JPH0541724B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a polyamide fiber having high strength, excellent modulus, dimensional stability and heat resistance suitable for industrial material use, and a method for producing the same. (Prior Art) Polyamide fibers such as polycapramide and polyhexamethylene adipamide fibers have high strength, toughness, and durability, and have traditionally been used in various industrial applications such as tire cords, V-belts, and conveyor belts. It has been widely used in fishing nets, ropes, etc. However, the above-mentioned polyamide fibers have a low modulus and poor dimensional stability at high temperatures, so their use as tire cords is currently limited to bias tires. Therefore, with the aim of imparting a level of modulus and dimensional stability that can be applied to radial tires, which are the mainstream tire structure, to the polyamide fibers mentioned above,
Conventionally, various modifications of polyamide fibers have been studied. On the other hand, in recent years, polytetramethylene adipamide has become known as a new material with high crystallinity (for example, JP-A No. 56-149429, JP-A No. 56-149430, and JP-A No. 56-149431). If utilized, it is expected that high modulus and low shrinkage fibers can be obtained, but polytetramethylene adipamide has a high melting point of 290°C or higher, and cannot be stably produced by melt spinning. In particular, it has been said that it is difficult to obtain highly strong fibers. (Problems to be Solved by the Present Invention) The present inventors have conducted extensive studies with the aim of developing high-strength polyamide spinning that retains the characteristics of polyamide fibers and has significantly improved modulus and dimensional stability. As a result, it was discovered that a new polyamide fiber that met the above purpose could be obtained by spinning copolyamide containing polytetramethylene adipamide polymer as a main component under specific conditions, and the manufacturing conditions were also improved. This led to the establishment of the present invention. (Means for Solving the Problems) That is, the present invention comprises 98 to 85 mol% of tetramethyleneadipamide units and 2 to 85 mol% of other amide-forming units.
A copolyamide fiber consisting of 15 mol%, characterized in that it simultaneously has the following properties, and (1) 98 to 85 mol% of tetramethylene adipamide units and 2 to 85 mol% of other amide-forming units.
A copolyamide consisting of 15 mol% and having a sulfuric acid relative viscosity of 3.0 or more, 290
melting at a temperature of ~320°C and spinning through a spinneret; (2) directly under the spinneret a length of 5~100 mm;
cm, attaching a heating cylinder whose atmospheric temperature is controlled at 200 to 400°C, and passing the spun yarn through the heating cylinder atmosphere to delay cooling of the yarn; (3) after passing through the high temperature atmosphere; quenching the yarn of and
(4) 6.0 times or less after taking the yarn,
The present invention also provides a method for producing polyamide fibers having the following characteristics, characterized in that each step consisting of drawing at a draw ratio of 90% or more of the limit draw ratio is carried out in sequence. (a) Strength T/D≧8g/d (b) Elongation E≦20% (c) Initial modulus Mi≧30g/d (d) Boiling water shrinkage rate △Sw≦5% (e) Melting point Tm=275~ 288°C The copolyamide used in the present invention is a copolymer consisting of 98 to 85 mol% of tetramethylene adipamide units and 2 to 15 mol% of other amide-forming units, and 95 to 90 mol% and 5 to 5 mol% of other amide-forming units, respectively. A copolymerization range of 10 mol% is preferred. Here, if the tetramethylene adipamide unit exceeds 98 mol%, the effect of the present invention due to copolymerization cannot be obtained;
If the amount is less than mol%, the crystallinity will be significantly reduced, and the excellent characteristics inherent to the polytetramethylene adipamide polymer, such as modulus and dimensional stability, will be lost, which is not preferable. Other amide-forming units that can be copolymerized with the tetramethylene adipamide unit include, for example, capramide,
Hexamethylene adipamide, hexamethylene sebamide, hexamethylene terephthalamide, hexamethylene isophthalamide, undecamethylene terephthalamide, undecamide, metaphenylene isophthalamide, paraphenylene terephthalamide and metaxylylene Examples include adipamide, among which capramide units are most preferred from the viewpoint of copolymer production and the properties of the resulting fibers. The copolyamide has a low melting point of 275°C to 28°C, and thermal decomposition foaming occurs only at a temperature of 325°C or higher, so its thermal stability is the same as that of the homopolymer. Therefore, by using the above-mentioned copolyamide, the spinning temperature range can be expanded and a lower spinning temperature can be used. In addition, in order to obtain the desired high-strength fiber, the copolyamide used in the present invention must have a high degree of polymerization, with a relative sulfuric acid viscosity of 3.0 or more, preferably 3.5 or more, as measured in a 1% solution of 98% sulfuric acid at 25°C. is necessary. Next, the method for producing the polyamide fiber of the present invention will be explained. In the method of the present invention, the above-mentioned copolymer is first melted at a spinning temperature of 290 to 325°C, particularly 295 to 320°C, and then passed through a normal spinning pack and spun through a spinneret hole, directly below the spinneret. has a length of 5~
A cylindrical heating cylinder of 100 cm, preferably 10 to 50 cm is attached, and the yarn is guided into the atmosphere of the heating cylinder heated to 200 to 400°C, preferably 250 to 360°C, to delay cooling of the spun yarn. It is necessary. Next, cold air is blown onto the yarn that has come out of the heating cylinder to rapidly cool it down. If the yarn spun from the spinneret hole does not pass through the atmosphere inside the heating cylinder and is rapidly cooled directly under the spinneret, stable spinning cannot be carried out, and the undrawn yarn that is drawn has a low strength/elongation product. Therefore, even if the yarn is drawn subsequently, it is not possible to draw at a high magnification, and a high-strength yarn cannot be obtained, which is not preferable. In the heating atmosphere conditions directly below the spinneret in the method of the present invention, if the length of the heating cylinder and the lower limit of the atmosphere temperature are less than 5 cm or less than 200°C, respectively, there is no effect of sufficiently heating the yarn; Exceeding 100 cm or 400°C is not necessary in terms of the effect of heating the yarn, and is rather undesirable because it causes thermal oxidative deterioration of the spun yarn. The appropriate condition for rapidly cooling the yarn that has passed through the heating tube with cold air is usually to blow cold air at a temperature of 10 to 50° C. at a flow rate of 1 to 5 Nm ³ /min. The cooled and solidified yarn is coated with an oil and then taken off by a take-up roll that rotates at a predetermined speed. In this case, the take-up speed can be arbitrarily selected from the range of 300 to 3000 m/min, and the discharge rate can also be arbitrarily selected from the range of 1 to 3 g/min. Next, the drawn yarn is once wound up with a winder, or it is continuously subjected to a drawing process. For example, in the case of the direct spinning drawing method, the drawn yarn is drawn to a total drawing ratio of 6.0 times or less depending on its degree of orientation.
In order to obtain the high-strength fiber of the present invention, it is preferable to carry out the stretching at a stretching ratio of 90% or more, usually 92 to 96%, of the limit stretching ratio, and to divide the stretching into two or more stages. Note that the limit stretching ratio here means the highest stretching ratio that allows stretching for at least 5 minutes or more. After the yarn has been drawn, it is heat-set in a relaxed or tensioned state and then wound up with a winder. Thus, the polyamide fiber obtained by the method of the present invention has excellent novel properties as described above, but in particular, compared to conventional polyamide fibers such as polycapramide and polyhexamethylene adipamide fibers, it has a high melting point of about 15°C or more, Moreover, it is significantly different in that it exhibits a low boiling water shrinkage rate. Furthermore, since the polyamide fiber of the present invention has a high melting point, there is little change in properties when heated to high temperatures, such as low shrinkage when exposed to high temperature air, modulus at high temperatures, and strength retention. It exhibits excellent properties such as good hardness and low creep. The polyamide fiber of the present invention is a high-strength yarn with a strength of 8 g/d or more, usually 9 g/d or more, and since it is produced by drawing at a high magnification, the elongation is 20% or less. The copolyamide of the present invention has good crystallinity and therefore has excellent heat fixability, so it can be heat fixed with the molecular chains in a highly oriented state during stretching, and fibers with high strength, high modulus, and low elongation can be obtained. It is. The above characteristics of the polyamide fiber of the present invention are based on the following definitions and measurement methods. (a) Strength T/D (b) Elongation E (c) Initial modulus (synonymous with initial tensile resistance)
Mi: Based on the method of JIS L-1017. sample
After being left in a temperature-humidity controlled room at 20℃ and 65%RH for more than 24 hours, it was measured using a "Tensilon" UTM-4L tensile tester (manufactured by Toyo Baldwin Co., Ltd.) at a test length of 25cm and a tensile speed of 30cm/min. And load -
The elongation rate curve was determined. From this load-elongation rate curve, T/D, E, and Mi were determined according to the definitions of JIS L-1017. (d) Boiling water shrinkage rate △Sw: The sample was taken in a skein shape, left in a temperature and humidity controlled room at 20℃ and 65% RH for more than 24 hours, and then measured by applying a load equivalent to 0.1 g/d of the sample. A sample of length l ₀ is
After being treated in boiling water for 30 minutes without tension,
The fibers were air-dried for 4 hours in the temperature and humidity control room, and then the load was applied again, and the measured yarn length _l1 was calculated using the following formula. △Sw=(l ₀ −l ₁ )/l ₀ ×100(%) (e) Melting point Tm: PerkinElmer DSC-2
Using a type differential scanning calorimeter, in a nitrogen stream, 10
In the DSC curve measured at a heating rate of °C/min, the peak temperature of the melting curve was defined as Tm (°C). Next, the present invention will be explained in detail with reference to the following examples. Example 1 Polyamide (nylon 4.6/6) containing tetramethylene adipamide as the main component and copolymerizing capramide as a copolymerization component at the ratio shown in Table 1.
A material containing 0.03% by weight of cuprous iodide and 0.1% by weight of potassium iodide as a heat stabilizer was subjected to the following melt spinning. An extruder-type spinning machine with a diameter of 30 mmφ and a nozzle with a hole diameter of 0.3 mmφ and 34 holes was used, and the spinning temperature (polymer temperature) was varied as shown in Table 1 depending on the copolymerization composition of the polymer. A heating tube with an inner diameter of 20 mmφ and a length of 50 cm was attached directly below the cap, and the ambient temperature at a position 225 cm from the top of the heating tube and 1 cm from the outermost thread was set at 350°C. After the spun yarn passes through the heating cylinder, it is placed under the heating cylinder.
The yarn was cooled by blowing cold air at 20°C over a distance of 1 m. The wind speed was 30 m/min and the flow rate was about ³ Nm3. The cooled and solidified yarn is coated with a lubricant using an oil supply roll, then taken up by a take-up roll at 60°C that rotates at a surface speed of 400 m/min, and then continuously
After performing stage stretching, it was rolled up. The stretching roll temperature was 200°C for the first stretching roll, 250°C for the second stretching roll, and no heating for the tension adjustment roll.The stretching ratio was 4.0 times in the second stage, and the remainder was stretched in the second stage. , it was rolled up with 5% relaxation. The total stretching ratio was 95% of the limit stretching ratio. The obtained drawn yarn was doubled to give a denier of 1260, and the results of evaluation of its physical properties are also shown in Table 1.

【table】

[Table] As is clear from Table 1, the fibers (No. 2 to 4) obtained from the copolymer of the present invention are a homopolymer (No. 1) and a polymer with a high copolymerization ratio of other components (No. 5). It has a good balance of strength, modulus, and dimensional stability compared to . Example 2 The copolyamide of Test No. 3 shown in Example 1 (95 mol% of tetramethyleneadipamide units/5 mol% of capramide units) was used, and the spinning conditions were changed to the second
Spinning and drawing was carried out with various modifications as shown in the table. The properties of the obtained drawn yarn are also shown in Table 2.

[Table] As is clear from Table 2, when the spinning conditions are outside the range specified in the present invention (Nos. 8 to 13),
It is not possible to obtain polyamide fibers with a desired balance of properties. (Effects of the Invention) As explained above, the new polyamide fiber of the present invention has excellent balance of strength, modulus, dimensional stability, and heat resistance, and is particularly suitable for use in rubber reinforcing materials such as tire cords and belts, and other materials. Useful as an industrial material.

Claims (1)

[Claims] 1. 98 to 85 mol% of tetramethylene adipamide units
A copolyamide fiber comprising 2 to 15 mol% of other amide-forming units and having the following properties at the same time. (a) Strength T/D≧8g/d (b) Elongation E≦20% (c) Initial modulus Mi≧30g/d (d) Boiling water shrinkage rate △Sw≦5% (e) Melting point Tm=275~ 288°C 2 (1) 98-85 mol% of tetramethyleneadipamide units and 2-15 mol% of other amide-forming units
A copolyamide consisting of a copolyamide with a sulfuric acid relative viscosity of 3.0 or more,
Melting it at a temperature of 320°C and spinning it through a spinneret; (2) attaching a heating cylinder with a length of 5 to 100 cm and an atmospheric temperature controlled at 200 to 400°C directly below the spinneret, and spinning the spun yarn through a spinneret; (3) rapidly cooling the yarn after passing through the high-temperature atmosphere; and (4) after taking the yarn, the yarn is heated by 6.0 times. A method for producing a polyamide fiber having the following characteristics, characterized by sequentially performing the steps of stretching at a stretching ratio of 90% or more of the limit stretching ratio. (a) Strength T/D≧8g/d (b) Elongation E≦20% (c) Initial modulus Mi≧30g/d (d) Boiling water shrinkage rate △Sw≦5% (e) Melting point Tm=275~ 288℃