JPS599209A - High-tenacity polyhexamethylene adipamide fiber - Google Patents

Abstract

PURPOSE:High-tenacity polyhexamethylene adipamide fibers, having a specific relative viscosity in formic acid, strength and tie molecular stability coefficient and a small change of strength in the vulcanization, and suitable for tire cords. CONSTITUTION:High-tenacity polyhexamethylene adipamide fibers having >=70, preferably 70-150, relative viscosity in formic acid, >=10g/denier strength, and <=0.20, preferably <=0.15, tie molecular stability, and consisting essentially of repeating units of the formula. Alternatively, 10wt% or less other amide-forming units may be added to the aimed fibers to modify the fibers. USE:Reinforcing tires with large amounts of yarns and numbers of lamination in construction vehicles, aircraft and trucks or buses.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides high tenacity polyhexamethylene adipamide fibers,
More specifically, the present invention relates to high-strength polyhexamethylene adipamide fibers having a strength of 10 f/d or more and having little change in strength during post-processing steps, particularly vulcanization steps.

Polyhexamethylene aji/armid fiber 1 Due to its excellent strength, toughness, heat resistance, dyeability, and color development, it is widely used as a fiber for industrial materials, interior bedding, and clothing. In particular, it has excellent strength, stiffness, heat resistance, fatigue resistance, adhesion to rubber, etc., and is therefore widely used as a fiber for tire cords.

In recent years, energy-saving technology has been required for tires as well, and tires with lower fuel consumption are being sought. To this end, tire manufacturers are pursuing tires that have low rolling resistance and are also lightweight.

Along with this, tire cords are also required to have high strength yarns with a high shimmodulus yarn arrangement. In particular, polyamide tire cords are mainly used for large tires with a large number of layers, such as for light trucks, truck passes, construction vehicles, and aviation, and as a result, there is a problem that the amount of yarn per tire is large. There is. ! R.N.
Reducing the number of woven fabrics and the number of woven fabrics not only reduces the weight of the tire, resulting in lower fuel consumption, but also improves fatigue resistance due to lower heat generation and increased heat dissipation, and improves separation safety due to improved adhesion. In order to contribute to improving productivity in the earring manufacturing process, polyamide diamond cords with higher strength are required. The fibers currently commercially available as polyamide fibers are 9.0 to 9.5 F.
It has an intensity of /d. Efforts have been made to improve this throughout history, but nothing satisfactory has yet been achieved.Generally, in order to obtain high-strength 4-lyamide fibers or preester fibers, polyamide or polyester with a high degree of polymerization is spun. , it is necessary to draw the obtained spun yarn at a high magnification. but,? Will it be discharged if the degree of polymerization of remer is increased? Since the melt viscosity of the remer increases, the degree of orientation of the obtained spun yarn increases and the drawability deteriorates. This tendency is particularly remarkable in polyhexamethylene adipamide, which has a significantly high crystallization rate.

In order to obtain a spun yarn with a low degree of orientation, there are methods such as decreasing the melting temperature, decreasing the spinning trough, decreasing the spinning speed, and increasing the amount of cooling air, but these methods are not sufficient. In order to completely improve this, there is a method of controlling the atmospheric temperature under the spinneret by providing a heating tube under the spinneret during melt spinning (Japanese Patent Publication No. 39-7,251, Japanese Patent Publication No. 43-8.985); A method in which a heating tube is provided under the spinneret to control not only the atmospheric temperature under the spinneret but also the cooling (% Kosho 4
No. 3-10,176, Special Publication No. 16.446 of 1983), etc. have been proposed. By using such a method, the degree of orientation of the spun yarn is reduced, making it possible to draw at a high magnification.
The strength of the obtained drawn yarn is improved.

In this way, the relative viscosity of the polyhexamethylene adipamide used can be increased from 50 to 60-70, and as a result, the strength of the resulting tire cord can be increased from 8 f/d to 9.0-95 f/d. I'm starting to be able to improve.

We further increased the degree of polymerization, carried out high-strength drawing, and studied to obtain a yarn with high strength, and as a result, we were able to obtain a yarn with a strength of 10 t/d or more. However, when we measured the strength of the threads taken from the rubber after passing through the twisting process, weaving process, adhesive heat treatment process, and vulcanization process using this raw yarn gold, we found that the conventional commercially available yarn was 9.5r/d. It was found that by using a polyhexamethylene adipamide tire cord and going through the above steps, the strength was comparable to that of the yarn taken from the rubber core (7 f/d). In particular, the decrease was remarkable during the vulcanization process, and it was found that the raw yarn did not exhibit any overall strength effect. As a result of extensive research into high-strength polyhexamethylene adipamide fibers that exhibit minimal strength loss during post-processing steps, particularly during the vulcanization step, the present inventors have improved the thermal stability of the elastic modulus of the resulting fibers. I discovered that it is important to encourage others.

In other words, the thermal stability of the fiber material (retention of elastic modulus during high-temperature treatment) is determined by the viscoelastic mechanical dispersion in the temperature range closely related to the micro-Brownian motion exhibited by the polymer chain segments existing inside the amorphous region. , (αa absorption) can be estimated from the warming of the storage modulus E' after (αa absorption). That is, the temperature after αa absorption is 15 in the case of polyhexamethylene azitsumid fiber.
The temperature gradient of the temple in the temperature range of 0°C or higher and 220°C or lower, that is, -d (pupil E') / dT (T = temperature) is 1
It shows stability of elastic modulus over thermal history in the range of 50°C to 220°C, reflecting irreversible microstructural changes in amorphous and crystalline regions. The present inventor found that the 1d(log E')/dTO value in the temperature range after αa absorption affects the strength retention rate for the vulcanization process, which has the greatest strength reduction even in the post-processing process of the tire cord, This has led to the present invention.

That is, the high strength hexamethylene adipamide fiber according to the present invention has the following requirements: 1) formic acid relative viscosity of 70 or more, 2) strength of 10 f/d or more, 3) tie molecular stability coefficient of 0.20 or less. Features.

The polyhexamethylene adipamide fiber referred to herein is mainly composed of repeating units of the following formula.

Polyhexamethyleneazino and mido fibers modified by adding other amide-forming units up to 10 times IkeIb can also be used in the method of the present invention. Such small amounts of amide-forming units include aliphatic dicarzene acids such as sepacic acid and dodecanoic acid; aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid; aliphatic diamines such as decamethylene diamine;
Aromatic diamines such as metaxylylene diamine; ω-amino acids such as 6-aminocaproic acid; lactams such as caprolactam and laurinlactam can be used. It is also possible to use a mixture of the above-mentioned polyhexamethylene adipamide and other types of polyamides such as polycabramide and polyhexamethylene cenamide in an amount of 20 weight or less.

Furthermore, the above-mentioned polyhexamethylene adipamide fibers contain additives commonly used for polyamides, such as heat stabilizers such as copper acetate, copper chloride, copper iodide, mercagotopenzimidazole, manganese lactate, and hypophosphorous. Light stabilizers such as manganese acid, phosphoric acid, phenylphos heptaonic acid, thickeners such as sodium pyrophosphate, titanium dioxide, silicon dioxide,
Matting agents such as kaolin, methylene bisstearylamide,
It may also contain lubricants and plasticizers such as calcium stearate.

The term "acid relative viscosity" here refers to the relative viscosity of a solution of 90% formic acid with a polymer concentration of 8.4'iL and a JK% solution at 25°C. Strong and thick yarn can be produced even if the relative viscosity of formic acid is less than 70, but it is necessary to draw it to a higher degree.
This is not preferable because the strength utilization rate in the post-processing step becomes low. When the relative viscosity of formic acid is increased, the melt viscosity of the discharged polymer increases, and as a result, the degree of orientation of the resulting spun yarn becomes thicker and the υ drawability deteriorates. This tendency is particularly remarkable in polyhexamethylene adipamide, which has a significantly high crystallization rate. Therefore, by increasing the melting temperature, υ by decreasing the spinning speed,
It is necessary to reduce the orientation of the spun yarn by attaching a heating tube or controlling the cooling conditions, and to draw it to a high degree. Even if the degree of orientation of the yarn is reduced, the degree of orientation is still high, and a high drawing ratio cannot be obtained, making it difficult to increase the strength.Formic acid relative viscosity is 150
This kind of phenomenon is seen when the viscosity exceeds 't-, but as the technology for relaxing the orientation of spun yarns progresses, spun yarns on the viscosity side can also be used, but the preferable relative viscosity of formic acid is 70 to 150, particularly preferably 70 to 100. It is.

The polyhexamethylene adipamide fiber in the present invention is 1
It is necessary to have an intensity of 0 f/d or more.

The strength of the currently commercially available 4-lihexamethyleneazinamide fiber kasto is around 9.5 f/d, so if you want to change the tire design, the number of laminated layers, and the number of woven fabrics, consider the safety factor. It is required to improve the strength by about 5% of the original yarn. Of course, even in yarns with a strength of 10 r/d or less, the strength utilization rate in the post-processing process can be improved by providing a tie molecular stability coefficient as shown in the present invention. , the effect is small compared to the improvement for yarns of oy7a and above.

In the present invention, the term "Tie molecular stability coefficient" refers to the temperature characteristics measured in dry air at a measurement frequency of 110 Hz and a heating rate of 3°C/min using a Vibron DDV-nc model manufactured by Toyo Baldwin. Then, this was copied onto semi-logarithmic graph paper, and 1d(loi+E')/dTfc was determined in the temperature range of 150° C. or higher and 220° C. or lower. The closer it is to the tie molecular stability coefficient iiO, the more desirable it is, but if it is 0.20 or less, a decrease in strength can be tolerated.

Preferably it is 0.15 or less.

In order to reduce the tie molecular stability coefficient, approaches from both the polymer side and the spinning/drawing side are required.All polymers with a formic acid relative viscosity of 70 or higher
Even if it is made by melt polymerization in the same way as the polymer for yarn below, and then spun, stretched, and heat-set to create a yarn with a strength of 10 t/d or more, the tie molecular stability coefficient is 0.20 or more. As a result, the strength decreases significantly in the post-processing process. This is because it is necessary to lengthen the melting time to obtain a polymer with a high degree of polymerization, and during this time, a portion of polyhexamethylene azinoamide, which is easily thermally decomposed, is thermally decomposed. This is thought to have caused the stability of the tie molecule to decrease. Therefore, the tie molecular safety redundancy coefficient is 0.
In order to obtain polyhexamethylene adipamide fibers with a high polymerization degree of 20 or less, a polymer melt-polymerized to a formic acid relative viscosity of 70 or less, preferably 1:60 or less is chipped and then heated at 180°C.
It is preferable to carry out solid phase polymerization at a temperature of ~240°C.

After concentrating a 5° aqueous solution of hexamethylene diammonium adipate to 70° in a concentration tank, it was heated to 17.5 K in the first reactor.
1. From 220°C to 250°C while maintaining the pressure of f/-.
Let the temperature rise for 5 hours. The temperature in the second reactor was then increased to 2
While raising the temperature to 80°C, the pressure was returned to normal pressure in 20 minutes. After separating the water vapor in a gas-liquid separation tank, it is passed through a three-way valve, and one end passes through a spinneret to form a rope, which is water-cooled and then cut to form chips (1).The other end is polymerized in a post-polymerization vessel at 350 wHf and 280°C for 15 minutes. Thereafter, it was passed through a spinneret to form a rope, cooled in water, and then cut to form a tep (If). After the melt polymerization process, the polymer was poured through sampling nozzles before and after the polymerization vessel, and the [C00H) and CNHv) end groups of the obtained polymer were measured and shown in FIG. 1 (curve B). Chip (1)
The relative viscosity of formic acid is 29.7, the (COOH) end group is 10
1.5 meq/h, [N)h] terminal group is 62
．． It was 5 meq/1!4. Chip (1) 5000
A portion of the polymer was polymerized in a tumbler-type solid phase polymerization vessel at a jacket temperature of 200° C. and a nitrogen flow rate of 31/hr/polymer. During solid phase polymerization, the ring nozzle changes over time.
The [C00H) terminal group and ['Nf(,] terminal group) of the obtained chip were measured and shown in Figure 1 (curve A).As seen in Figure 1, solid phase polymerization (curve In A), as the polymerization progresses, the [C0OH] terminal group and [NH1]
In contrast to the fact that the terminal groups are reduced by approximately equimolar amounts, the reduction of the [NHt] terminal groups is small in melt polymerization. This indicates that a reaction occurs in which both the (COOH) and (NHv) end groups decrease due to polycondensation, and the C NHt ) end group increases due to thermal decomposition of polyhexamethylene adipate.

1 (Refer to P123 of Polymer Symposium Abstracts 71'5A10)
It is necessary to use a polymer that is less susceptible to thermal decomposition when using polyhexamethylene azamide fibers with a low molecular stability coefficient. is the preferred method.

Japanese Patent Publication No. 48-32,616 is known as a method for producing high-strength polyhexamethylene azino and mido fibers. However, even if a polymer having a formic acid relative viscosity of 70 or more is directly spun and stretched by the method disclosed in Japanese Patent Publication No. 48-32,616, it is difficult to obtain a raw yarn with a low tie molecular stability coefficient. In order to obtain raw thread metal with a low molecular stability coefficient,
It is necessary to heat set at a high temperature to reduce the shrinkage rate of the yarn and stabilize its thermal structure. The acceptable shrinkage rate of yarn is 160
The shrinkage rate when allowed to freely shrink for 30 minutes in dry heat at ℃ is 7% or less, preferably ti4% or less. For 7 inches or more, even when using polymers that undergo in-phase polymerization and have low thermal decomposition,
If the tie molecular stability coefficient is 0.20 or more, the retention of stiffness in the post-processing process will be low.

Spinning methods for obtaining low-shrinkage yarn include a method in which the spun yarn is once wound as an undrawn yarn and then drawn and heat-set, and a method in which the spun yarn is directly drawn and heat-set. In the production of raw yarn with a high relative viscosity of formic acid, the shrinkage rate becomes high, so high temperature heat setting, for example, high temperature heat setting of 220° C. or higher is required, and the relaxation rate also needs to be high.

Although the raw yarn of the present invention obtained by the method described above has a high yarn strength of 10 f/d or more, it can be used in a twisting process, a weaving process, an adhesive heat treatment process, and a vulcanization process. There is little decrease in strength when passing through. Therefore, it is useful for reinforcing products that require strength such as tire cords and belts. It is particularly useful for reinforcing tires for construction vehicles, aircraft, and trucks and buses, which require a large amount of yarn and a large number of layers.

Next, the method of the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples.

In the examples, the relative viscosity of formic acid is the relative viscosity at 25° C. of a solution in which a polymer is dissolved in 90% formic acid so that the polymer concentration is 8.4% by weight. Amino terminal group means 90% by weight
6.0 ft- of polymer in 50 ml of phenol aqueous solution
This is the value obtained by dissolving the solution and subjecting it to potential titration with 1/20 N hydrochloric acid to determine the neutralization point. The carboxylic acid terminal group is the deprivation value determined by heating and dissolving the polymer 4 of Of'i in benzyl alcohol 50, followed by neutralization titration with 1/1 ON sodium hydroxide using a phenolphthalein indicator. The strength elongation was determined using Autograph S-100' manufactured by Takasugi Seisakusho (using f-, 80 times/m
The value was determined using a raw yarn length of 25 cm with a twist of 25 cm, a falling speed of 30 f/min, a chart speed of 60 cm/7 min, and a full scale of 25 to 9. Dry heat shrinkage rate is 80 times/
This is the value obtained by freely shrinking a 1.0 m raw yarn in an air oven at -160° C. for 30 minutes in a twisted tube of 1.0 m. The tie molecular stability coefficient is Vibro manufactured by Toyo Baldwin Co., Ltd.
Using a DDV-11C model, measure the temperature characteristics in dry air at a measurement frequency of 110 Hz and a heating rate of 3°C/min.
This is the value of -d(E')/dT at 20°C.

Example: A 50% aqueous solution f of hexamethylene diammonium adipate was quantitatively fed at a rate of 2,000 parts/hour, and after being concentrated to 70% in a concentration tank, a pressure of 17.5 Kf/- was maintained in the first reactor. The temperature was raised from 220°C to 250'C in 1.5 hours. Then in the second reactor the temperature 'f: 280°C
The pressure was returned to normal pressure in 20 minutes while increasing the temperature to . In the gas-liquid separation tank, water vapor was passed through a separation layer spinneret to form a rope, which was cooled with water and cut into chips.

The formic acid relative viscosity of the chip was 29.7, (COOH:) terminal group 1 to 101.5 meq/Kf, CNHt) terminal group 62-5 meq/Ky. The chip 5.000
A portion of the polymer was polymerized in a tumbler-type homopolymerizer at a jacket temperature of 210° C. and a nitrogen flow rate of 3 t/hour/polymer smell.

After 7 hours and 15 minutes, it was cooled and discharged. Formic acid relative viscosity 90.
0, (COOH) terminal group 6 Z 7 meq/Kp, [
A chip with 23,0 meq/14 terminal groups (NHt) was obtained. The tip was spun from a spinneret having 312 holes of 0.27 wmφ at 303°C, passed through a 150mm heating cylinder heated to 350°C, cooled, and coated with a spinning oil. Adopted by Nelson Roller,
Continue to rotate at a higher circumferential speed in sequence @ 2nd to 4th nelson-ra, and stretch in 3 stages) 1-
It was wound up at a speed of 1.500 m/min. Assuming that each of the four stages of godet roll sets is G, ~ G4, the temperature of each roll is G: 80°C.

G: 210℃, G: 230℃, G4: 250
℃. The circumferential speed ratio of each roll is Gm/G+=3.6
3, Gm/Gy=1.67, G4/Gl=
0.995.

and winding speed/G4=0.890. The yarn obtained was 1890 d/312 f and had a formic acid relative viscosity of 83.0. Strength IQ, 4 f/d, elongation 21.
0chi.

Dry heat shrinkage rate 2.00. The tie molecular stability coefficient was 009.

The yarn was twisted at 32.0x310T/10cM, and
．． Using a Ritzler convenience store treater with 890 d/2 raw cord, the temperature in the first zone was 160°C.
, tension λOKy/cord, time 140 seconds, second zone temperature 230°C, tension 3.8 Kf/cord, time 40 seconds, third zone temperature 230°C, tension 2.6 Kf/cord, time 40 seconds.・Diragu treatment was performed using formalin latex liquid.

The amount of derag liquid attached is 4.5 inches.

The degging cord is buried in carcass rubber and heated to a temperature of 19
After vulcanization at 0°C for 30 minutes under free shrinkage, the vulcanized rubber was broken, the vulcanized cord was taken out, and its strength was measured.7.
The strength retention rate of the 9f/dc vulcanized cord was 76.0 cm).

Comparative Example 1 A 50% aqueous solution of hexamethylene diammonium adipate was quantitatively supplied at a rate of 2.000 parts/hour, and 7
After concentrating to 0%, 17.5Kg in the first reactor.

1. From 220°C to 250°C while maintaining the pressure of , /J.
The temperature was raised in 5 hours. The temperature in the second reactor was then increased to 2
While raising the temperature to 80°C, the pressure was returned to normal pressure in 20 minutes. After separating water vapor in a gas-liquid separation tank, 200 mHf in a post-polymerization vessel,
The mixture was stored at 280° C. for 15 minutes, passed through a spinneret to form a rope, cooled with water, and cut into chips. Formic acid relative viscosity of the chip tJ: 78.7, [α)011) terminal group is 58.6
me(lA, [NHtl end group is 33.4 meq/
I met Kf.

Using this chip, a hole 312 of 0.27 wφ was formed at 298°C.
The spinneret is spun from a spinneret with a diameter of 150 mm, heated to 310°C, passed through a 150 mm heating cylinder, cooled, and coated with spinning oil. It is guided to the rotating second to fourth Nelson rollers, and subjected to stretching heat setting in three stages.
, 500 m/min. , the temperature of each roll is 80°C in G, at: zio°Cv, G3: 230°C.

G4: 230°C, and the peripheral speed ratio of each roll is Gt
/Gt = 3.53, Gs /Gt = 1.67
, 0a/Gs = 0.9952 winding speed/G4 = 0.
It was 890. The obtained yarn had a formic acid relative viscosity of 74.
0, strength lQ, 3 f/d, elongation 21.5%, dry heat shrinkage rate 27 inches, and tie molecular stability coefficient 0.21.

The raw yarn was made into raw cord and dirag cord in the same manner as in Example 1, and then vulcanized, and the vulcanized cord was taken out and its strength was measured.7. SM'/d (vulcanized cord strength retention rate 69
．． Comparative Example 2 A 50% aqueous solution of hexamethylene diammonium adipate was quantitatively supplied at a rate of 2.000 parts/hour, and 7% was
17.5 Kg/c in the first reactor after 0tlbK concentration
1.5 from 220℃ to 250℃ while maintaining the pressure of r&
The temperature was raised over time. Then in the second reactor warm Mt28
While raising the temperature to 0°C, the pressure was returned to normal pressure in 20 minutes. After separating water vapor in a gas-liquid separation tank, 350wIIHJ' in a polymerization vessel
After polymerization at 280° C. for 15 minutes, it was passed through a spinneret to form a rope, cooled in water, and then cut to form chips. The formic acid relative viscosity of the chip is 67.0, [C00HJ end group is 65.9 me
q, /Kg, [NHt] terminal group is 34,1 meq /
It was a smell. Spun Li gold having 312 holes of 0.27 mm diameter was spun at 298°C using the spinneret, immediately cooled, applied with a spinning oil, taken up immediately by the first Nelson roller, and successively spun at higher circumferential speeds. The film was introduced into rotating second to fourth Nelson rollers, subjected to stretching heat setting in three stages, and wound up at a speed of 1.900 m/min.

Assuming that there are four stages of godet roll assemblies G, ~G4, the temperature i of each roll is G1: room temperature + G1 near 0°C.

G: 215℃, G4: 215℃, peripheral speed ratio of each roll is Gt /G1= 1-05, Gs /Gt=
3.24.

G4/Gl = 1.6s, winding speed/G4 =
It was 0.91. The obtained yarn has a formic acid relative viscosity of 62,
0, strength 9.4t/d, elongation 20.8%, dry heat shrinkage rate 3.5%, and tie molecular stability coefficient 0.15.

The raw yarn was made into raw cord and dirag cord in the same manner as in Example 1, and then vulcanized, and the vulcanized cord was taken out and its strength was measured.7. OF/d (vulcanized cord strength retention rate 74.5
%)Met.

Example 2 Low viscosity chips obtained in Example 1 (formic acid relative viscosity 29.
7), solid phase polymerization was carried out for 6 hours and 30 minutes in the same manner as in Example 1.
A chip with a formic acid relative viscosity of 79.0 was obtained. Spinning and drawing heat setting was performed in the same manner as in Comparative Example 1 using the tip tube. The obtained yarn has a formic acid relative viscosity of 74.1 and a strength of 1o.
-af/d, elongation 21.7%.

The dry heat shrinkage rate was 2.6%, and the tie molecular stability coefficient was 0.13. The raw yarn was made into raw cord and dirag cord in the same manner as in Example 1, and then vulcanized.The vulcanized cord was taken out and its stiffness was completely measured.
．． 8).

Example 3 Low viscosity chips obtained in Example 1 (formic acid relative viscosity 29.
7), solid phase polymerization was carried out in the same manner as in Example 1 for 6 hours at 50°C.
A chip with a formic acid relative viscosity of 83.6 was obtained. The chips were spun from a spinneret with 312 holes of 0.24 mφ at 298°C, and
After passing through a heating tube of 0.0 cm to cool it and applying a spinning oil,
Immediately, it is taken up by the first Nelson roller, and then guided to the second to fourth Nelson rollers, which rotate at higher circumferential speeds, and subjected to stretching heat setting in 3 stages for 1.8 minutes.
It was wound up at a speed of 00 m/min. If each godet roll set in 4 stages is t''Gt~G, then the temperature of each roll is Gl280℃lG:210℃G=230℃=Ga:23
0℃, peripheral speed ratio of each roll, Gy /Gl = 3
．． 50, Gm/Gt = 1.70.

G4 /Gm = 0.995, winding speed /G4 = 0
．． It was 890. The obtained yarn has a formic acid relative viscosity of 784
, strength 10. ! M/d, elongation 2α6chi, dry heat shrinkage rate z5
The molecular stability coefficient was 0.12.

The raw yarn was made into a raw cord and a dip cord in the same manner as in Example 1, and then vulcanized, the vulcanized cord was taken out, and its strength If
Measured location7. c+r/a (vulcanized cord strength retention rate 75
．． 2φ).

Example 4 Using the chip obtained in Comparative Example 2 (@acid relative viscosity 67.0), same phase polymerization was carried out in the same manner as in Example 1 for 4 hours and 30 minutes to obtain a chip having a formic acid relative viscosity of 85.7.

Using this chip, spinning and stretching were carried out in the same manner as in Example 3. The obtained yarn has a formic acid relative viscosity of 80.2, a strength of 10.51/d, an elongation of 20.5 inches, and a dry heat shrinkage rate of 2.6%.
, the tie molecular stability coefficient was 0.15.

The raw yarn was made into a raw cord and a dip cord in the same manner as in Example 1, and then vulcanized.The vulcanized cord was completely destroyed, and its strength was measured. Rate 72.
4%).

Comparative Example 3 Solid-phase polymerized chip obtained in Example 4 (@acid relative viscosity 85
．． 7) Spun from a spinneret with 312 holes of 0.27 amφ at 298°C using 'IIc, passed through a 200m+ heating cylinder heated to 320°C, cooled, applied spinning oil, and then immediately 1 Pick up at Nelson Roller,
Subsequently, the film was introduced into the second to fourth Nelson rollers rotating at higher circumferential speeds, subjected to stretching heat ceratra in three stages, and wound up at a speed of 1,800 m7. Assuming that each godet roll set in 4 stages is tG, -G4, the temperature of each roll is G.

: Room temperature + Gt near o℃lGs: 215℃, G4:2
The temperature was 15℃, and the circumferential speed ratio of each roll was G2/CI=1.0.
5, Gs/G4=3.43, G4/Ga=1
-65.

Winding speed/G4=0.91. The obtained yarn had a formic acid relative viscosity of 80.2, a strength of 10.5 f/d, and an elongation of 18.
9%, dry heat shrinkage rate 4.7%, tie molecular stability coefficient 0.2
It was 1.

The raw yarn was made into a raw cord and a dip cord in the same manner as in Example 1, and then vulcanized, and the vulcanized cord was taken out and its strength was measured: 71 r/d (vulcanized cord strength retention rate: 67.6 inches) Met.

As shown above in Examples and Comparative Examples, formic acid relative viscosity is 70
As mentioned above, raw yarn with a strength of 10 f/d or more is
Direct spinning and drawing by the method disclosed in Japanese Patent No. 2,616 does not yield a raw yarn with a low tie molecule stability coefficient. Combined with the reduction in the shrinkage rate of the yarn due to high-temperature heat setting and the improvement of the degree of decomposition-inhibiting polymerization through the use of in-phase polymerization, a yarn with a low tie molecular stability coefficient was obtained. , a cord with high strength utilization even after post-processing steps such as a twisting step, a dilag treatment step, and a vulcanization step, that is, a cord with high strength after vulcanization can be obtained. By using the raw yarn of the present invention, it is possible to reduce the number of layers laminated in tires and belts, and to reduce the number of tires and belts.

Figure 1 50 60 70 80 90
100 110 (COOH) (meqj/kg) Figure 2 m-) Temperature (0C)

Claims (1)

[Claims] 1. A high-strength polyhexamethylene adipamide fiber having the following requirements: 1) a formic acid relative viscosity of 70 or more, 2) a strength of 10 f/d or more, and 3) a tie molecular stability coefficient of 0.20 or less. . 2. The polyhexamethylene adipamide fiber according to claim 1, which has a tie molecular stability coefficient of 0.15 or less.