JPS5926517A - Preparation of nylon 66 yarn having high strength and high modulus - Google Patents

Abstract

PURPOSE:To obtain yarn having high strength and high modulus, having improved adhesiveness and durability, by drawing nylon 66 yarn spun at high-speed, under conditions to satisfy specific tension, temperature, heating zone, etc., quenching it. CONSTITUTION:Nylon 66 yarn spun at >=4,000m/minute spinning speed is heat- treated at 0.5g/d-0.99Tg/d tension (d is denier, and T is breaking tension of the yarn) in an atmosphere substantially containing no oxygen at a temperature exceeding Tm1 of DSC melt curve (the temperature at which the melt curve releases from the base line) and not exceeding Tm3 (the temperature at which the melting of the yarn is finished) in a heating zone having the length l (mm.) in the direction of fiber axis satisfying the formula [v is treatment speed (mm./minute), and theta is heat-treatment temperature ( deg.C)], and the yarn is immediately quenched to <= the glass transition temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing nylon 66 fibers having a special structure.

Nylon 66 fiber is superior in strength, modulus of elasticity, fatigue resistance, and adhesion to rubber compared to other fibers, and is therefore widely used as fiber for tire cords and as a reinforcing agent for various resins. However, in recent years, advances have been made in the modification and improvement of other fibers, and fibers have appeared that have properties approaching or comparable to those of nylon 66 fibers, with the exception of adhesive properties. Therefore, there is a demand for the development of nylon 66 fibers that take advantage of their excellent adhesive properties and have even higher strength and higher modulus of elasticity.

In order to meet the above-mentioned demands, the physical properties of tire cords have been improved by cold stretching, hot stretching, etc.

However, with this method, it becomes difficult to maintain mechanical properties during high-temperature bonding with rubber or after long-term use. Looking at this phenomenon from the perspective of the microstructure of the fiber, we can see that the tie molecules (which are strong and play a major role in maintaining the elastic modulus) that are extremely tensed during cold stretching are cut when heated or when tires are used for long periods of time.
It is thought that this causes a decrease in the strong elastic modulus.

As a result of intensive research into the relationship between the strength and elastic modulus of nylon 66 fibers and the microstructure of the fibers, the present inventors found that when fibers have a special microstructure (i.e., a structure mainly composed of extended molecular chains), found that the strength and elastic modulus of fibers were significantly increased, and established a new manufacturing method for producing such fibers.

Typical fibers obtained in the present invention are 20'C, 60%R
, H, is a nylon 66 fiber with an initial modulus of 60y-76 or more, and the temperature (Tmax 'C ) satisfies the following formula 1 formula %, the peak value (-δ) maX is 0.095 or less, and the average refractive index n7(0) and n□(0 ) are each formula 1.585
0≦n/(Oi≦1.6 i o o and 1.5
High strength that satisfies 100≦n(.)≦1.5300.
It is a high modulus nylon 66 fiber.

The "nylon 66 fiber" used in the present invention means a fiber consisting essentially of polyhexamethylene azinamide polymerized from hexamethylene diamine and adipic acid; The fibers may be copolyamide fibers containing a small amount of other copolymer components, or may be fibers composed of a mixture with other polymers, as long as the properties of the fibers are not substantially impaired. Also, usually
It may also contain additives used in synthetic fibers, such as matting agents, stabilizers, antistatic agents, etc. The higher the polymerization degree of the nylon 66 fibers, the higher the mechanical breaking strength, so it is desirable, and it is particularly desirable that the number average molecular weight is 43,000 or more.

The first feature of the method of the present invention is that the spinning speed is 4.000 m5/n.
The point is that high speed spun fibers spun at 11n or more are used. Here, "spinning speed" means the take-up speed of the take-up roll (7) in a spinning device as shown in FIG. The basic principle underlying the present invention is to focus on the extended molecular chains with high melting points contained in I-no-fi, and zone-melt the other low-melting point crystal parts under high tension to separate the molecular chains. Stretching and subsequent rapid cooling process recrystallizes into stretched molecular chain crystals (
(self-improvement, crystallization), and at the same time, the fully extended molecular chains of the amorphous region are also immobilized. Therefore, the fibers used need to contain more extended molecular chains.

Fibers with a spinning speed of less than 4,000 m/ml contain almost no extended molecular chain crystals, but
Fibers spun at in or more are elongated and have many molecular chains. The higher the spinning speed, the more elongated molecular chains are included. This is why fibers spun at a spinning speed of 4,000 m/min or higher are used in the present invention.

-F1 It is more preferable that the fiber is a high speed spun fiber spun at a spinning speed of 5.500 m/min or more.

The second feature of the method of the present invention is that the tension per unit fineness (denier) applied to the yarn during heat treatment is multiplied by the tension TK 0.99 at the time of yarn breakage at 0.5 f or more, which is 0.99.
The point is to keep it below T. If the tension is less than 0.5, the molecular chains in the region melted by zone melting will not be sufficiently stretched and will be fixed in the subsequent quenching zone, so that no significant increase in strength or elastic modulus will occur. Also,
If it exceeds 0.99T (b), thread breakage will occur during zone melting, making processing impossible in many cases, and
Even if it is not impossible, macroscopic defects are likely to occur, the strength and modulus of elasticity are reduced, and the fatigue resistance is also inferior.

A third feature of the method of the present invention is that the treatment is carried out in an atmosphere substantially free of oxygen. As mentioned above, the zone melting process is performed at a fairly high temperature, so if oxygen is present in the atmosphere, oxidative decomposition of the fibers will occur, resulting in a decrease in strength and elastic modulus. Therefore, the heat treatment is performed in an inert gas atmosphere such as nitrogen gas. It is more desirable to carry out the treatment in a vacuum because it prevents oxidative decomposition of the yarn, increases the degree of polymerization of the yarn, and improves the mechanical properties of the yarn.

The fourth characteristic of the method of the present invention is that the DSC (differential scanning calorimetry) melting curve of the yarn exceeds Tm1 (the temperature at which the melting curve departs from the baseline) and is below Tm3 (the temperature at which the melting of the fiber is completed). It is at the point where zone melting occurs within the range of .

Zone melting here is an operation in which the fiber is heated in as narrow a region as possible to melt the crystal region other than the stretched molecular chains. In order to heat the yarn as evenly as possible and to concentrate stress in the heating area most efficiently, the length t in the fiber axis direction of the heating zone where the yarn is heated is
are processing speed V (f/m1n), processing humidity θ (℃)
, a relational expression consisting of yarn fineness d (denier): 1≦t≦1
+□, 519 must be satisfied.

The temperature at which the yarn is heated by zone melting is the D of the yarn.
It is necessary that the humidity (°C) exceeds Tm1 of the SC melting curve and the temperature range does not drop Tm5. The method for measuring the DSC melting curve and the definition of Tm1+Tm, 5 are as described below. If the thread is heated below Tm1, the folded crystals and other microcrystals will not be melted and a structure mainly composed of molecular chains cannot be produced. Furthermore, if the yarn is heated to a temperature higher than Tm5, the yarn will completely melt and breakage will occur, making zone melting treatment impossible.

If the heating temperature is in the range of more than Tm1 and less than Tm3, the yarn will have a structure mainly composed of elongated molecular chains with a higher melting point, and its strength and elastic modulus will increase significantly. Note that the heating temperature range is Tm
2 or more and less than Tm3 is more desirable in terms of strength and elastic modulus, but in this case it is necessary to set the cooling rate to 20° C./IIec or more.

A fifth feature of the method of the present invention is that zone melting is immediately followed by rapid cooling in a cooling zone whose temperature is controlled to be below the glass transition temperature of the nylon 66 fibers.

In particular, if the time it takes for the yarn to enter the cooling zone after passing through the heating zone is within 10 seconds, the heating and cooling treatment effect will be fully exhibited.

In addition, the faster this cooling rate, the greater the processing effect of the heating and cooling zone, and the closer the temperature is to the limit (
(near Tm3) becomes possible.

Therefore, the quenching rate is desirably 10° C./'8 e n or higher, more preferably 20° C./II 86 or higher.

The cooling temperature needs to be lower than the glass transition temperature in order to cause recrystallization (self-seeding crystallization) into stretched molecular chain crystals and to fix molecules stretched in the fiber axis direction of the amorphous region. When the cooling temperature is higher than the glass transition temperature,
Since the extended molecular chains in the amorphous region are not fixed, a significant increase in strength and elastic modulus cannot be expected.

In addition, repeating the method of the present invention two or more times crystallizes the fixed extended molecular chains of the amorphous region and creates fibers with a more uniform structure without defects in the fiber direction. It is desirable because it can be obtained. In particular, by repeating the process five times, fibers with a strength of l5y-/d can be obtained.

Next, the method of the present invention will be explained in detail with reference to the accompanying drawings.

FIG. 2 is a schematic diagram of an example of an apparatus that can repeatedly perform heating and cooling used in the method of the present invention. In the figure, the spinning speed is 4.00.
Nylon 664 spun at 0 m/nli n or more
1fiM1 is fed into a heating and cooling device by a pair of rollers 8. This heating and cooling device has a pair of rollers 8, 8' at the inlet and outlet, respectively. roller 8.8
' has a sealed structure to prevent the atmosphere inside and outside the device from mixing with each other, as disclosed in Japanese Patent Publication No. 38-8395 or Japanese Patent Publication No. 40-2709, respectively, and Its function is to feed the nylon 66 fibers into the heating/cooling device or take them out. Nylon 66 $J1. is fed into the heating and cooling device by such a roller 8. The fibers are controlled at an appropriate temperature within the temperature range of Tm1 to Tm5 by the Calo-thermal zone 9.
It is heated in an atmosphere of ql and then immediately passes through a cooling zone io whose temperature is adjusted to below the glass transition point of the fiber.

Next, the heated and cooled nylon 66 fibers are sent to the next heating and cooling zone by the delivery roller 11. By appropriately varying the surface speeds of rollers 8 and 110, the tension applied to the nylon 66 fibers undergoing treatment in heating zone 9 and cooling zone 10 is adjusted. This heating and cooling operation can be repeated once or several times,
After all repeated heating and cooling treatments, nylon 66
The fibers are sent out of the device by rollers 8' and wound up by winder 12. This heating and cooling device is covered with a shield cover 13, and the interior of the shield carper 13 is evacuated by a vacuum pump through an exhaust port 14, or an inert gas such as nitrogen or helium is supplied through the exhaust port 14. It is fed to prevent oxidative decomposition during heating and cooling treatment of nylon 66 fibers.

The heating and cooling devices shown in 9.10 below may be of a type in which the fibers come into contact with the heating and cooling surfaces, respectively, or may be of a type in which the fibers do not come into contact with the heating and cooling surfaces, respectively.

In addition, heating media include infrared rays, high frequencies, laser beams,
Electric heaters are used, and cooling media include air cooling, water cooling, Freon gas, and electronic cooling elements.

Note that the apparatus used is not limited to the apparatus shown in FIG. 2, as long as the processing according to the method of the present invention that satisfies the above-mentioned requirements can be achieved.

Physical property values characterizing the fiber obtained by the method of the present invention are measured as follows.

[Positive mechanical loss”-! 5: (tlIIIδ) and dynamic elastic modulus (E') 3 To measure the mechanical loss tangent (tUδ) and dynamic elastic modulus (E'), a Rh@o-Vi bron manufactured by Toyo Baldwin was used. )DDV
-11c type is used. The -δ temperature (T) characteristic and the EJ degree (T) Ql characteristic are measured in dry air at a measurement frequency of 110 Hz and a temperature increase rate of 10° C./mln. -δ - From the temperature curve -δ peak height -δ) r11a and -δ peak temperature Tm
ax). In addition, before measurement, the sample is conditioned in an atmosphere with a relative humidity of 0 or more for 48 hours.

[Average refractive index f17+n and average refractive index distribution] Average refractive index and local average refractive index distribution observed from the side of the fiber using interference fringes obtained using an Interfaco fissure interference microscope manufactured by Carl Zeiss Jena, East Germany. can be measured.

All measurements described here are performed using green light (wavelength λ = 54
9 mμ) was used. The dip liquid was made by mixing olive oil and alpha-bromonaphthalene.

The average refractive index n7 is the average refractive index for polarized light with an electric field vector parallel to the fiber axis. From the obtained interference fringes, the optical path difference F is expressed as r=5λ=(n7−N)t. Here, d is the deviation of the interference fringes due to the fibers, D is the aperture of the parallel interference fringes, λ is the wavelength of the light beam used (549 mμ), N is the refractive index of the fiber encapsulant, and t is the thickness. Let R be the radius of the fiber, and let X be the coordinate along the direction perpendicular to the fiber axis direction when the center of the fiber is O, then the center of the fiber (X=O
) to the outer periphery (X=R), the local average refractive index distribution at each position can be determined from the optical path difference at each position. The refractive index at the center of the fiber (X=0) is the average refractive index n, □. Also, the average refractive index n□ is perpendicular to the fiber axis! With the average refractive index for polarized light with field vector'
"1f01 is the average refractive index at X=O"/fi
It can be found in the same way as l. Note that the birefringence Δ"to+ at X=0 is "/Q. −”J−fO).

[Strong elongation, initial modulus]

Manufactured by Toyo Baldwin, TENSILONUTMn-
Using a 20-type tensile tester, under conditions of 9.20°C, 60% R, H, (relative humidity), initial length 2 Crn, tensile speed 100.
Measured at m5/min.

(DSC melting curve) Using a DSC-1b model manufactured by P@rk1n-E1mer, a sample amount of 1.5 [drops] was melted in an N2 gas atmosphere for about 18
The temperature is raised from 0°C at a rate of 20°C/min, and the melting curve is measured. the temperature at which its melting curve departs from the baseline,
That is, the melting start temperature is Tm1, the peak temperature of the melting curve is Tm2, and the temperature at which the melting curve returns to the baseline (the temperature at which the melting of the fiber is completed) is Tm3. Figure 3 shows a typical SC melting curve of nylon 66 fiber, in which 16 is Tm1.17 is Tm2.18 is Tm
3.19 is the baseline.

[Example 1] Nylon 66 with a relative viscosity (VR) of 35 (25°C, solvent concentrated sulfuric acid) was melt-spun at 295°C through a spinneret with a pore diameter of 0.23 wn and a number of holes of 13, cooled 7, and oiled. gives focusing properties, and various take-up speeds (4000, 5500,
Nylon 66 fibers taken at 6000 and 7000 m/m1n) were subjected to the heating and cooling treatment of the present invention. That is, the heat treatment zone length is 1 mm, the treatment temperature is 260° C., and the treatment speed is 4 wimin.

Load 2.0()/d), cooling rate 60°C/see,
By performing the heating and quenching treatment of the method of the present invention once under each condition of a cooling temperature of 30 eC) and a vacuum state, the sample genus 3°4
．． 5.6 (all examples of the present invention) were obtained.

Samples/f61 and A2 (both comparative examples) were obtained by subjecting fibers obtained by spinning in the same manner as above, except that the spinning speed was changed to 500 and 2000 m/min, and then subjecting them to the same heating and quenching treatment as above. I got it.

For the above sample (theory δ) ma engineering, T□3 engineering (℃).

"/10) '"uol'Δn2 intensity (y/d),
Mechanical loss at room temperature (25°C), elastic modulus E' (dy
Table 1 shows the results of measuring ne/certainty 2). In addition, untreated type (spinning speed 5500 m/m1r3) Group 7 and commercially available Asahi Kasei nylon 66 tire cord fiber (1260D/210f) were used.
) The results obtained by measuring A8 are also listed in Table 1 as a comparative example.

From Table 1, it can be seen that the strength and elastic modulus increase rapidly when the spinning speed is 4000 m/min or more. The heat treatment zone length is 1 darkness, the treatment temperature is 250
and 260℃, processing speed 4m/m1n1 load 2.0 (
IP-/d), cooling rate 60℃/Bee, cooling temperature 30
(°C), vacuum condition, and the sample was treated once under the following conditions: 3.
4 (all examples of the present invention) were obtained. For comparison, samples AI and 2 (both comparative examples) were obtained by processing under the same conditions except that the processing temperature was changed to 150 and 200°C. For these samples (-δ)m a x r Tm a
x (℃) r n /1 (II + n BO) +
Table 2 shows the numerical values of Δi1 strength U'/d) and mechanical loss modulus E' (dyne/sieve) at room temperature (25°C). ) &
5 and commercially available Asahi Kasei nylon 66 tire cord fiber ft1f:
(1260D/13f) The structure and physical properties of A6 are also listed in Table 2.

Note that Tm + and Tm2 + Tm3 of the untreated system are 230.3 and 260.3, respectively, and 269.8 (1:
).

From Table 2, it can be seen that when the treatment temperature exceeds Tm1 and is below Tm5, the values of strength and elastic modulus become significantly large.

[Example 3] Nylon 66 fibers (tension at break = 4.12!?/d) with a spinning speed of 5500 m1m1n used in Example 2 were heat-treated at one corner of the zone length, at a treatment temperature of 260°C, and at a treatment speed of 4/d. Load】5 and 3.0 (Vd), cooling rate 60℃/l
Sample A3.4 (an example of the present invention) was obtained by processing once under the following conditions: 1 ec, cooling temperature 30 (t)), and vacuum state. For comparison, load is 0.2, 0.4 and 4.1 (?/d)
Sample ml, 2.5 ml was treated under the same conditions except that
(all comparative examples) were obtained.

For these samples (side δ), T (°C).

maX maX ”/lel ' ”1101 'Δ”tco + intensity (
i! -/d) and the mechanical loss modulus E' (dyne/(-rn2) at room temperature (25°C) are shown in Table 3. 6 and commercially available Asahi Kasei nylon 66 tire cord fiber (1260D/13
f) The structure and physical properties of 應7 are also listed in Table 3.

From Table 3, the load applied to the thread is 0.5 C7/d) or more 4
0U'/d) or less, the strength and elastic modulus are significantly improved.

[Example 4] The drawn fiber sample used in Example 2 at a spinning speed of 5500 m/ml was heat-treated at a treatment temperature of 260° C. with a zone length of 1.
Processing speed 4 mm 7 mm, load 2.0 C9/d)
, cooling rate 60℃/8 ee % cooling temperature 40.30
and processed once under vacuum at 10°C to prepare samples &2.
, 3 and 4 (all examples of the present invention) were obtained. For comparison, sample AI (comparative example) was obtained by processing under the same conditions except that the cooling temperature was changed to 100°C. Table 4 shows the structures and physical properties of these samples. Still unprocessed system (spinning speed 55
00rn/min)? Table 4 also lists the structures and physical properties of Asahi Kasei Nylon 65 and commercially available Asahi Kasei Nylon 66 tire cord fiber (1260V13f) Flat 6.

The untreated system has a lath transition temperature Tg of 49 (1:)
It is.

Table 4 shows that the strength-elasticity modulus is high when the cooling temperature is below Tg (°C).

The following margin [Example 5] The taken fiber sample used in Example 2 at a spinning speed of 5500 m/ml was heated in a heat treatment zone at a treatment temperature of 260°C.
Processing speed 4 m/m1yr, load 2.0 (,P,ro)
, cooling rate 60℃/sec, cooling temperature 30 (℃
) and 1°2.3.4 and 5 times under vacuum conditions to obtain samples 1, 2, and 3°4.5 (all examples of the present invention).

Table 5 shows the structures and physical properties of these samples. Table 5 shows the structure and physical property values of the trench-untreated system (spinning speed 5500 m/mrR) A 6 and the commercially available chemical-free nylon 66@fiber (1260D/13f) High 7.

It can be seen from Table 5 that as the number of treatments increases, both the strength and elastic modulus increase.

The remaining 1"I [Example 6] Examples 1 and 2.3 except that only the atmosphere during heat treatment was changed to treatment under a vacuum condition, and N2 gas and ■Ie gas were used as an inert atmosphere. Table 6 shows the structure and physical property values of sample A3, which was processed under the same conditions as 4 and 5 and compared with sample shop 1 and notification 2.1 (both examples of the present invention) in air. .

Table 6 shows that under an inert atmosphere, it is possible to prevent oxidative decomposition of the yarn, and yarns with higher strength and higher elastic modulus can be obtained than when treated in air.

Margin below FIG. 1 is a schematic diagram of an example of an apparatus for spinning spun fibers.

In the figure, 1 is a yarn, 2 is a spinning head, 3 is a tubular heating area, 4 is a fluid suction device, and 5 is an oil application device.

In the figure, 1 is a yarn, 8 and 8' are feed rollers that also serve as shields, 9 is a heating zone, 10 is a cooling zone, 1t, 11', and 11' are delivery rollers with different rotation speeds, 12 is a winding machine, 13 is a shield cover, 14 is an inlet for inert gas or an exhaust port for creating a vacuum, and 15 is a wire, Tm1 * Tm2
*This is an explanatory diagram of Tm3. In the figure, 16 is Tm1
+17 indicates Trn2, *18 indicates Tm3, and 19 is the baseline.

Claims (1)

[Claims] 1. When heat-treating nylon 66 fibers spun at a spinning speed of 4000 m/min or more, (1) the tension applied to the fiber axis in the fiber axis direction is 0.5 tA or more and 0.99 T, P/d; Below (where d is denier, T
(2) In an atmosphere substantially free of oxygen, (1) the heat treatment temperature exceeds Tm1 of the DSC melting curve (the temperature at which the melting curve departs from the base line), and The fiber is heat-treated in a heating zone having a length t (+1111 ) in the axial direction of the fiber under conditions below the temperature at which melting is completed, and then immediately rapidly cooled in a cooling zone whose temperature is controlled to be below the glass transition point of the fiber. A method for producing high-strength, high-modulus nylon 66 fiber, characterized by carrying out the following steps. 2. The method for producing high-strength, high-modulus nylon 66 fibers according to claim 1, wherein the spinning speed is 5,500 m1 m1 n or more. 3. A method for producing a high-strength, high-SiP property nylon 66 fiber according to claim 1, wherein the quenching treatment is performed at a cooling rate of 10° C./8@e or more. 4. A method for producing a high-strength, high-modulus nylon 66 fiber according to claim 1 or 2, in which the spun yarn is heat-treated in a vacuum. 5. The method for producing high-strength, high-modulus nylon 66 fibers according to claim 1, wherein the spun yarn is heat-treated in a heating zone at a temperature range of Tm2 or higher and lower than Tm3, and then rapidly cooled at a cooling rate of 20°C Aec. . 6. A method for producing high-strength, high-modulus nylon 66 fibers according to any one of claims 1 to 5, wherein the spun fibers are subjected to heat treatment and quenching treatment two or more times.