JP2559866B2 - Method for producing high fatigue resistance and high strength polyhexamethylene adipamide fiber - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a high-strength polyamide fiber suitable for use in the field of rubber reinforcement such as a tire cord. More specifically, the present invention relates to a method for producing high-strength polyhexamethylene adipamide fiber which maintains high strength as usual and has significantly improved fatigue resistance.

[Conventional technology]

Since high strength of polyhexamethylene adipamide fiber can be easily achieved, development has been made for a long time for rubber reinforcing fiber such as tire cord.

Since high-strength polyhexamethylene adipamide fiber is high-strength and has higher fatigue resistance than polyester fiber, it has been widely used as a tire cord in bias tires for heavy vehicles such as trucks and buses. It was But,
With the recent trend toward higher speeds and higher weight ratios of automobiles, further improvement in fatigue resistance is required, and it is clear that conventional high-strength hexamethylene adipamide fiber cannot meet the demand. It has become.

Japanese Patent Publication No. 48-32616 discloses a breaking strength of 10.1 g / d and a breaking elongation of 17.5% obtained by specifying the conditions of the direct spinning and drawing method using polyhexamethylene adipamide having a relative viscosity of 70 formic acid. High tenacity polyhexamethylene adipamide fibers are disclosed (Example 2). However, the fatigue fracture time measured by the Goodyear tube fatigue fracture test method, which is a measure of the fatigue resistance of this fiber, is 610 minutes,
It is an extremely low level (in the present invention, it is 1500 minutes or more as described later). Further, in this prior art, there is no description or suggestion of the relationship between the relative viscosity of formic acid and the finish or its application method and fatigue resistance.

JP-A-59-9209 discloses a formic acid relative viscosity of 80.0 obtained by solid phase polymerization and a formic acid relative viscosity of 90.0 obtained by specifying a spinning method and a stretching method from a raw material having a relative viscosity of 100.0 g / breaking strength.
d, a high tenacity polyhexamethylene adipamide fiber having a breaking elongation of 21.0% and a tie molecular stability coefficient of 0.09 is disclosed (Example 1). The feature of this fiber is that the decrease in strength in the vulcanization step in the tire manufacturing process is small. However, this prior art does not describe the fatigue resistance of the obtained fiber at all, let alone the relationship between the relative viscosity of formic acid and the finish or its application method and the fatigue resistance.

Japanese Unexamined Patent Publication (Kokai) No. 61-194209 discloses a high-strength polyhexamethylene adipamide fiber having a surface treatment with a non-aqueous finishing agent, which has ηr = 3.33 (this is converted to a relative viscosity of formic acid of about 95) ( Example 31). This fiber has achieved high tenacity in the drawing process by using a special means such as a steam jet in the first stage and a non-contact heater in the second stage. The fiber length period is 118Å and the breaking strength is 13.1 g / d, breaking elongation 15.0%. There is no mention or suggestion in this prior art of the fatigue resistance of this fiber.

JP-A-63-159541 proposes a method for producing a high-strength polyamide fiber in which nylon 66 is spun at 1500 m / min or more, continuously multistaged, and then wound at 4000 m / min or more. . It describes that a fiber having a breaking strength of 11.5 g / d, a breaking elongation of 14.2% and a fatigue breaking time of 833 minutes was obtained. The tube fatigue failure time of these fibers is 1043
Minutes or less, far below the level of 1500 minutes achieved by the present invention.

JP-A-60-88116 discloses a spinning speed of 1000 to 6000 m /
By drawing an undrawn yarn of polyhexamethylene adipamide spun at a speed of 100 m / min or less, the fatigue fracture time exceeds 1500 minutes. Mid fibers are disclosed.
However, with this fiber, the toughness of the yarn is small and the strength is low.
Those with 10 g / d and elongation exceeding 18% were not obtained. Further, there is no suggestion as to the relationship between the fatigue resistance and the finish or the method of applying the finish.

JP-A-63-91235 discloses a polyhexamethylene adipamide tire yarn surface-treated with a non-aqueous finishing agent (neat oil) (Examples A, B, C, D, E).
This polyamide tire yarn has a hydrophobic organic ester immersion modifier (contained in neat oil) with a melting point higher than 27 ° C on its surface, and has low rigidity and high air permeability. Polyhexamethylene adipamide fibers convertible into tire cords by means. The polyhexamethylene adipamide used in this fiber has a formic acid relative viscosity of 70 and there is no mention of fatigue resistance of this fiber in the prior art,
There is no description or suggestion of the effect of neat oil on fatigue resistance.

JP-A-63-50519 discloses a high-strength poly with improved fatigue resistance obtained by a method in which polyhexamethylene adipamide having a relative viscosity of formic acid of 90 is melt-spun at a relatively high speed and then subjected to multi-stage drawing. Hexamethylene adipamide is disclosed. Although the fiber had improved fatigue resistance, the fiber had a breaking strength of 9 g / d or less, and the mechanical properties were reduced to unsatisfactory levels for rubber reinforcement. Also, the fatigue fracture time is less than 1500 minutes.

[Problems to be Solved by the Invention]

Satisfies recent requirements for high-strength polyamide fibers suitable for rubber reinforcement such as tire cords, that is, high mechanical properties are better than before, and fatigue fracture time of 1500 minutes or more in Goodyear tube fatigue fracture test. It is an object of the present invention to provide a high tenacity polyhexamethylene adipamide fiber exhibiting excellent fatigue resistance.

As a result of intensive studies aimed at achieving the above object, the present inventors have found that polyhexamethylene adipamide has a molecular weight above a certain level, that is, a relative viscosity of formic acid and a finishing agent of a specific composition in a synergistic manner. The present invention has been completed by finding that fatigue resistance is improved.

[Means for solving the problem]

The object of the present invention is to provide a high-strength polyhexamethyleneadipamide fiber having a breaking strength of 10 g / d or more and a breaking elongation of 18% or more, wherein 95 mol% or more is composed of repeating units of polyhexamethylene adipamide. When produced by a multi-stage drawing method, the polyhexamethylene adipamide forming the fiber is melt-spun so that the relative viscosity of formic acid is 85% or more, and the spun yarn is treated with a non-aqueous finishing agent, This is achieved by a method for producing high-strength fatigue-resistant and high-strength polyhexamethylene adipamide fiber, which is characterized by multi-stage drawing.

In the polyhexamethylene adipamide of the present invention,
More than 95 mol% must be formed from hexamethylene adipamide repeat units. If it is less than 95 mol%, the melting point of the polymer is significantly lowered, and not only the heat resistance, which is a characteristic of polyhexamethylene adipamide, is impaired, but also high strength cannot be obtained. It is preferable that 98 mol% or more is formed of hexamethylene adipamide repeating units.

In the present invention, the breaking strength of the polyhexamethylene adipamide fiber must be 10 g / d and the breaking elongation must be 18% or more. If the breaking strength and / or the breaking elongation is less than this value, the toughness becomes insufficient when the tire cord is used and the tire cord becomes insufficient even if the relative viscosity of formic acid of the polymer is increased.

In the present invention, the polyhexamethylene adipamide forming the fiber must be melt-spun so that the relative viscosity of formic acid is 85 or more. Polyhexamethylene adipamide that forms fibers by adjusting the relative viscosity of formic acid, the water content, the polymer temperature during melt spinning, the residence time, and the stretching conditions of the raw material polymer used in consideration of equilibrium reaction and decomposition reaction. The relative viscosity of formic acid can be set. The formic acid relative viscosity is preferably in the range of 95 to 150, more preferably 95 to 135 in view of the ease of melt spinning.

In the present invention, the spun yarn must be surface-treated with a non-aqueous finishing agent. In the melt spinning method, a surface treatment is usually performed with a finishing agent before stretching, but in the present invention, a non-aqueous finishing agent containing no water is required instead of a water-based finishing agent obtained by dispersing the finishing agent in water.
There are two types of non-aqueous finishes, a neat type for directly applying crude oil itself and a diluting system for diluting in an organic solvent such as kerosene.

The finishing agent is mainly composed of a smoothing agent composed of a fatty acid ester or the like and an emulsifying agent composed of a nonionic surface active agent or the like, and often further contains a heat stabilizer, an antioxidant and an antistatic agent. Aqueous finishing agents are usually given emulsifying ability in water by increasing the content of emulsifier,
On the other hand, the non-aqueous finishing agent has a low emulsifier ratio and is mainly composed of a smoothing agent. Usually, the proportion of emulsifier in the non-aqueous finishing agent is 20% by weight or less. The present invention also includes a method of using a crude oil as a non-aqueous finish agent without dispersing a water-based finish agent in water.

The adhesion of the finishing agent to the fibers is preferably 0.5 to 2.0% by weight, more preferably 0.8 to 1.6% by weight.

Examples of the leveling agent in the finishing agent in the present invention include oleyl oleate, isostearyl oleate, esters of higher alcohols and higher fatty acids, dioleyl adipate diisostearyl sebacate, esters of higher basic alcohols, and trihydric alcohols. Esters of aromatic carboxylic acids and higher alcohols such as isodecyl trimellilate, and polyhydric alcohols such as neopentyl glycol dilaurate, glycerin trioleate, and pentaerythritol tetradecaneate and higher fatty acid esters.

Further, as an emulsifier in the finishing agent in the present invention, that is, a nonionic surfactant, ethylene oxide adducts of polyhydric alcohols such as glycerin and sorbitan, higher fatty acid esters such as oleic acid and lauric acid, and natural oils and fats such as castor oil Examples thereof include those obtained by adding ethylene oxide, those obtained by adding ethylene oxide to higher alcohols, higher amines, alkylphenols and the like.

The method for producing the high-strength polyhexamethylene adipamide fiber of the present invention will be further described.

First, a prepolymer containing a stabilizer such as copper acetate and potassium iodide and having a relative viscosity of formic acid of 40 to 50 is produced by a known melt polymerization method to obtain polymer pellets. Then, the polymer pellets are made to have a high molecular weight to a relative viscosity of formic acid of 90 or more by a known solid-state polymerization method. This high molecular weight polymer is subjected to melt spinning and subsequent multi-stage drawing using an apparatus as illustrated in FIG. 1 to obtain high strength polyhexamethylene adipamide fiber.

That is, the melted polymer is extruded from the spinneret 2 mounted on the spin head 1 to form filaments 4, the cooling is delayed in the heating cylinder 3, and then cooled and solidified in the cooling air chamber 5 by the cooling air. Then, after applying a finishing agent by a finishing agent applying device (oiling roll 6), it is guided to a stretching machine and godet rolls 8, 9, 10, 11 at each stage
It is heated in the following manner, stretched in multiple stages according to a conventional method, and wound by a winder.
The undrawn yarn obtained by spinning may be once wound and then drawn.

At that time, the spinning temperature, the water content of the polymer pellets to be supplied, and the drawing conditions are adjusted so that the relative viscosity of formic acid of the obtained fiber becomes 85 or more. Further, in order to apply the non-aqueous finishing agent to the fibers, a known oiling roll as shown in FIG. 1 may be used, or a known oiling nozzle may be used. In addition, since the viscosity of the finishing agent is high, it is desirable to heat it to 40 to 70 ° C. before applying.

The spinning speed is preferably from 200 m / min to 800 m / min in order to obtain fibers having higher breaking strength and breaking elongation.

〔Example〕

The method for producing the high fatigue resistance and high strength polyhexamethylene adipamide fiber of the present invention will be described below based on Examples. Prior to the description of the embodiments, definitions of various technical terms used in the present invention and measurement methods thereof will be described. Various measuring methods used in the examples of the present invention are shown below.

(1) 90% formic acid relative viscosity The formic acid relative viscosity is the relative viscosity at 25 ° C. of a solution prepared by dissolving 90% formic acid in a polymer concentration of 8.4% by weight.

(2) Strength and elongation Using Autograph S-100 manufactured by Shimadzu Corporation, a descending speed of 30 cm was applied to a sample of 25 cm raw yarn with 80 twists / m of twist.
/ Min, chart speed 60 cm / min, full scale 25 kg.

(3) The dry heat shrinkage is calculated according to the following formula after freely shrinking a 1.0 m raw yarn with a twist of 80 times / m in an air oven at 160 ° C. for 30 minutes.

l ₁ : Yarn length after heat treatment (cm) (4) Goodyear tube fatigue test According to JISL-10173 / 2.2.1A method.

Tube shape Inner diameter 12.5mm Outer diameter 26mm Length 230mm Bending angle 90 ° Inner pressure 3.5kg / cm ² G Rotation speed 850rpm Vulcanization condition 140 ℃ × 40min (5) Vulcanization cord strength, elongation Treatment cord is embedded in rubber After vulcanizing under free shrinkage at 155 ° C for 40 minutes, the vulcanized rubber is broken, the vulcanized cord is taken out, and the strength and elongation are measured by the method shown in (1).

Example 1 and Comparative Example 1 A formic acid relative viscosity of 82,91,102,120,
151 polyhexamethylene adipamide (100% hexamethylene adipamide repeating unit) pellets were obtained. The polymer pellets contain cupric acetate corresponding to a copper content of 170 ppm, potassium iodide corresponding to an iodine content of 1300 ppm, and 30 ppm of titanium oxide.

The polymer pellets were directly spun and drawn at 1260 denier / 2 by using the melt spinning machine and the drawing machine shown in FIG.
High strength polyhexamethylene adipamide fiber of 10f was used. At that time, two kinds of finishing agents were used. One of them (finishing agent A) was a non-aqueous finishing agent applied as crude oil (as neat oil), and the other (finishing agent B) was a finishing agent having emulsifying ability in water and applied as an aqueous emulsion. The compositions of finishes A and B are shown in Table 1.

The spinning conditions and stretching conditions were as follows.

・ Spinning conditions Polymer discharge rate 200g / min Spinneret Pore diameter 0.25φmm, Pore length 0.375m, Pore number 210 Spinning temperature (spin head temperature) 300 ℃ Heating tube length 300mm, Inner temperature 300 ℃ Cooling air temperature 20 ℃, Humidity RH65 %, Wind speed 0.8m / s Oiling Oiling roll diameter 150φmm Oiling roll speed Finishing agent A 9rpm Finishing agent B 5rpm Finishing agent temperature Finishing agent A 50 ℃ Finishing agent B Room temperature Spinning speed (pretension roll peripheral speed) 278.4m / min ・Drawing conditions Circumferential speed (m / min) Temperature (℃) 1st godet roll 292.2 80 2nd godet roll 833 215 3rd godet roll 1666 220 4th godet roll 1666 220 Winding speed 1500m / min Is calculated as follows.

Total draw ratio = 1.05 x 2.85 x 2.00 x 1.00 x 0.90 = 5.39 Table 2 shows the physical properties of the obtained fiber. Next, using a ring twisting machine, the obtained fiber is twisted 39 times / 10 cm (S
Twisting), then 39 twists per 2 twist yarns
M (Z twist) was twisted to make a raw cord. The physical properties of the raw cord are shown in Table 3.

Next, the raw cord was treated with an adhesive, that is, a resorcin-formaldehyde-latex (RFL) liquid, using a 3-oven hot stretcher (Computer) to obtain a treated cord. Physical properties of the treated cord are shown in Table 4. The hot stretch conditions at that time are as follows.

Hot stretch conditions Temperature (℃) Tension (kg) 1st zone 160 1.45 2nd zone 227 2.8 3rd zone 227 1.8 Treatment speed 15m / min Physical properties of the obtained treated cord, physical properties of vulcanized cord and tube fatigue of Goodyear method The breaking time is shown in Table 4.

As shown in Tables 2, 3, and 4, formic acid relative viscosity of 85 or more, breaking strength of 10 g / d or more, breaking elongation of 18% or more, and surface treatment with a non-aqueous finishing agent The polyhexamethylene adipamide fiber of Example 1 (Test No. 1,2,3,4) shows high fatigue resistance with a fatigue failure time of 1500 minutes or more and high treated cord strength.

Example 2 and Comparative Example 2 Pellets of polyhexamethylene adipamide (100% consisting of repeating units of hexamethylene adipamide) having a relative viscosity of formic acid of 110 were obtained by the solid phase polymerization method. The polymer pellet contains the same amount of the same additives as the polymer pellet used in Example 1.

These polymer pellets were directly spun and drawn in 1890 denier / 312 using a melt spinning machine and a drawing machine shown in FIG.
High strength polyhexamethylene adipamide fiber of f was obtained.
At that time, four kinds of finishing agents were used. Two of them (finishing agents C and D) are non-aqueous finishing agents that are applied as crude oil (as neat oil), and the other two (finishing agents E).
And F) are finishing agents having emulsifying ability in water and were applied as an aqueous emulsion. The composition of the finishing agents C, D, E and F is the fifth one.

The spinning conditions and stretching conditions were as follows.

・ Spinning conditions Polymer discharge rate 568g / min Spinneret hole diameter 0.26φmm, hole length 0.39mm, number of holes 156 × 2 Spinning temperature (spin head temperature) 300 ℃, heating tube length 300mm, internal temperature 180 ℃ Cooling air temperature 20 ℃ , Humidity RH65%, Wind speed 0.75m / s Oiling Oiling roll diameter 65φmm Oiling roll rotation speed Finishing agent C, D 54rpm Finishing agent E, F 7.0rpm Finishing agent temperature Finishing agent C, D 50 ℃ Finishing agent E, F Room temperature Spinning speed (Pretension roll peripheral speed) 577.1 ・ Stretching condition Circular speed (m / min) Temperature (℃) 1st godet roll 583 80 2nd godet roll 1530 215 3rd godet roll 3060 220 4th godet roll 3060 150 Winding speed 2800m / min Therefore top From the above conditions, the total draw ratio is calculated as follows.

Total draw ratio = 1.01 x 2.26 x 2.00 x 0.92 = 4.86 Physical properties of the high-strength polyhexamethylene adipamide fiber obtained under the above conditions are shown in Table 6.

Next, the cord characteristics of the obtained yarn were evaluated. First, using a twisting machine, the number of twists is 32 times / 10 cm (S
Twist) Twisted 32 twists for each 2 twists
A twist and 10 cm (Z twist) twist was applied to make a raw cord. The physical properties of the obtained raw cord are shown in Table 7.

Next, the raw cord was treated with an adhesive, that is, a resorcin-formamide-latex (RFL) liquid using a 3-oven hot stretcher (Computer) to obtain a treated cord. The conditions for the adhesive treatment are shown below.

Hot stretch condition Temperature (℃) Tension (kg) 1st zone 160 2.08 2nd zone 228 4.15 3rd zone 228 2.28 Treatment speed 15m / min Physical properties of the obtained treated cord and tube fatigue failure time of Goodyear method are shown in Table 8. Is like.

As shown in Tables 6, 7, and 8, formic acid relative viscosity of 85 or more, breaking strength of 10 g / d or more, breaking elongation of 18.0%
The polyhexamethylene adipamide fiber of Example 2 which has been surface-treated with the above non-aqueous finishing agent shows not only high treated code toughness but also high fatigue resistance of 1500 minutes in fatigue breaking time.

Example 3 and Comparative Example 3 Polyhexamethylene adipamide fiber was produced by the same method and conditions as in Example 2 and Comparative Example 2 except for the finishing agent. That is, two types of fibers having relative viscosities of formic acid of 96 to which finishes G and H were added were manufactured. Finishing agent G
In Example 3, a non-aqueous finishing agent was used as crude oil, and as a finishing agent H (Comparative Example 3), an aqueous emulsion was used. The compositions of finishes G and H are shown in Table 9. The physical properties of the obtained polyhexamethylene adipamide fiber are 10th.
Shown in the table.

These fibers were twisted under the same method and conditions as in Example 2 to form a raw cord, and then subjected to a dipping treatment to obtain a treated cord. Physical properties of the raw cord and the treated cord are shown in Table 11 and Table 12, respectively.

The fiber of Example 3 surface-treated with the non-aqueous finishing agent G is
It exhibited a high fatigue failure time of over 1500 minutes.

[Effects of the Invention] The high-strength polyhexamethylene adipamide fiber of the present invention, when used as a tire cord, retains high toughness (strength x elongation) as in the conventional case and has extremely high fatigue resistance. Show. This not only extends the life of bias tires for heavy-duty vehicles such as trucks and buses, but also makes it possible to obtain tires suitable for high-speed running.

[Brief description of drawings]

FIG. 1 shows a test spinning machine and a stretching machine used in Examples of the present invention. 1 ... Spin head, 2 ... Spinneret, 3 ... Heating cylinder, 4 ... Filament, 5 ... Cooling air chamber, 6 ... Oiling roll, 7 ... Pre-tension roll, 8 ... First godet roll, 9: second godet roll, 10: third godet roll, 11: fourth godet roll, 12: winder.

Claims (1)

(57) [Claims] 1. 95 mol% or more is made up of polyhexamethylene adipamide repeating units, and has a breaking strength of 10 g / d or more and 18
When a high-strength polyhexamethylene adipamide fiber having a breaking elongation of at least 10% is produced by a multi-stage drawing method, the relative viscosity of formic acid of polyhexamethylene adipamide forming the fiber is
Production of highly fatigue-resistant and high-strength polyhexamethylene adipamide fiber characterized by melt-spinning to 85% or more, treating the spun yarn with a non-aqueous finishing agent, and then performing multi-stage drawing Method.