JP4214071B2 - Polyester fiber - Google Patents

Description

  The present invention is excellent in hydrolysis resistance, dry heat decomposition resistance, and construction of various industrial fabrics represented by paper fabric dryer canvas, belt fabric for thermal bonding process of nonwoven fabric and fabric for conveyor belt in heat treatment furnace. The present invention relates to a polyester fiber useful as a material.

  Polyester fiber has excellent physical properties, so it can be used as a constituent material for various industrial fabrics such as paper-made dryer canvas, belt fabric for thermal bonding process of nonwoven fabric, fabric for conveyor belt in heat treatment furnace, and woven fabric for tire cord. Have been widely used.

  However, when the polyester fiber is used as a constituent material of a paper-making dryer canvas, for example, when it is used under conditions that are easily hydrolyzed such as high temperature and high humidity, the polyester fiber causes a decrease in strength due to hydrolysis degradation during use. It was difficult to withstand long-term use.

  In order to improve the hydrolysis resistance, which is a drawback of such polyester fibers, various proposals have heretofore been made.

  For example, a polyester monofilament (for example, see Patent Document 1) to which a specific amount of polyolefin such as polyethylene, polypropylene, polybutene, poly-4-methylpentene 1, and polystyrene is added is known. A monofilament made of polyethylene terephthalate to which polyethylene is added has little effect on improving hydrolysis resistance and is not practical.

  Moreover, the method of improving the hydrolysis resistance of polyester by adding a carbodiimide compound is known. For example, a method of forming a filament not containing unreacted carbodiimide by adding a mono- or biscarbodiimide compound and kneading and spinning in a short time (see, for example, Patent Document 2), having 3 or more carbodiimide groups in the molecule A method of adding a polycarbodiimide compound (see, for example, Patent Document 3), wherein the carboxyl end group is capped by reaction with carbodiimide, and 30 to 200 ppm of free mono and / or biscarbodiimide compound and free polycarbodiimide or still reactive Polyester fibers and filaments containing at least 0.02% by weight of a reaction product containing polycarbodiimide groups are proposed (see, for example, Patent Document 4).

Furthermore, a method for producing an industrial polyester monofilament in which a specific carbodiimide compound is added to a polyester containing a specific amount of phosphorus (see, for example, Patent Document 5), the terminal carboxyl group concentration is 10 equivalents or 10 ⁶ g or less of polyester, Polyester monofilament containing 0.005 to 1.5% by weight of a carbodiimide compound in an unreacted state and 0.01 to 30% by weight of a fluorine-based polymer (see, for example, Patent Document 6), unreacted mono Polycarbodiimide compound (B) containing 230 ppm to 1.5% by weight of carbodiimide compound (A), partially reacting with carboxyl end groups of unreacted polycarbodiimide compound and / or polyester, and having unreacted carbodiimide groups Containing 0.05 to 1.5% by weight of polyester mono Iramento (e.g., see Patent Document 7), polymer component, terminal carboxyl group concentration of 10 99.8 to 60 wt% eq / 10 ⁶ g or less of the polyester (A), a thermoplastic polymer containing no fluorine atom (B ) Polyester monofilament comprising 0.2 to 40% by weight and containing 0.005 to 1.5% by weight of the carbodiimide compound (C) in which the polymer component is unreacted (for example, see Patent Document 8), syndiotactic A monofilament comprising a polyester composition containing a specific amount of polystyrene and an unreacted monocarbodiimide compound and polycarbodiimide compound such as a tic structure (see, for example, Patent Document 9), and an ethylene / acrylate copolymer and a carbodiimide Polyester monofilament with a specific amount of compound ( Eg to be proposed and Patent Document 10), various improvements have been made.

However, even polyester monofilaments that have been improved in hydrolysis resistance by the above-described methods are intended to be used as constituent materials for papermaking dryer canvas in applications that require dry pyrolysis resistance, for example, in processes where the drying temperature of the papermaking dryer is high. Used as a component material for papermaking dryer canvas used for papermaking dry parts where the drying temperature is higher than before for the purpose of increasing paper productivity and ears exposed to higher temperatures without contact with wet paper When trying to do so, not only the hydrolysis resistance is still insufficient, but also the problem that the dry heat decomposition resistance is insufficient is left, and the fact that an expensive PPS monofilament has been forced to be used It is.
Japanese Patent Application Laid-Open No. 51-136923 (pages 1 to 5) JP 50-95517 A (pages 1 to 4) Japanese Examined Patent Publication No. 38-15220 (pages 1-6) JP-A-4-289221 (pages 1-7) JP-A-57-205518 (pages 1 to 9) Republication International Publication No. WO 92/07126 (pages 1-11) JP-A-7-216647 (pages 1-7) JP-A-7-258524 (pages 1 to 43) JP-A-10-168661 (pages 1 to 11) Japanese Patent Laid-Open No. 14-20931 (pages 1-7)

  The present invention has been made as a result of studies to solve the above-described problems in the prior art, has a hydrolysis resistance superior to that of the conventional one, and is also excellent in dry pyrolysis resistance, and is a papermaking dryer. The object of the present invention is to provide polyester fibers useful as constituent materials for various industrial fabrics, such as canvas, nonwoven fabric for thermal bonding of thermal bonding processes, and fabric for conveyor belt in heat treatment furnace.

In order to achieve the object of the present invention, according to the present invention, as a component other than polyester, a copolymer of ethylene and 1-octene is 0.3 to 20% by weight, a monocarbodiimide compound is 0.01 to 1.5% by weight. %, A polyester fiber containing 0 to 3% by weight of a polycarbodiimide compound and 0 to 2% by weight of a phenolic antioxidant, wherein the carboxyl end group concentration is 10 equivalents or less than 10 ⁶ g of polyester fiber, and the polycarbodiimide The compound is the sum of the unreacted carbodiimide group (D1) in the polycarbodiimide compound and the carbodiimide group (D2) in which the carboxyl end group and / or hydroxyl end group of the polyester are partially reacted [(D1) + (D2)] containing 5 to 100 carbodiimide groups in one molecule Steal fiber is provided.

In the polyester fiber of the present invention,
The copolymer of ethylene and 1-octene has a DSC method (in nitrogen gas, heating rate 10 ° C./min) melting point of 50 ° C. or higher and a Shore A hardness (according to ASTM D-2240) of 70 or higher. There is,
The monocarbodiimide compound is N, N′-di-2,6-diisopropylphenylcarbodiimide,
The polycarbodiimide compound is an aromatic polycarbodiimide compound in which the ortho position of the phenyl group is substituted with an isopropyl group with respect to the carbodiimide group,
The phenolic antioxidant is tetrakis- [methylene-3- (3 ′, 5′-di-t-butyl-4-hydroxyphenyl) propionate] methane, and the fiber is a monofilament. Is also a preferable condition, and by satisfying at least one of these conditions, it can be expected to obtain a more excellent effect.

  Further, the polyester fiber of the present invention is for use as a constituent material of at least a part of an industrial fabric, and in particular, the industrial fabric is a papermaking dryer canvas, a belt for a thermal bonding process of a nonwoven fabric. The best effect is exhibited when the material is at least one selected from a woven fabric and a woven fabric for a conveyor belt in a heat treatment furnace.

  As will be described below, the polyester fiber of the present invention has excellent hydrolysis resistance and excellent dry heat decomposition resistance, and is a papermaking dryer canvas, a belt fabric for a thermal bonding process of a nonwoven fabric, and a heat treatment furnace. Since it is particularly suitable as a constituent material of various industrial fabrics such as the inner transport belt fabric, it has high utility value in industries such as the papermaking industry.

  Hereinafter, the present invention will be specifically described.

  The polyester in the polyester fiber of the present invention comprises a dicarboxylic acid component and a glycol component. Examples of the dicarboxylic acid component include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, 1,4-cyclohexanedicarboxylic acid, and the like. Examples of the glycol component include ethylene glycol, propylene glycol, tetramethylene glycol, and 1,4-cyclohexanedimethanol. These dicarboxylic acid components and glycol components can be used in appropriate combination. Further, a part of the dicarboxylic acid component may be replaced with adipic acid, sebacic acid, dimer acid, sulfonic acid metal salt-substituted isophthalic acid, etc., and a part of the glycol component may be diethylene glycol, neopentyl glycol, It may be replaced by 1,4-cyclohexanediol, polyalkylene glycol or the like. Furthermore, a small amount of chain branching agents such as pentaerythritol, trimethylolpropane, trimellitic acid, trimesic acid and boric acid can be used in combination. The polyester includes aliphatic polyesters such as polylactic acid, polybutylene succinate adipate, polyethylene succinate and polycaprolactone.

  Among these, it is most preferable to use polyethylene terephthalate (hereinafter referred to as PET) in which 90 mol% or more of the dicarboxylic acid component is made of terephthalic acid and 90 mol% or more of the glycol component is made of ethylene glycol.

  Polyester includes titanium oxide, silicon oxide, calcium carbonate, silicon nitride, clay, talc, kaolin, zirconium acid, carbon black and other inorganic particles, cross-linked polymer particles, various metal particles and other conventional particles. Known sequestering agents, ion-exchange agents, anti-coloring agents, light-proofing agents, inclusion compounds, antistatic agents, various colorants, waxes, silicone oils, various surfactants, various reinforcing fibers, etc. are added. May be.

  The intrinsic viscosity of the polyester used in the present invention is usually 0.5 or more, but 0.7 or more is more preferable because of excellent strength. Here, the intrinsic viscosity is an intrinsic viscosity determined from a viscosity measured at 25 ° C. in an o-chlorophenol solution, and is a value represented by [η].

  In addition, it is preferable that the polyester which comprises a polyester fiber is what carried out the solid phase polycondensation following melt polycondensation. Performing solid-phase polymerization is preferable because the concentration of carboxyl end groups (hereinafter referred to as COOH end groups) can be reduced along with the increase in the molecular weight of polyester.

Since the COOH end group concentration of the polyester fiber of the present invention is 10 equivalents (hereinafter referred to as eq) / 10 ⁶ g or less of polyester fiber, the carboxyl end group concentration of the polyester is 10 equivalents / 10 ⁶ g or less of polyester. It is preferably 5 eq / polyester 10 ⁶ g or less.

  Here, the COOH end group concentration of the polyester was measured by the method described by Pohl in ANALYTICAL CHEMISTRY Vol. 26, page 1614.

  The polyester fiber of the present invention contains 0.3 to 20% by weight of a copolymer of ethylene and 1-octene (hereinafter referred to as ET / OCT copolymer) as a component other than polyester.

  The ET / OCT copolymer is a copolymer produced from ethylene and 1-octene as a kind of metallocene catalyst system, has a relatively uniform molecular weight distribution, flexibility, flexibility, A copolymer having rubber elasticity, low permanent strain, heat resistance and the like.

  The ET / OCT copolymer has different hardness and melting point depending on the copolymerization ratio of ethylene and 1-octene, and any of them can be used. Among them, the DSC method (in nitrogen gas, When using a copolymer having a melting point measured at a heating rate of 10 ° C./min) of 50 ° C. or higher and a Shore A hardness of 55 or higher measured according to ASTM D-2240, the resulting polyester fiber This is preferable because the strength of the is good. More preferably, the melting point is 60 ° C. or more and the Shore A hardness is 70 or more, and the melting point is 70 ° C. or more and the Shore A hardness is 80 or more.

  As the ET / OCT copolymer described above, Engage (registered trademark) (a product of DuPont Dow Elastomer Japan Co., Ltd.) is commercially available, and can be obtained and used.

  The content of the ET / OCT copolymer contained in the polyester fiber is preferably 0.3 to 20% by weight, particularly preferably 1 to 10% by weight. When the content is less than 0.3% by weight, the resistance of the polyester fiber is reduced. If the hydrolyzability is insufficient and it exceeds 20% by weight, the strength of the polyester fiber is insufficient, which is not preferable.

  The ET / OCT copolymer is dispersed in the form of fine fibrils in the polyester fiber, and the monocarbodiimide compound added separately is incorporated into the fine dispersion, so that the monocarbodiimide and the hydroxyl end groups of the polyester are added to the side chain. It has the effect of suppressing deactivation and consumption by reaction, and the presence of the ET / OCT copolymer in the polyester fiber has the effect of increasing the content of the monocarbodiimide compound in the polyester fiber. Play.

  The polyester fiber of the present invention further contains 0.01 to 1.5% by weight of a monocarbodiimide compound (hereinafter referred to as MCD compound).

  The MCD compound contained in the polyester monofilament of the present invention is a compound containing one carbodiimide group (—N═C═N—) in the molecule in the polyester fiber.

  The MCD compound may be any compound having one carbodiimide group in one molecule. For example, N, N′-di-o-triylcarbodiimide, N, N′-diphenylcarbodiimide, N, N′-dioctyldecylcarbodiimide, N, N′-di-2,6-dimethylphenylcarbodiimide, N-triyl-N′-cyclohexylcarbodiimide, N, N′-di-2,6-diisopropylphenylcarbodiimide, N, N '-Di-2,6-di-tert.-butylphenylcarbodiimide, N-triyl-N'-phenylcarbodiimide, N, N'-di-p-nitrophenylcarbodiimide, N, N'-di-p-amino Phenylcarbodiimide, N, N'-di-p-hydroxyphenylcarbodiimide, N, N'-di-cyclohexylca Bojiimido, N, etc. N'- di -p- triyl carbodiimide. One or two or more compounds may be arbitrarily selected from these MCD compounds and included in the polyester fiber, but the compound having an aromatic skeleton tends to be advantageous from the viewpoint of stability after addition to the polyester. Among them, N, N'-di-2,6-diisopropylphenylcarbodiimide, N, N'-di-2,6-di-tert.-butylphenylcarbodiimide, N, N'-di-2,6-dimethyl Phenylcarbodiimide, N, N′-di-o-triylcarbodiimide and the like tend to be advantageous, and N, N′-di-2,6-diisopropylphenylcarbodiimide (hereinafter referred to as TIC) is particularly preferable. As this TIC, commercially available products such as “STABAXOL” (registered trademark) manufactured by Rhein-Chemie or “Stabilizer” (registered trademark) 7000 manufactured by Raschig AG can be used. Further, the MCD compound can be used as a master batch which is previously contained in the ET / OCT copolymer at a high concentration.

  The MCD compound contained in the polyester fiber of the present invention has an action of reaction-blocking / inactivating the COOH end group of the polyester itself having a catalytic action for promoting the hydrolysis of the polyester.

  The COOH end group of the polyester is generated by raw material origin, polycondensation, heat and hydrolysis during melt molding, and hydrolysis during use in a moist heat atmosphere.

  In order to suppress the hydrolysis of the polyester, the polyester before melt molding contains an MCD compound to inactivate the COOH end groups, and the molded product also contains the MCD compound in a moist heat atmosphere. It is necessary to deactivate COOH end groups generated by hydrolysis during use. Therefore, in order to extend the service life of the polyester fiber, it is important how much MCD compound is contained in the fiber.

  Therefore, the content of the MCD compound contained in the polyester fiber is preferably in the range of 0.01 to 1.5% by weight, particularly 0.015 to 1.2% by weight, and if the content is less than 0.01% by weight If the hydrolysis resistance is insufficient and it exceeds 1.5% by weight, melt spinning becomes unstable, which is not preferable.

Here, the content of the MCD compound in the polyester fiber referred to in the present invention is measured by the following method.
(1) Weigh about 200 mg of sample into a 100 ml volumetric flask.
(2) Add 2 ml of hexafluoroisopropanol / chloroform (volume ratio 1/1) to dissolve the sample,
(3) When the sample is dissolved, add 8 ml of chloroform.
(4) Acetonitrile / chloroform (volume ratio 9/1) was gradually added to make 100 ml while precipitating the polymer.
(5) The sample solution is filtered through a disk filter having an aperture of 0.45 μm and quantitatively analyzed by HPLC. The HPLC analysis conditions are as follows:
Column: Inertsil ODS-2 4.6 mm × 250 mm
Mobile phase: acetonitrile / water (volume ratio 94/6)
Flow rate: 1.5 ml / min.
Sample volume: 20 μl
Detector: UV (280 nm).

  The polyester fiber of the present invention further contains 0 to 3% by weight of a polycarbodiimide compound. However, the polycarbodiimide compound is a total of the unreacted carbodiimide group (D1) in the polycarbodiimide compound and the carbodiimide group (D2) in which the COOH terminal group and / or the hydroxyl terminal group of the polyester are partially reacted. [(D1) + (D2)] contains 5 to 100 carbodiimide groups in one molecule.

  Examples of the polycarbodiimide compound (hereinafter referred to as PCD compound) contained in the polyester fiber of the present invention include an isopropyl group at the 2,6-position and / or the 2,4,6-position of the benzene ring bonded to the carbodiimide group. Aromatic PCD compound having a substituted structure as a repeating unit, aromatic PCD compound synthesized from 1,3,5-tris (1-methylethyl) -2,4-diisocyanatobenzene, 1,3,5- Aromatic PCD compound synthesized from a mixture of tris (1-methylethyl) -2,4-diisocyanatobenzene and 2,6-diisopropylbenzene diisocyanate, 1,3,5-tris (1-methylethyl) Aromatic PCD synthesized from a mixture of -2,4-diisocyanatobenzene and 1,3,5-tris (isopropyl) -2,4-diisocyanatobenzene Preferred examples include alicyclic PCD compounds synthesized from a compound and poly [1,1′-dicyclohexylmethane (4,4′-diisocyanate)]. However, there is no limitation to this.

  Among these PCD compounds, aromatic PCD compounds having a structure in which an isopropyl group is substituted at the 2,6 position and / or 2,4,6-position of a benzene ring bonded to a carbodiimide group are particularly preferable.

  An aromatic PCD compound having a structure in which an isopropyl group is substituted at the 2,6 position and / or 2,4,6-position of the benzene ring bonded to the carbodiimide group is, for example, “STABAXOL” having an average molecular weight of about 3,000. (Registered trademark) P (Rhein Chemie product), “STABAXOL” (registered trademark) P100 (Rhein Chemie product) with an average molecular weight of about 10,000 and “STABILIZER” (registered trademark) 9000 (product of Raschig) with an average molecular weight of about 20,000 Are commercially available and can be obtained and used. The alicyclic PCD compound synthesized from the poly [1,1′-dicyclohexylmethane (4,4′-diisocyanate)] is, for example, “CARBODILITE” (registered trademark) HMV-8CA (Nisshinbo Co., Ltd. product). Are commercially available and can be obtained and used.

  These PCD compounds are also commercially available as masterbatches previously kneaded into polyester. For example, “STABAXOL” is a PET masterbatch containing 15% by weight of “STABAXOL” (registered trademark) P100 having an average molecular weight of about 10,000. "STABILIZER" 9500 (registered trademark) which is a PET masterbatch containing 15% by weight of "(registered trademark) KE-7646 (product of Rhein Chemie) and the above-mentioned" STABILIZER "(registered trademark) 9000 having an average molecular weight of about 20,000 (Raschig products) are known. The PCD compound and the MCD compound can be used by dissolving and mixing each other.

  The content of the PCD compound can be adjusted in the range of 0 to 3% by weight depending on the target hydrolysis resistance level. The presence of the PCD compound can further suppress degradation of the polyester fiber by hydrolysis. However, if the content of the PCD compound exceeds 3% by weight, it is not preferable because the melt viscosity of the polyester is excessively increased or the discharge and molding become difficult.

  The polyester fiber of the present invention further contains 0 to 2% by weight, preferably 0.05 to 1% by weight, of a phenolic antioxidant.

  Examples of the phenol-based antioxidant in the present invention include 2,6-di-t-butyl-p-cresol, butylhydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearyl-β- ( 3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2,2'-methylenebis (4-methyl-6-t-butylphenol), 22'-methylenebis (4-ethyl-6-t-butylphenol) 4,4′-thiobis (3-methyl-6-tert-butylphenol), 4,4′-butylidenebis (3-methyl-6-tert-butylphenol), 3,9-bis [1,1′-dimethyl- 2- [β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl] 2,4,8,10-tetraoxaspiro [5,5] undecane, 1,1,3- Tris (2-methyl-4-hydroxy-5 -T-butylphenyl) butane, 1,3,5-trimethyl-2,4,6- (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tetrakis- [methylene-3- (3 ' , 5′-di-tert-butyl-4-hydroxyphenyl) propionate] methane, bis [3,3′-bis- (4′-hydroxy-3′-tert-butylphenyl) butyric acid] glycol ester, and 1,3,5-tris (3 ′, 5′-di-t-butyl-4′-hydroxybenzyl) -S-triazine-2,4,6- (1H, 3H, 5H) trione and the like. it can. However, there is no limitation to this.

  Of these phenolic antioxidants, tetrakis- [methylene-3- (3 ′, 5′-di-t-butyl-4-hydroxyphenyl) propionate] methane is particularly preferred. The tetrakis- [methylene-3- (3 ′, 5′-di-t-butyl-4-hydroxyphenyl) propionate] methane is, for example, “Irganox” (registered trademark) 1010 (product of Ciba Specialty Chemicals) Is commercially available and can be obtained and used.

  By containing the phenol-based antioxidant, the polyester fiber of the present invention has further sufficient dry heat decomposition resistance. However, if the content of the phenolic antioxidant exceeds 2% by weight, the hydrolysis resistance is lowered, which is not preferable.

The COOH end group concentration of the polyester fiber of the present invention is 10 eq / 10 ⁶ g or less of polyester fiber, more preferably 5 eq / 10 ⁶ g or less of polyester fiber.

  The production of the polyester fiber of the present invention comprises polyester, ET / OCT copolymer 0.3 to 20% by weight, MCD compound 0.01 to 1.5% by weight, PCD compound 0 to 3% by weight and phenolic antioxidant. It can be carried out by melt-kneading the agent 0 to 2% by weight and then melt spinning.

  Specific examples of the production of the polyester fiber of the present invention include, for example, a required amount of polyester pellets and ET / OCT copolymer pellets in a uniaxial or biaxial extruder and a predetermined amount of PCD compound in a high concentration as required. Metered polyester masterbatch pellets and phenolic antioxidants are weighed and metered at the top of the extruder after melted and kneaded by adding liquid MCD compound from the entrance of the extruder or from the middle of the barrel of the extruder. Extrusion from the spinneret through a gear pump, cooling, stretching, heat setting, etc. (hereinafter referred to as production method 1), or the necessary amount of polyester pellets or ET / OCT copolymer for a single or twin screw extruder Metering pellets, if necessary, powdered PCD compound and phenolic antioxidant, After liquid MCD compound is metered and melted and kneaded from the entrance of the extruder or from the middle of the barrel of the extruder, it is extruded from the spinneret through a measuring gear pump provided at the end of the extruder, and then cooled, stretched, and heat set. The method of etc. can be mentioned. Among these methods, the production method 1 is industrially advantageous.

  In these production methods, it is advantageous to adjust the temperature at which the polyester, the ET / OCT copolymer, the MCD compound, the PCD compound, and the phenolic antioxidant are melt-kneaded to be not less than the melting point of the polyester and not more than 295 ° C. It is more advantageous to adjust the temperature within the range of 275 ° C to 290 ° C. Further, the residence time from melting to spinning is advantageously 7 minutes or less, more preferably 5 minutes or less. By adjusting the melt-kneading temperature and the residence time from melting to spinning within the above range, the polyester fiber of the present invention excellent in hydrolysis resistance and dry pyrolysis resistance can be preferably produced. .

  The shape of the cross section perpendicular to the fiber axis direction of the polyester fiber single yarn of the present invention (hereinafter referred to as cross-sectional shape or cross section) is a circle, hollow, flat, square, T-shaped, Y-shaped, half-moon shaped, triangular, five or more corners It may have any cross-sectional shape such as a polygonal shape, a multileaf shape, a dogbone shape, and a saddle shape.

  The form of the polyester fiber of the present invention is arbitrary such as multifilament, monofilament, short fiber, cotton-like and non-woven fabric, but the polyester fiber of the present invention is a paper-making dryer canvas, belt fabric for thermal bonding process of non-woven fabric, and conveyance in heat treatment furnace In the case of a constituent material of various industrial fabrics typified by belt fabrics, monofilaments are particularly preferable. The monofilament here is a continuous yarn composed of one single yarn.

  When the monofilament of the present invention is used as a constituent material for industrial fabrics, the cross-sectional shape of the monofilament is preferably a circle or a flat shape. In particular, when a monofilament is used as a warp for a papermaking dryer canvas, a monofilament having a flat cross-sectional shape is preferably used from the viewpoint of effectively exhibiting antifouling properties and flatness of the papermaking dryer canvas. Here, flat means an ellipse, square, or rectangle, but other than an exact ellipse, square, or rectangle defined mathematically, a shape that is generally similar to an ellipse, square, or rectangle, for example, square and rectangular corners. Including a rounded shape. In the case of an ellipse, the length of the major axis (LD) and the length of the minor axis (SD) intersecting at right angles at the center of the ellipse satisfy the expression 1.0 ≦ LD / SD ≦ 10. In the case of a square or a rectangle, the length (LD) of the long side and the length (SD) of the short side of the rectangle may satisfy the expression 1.0 ≦ LD / SD ≦ 10. preferable.

  The length of the line segment passing through the center of gravity of the monofilament cross section can be appropriately selected depending on the application, but is preferably in the range of 0.05 to 2.5 mm. Further, the required strength of the yarn varies depending on the use, but is preferably approximately 2 cN / dtex or more.

  The polyester fiber of the present invention thus obtained is superior in hydrolysis resistance compared to conventional ones and has sufficient dry heat decomposition resistance, and is suitable as a constituent material of at least a part of industrial fabrics.

  The industrial fabrics in the present invention are, for example, papermaking wires (papermaking nets), papermaking dryer canvas, belt fabrics for thermal bonding processes of nonwoven fabrics, fabrics for conveyor belts in heat treatment furnaces, fabrics for tire cords, and various filter fabrics. That is.

  Here, the papermaking wire is a woven fabric used in the paper winding process as various woven fabrics such as plain weave, double woven fabric, and triple woven fabric, and is used as a long mesh or a round mesh. Paper machine dryer canvas is a dryer for paper machines as various fabrics such as plain weave, double weave, and triple weave (including spiral fabrics in which weft and weft yarns interwoven by spiral monofilaments are used) It is the fabric used to dry the paper inside. The belt woven fabric for the thermal bonding process of the nonwoven fabric is a woven fabric for allowing the nonwoven fabric to pass through a furnace in order to fuse the low-melting-point polyethylene fibers constituting the nonwoven fabric. , Etc. The fabric for a conveyor belt in a heat treatment furnace refers to a fabric that transports a semi-finished product in a high-temperature zone for drying, thermosetting, sterilizing, cooking, and the like of various semi-finished products. Tire cord woven fabric is a woven fabric that is embedded in rubber as a reinforcing agent for automobile tires. Various filters are woven fabrics that filter high-temperature liquids, gases, powders, etc. is there.

  Among these, the polyester fiber of the present invention is selected from a papermaking dryer canvas, a belt fabric for a thermal bonding process of a nonwoven fabric, and a fabric for a conveyor belt in a heat treatment furnace, which require high hydrolysis resistance and high dry heat resistance. It is particularly suitable as a constituent material of at least a part of the industrial fabric.

  Hereinafter, the present invention will be described in detail with reference to examples of polyester monofilaments which are preferred forms of the polyester fiber of the present invention.

  The characteristic values in the following examples are measured by the following methods unless otherwise specified in each example.

1. Monofilament tensile test It was performed according to JIS L1013-1992.
(1) Sample grip interval 25cm
(2) Tensile speed 30 cm / min.
(3) Test temperature 20 ° C

2. Hydrolysis resistance of monofilaments Monofilaments are put into a 100 liter autoclave and treated for 14 days, 16 days, and 18 days in 121 ° C saturated steam, and then the strength of monofilaments after treatment is determined by tensile test of the above monofilaments. The strength retention compared with the strength of the previous monofilament was used as a measure of hydrolysis resistance (hereinafter referred to as strength retention after steaming). The higher the strength retention after steaming, the better the hydrolysis resistance.

3. Resistance to dry pyrolysis of monofilaments Monofilaments are placed in a hot air circulation type heat resistance tester and treated in heated air at 180 ° C for 15 days, 18 days, and 20 days, and then the strength of the monofilaments after treatment is determined by the tensile test of the above monofilaments. The strength retention compared with the strength of the monofilament before treatment was determined as a measure of dry pyrolysis resistance (hereinafter referred to as strength retention after dry heat treatment). The higher the strength retention after dry heat treatment, the better the dry pyrolysis resistance.

[Examples 1 to 12, Comparative Example 1]
As raw materials, a polyethylene terephthalate dry chip (hereinafter referred to as a PET chip) having an intrinsic viscosity of 0.94 and a terminal carboxyl group concentration of 15 eq / 10 ⁶ g produced by known melt polycondensation and solid phase polycondensation, ET / OCT co-polymerization Engage (registered trademark) (hereinafter referred to as “Eng”) having a melting point of 50 ° C. and a Shore A hardness of 60 (hereinafter “Eng” product) ENR8137 (1% by weight of talc on the pellet surface as an antiblocking agent) ), Which is also an ET / OCT copolymer having a melting point of 60 ° C. and Shore A hardness of 75 “Eng” 8200 and also an ET / OCT copolymer having a melting point of 98 ° C. and a Shore A hardness of 94 "Eng" 8440, TIC ("STABAXOL" (registered trademark) I (product of Rhein Chemie)) as an MCD compound, bound to a carbodiimide group PET masterbatch containing 15% by weight of an aromatic PCD compound having a structure in which an isopropyl group is substituted at the 2,6-position and / or 2,4,6-position of the benzene ring to be combined (hereinafter referred to as PCD- “STABAXOL” (registered trademark) KE7646 (product of Rhein Chemie) which is MB) and tetrakis- [methylene-3- (3 ′, 5′-di-t-butyl-4) which is a kind of phenolic antioxidant -Hydroxyphenyl) propionate] methane ("Irganox" (registered trademark) 1010 (product of Ciba Specialty Chemicals)) (hereinafter referred to as IR1010) was prepared.

  While weighing the PET chips, ET / OCT copolymers, KE7646 and IR1010 at the quantitative ratios shown in Table 1, they are converted into a single-screw extruder via the hopper of the single-screw extruder and the polymer pipe at the bottom of the hopper. Continuous supply. At the same time, the liquid TIC was continuously supplied to the chip in the polymer pipe below the hopper while being metered at the quantitative ratio shown in Table 1. A melt polymer melt-kneaded for 3 minutes at about 282 ° C. in a single-screw extruder was spun from a spinneret for circular cross-section yarns through a filtration layer in a spin pack via a gear pump. The spun monofilament was cooled in a hot water bath at 70 ° C. and then stretched and heat-set by a total of 5.0 times according to a conventional method to obtain a monofilament having a diameter of 0.45 mm and a circular cross section.

  The composition and properties of the obtained monofilament are shown in Table 1.

  From the results of Examples 1 to 12 and Comparative Example 1, the polyester monofilaments (Examples 10 to 12) which are the polyester fibers of the present invention containing ET / OCT copolymers and an MCD compound are resistant to hydrolysis. It turns out that it is excellent. Moreover, it turns out that the polyester monofilament (Examples 4-6) of this invention containing a PCD compound in addition to ET / OCT copolymers and an MCD compound has much better hydrolysis resistance. Furthermore, the polyester monofilaments of the present invention (Examples 7 to 9) containing a phenolic antioxidant in addition to the ET / OCT copolymers and MCD compounds are excellent in hydrolysis resistance and dry heat degradation resistance. It can be seen that it is. Furthermore, the polyester monofilaments of the present invention (Examples 1 to 3) containing ET / OCT copolymers, MCD compounds, PCD compounds and phenolic antioxidants have excellent hydrolysis resistance and sufficient dry heat resistance. Fabrics that have decomposability and are used in paper machines such as paper dryer canvas, etc. that are used for a long time in a high-temperature and high-humidity atmosphere, belt fabrics for thermal bonding processes of nonwoven fabrics, and conveyor belts in heat treatment furnaces It can be seen that it is useful as a constituent material for at least a part of various industrial fabrics represented by industrial fabrics.

  The polyester fiber of the present invention has excellent hydrolysis resistance and sufficient dry heat decomposition resistance, so that it can be attached to a paper machine such as a paper machine dryer canvas or a belt fabric for a thermal bonding process of a nonwoven fabric. In addition, it is useful as a constituent material for at least a part of various industrial fabrics typified by fabrics for conveyor belts in heat treatment furnaces, and can be used for a longer period of time than before and has high industrial utility value.

Claims (8)

As components other than polyester, a copolymer of ethylene and 1-octene of 0.3 to 20% by weight, a monocarbodiimide compound of 0.01 to 1.5% by weight, a polycarbodiimide compound of 0 to 3% by weight, and a phenolic antioxidant Polyester fiber containing 0 to 2% by weight of an agent, having a carboxyl end group concentration of 10 equivalents / 10 ⁶ g or less of polyester fiber, and the polycarbodiimide compound is an unreacted carbodiimide group in the polycarbodiimide compound ( D1) and a total of [(D1) + (D2)] of carbodiimide group (D2) in which the carboxyl end group and / or the hydroxyl end group of the polyester are partially reacted 5 to 100 per molecule A polyester fiber containing a carbodiimide group. The copolymer of ethylene and 1-octene has a DSC method (in nitrogen gas, heating rate 10 ° C./min) melting point of 50 ° C. or higher and a Shore A hardness (according to ASTM D-2240) of 70 or higher. The polyester fiber according to claim 1, wherein the polyester fiber is present. The polyester fiber according to claim 1 or 2, wherein the monocarbodiimide compound is N, N'-di-2,6-diisopropylphenylcarbodiimide. The polyester according to any one of claims 1 to 3, wherein the polycarbodiimide compound is an aromatic polycarbodiimide compound in which the ortho position of the phenyl group is substituted with an isopropyl group with respect to the carbodiimide group. fiber. The phenolic antioxidant contained in the polyester fiber is tetrakis- [methylene-3- (3 ', 5'-di-t-butyl-4-hydroxyphenyl) propionate] methane. The polyester fiber of any one of 1-4. The polyester fiber according to claim 1, wherein the polyester fiber is a monofilament. The polyester fiber according to any one of claims 1 to 6, wherein the polyester fiber is used as a constituent material of at least a part of an industrial fabric. 8. The polyester fiber according to claim 7, wherein the industrial fabric is at least one selected from a paper-making dryer canvas, a belt fabric for a thermal bonding process of a nonwoven fabric, and a fabric for a conveyor belt in a heat treatment furnace.