JP2010126822A - Polyester filament - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester filament capable of holding excellent moist heat resistance even if the moist heat treatment is carried out at high temperature, having good yarn quality and excellent surface smoothness, and being produceable in good operability. <P>SOLUTION: The polyester filament comprises a polyester containing a polyolefin of 0.1-20 mass% having a melting point of ≥150°C, and a carbodiimide compound of 0.1-4.0 mass%, and has a relative viscosity of ≥1.40 and a carboxy terminal content of ≤15.0 eq./t. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a filament for industrial materials, particularly a polyester filament having excellent moisture and heat resistance suitable for a belt cloth, a filter and the like.

  Polyester filaments have excellent physical properties, and are suitably used for filaments for industrial materials, particularly for paper-making canvases, belt cloths or filters. However, the filament for industrial materials is used in a severe environment, and the filament may deteriorate in a relatively short period of time, and may not be used. For example, a paper making canvas using a polyester filament is exposed to a high temperature and high humidity condition because it is used in processes such as a paper making press zone and a subsequent drying zone. For this reason, it is known that polyester filaments undergo heat and hydrolysis degradation due to the influence of water, heat, and water vapor, and cannot be used.

  Hydrolysis of polyester by water and water vapor occurs by attacking the ester bond portion of water molecules, carboxyl groups and hydroxyl groups are formed, polymer chains are split, and hydrolysis degradation proceeds. Furthermore, the carboxyl end group thus formed plays a catalytic role in the hydrolysis reaction of the polyester, and the hydrolysis rate is accelerated as the amount of the carboxyl end group increases. In particular, hydrolysis is accelerated when heat is applied.

  Therefore, as a countermeasure against thermal hydrolysis, a method for improving the heat-and-moisture resistance of the filament by adopting a polyester having a small amount of carboxyl end groups is employed. For example, Patent Literature 1 and Patent Literature 2 disclose a method of obtaining a polyester filament having improved wet heat resistance by adding a carbodiimide compound and blocking carboxyl end groups. However, it has been difficult to maintain the heat-and-moisture resistance over a long period only by reducing the amount of carboxyl end groups in the polyester filament.

  Patent Document 3 discloses a method for improving moisture and heat resistance performance by incorporating a polyolefin and a carbodiimide compound into polyester. However, when ordinary polyolefin is blended with polyester, there is a problem that phase separation is liable to occur, and filaments are fibrillated and yarn properties are deteriorated.

  Therefore, in order to solve the above problems, Patent Document 4 discloses that a polyester mainly composed of polyethylene terephthalate contains a polymer having an ethylene component and a glycidyl methacrylate component, and further includes the polyester, the ethylene component, and glycidyl methacrylate. There has been proposed a moisture and heat resistant monofilament in which the amount of residual carbodiimide in the yarn is increased by adding a compatibilizer having compatibility with the copolymer with the component.

  The polyolefin component which is a polymer having the ethylene component and the glycidyl methacrylate component can reduce phase separation from the polyester because the glycidyl methacrylate group reacts with the terminal carboxyl group of the polyester. For this reason, the monofilament excellent in wet heat resistance was obtained, suppressing fibrillation.

However, if a polyolefin with a high copolymerization ratio of the glycidyl methacrylate component is used to further improve the heat and moisture resistance, the reaction with the polyester proceeds excessively, resulting in a marked increase in melt viscosity, resulting in melt viscosity spots on the polymer. Occurs and the yarn-making property is deteriorated. In addition, since the polyolefin itself does not have heat resistance, the monofilament has a problem that it becomes inferior in wet heat resistance as the wet heat treatment becomes higher.
Japanese Patent Publication No. 1-15604 JP-A-4-289221 Japanese Patent Application Laid-Open No. 11-124731 JP-A-11-323661

  The present invention solves the above-mentioned problems, can maintain excellent moisture and heat resistance performance even when the wet heat treatment is high temperature, good yarn quality performance, excellent surface smoothness, In addition, an object of the present invention is to provide a polyester filament that can be produced with good operability.

  The inventors of the present invention have reached the present invention as a result of intensive studies to solve the above problems.

  That is, the present invention is a filament comprising a polyester containing 0.1 to 20% by mass of a polyolefin having a melting point of 150 ° C. or higher and 0.1 to 4.0% by mass of a carbodiimide compound, and having a relative viscosity of 1.40. The gist of the polyester filament is characterized in that the amount of carboxyl end groups is 15.0 eq / t or less.

  The polyester filament of the present invention has excellent moisture and heat resistance with little decrease in strength after wet heat treatment even when subjected to high temperature wet heat treatment. Further, it is excellent in yarn quality such as strength and elongation and surface smoothness, and can be obtained with high productivity. Therefore, the polyester filament of the present invention can be suitably used for products such as filaments for industrial materials, in particular, canvas yarns for papermaking, which are industrial fabrics, belt fabrics, filters and the like.

  Hereinafter, the present invention will be described in detail.

  As polyester which forms the polyester filament of this invention, aliphatic polyester and aromatic polyester can be used.

  Examples of aliphatic polyesters include poly-α-hydroxy acids such as polylactic acid and polyglycolic acid, poly-β-hydroxyalkanos such as poly-β-hydroxybutyric acid and poly- (β-hydroxybutyric acid / β-hydroxyvaleric acid). And poly-ω-hydroxyalkanoates such as poly-β-propiolactone and poly-ε-caprolactone.

  Examples of the aromatic polyester include polyesters mainly composed of polyalkylene terephthalates such as polyethylene terephthalate (PET), polybutylene terephthalate, and polytrimethylene terephthalate. Aromatic dicarboxylic acids such as isophthalic acid and 5-sulfoisophthalic acid, adipine Aliphatic dicarboxylic acids such as acid, succinic acid, suberic acid, sebacic acid and dodecanedioic acid, and aliphatic diols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and glycol Acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxypentanoic acid, hydroxyheptanoic acid, hydroxyoctanoic acid and other aliphatic carboxylic acids, and ε-caprolactone The emission or the like may be copolymerized.

  Among them, the polyester filament of the present invention preferably has a melting point of 155 ° C. or higher in order to make the polyester filament highly resistant to wet heat treatment at high temperatures.

  The polyester filaments of the present invention may be monofilaments or multifilaments, but are preferably those having a fineness of 100 to 20000 dtex for suitable use in industrial materials.

  And the polyester filament of this invention contains 0.1-20 mass% of polyolefin with a melting | fusing point of 150 degreeC or more in a polyester which forms a filament, and 0.1-4.0 mass% of carbodiimide compounds.

  As the polyolefin, homopolymers such as polyethylene, polypropylene, polybutene, poly-4-methylpentene, and polycycloolefin, and copolymers such as ethylene-acrylic acid copolymer and ethylene-methyl methacrylate copolymer can be used. Of these, polymethylpentene is particularly preferable from the viewpoint of heat resistance.

  The melting point of these polyolefins is required to be 150 ° C. or higher, preferably 180 ° C. or higher.

  And it is necessary to make content of polyolefin in polyester into 0.1-20 mass%, and it is preferable to set it as 2.0-10 mass% especially.

  When the melting point of the polyolefin is less than 150 ° C. or the content is less than 0.1% by mass, the yarn quality performance such as strength is deteriorated when subjected to wet heat treatment at a high temperature of 135 ° C. or more, and sufficient moisture resistance It cannot be made into the polyester filament which has thermal performance.

  On the other hand, when the content of the polyolefin exceeds 20% by mass, the spinning property is deteriorated or sufficient strength cannot be obtained.

  Moreover, in this invention, in order to react with the terminal group of polyester and to reduce the amount of carboxyl terminal groups, a carbodiimide compound is included as a terminal blocker.

  Specific examples of the carbodiimide compound used in the present invention include N, N′-bis (2,6-dimethylphenyl) carbodiimide, N, N′-bis (2,6-diethylphenyl) carbodiimide, and N, N′-bis. (2,6-diisopropylphenyl) carbodiimide, N, N′-bis (2-isopropylphenyl) carbodiimide and the like.

  Among these, N, N′-bis (2,6-diisopropylphenyl) carbodiimide is preferable because it can be used at a heat resistance and industrial level.

  The content of the carbodiimide compound in the polyester needs to be 0.1 to 4.0% by mass, preferably 0.1 to 3.5% by mass, and more preferably 0.5 to 2%. It is preferable to set it as 5 mass%. When the content is less than 0.1% by mass, the carboxyl end groups are not sufficiently blocked, and the moisture and heat resistance is not sufficient. On the other hand, if it exceeds 4.0% by mass, the yarn forming property is deteriorated and the yarn quality performance such as strength is also lowered.

  The polyester filament of the present invention contains the carbodiimide compound as described above, and the amount of carboxyl end groups of the filament is preferably 15.0 eq / t or less, and more preferably 10.0 eq / t or less. preferable.

  Moreover, it is preferable that 20-28000 ppm of the carbodiimide compound of an active state remains in the polyester filament of this invention, and it is preferable that 100-20000 ppm remains especially.

  The active state means a state capable of reacting with a carboxyl group or a water molecule. When the content of the carbodiimide compound in the active state is less than 20 ppm, the effect of the carbodiimide compound is hardly expressed, and the carboxyl terminal of the filament It becomes difficult to make the base amount 15.0 eq / t or less. On the other hand, in order to make it exceed 28000 ppm, it is necessary to make the content of the carbodiimide compound exceed 4.0% by mass, so that the yarn-making property is deteriorated, and the obtained filaments are deteriorated in yarn quality such as strength. .

  Furthermore, the polyester filament of the present invention preferably has a strength retention of 30% or more after being treated in a saturated water vapor at 135 ° C. for 48 hours (wet heat treatment) as a yarn property exhibiting heat-and-moisture resistance. It is preferable that it is 60% or more. If the strength retention is less than 30%, when subjected to a wet heat treatment at a high temperature, the yarn quality is deteriorated and the heat-and-moisture resistance is inferior, so that it is difficult to use for industrial materials.

The strength retention is calculated as follows.
Strength retention (%) = (Strength of polyester filament after wet heat treatment / Strength of polyester filament before wet heat treatment) × 100
The strength (cN / dtex) of the polyester filament is measured using an autograph AG-1 type manufactured by Shimadzu Corporation with a sample length of 25 cm, a tensile speed of 30 cm / min, and an initial load of 1/20 of the fineness.

  The strength of the polyester filament of the present invention before wet heat treatment is preferably 6.0 cN / dtex or higher, and the strength after wet heat treatment is preferably 2.4 cN / dtex or higher.

  The polyester filament of the present invention has a relative viscosity of 1.40 or higher, and preferably has a relative viscosity of 1.44 or higher. When the relative viscosity of the filament is less than 1.40, the filament does not satisfy a sufficient strength, so that it is difficult to put it to practical use as an industrial material application.

  In order to set the relative viscosity of the polyester filament to 1.40 or more, for example, when PET is used as the polyester, first, a prepolymer having a relative viscosity of 1.25 to 1.45 is obtained by an ordinary melt polymerization method. Next, this prepolymer pellet is heated in a solid phase under reduced pressure or an inert gas flow to perform a solid phase polymerization reaction, and a relative viscosity of 1.43 or more (however, greater than the relative viscosity of the prepolymer) Of polyester. If the relative viscosity of the prepolymer is not appropriate, the total polymerization time will be remarkably increased, or the amount of carboxyl end groups of the polyester after solid-phase polymerization cannot be kept within a predetermined range. It is desirable that the relative viscosity be in the above range.

  In addition, when the polyester after solid-phase polymerization has a relative viscosity of less than 1.43, the yarn-making property is deteriorated or the yarn quality is insufficient, and the filaments obtained by melt spinning have a relative viscosity. It tends to be difficult to make the viscosity 1.40 or more.

  In addition, it is preferable to select the conditions for the solid phase polymerization so that the relative viscosity is about 0.10 to 0.40 higher than that of the prepolymer by solid phase polymerization. This reduces the amount of carboxyl end groups of the polyester and removes impurities such as oligomers.

  In addition, in the polyester filament of the present invention, if necessary, the heat stabilizer, crystal nucleating agent, matting agent, pigment, light proofing agent, weathering agent, lubricant, as long as the object of the present invention is not impaired. An antioxidant, an antibacterial agent, a fragrance, a plasticizer, a dye, a surfactant, a flame retardant, a surface modifier, various inorganic and organic electrolytes, and other similar additives may be contained.

  Next, the manufacturing method of the polyester filament (monofilament) of this invention is demonstrated using an example.

  Using the polyester obtained by solid phase polymerization as described above, melt spinning is performed at a spinning temperature of 350 ° C. or lower, preferably 310 ° C. or lower. The spun filament is cooled and solidified in liquid or air. Next, the cooled and solidified filament is stretched after being wound once or without being wound.

  Stretching can be performed in a single stage or multiple stages including two or more stages, but is preferably performed in multiple stages. First, 3.0 to 6.5 times the first stage stretching is performed in a liquid at 65 to 95 ° C. or in a gas at 70 to 200 ° C., and then a liquid at 150 to 300 ° C. that is higher in temperature than the first stage stretching. Alternatively, the second and subsequent stages are stretched so that the total stretching ratio is 5.0 to 8.0 times in a gas.

  At this time, the total draw ratio is set to be higher than the first stage draw ratio. If the stretching temperature is lower than the above range, heating is insufficient, and stretching spots and thread breakage occur. On the other hand, if the stretching temperature is too high, filament melting and thermal deterioration occur, which is not preferable. Further, if the total draw ratio is less than 5.0 times, the yarn quality, particularly the linear strength, of the obtained filament tends to be low. On the other hand, if the total draw ratio is larger than 8.0 times, the molecular orientation cannot cope with plastic deformation in the fiber, so that microvoids are generated in the fiber, and it becomes difficult to obtain a filament exhibiting satisfactory performance. Moreover, it is preferable to perform relaxation heat treatment at a relaxation rate of 1.0 to 15.0% in a gas at 150 to 500 ° C. after stretching.

Next, the present invention will be specifically described by way of examples. In addition, the measurement and evaluation of the characteristic value in an Example were performed as follows.
[Relative viscosity]
An equimass mixture of phenol and ethane tetrachloride was used as a solvent, and measurement was performed using an Ubbelohde viscometer under the conditions of a concentration of 0.5 g / dl and a temperature of 20 ° C.
[Remaining amount of active carbodiimide compound]
The polyester filament was dissolved in a mixture of hexafluoroisopropanol and chloroform, reprecipitated with acetonitrile, and diluted with acetonitrile as a measurement solution, and measured using HPLC manufactured by Hewlett-Packard Company.
[Amount of carboxyl end group]
The polyester filament was dissolved in benzyl alcohol and titrated with a 0.1 N potassium hydroxide methanol solution.
[Strength, strength retention]
It was measured and calculated by the method described above.
[Melting point]
A differential scanning calorimeter DSC-2 manufactured by Perkin Elmer was used, and the measurement was performed under the condition of a heating rate of 20 ° C./min.
[Yarn-making property]
Melt spinning was performed continuously for 300 minutes, and the following three stages were evaluated based on the number of yarn breaks per 60 minutes.
When thread breakage is less than 1 time
When thread breakage is once or twice ... △
When thread breakage is 3 or more times ×
[Surface smoothness]
The fiber diameter of the obtained polyester filament was measured with a micrometer, and evaluated according to the following four stages according to the variation rate of the fiber diameter value.
Fluctuation rate less than 4% ... ◎
The fluctuation rate is 4% or more and less than 8%.
Fluctuation rate of 8% or more and less than 12% ・ ・ ・ △
Fluctuation rate of 12% or more ... ×

Example 1
Ethylene glycol and terephthalic acid are melt polycondensed by a conventional method to obtain a prepolymer pellet having a relative viscosity of 1.34 and a carboxyl end group amount of 30.9 eq / t, and then a solid-phase polymerization reaction is performed to obtain a relative viscosity of 1.55. A solid phase polymerization pellet having a carboxyl end group amount of 15.8 eq / t was obtained. To this PET pellet, polymethylpentene (manufactured by Mitsui Chemicals, TPX DX350, melting point 233 ° C.) as polyolefin and N, N′-bis (2,6-diisopropylphenyl) carbodiimide (manufactured by Matsumoto Yushi Co., STABAXOL EN) as carbodiimide compound -160) was added. Melt spinning was performed so that the content of polymethylpentene in PET was 1.0% by mass and the content of carbodiimide compound was 1.5% by mass. The melt spinning was performed using an extruder type spinning apparatus at a spinning temperature of 295 ° C. After cooling the spun yarn, it was drawn at a take-up speed of 500 m / min to obtain an undrawn yarn. Next, the obtained unstretched yarn is subjected to a first stage stretching at 150 ° C. and a stretching ratio of 3.0 times, followed by a second stage stretching at 200 ° C., with a total stretching ratio of 5.0 times. It extended | stretched so that it might become. After stretching, a relaxation heat treatment was performed in a 190 ° C. gas at a relaxation rate of 5.0%.
The obtained polyester filament (monofilament) had a fineness of 160 dtex and a carboxyl end group amount of 4.8 eq / t.

Examples 2-3 and Comparative Example 2
A polyester filament was obtained in the same manner as in Example 1 except that the content of polyolefin (polymethylerpentene) was changed as shown in Table 1.

Examples 4-5, Comparative Examples 3-4
A polyester filament was obtained in the same manner as in Example 1 except that the content of the carbodiimide compound was changed as shown in Table 1.

Example 6
A polyester filament was obtained in the same manner as in Example 1 except that N, N′-diisopropylcarbodiimide was used as the carbodiimide compound and the content in PET was changed as shown in Table 1.

Example 7, Comparative Example 5
Polyester filaments were obtained in the same manner as in Example 1 except that polypropylene having a melting point of 163 ° C. was used as the polyolefin and the content in PET was changed as shown in Table 1.

Comparative Example 1
The same as in Example 1 except that the PET pellet obtained by solid phase polymerization in the same manner as in Example 1 contains only the same carbodiimide compound as in Example 1 so that the content becomes 1.5% by mass. Polyester filaments were obtained by melt spinning and stretching by the method described above.

Comparative Example 6
The same method as in Example 2 except that prepolymer pellets having a relative viscosity of 1.34 and a carboxyl end group amount of 30.9 eq / t obtained in the same manner as in Example 1 were used without performing a solid phase polymerization reaction. A polyester filament was obtained.

  Table 1 shows the characteristic values and evaluation results of the polyester filaments obtained in Examples 1 to 7 and Comparative Examples 1 to 6.

  As is clear from Table 1, the polyester filaments obtained in Examples 1 to 7 had a small decrease in strength after wet heat treatment, high strength retention, and excellent moisture heat resistance. In addition, the strength before wet heat treatment was high, the yarn physical properties were excellent, the surface smoothness was excellent, and the yarn production was good.

On the other hand, since the polyester filament of Comparative Example 1 did not contain polyolefin, the polyester filament of Comparative Example 3 did not contain a carbodiimide compound, and both were inferior in moisture and heat resistance. Since the polyester filament of Comparative Example 2 contained too much polyolefin, the surface was rough, the surface smoothness was inferior, and the yarn production was poor. Since the polyester filament of Comparative Example 4 contained too much carbodiimide compound, the yarn filament was inferior. Since the polyester filament of Comparative Example 5 used a polyolefin having a low melting point, the strength retention was low and the heat-and-moisture resistance performance was poor. In Comparative Example 6, since the relative viscosity of the raw material polyester was low and the relative viscosity of the obtained polyester filament was low, the strength was low and the wet heat resistance performance was poor.

Claims (3)

A filament comprising a polyester containing 0.1 to 20% by mass of a polyolefin having a melting point of 150 ° C. or higher and 0.1 to 4.0% by mass of a carbodiimide compound, having a relative viscosity of 1.40 or more and a carboxyl end group amount Is a polyester filament, characterized in that it is 15.0 eq / t or less. The polyester filament according to claim 1, wherein the carbodiimide compound is N, N'-bis (2,6-diisopropylphenyl) carbodiimide. The polyester filament according to claim 1 or 2, wherein the polyolefin having a melting point of 150 ° C or higher is polymethylpentene.