JP2017020125A - Short fiber for rubber reinforcement and transmission belt by blending the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a short fiber for rubber reinforcement which is manufactured by cutting an alicyclic polyamide fiber, suppresses flexure heat generating with good adhesive force between rubber and various members while maintaining strength of rubber itself good even under high temperature environment, and can enhance durability of a belt used under high load, high flex and high temperature environment.SOLUTION: There are provided a short fiber for rubber reinforcement manufactured by cutting an alicyclic polyamide fiber, a short fiber reinforced rubber by blending the short fiber for rubber reinforcement of 5 pts.wt. to 80 pts.wt. and a transmission belt using the short fiber for rubber reinforcement for a compression layer.SELECTED DRAWING: None

Description

  The present invention relates to a short fiber for reinforcing rubber, and a transmission belt made of a short fiber reinforced rubber in which a predetermined amount of the short fiber is blended and used under a high temperature and high load environment.

In automobile internal combustion engines and the like, transmission belts are widely used for power transmission. In recent years, transmission belts are increasingly used in high-temperature and high-load environments due to the increasing use environment and narrowing of the use environment due to the downsizing of engines and the like.
Conventionally, short fibers and the like have been blended with compressed rubber so that the transmission belt has good durability under a high load environment. In order to increase the lateral pressure resistance of the belt, a rubber having a relatively high modulus due to the orientation effect of the short fibers is used for the compressed rubber. Patent Document 1 below discloses blending aramid short fibers and the like into a rubber composition forming a compressed rubber layer of a V-belt.
Furthermore, in the case of a toothed belt with a toothed compression rubber layer, the internal heat generation amount increases under a high-temperature environment, so that heat deterioration tends to occur, and the rubber and canvas of the tooth base part are repeatedly stretched greatly, Cracks are easily generated. Patent Documents 2 and 3 below disclose adding an adhesive component to a tooth rubber containing short fibers in order to improve durability.
In addition, the power transmission portion has been made compact with the downsizing of automobiles, and a pulley with a small diameter has been included, the amount of bending deformation of the belt has been further increased, and the demand for bending resistance has increased.

JP 2004-125164 A JP 2013-108564 A JP 2008-261489 A

The demand level for durability of power transmission belts in the market has increased in recent years. Therefore, the durability can be increased to the required level only by using high-strength rubber and short fibers and prescribing an adhesive. It's getting harder.
Further, when the compression rubber layer of the transmission belt has a high modulus, the adhesion to canvas and short fibers and the rubber strength at high temperatures tend to be lowered. Furthermore, as disclosed in Patent Document 2 or 3, when a resorcin formalin resin or a melamine resin is added to an adhesive rubber, the adhesive strength can be improved, but the tear strength of the rubber itself is reduced, and there is a lack of teeth and Cracks and the like may easily occur.

  In view of the present state of the art, the problem to be solved by the present invention is to suppress bending heat generation while maintaining the adhesive strength between rubber and various members while maintaining the strength of the rubber itself even in a high temperature environment, and high load.・ Provides short fibers for rubber reinforcement that can improve the durability of belts used in high bending and high temperature environments, short fiber reinforced rubber containing a certain amount of this, and transmission belts made of rubber reinforced with short fibers. It is to be.

As a result of intensive studies and repeated experiments to solve the above problems, the inventors of the present application have developed a transmission rubber containing a predetermined amount of short fibers made of alicyclic polyamide fibers having a specific composition and specific viscoelastic properties. The present inventors have found that the above problems can be solved and have completed the present invention.
That is, the present invention is as follows.

[1] A rubber reinforcing short fiber obtained by cutting an alicyclic polyamide fiber.
[2] The rubber reinforcing short fiber according to [1], wherein the alicyclic polyamide fiber has a melting point of 270 ° C. or higher.
[3] The short fiber for reinforcing rubber according to [1] or [2], wherein the alicyclic polyamide fiber has a birefringence of 0.030 to 0.070.
[4] The rubber reinforcing short fiber according to any one of [1] to [3], wherein the cut length of the rubber reinforcing short fiber is 0.5 mm to 10 mm.
[5] The rubber reinforcing short fiber according to any one of [1] to [4], wherein the single yarn fineness of the rubber reinforcing short fiber is 0.5 dtex to 10 dtex.
[6] The rubber reinforcing short fiber according to any one of [1] to [5], wherein 1 to 15 parts by weight of resorcin-formalin-latex (RFL) is attached.
[7] Any of [1] to [6] above, wherein in the dynamic viscoelasticity measurement of the alicyclic polyamide fiber, the maximum value of the loss tangent tan δ between 0 ° C. and 140 ° C. is 0.100 or less. The short fiber for rubber reinforcement described in 1.
[8] The alicyclic polyamide fiber is a polyamide multifilament fiber comprising a polycondensate of a dicarboxylic acid containing an alicyclic dicarboxylic acid and a diamine, and the following requirements:
(A) The ratio of the alicyclic dicarboxylic acid to the dicarboxylic acid is 50 mol% or more;
(B) the total fineness of the polyamide multifilament fiber is 100 dtex or more; and (c) the cross ratio (maximum diameter / minimum diameter) of the polyamide multifilament fiber is 1.7 or less;
The short fiber for reinforcing rubber according to any one of [1] to [7], wherein
[9] The rubber reinforcing short fiber according to [8], wherein the polyamide multifilament fiber has a sulfuric acid relative viscosity of 1.5 or more and 4.0 or less.
[10] The polyamide multifilament fiber contains 1,10-decanediamine as a diamine component, and the ratio of the 1,10-decanediamine to the whole diamine component is 20 mol% or more. [8] Or the short fiber for rubber reinforcement as described in [9].
[11] The polyamide multifilament fiber contains a diamine having 5 or 6 carbon atoms as a diamine component, and the ratio of the diamine having 5 or 6 carbon atoms to the entire diamine component is 20 mol% or more. The short fiber for rubber reinforcement according to any one of [8] to [10].
[12] The rubber reinforcing short fiber according to [11], wherein the diamine having 5 or 6 carbon atoms is 2-methylpentamethylenediamine.
[13] The rubber reinforcing short fiber according to [11], wherein the diamine having 5 or 6 carbon atoms is hexamethylenediamine.
[14] A short fiber reinforced rubber in which the rubber reinforcing short fibers according to any one of [1] to [13] are blended in an amount of 5 to 80 parts by weight.
[15] A power transmission belt using the short fiber reinforced rubber according to [14] as a compression layer.

  The short fiber according to the present invention is excellent in rubber adhesion and has a characteristic that bending energy loss is small from room temperature to high temperature. Therefore, if this short fiber is blended with rubber, it will become a rubber that does not lose its durability due to bending heat of the rubber, and if it is used for the compression rubber layer of the transmission belt, it will endure under high load, high bending, and high temperature environment. It is possible to provide a transmission belt with improved performance.

It is a perspective view of a V-ribbed belt cross section. FIG. 5 is a layout diagram of pulleys in a heat and durability belt running test.

Hereinafter, embodiments of the present invention will be described in detail.
The present embodiment is a rubber reinforcing short fiber obtained by cutting an alicyclic polyamide fiber.
In this specification, the term “alicyclic polyamide fiber” refers to a polyamide multifilament fiber made of a polycondensate of a dicarboxylic acid containing an alicyclic dicarboxylic acid and a diamine. In the alicyclic polyamide, the polymer skeleton is not rigid and is solidified from a molten state in which the molecule moves flexibly, and the amide group and terminal group which are adhesive functional groups can be coordinated on the fiber surface. Therefore, it is excellent in rubber adhesiveness, and sufficient adhesion durability can be obtained by conventional adhesive treatment.

Hereinafter, the polymer composition of the alicyclic polyamide fiber of this embodiment will be described.
[Dicarboxylic acid]
The polyamide multifilament fiber of this embodiment is a polyamide multifilament fiber made of a polycondensate of a dicarboxylic acid containing an alicyclic dicarboxylic acid and a diamine. The ratio of alicyclic dicarboxylic acid to dicarboxylic acid is preferably 50 mol% or more, more preferably 60 mol% or more, still more preferably 70 mol% or more, and even more preferably 80 mol% or more. Most preferably, it is 100 mol%. By including at least 50 mol% or more of structural units derived from alicyclic dicarboxylic acid, a polyamide multifilament fiber excellent in high temperature loss loss tangent tan δ peak, fiber strength, and spinnability can be obtained.

The alicyclic dicarboxylic acid is not limited to the following. For example, the alicyclic dicarboxylic acid having 3 to 10 carbon atoms in the alicyclic structure, preferably 5 to 10 carbon atoms in the alicyclic structure. The alicyclic dicarboxylic acid which is is mentioned. Specific examples include, but are not limited to, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, and the like.
The alicyclic dicarboxylic acid may be unsubstituted or may have a substituent. Examples of the substituent include, but are not limited to, for example, 1 to 4 carbon atoms such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, and tert-butyl group. Of the alkyl group.
As the alicyclic dicarboxylic acid, 1,4-cyclohexanedicarboxylic acid is preferable from the viewpoints of heat resistance, dimensional stability, strength and the like of the polyamide multifilament fiber.
One type of alicyclic dicarboxylic acid may be used alone, or two or more types may be used in combination.

  An alicyclic dicarboxylic acid has a trans isomer and a cis geometric isomer. For example, 1,4-cyclohexanedicarboxylic acid as a raw material monomer may use either a trans isomer or a cis isomer, or may be used as a mixture in various ratios of a trans isomer and a cis isomer. 1,4-Cyclohexanedicarboxylic acid is isomerized at a high temperature to have a certain ratio, and the cis isomer has higher water solubility in the equivalent salt with diamine than the trans isomer. The body ratio, that is, the molar ratio of trans isomer / cis isomer is preferably 50/50 to 0/100, more preferably 40/60 to 10/90, and still more preferably 35/65 to 15/85. It is. Due to the trans isomer ratio being within the above range, polyamides not only have excellent properties of high melting point, toughness, and strength, but also have a high glass transition temperature and fluidity, which is usually opposite to heat resistance. And high crystallinity can be satisfied at the same time. The molar ratio of the trans form / cis form of 1,4-cyclohexanedicarboxylic acid can be determined by liquid chromatography (HPLC) or nuclear magnetic resonance spectroscopy (NMR).

  Examples of dicarboxylic acids other than alicyclic dicarboxylic acids include, but are not limited to, for example, malonic acid, dimethylmalonic acid, succinic acid, 2,2-dimethylsuccinic acid, 2,3-dimethylglutaric acid, 2,2-diethylsuccinic acid, 2,3-diethylglutaric acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, suberic acid, azelaic acid, sebacine Examples thereof include linear or branched aliphatic dicarboxylic acids having 3 to 20 carbon atoms such as acid, dodecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, octadecanedioic acid, eicosanedioic acid, and diglycolic acid.

Moreover, you may add aromatic dicarboxylic acid to the said dicarboxylic acid in the range which does not inhibit the fluidity | liquidity of polyamide, ie, the ratio of aromatic dicarboxylic acid with respect to dicarboxylic acid is 0 mol% or more and 10 mol% or less. Examples of the aromatic dicarboxylic acid include, but are not limited to, for example, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, 5-methylisophthalic acid, 5-sodium Examples thereof include aromatic dicarboxylic acids having 8 to 20 carbon atoms which are unsubstituted or substituted with various substituents such as sulfoisophthalic acid.
If the ratio of the alicyclic dicarboxylic acid to the dicarboxylic acid is at least 50 mol% or more, a dicarboxylic acid other than those described above may be included as long as the desired effects are not impaired.

[Diamine]
The polyamide multifilament fiber of this embodiment contains 1,10-decamethylenediamine as a diamine component from the viewpoint of spinning stability, heat resistance, and low water absorption, and the ratio of 1,10-decamethylenediamine to diamine is It is preferable that it is 20 mol% or more. The ratio of 1,10-decamethylenediamine to diamine is preferably 20 mol% or more, more preferably 30 mol% or more and 80 mol% or less, further preferably 40 mol% or more and 75 mol% or less, and still more preferably 45 mol%. % Or more and 70 mol% or less.
When the melting point is too high due to the composition, the polyamide is thermally decomposed at the time of melting, resulting in a decrease in molecular weight and strength, coloring, and mixing of decomposition gas, resulting in poor spinnability. However, by including 20 mol% or more and 80 mol% or less of 1,10-decamethylenediamine, the melting point suitable for melt spinning can be suppressed while maintaining the loss tangent tan δ peak temperature high. Moreover, since the polyamide containing 1,10-decamethylenediamine has high thermal stability at the time of melting, a multifilament fiber having excellent spinning stability and good uniformity can be obtained. Moreover, the thread | yarn which is excellent in the dimensional stability at the time of water absorption can be obtained because the amide group density | concentration in polyamide falls. Furthermore, 1,10-decamethylenediamine is also preferable from the viewpoint that it is a biomass-derived raw material.

The diamine other than 1,10-decamethylenediamine is not particularly limited, and may be an unsubstituted linear aliphatic diamine, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl. A branched aliphatic diamine having a substituent such as an alkyl group having 1 to 4 carbon atoms such as a tert-butyl group or an alicyclic diamine may be used.
Examples of diamines other than 1,10-decamethylenediamine include, but are not limited to, ethylenediamine, propylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, Non-methylene diamine, decamethylene diamine, undecamethylene diamine, dodecamethylene diamine, tridecamethylene diamine and other linear aliphatic diamines, 2-methylpentamethylene diamine, 2,2,4-trimethylhexamethylene diamine, 2-methyl Examples include octamethylenediamine, 2,4-dimethyloctamethylenediamine, 1,4-cyclohexanediamine, 1,3-cyclohexanediamine, and 1,3-cyclopentanediamine.

  Moreover, you may add aromatic diamine to diamine in the range which does not inhibit the fluidity | liquidity of polyamide, ie, the ratio of aromatic diamine with respect to diamine is 0 mol% or more and 10 mol% or less. The aromatic diamine is a diamine containing an aromatic, and is not limited to the following, and examples thereof include metaxylylenediamine, orthoxylylenediamine, and paraxylylenediamine.

As the diamine other than 1,10-decamethylenediamine, a diamine having 5 to 6 carbon atoms and a ratio of the diamine having 5 to 6 carbon atoms being 20 mol% or more is more preferable. By copolymerizing a diamine having 5 to 6 carbon atoms in addition to 1,10-decamethylenediamine, a polymer having high crystallinity can be obtained while maintaining an appropriate melting point suitable for spinning. Examples of the diamine having 5 to 6 carbon atoms include pentamethylenediamine, hexamethylenediamine, 2-methylpentamethylenediamine, 2,5-dimethylhexanediamine, and 2,2,4-trimethylhexamethylenediamine.
Among the diamines having 5 to 6 carbon atoms, 2-methylpentamethylenediamine is preferable from the viewpoint of spinnability, fluidity, and strength. If the ratio of 2-methylpentamethylenediamine is too high, 2-methylpentamethylenediamine is self-cyclized and decomposes when melted, causing a decrease in molecular weight, resulting in poor spinnability and strength. The ratio of 2-methylpentamethylenediamine in the diamine needs to be set in a range where decomposition is not caused at the time of melting while ensuring fluidity, preferably 20 mol% or more and 70 mol% or less, more preferably It is 20 mol% or more and 60 mol% or less, More preferably, it is 20 mol% or more and 55 mol% or less. Among the diamines having 5 to 6 carbon atoms, hexamethylene diamine is preferable from the viewpoint of heat resistance of the polyamide multifilament fiber. If the ratio of hexamethylenediamine is too high, the melting point becomes too high and spinning becomes difficult, so the ratio of hexamethylenediamine in the diamine is preferably 20 mol% or more and 60 mol% or less, more preferably 20 mol. % To 50 mol%, more preferably 20 mol% to 45 mol%.

  The addition amount of the dicarboxylic acid and the addition amount of the diamine are preferably around the same molar amount in order to increase the molecular weight. The amount of diamine escaped from the reaction system during the polymerization reaction is also considered in terms of molar ratio, and the total amount of diamine is 0.90 to 1.20 compared to the total amount of 1.00 of dicarboxylic acid. Preferably, it is 0.95 to 1.10, more preferably 0.98 to 1.05.

[Lactam and / or aminocarboxylic acid]
The polyamide multifilament fiber used for rubber reinforcement of the present embodiment may contain a component derived from lactam and / or aminocarboxylic acid as long as desired effects are not impaired.
Examples of the lactam include, but are not limited to, butyrolactam, pivalolactam, ε-caprolactam, caprylolactam, enantolactam, undecanolactam, laurolactam (dodecanolactam).
The aminocarboxylic acid is not limited to the following, but is preferably, for example, a linear or branched saturated aliphatic carboxylic acid having 4 to 14 carbon atoms substituted with an amino group at the ω position. -Aminocaproic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid and the like can be mentioned, and examples of the aminocarboxylic acid include paraaminomethylbenzoic acid.
The component ratio derived from the lactam and / or aminocarboxylic acid is not particularly limited, but the ratio derived from the lactam and / or aminocarboxylic acid component to the structural unit derived from the raw material monomer component is 0 mol% or more and 20 mol. % Or less, more preferably 2 mol% or more and 15 mol% or less. When the ratio derived from the lactam and / or aminocarboxylic acid component is 0 mol% or more and 20 mol% or less, a polyamide multifilament fiber excellent in heat resistance, spinnability, and strength can be obtained.

[End sealant]
When polymerizing a polyamide from a dicarboxylic acid and a diamine, a known end-capping agent can be further added to adjust the molecular weight. Examples of the end-capping agent include monocarboxylic acids, monoamines, acid anhydrides such as phthalic anhydride, monoisocyanates, monoacid halides, monoesters, monoalcohols, and the like, from the viewpoint of thermal stability. Monocarboxylic acid and monoamine are preferable. One type of end capping agent may be used, or two or more types may be used in combination.

The monocarboxylic acid that can be used as the end-capping agent is not particularly limited as long as it has reactivity with an amino group. For example, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid , Aliphatic monocarboxylic acids such as caprylic acid, lauric acid, tridecylic acid, myristic acid, palmitic acid, stearic acid, pivalic acid and isobutyric acid; alicyclic monocarboxylic acids such as cyclohexanecarboxylic acid; benzoic acid, toluic acid, and aromatic monocarboxylic acids such as α-naphthalenecarboxylic acid, β-naphthalenecarboxylic acid, methylnaphthalenecarboxylic acid, and phenylacetic acid.
One kind of monocarboxylic acid as a terminal blocking agent may be used, or two or more kinds may be used in combination.

  The monoamine that can be used as the end-capping agent is not particularly limited as long as it has reactivity with a carboxyl group. For example, methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, Aliphatic monoamines such as decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine and dibutylamine; alicyclic monoamines such as cyclohexylamine and dicyclohexylamine; aromatic monoamines such as aniline, toluidine, diphenylamine and naphthylamine; . Monoamine as a terminal blocking agent may be used alone or in combination of two or more.

[Additive]
For thermal stability in a high temperature and high humidity environment, it is preferable to add a copper compound such that the copper concentration is 1 to 500 ppm relative to the polyamide, more preferably 30 to 500 ppm. By doing so, even if the product of the present invention is left in a high-temperature, high-humidity environment for a long time or exposed to an environment containing a lot of ozone for a long time, the deterioration of mechanical performance is extremely effectively suppressed. The When the copper content is less than 30 ppm, the heat resistant strength retention ratio decreases, and when the added amount exceeds 500 ppm, the strength decreases.
The type of the copper compound is not particularly limited, and for example, an organic copper salt such as copper acetate, or a copper halide such as cuprous chloride or cupric chloride can be preferably used. The copper compound is more preferably used in combination with a metal halide compound. Examples of the metal halogen compound include potassium iodide, potassium bromide, potassium chloride and the like. Preferred combinations in this embodiment are cuprous iodide and potassium iodide, and copper acetate and potassium iodide. The copper content in the polyamide can be measured by an atomic absorption method or a colorimetric method.

  Although not particularly limited, as stabilizers, organic antioxidants such as hindered phenol antioxidants, sulfur antioxidants, phosphorus antioxidants, heat stabilizers, hindered amines, benzophenones, imidazoles, etc. You may add a light stabilizer, a ultraviolet absorber, etc. The addition amount should just select an appropriate quantity, but 1-1000 ppm can be added with respect to polyamide. These additives may be used alone or in combination of several kinds.

[Degree of polymerization]
From the viewpoints of mechanical properties such as high elongation and spinnability, the polyamide multifilament fiber has a sulfuric acid relative viscosity (ηr) of 1.5% or more at a concentration of 1% in 98% sulfuric acid measured in accordance with JIS-K6810 at 25 ° C. 4.0 or less, preferably 1.7 or more and 3.5 or less, more preferably 1.8 or more and 3.3 or less. If ηr is 1.5 or more, fibers having stable mechanical properties can be easily obtained, and the rubber reinforcing effect can be easily made uniform. Moreover, if ηr is 4.0 or less, fibers having a uniform single yarn fineness are easily obtained, and the rubber reinforcing effect is stabilized. If attention is paid to the moisture content of the polymerized polymer so that it does not depolymerize during melting, it is possible to maintain the polymerization degree of the polymerized polymer and to make fibers.

[Dynamic viscoelasticity]
In the alicyclic polyamide fiber of this embodiment, MAXtan δ (0/140), which is the maximum value of the loss tangent tan δ between 0 ° C. and 140 ° C., is 0.100 or less in the evaluation of dynamic viscoelasticity. preferable. More preferably, it is 0.080 or less, More preferably, it is 0.050 or less. If the value of the loss tangent tan δ is 0.100 or less in the entire range from 0 ° C. to 140 ° C., the loss tangent tan δ of the short fiber-blended rubber is low in the belt operating range from room temperature to high temperature, and rubber heat generation is suppressed. For this reason, the bending durability up to a high temperature is improved. Therefore, a decrease in belt running life during high temperature operation relative to normal temperature operation is suppressed.
MAXtan δ (0/140) is preferably 0.005 or more in order to obtain an alicyclic polyamide fiber by melt spinning and have molecular chain flexibility.
As described above, MAXtanδ (0/140) of alicyclic polyamide fiber has a polymer composition design such as increasing the loss tangent tanδ peak depending on the composition, and lowering the value of the tanδ peak on the low temperature side. Can be lowered.

  The alicyclic polyamide fiber of the present embodiment preferably has a melting point of 270 ° C. or higher. In a polymer design in which the loss tangent tan δ peak is increased in temperature, the melting point of the polymer tends to increase. If the melting point of the fiber is 270 ° C. or higher, it contributes to lowering MAXtan δ (0/140). On the other hand, the melting point of the alicyclic polyamide fiber is preferably 350 ° C. or less. Since a flexible alicyclic polyamide fiber is stably obtained by melt spinning, the melting temperature of the fiber reflecting the melting point of the polymer is also low.

Furthermore, when the alicyclic polyamide is made into a fiber, it is preferable to increase the loss tangent tan δ peak at a high temperature by sufficient thermal stretching orientation.
The birefringence (Δn) of the alicyclic polyamide fiber of the present embodiment is preferably 0.030 to 0.070. High orientation of the birefringence index of 0.030 or higher contributes to increasing the loss tangent tan δ peak and lowering MAX tan δ (0/140). On the other hand, the alicyclic polyamide fiber is obtained with a birefringence of 0.070 or less from the unit structure of the polymer.

Hereinafter, fiberization of the alicyclic polyamide of this embodiment will be described.
[Alicyclic polyamide fiber]
Various methods can be used as a method for producing the alicyclic polyamide filament fiber. Usually, melt spinning is used, and it is preferable to use a screw-type melt extruder. The spinning temperature (melting temperature) of the polyamide is preferably 300 ° C. or higher and 360 ° C. or lower. If it is 300 degreeC or more, mixing of the undissolved substance by heat shortage can be suppressed. When it is 360 ° C. or lower, the thermal decomposition of the polymer and the generation of decomposition gas are greatly reduced, and the spinnability is improved.

After the heat melting, it is passed through a spinning pack incorporating a metal nonwoven fabric filter and discharged through a nozzle hole nozzle called a spinning nozzle. The number of filaments of the multifilament fiber is determined by the number of holes in the nozzle at this time.
The discharged yarn is rapidly cooled and solidified by applying cold air. A finish is then applied. As the finishing agent, a non-aqueous finishing agent diluted with mineral oil or an aqueous dispersion emulsion having a finishing agent concentration of 15 to 35% by weight is applied. The amount of the finishing agent attached to the fiber is 0.5 to 2.5% by weight, preferably 0.7 to 2.0% by weight, based on the wound fiber.

In the stretching step, a heating bath, heated steam spraying, a roller heater, a contact type plate heater, a non-contact type plate heater, or the like can be used, but a roller heater is preferable from the viewpoint of productivity. Further, in the stretching of this embodiment, it is preferable to perform two or more stages of multi-stage hot stretching including the steps of cold stretching and hot stretching. In particular, in order to develop fiber strength, the cold drawing temperature, the hot drawing temperature, the ratio of the cold drawing ratio and the hot drawing ratio are important.
Cold drawing plays the role of pre-drawing to properly align the fiber orientation before hot drawing. Since the polyamide resin of this embodiment has a high Tg, the cold stretching temperature also requires a high temperature of (Tg-30 ° C.) or higher and Tg or lower. By being (Tg-30 ° C.) or more, the film is uniformly oriented without stretching spots and good strength can be obtained. It can suppress that crystallization advances excessively because it is below Tg. In addition, in uniaxial orientation by stretching, there is a portion called a neck point where the diameter suddenly decreases and the orientation proceeds, but the neck point is stable because the cold stretching temperature is Tg or less. Uniform fibers can be obtained.

Since the polyamide resin of this embodiment has a high Tg, stretch spots and excessive thermal crystallization are likely to occur during stretching due to insufficient heat or excessive heat. Therefore, in order to perform high stretching, the distribution of the cold stretching ratio and the hot stretching ratio is very important. The distribution of the cold draw ratio is preferably 50% or more and 80% or less of the overall draw ratio. When the distribution of the cold draw ratio is 50% or more of the total draw ratio, the necessary pre-drawing is given to the fiber, and a uniform fiber without drawing unevenness can be obtained. Moreover, excessive crystallization by hot stretching can be suppressed. On the other hand, if the distribution of the cold draw ratio is 80% or less of the total draw ratio, the heat necessary for crystallization is given by hot drawing, and excellent strength can be obtained.
The heat stretching temperature is preferably 200 ° C. or higher and 250 ° C. or lower. When it is 200 ° C. or higher, the amount of heat necessary for crystallization can be provided, and when it is lower than 250 ° C., thermal degradation of the fiber can be suppressed. The overall draw ratio is 2.0 to 7.0 times, preferably 3.0 to 6.0 times. If sufficient stretching is performed, it contributes to increasing the loss tangent tan δ peak due to crystal orientation and molecular chain orientation.

[Short fiber]
The alicyclic polyamide fiber of this embodiment is preferably obtained by cutting a long fiber made of a bundle of single yarns (filaments) produced in a continuous spinning process at a constant length. Since the fiber length of the short fiber is constant and the fiber length and fiber diameter of the short fiber are constant, the fiber is well utilized for forming anisotropy of rubber characteristics when oriented and blended with rubber.
The cross ratio (maximum diameter / minimum diameter) of the filaments in the alicyclic polyamide fiber of the present embodiment is preferably 1.7 or less, more preferably 1.5 or less. A constant fiber diameter of the short fibers enhances the effect of rubber orientation blending.
The total fineness of the alicyclic polyamide fiber of this embodiment is preferably 100 dtex or more. The simultaneous cutting with a fineness as thick as possible contributes to the constant fiber length and fiber diameter of the short fibers.
The single yarn fineness of the short fiber of this embodiment is preferably 0.5 to 10 dtex, more preferably 1 to 6.5 dtex. If the single yarn fineness is 1 dtex or more, the elasticity of the short fibers contributes to good dispersion in the rubber, and if the single yarn fineness is 10 dtex or less, the flexibility of the rubber is difficult to be inhibited.

The cross-sectional shape of the short fiber single yarn is preferably a round cross-section. If the cross-sectional shape of the single yarn is a round cross-section, the single yarn oriented perpendicular to the sliding surface of the belt can be prevented from changing the friction coefficient due to its own deformation in the cross-section. The cross-sectional shape of the single yarn is preferably from 1.00 to 1.05 in terms of flatness comprising the ratio of the major axis (longest interval) to the minor axis (shortest interval) of the circumscribed rectangle of the outer shape.
It is preferable that the fiber length of the short fiber of this embodiment is 0.5-10 mm, More preferably, it is 0.5-5 mm, More preferably, it is 1-5 mm, More preferably, it is 1-4 mm. If the cut length of the short fiber is 10 mm or less, the fibers are unlikely to be entangled with each other, the orientation in the rubber is good, and the flexibility of the power transmission belt is not impaired. On the other hand, if it is 0.5 mm or more, the reinforcing effect of the rubber frictional transmission portion of the power transmission belt is effective, and belt running troubles are eliminated.

The adhesive treatment of this embodiment is a treatment for impregnating a resin for adhering the synthetic fiber and rubber, and examples thereof include RFL (resorcin-formalin-latex) treatment. In the adhesive treatment process, heat is applied to develop an adhesive force between the fiber and the adhesive, and the fiber itself is thermally stabilized.
The RFL liquid is a treatment liquid in which a resorcin / formaldehyde initial condensate and a rubber latex are mixed. In this case, the molar ratio of resorcin to formaldehyde is preferably 3/1 to 1/3 in order to increase the adhesive force. Moreover, it is preferable when the solid content adhesion amount of RFL liquid is 1-10 weight%, when raising the effect of the adhesive force by RFL liquid. If it exceeds 1/1, the cohesive force of the short fibers becomes large and the dispersibility becomes worse. Conversely, if it becomes less than 1/5, the adhesive strength between the rubber and the short fibers may decrease, and the tensile strength may also decrease. is there. Further, when the solid content adhesion amount of the RFL liquid is 15 weights or less, it is avoided that the filaments of the short fibers are difficult to be separated due to the lump of the treatment liquid. More preferably, it is 10% by weight or less. On the other hand, if it is 1 weight or more, the effect of improving dispersibility and adhesion by the RFL solution can be expected. The solid content adhesion amount of the RFL liquid is more preferably 3% by weight or more.

Examples of rubber latex include styrene / butadiene / vinylpyridine terpolymer, chlorosulfonated polyethylene, hydrogenated nitrile rubber, epichlorohydrin, natural rubber, SBR, chloroprene rubber, olefin-vinyl ester copolymer, and EPDM latex. Can be mentioned.
In addition, the temperature of the process liquid at the time of performing an adhesion | attachment process is adjusted to 5-40 degreeC, Moreover, the immersion time is 0.5-30 seconds, It is 1-3 minutes in the oven adjusted to 200-250 degreeC. It is desirable to be heat treated through. In addition, a pre-dip process can be performed before the RFL process, or an overcoat process can be performed after the RFL process.

  The short fiber for reinforcing rubber of the present embodiment is preferably a short fiber obtained by cutting the multifilament fiber after the adhesive treatment.

It is preferable that the adhesive adhesion amount to the short fiber of this embodiment is 1-15 mass%, More preferably, it is 1.5-10 mass%, More preferably, it is 2-5 mass%. If the adhesion amount of the adhesive is 1% by mass or more, it contributes to the uniform and good adhesion of the short fiber to the rubber. If the adhesion amount of the adhesive is 10% by mass or less, the short fiber is an adhesive. It does not become a hard lump but contributes to the dispersion of single yarn in rubber.
When applying the adhesive in two or more stages, it is necessary to pay attention to the fact that the first stage adhesive hinders the penetration of the adhesive in the subsequent stage. In order to compensate for this, it is better to avoid excessive adhesion of the adhesive through the former stage or the latter stage.

[Short fiber reinforced rubber]
The short fiber reinforced rubber of the present embodiment is obtained by blending 5 to 80 parts by mass of the rubber reinforcing short fibers with respect to 100 parts by mass of the rubber component. More preferably, it is 10-40 mass parts, More preferably, it is 20-30 mass parts. Other short fibers other than the present embodiment may be mixed.
As shown in FIG. 1, short fiber reinforced rubber is preferably used for the compressed rubber layer 11. The short fibers 16 are preferably arranged so as to be oriented in the belt width direction. For example, the short fibers 16 may be subjected to an adhesive treatment of heating after being immersed in an aqueous solution of resorcin / formalin / latex (hereinafter referred to as “RFL aqueous solution”), or the adhesive treatment may not be performed. Also good.

  Examples of the rubber component of the rubber composition forming the compressed rubber layer 11 include ethylene-α-olefin elastomer (EPDM, EPR, etc.), chloroprene rubber (CR), chlorosulfonated polyethylene rubber (CSM), hydrogenated acrylonitrile rubber. (H-NBR) and the like. Of these, ethylene-α-olefin elastomers are preferable, and EPDM is particularly preferable. The rubber component may be composed of a single species or a blend of a plurality of species.

[Combination agent]
Examples of the compounding agent include a reinforcing agent, a filler, an anti-aging agent, a softening agent, a crosslinking agent, a vulcanization accelerator, and a vulcanization acceleration aid.
Examples of the reinforcing agent include carbon black and silica. Examples of carbon black include channel black; furnace black such as SAF, ISAF, N-339, HAF, N-351, MAF, FEF, SRF, GPF, ECF, and N-234; thermal black such as FT and MT; Examples include acetylene black. The reinforcing agent may be composed of a single species or a plurality of species. The blending amount of the reinforcing agent is preferably 30 to 80 parts by mass, more preferably 40 to 70 parts by mass with respect to 100 parts by mass of the rubber component, from the viewpoint that the balance between wear resistance and flex resistance becomes good. More preferably, it is 50-70 mass parts.

  Examples of the filler include inorganic fillers such as layered silicate containing calcium carbonate and bentonite. Examples of the layered silicate include smectite group, vermulite group and kaolin group. Examples of the smectite group include montmorillonite, beidellite, saponite, and hectorite. Examples of the vermulite family include 3 octahedral vermulites, 2 octahedral vermulites, and the like. Examples of the kaolin family include kaolinite, dickite, halloysite, lizardite, amesite, and chrysotile. Of these, smectite montmorillonite is preferred. The filler may be composed of a single species or a plurality of species. The blending amount of the filler is preferably 10 to 70 parts by mass, more preferably 20 to 60 parts by mass, and further preferably 25 to 35 parts by mass with respect to 100 parts by mass of the rubber component. The blending amount of the reinforcing agent and the filler is preferably 40 to 150 parts by mass, more preferably 55 to 115 parts by mass, and further preferably 70 to 80 parts by mass with respect to 100 parts by mass of the rubber component. is there.

Antiaging agents include amine-based, quinoline-based, hydroquinone derivatives, phenol-based, and phosphite-based agents. The anti-aging agent may be composed of a single species or a plurality of species. The amount of the anti-aging agent is, for example, 0 to 8 parts by mass with respect to 100 parts by mass of the rubber component.
Examples of softeners include mineral oil softeners such as paraffinic oil, castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, palm oil, raw fallen oil, wax, rosin, pine oil, etc. And vegetable oil-based softeners and petroleum-based softeners. The softener may be composed of a single species or a plurality of species. The compounding quantity of a softening agent is 2-30 mass parts with respect to 100 mass parts of rubber components, for example.

Examples of the crosslinking agent include sulfur and organic peroxides. As the crosslinking agent, sulfur may be used, organic peroxide may be used, or both of them may be used in combination. In the case of sulfur, the compounding amount of the crosslinking agent is, for example, 0.5 to 4.0 parts by mass with respect to 100 parts by mass of the rubber component. For example, 0.5 to 8 parts by mass.
Examples of the vulcanization accelerator include thiuram (for example, TET), dithiocarbamate (for example, EZ), and sulfenamide (for example, MSA). The vulcanization accelerator may be composed of a single species or a plurality of species. The compounding quantity of a vulcanization accelerator is 2-10 mass parts with respect to 100 mass parts of rubber components, for example.
Examples of the vulcanization acceleration aid include metal oxides such as magnesium oxide and zinc oxide (zinc white), fatty acids such as metal carbonates and stearic acid, and derivatives thereof. The vulcanization acceleration aid may be composed of a single species or a plurality of species. The compounding quantity of a vulcanization | cure acceleration | stimulation adjuvant is 0.5-8 mass parts with respect to 100 mass parts of rubber components, for example.

As shown in FIG. 1, the short fibers 16 are arranged so as to protrude from the surface of the V rib 15 of the compressed rubber layer 11 constituting the pulley contact portion. The protruding length of the short fibers 16 is preferably 0.01 to 5 mm, more preferably 0.05 to 2 mm. If the rubber composition containing the short fibers is ground, a form in which the short fibers 16 protrude from the surface can be obtained.
In addition to the rubber composition forming the compressed rubber layer 11, a surfactant or the like may be blended.

[Belt configuration]
As shown in FIG. 1, the adhesive rubber layer 12 is formed in a band shape having a horizontally long cross section, and has a thickness of, for example, 1.0 to 2.5 mm. The back rubber layer 13 is also configured in a band shape having a horizontally long cross section, and has a thickness of, for example, 0.4 to 0.8 mm. The surface of the back rubber layer 13 is preferably formed in a form in which the texture of the woven fabric is transferred from the viewpoint of suppressing the sound generated between the flat rubber and the flat pulley with which the belt back contacts. The adhesive rubber layer 12 and the back rubber layer 13 are formed of a rubber composition obtained by heating and pressurizing an uncrosslinked rubber composition in which various compounding agents are blended into a rubber component and then kneading and crosslinking with a crosslinking agent. . The back rubber layer 13 is preferably formed of a rubber composition that is harder than the adhesive rubber layer 12 from the viewpoint of suppressing sticking from being caused by contact with a flat pulley that contacts the back of the belt. The compressed rubber layer 11 and the adhesive rubber layer 12 constitute a V-ribbed belt main body B. Instead of the back rubber layer 13, for example, a woven fabric formed of yarns such as cotton, polyamide fiber, polyester fiber, and aramid fiber Further, a configuration in which a reinforcing fabric composed of a knitted fabric, a nonwoven fabric or the like is provided may be used.

Examples of the rubber component of the rubber composition forming the adhesive rubber layer 12 and the back rubber layer 13 include ethylene-α-olefin elastomer (EPDM, EPR, etc.), chloroprene rubber (CR), chlorosulfonated polyethylene rubber (CSM). And hydrogenated acrylonitrile rubber (H-NBR). The rubber component of the adhesive rubber layer 12 and the back rubber layer 13 is preferably the same as the rubber component of the compressed rubber layer 11. Examples of the compounding agent include a reinforcing agent, a filler, an anti-aging agent, a softening agent, a crosslinking agent, a vulcanization accelerator, and a vulcanization acceleration aid, as in the case of the compressed rubber layer 11. The rubber composition forming the adhesive rubber layer 12 and the back rubber layer 13 may contain short fibers or may not contain short fibers.
The compressed rubber layer 11, the adhesive rubber layer 12, and the back rubber layer 13 may be formed of a rubber composition having a different composition, or may be formed of a rubber composition having the same composition.

  The core wire 14 is composed of twisted yarns such as polyester fiber (PET), polyethylene naphthalate fiber (PEN), aramid fiber, and vinylon fiber. In order to give adhesion to the V-ribbed belt main body B, the core wire 14 is subjected to an adhesive treatment to be heated after being immersed in an RFL aqueous solution before molding and / or an adhesive treatment to be dried after being immersed in rubber paste. .

[Belt configuration]
It is preferable that a short fiber made of alicyclic polyamide fiber is blended with rubber, and the short fiber reinforced rubber is used for the compression rubber layer of the transmission belt.
Hereinafter, an example of a V-ribbed belt will be described as an example of a transmission belt.
FIG. 1 shows a V-ribbed belt B (friction transmission belt). Such a V-ribbed belt B is used, for example, in an auxiliary machine drive belt transmission provided in an engine room of an automobile. For example, the V-ribbed belt B may have a belt circumferential length of 700 to 3000 mm, a belt width of 10 to 36 mm, and a belt thickness of 4.0 to 5.0 mm.
The V-ribbed belt B includes a V-ribbed belt main body B configured as a triple layer of a compression rubber layer 11 that constitutes a pulley contact portion on the inner circumference side of the belt, an intermediate adhesive rubber layer 12 and a back rubber layer 13 on the outer circumference side of the belt. A core wire 14 is embedded in the adhesive rubber layer 12 so as to form a spiral having a pitch in the belt width direction.
The compressed rubber layer 11 constitutes a pulley contact portion, and is provided so that a plurality of V ribs 15 hang down to the belt inner peripheral side. The plurality of V ribs 15 are each formed in a ridge having a substantially inverted triangular cross section extending in the belt length direction and arranged in parallel in the belt width direction. Each V rib 15 may have a rib height of 2.0 to 3.0 mm and a width between base ends of 1.0 to 3.6 mm, for example. The number of ribs can be, for example, 3-6 (three in FIG. 1). The compressed rubber layer 11 is formed of a rubber composition obtained by heating and pressurizing an uncrosslinked rubber composition in which various compounding agents are blended and kneaded with a rubber component and then crosslinking with a crosslinking agent.

[Manufacture of V-rib belt]
Next, an example of a method for manufacturing the V-ribbed belt B will be described.
In the manufacture of the V-ribbed belt B, first, each compound containing the short fiber 16 is blended in the rubber component, kneaded by a kneader such as a kneader or a Banbury mixer, and the obtained uncrosslinked rubber composition is formed into a sheet by calendar molding or the like. An uncrosslinked rubber sheet for the compressed rubber layer 11 (an uncrosslinked rubber composition for forming a belt) is produced. The uncrosslinked rubber sheet for the compressed rubber layer 11 has short fibers 16 oriented in the length direction. Similarly, uncrosslinked rubber sheets for the adhesive rubber layer 12 and the back rubber layer 13 are also produced. Moreover, the adhesion process which immerses and heats the twisted yarn used as the core wire 14 in RFL aqueous solution is performed, and the adhesion process which immerses a twisted yarn in rubber paste and heat-drys as needed is performed.

  Next, an uncrosslinked rubber sheet for the back rubber layer 13 and an uncrosslinked rubber sheet for the adhesive rubber layer 12 are sequentially wound around the outer peripheral surface of the cylindrical shape and laminated, and a twisted yarn for the core wire 14 is formed on the cylindrical shape. Then, a belt-formed molded body is formed by winding the material in a spiral shape and winding and laminating an uncrosslinked rubber sheet for the adhesive rubber layer 12 and an uncrosslinked rubber sheet for the compression rubber layer 11 in this order. In addition, when it is set as the structure which the short fiber 16 of the compression rubber layer 11 orientated in the belt width direction, the orientation direction of the short fiber 16 is made to correspond with the axial direction of a cylindrical type in the uncrosslinked rubber sheet for compression rubber layers 11. Should be arranged.

Next, a rubber sleeve is placed on the belt-forming molded body, and the rubber sleeve is placed and sealed in the vulcanizing can, and the vulcanizing can is filled with high-temperature and high-pressure steam, and the state is maintained for a predetermined time. At this time, the cross-linking of the uncrosslinked rubber sheet proceeds and integrates and is combined with the twisted yarn, and finally, the cylindrical belt slab S is formed. The molding temperature of the belt slab S is, for example, 100 to 180 ° C., the molding pressure is, for example, 0.5 to 2.0 MPa, and the molding time is, for example, 10 to 60 minutes.
Next, steam is discharged from the vulcanizing can to release the seal, and the belt slab S molded on the cylindrical shape is taken out.

Next, the belt slab S is spanned between a pair of slab suspension shafts, and a grinding wheel in which V-rib-shaped grooves extending in the circumferential direction are connected to the outer circumferential surface of the belt slab S in the axial direction of the outer circumferential surface is rotated. The belt slab S is also rotated between the pair of slab suspension shafts, and the outer peripheral surface thereof is ground over the entire circumference. At this time, the V rib 15 is formed on the outer peripheral surface of the belt slab S, and a form in which the short fibers 16 protrude from the surface of the V rib 15 is obtained. The belt slab S may be divided by grinding in the length direction as necessary.
Then, the belt slab S on which the V ribs 15 are formed by grinding is cut into a predetermined width and turned upside down to obtain the V ribbed belt B.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.
[Production of polyamide multifilament]
<Production Example 1>
The weight of the raw material monomer is 1500 g and 1,4-cyclohexanedicarboxylic acid 831 g (4.83 mol), 1,10-decamethylenediamine 416 g (2.41 mol), so as to have the composition ratio shown in Table 1 below, Then, 280 g (2.41 mol) of 2-methylpentamethylenediamine was dissolved in 1500 g of distilled water to prepare an equimolar 50 mass% homogeneous aqueous solution of the raw material monomer. In this homogeneous aqueous solution, 17.0 g of 1,10-decamethylenediamine (0.10 mol, 2.1% with respect to the total diamine) so that the amount of diamine added is 2.1% with respect to the equimolar amount. Further, potassium iodide and copper iodide were added so that the copper concentration was 170 ppm and the iodine concentration was 0.68% based on the polymer weight after polymerization to obtain an aqueous solution.
The obtained aqueous solution was charged into an autoclave (made by Nitto Koatsu Co., Ltd.) having an internal volume of 5.4 L, kept warm until the liquid temperature (internal temperature) reached 50 ° C., and the inside of the autoclave was replaced with nitrogen. The liquid temperature was continuously heated from about 50 ° C. until the pressure in the autoclave tank reached about 2.5 kg / cm ² as gauge pressure (hereinafter, all pressure in the tank was expressed as gauge pressure). (The liquid temperature in this system was about 145 ° C.).

In order to keep the pressure in the tank at about 2.5 kg / cm ² , heating was continued while removing water out of the system, and the solution was concentrated until the concentration of the aqueous solution reached about 75% by mass (the liquid temperature in this system was It was about 160 ° C.). The removal of water was stopped, and heating was continued until the pressure in the tank reached about 30 kg / cm ² (the liquid temperature in this system was about 245 ° C.). Heating was continued until the final temperature was −30 ° C. while removing water out of the system in order to keep the pressure in the tank at about 30 kg / cm ² . After the liquid temperature rose to a final temperature of −30 ° C. (here, 290 ° C.), the pressure was reduced while heating was continued while taking 60 minutes until the pressure in the tank reached atmospheric pressure (gauge pressure was 0 kg / cm ² ). Thereafter, the heater temperature was adjusted so that the final temperature of the resin temperature (liquid temperature) was about 320 ° C. With the resin temperature kept in this state, the inside of the tank was maintained for 10 minutes under a reduced pressure of 100 torr with a vacuum apparatus. Thereafter, it was pressurized with nitrogen to form a strand from the lower nozzle (nozzle), water-cooled and cut, and discharged in a pellet form to obtain a polyamide. The obtained polyamide was dried with a vacuum dryer, and the moisture content was adjusted to 500 ppm.

The polyamide in the dried state is melt-spun using a melt spinning device (cap nozzle fine nozzle: number of holes 72, hole diameter 0.23 mm, outer diameter 130 mm), spinning temperature 320 ° C., spinning heater temperature 320 ° C., heating cylinder temperature 120 ° C. Spinning was carried out under the conditions (heating tube length 150 mm, inner diameter 170 mm). Then, after cooling at a cold air speed of 0.9 m / s, a finish was attached at 1.0% by weight with respect to the wound fiber. Next, 65% of the total draw ratio was drawn at a cold drawing temperature of 138 ° C., and further drawn at a hot drawing temperature of 220 ° C. After stretching, entanglement was imparted 8 times / m by an entanglement imparting device, and wound with a winder to obtain polyamide multifilament fiber A. The melting point of the fiber was 280 ° C., the fineness was 238 dtex, the number of filaments was 72, and the tensile strength was 8.6 cN / dtex.
This fiber had a low MAX tan δ (0/140).
The evaluation results of the obtained fiber are shown in Table 2 below.

<Production Example 2>
The weight of the raw material monomer is 1500 g, and the composition ratio in Table 1 below is set to 816 g (4.74 mol) of 1,4-cyclohexanedicarboxylic acid, 490 g (2.84 mol) of 1,10-decamethylenediamine, Then, 194 g (1.90 mol) of 1,5-pentamethylenediamine was dissolved in 1500 g of distilled water to prepare an equimolar 50 mass% homogeneous aqueous solution of the raw material monomer. In this homogeneous aqueous solution, 17.0 g of 1,10-decamethylenediamine (0.10 mol, 2.1% with respect to the total diamine) so that the amount of diamine added is 2.1% with respect to the equimolar amount. Further, potassium iodide and copper iodide were added so that the copper concentration was 170 ppm and the iodine concentration was 0.68% based on the polymer weight after polymerization to obtain an aqueous solution. Next, polyamide was synthesized and dried in the same manner as in Production Example 1. The obtained polyamide was subjected to spinning, finishing agent adhesion, stretching, and confounding in the same manner as in Production Example 1 except that the spinning temperature was 330 ° C, the spout heater temperature was 330 ° C, and the cold drawing temperature was 134 ° C. Multifilament fiber B was obtained. The melting point of the polyamide multifilament fiber B was 292 ° C., the fineness was 238 dtex, the number of filaments was 72, and the tensile strength was 8.6 cN / dtex.
This fiber had a low MAX tan δ (0/140).

(Preparation of short fibers used in Examples and Comparative Examples)
Each fiber obtained in Preparation Examples 1 and 2 was immersed in an RFL solution, heated at 220 ° C. for 1 minute, and DIP-treated. This was cut to obtain short fibers, which were used in Examples 1 and 2 below, respectively. The RFL composition was obtained by aging resorcin / formalin / vinylpyridine latex with sodium hydroxide to obtain a composition liquid having a solid weight ratio of RF / L = 1/2. In Example 3 below, the short fibers used in Example 2 with different cutting lengths were used.
In Comparative Example 1 below, short fibers obtained in the same manner as in Example 1 were used from polyamide 66 235 dtex / 72 filaments having a tensile strength of 8.5 cN / dtex. Further, in Comparative Example 2 below, short fibers obtained in the same manner as in Example 1 were used, using aramid fibers with a fineness of 220 dtex, a filament count of 134, and a tensile strength of 20.3 cN / dtex.

(V-ribbed belt)
V-ribbed belts of Examples 1 to 3 and Comparative Examples 1 and 2 below were produced.
(Compressed rubber layer)
Uncrosslinked rubber sheet for compressed rubber layer,
EPDM (trade name: EPT3045 manufactured by Mitsui Chemicals); 100 parts by mass of a rubber component,
60 parts by mass of HAF carbon black (trade name: Seast SO manufactured by Tokai Carbon Co., Ltd.)
2 parts by mass of a benzimidazole anti-aging agent (trade name: NOCRACK MB, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
10 parts by mass of a paraffinic oil (trade name: Diana Process Oil PW-90 manufactured by Idemitsu Kosan Co., Ltd.) as a softener
2.3 parts by mass of sulfur,
Vulcanization accelerator-mixed system (thiuram system / dithiocarbamate system / thiazole system); (trade name: Sunseller EM-2, manufactured by Sanshin Chemical Co., Ltd.) 1.4 parts by mass,
Zinc oxide as a vulcanization acceleration aid, and 25 parts by mass of alicyclic polyamide short fibers,
After kneading with a Banbury mixer, it was rolled with a calender roll.
Similarly, an uncrosslinked rubber sheet of an EPDM rubber composition for an adhesive rubber layer and a back rubber layer was prepared. Moreover, the twisted yarn of the polyester fiber for cords which performed the adhesion process by RFL aqueous solution was prepared.
And the V ribbed belt by which the compression rubber layer was formed with the EPDM rubber composition which mix | blended the short fiber with the above-mentioned method was produced.
This V-ribbed belt had a belt circumferential length of 1200 mm, a belt thickness of 4.3 mm, a number of ribs of 3 and a belt width of 10.68 mm.

(Heat resistance durability test)
FIG. 2 shows a pulley layout of a belt running test machine 70 for a heat durability test.
This heat resistance durability evaluation belt running test machine 70 includes a driving pulley 71 that is a rib pulley having a pulley diameter of 120 mm, and a first driven pulley that is a rib pulley having a pulley diameter of 120 mm provided above the driving pulley 71. 72, an idler pulley 73, which is a flat pulley having a diameter of 45 mm, provided in the middle in the vertical direction of the drive pulley 71 and the first driven pulley 72, and a pulley diameter provided to the right of the idler pulley 73. And a second driven pulley 74 which is a 45 mm rib pulley. In the belt running test machine 70 for heat and durability test, the V rib side of the V-ribbed belt B is in contact with the drive pulley 71, which is a rib pulley, the first and second driven pulleys 72 and 74, and the back side is a flat pulley. It is configured to be wound around the idler pulley 73. Each of the idler pulley 73 and the second driven pulley 74 is positioned so that the winding angle of the V-ribbed belt B is 80 °.

The three ribs of each of Examples 1 to 3 and Comparative Examples 1 and 2 were set in the belt running test machine 70 for heat and durability test, and the second driven pulley 74 was loaded with belt tension. The first driven pulley 72 is loaded with a rotational load of 11.8 kW, and the drive pulley 71 is rotated at a rotational speed of 4900 rpm under an ambient temperature of 130 ° C. to drive the belt. It was. After 20 hours, the temperature of the compressed rubber layer (surface temperature) was measured with a non-contact thermometer.
In addition, the atmospheric temperature was set to 30 ° C. and 130 ° C. under the same conditions, and cracks were generated in the compressed rubber layer of the V-ribbed belt B, and the running time until it reached the core was measured and compared. The percentage of the running life at an ambient temperature of 130 ° C. with respect to the running life at an ambient temperature of 30 ° C. was obtained as a high temperature change rate (%).
Furthermore, the V-ribbed belt was exposed to an atmosphere of 150 ° C. for 5 hours, and then the running life at an ambient temperature of 130 ° C. was measured. The percentage of the running life at an ambient temperature of 130 ° C. after the high temperature exposure to the running life at the ambient temperature of 130 ° C. before the high temperature exposure (described above) was obtained as a post-heat retention rate (%).
Table 2 below shows the characteristics of the short fibers used and the like, as well as the surface temperature, rate of change at high temperature, and retention after heat.

As can be seen from Table 2, in Examples 1 to 3, the belt surface temperature increase was small and the energy loss was small. Further, the high temperature change rate hardly decreased from 100%, and the running life at high temperature was good. The running life after heat exposure was also maintained and good.
On the other hand, in Comparative Example 1, the belt surface temperature rise was large, energy loss was large, and fatigue was also affected. Moreover, the high temperature change rate was bad, fatigue was advanced, and durability was greatly reduced. However, the high-temperature running life after exposure to heat did not change much.
In Comparative Example 2, the belt surface temperature increase was small and the energy loss was small. Moreover, the running life at high temperature was good. However, the high temperature running life after exposure to heat was significantly reduced. It is presumed that the poor adhesion between the aramid fiber and the rubber has become apparent.

  The short fiber according to the present invention is excellent in rubber adhesion and has a characteristic that bending energy loss is small from room temperature to high temperature. Therefore, if this short fiber is blended with rubber, it becomes a rubber that does not lose its durability with little bending heat generation, and if it is used for the compression layer of a transmission belt, it is durable under high load, high bending, and high temperature environments. It is possible to provide a power transmission belt with improved performance.

11: Compression rubber layer 12: Adhesive rubber layer 13: Back rubber layer 14: Core wire 15: V rib 16: Short fiber 70: Belt running test machine 71 for heat and durability test 71: Drive pulley 72: First driven pulley (rib pulley)
73: idler pulley (flat pulley)
74: Second driven pulley (rib pulley)
B: V rib belt

Claims (15)

  Short fiber for rubber reinforcement made by cutting alicyclic polyamide fiber.   The short fiber for rubber reinforcement according to claim 1, wherein the melting point of the alicyclic polyamide fiber is 270 ° C or higher.   The short fiber for rubber reinforcement according to claim 1 or 2, wherein a birefringence of the alicyclic polyamide fiber is 0.030 to 0.070.   The short fiber for rubber reinforcement according to any one of claims 1 to 3, wherein a cut length of the short fiber for rubber reinforcement is 0.5 mm to 10 mm.   The short fiber for rubber reinforcement according to any one of claims 1 to 4, wherein the single yarn fineness of the short fiber for rubber reinforcement is 0.5 dtex to 10 dtex.   The short fiber for rubber reinforcement according to any one of claims 1 to 5, wherein 1 to 15 parts by weight of resorcin-formalin-latex (RFL) is attached.   The rubber reinforcement according to any one of claims 1 to 6, wherein a maximum value of a loss tangent tan δ between 0 ° C and 140 ° C is 0.100 or less in dynamic viscoelasticity measurement of the alicyclic polyamide fiber. For short fiber. The alicyclic polyamide fiber is a polyamide multifilament fiber comprising a polycondensate of a dicarboxylic acid containing an alicyclic dicarboxylic acid and a diamine, and the following requirements:
(A) The ratio of the alicyclic dicarboxylic acid to the dicarboxylic acid is 50 mol% or more;
(B) the total fineness of the polyamide multifilament fiber is 100 dtex or more; and (c) the cross ratio (maximum diameter / minimum diameter) of the polyamide multifilament fiber is 1.7 or less;
The short fiber for rubber reinforcement according to any one of claims 1 to 7, which satisfies:   The short fiber for rubber reinforcement according to claim 8, wherein the polyamide multifilament fiber has a sulfuric acid relative viscosity of 1.5 or more and 4.0 or less.   The polyamide multifilament fiber contains 1,10-decanediamine as a diamine component, and the ratio of the 1,10-decanediamine to the whole diamine component is 20 mol% or more. Short fiber for rubber reinforcement.   The polyamide multifilament fiber contains a diamine having 5 or 6 carbon atoms as a diamine component, and the ratio of the diamine having 5 or 6 carbon atoms to the entire diamine component is 20 mol% or more. 11. The short fiber for reinforcing rubber according to any one of 10 above.   The short fiber for rubber reinforcement according to claim 11, wherein the diamine having 5 or 6 carbon atoms is 2-methylpentamethylenediamine.   The short fiber for rubber reinforcement according to claim 11, wherein the diamine having 5 or 6 carbon atoms is hexamethylenediamine.   A short fiber reinforced rubber comprising 5 to 80 parts by weight of the short fiber for reinforcing rubber according to any one of claims 1 to 13.   A power transmission belt using the short fiber reinforced rubber according to claim 14 as a compression layer.

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