JP2688708B2 - Polyester monofilament and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a polyester monofilament having novel properties and a method for producing the same, and more specifically, to an elongation modulus, a heat shrinkage stress and a maximum of the heat shrinkage stress. The present invention relates to a polyester monofilament having a high point (peak temperature) and a small heat shrinkage ratio, which has novel properties suitable for industrial fabric applications, and an efficient production method thereof.

(Prior Art) Among polyesters, polyethylene terephthalate (hereinafter abbreviated as PET) has excellent chemical and physical properties and has been widely used as an industrial monofilament.

Then, for example, a material monofilament used in the field of industrial fabrics such as for paper machines, for over-clothing, for rubber reinforcement and for screen gauze has a small thermal shrinkage, and further has an elongation elastic modulus, a thermal shrinkage stress and a peak temperature. High quality is required.

That is, although the monofilament having a large heat shrinkage ratio can easily modify the woven surface of the cloth at the time of weaving, it has a problem that it lacks dimensional stability against heat setting and impairs the finished size of the cloth.

Also, when the elongation modulus and heat shrinkage stress of the monofilament are low, especially when the heat shrinkage stress is low, the pressing force between the warp and weft threads in the knuckle part of the fabric does not increase when the greige is set. Misalignment is likely to occur, which causes problems such as impairing the scanning stability of the fabric and wrinkles. In addition, wrinkles caused by misalignment make it easier to destroy the part, which further shortens the service life of the fabric. That is not desirable.

Further, even if the monofilament has a high heat shrinkage stress, if the peak temperature is low, when the heat setting during weaving of the fabric is performed at the peak temperature or higher, the knuckle part once tightened with the maximum heat shrinkage stress is tightened. The force is reduced by heating above the maximum peak temperature, and it is possible to apply only a cloth pouch that can be easily misaligned with a finger, for example.

Under such circumstances, various studies have been conducted with the aim of improving the properties of industrial polyester monofilaments.

For example, for the purpose of reducing the shrinkage rate of PET monofilament, a method of stretching in hot water and then subjecting it to relaxation heat treatment at a temperature 5 to 40 ° C. lower than the melting point of PET (JP-A-48-
18517) and a single step in water at 80 to 100 ° C,
A method of performing a two-stage stretching in a gas of 200 to 300 ° C or a liquid of 150 to 200 ° C, and then performing a relaxation heat treatment in a gas of 300 to 400 ° C or a liquid of 200 to 250 ° C (Japanese Patent Publication No. 53-9298). ) Have been proposed, the PET monofilament obtained by these methods achieves a low shrinkage ratio and achieves the dimensional stability of the fabric, but the elongation elastic modulus and the heat shrinkage stress decrease, so In addition to making it difficult to correct the woven surface by setting, misalignment is likely to occur when using the fabric, causing not only defects such as wrinkles and shortening of life, but also when using a mesh structure such as a screen gauze, There is a problem that mesh irregularity occurs due to misalignment.

Further, JP-A-58-22081 and JP-A-59-7
In the 6917 publication, PET fibers having an increased heat shrinkage stress have been proposed, but since these PET fibers have a too large dry heat shrinkage of 200 ° C. of 20% or more, the finish dimension of the fabric is significantly impaired. It includes the defect.

Further, in JP-A-59-187618, a PET fiber having a low heat shrinkage ratio and a high heat shrinkage stress is known, but since the peak temperature of this PET fiber is as low as 100 ° C. or lower, There was a problem that the tightening force of the knuckle part was lowered during high temperature heat setting, and misalignment was easily caused.

Furthermore, as a manufacturing method of PET monofilament, 8
Stretched one step 3.3 to 3.5 times in a water bath at 5 to 95 ℃, 150 to 260
200-260 ℃ after stretching 1.7 to 2.3 times in a gas at ℃
Heat treatment at 1.0 to 0.95 times in the above gas (Japanese Patent Publication No.57-2)
No. 3006), a single stretch of 2.0 to 2.5 times in a humid heat of 85 to 100 ° C., a double stretch of 2.0 to 4.0 times in a gas of 200 to 300 ° C., and a 1.0 scale in a gas of 200 to 300 ° C. Heat treatment at ~ 0.9 times (JP-A-60-126317) and single stretching in water at 70 ~ 100 ° C by 4 ~ 6 times, and the total draw ratio becomes 6.0 ~ 7.5 times at a temperature 15 ° C lower than the melting point. After the two-stage drawing, the method of heat-treating at a temperature lower than the melting point by 15 ° C. and a restricted shrinkage of 0 to 5% (Japanese Patent Publication No. 56-4644) is known. In the method, the elongation elastic modulus is insufficient, the heat shrinkage stress is too low,
Moreover, only PET monofilaments having a large heat shrinkage can be obtained, and this involves problems in weavability and misalignment when used for industrial purposes.

(Problems to be Solved by the Invention) As described above, the PET monofilament used in the field of industrial fabrics is required to have characteristics that the thermal shrinkage rate is small and the elongation elastic modulus, the thermal shrinkage stress and the peak temperature thereof are high. However, it is not known that these four properties are balancedly satisfied, and the conventional PET monofilament lacks any one of the above-mentioned properties or two or more properties, resulting in poor surface modification during weaving and However, the problems such as the occurrence of misalignment when using the fabric remain.

As a measure for misalignment, there is known a method of limiting the degree of freedom of each yarn constituting the fabric by increasing the weaving density and thickening the yarn, but this method not only increases the cost by increasing the raw materials used, Depending on the use of the cloth, it may cause excess or decrease in drying efficiency, which is not preferable.

In view of such a situation, an object of the present invention is to easily perform heat correction on a woven surface of a fabric, and to have excellent thermal dimensional stability, without causing misalignment when the fabric is used,
It is an object of the present invention to provide a PET monofilament capable of maintaining a stable woven surface and a method for producing the same.

The above-mentioned object of the present invention can be achieved by a PET monofilament having a novel property that the elongation modulus, the heat shrinkage stress and the peak temperature of the heat shrinkage stress are high, and the heat shrinkage ratio is small, and Have PET
It was found that the monofilament can be obtained by a unique process of drawing at a relatively low temperature and then subjecting to a fixed length heat treatment at a high temperature, and completed the present invention.

(Means for Solving the Problems) That is, the present invention provides an ethylene terephthalate unit containing 85 units.
A monofilament made of polyester having an intrinsic viscosity of 0.64 or more in an amount of at least 100% by weight and having a heating rate of 100 ° C /
The maximum point of heat shrinkage stress in the process of heating and heating in minutes is 20
A polyester monofilament characterized by being present at 0 ° C. or higher and having the following characteristics and containing ethylene terephthalate unit in an amount of 85% by weight or more, and having an intrinsic viscosity of 0.
A polyester of 64 or more is melt-spun in a water bath, the obtained undrawn yarn is drawn in one stage at 3.5 to 5.0 times at a temperature of 80 to 100 ° C., and then the total draw ratio is 5.0 to 5.8 at a temperature of 110 to 140 ° C. After being double-stretched so that it doubles, 0.98-at a temperature of 180-260 ℃
A gist of the present invention is a method for producing a polyester monofilament having the following characteristics, which is characterized by heat treatment under a substantially constant length of 1.05 times.

Maximum heat shrinkage stress ≧ 0.25 g / d 3% Elongation elastic modulus ≧ 95% 200 ° C. Dry heat shrinkage ≦ 15% The raw material polymer used in the present invention is a copolymerized polyester containing 85% by weight or more of polyethylene terephthalate and ethylene terephthalate units. Alternatively, it is a blend containing these polyesters as a main component, and examples of copolymerization units other than ethylene terephthalate units include ethylene isophthalate units, butylene terephthalate units, and butylene isophthalate units.

However, the polyester monofilament of the present invention,
The intrinsic viscosity measured at 25 ° C in orthochlorophenol is
It is important to be in the range of 0.65 or more, particularly 0.70 or more, and if it is less than 0.65, sufficient heat shrinkage stress and elongation elastic modulus cannot be obtained even by the method of the present invention, which is not preferable.

The polyester monofilament of the present invention may contain a small proportion of another blended thermoplastic polymer, and further, a heat-resistant agent, a light-resistant agent, a weather-resistant agent, a plasticizer, a matting agent, an abrasive, a lubricant, Conventional additives such as antistatic agents, dyes and pigments can be included.

And, the polyester monofilament of the present invention,
It is important that the maximum point (peak temperature) of heat shrinkage stress in the process of heating and heating at a heating rate of 100 ° C./min exists at 200 ° C. or higher and the following three characteristics are satisfied.

Maximum heat shrinkage stress ≧ 0.25g / d 3% Elongation modulus ≧ 95% 200 ℃ Dry heat shrinkage ≦ 15% Here, the maximum point (peak temperature) of heat shrinkage reaction force is Kanebo Engineering's thermal stress measurement. Machine (type KE-
2L type) is the temperature at which the maximum heat shrinkage stress peak appears when the heat shrinkage stress is measured under the conditions of initial load of 0.05 g / d and heating rate of 100 ° C.

That is, as shown in the model diagram in the drawing, when the measured atmosphere temperature (horizontal axis) is gradually increased, the heat shrinkage stress (vertical axis) increases almost linearly, and eventually the maximum peak is drawn. And then descend. The temperature at which this maximum peak appears is the maximum point of heat shrinkage stress (peak temperature), and the heat shrinkage stress corresponding to this peak temperature is the maximum heat shrinkage stress.

And, in the relationship between the peak temperature and the maximum heat shrinkage stress, the peak temperature is 200 ℃ or more, particularly 220 ℃ or more, and the maximum heat shrinkage stress is 0.25 g / d or more, particularly 0.30 g / d
It is necessary to satisfy the above two requirements, and the peak temperature
If the temperature is less than 200 ° C, misalignment is likely to occur during weaving of the fabric, especially in heat setting, and the maximum heat shrinkage stress is 0.25 g / d.
If it is less than the range, not only is it difficult to modify the surface of the fabric by heat setting, but also the knuckle portion and the pressing force between the yarns after the heat setting are insufficient, whereby misalignment is likely to occur when the fabric is used, which is not preferable.

Even with the polyester monofilament of the present invention, when heat setting is performed at a peak temperature or higher during fabric production, misalignment may occur, but according to the polyester monofilament of the present invention, it is easy at a temperature of 120 to 200 ° C. Since it is possible to obtain the heat setting effect, it is not necessary to perform heat setting at a temperature equal to or higher than the peak temperature, and it is possible to effectively eliminate the problem of misalignment of the cloth.

Further, the polyester monofilament of the present invention has a JI
S L1013 1981 7.9. Elongation elastic modulus It is necessary that the 3% elongation elastic modulus measured by the B method is 95% or more, particularly 98% or more, and this 3% elongation elastic modulus is woven with monofilaments less than 95%. The fabric has a weak pressing force between the warp yarn and the weft yarn in the knuckle portion and is liable to cause misalignment. For example, running stability is lost when the fabric is used as a belt-like fabric such as a mesh net, and the misaligned portion is wrinkled. It tends to be damaged from that portion, and the durability life is significantly impaired, which is not preferable. Furthermore, when it is used for a mesh structure such as a screen gauze, the mesh specification deviates due to misalignment, which is not preferable.

Furthermore, the polyester monofilament of the present invention,
JIS L1013 1981 7.15. (2) Dry heat shrinkage measured by the B method: 200 ℃ dry heat shrinkage must be 15% or less, especially 12% or less, when 200 ℃ dry heat shrinkage exceeds 15% Is not preferable because the dimensional change during weaving of the cloth is remarkable and the desired mesh opening cannot be obtained.

Elongation elastic modulus, heat shrinkage stress, peak temperature of this heat shrinkage stress and the polyester monofilament of the present invention satisfying the heat shrinkage in the above-mentioned range, can be easily heat-corrected at the time of fabric weaving, and thermal dimensions. In addition to being excellent in stability, it is possible to maintain a stable woven surface without causing misalignment when the cloth is used, and it has new characteristics suitable for industrial cloth applications.

Next, a method for producing the polyester monofilament of the present invention having the above new characteristics will be described.

In the production of the polyester monofilament of the present invention, first, a polyester having an intrinsic viscosity of 0.65 or more is melt-extruded from a spinneret of an extruder by a conventional method and then cooled and solidified in a water bath to obtain an undrawn yarn.

The obtained undrawn yarn is subsequently subjected to drawing for obtaining a high elongation elastic modulus and a high heat shrinkage stress, but it is drawn in two steps because a sufficiently high draw ratio cannot be obtained by only one step drawing.

First, the first stage drawing is carried out at a relatively low temperature and a high draw ratio, that is, at a temperature of 80 to 100 ° C, especially 85 to 95 ° C, a condition of 3.5 to 5.0 times, especially 3.8 to 4.5 times.

If the first-stage drawing temperature exceeds 100 ° C, the drawing tension will be significantly reduced, making it difficult to draw and not producing a monofilament with a high elongation elastic modulus. Not preferable.

Further, if the first stage draw ratio is less than 3.5 times, it is not possible to obtain a monofilament that is uniform and has high elongation elastic modulus and high heat shrinkage stress, and conversely, if it exceeds 5.0 times, in the next second stage draw. It is not preferable because the yarn is easily broken.

As the heat medium used for the first-stage drawing, any substance can be easily removed from the surface of the monofilament and is not a substance which physically or chemically changes the monofilament. However, a hot water bath or a heated air bath is economically preferable because it is a relatively low temperature drawing.

Next, the second stage stretching is slightly higher than the first stage stretching temperature in order to obtain stable stretchability, but at a relatively low temperature and a relatively high draw ratio, that is, 110 to 140 ° C, especially 120 ° C. The conditions are such that at a temperature of up to 130 ° C, the total draw ratio is 5.0 to 5.8 times, especially 5.3 to 5.5 times.

When the second drawing temperature exceeds 140 ℃, the monofilament with high elongation modulus and high heat shrinkage stress cannot be obtained.
If it is less than the above range, the yarn is easily broken during drawing, which is not preferable.

Further, if the second draw ratio is too low, a monofilament having a high elongation elastic modulus and a high heat shrinkage stress cannot be obtained. On the contrary, if it is too high, not only the yarn is easily broken, but also the next heat treatment is performed. It is not preferable because a monofilament having a low shrinkage cannot be obtained.

The heat medium used in the second stage drawing is any substance that can be easily removed from the surface of the monofilament and that does not essentially give physical or chemical changes to the monofilament. Can also be used, but a heating device such as a liquid bath filled with an inert liquid having a high boiling point, an air furnace, an inert gas furnace, an infrared furnace, and a high-frequency furnace is preferably used.

The monofilament thus stretched is subjected to a heat treatment in order to reduce the shrinkage ratio and increase the peak temperature of the heat shrinkage stress without impairing the high elongation elastic modulus and the high heat shrinkage stress obtained by the stretching. It

Heat treatment at 180-260 ℃, especially at high temperature of 200-240 ℃,
It is performed under a substantially constant length of 0.98 to 1.05 times, especially 1.0 to 1.03 times.

When the heat treatment temperature exceeds 260 ° C, not only the monofilament is easily melt-broken, but also a monofilament having a high elongation elastic modulus and heat shrinkage stress cannot be obtained. Although it increases, the peak temperature decreases and the shrinkage ratio increases, which is not preferable.

Further, when the heat treatment ratio decreases, the shrinkage ratio decreases, but it is not possible to obtain a monofilament having a high elongation elastic modulus and heat shrinkage stress. Conversely, if it is too high, a monofilament having a high elongation elastic modulus and heat shrinkage stress can be obtained. It is not preferable because it disappears.

Although the reason why the effect in the substantially constant length heat treatment is expressed is not clear, the high temperature heat treatment in the constant length region effectively removes the intermolecular strain generated at the low temperature,
It is considered that the shrinkage rate decreases and the peak temperature rises without causing a significant decrease in the elongation elastic modulus and the heat shrinkage stress.

As a heating device used for this heat treatment, a liquid bath filled with an inert liquid having a high boiling point similar to the above-described second stage drawing,
Examples thereof include an air furnace, an inert gas furnace, an infrared furnace, a high frequency furnace, and the like.

The polyester monofilament of the present invention thus obtained has a novel property that the elongation modulus, the heat shrinkage stress and the peak temperature of the heat shrinkage stress are high, and the heat shrinkage rate is small, for example, for papermaking machines. When used as an industrial cloth for over-clothing, rubber reinforcement, screen gauze, etc., the woven surface of the cloth can be easily heat-corrected, and the thermal dimensional stability is excellent, and at the time of using the cloth. It has the excellent effect of being able to maintain a stable woven surface without causing misalignment.

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

Examples 1 to 5 and Comparative Examples 1 to 12 Polyethylene terephthalate having an intrinsic viscosity of 0.71 (T301T manufactured by Toray Industries, Inc.) was subjected to a 40 mmφ extruder of Nippon Steel Co., Ltd., extruded from a nozzle at a spinning temperature of 290 ° C., and cooled in a water bath. By solidifying, 2150 denier undrawn yarn was obtained.

The unstretched yarn was subjected to the first stage drawing (using a hot water bath), the second stage drawing (using a dry heat bath) and the heat treatment (using a dry heat bath) under the conditions shown in Table 1 to obtain 390 denier drawn monofilaments. Obtained.

Table 1 also shows the measurement results of 3% elongation elastic modulus, maximum heat shrinkage stress and its peak temperature and 200 ° C. dry heat shrinkage rate for each monofilament.

When the first drawing temperature was 70 ° C (Comparative Example 10)
Was broken at a draw ratio of 4.5 times and could not be drawn.

When the first stage drawing temperature is 90 ° C and the drawing ratio is 5.3 times (Comparative Example 11), the 4th drawing temperature is 120 ° C and the total drawing ratio is
During the second-stage drawing of 5.8 times, the yarn was broken and it became impossible to draw.

Further, when the first stage stretching temperature is 90 ° C, the stretching ratio is 3.5 times, and the second stage stretching temperature is 100 ° C (Comparative Example 12).
Was broken at a total draw ratio of 5.8 times and could not be drawn.

As is clear from the results of Table-1, polyester monofilaments (No. 1 to 5) obtained by the method of the present invention
Has a novel property that the stretching elastic modulus, the heat shrinkage stress and the peak temperature of the heat shrinkage stress are high and the heat shrinkage rate is small.

(Effects of the Invention) As described above, the polyester monofilament of the present invention has novel characteristics that the elongation modulus, the heat shrinkage stress, and the peak temperature of the heat shrinkage stress are high and the heat shrinkage rate is small. For example, when it is used as an industrial cloth for a paper machine, over-clothing, rubber reinforcement, screen cloth, etc., the woven surface of the cloth can be heat-corrected and the thermal dimensional stability is excellent, and the cloth is excellent. It does not cause misalignment during use, and exhibits the excellent effect of being able to maintain a stable woven surface.

The polyester monofilament of the present invention having the above characteristics can be easily manufactured by an effective method in which two-stage drawing is performed at a relatively low temperature and then a fixed length treatment is performed at a relatively high temperature.

[Brief description of the drawings]

The drawing is a model diagram (graph) showing the state of development of the maximum shrinkage stress of the monofilament and its peak temperature.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-51-7280 (JP, A) JP-A-57-143551 (JP, A) JP-A-2-200137 (JP, A)

Claims (2)

(57) [Claims] 1. A monofilament made of polyester having an ethylene terephthalate unit content of 85% by weight or more and an intrinsic viscosity of 0.64 or more, the maximum point of heat shrinkage stress in the process of heating at a heating rate of 100 ° C./min. Is present at 200 ° C. or higher, and has the following characteristics, a polyester monofilament. Maximum heat shrinkage stress ≧ 0.25g / d 3% Elongation modulus ≧ 95% 200 ℃ Dry heat shrinkage ≦ 15% 2. A polyester containing 85% by weight or more of ethylene terephthalate units and having an intrinsic viscosity of 0.65 or more is melt-spun in a water bath, and the obtained undrawn yarn is heated at a temperature of 80 to 100 ° C.
It is drawn in one step at 3.5 to 5.0 times, then in two steps at a temperature of 110 to 140 ° C so that the total draw ratio becomes 5.0 to 5.8 times, and then 180
The method for producing a polyester monofilament having the characteristics according to claim (1), wherein the heat treatment is performed at a temperature of ˜260 ° C. under a substantially constant length of 0.98 to 1.05 times.