JPH0376810A - Polyester finer having high toughness and low shrinkage and its production - Google Patents

Abstract

PURPOSE:To provide the subject fiber containing ethylene terephthalate as a main constituent unit, satisfying a specific physical property, having high strength, high elongation, low shrinkage, high IV(intrinsic viscosity), low COOH content and excellent durability and useful in a non-rubber use. CONSTITUTION:The objective fiber having an intrinsic viscosity(IV) of 0.91-1.05, a terminal COOH content of <=18 equivalent/10<6>g, a yarn strength of >=9.2g/d, a yarn elongation at break of 16-21%, an intermediate elongation of yarn of 8-12% (elongation under a load of 4.5g/d) and dry-heat shrinkage of <=6% (150 deg.CX30min) is produced by melting a polyester having an intrinsic viscosity of >=0.95 at 280-300 deg.C, pressurizing the molten polymer with a gear pump to 400-1,200kg/cm<2>G, extruding through a spinneret, passing the spun fiber through a heating cylinder placed immediately below the spinneret and having an atmosphere temperature maintained to a level to give an undrawn fiber having a birefringence of <=300X10<-5> when taken up at a speed of <=700m/min, drawing the undrawn yarn at a draw ratio of >=5 and subjecting the drawn fiber to relaxed heat-treatment at >=180 deg.C and a relaxation ratio of 5-10%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to high toughness, low shrinkage polyester fibers and methods for producing the same. More specifically, the present invention relates to a polyester fiber that has high strength, high elongation, and exhibits good dimensional stability, and is particularly suitable for industrial materials, and a method for producing the same.

[Conventional technology]

Polyester fibers have excellent, well-balanced properties in terms of strength, elastic modulus, and dimensional stability, so they are used in tires,
■It is preferably used as a reinforcing material for rubber structures such as belts and conveyor belts, and is also used in large quantities for many non-rubber industrial materials, including fishing nets, robes, seatbelts, and canvas.

In rubber material applications, there has been an increasing demand for high modulus and low shrinkage, especially in the tire cord field, so in recent years, high modulus, low shrinkage, and fatigue resistance achieved by high spinning speed and high tension spinning have been developed. Excellent polyester fibers and methods for producing the same have been proposed. In such rubber material applications, in order to improve the adhesion between fibers and rubber, a dip treatment process is performed under much harsher processing conditions than those used in the spinning process, so the physical properties of the cord after dip treatment must be carefully evaluated. Since the primary objective is to achieve the desired high strength, high modulus, and low shrinkage, the physical properties (strength, elongation, shrinkage rate) of the yarn itself do not have a significant effect.

On the other hand, in industrial material applications, the quality of the raw yarn is often reflected in the quality of the final product, as the harsh heat treatment that is applied to rubber materials is generally not performed. Therefore, in this field, increasing the strength at the yarn stage has an important meaning.

In addition, conventionally, in the property field, the degree of polymerization is 0.6 to 0.8 in terms of intrinsic viscosity (IV), and even higher is 0.85 to 0.
．． 90, and the terminal carboxyl group is 20 to 40.
Equivalent/106g is common. However, in order to improve durability under harsh usage environments, it is desirable to improve polymer potential by increasing IV and decreasing COOH.

In response to these problems, various proposals have been made for increasing the strength, toughness, and shrinkage of industrial fibers for industrial fibers, including those for use in rubber materials. For example, increasing strength,
Regarding increasing toughness, proposals have been made in Japanese Patent Publication No. 55-32805 and Japanese Patent Publication No. 56-31365, but although high strength of 9.0 to 9.4 g/d has been achieved, elongation is low at 12-13%, and low shrinkage is insufficient.
The IV is 0.88 to 0.90, which is not a sufficient level for industrial materials.

Regarding low shrinkage, proposals have been made in JP-A-52-99317 and JP-A-55-158324, but although these have achieved the goal of low shrinkage,
The strength remains at an unsatisfactory level of 7 to 9 g/d.

[Problem to be solved by the invention]

The present invention was made against the background of the problems of the prior art, and has the characteristics of high strength, high elongation (high toughness), and low shrinkage, and is suitable for industrial material applications, especially in the field of non-rubber materials. Our goal is to provide polyester fibers.

[Means to solve the problem]

The present invention relates to a polyester fiber containing ethylene terephthalate as a main structural unit, and which includes the following (a) to (f).
The purpose of the present invention is to provide a high toughness, low shrinkage polyester fiber characterized by having the following properties at the same time.

(a) Intrinsic viscosity (IV) 0.91 to 1.05 (b)
Terminal carboxyl group (COOH) 18 equivalents/10
6 g or less (c) Yarn strength 9.2 g/d or more (d) Yarn breaking elongation 16-21% (e) Yarn intermediate elongation (elongation at 4.5 g/d) 8-1
2% (f) Dry heat shrinkage rate (150″C x 30 minutes) 6% or less In addition, the present invention provides the following method when obtaining polyester fiber by melt spinning and drawing polyester having ethylene terephthalate as a main constituent unit. The present invention provides a method for producing a high-toughness, low-shrinkage polyester fiber comprising steps (i) to (iv).

(i) Melting polyester having an intrinsic viscosity of 0.95 or more at a melting temperature of 280 to 300°C.

(ii) The molten polymer was pumped to a pressure of 400 with a gear pump.
After increasing the pressure to ~1200 kg/c11IG, discharge from the spinneret.

(iii) A heating cylinder is provided directly below the spinneret, and the ambient temperature is maintained so that the birefringence of the undrawn yarn drawn at 700 m/min or less is 300×10 −′ or less.

(IV) After stretching the undrawn yarn five times or more,
5-10% relaxing heat treatment at temperatures above °C.

Various physical property values in the present invention are values determined as follows.

Intrinsic viscosity (IV) is 35 using an Ostwald viscometer.
This is a value obtained by measuring an orthochlorophenol solution at °C.

The terminal carboxyl group (COOH) was determined by the Ni-Conix method (Makromol, chem.

26, p. 226, 195B).

The re-stretch curve, strength, cutting elongation, intermediate elongation, and dry heat shrinkage are as follows:
These are curves or numerical values obtained according to the method described in JIS L1013.

The birefringence can be obtained by measuring the birefringence using a polarizing microscope using bromonaphthalene as an immersion liquid, using a Berek compensator, or by the tarp john method.

The polyester used in the present invention mainly refers to polyethylene terephthalate consisting of a terephthalic acid component and an ethylene glycol component, but a polyester in which a portion of the terephthalic acid component, usually 10 mol% or less, is replaced with another dicarboxylic acid component. and/or a polyester in which a portion of the ethylene glycol component, typically 10 mol % or less, is replaced by other diol components. In addition, for example, a modifier, a stabilizer, etc. may be optionally used in the polyester, if necessary.

The degree of polymerization of the fiber of the present invention made of such polyester is
In order to maintain sufficient strength for industrial materials, the intrinsic viscosity (IV) is 0.91 to 1.05, particularly 0.92.
A range of 1.00 to 1.00 is preferable.

Further, the terminal carboxyl group is preferably at most 18 equivalents/106 g, particularly preferably at most 15 equivalents/106 g.

In other words, fibers for industrial materials have traditionally had an intrinsic viscosity (
IV) is 0.62 to 0.90, and the terminal carboxyl group is 1
9 to 40 equivalent/106 g was used, but as mentioned above, it has a higher IV and lower COOH than the conventional system, and has high strength and low shrinkage of the fiber, as well as chemical stability and durability. One of the features of the present invention is that it aims to improve performance.

Further, the polyester fiber of the present invention is characterized by having, in addition to the above-mentioned intrinsic viscosity and carboxyl group, a re-stretch curve and shrinkage characteristics suitable as a fiber for industrial materials.

That is, the yarn strength is 9.2 g/d or more, particularly preferably 9.3 g/d or more, and the yarn breaking elongation is 16 to 21%.
, particularly preferably 17-21%, yarn intermediate elongation (4,
elongation at 5 g/d) of 8 to 12%, particularly preferably 9 to 12%.
12%, and dry heat shrinkage rate (150℃ x 30 minutes)
, is 6% or less.

The re-stretching curve is shown in FIG. 1, and the polyester fiber of the present invention is represented by curves A and B in FIG. Elongation 1. That is, the elongation at a stress of 4.5 g/d passes through the solid line in the figure.

The polyester fiber of the present invention has a yarn strength of 9.2 g/d.
As mentioned above, the yarn has an extremely high strength and high elongation with a breaking elongation of 16 to 21%, which is at the level of currently commercially available high tenacity yarns (yarn strength of 8.8 to 9.2 g/d, yarn breaking elongation of 1
2 to 15%, as shown by curve F in FIG. 1). Here, if the yarn strength is lower than 9.2 g/d, it is insufficient as a fiber for industrial materials. Furthermore, if the yarn breaking elongation is less than 16% and the yarn intermediate elongation is less than 8%, the toughness is insufficient and the low shrinkage characteristic cannot be achieved. On the other hand, the yarn cutting elongation is 2
If it exceeds 1% or if the yarn intermediate elongation exceeds 12% (
(as shown by curves G and H in FIG. 1), it is difficult to maintain the target strength level, and problems in drawing operability such as yarn breakage and fuzz occur.

Furthermore, the polyester fiber of the present invention has a dry heat shrinkage rate of 6.
% or less, and exhibits good dimensional stability especially in fields where fibers for industrial materials are used untwisted or with a relatively low number of twists and are not subjected to severe heat treatment.

When the dry heat shrinkage rate exceeds 6%, the dimensional stability against heat deteriorates and the product may not be usable depending on the application.

The polyester fiber of the present invention has high IV and low COOH,
It has extremely high potential as a polymer, and exhibits high strength and high elongation, and exhibits characteristics of high elongation and low shrinkage compared to conventional high-strength types (shown by curves E and F in Figure 1). In addition, the conventional low shrinkage type (first
Curve G in the figure shows higher strength than the old fiber, and has physical properties preferable as a fiber for industrial materials.

The polyester fiber of the present invention can be obtained by the following method. That is, polyester having an intrinsic viscosity (IV) of 0.95 or more, preferably 0.98 to 1.20, is
It melts at ~300°C, particularly preferably at 285-295°C. If the melting temperature is lower than 280°C, stable spinning of high IV polymer is impossible, while if it is higher than 300°C, the degree of polymerization will decrease and the number of terminal carboxyl groups will increase significantly, making it impossible to achieve the desired high IV and low COOH. .

On the other hand, various known methods can be used to reduce Coo)I. For example, (1) Tokuko Sho 44-2
7911, a method of reacting a molten polyester with phenyl glycidyl ether; (2) A method of reacting a molten polyester with a linear polyester carbonate, as described in Japanese Patent Publication No. 45-41235; (3) ) A method of reacting polyester with ethylene oxide as described in Japanese Patent Publication No. 47-12891, (4) A method of reacting polyester with glycol ester of oxalic acid or oxalic acid polyester as described in Japanese Patent Publication No. 4B-35953, ( 5) Special Public Service 1977-
(6) A method of reacting a polyester with a diaryl oxalate and/or a diaryl malonate and a diaryl carbonate as described in Japanese Patent Publication No. 49-5233. , (7) A method of reacting a polyester with a carbosiimide as described in U.S. Pat. It is possible to adopt it as needed depending on the viscosity and the amount of terminal carboxyl groups, and a method in which the terminal carboxyl groups are reduced to 18 equivalents/10 bg or less without reducing the degree of polymerization is particularly preferred.

Next, the molten polymer was pumped with a gear pump at a pressure of 400~
After increasing the pressure to 1,200 kj/aMG, it is discharged from a spinneret. The pressure increasing means includes an arbitrary resistor, such as a wire mesh filter, a filter medium, a narrow part, etc., between the hegear pump and the spinneret. This pressure increase before discharge improves the spinnability of the high IV polymer and reduces the orientation of the undrawn yarn. That is, if the discharge pressure is less than 400 kg/dG, discharge failure will occur due to the high IV polymer, and the degree of orientation of the obtained undrawn yarn will become high, making it difficult to increase the strength by drawing at a high magnification. On the other hand, the discharge pressure is 1. If it exceeds 200 kg/cIIlG, the degree of polymerization will decrease significantly or a discharge failure will occur on the nozzle surface.

Furthermore, under the spinneret, the degree of orientation of the undrawn yarn is 300X10-' or less in terms of birefringence, particularly preferably 200X
The heating cylinder is arranged so that the temperature is 10-5 or less. If the birefringence exceeds 300 x 10-', it is not preferable because it is not possible to satisfy both high strength due to high-magnification stretching and low shrinkage characteristics.

In order to keep the birefringence of the undrawn yarn within the above range, the take-up speed is 700 m/min or less, preferably 600 m/min or less. The length of the heating cylinder is preferably 20 to 100 cm, and the ambient temperature is preferably 300 to 450°C.

Thereafter, the undrawn yarn is stretched 5 times or more and 180°
The polyester fiber of the present invention can be obtained by subjecting it to a relaxing heat treatment of 5 to 10% at a temperature of C or higher. This stretching may be performed continuously following spinning, or may be performed after spinning and then winding.

As a heating means for stretching, it is preferable to perform one stage of stretching at once by spraying heated steam at 300°C or higher, preferably 350 to 600"C, from the viewpoint of increasing the degree of elongation. You can go.

For relaxing heat treatment, it is effective to use a heated roller, hot plate, etc., and the surface temperature at this time is 180°C.
above, preferably 190 to 250°C, and 180°
If it is less than C, the reduction in shrinkage is insufficient. Further, if the relaxation rate is less than 5%, it is insufficient to achieve high elongation and low shrinkage, while if it exceeds 10%, yarn waviness increases and strength decreases.

[Effect]

According to the present invention, while increasing the potential of physical properties and chemical stability by increasing the IV and lowering the COOH, a low-oriented undrawn yarn can be stretched at a high ratio and subjected to a high-relaxation heat treatment. As a result, high toughness, low shrinkage polyester fibers having a structure that is highly oriented and has a high degree of crystallinity can be obtained. This polyester fiber has high IV,
It has excellent strength properties such as high strength and high elongation, and also maintains good dimensional stability and chemical stability, making it extremely suitable as a fiber for industrial materials.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Examples 1 to 2 Polyethylene terephthalate chips having an intrinsic viscosity of 1.10 were melted using an extruder at a melting temperature of 290°C. At this time, 0.4% by weight of 0-phenyl-phenyl-glycidyl ether was added as a carboxyl terminal group blocking agent. This molten polymer was supplied to a gear pump, passed through a spinning pack, and was discharged from a spinneret having a hole diameter of 0.40011 and a number of holes of 250. A wire mesh filter and sand were inserted into the spinning pack to increase the pressure of the polymer, and the pressure immediately before the spinning pack was 520 kg/c111.

The length of the discharged polymer is 50 cm, and the ambient temperature is 360°C.
25℃ cooling air at 6.0Nrt.
The sample was cooled and solidified while being sprayed for f/min, and then an oil agent was applied using a conventional oiling device and the sample was taken to a take-up roll. The obtained undrawn yarn is immediately passed between 3. drawing rolls without being wound up. After stretching by injecting heated steam at 0 kg/dG and 450°C, the film was subjected to a relaxing heat treatment of 7.0 to 9.5% with a relaxing roll. On this occasion,
The surface temperature of the stretching roll and relaxation roll is 20
The temperature ranged from 0 to 210°C.

The physical properties of the obtained drawn yarn are shown in Table 1, and it had excellent properties such as high strength, high elongation, and low shrinkage, and also had good drawability.

In addition, the re-stretching curve of the drawn yarn obtained in Example 1 is A in FIG. 1, and the re-stretching curve of the drawn yarn obtained in Example 2 is B in FIG.
are shown respectively.

Comparative Examples 1 to 2 The same polymer as in Example 2 was spun and stretched in the same manner as in Example 2, except that the melting temperature, spinning back pressure, and heating cylinder conditions were changed as shown in Table 1. A drawn yarn was obtained.

As shown in Table 1, the obtained drawn yarns had both low strength and elongation, and poor drawability.

Comparative Example 3 The same polymer as in Example 2 was spun and stretched under the same spinning conditions and draw ratio as in Example 2, and the relaxing heat treatment conditions for stretching were changed as shown in Table 1 to obtain a drawn yarn.

The physical properties of the obtained drawn yarn are shown in Table 1, and it was found that the elongation was low and the shrinkage rate was high. The re-stretching curve of the obtained drawn yarn is shown as E in Figure 1.
It is shown by

Comparative Example 4 A conventional high-strength type fiber was obtained by spinning and drawing under the conditions shown in Table 1 (the IV of the chip was 1.00 and no end-capping agent was used).

The re-stretching curve of the obtained drawn yarn is According to F in Figure 1 Show.

〔Effect of the invention〕

As described above, the polyester fiber of the present invention has high toughness (high strength, high elongation), low shrinkage, high rv,
It is expected to have low COOH and excellent durability, making it extremely useful in the industrial material field, especially in non-rubber applications.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the re-stretching curve of polyester fiber. In FIG. 1, A is the redraw curve of the drawn yarn obtained in Example 1, B is the redraw curve of the drawn yarn obtained in Example 2, and E and F are the redraw curves of the drawn yarn obtained in Example 2. G and H show the re-stretching curves of the fibers, and G and H indicate the re-stretching curves of conventional low-shrinkage type polyester fibers.

Claims (2)

[Claims] (1) A high-toughness, low-shrinkage polyester fiber containing ethylene terephthalate as a main structural unit and characterized by having the following properties (a) to (f) at the same time. (a) Intrinsic viscosity (IV) 0.91 to 1.05 (b) Terminal carboxyl group (COOH) 18 equivalents/10
^6g or less (c) Yarn strength 9.2g/d or more (d) Yarn breaking elongation 16% to 21% (e) Yarn intermediate elongation (elongation at 4.5g/d) 8 to 1
2% (f) Dry heat shrinkage rate (150℃ x 30 minutes) 6% or less (2) A method for producing high-toughness, low-shrinkage polyester fibers, which includes the following steps (i) to (iv), in which polyester fibers are obtained by melt-spinning and drawing polyester containing ethylene terephthalate as a main structural unit. (i) Melting polyester having an intrinsic viscosity of 0.95 or more at a melting temperature of 280 to 300°C. (ii) The molten polymer is pumped with a gear pump at a pressure of 400~
After increasing the pressure to 1,200 kg/cm^2G, discharge from the spinneret. (iii) A heating cylinder is disposed directly below the spinneret, and the ambient temperature is maintained so that the birefringence of the undrawn yarn drawn at 700 m/min or less is 300×10^-^5 or less. (iv) After stretching the undrawn yarn by 5 times or more,
5-10% relaxing heat treatment at a temperature of ℃ or higher.