WO2023286738A1

WO2023286738A1 - Polyamide fibers for tire cord and method for producing same

Info

Publication number: WO2023286738A1
Application number: PCT/JP2022/027269
Authority: WO
Inventors: 浩介井田
Original assignee: 旭化成株式会社
Priority date: 2021-07-16
Filing date: 2022-07-11
Publication date: 2023-01-19
Also published as: JPWO2023286738A1; CN117642531A

Abstract

Provided are: polyamide fibers for a tire cord, with which cutting of a cord during steps for producing a tire cord and tire cord fabric is suppressed; a method for producing same; a twisted yarn cord using the fibers; and cord fabric using the cord. The present invention relates to polyamide fibers for a tire cord and a method for producing same, wherein the air-knot strength of the polyamide fibers in an environment at a temperature of 180°C is 3.5-6.0 cN/dtex.

Description

Polyamide fiber for tire cord and its production method

The present invention relates to a polyamide fiber for tire cords, a method for producing the same, a twisted yarn cord using the fiber, and a cord fabric using the cord.

Due to its excellent toughness, adhesiveness, and fatigue resistance, polyamide fiber is widely used as a fiber for reinforcing rubber, such as tire cords for trucks, buses, construction, and aircraft.

As described in Patent Document 1 below, radial tires for aircraft are generally used under conditions of high internal pressure and high load, so there is a strong demand for load resistance and suppression of tire diameter growth. In addition, there is also a growing demand for cost reduction and weight reduction, and as a reinforcing fiber used in radial tires for aircraft, it is important to reduce the amount of fiber without impairing its function. In order to satisfy such demands, it is required to develop fibers with higher strength and higher rigidity.

As described in Patent Document 2, as a method for producing a tire reinforcing cord, a polyamide fiber is made into a twisted cord, and then treated with an adhesive (hereinafter also referred to as "dip"), and then the twisted cord is subjected to tension. A method of tension heat treatment is known. Twisted yarn cords have been subjected to tension heat treatment at higher tensions in order to obtain reinforcing cords with higher strength and higher rigidity. By doing so, the strength after the dip treatment is increased, contributing to further weight reduction of the tire and making it possible to use the tire for higher load applications.

On the other hand, when polyamide fiber is used as a fiber for reinforcing rubber, a twisted cord (hereinafter referred to as "raw However, when producing raw cords, there are cases where the length varies, and depending on the application, extremely long raw cords are required. requires the raw cords to be connected at their ends.

Conventionally, as a general method for connecting raw cords, a method of connecting by entangling fibers called the air splicing method is known. According to this connecting method, the connecting operation is easy, the workability is excellent, and the advantage of being able to reduce the swelling of the connecting portion (hereinafter also referred to as "air knot") is obtained.

However, in the case of a tire cord having air knots connected by an air splicing method or a cord fabric for a tire cord, the twisted yarn cord cannot withstand the tension during the tension heat treatment under high temperature and high tension during the dipping described above, and the cord tends to break. , has the problem of becoming a breaking point. Since the broken part of the dipped cord or dipped fabric is treated as a defective product and distinguished from a normal product, the present situation is that there is a problem of cord breakage in the manufacture of tire cords and tire cord blind fabrics.

Japanese Patent Application Publication No. 2019-508595 JP-A-1-174628

In view of the above-described problems of the prior art, the problem to be solved by the present invention is to provide a polyamide fiber for tire cords that suppresses cord breakage in the manufacturing process of tire cords and tire cord blind fabrics.

In order to solve the above problems, the present inventors conducted extensive studies and repeated experiments, and found that air knot strength is important for suppressing cord breakage under high-temperature tension in the manufacturing process of tire cords and tire cord blind fabrics. This unexpected finding led to the completion of the invention.

That is, the present invention is as follows.
[1] A polyamide fiber for tire cords having an air knot strength of 3.5 cN/dtex or more and 6.0 cN/dtex or less at a temperature of 180°C.
[2] The polyamide fiber for tire cords according to [1] above, wherein the intertrip entanglement number is 13/m or more and 30/m or less.
[3] The polyamide fiber for tire cords according to [1] or [2], which has a 25°C air knot strength of 6.4 cN/dtex or more and 9.0 cN/dtex or less.
[4] The polyamide fiber for tire cord according to any one of [1] to [3], which has a knot strength of 4.5 cN/dtex or more and 6.5 cN/dtex or less at 25°C.
[5] The polyamide fiber for tire cord according to any one of [1] to [4], which has a tensile strength of 8.7 cN/dtex or more and 11.0 cN/dtex or less.
[6] The polyamide fiber for tire cords according to any one of [1] to [5], which has a dimensional stability of 12% or more and 20% or less.
[7] The polyamide for tire cords according to any one of [1] to [6], wherein the surface is provided with an ionic surfactant of 0.01% by weight or more and 0.1% by weight or less based on the weight of the fiber. fiber.
[8] The following physical properties (1) to (5):
(1) total fineness is 900dtex or more and 2500dtex or less;
(2) elongation is 15% or more and 25% or less;
(3) Boiling water shrinkage is 4% or more and 8% or less;
(4) Finishing agent adhesion rate is 0.5% by weight or more and 1.5% by weight or less; and (5) Number of single yarns is 100 or more and 400 or less;
Polyamide fiber for tire cord according to any one of the above [1] to [7], which is a multifilament yarn having
[9] The polyamide fiber for tire cord according to any one of [1] to [8], which has an air knot portion.
[10] A twisted yarn cord using the polyamide fiber for tire cords according to [9] above.
[11] A bamboo blind fabric using the twisted cord according to [10].
[12] A method for producing polyamide fibers for tire cords, in which polyamide fibers spun by melt spinning are wound through one or more finishing agent application devices and multi-stage stretching rollers, wherein the stretching fixed temperature of the multi-stage stretching rollers is 205° C. or higher and 240° C. or lower.

The polyamide fiber for tire cords of the present invention suppresses cord breakage under high-temperature tension in the manufacturing process of tire cords and tire cord blind fabrics.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining an example of the apparatus which manufactures the polyamide fiber for tire cords of this invention.

Hereinafter, embodiments of the present invention will be described in detail.
One embodiment of the present invention is a polyamide fiber for tire cord, which has an air knot strength of 3.5 cN/dtex or more and 6.0 cN/dtex or less in an environment at a temperature of 180°C.
The air knot strength of the polyamide fiber for tire cord of the present embodiment at a temperature of 180° C. is 3.5 cN/dtex or more and 6.0 cN/dtex or less, preferably 4.0 cN/dtex or more and 5.0 cN/dtex or less, more preferably. is 4.2 cN/dtex or more and 4.5 cN/dtex or less. The air knot strength can be measured by the method described in Examples below. An air knot strength of 3.5 cN/dtex or more in an environment at a temperature of 180° C. can suppress breakage of the twisted yarn cord under tension heat treatment. On the other hand, if the air knot strength is 6.0 cN/dtex or less in an environment at a temperature of 180° C., the entanglement of the single yarns in the air knot portion is prevented from becoming too dense, and the thickness of the cord fabric is uneven due to the gauge thickness of the seam. is less likely to occur. Incidentally, the air knot strength is a characteristic of the fiber, which is obtained by subjecting the fiber to a specific air knot operation and measuring the yarn connection characteristics.

The 25° C. (normal temperature) air knot strength of the polyamide fiber for tire cord of the present embodiment is preferably 6.4 cN/dtex or more and 9.0 cN/dtex or less, more preferably 6.8 cN/dtex or more and 8.0 cN/dtex. Below, it is more preferably 7.0 cN/dtex or more and 7.5 cN/dtex or less. When the room-temperature air knot strength is 6.4 cN/dtex or more, cord breakage can be suppressed even under tension heat treatment. On the other hand, when the room-temperature air knot strength is 9.0 cN/dtex or less, the entanglement of the single yarns in the air knot portion is prevented from becoming too dense, and unevenness in the thickness of the cord fabric due to gauge thickening at the seams is less likely to occur.

The room temperature (25°C) knot strength of the polyamide fiber for tire cord of the present embodiment is preferably 4.5 cN/dtex or more and 6.5 cN/dtex or less, more preferably 5.0 cN/dtex or more and 6.0 cN/dtex or less. More preferably, it is 5.2 cN/dtex or more and 5.8 cN/dtex or less. When the 25° C. knot strength is 4.5 cN/dtex or more, it is possible to suppress breakage of the cord under tension heat treatment. On the other hand, when the knot strength at 25° C. is 6.5 cN/dtex or less, the production can be carried out without significant decrease in process stability due to increase in fluff and yarn breakage.

The tensile strength of the polyamide fiber for tire cord of the present embodiment is preferably 8.7 cN/dtex or more and 11.0 cN/dtex or less, more preferably 9.0 cN/dtex or more and 10.5 cN/dtex or less, and still more preferably 9.0 cN/dtex or more and 10.5 cN/dtex or less. It is 4 cN/dtex or more and 10.2 cN/dtex or less. When the tensile strength is 8.7 cN/dtex or more, the tensile strength is excellent and contributes to the expression of the air knot strength and the knot strength. On the other hand, when the tensile strength is 11.0 cN/dtex or less, production can be carried out without significant deterioration in process stability due to increased fluff and yarn breakage.

The dimensional stability of the polyamide fiber for tire cords of the present embodiment is preferably 12% or more and 20% or less, more preferably 15% or more and 19% or less, and still more preferably 16% or more and 18% or less. The dimensional stability can be determined from the sum of the boiling water shrinkage of the fiber and the intermediate elongation (elongation at a high load of 1/2 of the breaking strength). When the dimensional stability is 12% or more, the toughness in rubber reinforcement applications such as tire cords is improved. On the other hand, if the dimensional stability is 20% or less, it contributes to maintaining strength at high temperatures, is excellent in tensile strength at high temperatures, and contributes to the expression of air knot strength under a temperature of 180° C. and knot strength at 25° C. .

The intertrip entanglement number of the polyamide fiber for tire cord of the present embodiment is preferably 13/m or more and 30/m or less, more preferably 13/m or more and 25/m or less, and still more preferably 17/m or more. 23 pieces/m or less. The number of intertrip entanglements refers to the degree of entanglement that satisfies 60% strength with respect to the trip level in the degree of entanglement measured by an automatic entanglement tester. If the number of intertrip entanglements is 13/m or more, the entanglement of single yarns during air knot production is promoted, and a fiber having excellent air knot strength in an environment at a temperature of 180° C. can be obtained. On the other hand, when the number of intertrip entanglements is 30/m or less, single yarn loosening and resulting single yarn fluffing in the twisting process are suppressed, so that the twisting efficiency is not lowered and the quality of the fabric is not impaired.
In addition, from the viewpoint of making the shape of the air knots uniform and suppressing slack during hanging when manufacturing the cord fabric, it is also preferable that the number of inter-trip entanglements is 25/m or more and 30/m or less.

The polyamide fiber for tire cords of the present embodiment preferably has an ionic surfactant attached thereto in an amount of 0.01% by weight or more and 0.1% by weight or less, more preferably 0.012% by weight or more, based on the weight of the fiber. It is 0.08% by weight or less, more preferably 0.02% by weight or more and 0.06% by weight or less. By containing the above-mentioned amount of ionic surfactant, the effect of other finishing agent components is enhanced, the extreme pressure property of the yarn is improved, the stress applied to the air knot during tension is easily dispersed, and the knot strength is improved. The high strength of the polyamide fiber and the presence of the ionic surfactant on the surface of the fiber combine to improve the knot strength. When the content of the ionic surfactant is 0.01% by weight or more, it improves the knot strength and contributes to the improvement of the air knot strength. On the other hand, when the content of the ionic surfactant is 0.1% by weight or less, contamination on the surface of the rolls in the stretching process hardly causes an increase in the frequency of cleaning the rolls. The ionic surfactant can be applied to the polyamide fiber by finish application during the spinning process.

The polyamide fiber for tire cords of the present embodiment has the following physical properties (1) to (5):
(1) total fineness is 900dtex or more and 2500dtex or less;
(2) elongation is 15% or more and 25% or less;
(3) Boiling water shrinkage is 4% or more and 8% or less;
(4) Finishing agent adhesion rate is 0.5% by weight or more and 1.5% by weight or less; and (5) Number of single yarns is 100 or more and 400 or less;
It is preferably a multifilament yarn having Those having a total fineness of 900 dtex or more have sufficient mechanical properties when made into tire cords and tire cord cord fabrics. On the other hand, from the viewpoint of weight reduction, those having a total fineness of 2500 dtex or less are preferable.

The elongation is preferably 15-25%. If the elongation is 15% or more, sufficient toughness can be obtained in rubber reinforcing applications such as tire cords. In addition, there is a trade-off between elongation and strength, and the elongation is preferably 25% or less in order to balance with strength.

Also, the boiling water shrinkage ratio is preferably in the range of 4 to 8%. If the boiling water shrinkage ratio is 4.0% or more, the thermal shrinkage stress becomes high, so that the stretching during the dip treatment is suppressed, and a high-strength dipped cord can be obtained. On the other hand, if the boiling water shrinkage ratio is 8.0% or less, the dimensional stability is excellent and contributes to the development of air knot strength at high temperatures.

In addition, it is preferable that the finishing agent adhesion rate applied to the yarn in the spinning process is in the range of 0.5% by weight or more and 1.5% by weight or less. Polyamide fibers for rubber reinforcement applications such as tire cords are stretched in contact with stretching rolls at high tension, so they have excellent extreme pressure properties and reduced frictional resistance (smoothness) with metal surfaces, suppressing the reduction in strength of vulcanized cords, and In order to improve fatigue resistance, the finishing agent that reduces the frictional resistance between single fibers forming the fiber must be uniformly attached to the surface of the fiber. If the coating amount of the finishing agent is less than 0.5% by weight, the effect of reducing frictional resistance (smoothness) between the extreme pressure property and the metal surface is insufficient, making it difficult to stably produce high-strength polyamide fibers. On the other hand, if the coating amount of the finishing agent exceeds 1.5% by weight, the penetration of the dipping liquid into the polyamide fiber is inhibited during the dipping treatment, resulting in a large decrease in adhesion to the rubber.

Also, the number of single yarns is preferably 100 or more and 400 or less. A multifilament having a single filament count of 100 or more increases the specific surface area and can flexibly respond to external stress, thereby improving rubber adhesion and fatigue resistance. On the other hand, when the number of single yarns is 400 or less, it is possible to avoid fusion between single yarns during melt spinning.

Polyamide fibers for tire cords of the present embodiment include polyamide 6, polyamide 6.6, polyamide 11, polyamide 12, polyamide 6.10, polyamide 6.12, polyamide 4.6, copolymers thereof and mixtures thereof. At least one fiber selected from the group consisting of Among them, polyamide 6.6 fibers mainly composed of polyhexamethylene adipamide fibers are preferred. Polyhexamethylene adipamide refers to a polyamide fiber composed of 100% hexamethylene diamine and adipic acid and having a melting point of 250° C. or higher. Polyamide 6.6 fibers are composed of polyhexamethylene adipamide, polyamide 8, polyamide 6.5, and polyhexamethylene adipamide, as long as the melting point is not less than 250.degree. Fibers made of polymers obtained by copolymerizing or blending I, polyamide 10, polyamide 6·T, etc. may also be used.

Another embodiment of the present invention is a method for producing polyamide fibers for tire cords, in which polyamide fibers spun by melt spinning are wound through one or more finishing agent applicators and multistage drawing rollers, A method for producing a polyamide fiber for tire cord, wherein the stretching and fixing temperature of the stretching roller is 205°C or higher and 240°C or lower.
An example of a method for producing a polyamide fiber for tire cords according to the present invention will be described below.
FIG. 1 is an explanatory view showing an example of equipment for manufacturing polyamide fibers for tire cords according to the present embodiment. First, a polymer in a molten state is homogenized by a part of the spinning machine called a spin head 1 and spun from a spinneret 2 . The spun polymer passes through a heating tube 3 provided directly below the spinneret and is solidified by cold air from a cooling chamber 4 to form threads. The yarn collected at each end is then applied with finishing agent by the finishing agent applying device 5, and then fed from the take-up roller 6, the first roller 7, the second roller 8, the third roller 9, and the fourth roller 10. Then proceed to the stretching step by a group of rollers. That is, after the yarn is taken up by the roller 6 at a predetermined speed, it is guided to the first stage roller 7 with a slight tension, and is stretched from the first stage roller 7 by the multistage heating and stretching

rollers

8, 9, and 10. be. After that, it is supplied to the entangling device 11 and wound up by the winder 12 .

The finishing agent applicator 5 is not particularly limited, but generally a roll type or nozzle type is used. The finishing agent applied by the finishing agent applying device 5 is preferably 0.5% by weight or more and 1.5% by weight or less based on the weight of the fiber. When the finishing agent is 0.5% by weight or more, the yarn can be stably processed from twisting to dipping, and the quality is improved without single yarn breakage. Since the content of the finishing agent is 1.5% by weight or less, there is no trouble such as tension slipping at the knot portion.

An ionic surfactant can be applied to the fibers when the finish is applied to the fibers. The ionic surfactant includes at least one selected from the group consisting of anionic surfactants containing P atoms and anionic surfactants containing S atoms. The anionic surfactant containing a P atom is not particularly limited. mentioned. More specific examples include lauryl phosphate potassium salt, lauryl phosphate sodium salt, octyl phosphate potassium salt, octyl phosphate sodium salt and the like. An anionic surfactant containing an S atom is not particularly limited, but examples thereof include alkanesulfonates.

As the finishing agent component to be lubricated, in addition to the above-mentioned ionic surfactant, it is preferable to use a component having excellent smoothness and heat resistance so that the yarn can be drawn smoothly in the yarn making process. It is preferable from the viewpoint of quality and industrial material use. Ester compounds are preferred as the component as the smoothing agent. Those containing at least one ester compound selected from the group consisting of an ester compound having three or more ester bonds in the molecule and an ester compound having a sulfur element in the molecule are preferred.

Ester compounds having a sulfur element in the molecule include, for example, (1) ester compounds of divalent carboxylic acids such as dialkylthiodipropionates and monohydric alcohols, and (2) monovalent carboxylic acids such as alkylmercaptopropionates. and an ester compound with a monohydric alcohol.

Examples of ester compounds having three or more ester bonds in the molecule include (3) polyhydric alcohols such as trimethylolpropane trialkylate, glycerin trifatty acid ester, pentaerythritol tetrafatty acid ester, and trimethylolpropane fatty acid ester, and monohydric alcohols. Ester compounds with carboxylic acids, (4) Ester compounds with polyhydric carboxylic acids such as trialkyl trimellitate and triethyl citrate and monohydric alcohols, (5) Natural fats and oils such as castor oil, palm oil, and rapeseed oil etc. These components may be used individually by 1 type, and may be used in combination of 2 or more type.

A nonionic surfactant can be used as a regulator of emulsifying action and friction action. For example, (1) polyethylene glycol dialkylate, polyoxyethylene sorbitan monoalkylate, polyoxybutylene sorbitan trialkylate, polyoxypropylene castor oil, polyoxyethylene hydrogenated castor oil, polyoxyethylene propylene hydrogenated castor oil trialkylate, polyoxyethylene hydrogenated castor oil Ether esters obtained by condensing at least one compound selected from the group consisting of trialkylates, ethylene oxide (hereinafter also referred to as EO) adducts of castor oil and EO adducts of hardened castor oil with monocarboxylic acids and dicarboxylic acids polyoxyalkylene polyhydric alcohol fatty acid ester type nonionic surfactants such as compounds; More specifically, for example, polyoxyethylene fatty acid ester, polyoxyethylene fatty acid ester methyl ether, polyoxyethylene alkyl ether, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene polyoxypropylene nonylphenyl ether, polyoxyethylene Ether-type nonionic surfactants such as alkylamino ethers and polyoxyethylene fatty acid amide ethers, (3) Polyhydric alcohol partial ester-type nonionic surfactants such as sorbitan monofatty acid esters, sorbitan trifatty acid esters, and glycerin monofatty acid esters, ( 4) alkylamide type nonionic surfactants such as diethanolamine monofatty acid amides; These components may be used individually by 1 type, and may be used in combination of 2 or more type.

The application of the finishing agent is not limited to one diluted with mineral oil or the like, or a water-based emulsion, but it is preferable to apply it in the form of an emulsion when considering the compatibility with water in the post-process.

In the multi-stage heating and stretching rollers 10, the temperature is applied at 205°C or higher and 240°C or lower as the stretching fixing temperature. The stretching and fixing temperature is preferably 210° C. or higher and 230° C. or lower, more preferably 215° C. or higher and 220° C. or lower. When the temperature is 205° C. or higher, the dimensional stability at high temperatures in cord processing is excellent. On the other hand, if the draw-fixing temperature is 240° C. or higher, it is difficult to stably produce a polyamide fiber having a boiling water shrinkage of 4% or higher.

The entangling device 11 can use a known device that jets a compressed fluid to the yarn from an entangling nozzle, but the compressed fluid to the yarn should be supplied with an energy of 1.0 to 1.5 kW. is preferred. The compressed fluid supply energy (air supply energy) can be calculated by multiplying the supply pressure (MPa) and the flow rate (Nm3/hr). , can satisfy the above supply energy range. Furthermore, it is more preferable to supply energy of 1.3 kW or more and 1.5 kW or less. By satisfying the range of the supplied energy, it is possible to obtain a suitable intertrip entanglement number without impairing the process stability during the twisting process, promote the entanglement of the single yarns when making an air knot, and improve the air knot strength. Excellent fiber is obtained.

The polyamide fiber of the present embodiment can be suitably used for twisted yarn cords (tire cords) connected by air knots and cord fabrics using the same. By using the polyamide fiber of the present embodiment, it is possible to suppress cord breakage in the manufacturing process of the twisted yarn cord and the blind fabric.

EXAMPLES Next, the present invention will be specifically described with reference to examples and comparative examples. It should be noted that the present invention is not limited to this embodiment.
First, definitions of physical properties, measuring methods, etc. used in Examples and Comparative Examples will be described.

(1) Strength and strength of air knot Using Joint Air 116 type manufactured by Machinetex Co., Ltd. for the connecting yarn, selecting and attaching the chamber and chamber cover of the air splicer appropriately according to the fineness, and attaching the air splicer under the following conditions. to connect the polyamide fibers.
Supply air pressure: 0.5 MPa
Air injection time: 1 second Thread chopstick length: 20 mm
A 150 mm fiber sample (connecting yarn) having one air knot portion was subjected to tensile breakage in accordance with JIS L 1013 8.5 at test temperatures of 25 ° C. (room temperature) and 180 ° C. and a tensile speed of 300 mm / min. The strength was measured and defined as the air knot strength at each temperature. The measurement was performed twice for each level, and the average value was taken as the air knot strength.

(2) Knot Strength and Strength A 150 mm fiber sample was measured at 25° C. at a tensile speed of 300 mm/min according to JIS L 1013 8.6. The measurement was performed twice for each level, and the average value was taken as the knot strength.

(3) Intertrip entanglement number In accordance with ASTM D 4724, using RAPID 600V manufactured by LENZING INSTRUMENTS, under the conditions shown in Table 1 below, measure the 60% strength entanglement number (intertrip entanglement number) of the trip level. bottom. The measurement was performed 10 times per level, and the average value was taken as the intertrip confounding number.

(4) Fineness Measured according to JIS L 1013 8.3.1 A method, except that the rewinding speed was set to 60 times/min.

(5) Tensile Strength, Tensile Strength, Elongation, Intermediate Elongation According to JIS L 1013 8.5, a 150 mm fiber sample was measured at a tensile speed of 300 mm/min. The measurement was performed 3 times per level, and the average value was taken as the tensile strength. However, as the intermediate elongation, the elongation (%) at a heavy load of 1/2 of the breaking strength was used.

(6) Finishing agent deposition rate Measured according to JIS L 1013 8.27. Cyclohexane is used as the solvent.

(7) Boiling Water Shrinkage Measured according to JIS L 1013 8.18.

(8) Dimensional stability Obtained from the sum of the obtained boiling water shrinkage and intermediate elongation (elongation at 1/2 breaking strength under heavy load).

(9) Disturbance of Twisted Yarn Filaments Two raw yarns were twisted at a lower twist of 26.5 turns/100 mm and an upper twist of 26.5 turns/100 mm. The spliced yarn of the raw yarn package was spliced with an air knotter in the same manner as the air knot strength measurement described above, and the yarn was continuously twisted. This twisted yarn cord was used for blind weaving, and the supplied twisted yarn cord was counted with a KH-700 infrared sensor manufactured by Daiko Co., Ltd. and an SF2-A phototube sensor manufactured by Kasuga Denki Co., Ltd. to count filament turbulence that needed to be removed for weaving. Disarrayed filaments include single yarns of twisted yarn cords that are loose or fluffed, which may cause thickness unevenness when made into a blind. Twisted filament turbulence was evaluated based on the following criteria for 1,000 twisted cords and 1,000 m.
(Evaluation criteria)
◎: Filament disorder is less than 1.0;
○: 1.0 or more and less than 5.0 filament disturbances;
Δ: 5.0 or more but less than 10.0 filament disturbances;
x: 10.0 or more filament disturbances.

(10) Flatness In the blind weaving obtained in (9) above, the blind after weaving was visually inspected, and the hanging slack of the twisted yarn cord was counted. Suspension slack includes twisted yarn cords that are stretched or loosened, causing uneven alignment with other cords, and causing unevenness in the cords of the blinds. If the twisted cord is stretched, it looks shiny, and if it is loose, it looks blackish. The hanging slack was evaluated by the following evaluation criteria for 2,000 twisted yarn cords per 1,000 m.
(Evaluation criteria)
◎: Hanging looseness is less than 1.0;
○: The hanging slack is 1.0 or more, but it can be corrected by adjusting the tension of the fabric;
x: Hanging slack is 1.0 or more, requiring cord replacement.

(11) Cord breakage Using the twisted yarn cord obtained in (9) above, a 3200 m blind fabric was produced with a width of 1580 mm, a pick number of 2.0/50 mm, a warp number of 1091, and a warp density of 34.5/inch. Dip treatment was performed using an RFL solution (resorcin-formalin-latex solution) at a treatment speed of 86 m/min, a treatment temperature of 140 to 240° C., and a treatment tension of 300 to 5500 kgf. This weaving and working treatment was repeated 10 times. The process passability at this time was evaluated. Cord breakage was evaluated according to the following evaluation criteria.
(Evaluation criteria)
◯: Cord breakage occurred less than 0.1 times, and there was no problem in processability;
Δ: cord breakage occurred 0.1 times or more and less than 2 times;
x: There was a problem in process passability because cord breakage occurred twice or more.

[Examples 1 to 4, Comparative Example 1]
A polyhexamethylene adipamide polymer having a relative viscosity of 82 for formic acid was obtained by a known melt polymerization method and applying vacuum at the final stage of the melt polymerization. This polymer, in a molten state, was introduced into the melt spinning machine and drawing machine illustrated in FIG. 1 to obtain a high strength polyhexamethylene adipamide fiber of 1440 dtex/210 f. Specifically, after melting the polymer at 300° C., it was homogenized at 305° C. by the spin head 1, discharged from the spinneret 2 with 210 holes, and heated to a heating cylinder with a length of 70 mm at a set temperature of 300° C. 3, the yarn is passed through a heated atmosphere, cooled and solidified in a cold air chamber 4 to form a yarn, then a finishing agent application device 5, a take-up roller 6, a first roller 7 to a third roller 9, and a set temperature of 220 ° C. The yarn was sequentially passed through the fourth roller 10 , entangled with the entangling device 11 , and wound with the winder 12 . Between the first roller 7 and the fourth roller 10, the raw yarn was wound while changing the draw ratio so that the tensile strength of the obtained raw yarn would be the value shown in Table 2 below (8.46 cN to 9.99 cN). The wound fibers were twisted to prepare raw cords and cord fabrics, which were dipped in RFL liquid.

In the finishing agent application device 5, a finishing agent (containing 1.5% by weight of an ionic surfactant) having the following composition was applied so that the deposition rate was 1.1% by weight. Compressed air was applied to the entangling device 11 at 0.45 MPa, and the air supply energy was 1.3 kW. The obtained polyamide 66 fiber was evaluated for tensile strength (strength), air knot strength (strength), knot strength (strength), entanglement strength, dimensional stability and the like. In addition, process stability in the twisting process and the dip treatment process, twisted filament disturbance, and cord breakage were evaluated. The results are shown in Table 2 below.
(Finishing agent composition)
(a1) trimethylolpropane trilaurate: 10 parts by weight (a2) dioleyl thiodipropionate: 40 parts by weight (b) POEO stearyl polyether: 20 parts by weight (c1) hydrogenated castor oil EO25 triisostearate: 15 parts by weight Parts by weight (c2) hydrogenated castor oil EO25 maleic acid stearate: 15 parts by weight (d) ionic surfactant (d1) alkyl (C10-16) sulfate sodium salt: 0.5 parts by weight (d2) alkyl (C12) -18) Acid phosphate, alkyl (C12-14) amine salt: 1 part by weight

[Example 5]
The same procedure as in Example 1 was carried out, except that the air supply energy was changed to 1.0 kW in the entangling step. The results are shown in Table 2 below.

[Example 6]
In the stretching step, the same procedure as in Example 1 was carried out, except that the stretching and fixing temperature was 210°C. The results are shown in Table 2 below.

[Example 7]
The procedure was carried out in the same manner as in Example 1, except that a finishing agent containing 4.5% by weight of an ionic surfactant having the following composition was applied in the lubricating step. The results are shown in Table 2 below.
(ionic surfactant)
(d1) alkyl (C10-16) sulfate sodium salt: 1.5 parts by weight (d2) alkyl (C12-18) acid phosphate, alkyl (C12-14) amine salt: 3 parts by weight

[Comparative Example 2]
The entanglement process was carried out in the same manner as in Example 1, except that the air supply energy was changed to 1.6 kW. The results are shown in Table 2 below.

[Comparative Example 3]
The entanglement process was carried out in the same manner as in Example 1, except that the air supply energy was changed to 1.8 kW. The results are shown in Table 2 below.

[Comparative Example 4]
In the stretching step, the same procedure as in Example 1 was carried out, except that the stretching and fixing temperature was 200°C. The results are shown in Table 2 below.

[Comparative Example 5]
The procedure was carried out in the same manner as in Example 1, except that in the refueling step, a finishing agent containing no ionic surfactant was added so that the deposition rate was 1.1% by weight. The results are shown in Table 2 below.

[Comparative Example 6]
In the lubricating step, the same procedure as in Example 1 was carried out, except that a finishing agent containing 0.7% by weight of an ionic surfactant having the following composition was applied. The results are shown in Table 2 below.
(ionic surfactant)
(d1) alkyl (C10-16) sulfate sodium salt: 0.2 parts by weight (d2) alkyl (C12-18) acid phosphate, alkyl (C12-14) amine salt: 0.5 parts by weight

[Comparative Example 7]
In the refueling process, a finishing agent containing no ionic surfactant was applied so that the adhesion rate was 1.1% by weight, and the fiber tensile strength was 8.49 cN / stex, except that the fiber tensile strength was 8.49 cN / stex. conducted in the same way. The results are shown in Table 2 below.

[Comparative Example 8]
The entanglement process was carried out in the same manner as in Example 1, except that the air supply energy was changed to 0.8 kW. The results are shown in Table 2 below.

REFERENCE SIGNS LIST 1 spin head 2 spinneret 3 heating tube 4 cold air chamber 5 finishing agent application device 6 take-up roller 7 first roller 8 second roller 9 third roller 10 fourth roller 11 entanglement device 12 winder

Claims

A polyamide fiber for tire cords having an air knot strength of 3.5 cN/dtex or more and 6.0 cN/dtex or less under a temperature of 180°C.
The polyamide fiber for tire cord according to claim 1, wherein the number of intertrip entanglements is 13/m or more and 30/m or less.
The polyamide fiber for tire cords according to claim 1 or 2, having a 25°C air knot strength of 6.4 cN/dtex or more and 9.0 cN/dtex or less.
The polyamide fiber for tire cords according to claim 1 or 2, having a knot strength at 25°C of 4.5 cN/dtex or more and 6.5 cN/dtex or less.
The polyamide fiber for tire cord according to claim 1 or 2, having a tensile strength of 8.7 cN/dtex or more and 11.0 cN/dtex or less.
The polyamide fiber for tire cords according to claim 1 or 2, which has a dimensional stability of 12% or more and 20% or less.
The polyamide fiber for tire cords according to claim 1 or 2, wherein an ionic surfactant of 0.01% by weight or more and 0.1% by weight or less based on the weight of the fiber is applied to the surface.
The following physical properties (1) to (5):
(1) total fineness is 900dtex or more and 2500dtex or less;
(2) elongation is 15% or more and 25% or less;
(3) Boiling water shrinkage is 4% or more and 8% or less;
(4) Finishing agent adhesion rate is 0.5% by weight or more and 1.5% by weight or less; and (5) Number of single yarns is 100 or more and 400 or less;
Polyamide fiber for tire cord according to claim 1 or 2, which is a multifilament yarn having
The polyamide fiber for tire cord according to claim 1 or 2, which has an air knot portion.
A twisted yarn cord using the polyamide fiber for tire cord according to claim 9.
A blind fabric using the twisted yarn cord according to claim 10.
A method for producing a polyamide fiber for a tire cord, comprising: winding a polyamide fiber spun by melt spinning through one or more finishing agent applying devices and multi-stage stretching rollers, wherein the stretching fixing temperature of the multi-stage stretching roller is 205 ° C. The method for producing a polyamide fiber for a tire cord according to claim 1 or 2, wherein the temperature is at least 240°C.