JPH04300320A - High-strength polyester monofilament and its production - Google Patents

Abstract

PURPOSE:To provide polyester monofilament, excellent in tensile strength, knot strength, loop strength, etc., and good in even adhesion to rubber. CONSTITUTION:High-strength polyester monofilament is obtained by extruding a polyester having >=0.8 intrinsic viscosity through a spinning hole of a special shape, spinning the monofilament under specific quenching conditions, providing undrawn monofilament having >=350% natural draw ratio, drawing the resultant undrawn monofilament in a hot water bath at 85-95 deg.C in the first stage, subsequently drawing the prepared monofilament at 180-280 deg.C in an atmosphere of a gas in the second stage and then heat-treating the drawn monofilament at 200-280 deg.C at a constant length or under conditions of restricted shrinkage. Since the aforementioned monofilament has characteristics of plural uneven parts present on the outer periphery of the fiber cross section, >=7.5g/de tensile strength, >=4.0g/de knot strength and >=3.0g/de loop strength, the monofilament is extremely suitable as monofilament for reinforcing rubber.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to high strength polyester monofilaments useful for industrial material applications, particularly as rubber reinforcing materials. More specifically, the present invention relates to a polyester monofilament having excellent mechanical properties such as tensile strength, knot strength, and hooking strength, and improved adhesion to rubber, and a method for producing the same.

0002

[Prior Art] Polyester monofilaments, typically polyethylene terephthalate, have mechanical properties such as
In particular, it has properties such as high strength and high elasticity, so it is widely used in various industrial materials, and is frequently used as fishing lines, guts, fishing nets, brushes, etc. In addition, in recent years, attempts have been made to use it as a rubber reinforcing material for tires, power transmission belts, conveyor belts, and the like.

[0003] Conventionally, multifilaments such as polyester, polyamide, and rayon have been widely used as rubber reinforcing materials. There was a limit to the ability to fully utilize the properties of filaments, such as high strength and high elasticity. In order to solve this problem, Japanese Patent Laid-Open No. 1-148828 proposes the use of polyamide monofilament as a carcass cord for radial tires. By using monofilament, high strength and high elasticity can be achieved, and the cord It is also disclosed that the amount of rubber used can be reduced by 20 to 40%, and that the heat generated during running of the tire can also be reduced.

However, although high strength monofilaments of 9.5 g/de or more have been proposed for polyamide monofilaments, monofilaments of 500 denier or more have a strength of 7.5 g/de or more and a knot strength of 4 g.
There is no known monofilament with high strength and durability such as /de or more and hooking strength of 3g/de or more. For example, Japanese Patent Publication No. 47-9224 describes that a monofilament with improved knot strength can be obtained by drawing under specific drawing conditions, but this material still has a low strength of 5 g/de. there were. Even if such polyester monofilament is used as a rubber reinforcing material,
There are problems such as insufficient durability and low reinforcing effect, and a monofilament with high strength and excellent properties such as knot strength and hooking strength has been desired.

[0005] Furthermore, polyester monofilaments have fewer functional groups with large hydrogen bonding abilities in their molecular chains than polyamides, and monofilaments have a smaller adhesive area with rubber than multifilaments. Since the adhesion with the adhesive is insufficient, it has been necessary to improve the adhesion as well as the strength.

[0006]

OBJECTS OF THE INVENTION The present invention has been made in view of the problems of the above-mentioned prior art, and its purpose is to improve the properties of the industry in which excellent properties such as knot strength and hook strength are required as well as tensile strength. The object of the present invention is to provide a monofilament that is suitable for various uses and has improved adhesion to rubber, and is particularly suitable for reinforcing rubber.

[0007]

[Structure of the Invention] As a result of intensive studies to achieve the above object, the present inventors surprisingly found that a monofilament having a specific cross-sectional shape has extremely good spinability.
The present invention was achieved based on the discovery that a monofilament with high strength and excellent knot strength and hooking strength can be easily obtained.

That is, the present invention provides (1) a monofilament made of polyester containing 75% or more of ethylene terephthalate units, in which a plurality of uneven portions are present on the outer periphery of the cross section of the monofilament, and the fineness is 5.
00 denier or more, tensile strength is 7.5 g/de or more, knot strength is 4.0 g/de or more, hooking strength is 3.0 g/d
A high-strength polyester monofilament characterized by having a strength of at least e, (2) 7 ethylene terephthalate units;
Polyester containing 5% or more and having an intrinsic viscosity of 0.8 or more,
It is melt-extruded from a nozzle having one main hole and a plurality of sub-holes, the main hole and the sub-holes partially overlapping and/or connected through slits, and is heated at 50 to 150°C. After passing through a heating cylinder, the undrawn monofilament is introduced into a coagulation bath at 70 to 95°C and cooled, and the undrawn monofilament with a natural draw ratio of 350% or more is taken out.
Stretched 2.5 to 3.5 times in a hot water bath, then 180
After stretching 2.0 to 3.5 times in a gas atmosphere at ~280°C, it is stretched by 1.0 to 0.0 times in a gas atmosphere at 200 to 280°C.
This is a method for producing a high-strength monofilament characterized by heat treatment for constant length or limited shrinkage of 9 times.

The contents and effects of each element constituting the present invention will be explained in detail below.

[0010] The polyester referred to in the present invention is primarily a polyester whose main repeating unit is ethylene terephthalate. In addition, a tertiary material may be used within the range that does not impair the excellent physical and chemical properties of polyethylene terephthalate.
It may also be a polyester obtained by copolymerizing the components. Examples of such copolymerization components include dicarboxylic acids such as isophthalic acid, naphthalene dicarboxylic acid, and diphenyldicarboxylic acid, as well as propylene glycol, butylene glycol,
A diol component such as diethylene glycol can be exemplified, and its copolymerization ratio is 25 mol% or less, preferably 10 mol% or less, based on the terephthalic acid component. The polyester may also contain additives such as stabilizers, plasticizers, matting agents, abrasives, lubricants, and flame retardants within the range that does not impede the object of the present invention.

It is important that the polyester monofilament of the present invention has a denier of 500 de or more and that a plurality of uneven portions are present on the outer periphery of the monofilament. By having such a cross-sectional shape, even if the monofilament is 500 de or more, as will be explained in detail later,
A monofilament with improved tensile strength, knot strength, and hooking strength can be obtained, and its adhesion to rubber is also improved.

Further, the polyester monofilament of the present invention has a tensile strength of 7.5 g/de or more and a knot strength of 4.0 g/de.
Since it has well-balanced properties such as g/de or more and hanging strength of 3.0 g/de or more, it is particularly suitable for rubber reinforcement.

The polyester monofilament of the present invention having the above characteristics can be produced by the following method. That is, a polyester having an intrinsic viscosity [η] of at least 0.8 or more, preferably 0.9 or more as measured with an orthochlorophenol solution at 35°C is melted by a conventional method, and one main pore and a plurality of sub-pores are formed. The main hole and the sub-hole partially overlap or are connected through a slit, for example, extrusion is carried out through an irregularly shaped nozzle illustrated in FIGS. 80-15
After passing through a heating cylinder heated to 0℃, the temperature is 70-95℃.
It is important to introduce the monofilament into a coagulation bath, cool it, and take out the monofilament with a natural draw ratio of 350% or more.

[0014] If the temperature of the heating cylinder is less than 50°C, a monofilament with high tensile strength and knot strength cannot be obtained; on the other hand, if it exceeds 150°C, the spinning tension will drop significantly and it will be difficult to take off the yarn. becomes. On the other hand, the coagulation bath temperature is 70℃
If it is less than 95°C, the cooling rate is too fast and contraction occurs rapidly, resulting in an irregular cross-sectional shape. Conversely, if it exceeds 95°C, the spinning tension decreases and it is difficult to take off. becomes. The lengths of the heating tube and the coagulation bath vary depending on the take-up speed of the undrawn yarn, and may be changed as appropriate within the range where the natural draw ratio is 350% or more.

Furthermore, if the natural stretching ratio of the obtained unstretched monofilament is less than 350%, it will be difficult to carry out the subsequent stretching within the scope of the present invention, and even if stretching is possible, the present invention will not be possible. This is not preferable because it becomes impossible to obtain a monofilament that simultaneously satisfies the various properties specified in (1).

[0016] Furthermore, it is assumed that this is due to the presence of a plurality of irregularities on the outer periphery of the cross section, but the yarn wobbling that occurs when the undrawn monofilament is taken up is also reduced, which improves the stability of the spinning process. There is also.

The undrawn yarn thus obtained is then subjected to two-step drawing treatment. The first stage of stretching is carried out at a relatively low temperature and low magnification, i.e. 2.5 to 3.5 in a hot water bath at 85 to 95°C.
It needs to be done under twice the conditions. If the drawing temperature is less than 75°C, not only will the yarn be likely to break during drawing, but a monofilament with high knot strength will not be obtained. On the other hand, if the temperature exceeds 85°C, the stretching tension is significantly reduced and stretching becomes difficult, which is not preferable.

Furthermore, if the stretching ratio is less than 2.5 times, stretching unevenness occurs and a uniform monofilament cannot be obtained.
On the other hand, if it exceeds 3.5 times, it is not preferable because the knot strength and hooking strength decrease.

In addition, in the case of a monofilament with no irregularities on the outer periphery of the cross section, the stretching zone tends to fluctuate in the hot water bath, so even when stretching at a low magnification of 2.5 to 3.5 times, the stretching zone does not extend outside the hot water bath. In contrast, the monofilament according to the present invention has irregularities on the outer periphery of the cross section, so that the stretching zone is stabilized and uniform stretching is possible.

Next, the second stage stretching conditions are set at a higher temperature than the first stage stretching, 180 to 280°C, preferably 220°C.
Stretching ratio 2.0 to 3.5 in a gas atmosphere at ~280°C
Execute twice. Similarly to the first stage of drawing, if the drawing temperature is low, below 180°C, a monofilament with high knot strength cannot be obtained; on the other hand, if it is low, below 280°C, tensile strength and knot strength This is not preferred because it is impossible to obtain a monofilament with high hooking strength. Furthermore, if the second stage draw ratio is low (less than 2.0 times), a monofilament with high tensile strength and knot strength cannot be obtained, and conversely, if it is too high (more than 3.5 times), the tensile strength is However, it is not possible to obtain a monofilament with high hook strength and knot strength.

The drawn monofilament is subsequently heat treated. This heat treatment is carried out in a gas atmosphere at 200-280°C, preferably above the second-stage stretching temperature and below 280°C, while causing constant or limited shrinkage to 1.0-0.9 times. If the heat treatment temperature is less than 200°C, the knot strength will decrease, and if it exceeds 280°C, the hooking strength and knot strength will decrease, which is preferable.

Furthermore, if the monofilament is stretched during heat treatment, the knot strength and hooking strength are significantly reduced, but even if the shrinkage treatment exceeds 10%, the monofilament sag is large and stable operation cannot be achieved. becomes difficult.

The gas atmosphere for the second-stage stretching and heat treatment may be air or an inert gas such as nitrogen, but air is usually sufficient. As the heating device, any one such as an air furnace, an inert gas furnace, an infrared furnace, a high frequency furnace, a metal furnace, etc. can be used.

The polyester monofilament of the present invention produced by the method described in detail above has an excellent balance between tensile strength and knot strength or hooking strength, and has unevenness on the surface of the monofilament. , can be applied to industrial applications such as rubber reinforcement,
The industrial value of the present invention is extremely large.

[0025]

[Examples] The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to the following embodiments unless it exceeds the spirit thereof.

[0026]

[Examples 1 to 13 and Comparative Examples 1 to 7] Intrinsic viscosity 1.0 (
Polyethylene terephthalate (measured with an orthochlorophenol solution at 35°C) was melted and extruded from the irregularly shaped nozzle shown in Figure 2(a) kept at 290°C, and passed through a heating cylinder under the conditions shown in Tables 1 and 2. After cooling and solidifying, first-stage stretching, second-stage stretching and heat treatment are performed, each with a
A monofilament of de was produced. Table 3 also shows the results of measuring the tensile strength, knot strength, and hooking strength of the obtained monofilament. Measurement of each of these physical properties is carried out by JI
It was performed according to the standard of SL1013.

[0027] When the temperature of the heating cylinder was 200°C, the monofilament tended to sag and was difficult to take off at a take-up speed of 30 m/min. In addition, the heat treatment temperature was increased to 1
If the heat treatment temperature is as low as 50°C, the yarn will sag during limited shrinkage heat treatment, causing uneven heat shrinkage.
Even when the temperature is as high as 0° C., if the limiting shrinkage rate exceeds 10%, the yarn becomes slack, making it difficult to implement.

As is clear from the results in Table 3, the polyester monofilaments obtained by the method of the present invention (Examples 1 to 13) are excellent in tensile strength, knot strength, and hooking strength in balance. On the other hand, polyester monofilaments obtained by methods other than the present invention (Comparative Examples 1 to 6) are inferior in at least one of the properties of tensile strength, knot strength, and hook strength.

Furthermore, a monofilament (Comparative Example 7) obtained by taking and drawing a spun yarn having no unevenness on the outer periphery of the cross section from the nozzle shown in FIG. 5(a) under the conditions shown in Table 1, Although the results were fair in terms of knotting, knotting and hooking strength, the yarn swayed significantly during spinning, and the necking point during the first stage drawing also fluctuated easily, resulting in extremely poor spinning properties.

[0030] Monofilament drawn yarn obtained in Examples 10, 11 and Comparative Example 7 and PET multifilament twisted yarn cord for tire cord (single yarn 6 denier, twist structure 1500 de/2, twisted yarn 40 x 40 T/10 cm; manufactured by Teijin) ) was treated with epoxy and dried at 130°C for 2 minutes, then
Heat treatment was performed at 0°C for 1 minute. The physical properties of the obtained treated cord are shown in Table 4.

Next, the treated cord was embedded in unvulcanized rubber mainly composed of natural rubber, and after vulcanization at 150° C. for 30 minutes, the pull-out adhesive strength T was measured. Table 4 also shows the results.

[0032] From this result, the monofilament having a plurality of irregularities on the outer periphery of the cross section (Examples 10 and 11) has extremely high adhesive strength compared to the monofilament having no irregularities (Comparative Example 7). It is clear that it exhibits adhesive strength equivalent to that of PET multifilament.

It is also clear that the polyester monofilament of the present invention has a higher modulus (represented by 6.75 kg intermediate elongation) compared to PET multifilament.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

[Table 4]

[0038]

[Table 5]

[0039]

[Table 6]

[0040]

[Table 7]

[0041]

[Effects of the Invention] As explained above, the polyester monofilament of the present invention has the characteristics of high strength, balanced knot strength, and hooking strength, and also has no unevenness on the surface. Since it has improved adhesion to rubber, it is highly effective as a rubber reinforcing material for tire cords, power transmission belts, conveyance belts, etc. Furthermore, since the monofilament of the present invention has the above-mentioned excellent characteristics, it can be applied to general industrial material applications, such as fishing lines, guts, and fishing nets.

Further, according to the production method of the present invention, it is possible to industrially advantageously obtain a polyester monofilament which has excellent spinnability and drawability, and therefore has high strength and excellent properties such as knot strength and hooking strength in a well-balanced manner. be able to.

[Brief explanation of drawings]

FIG. 1 (a) shows one example of a nozzle hole shape used in the present invention. (b) shows the cross-sectional shape of the monofilament of the present invention obtained from the nozzle hole in (a).

FIG. 2 (a) shows one example of the nozzle hole shape used in the present invention. (b) shows the cross-sectional shape of the monofilament of the present invention obtained from the nozzle hole in (a).

FIG. 3(a) shows one example of a nozzle hole shape used in the present invention. (b) shows the cross-sectional shape of the monofilament of the present invention obtained from the nozzle hole in (a).

FIG. 4(a) shows one example of a nozzle hole shape used in the present invention. (b) shows the cross-sectional shape of the monofilament of the present invention obtained from the nozzle hole in (a).

FIG. 5(a) shows an example of a nozzle hole shape used in a flat cross-section monofilament. (b) shows the cross-sectional shape of the flat cross-section monofilament obtained from the nozzle hole in (a).

Claims (2)

[Claims] Claim 1: A monofilament made of polyester containing 75% or more of ethylene terephthalate units, which has a plurality of irregularities on the outer periphery of the cross section, has a fineness of 500 deniers or more, and has a tensile strength of 7.5 g. /de or more, a knot strength of 4.0 g/de or more, and a hooking strength of 3.0 g/de or more. Claim 2: Polyester containing 75% or more of ethylene terephthalate units and having an intrinsic viscosity of 0.8 or more, having one main pore and a plurality of sub-pores, the main pores and the sub-pores being partially separated. It is melt-extruded from nozzles overlapping and/or connected through slits, passed through a heating cylinder at 50 to 150°C, and then introduced to a coagulation bath at 70 to 95°C and cooled to a natural stretching ratio of 350%. After taking the above undrawn monofilament, the undrawn monofilament is drawn 2.5 to 3.5 times in a hot water bath at 85 to 95°C, and then 180 to 280
After stretching 2.0 to 3.5 times in a gas atmosphere at ℃,
A method for producing a high-strength monofilament, characterized by subjecting it to heat treatment for fixed length or limited shrinkage to 1.0 to 0.9 times in a gas atmosphere at 00 to 280°C.