JPH03137217A - High tenacity polyester fiber - Google Patents

Abstract

PURPOSE:To provide the subject fiber composed of polyethylene terephthalate, having a specific fiber structure parameter, high strength and modulus and excellent thermal dimensional stability and useful as rubber-reinforcing material such as tire cord or transmission belt or fishing net, sewing thread, tent, etc. CONSTITUTION:The objective fiber is composed essentially of a polyethylene terephthalate having an intrinsic viscosity [eta] of >=0.7 (preferably 0.8-1.2). The birefringence n of the fiber is >=190X10<-3> (preferably 190X10<-3> to 220X10<-3>), the crystal orientation degree fc is >=0.94 (preferably >=0.95), the amorphous region orientation degree fa is >=0.55 (preferable >=0.60), the absolute value (¦delta ns-c¦) of the difference between the birefringence ( ns) of the surface layer of each single filament and that of the core part ( nc) is <=3X10<-3> and the absolute value (¦deltaX(H)s-c¦) between the crystallinity parameter (X(H)s) of the surface layer of each single filament measured by laser Raman spectrometry and that of the core part (X(H)c) is <=2.0cm<-1>.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to polyester fibers, and more particularly, to polyester fibers with high strength, high elastic modulus, and excellent thermal dimensional stability suitable for industrial material applications. It is something.

<Prior Art> Polyester fibers have the characteristics of high strength and high modulus of elasticity, and are therefore widely useful in various industrial material applications. For example, it is used for rubber reinforcing materials such as tire cords, power transmission belts, and conveyor belts, seat belts, fishing nets, safety nets, sewing threads, cover sheets, and bag fabrics.

However, the quality level required of recent polyester fibers for industrial materials is becoming higher and higher. In particular, efforts are being made to increase the strength of polyester fibers, reduce the amount of reinforcing materials used, and reduce costs while making products lighter and thinner.

Improved techniques for increasing the strength of polyester fibers are disclosed in JP-A-59-1714, JP-A-60-94619, and JP-A-63-196712.

In addition, as a material for modifying the surface of polyester fibers,
JP-A-61-19880, JP-A-61-4254
No. 6 and Japanese Unexamined Patent Publication No. 62-238871 are known.

<Problem to be solved by the invention> The above-mentioned JP-A-59-1714 and JP-A-60-94
No. 619, JP-A No. 63196712, etc. are excellent inventions for achieving high strength of polyester fibers. However, the polyester fiber obtained by this technique has a problem in that it has poor thermal dimensional stability compared to ordinary polyester fiber. The above problem lies in the fact that even after the orientation of crystalline and amorphous molecular chains has been sufficiently increased by hot stretching, the structure cannot be firmly fixed as it is. That is, in an attempt to fix the structure, the thermal setting conditions (
If the temperature, time, etc.) were increased, the structure would change due to the treatment, and the crystal orientation and the degree of orientation of the amorphous molecular chains could not be maintained in the highly oriented state immediately after stretching. As a result, no matter how high the stretching ratio was attempted, only a certain level of strength and elastic modulus could be obtained, and the strain in the molecular chains during stretching was only temporarily fixed. Relaxation occurred and only a product with poor thermal dimensional stability was obtained.

JP-A-61-19880, JP-A-61-4 mentioned above
The inventions described in JP-A No. 2546 and JP-A No. 62-238871 claim that low-temperature plasma treatment is effective for surface modification of organic fibers, and specifically, in a specific gas atmosphere. By performing low-temperature plasma treatment, the fiber surface is modified by crosslinking, etching, introducing active groups, or graft polymerization with a specific polymer.

In particular, an example is described in which low-temperature plasma treatment is applied to polyester fibers for industrial materials.

However, the low-temperature plasma treatment of polyester fibers is concerned with improving the adhesion between polyester fibers and rubber, and cords made of already drawn and heated polyester fibers are treated with low-temperature plasma, followed by resorcinol-formaldehyde. The present invention discloses a method of treating with a mixture of an initial condensate and a rubber latex.

Therefore, it can be said that the invention technique merely utilizes the surface treatment effect recognized as an effect of low-temperature plasma treatment. Therefore, no equivalent suggestion is made regarding the effects of improving mechanical and thermal properties such as increasing the modulus of elasticity and improving thermal dimensional stability.

The purpose of the present invention is to improve the polyester fiber, which has high strength and high elastic modulus obtained by the conventional hot drawing method, but has poor thermal dimensional stability. It also provides a polyester fiber with improved stability.

5 6- Furthermore, another object of the present invention is to improve the appropriate conditions for low-temperature plasma treatment, whereas conventional low-temperature plasma treatment has been developed as a surface treatment technology based on the idea that it acts only on the surface of fibers. It was discovered that, if selected, the action of low-temperature plasma can reach the inside of the fiber to be treated, and by using this as a new drawing method, it is possible to perform ideal drawing, which is different from conventional hot drawing. The object of the present invention is to provide a novel high-strength polyester fiber obtained by this method.

<Means and Operations for Solving the Problems> In order to achieve the above objects, the present invention has the following configuration. That is, (1) A high-strength polyester fiber having an intrinsic viscosity [η] of 0.7 or more and consisting essentially of polyethylene terephthalate, and having the following fiber structure parameters.

(a) Birefringence/n≧19'0 , ) and the central birefringence (Δn.) (δA n ,, l
) is 3X10--1 or less.

(e) Absolute difference between the crystallinity parameter (x(r-■),) of the surface layer of each single fiber and the crystallinity parameter (X(H) e) of the central part measured by laser Raman spectroscopy value (|δX(II).

. 1) is 2, 04’, :’l”]- below.

(2) In the high-strength polyester fibers of (1) and (2) above, the strength is 10 g/d or more and the initial elastic modulus Mi
130 g/d or more, and a dry heat shrinkage rate ΔSI5° of 10% or less.

(3) A high-strength polyester fiber as described in (1) and (2) above, characterized in that an adhesive is applied to the surface of the polyester fiber to be used as a rubber reinforcing material.

(4) A high-strength polyester fiber of the above (1) and (2), which is knitted or woven and used as a thick cloth or a thick belt.

(5) A high-strength polyester fiber of the above (1) and (2), characterized in that the polyester fiber is subjected to a strong twisting process and used as a sewing thread.

(6) A high-strength polyester fiber of the above (1) and (2), characterized in that the polyester fiber is knitted and used as a net.

It is.

The high-strength polyester fibers according to the invention consist essentially of ethylene terephthalate units, but may contain less than 10% of ester-forming components. Examples of ester-forming components include terephthalic acid, ethylene glycol, and ethylene oxide components, as well as aromatic dicarboxylic acids such as isophthalic acid, naphthalene dicarboxylic acid, and diphenyldicarboxylic acid, diol components such as propylene glycol and butylene glycol, or the former. This is a mixed polymer in which a polymer obtained from the above component and the latter component is melt-mixed with polyethylene terephthalate.

In order to be put to practical use mainly as a fiber for industrial materials, the high-strength polyester fiber according to the present invention not only has the high strength and high modulus of elasticity that are the objectives of the present invention, but also has excellent thermal dimensional stability. Since fatigue resistance and other properties are also required, it is essential that the polymer has a high degree of polymerization, and the intrinsic viscosity [η] of the polymer is 0. 7 or more, preferably 0.8 to 1.2
It is.

The birefringence Δn of the high-strength polyester fiber according to the present invention is 1
90X10-3 or more, preferably 190XIO-"~2
20×10-”. Compared to conventional high-strength, high-modulus polyester fibers, it has extremely high birefringence and is highly oriented.

Crystal orientation fe is 0.94 or more, preferably 0°95 or more.
2, it is highly oriented to the same degree or higher than conventional high strength, high modulus 0-polyester fibers.

The degree of amorphous molecular orientation fa is 0.55 or more, preferably 0.6
It is characterized by having a high orientation of 0 or more.

Next, the high-strength polyester fiber according to the present invention differs from conventional polyester fibers in the chemical composition of the surface layer of each single yarn constituting the fiber, and the oxygen element in the surface layer analyzed by X-ray photoelectron spectroscopy (ESCA). and the ratio of carbon element (0/C) is 0
．． 35 or less, and is characterized by a low oxygen concentration in the surface layer. On the other hand, the O/C ratio of the inner layer exceeds 0.35 and is almost close to the value of the pure polyethylene terephthalate component.

In addition, the microstructure of the high-strength polyester fiber according to the present invention is relatively uniform in both the surface layer and the inner layer of each single yarn, and the birefringence of the surface layer of each single yarn measured with a quantitative interference transmission microscope (
The absolute value of the difference between Δn, ) and the central birefringence (Δn.)
1δΔn.

It is less than 3X10-1, which is relatively small compared to the 2X10-8 to 5X10" of conventional polyester fibers. Furthermore, the surface layer of each single yarn measured with a laser Raman spectrometer is crystallinity parameter (X (
H) , ) and the central crystallinity parameter (X (H
). ) and the absolute value of the difference (|δX (H) ,,cl )
is 2.0 cm or less, preferably 0.1 or less. That is, the high-strength polyester fiber according to the present invention has a small distribution of orientation degree and crystallinity within the cross section of a single yarn, and conventional polyester fiber has a distribution of 1.0 to 3.0.
This shows that it is relatively small and homogeneous.

The high-strength polyester fiber according to the present invention characterized by the above fiber structure parameters has a strength of 10 g/
d or more, the initial elastic modulus is 130 g/d or more, the dry heat shrinkage rate measured at 150 ° C. is 10% or less, and it is a high-strength polyester fiber with high strength, high elastic modulus, and excellent thermal dimensional stability. .

The above-mentioned high-strength polyester fiber according to the present invention can be obtained by the novel method described below. That is, the high-strength polyester fiber of the present invention is obtained by cold-stretching an undrawn yarn having an intrinsic viscosity [η] of 0.7 or more until it has a birefringence of 20X10-'' to 100XIO-'' or at 100°C or less. After performing low-temperature thermal stretching to obtain an intermediately oriented yarn, the intermediately oriented yarn is stretched in a low-temperature plasma atmosphere under a tension of 1.0 to 5.0 g per denier within a range of 1.2 to 3.5 times. A highly oriented polyester fiber having a birefringence of 190XIO-'' or more is obtained by stretching the fiber.

The plasma used in the plasma stretching of the present invention is generated by applying a high voltage in a reduced pressure container filled with a specific gas, and such discharge can take various forms such as spark discharge, corona discharge, and glow discharge. Although there are various types of discharge, glow discharge is particularly preferred because of its uniform discharge and excellent activation effect. As the discharge frequency, low frequency, high frequency, or microwave can be used, and direct current can also be used.

Examples of the gas used in the present invention include Ar.

N2) Hl, CO2) CO, O2) HiOlCF,,N
H4, H,, air, etc., and non-polymerizable gases mixed thereof are preferable, and Ar, N,, CO2) H, 0° air, etc., which do not have a particularly strong etching effect, are preferable, but air is particularly practical. It is suitable for

Naturally, the surface of the polyester fiber obtained by the present invention changes in the composition of elements bonded to surface molecules, but as mentioned above, the ratio of oxygen and carbon in particular is significantly different from that of the polyester fiber before plasma stretching. It is a characteristic.

The plasma used for plasma stretching in the method for producing high-strength polyester fibers according to the present invention is 0.01 to 5
From the viewpoint of discharge stability, it is preferable to conduct the reaction under a pressure of 0 Torr, preferably 0°5 to 20 Torr. The applied voltage is 0°5 to 10KV, preferably 1 to 8KV.
It is.

The stretching ratio in the plasma stretching described above is within the range of 1.4 times to 3.5 times, preferably 1.6 times to 3.0 times, depending on the properties of the undrawn polyester yarn subjected to plasma stretching. is selected.

By using the plasma stretching, stretching can be performed while suppressing crystallization compared to conventional hot stretching methods, and therefore, it is possible to stretch at a high magnification, and the resulting polyester fiber can be highly oriented.

The plasma stretching may be performed in one stage or in multiple stages of two or more stages.

Plasma conditions are changed depending on the physical properties and form of the undrawn polyester yarn to be subjected to drawing, plasma applied voltage, atmospheric gas, degree of atmospheric pressure reduction, drawing speed, etc. However, the birefringence of polyester fiber obtained by plasma drawing is 19
0X103 or more, preferably 190X10-8 to 220
Stretching is performed by combining plasma conditions to obtain a high degree of orientation of x10-''.

The plasma-stretched polyester fibers described above may be further subjected to conventional hot stretching or heat treatment.

The apparatus used to produce the high-strength polyester fiber according to the present invention is not particularly limited, and may be a batch type that incorporates a drawing device in a vacuum container, or a continuous type that incorporates a sealing method. A hot plate, hot roll, etc. may be connected before and after the plasma drawing zone as necessary.

The polyester fiber obtained by the above-mentioned plasma stretching has a lower molecular weight drop during stretching than when stretched by the conventional hot stretching method. Furthermore, the density is somewhat low and the birefringence is high, indicating that crystallization is suppressed and high orientation is achieved.

The above phenomena indicate that smooth stretching is achieved by plasma stretching.

In this way, a high strength polyester fiber according to the present invention is obtained.

The high-strength polyester fiber according to the present invention is particularly preferably used for industrial material applications.

By heating the high-strength polyester fiber according to the present invention and applying an adhesive such as resorcinol, formalin, latex, etc., it can be preferably used as a rubber reinforcing material for tires, power transmission belts, conveyor belts, etc.

Further, the high-strength polyester fiber according to the present invention can be knitted or woven and preferably used as a thick cloth or a thick belt.

Furthermore, by subjecting the high-strength polyester fiber according to the present invention to strong twist processing, it can be preferably used as a sewing thread.

Furthermore, the high-strength polyester fibers according to the present invention can be knitted and preferably used as a net.

Next, the present invention will be explained based on Examples, and the method for measuring fiber physical properties according to the present invention is as follows.

(1) Intrinsic viscosity [η]: A sample was dissolved in an orthochlorophenol solution and measured at 25°C using an Ostwald viscometer.

(2) Birefringence Δn: Nippon Kogaku Kogyo Co., Ltd. PO) (D
It was determined by the ordinary Bereck convencator method using a line as a light source.

(3) Crystal orientation fc: using Rigaku X-ray generator (4036A), CuK
Measurements were made using α as the radiation source. It was determined from the half-width H0 of the intensity distribution curve of the (010) plane of equatorial interference using the following equation.

f c = (180'-Ho) /1800 (4) Degree of amorphous molecular orientation fa: R, J, Samuels, J, Polymer Sc
i, A-2, 10, 781 (1972).

Δn=Xfcane+(1-X)faan.

+/n.

Δn = Birefringence Δnt: Form birefringence (0) It was determined from the crystallinity or the following formula.

1/d=X/dc+(1-X)/d.

d: Density of sample d,: Density of amorphous part (1,335) dc: Density of crystal part (1,455) (5) Absolute value of the difference in birefringence between the surface layer and the center of the single filament
δΔnm-tI: Determined by measuring the average birefringence distribution observed from the side surface of the fiber by the interference fringe method obtained using a transmission interference microscope (for example, an interference microscope manufactured by Carl Zeiss Jena (East Germany)).

The position 2M from the surface of the fiber was defined as surface layer birefringence Δns, and the birefringence at the center of the fiber was defined as center birefringence Δnc, and the absolute value of the difference between the two was defined as 1|δΔn−0.

(6) Absolute value of the difference in crystallinity parameters between the surface layer and the center of a single fiber | δX (H), el; Measure the distribution of crystallinity parameters within the cross section of a single fiber using Raman spectroscopy did. Using a laser Raman microprobe (MOLE) manufactured by Jobin-Yvon (France), 〉C = 1730 cm-' of polyethylene terephthalate fiber
The half width of the Raman band due to zero stretching vibration was measured.

The half width is inversely proportional to the density (A, J, Me
1 reger, J., Polym, Sci., 10 3
17 (1972), the half values of the surface layer and center were determined, and the difference between the two was taken as the difference between the crystallinity parameters of the surface and center of the single yarn.

(7) X-ray photoelectron spectroscopy (ESCA) The sample was thoroughly washed with carbon tetrachloride, air-dried, and then subjected to measurement. Using an ESCA750 type device manufactured by Shimadzu Corporation, under the following conditions:
The ratio of oxygen to carbon filament number on the surface of the sample (number + A) is 0
7C was measured.

Excitation conditions: Mg, C1,2 line (1253,6ev) Energy correction: Binding energy of C1B main peak Lugie value to 284.6ev Combined.

Photoelectron escape angle (θ) = 90 degrees (8) Density ρ; Measurement was performed at 25° C. using a density gradient tube prepared with carbon tetrachloride as a heavy liquid and n-hebutane as a light liquid.

(9) Strength T/D, elongation E1, and initial elastic modulus MI=as defined by JIS-L1017. A sample was taken into a general shape and left in a temperature and humidity controlled room at 20°C and 65% RH for 24 hours.
The measurement was carried out using a 4-100 type tensile testing machine at a trial length of 25 cm and a tensile speed of 30 cm/min.

(10) Dry heat shrinkage rate △S+go (raw yarn), △5177 (
Code): Take the sample in a general shape and heat it in a temperature-controlled room at 20°C and 65% RH for 24 hours.
The sample was left for more than an hour and used as a measurement sample. 0 of the sample. Ig/d
A sample of length Lo measured by applying a load corresponding to It was left in the preparation room for 4 hours, the above load was applied again, and the measured length was calculated using the following formula.

△SSS. = ((Lo-L,)/Lo)xlOO(%
) △5177= ((LOLl)/LO)X100(%) <Example> Examples 1 to 4 and Comparative Examples 1 to 3 A polyethylene terephthalate polymer with an intrinsic viscosity [η] of 1.10 was used as a regular polyester for industrial materials. The fibers were spun using the slow-cooling melt spinning method used in fiber manufacturing. Directly below the spinneret, a heating cylinder with a length of 50 cm and an internal atmosphere temperature of 300°C was installed, and an undrawn yarn was obtained at a spinning speed of 500 m/min. The undrawn yarn was produced by adjusting the spinning discharge rate so that it would have 500 denier and 120 filaments after drawing.

The above-mentioned undrawn yarn is fed through a feed roll rotating at 30 m/min, and after one stage of drawing with a first drawing roll, a continuous yarn having a sealing mechanism at both ends is set between it and a second drawing roll. The film was passed through a processing-type low-temperature plasma treatment machine to perform second-stage stretching, and the first-stage stretching ratio, stretching roll temperature, and plasma stretching conditions were changed.

The effective processing length of plasma drawing was 100 cm, the gas used was air, and the frequency was 110 KHz, and the atmospheric gas pressure and applied voltage were changed according to changes in the physical properties of the undrawn yarn and the drawing speed.

For comparison, a hot plate with a length of 100 cm was used instead of the plasma stretching section, and hot stretching was carried out at different temperatures. A commercially available polyester fiber for tire cords was also used for comparison. The manufacturing conditions and physical properties of the polyester fibers are shown in Tables 1 and 2, respectively.

It can be seen that the high-strength polyester fiber according to the present invention has high strength, high elastic modulus, and excellent thermal dimensional stability.

(The following is a blank space) 3-24- <Effects of the invention> The high-strength polyester fiber according to the present invention is a polyester fiber with high strength, high modulus of elasticity, and excellent thermal dimensional stability.
The high-strength polyester fiber according to the present invention having such characteristics is excellent as a material for industrial use, and is particularly useful as a rubber reinforcing material for tire cords, power transmission belts, conveyor belts, seat belts, fishing nets, sewing threads, tents, tarpaulins, slings, etc.
It can be useful for safety nets, etc.

In addition, the effects of the plasma stretching method used in producing the high-strength polyester fibers of the present invention are that crystallization during stretching can be suppressed and highly oriented, that is, smooth stretching can be achieved. It is characterized by being able to easily obtain high-strength polyester fibers having high-quality characteristics according to the present invention, which can be stretched at low magnification and tension.

Claims (6)

[Claims] (1) A high-strength polyester fiber having an intrinsic viscosity [η] of 0.7 or more and consisting essentially of polyethylene terephthalate, and having the following fiber structure parameters. (a) Birefringence Δn≧190×10＾-＾3 (b) Degree of crystal orientation f_c≧0.94 (c) Degree of amorphous orientation f_a≧0.55 (d) Birefringence of the surface layer of each single fiber ( The absolute value of the difference between Δn_■) and the central birefringence (Δn_c) (|δΔn_■_−
＿c｜) is 3×10^-^3 or less. (e) The absolute value of the difference between the crystallinity parameter (X(H)_a) of the surface layer of each single yarn and the crystallinity parameter (X(H)_c) of the center part measured by laser Raman spectroscopy (
|δX(H)＿■＿−＿＿c|) is 2.0cm^-^1
below. (2) The high-strength polyester fiber according to claim 1, which has a strength of 10 g/d or more and an initial elastic modulus Mi
is 130 g/d or more, and the dry heat shrinkage rate ΔS_1_5_
A high-strength polyester fiber characterized by having 0% or less of 10% or less. (3) A high-strength polyester fiber according to claims 1 and 2, characterized in that an adhesive is applied to the surface of the polyester fiber to be used as a rubber reinforcing material. (4) A high-strength polyester fiber according to claims 1 and 2, characterized in that the polyester fiber is knitted or woven and used as a thick cloth or a thick belt. (5) A high-strength polyester fiber according to claims 1 and 2, characterized in that the polyester fiber is highly twisted and used as a sewing thread. (6) A high-strength polyester fiber according to claims 1 and 2, characterized in that the polyester fiber is knitted and used as a net.