JPH07118923A - Polyamide monofilament and production thereof - Google Patents

Abstract

PURPOSE:To obtain the polyamide filament which satisfies specific physical properties and has a high tensile strength and loop tenacity by making a polyamide copolymer from specific carboxylic acid and hexamethylenediamine into fibers under the specified melt extrusion and drawing conditions. CONSTITUTION:A polyamide copolymer which is produced by copolymerization of terephthalic acid, isophthalic acid and adipic acid with hexamethylenediamine has the recurring structural units of formula I to formula III (R is C6 straight- chain aliphatic hydrocarbon group). The copolymerization ratios of formula I to III are 60 to 70 mole %, 20 to 30 mole % and less than 15 mole % respectively. This copolymer is melt-extruded through a single-orifice spinneret at a temperature lower than the melting point of the polymer at a pack pressure over 70kg/cm<2>. The extruded filament is cooled in a hot bath kept over 90 deg.C and taken up at a rate of 10 to 50m/min. After being taken up, it is tentatively wound up and drawn or continuously drawn without winding at 200 to 230 deg.C at a drawing ratio over 3.2, and heat-set over the drawing temperature at a rate of 0.95 to 1.15 to give the monofilament having over 1.5g/d of tensile strength, over 2.5g/d of loop strength, and over 3g/d of knot strength.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a dryer canvas,
The present invention relates to a polyamide monofilament having excellent wet heat durability, which is useful as a brush for cleaning steel and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, polyamide monofilaments such as nylon 66 are often used in dryer canvases and brushes for washing steel, but they have the drawback of being inferior in durability such as moist heat resistance and acid resistance.

In order to improve such drawbacks, for example, Japanese Patent Publication No. 19809/1989 discloses a polyamide copolymer using an aromatic dicarboxylic acid such as terephthalic acid and isophthalic acid as an acid component.

However, since the polymer has a high crystallinity and the fluidity of the polymer is poor, it can be used as a resin for injection molding, but it is extremely difficult to obtain a monofilament having high strength by melt spinning. was there.

In order to improve such a drawback, for example, Japanese Patent Publication No. 3-56576 discloses a polyamide copolymer in which a part of aromatic dicarboxylic acid is replaced with adipic acid to improve the fluidity. It has been shown that polymers can be used to obtain polyamide monofilaments with high tenacity.

However, the above-mentioned polyamide monofilament merely shows an example in which the polymer fluidity is improved by lowering the crystallinity of the polymer, and the fiber can be formed, and it is used for a dryer canvas or a steel cleaning brush. At this time, no mention is made of a polyamide monofilament having high hooking strength, knot strength, and resistance to deterioration under hot and humid conditions and acid.

In particular, recent dryer canvases and brushes for washing steel have come to be used in more severe environments, and there is an increasing demand for improving the durability of constituent materials. Instead, it has been earnestly desired to develop a polyamide monofilament in which the microstructure of the fiber is changed by optimizing the spinning conditions to improve the durability against deformation and deterioration under heating.

[0008]

DISCLOSURE OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, to have high tensile strength, hooking strength and knot strength, and to improve wet heat durability. Another object of the present invention is to provide a polyamide monofilament suitable for an iron and steel cleaning brush and a method for producing the same.

[0009]

Means for Solving the Problems As a result of intensive studies for achieving the above object, the present inventors have melt-spun a crystalline polyamide copolymer formed from terephthalic acid, isophthalic acid, adipic acid and an aliphatic diamine. When adopting the spinning and drawing conditions that increase the denseness of the surface structure of the fiber, it has high tensile strength, hooking strength and knot strength due to the synergistic effect of the surface structure and the polymer composition, and the wet heat It was determined that a polyamide monofilament with improved durability can be obtained.

Thus, according to the present invention, the following (1)-
A polyamide monofilament comprising a polyamide copolymer having the repeating structural unit (3) and satisfying the following (a) to (d) is provided. (A) Tensile strength of 3.5 g / denier or more (b) Hooking strength of 2.5 g / denier or more (c) Knot strength of 3.0 g / denier or more (d) Strength retention after heat treatment at 140 ° C. for 100 hours 70% or more

According to the present invention, the following (a) to (c)
There is provided a method for producing a polyamide monofilament, which comprises sequentially including the steps of. (A) A polyamide copolymer having the following repeating structural units (1) to (3) is melted and discharged from a single-hole spinneret set at a temperature not higher than the melting point of the polymer at a pack pressure of 70 kg / cm ² or higher. Then, (a) the discharged yarn is cooled in a heating bath at 90 ° C. or higher, taken up at a speed of 10 to 50 m / min, and then once wound or continuously supplied to the drawing process without being wound. , (C) at a temperature of 200 to 230 ° C., 3.
After stretching by a factor of 2 or more, a heat treatment of 0.95 to 1.15 times is subsequently performed at a temperature equal to or higher than the stretching temperature.

[0012]

[Chemical 7]

[0013]

[Chemical 8]

[0014]

[Chemical 9]

(In the formula, the copolymerization ratios of (1) to (3) are 60 to 70 mol% of (1), 20 to 30 mol% of (2), and 15 mol% or less of (3), R is a linear aliphatic hydrocarbon group consisting of 6 carbon atoms.)

The polyamide copolymer used in the present invention is a polyamide formed from terephthalic acid, isophthalic acid and adipic acid and hexamethylenediamine, and a small amount of a stabilizer within a range not impairing the object of the present invention,
It may contain a modifier, a matting agent, a coloring agent and the like.

The polyamide copolymer is generally synthesized by copolymerizing terephthalic acid, isophthalic acid and adipic acid or a functional derivative thereof in the presence of a catalyst under suitable reaction conditions.

The polyamide copolymer has the following (1) to
It has a repeating structural unit of (3), and its copolymerization ratio is
It is necessary that (1) is 60 to 70 mol%, (2) is 20 to 30 mol%, and (3) is 15 mol% or less.

[0019]

[Chemical 10]

[0020]

[Chemical 11]

[0021]

[Chemical 12]

R in the above formula represents a straight-chain aliphatic hydrocarbon group having 6 carbon atoms.

Here, when the ratio of (1) exceeds 70 mol% or when the ratio of (2) is less than 20 mol%, the crystallinity is too high and spinning becomes difficult, while the ratio of (1) is When it is less than 60 mol% or when the ratio of (2) exceeds 30 mol%, mechanical properties such as tensile strength and abrasion resistance and wet heat durability are deteriorated.

Further, in the above polyamide copolymer, since the decomposition initiation temperature of the polymer is lower than the melting point, it is necessary to add (3) to lower the melting point, but when it exceeds 15 mol%, the wet heat durability is deteriorated. To do.

However, if the amount of (3) is too small, the molecular chain becomes rigid and the values of hooking strength and knot strength decrease, and decomposition during melting tends to occur. Is preferred.

The preferred melting point range of the above polyamide copolymer is 305 to 320.degree.

The polyamide monofilament of the present invention is
The above polyamide copolymer can be obtained by sequentially using the following steps. The polyamide copolymer is melted, discharged at a pack pressure of 70 kg / cm ² or more from a single-hole spinneret set to a temperature not higher than the melting point of the polymer, and the discharged yarn is cooled in a heating bath at 90 ° C. or higher, 10-5
After being drawn at a speed of 0 m / min, it is once wound or continuously supplied to the drawing step without being wound, and drawn 3.2 times or more at a temperature of 200 to 230 ° C. and then continuously drawn at the drawing temperature or more. Temperature of 0.95 to 1.15
Double heat treatment.

At this time, the pack pressure during melt spinning is 70 k.
If it is less than g / cm ² , the polymer is decomposed and spinning becomes difficult. However, if the pack pressure becomes too high, the spinning condition will be poor, so it is preferable to stop the pressure at about 160 kg / cm ² .

Further, in obtaining the polyamide monofilament of the present invention, it is most important to set the die temperature to the melting point or lower.

When the spinneret temperature exceeds the melting point, the polymer is likely to be decomposed, voids are generated, foreign matter is attached to the spinneret, and spinning is difficult.
Nodule strength cannot be obtained. A more preferable range of the die temperature is (melting point-2 ° C) to (melting point-15 ° C).

Further, a heating cylinder may be provided immediately below the base to perform delayed cooling.

The spun yarn is then cooled in a heating bath above 90 ° C. and taken up at a speed of 10 to 50 m / min. As the heating medium for the heating bath, any medium such as hot water or silicon oil can be used. However, if the temperature of the heating bath is lower than 90 ° C., the cooling is too fast and the cross-sectional shape of the monofilament becomes uneven.

However, if the cooling temperature is too high, the crystallization of the monofilament will proceed and the drawability will be poor.
It is preferable to stop at about 120 ° C.

When the spinning take-up speed is less than 10 m / min, the structure of the obtained monofilament becomes loose and the wet heat durability is deteriorated. On the other hand, when it exceeds 50 m / min, the elongation is too low. The hooking strength and knot strength decrease.

The above undrawn yarn is wound once after spinning, or is continuously fed to the drawing process without being wound,
After being stretched 3.2 times or more at ˜230 ° C., it is subsequently heat treated at a temperature not lower than the stretching temperature.

The heat treatment may be carried out in any state of relaxation, constant length and tension depending on the characteristics of the obtained monofilament, and the elongation rate thereof is required to be 0.95 to 1.15 times. is there.

If the stretching temperature is less than 200 ° C., sufficient strength cannot be obtained, while if it exceeds 230 ° C., the hooking strength, knot strength or wet heat resistance deteriorates.

When the draw ratio is less than 3.2 times,
The molecular orientation is insufficient and the tensile strength decreases. However, if the draw ratio is too high, yarn breakage will occur, so it is preferable to stop at about 3.5 times.

The effect of the heat treatment is not fully exhibited unless it is carried out at a temperature higher than the drawing temperature, but if it is too high, yarn breakage occurs, so it is preferable to stop the heat treatment at about 260 ° C.

When the elongation percentage during heat treatment exceeds 1.15 times, the elongation is lowered and the hooking strength and knot strength are lowered. On the other hand, when the elongation is less than 0.95 times, the monofilament becomes brittle.

The cross-sectional shape and fineness of the monofilament are not particularly limited and may be appropriately set according to the intended use. However, when the monofilament is used for a dryer canvas or a steel cleaning brush, the fineness is 100 to 10,000 denier. A circular cross section is preferred.

The polyamide monofilament thus obtained has a tensile strength of 3.5 g / denier or more and a hooking strength of 2.5 g / denier or more and a knot strength of 3.0.
It must be g / denier or more.

When the tensile strength is less than 3.5 g / denier or the hooking strength is less than 2.5 g / denier, or the knot strength is less than 3.0 g / denier, it is used for applications such as dryer canvas and steel washing brushes. I can't.

That is, in the dryer canvas,
Polyamide monofilament is formed into a sheet in the form of woven or knitted fabric or knotted net, and is subject to tensile and bending deformation during use,
Tensile strength less than 3.5 g / denier or hooking strength less than 2.5 g / denier or knot strength 3.0 g /
If it is less than denier, the monofilament breaks.

Further, in the case of the steel cleaning brush, since it undergoes bending deformation while being exposed to the heated cleaning liquid,
After all, the above strength is required.

Furthermore, the polyamide monofilament has a strength retention of 7 after moist heat treatment at 140 ° C. for 100 hours.
It must be 0% or more.

Here, the strength retention is a value calculated from the tensile strength before and after the polyamide monofilament is heat-moisture treated in an autoclave at 140 ° C. for 100 hours,
It is a value that is an index of wet heat durability.

When the strength retention rate is less than 70%, the durability of the composition is greatly deteriorated when it is used for a dryer canvas, a steel cleaning brush, etc., and the object of the present invention cannot be achieved.

[0049]

In the present invention, when the polyamide copolymer containing terephthalic acid and isophthalic acid as the main acid components is melt-spun, the thermal decomposition of the polymer is minimized by specifying the pack pressure and the die temperature. Since the cooling condition and the drawing condition after discharging are optimized to improve the uniformity of the cross-sectional shape and the denseness of the fiber surface, a polyamide monofilament having high hooking strength and knot strength can be obtained.

Further, the polyamide monofilament of the present invention is much more excellent in wet heat durability than the polyamide monofilament disclosed in Japanese Patent Publication No. 3-56576.

Although the details of the reason are not clear, in the polyamide monofilament of the present invention, the spinneret temperature during melt spinning is kept below the melting point of the polymer to minimize thermal decomposition of the polymer and to lower the stretching temperature as much as possible. It is presumed that this is probably because the molecules are densely arranged and then heat-treated, so that they have high crystallinity and a dense fiber structure.

On the other hand, the above-mentioned Japanese Patent Publication No. 3-5657.
The polyamide monofilament disclosed in Japanese Patent No. 6 is
Since the polymer is melted at a temperature equal to or higher than the melting point, it is considered that the thermal decomposition of the polymer is progressing, the uniformity of the cross-sectional shape and the denseness of the fiber surface are low, and the wet heat durability is poor.

Hereinafter, the present invention will be described in more detail with reference to examples. The physical property values in Examples and Comparative Examples are
It was measured by the following method.

(1) Tensile strength, hooking strength, knot strength According to JIS L 1013, sample length 20c
m, elongation rate 100% / min.

(2) Wet heat durability The polyamide monofilament was expressed by the retention rate of the tensile strength before and after being treated for 100 hours in saturated steam at 140 ° C. using an autoclave.

[0056]

Example 1 A molar ratio of terephthalic acid, isophthalic acid, adipic acid and hexamethylenediamine of 65:25:
10: 100 polyamide copolymer (melting point 315 ° C)
From a single-hole spinneret having a circular shape with a hole diameter of 2.0 mm to a spinneret temperature of 310 ° C., a pack pressure of 130 kg / cm ² ,
It was discharged at a discharge rate of 25.9 g / min, cooled in a warm water bath at 92 ° C., and then wound at a spinning speed of 37 m / min.

The unstretched yarn obtained was fed to a stretching heat treatment apparatus provided with a non-contact type heater between a feeding roller, a stretching roller and a winding roller and each roller, and after stretching at a temperature of 210 ° C. by 3.4 times. A heat treatment of 0.97 times was performed at 240 ° C.

Table 2 shows the physical properties of the obtained polyamide monofilament.

[0059]

Comparative Examples 1 to 4 In Example 1, melt spinning condition table 1
The same procedure as in Example 1 was carried out except that the changes were made as shown in FIG.
Table 2 shows the physical properties of the obtained polyamide monofilament.

[0060]

Example 2 and Comparative Examples 5 to 6 The procedure of Example 1 was repeated, except that the stretching heat treatment conditions were changed as shown in Table 1. Table 2 shows the physical properties of the obtained polyamide monofilament.

[0061]

Third Embodiment In the first embodiment, the discharge amount is 20.6 g /
Min, the spinning speed was 43 m / min, and the drawing heat treatment conditions were shown in Table 1.
The same procedure as in Example 1 was carried out except that the changes were made as shown in FIG.
Table 2 shows the physical properties of the obtained polyamide monofilament.

[0062]

Examples 4 and 5 and Comparative Examples 7 to 9 Example 3 is the same as Example 3 except that the stretching heat treatment conditions are changed as shown in Table 1.
It carried out similarly to. Table 2 shows the physical properties of the obtained polyamide monofilament.

[0063]

Example 6 The procedure of Example 1 was repeated, except that the circular single-hole spinneret had a hole diameter of 2.5 mm and the spinning and drawing heat treatment conditions were changed as shown in Table 1. Table 2 shows the physical properties of the obtained polyamide monofilament.

[0064]

Example 7 In Example 1, the polyamide copolymer terephthalic acid, isophthalic acid, adipic acid and hexamethylenediamine were mixed at a molar ratio of 65: 30: 5: 100.
(Melting point 318 ° C.) and the spinning and drawing heat treatment conditions were changed as shown in Table 1, and the same procedure as in Example 1 was performed. Table 2 shows the physical properties of the obtained polyamide monofilament.
Shown in.

[0065]

[Table 1]

[0066]

[Table 2]

As is clear from Tables 1 and 2, the polyamide monofilament of the present invention has a tensile strength of 3.5 g / d or more, a hooking strength of 2.5 g / d or more and 3.0 g / d.
It has a knot strength of d or more, and has a strength retention of 70% or more after heat treatment at 140 ° C. for 100 hours.

[0068]

According to the present invention, it is possible to obtain a polyamide monofilament having high tensile strength, hooking strength, knot strength, and improved wet heat resistance, which is suitable for a dryer canvas or a steel cleaning brush.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area // D01F 6/84 301 E 7199-3B D21F 7/08 A 7199-3B

Claims (2)

[Claims] 1. A polyamide copolymer having repeating structural units of the following (1) to (3), which comprises:
A polyamide monofilament satisfying the condition (d). (A) Tensile strength of 3.5 g / denier or more (b) Hooking strength of 2.5 g / denier or more (c) Knot strength of 3.0 g / denier or more (d) Strength retention after heat treatment at 140 ° C. for 100 hours The rate is 70% or more. [Chemical 2] [Chemical 3] (In the formula, the copolymerization ratio of (1) to (3) is 60 to (1).
70 mol%, (2) 20 to 30 mol%, (3) 15
It is not more than mol%, and R is a straight-chain aliphatic hydrocarbon group having 6 carbon atoms. ) 2. A method for producing a polyamide monofilament, which comprises sequentially including the following steps (a) to (c) when producing the polyamide monofilament according to claim 1. (A) A polyamide copolymer having the following repeating structural units (1) to (3) is melted and discharged from a single-hole spinneret set at a temperature not higher than the melting point of the polymer at a pack pressure of 70 kg / cm ² or higher. (A) Cool the discharged yarn in a heating bath at 90 ° C. or higher,
After being drawn at a speed of ˜50 m / min, it is once wound or continuously supplied to the drawing step without being wound, and (c) after being drawn 3.2 times or more at a temperature of 200 to 230 ° C., Then, at a temperature equal to or higher than the stretching temperature, 0.95 to 1.1
Heat treatment of 5 times is performed. [Chemical 4] [Chemical 5] [Chemical 6] (In the formula, the copolymerization ratio of (1) to (3) is 60 to (1).
70 mol%, (2) 20 to 30 mol%, (3) 15
It is not more than mol%, and R is a straight-chain aliphatic hydrocarbon group having 6 carbon atoms. )