JP3234295B2 - Method for producing polyhexamethylene adipamide fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyhexamethylene adipamide fiber (nylon 66 fiber), and more particularly to a high-strength polyhexamethylene adipamide fiber suitable for use in the field of rubber reinforcement such as tire cords. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Hitherto, polyhexamethylene adipamide fibers have been used for industrial materials, particularly tire cords and computer ribbons, because of their high fatigue resistance, heat resistance and high strength. JP-A-59-199812 discloses a method for producing a polyhexamethylene adipamide fiber having a breaking strength of 10.5 g / d. However, in recent years, the automobile industry has demanded higher performance and lighter weight for tires, and particularly demanded high-strength fibers having a breaking strength of 12 g / d.

We have made efforts to further increase the draw ratio based on the method disclosed in JP-A-59-199812, but have failed to achieve a strength of 12 g / d. Since polyhexamethylene adipamide has a very high crystallization rate, spherulites are liable to be generated, and the spherulites serve as an inhibitory factor in stretching. For this reason, the stretchability of the undrawn yarn in which the spherulites have grown remarkably deteriorates, and sufficient strength cannot be obtained. It is known that increasing the speed and volume of cooling air is effective to suppress spherulites, but in this case, the yarn sway becomes severe and the cooling becomes uneven. was there.

Japanese Patent Application Laid-Open No. 61-194209 discloses a cutting strength of 12
A method for producing g / d or more polyhexamethylene adipamide fibers is disclosed. However, this method requires special and complicated equipment, such as using a high-temperature pressurized steam nozzle and a slit heater with a temperature gradient to seal the space under the spinneret with an inert gas and further extend the film. Since the cost is high and the allowable range of the setting conditions is narrow, there are disadvantages such as easy generation of fluff and deterioration of the yield.

That is, although a fiber having a strength of 12 g / d can be obtained, it is easily industrialized due to the cost problem of requiring special equipment and the problem of yield such as fluff and yarn breakage. It's not a feasible way.

[0006]

SUMMARY OF THE INVENTION The main object of the present invention is to:
It is to solve the above points. In other words, the spinning and drawing equipment for producing tire cords and the like can be used as it is, without the need for a costly special device, and at a rate of 12 g / d.
It is intended to provide a method for stably producing a polyhexamethylene adipamide fiber having a high strength in a high yield with suppressing the occurrence of yarn breakage and fluff.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies based on the method disclosed in JP-A-59-199812 in order to achieve the above object, and as a result, polyhexamethylene adipamide was obtained. A non-aqueous finishing oil that suppresses the generation of spherulites in undrawn yarn, which is a draw inhibition factor, by blending and spinning thermoplastic polyamides with different repeating structural units By using a method of continuously stretching.
The draw ratio can be improved without using special equipment and conditions.
The present inventors have found that a high strength of 2 g / d can be obtained with good yield, and have reached the present invention.

That is, the present invention provides a formic acid having a relative viscosity VR of 7
5% or more of polyhexamethylene adipamide and 10% by weight or more of a thermoplastic polyamide having a different repeating structural unit.
0 wt% or less is blended and melt-spun, and a non-aqueous finishing oil is applied. Then, the undrawn yarn is subjected to continuous multi-stage drawing of two or more stages without winding, and at this time, the birefringence of the fiber Is set to a draw ratio of 60 × 10 ⁻³ or more.

The polyhexamethylene adipamide used in the present invention has a formic acid relative viscosity VR of 75 or more, and preferably VR of 80 or more. VR
Is 75 or less, even when stretched at a high magnification of 12 g
/ D or higher strength cannot be obtained. When the single-fiber fineness is as large as 6d as used in a normal tire cord, when spun with polyhexamethylene adipamide alone, many spherulites are observed in the drawn undrawn yarn. Since this spherulite becomes an inhibitory factor in stretching, it is difficult to sufficiently stretch. By blending and spinning a thermoplastic polyamide having different repeating structural units with polyhexamethylene adipamide, crystallization is suppressed, and spherulite generation can be suppressed.

The polyamide to be blended may be a meltable thermoplastic polyamide compatible with polyhexamethylene adipamide (nylon 66). For example, polycapramide (nylon 6), polytetramethylene adipamide (nylon 46), nylon 610, nylon 12, and the like. Preferably, it is a polycapramide, nylon 610.

The molecular weight of the polyamide to be blended is not particularly limited, but preferably is close to the molecular weight of the base polyhexamethylene adipamide. For example,
Polyhexamethylene adipamide has a formic acid relative viscosity VR of 8
When it is 0, the VR of the polyamide to be blended is also 8
It is better to use the one of 0. The polyhexamethylene adipamide and the polyamide to be blended may be obtained by a known production method, and may contain additives such as a heat stabilizer, an antioxidant, and a lubricant.

The blend amount of the polyamide to be blended is
It must be at least 10% by weight and at most 30% by weight. If the blend amount is less than 10% by weight, the effect of suppressing spherulites is small, and the stretching becomes insufficient. By blending 10% by weight or more, the number of generated spherulites can be suppressed to almost zero, and as a result, a strength of 12 g / d can be stably obtained. The blend amount is 30% by weight.
If it exceeds, the yarn properties are undesirably reduced. For example, since the wet heat resistance when a tire cord is dipped is greatly reduced, the heat resistance of polyhexamethylene adipamide cannot be utilized.

The method of blending is not specified, but for example, chips of polyhexamethylene adipamide may be blended with chips of another polyamide using a chip mixing device such as a tumbler. The blended chips are melted using an extruder or the like, and spun and stretched by the following method.

First, a molten polymer is extruded from a spinneret, and after cooling is delayed by a heating cylinder, the fiber is cooled and solidified by cooling air to form a fiber yarn, and then a non-aqueous finishing agent is applied by a finishing oiling device such as a roll. Apply oil agent.
At this time, if an aqueous emulsion type finishing oil is used, post-crystallization occurs due to the attached moisture, and it becomes impossible to achieve a desired strength due to poor stretching. Therefore, a non-aqueous finishing oil must be used.

Further, it is necessary to use a continuous drawing method in which drawing is performed directly and continuously after the spinning step. If the spinning step and the drawing step are separated, the undrawn yarn that has been wound once undergoes post-crystallization due to moisture in the air, so that it is impossible to draw sufficiently. For stretching, it is necessary to perform two or more-stage stretching using a heated godet roll.
With only one-stage stretching, it is difficult to perform high-magnification stretching so that the birefringence of the stretched yarn is 60 × 10 ⁻³ or more, and 12 g / g
The strength of d cannot be obtained.

When performing two-stage stretching, the temperature of the first godet roll is preferably selected from the range of 50 to 130 ° C., and the temperature of the second and third godet rolls is preferably selected from the range of 150 to 250 ° C. The stretching ratio of the first stage is 2.5 to
It is selected from among 4.0 times, and the draw ratio of the second step is 1.5-3.
It is good to choose from 0 times. The total draw ratio needs to be set so that the birefringence of the drawn yarn is 60 × 10 ⁻³ or more. By making the birefringence 60 × 10 ⁻³ or more,
A stretch strength of 12 g / d is obtained.

The temperature of the heated godet roll and the temperature
Since there is an appropriate value for the stretching distribution in the second stage and the second stage, the optimal value is set by trial and error. Next, winding is performed after slightly relaxing the final godet roll and the winding machine. As described above, formic acid relative viscosity VR is 75 or more, polyhexamethylene adipamide is blended with a thermoplastic polyamide having a different repeating structural unit, and spun, thereby suppressing spherulite generation and further imparting a non-aqueous finishing oil agent. A continuous multi-stage stretching is performed later, and a combination of these methods of performing stretching while preventing post-crystallization is used, without using special equipment, to set a stretching ratio at which the birefringence is 60 × 10 ⁻³ or more. It is possible to wind a fiber having a strength of 12 g / d with a high yield while suppressing the occurrence of yarn breakage and fluff.

[0018]

The present invention will be described below in detail with reference to examples. The measurement method and the like used here are shown. Relative viscosity of formic acid VR A polymer chip was dissolved in a 90% by weight formic acid aqueous solution to a concentration of 8.4% by weight, and the solution was dissolved in a formic acid tube using a viscosity tube.
It is a relative viscosity with respect to a 90% by weight aqueous solution of formic acid measured at 5 ° C. Method for measuring strength and elongation of drawn yarn After leaving the sample in a measuring room at a temperature of 20 ° C. and a relative humidity of 65% for one day, an autograph S-1 (trade name, manufactured by Shimadzu Corporation)
The measurement was performed using 00. A tensile test was performed on a 25 cm sample to which a twist of 80 times / m was applied at a descent speed of 30 cm / min. Observation method of spherulite The cross section of the undrawn yarn collected by winding on a pretension roller was observed using a polarizing microscope, and the number of spherulites generated was measured. Birefringence of drawn yarn Observing the wound drawn yarn with a polarizing microscope, the birefringence Δn
I asked. The number of fluffs of the drawn yarn was observed for 3 minutes with a strobe light during the winding, and the number of fluffs counted was converted into the number of drawn yarns per 1000 m in length. Winding yield The winding of 5 kg of cheese (winding for 23 minutes) was repeated 10 times, and the result was shown by the obtained ratio of full cheese. When the yield was 0%, the possible winding time was also shown. Moisture / heat resistance measuring method A dip cord wound around a frame of 40 cm width is 50 m
The mixture was placed in a 1-liter autoclave containing 1 l of water, sealed, heated to 160 ° C., and heated at this temperature for 4.5 hours. Take it out, temperature 25 ° C, relative humidity 5
After leaving to dry in a 5% constant temperature and humidity room for one day, a tensile test was performed to measure the strength. Then, the retention ratio of the strength to the strength before the heat treatment was calculated and obtained.

[0019]

EXPERIMENTAL EXAMPLE 1 (Examples 1 to 5 and Comparative Examples 1 to 8) A chip of polyhexamethylene adipamide (nylon 66) was mixed with a chip of polycapramide (nylon 6) as a blend component. Each was blended using a tumbler so as to be 30, 40, and 50% by weight, and spinning and stretching were performed using an extruder under the following conditions. <Spinning conditions> Fineness 1260d Number of filaments 210f Spinneret hole diameter 0.23mmφ Number of holes 210 Holes Melting temperature 300 ° C Heating cylinder length 15cm Temperature 300 ° C Cooling air temperature 20 ° C Wind speed 0.5m / s Finish oil adhering Amount 2.0% vs. polymer <Elongation condition> First godet roll temperature 65 ° C Second godet roll temperature 215 ° C Third godet roll temperature 220 ° C First stage stretching ratio Total stretching ratio / 2.0 Second stage stretching ratio 2 0.0 × Final winding speed 1600 m / min At this time, the stretching ratio was selected so that the birefringence of the drawn yarn was 60 × 10 ⁻³ or more, and the setting was made so as to obtain a strength of 12 g / d. As for the condition where a strength of 12 g / d cannot be obtained, the maximum stretch ratio at which stretch winding can be performed was selected.

Tables 1 and 2 show the occurrence of spherulites in the undrawn yarn and the physical properties of the drawn yarn. Further, the number of fluffs and the yield in performing the stretching winding are also shown. As shown in Examples 1 to 5, 10 to 30% by weight of polycapramide was blended, and a continuous stretching was performed after using a non-aqueous finishing oil, whereby the birefringence Δn became 60 × 10 ⁻³ or more,
A drawn yarn having a strength of 12 g / d was obtained. At this time, the number of fluffs generated was small and the yield was good.

Meanwhile, and if it exceeds polycarbonate <br/> and 40 wt% blend ratio is less than 10% by weight of the flop La bromide as shown in Comparative Examples 1-8, Ya case of using the aqueous emulsion system finishing oil When another stretching is performed, it is difficult to set a stretching magnification to make the birefringence Δn to be 60 × 10 ⁻³ or more, and it is impossible to stably obtain a strength of 12 g / d. Even if 12 g / d could be obtained, fluff was generated frequently and the yield was almost 0%, and stable production could not be performed.

[0022]

EXPERIMENTAL EXAMPLE 2 (Examples 1 to 5 and Comparative Examples 1 to 5) The drawn yarn samples of Examples 1 to 5 and Comparative Examples 1 to 5 were twisted 39 times / 10 cm (S) by a ring twisting machine.
Twist) and the number of lower twists was 39 times / 10 cm (Z twist) to obtain a raw cord. Next, this raw code is placed at 160 ° C.
After a tension heat treatment with a tension of 1.3 g / d, a dipping treatment of an adhesive, that is, a resorcinol-formaldehyde-latex liquid (RFL liquid) was performed using a three-stage oven hot stretch apparatus (computer treater). Got dip code.

The conditions of the dipping process are shown below. <Dipping conditions> Atmospheric temperature (° C) Tension (Kg / cord) Tensile heat treatment zone 160 3.6 First zone 225 3.6 Second zone 225 2.8 Third zone 225 1.8 Processing speed 15 m / min Tables 1 and 2 show the results of measuring the moisture and heat resistance of the dip cord. Looking at the value of wet heat resistance, when the blending amount of polycapramide is 30% by weight or less, a strong retention of 80% or more is exhibited, but when it exceeds 30% by weight, the strength retention is remarkably reduced to about 20%. Rate is 30
It has been found that it is necessary to keep the content to not more than% by weight.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

EFFECT OF THE INVENTION In order to suppress the generation of spherulites and to prevent post-crystallization by blending and spinning a thermoplastic polyamide having a repeating structural unit different from polyhexamethylene adipamide having a formic acid relative viscosity VR of 75 or more. By performing continuous multi-stage drawing after applying the non-aqueous finishing oil, the birefringence can be maintained at 60 without using special equipment.
It is possible to set a draw ratio of × 10 ⁻³ or more, and it is possible to stably produce a fiber having a strength of 12 g / d with good yield by suppressing yarn breakage and fluff.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a test spinning machine and a drawing machine used in Examples of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Spin head 2 Spinneret 3 Heating cylinder 4 Filament 5 Cooling air chamber 6 Oiling roll 7 Pretension roll 8 First godet roll 9 Second godet roll 10 Third godet roll 11 Winding machine

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-194209 (JP, A) JP-A-59-199812 (JP, A) JP-A-54-30957 (JP, A) JP-A-54-957 30958 (JP, A) JP-A-54-11324 (JP, A) JP-A-4-1533311 (JP, A) JP-A-3-185110 (JP, A) JP-A-3-199420 (JP, A) JP-A-3-241007 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) D01D 5/096 D01F 6/90 311

Claims (1)

(57) [Claims] 1. A non-aqueous finishing oil which is prepared by blending thermoplastic polyamides having different repeating structural units in an amount of 10% by weight or more and 30% by weight or less with polyhexamethylene adipamide having a formic acid relative viscosity VR of 75 or more and melt-spinning. Is applied, and the multi-stage drawing of two or more stages is performed continuously without winding the undrawn yarn once, and the birefringence of the fiber is 60 × 10
^A method for producing a polyhexamethylene adipamide fiber, wherein a draw ratio is set to ^-3 or more.