obtained rubber composite.

<Comparative Example 3>
A rubber composite was prepared in the same manner as in Example 1 except that the fiber length of the para-type wholly aromatic polyamide fiber was 40 mm and the content in the rubber composite was 0.5 mass%. Table 1 shows the compressive strength of the obtained rubber composite.

  Since the rubber composite of the present invention is excellent in compression resistance, it is very useful in fields where compression strength is required, such as tires.

Claims (4)

A rubber composite using para-type wholly aromatic polyamide fiber as a reinforcing material,
The para-type wholly aromatic polyamide fiber has a single yarn fineness of 10 to 50 dtex, a fiber length longer than 30 mm,
A rubber composite having a content of the para-type wholly aromatic polyamide fiber of 1 to 30% by mass. A rubber composite having a compressive strength of 25 to 60 kN / m ² when 20% strain is applied in a compressive strength measurement according to JIS K7208.   The rubber composite according to claim 1 or 2, wherein the para-type wholly aromatic polyamide fiber has a tensile strength of 15 cN / dtex or more and an initial elastic modulus of 500 cN / dtex or more.   The rubber composite according to any one of claims 1 to 3, wherein the para-type wholly aromatic polyamide fiber is copolyparaphenylene 3,4'-oxydiphenylene terephthalamide.