JPH11222722A - Polyester monofilament - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyester monofilament excellent in durability, hard to generate fibrillation or crazing even when used in a severe condition exposed to repeated dry heating and wet heating process such as a paper making dryer canvas while using original advantage of a naphthalate polyester. SOLUTION: This monofilament is obtained by melt spinning a naphthalate copolyester comprising a polyester at least including 85 mol.%. of ethylene-2,6- naphthalate units and containing 1-15 mol.%. of a diol expressed by formula I [(m) and (n) are same or different integers of 1-3, A is a 2-4C alkylene group, X is formula II or the like] based on the whole diol component, and the monofilament of 10>= denier manifests at least 70% retention of knot strength after wet heating treatment at 140 deg.C, and 100% RH for 60 hr.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a polyester monofilament, and more particularly, to a polyester monofilament having excellent durability even when used under conditions of wet heat treatment or dry heat treatment.
For example, the present invention relates to a polyester monofilament useful as a raw material for industrial materials such as a papermaking dryer canvas.

[0002]

2. Description of the Related Art Conventionally, polyester fibers have been used in various applications because of their excellent properties. In particular, polyester fibers used in industrial materials are subject to severe conditions under high temperature and high humidity due to their properties. Many are used under various conditions.

[0003] Above all, monofilaments used in dryer canvases, steel cleaning brushes and the like used in the drying process of papermaking are required to have sufficient durability under long-term use under high temperature and high humidity. However, polyesters, especially polyethylene terephthalate, are liable to decompose in a high-temperature atmosphere in which water is present, and the degree of polymerization is reduced, resulting in reduced fiber cutting strength and knot strength, and cannot withstand long-term use under high temperature and high humidity. There was a problem.

In order to solve this problem, various methods have been studied. For example, Japanese Patent Publication No. 47-1510
No. 4 discloses a method for reducing the carboxyl terminal concentration of polyethylene terephthalate by combining a copper carboxylate and a reducing anion. However, when the above-mentioned stabilizer is added, the polymer is colored in an undesired color tone and, under severe conditions of high temperature and high humidity, sufficient durability cannot always be obtained.

On the other hand, it is widely known that durability can be improved by using polyethylene naphthalate having a naphthalene ring in a molecular skeleton instead of polyethylene terephthalate. For example, polyethylene-2,6
For the naphthalate fiber, see JP-B-47-49769.
JP, JP-B-47-49770, JP-B-56-
No. 42682 discloses that the production of polyethylene naphthalate having excellent mechanical properties and thermal stability is specified by specifying the melt spinning conditions of polyethylene naphthalate.

[0006] Polyethylene-2,6-naphthalate fiber can have higher elastic modulus and tensile strength than polyethylene terephthalate fiber which has been widely used in the past, and has good wet heat resistance due to its high glass transition temperature. Are known. As a method for improving wet heat resistance, for example, a method of adding a carbodiimide compound (Japanese Patent Application Laid-Open No.
0-95517, JP-A-56-85704) and the like. However, in the above method, although hydrolysis resistance is improved, whitening, cracking and fibrillation at the time of bending specific to naphthalate polyester monofilaments proceed not only under wet heat but also under dry heat. I can't connect.

That is, since polyethylene-2,6-naphthalate fiber has a rigid molecular chain and a characteristic crystal structure, a bent portion of a monofilament having a denier of 10 denier or more is whitened when a knot is formed. There is a problem that fibrillation and cracking progress from the result, and as a result, the knot strength and the hook strength decrease, and both the bending fatigue durability under wet heat and dry heat and the mechanical properties such as the knot strength and the hook strength are satisfied. A monofilament has been longing.

The inventors of the present invention have investigated the causes of whitening, fibrils and cracks at the time of bending, which are phenomena specific to naphthalate polyester monofilaments.
It was found that the cause was fiber breakage due to compression deformation in the fiber axis direction. Since naphthalate polyester has its unique crystal structure, the fiber structure cannot be sufficiently relaxed against compressive stress, resulting in structural destruction, whitening, fibrillation, and cracking of the fiber, resulting in reduced durability. As a means to prevent them, it is necessary to have flexibility that is seemingly incompatible with high strength and high modulus. The present inventors have conducted intensive research on this problem and have reached the present invention.

That is, by copolymerizing a diol component having a specific structure with a polymer having ethylene-2,6-naphthalate as a main component, flexibility is imparted to a monofilament made of the polymer. As a method for imparting flexibility, there are many types of dicarboxylic acids or diols as the third component.However, in their copolymerization, the high glass transition temperature, one of the advantages of naphthalate polyester, is impaired, resulting in high temperature and wet heat. Inferior in durability.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and to carry out dry heat treatment and wet heat treatment such as a papermaking dryer canvas while taking advantage of the inherent advantages of naphthalate-based polyester. It is an object of the present invention to provide a polyester monofilament having excellent durability even in applications used under repeated severe conditions.

[0011]

According to the studies made by the present inventors, the object of the present invention is to provide at least 85 mol% of ethylene-2,6-naphthalate units per total recurring unit and all diols. It has been found that 1 to 15 mol% of the component is achieved by a polyester monofilament characterized by being formed from a copolymerized naphthalate polyester containing a diol component represented by the general formula (1) as a copolymerization component. .

[0012]

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Wherein, in the formula, m and n are the same or different and each represent an integer of 1 to 3, and A has 2 to 2 carbon atoms.
4 represents an alkylene group, and X represents

[0014]

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Is shown. ]

Hereinafter, the present invention will be described in more detail. The copolymerized naphthalate polyester of the present invention can be produced according to the means and conditions for producing ordinary polyesters, particularly polyethylene-2,6-naphthalate. That is, polyethylene-2,6-naphthalate is synthesized by polymerizing naphthalene-2,6-dicarboxylic acid or a functional derivative thereof (for example, a lower alkyl ester) and ethylene glycol under appropriate reaction conditions in the presence of a catalyst. Is done. In this case, the desired copolymerized naphthalate polyester can be obtained by adding a predetermined amount of the diol component represented by the formula (1) before the completion of the polymerization of polyethylene-2,6-naphthalate. Also,
The polyester used in the present invention may be one obtained by copolymerizing a known third component. Here, as the main third component, there are a dicarboxylic acid component such as terephthalic acid and isophthalic acid, and a diol component such as polyethylene glycol and 1,4-cyclohexanediol, but other known components can be used arbitrarily.

The copolymer naphthalate polyester may further contain an additive usually added to the polyester fiber.
For example, titanium oxide, silicon oxide, calcium carbonate, inorganic particles such as talc, conventionally known stabilizers, ultraviolet absorbers,
Various agents such as antioxidants, antistatic agents, pigments, waxes, silicone oils, and surfactants may be added. Further, a polyester, polyamide, polyetherester, polyurethane, polycarbonate, polyarylate, fluororesin, or the like other than the above-mentioned polyester may be blended in a small proportion as required.

In the diol represented by the general formula (1) used as the copolymerization component of the present invention, m and n are the same or different and each represent an integer of 1 to 3, preferably 1 or 2. When m or n exceeds 3, the properties of high strength, high modulus, and high glass transition temperature characteristic of naphthalate polyester are impaired. A is preferably an alkylene group having 2 carbon atoms (ethylene group). X is

[0019]

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Where X is

[0021]

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Are preferred, especially

[0023]

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Is preferred.

The diol represented by the general formula (1) is
1 to 15 mol%, preferably 2 mol%, based on all diol components
-10 mol%, particularly preferably 3-7 mol%. If it is less than 1 mol%, the effect of copolymerization is not exhibited, and if it exceeds 15 mol%, the advantages of naphthalate polyester such as a decrease in monofilament strength are impaired, which is not preferable.

The intrinsic viscosity of the copolymerized naphthalate polyester of the present invention is from 0.45 to 1.5, preferably from 0.55 to 1.5.
Use five. The intrinsic viscosity referred to herein is a value measured at a temperature of 35 ° C. using orthochlorophenol as a solvent. If the intrinsic viscosity is less than 0.45, not only the mechanical properties are reduced, but also the durability in wet heat and dry heat treatment is significantly reduced. On the other hand, in the case of a polymer having a high degree of polymerization having an intrinsic viscosity of more than 1.5, the melt viscosity becomes high, the fluidity is poor, and it is difficult to spin a uniform yarn.

The polyester monofilament of the present invention can be obtained by melt-spinning the above-mentioned copolymerized naphthalate polyester by a conventional method, stretching and, if necessary, heat-treating.

Also, by adding a carboxyl group terminal blocking agent such as a carbodiimide compound during melt spinning,
This is more preferable because the decrease in the intrinsic viscosity can be suppressed and the durability can be improved. The number of holes in the melt spinneret may be one, but it is more efficient to simultaneously discharge and separate the fibers in 2 to 4 holes and wind them up.
Moreover, the intrinsic viscosity of the spun yarn is less likely to decrease.

The monofilament has a circular cross section,
A cross-sectional shape such as a triangle, a square, and a polygon can be appropriately selected as needed. The diameter of the cross section can also be appropriately set according to the application, but in the case of a fiber diameter of less than 10 denier, the problem of whitening and fibril of the knot portion does not occur even without copolymerizing the diol component at 140 ° C. The knot strength retention after the heat treatment for 60 hours at 100% RH can be secured to 70% or more. On the other hand, a monofilament of 10 denier or more has high strength, but when used for papermaking such as a dryer canvas, the knot strength retention rate after wet heat treatment at 140 ° C. and 100% RH for 60 hours is 70% or more. Is required. When the knot strength retention rate of the polyester monofilament of 10 denier or more is less than 70%, the use greatly reduces the durability, and the object of the present invention cannot be achieved.

Here, the strength retention is a value calculated from the knot strength before and after the polyester monofilament is subjected to a wet heat treatment in an autoclave at 140 ° C. for 60 hours. In addition, the monofilament of the present invention is generally 10 to 13,
000 denier, preferably in the range of 400 to 10,000 denier.

[0031]

EXAMPLES The present invention will be described below more specifically with reference to examples. In addition, each characteristic value in an Example and a comparative example was measured by the following method. (1) Tensile strength, knot strength and hook strength Measured according to JIS L1013 at a sample length of 20 cm and an elongation rate of 100% / min. (2) Wet heat knot strength retention rate The polyester monofilament was treated in an autoclave filled with saturated steam at a temperature of 140 ° C. for 60 hours, and the knot strength of the treated monofilament was divided by the knot strength before treatment and calculated as 100 times. . (3) Moist heat durability The polyester monofilament is treated in an autoclave filled with saturated steam at a temperature of 140 ° C. for 60 hours, and the treated monofilament is gripped at a pressure of 3 kg / cm 2.
Was used to measure the occurrence of pinch cracks in the chuck. In addition, the case where cracks did not occur was represented by ○, the case where the occurrence of cracks was suppressed by protecting the grip portion with a cushioning material was suppressed, and the case where cracks could not be suppressed was represented by X.

Example 1 A copolymerized naphthalate polyester having an intrinsic viscosity of 0.97 and having a pore size of 2.5 and containing 5 mol% of a diol component represented by the following formula and having a principal component of ethylene-2,6-naphthalate: 2.5
mm from a single-hole spinneret having a circular shape of 30 mm.
It was melt spun at 5 ° C. and wound up at 54 m. The obtained undrawn yarn is supplied to a drawing heat treatment apparatus equipped with a supply roller, a drawing roller, and a take-up roller, and a non-contact heater between the rollers, and is drawn 4.5 times at 240 ° C. and heat set. went. Table 1 shows the physical properties of the obtained monofilament.

[0033]

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Example 2 A copolymerized naphthalate polyester having an intrinsic viscosity of 0.97 containing 5 mol% of a diol component represented by the following formula and having a main component of ethylene-2,6-naphthalate was prepared.
Spinning and stretching were performed in the same manner as in the above. Table 1 shows the physical properties of the obtained monofilament.

[0035]

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Comparative Example 1 An ethylene-2,6-naphthalate having an intrinsic viscosity of 0.5.
The polyester of 62 was run as in Examples 1 and 2. Table 1 shows the physical properties of the obtained monofilament.

Comparative Example 2 An ethylene-2,6-naphthalate having an intrinsic viscosity of 0.3.
Polyester 97 was run as in Examples 1 and 2. Table 1 shows the physical properties of the obtained monofilament.

Comparative Example 3 A copolymerized naphthalate polyester having a main component of ethylene-2,6-naphthalate and containing 3 mol% of phthalic anhydride as a dicarboxylic acid component and having an intrinsic viscosity of 0.97 was prepared as in Examples 1 and 2. The same was done. Table 1 shows the physical properties of the obtained monofilament.

Example 3 For the same polyester as used in Example 1,
A chip blend of 1.8% by weight of a carbodiimide compound (STABAXOL P100, manufactured by Bayer Corp.) is performed, spun in the same manner as in Example 1, and stretched 4.4 times using the same stretching apparatus as in Example 1. went. Table 1 shows the physical properties of the obtained monofilament.

Comparative Example 4 The same polyester as that used in Comparative Example 2 was used.
1.8% by weight of carbodiimide compound (STABAXOL P100 manufactured by Bayer K.K.) as in Example 3.
Was subjected to chip blending, and spun and drawn in the same manner as in Example 1.

[0041]

[Table 1]

[0042]

As described above, the monofilament of the present invention uses a naphthalate polyester obtained by copolymerizing ethylene-2,6-naphthalate with the diol component represented by the above formula. Orientation crystallization can be suppressed. Therefore, even if dry heat treatment or wet heat treatment is repeated, embrittlement due to stress in the direction perpendicular to the fiber axis accompanying crystallization acceleration is suppressed, and even if the monofilament is bent, whitening, fibrillation and cracking are unlikely to occur, and tensile The retention rate of the knot strength in addition to the strength is increased, and the durability is remarkably improved.

Claims (3)

[Claims] (1) Ethylene-2,6-
Naphthalate units are at least 85 mol%, and 1 to 15 mol% of all diol components are formed from a copolymerized naphthalate polyester containing a diol component represented by the following general formula (1) as a copolymerization component. Polyester monofilament. Embedded image Wherein m and n are the same or different and each represent an integer of 1 to 3, A represents an alkylene group having 2 to 4 carbon atoms, and X represents Is shown. ] 2. The copolymerized naphthalate polyester according to claim 1,
The polyester monofilament according to claim 1, which has an intrinsic viscosity of 0.45 to 1.5. 3. A monofilament having a fineness of 10 denier or more at 140 ° C. and 100% RH.
The polyester monofilament according to claim 1, having a knot strength retention of 70% or more after moist heat treatment for a long time.