JP2011012154A - Polyester resin and binder fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester resin having excellent crystallinity in spite of low melting point, producible in high operability and suitable for using in various adhesive uses including a binder fiber.SOLUTION: The polyester resin comprises 70-95 mol% of terephthalic acid and ≥5 mol% of isophthalic acid in the total acid component and 20-80 mol% of ethylene glycol and ≥20 mol% of butanediol in the glycol component, has a melting point of 140-190°C and a glass transition temperature of ≥45°C, contains 0.01-5.0 mass% of a crystal nucleating agent and has a temperature lowering crystallization peak determined by DSC and the peak satisfying formula (1): b/a≥0.01 (mW/mg×°C).

Description

  The present invention relates to a polyester resin having crystallinity and having a glass transition temperature of 45 ° C. or higher and which can be suitably used for a binder fiber.

   In recent years, polyester nonwoven fabrics have been widely used in the clothing field, sanitary material field, industrial material field, and the like. And in such a polyester nonwoven fabric, in order to heat-bond fibers, a heat-adhesive binder fiber made of a copolyester having a low softening point is used.

  As copolymer polyesters having a low softening point for heat-adhesive polyester binder fibers, amorphous copolymer polyesters such as copolymer polyesters composed of terephthalic acid, isophthalic acid and ethylene glycol are generally widely used.

  However, when non-crystalline or low-crystalline copolymer polyester is made into a non-woven fabric with a general-purpose heat treatment machine and held at a high temperature, the strength is lowered or the non-woven fabric is deformed under a load. was there.

  Patent Document 1 describes a copolyester for binder fibers having crystallinity and having a melting point of about 160 ° C. and excellent heat resistance. However, the copolymerized polyester of Patent Document 1 has a low glass transition temperature of about 30 ° C., and when the polymerized polyester is discharged into a strand shape to form a chip, it becomes difficult to cool the polymer below the glass transition temperature. Insufficient cooling and solidification may cause problems in operability such as sticking of polyester to the cutter blade and fusion between strands.

  Patent Document 2 also proposes a copolyester exhibiting a clear crystal melting point by using a crystal nucleating agent. When a polymer having a clear crystal melting point is used to form a binder fiber, the nonwoven fabric obtained does not decrease in strength even when held at a high temperature, and a nonwoven fabric with good heat resistance can be obtained.

  However, since the copolyester described in Patent Document 2 also has a low glass transition temperature of the polyester, in the same manner as described above, the polyester is fixed to the cutter blade, and fusion between strands occurs. A problem sometimes occurred.

Japanese Patent Application Laid-Open No. 09-12663 Japanese Patent Laid-Open No. 2008-222737

  The present invention solves the above-mentioned problems, and is a copolyester having crystallinity while having a low melting point. When the polymerized polyester is discharged into a strand shape to form a chip. An object of the present invention is to provide a polyester resin that can sufficiently cool and solidify a polymer, does not cause adhesion of polyester to a cutter blade and does not cause fusion between strands, and can be chipped with good operability. .

The present inventor has reached the present invention as a result of studies to solve the above-mentioned problems.
That is, the gist of the present invention is the following (A) and (B).
(I) Among all acid components, terephthalic acid is composed of 70 to 95 mol%, isophthalic acid is composed of 5 to 30 mol%, glycol component is composed of ethylene glycol 20 to 80 mol%, butanediol 20 to 80 mol%, and melting point 140 to 190 ° C., glass transition temperature of 45 ° C. or more, containing 0.01 to 5.0% by mass of a crystal nucleating agent, and a DSC curve showing temperature-fall crystallization determined by DSC satisfies the following formula (1) A polyester resin characterized by.
b / a ≧ 0.01 (mW / mg · ° C.) (1)
Note that a is the temperature A1 (° C.) of the intersection between the tangent line and the baseline having the maximum inclination in the DSC curve indicating the temperature-falling crystallization, and the temperature A2 (° C.) of the intersection of the tangent line and the baseline having the minimum inclination. B) is the difference (B1-B2) between the baseline heat quantity B1 (mW) and the peak top heat quantity B2 (mW) at the peak top temperature (mg) The value divided by.
(B) A binder fiber in which the polyester resin described in (a) is arranged on the fiber surface.

  Since the polyester resin of the present invention has a low melting point but has crystallinity and a glass transition temperature of 45 ° C. or higher, when the polymerized polyester is discharged into a strand to form a chip, the polymer is sufficient. It can be cooled and solidified, and the polyester can be fixed to the cutter blade and the inter-strand fusion does not occur, and chips can be formed with good operability. And since the polyester resin of the present invention is suitable as a binder fiber and can be melted by heat treatment at a low temperature, the use of the binder fiber of the present invention hardly causes a decrease in strength even in a high temperature atmosphere, and is heat resistant. It is possible to obtain a nonwoven fabric excellent in properties.

It is an example of the DSC curve which shows the temperature-fall crystallization calculated | required from DSC in the polyester resin of this invention.

Hereinafter, the present invention will be described in detail.
The polyester resin of the present invention is a copolyester mainly composed of terephthalic acid and isophthalic acid, ethylene glycol and butanediol.

  Of all the acid components, terephthalic acid needs to be 70 to 95 mol%, and 80 to 95 mol% is preferable. Further, the copolymerization amount of isophthalic acid needs to be 5 to 30 mol%, and preferably 5 to 20 mol%.

  If terephthalic acid is less than 70 mol% or isophthalic acid exceeds 30 mol%, the crystallinity of the polyester will be lowered, so that the formula (1) described later cannot be satisfied. On the other hand, when the terephthalic acid exceeds 95 mol% or the isophthalic acid is less than 5 mol%, the melting point of the polyester becomes high and exceeds 190 ° C.

  In addition, as a dicarboxylic component other than terephthalic acid and isophthalic acid, phthalic acid, adipic acid, sebacic acid, dimer acid, 2,6-naphthalenedicarboxylic acid, 4,4′-biphenyl, as long as the effects are not impaired. Dicarboxylic acid or the like can be used.

  As a glycol component, it is necessary to make ethylene glycol into 20-80 mol%, and it is preferable to set it as 40-80 mol% especially. Moreover, it is necessary to make butanediol into 20-80 mol%, and it is preferable to set it as 20-60 mol% especially.

  If the ethylene glycol is less than 20 mol% or the butanediol exceeds 80 mol%, the crystallinity of the polyester becomes low, and the later-described formula (1) cannot be satisfied. On the other hand, when the ethylene glycol exceeds 80 mol% or the butanediol is less than 20 mol%, the melting point of the polyester becomes high and exceeds 190 ° C.

  As a glycol component other than ethylene glycol and butanediol, neopentyl glycol, 1,4-butanediol, 1,5-pentamethylenediol, diethylene glycol, dimer diol, bisphenol A or bisphenol, as long as the effect is not impaired. An ethylene oxide adduct of S can be used.

  The polyester resin of the present invention has a melting point of 140 to 190 ° C, and preferably 150 to 180 ° C. When the melting point exceeds 190 ° C., it is necessary to increase the heat treatment temperature when melted by heat treatment to form an adhesive component, and a general-purpose heat treatment apparatus cannot be used, and the cost increases. On the other hand, in the case of a copolymer polyester composed of four components as described above, if an attempt is made to obtain one having a melting point of less than 140 ° C., it becomes amorphous, making it difficult to satisfy the formula (1) described below.

  Furthermore, the polyester resin of the present invention needs to have a glass transition temperature of 45 ° C. or higher, preferably 45 to 75 ° C., more preferably 50 to 70 ° C. When the glass transition temperature is less than 45 ° C., when the resin is made into chips and stored and transported, the frequency of occurrence such as fusion to an apparatus or blocking between chips becomes unfavorable. Further, when melt spinning, fusion between single yarns is likely to occur during spinning, and operability is deteriorated. On the other hand, in the case of a copolymer polyester composed of the above four components, the upper limit of the glass transition temperature is about 75 ° C.

The polyester resin of the present invention has crystallinity, and the DSC curve showing the temperature-falling crystallization obtained from DSC satisfies the following formula (1), and in particular, b / a ≧ 0 .05 is preferred. On the other hand, the larger b / a is, the better the crystallinity at the time of temperature drop is. However, in order to achieve the target effect in the present invention, it is preferable to set b / a to 0.3 or less.
b / a ≧ 0.01 (mW / mg · ° C.) (1)

  The DSC curve showing the melting point of the polyester resin in the present invention and the temperature-falling crystallization obtained from DSC is a temperature range of −20 ° C. to 250 ° C. in a nitrogen stream using a differential scanning calorimeter (Diamond DSC) manufactured by PerkinElmer. Measured at a rate of temperature rise (fall) of 20 ° C./min and a sample amount of 2 mg.

  Said b / a is calculated | required from the DSC curve which shows the temperature-fall crystallization calculated | required from DSC. As shown in FIG. 1, in the DSC curve of the polyester resin, a is the temperature A1 (° C.) at the intersection of the tangent line and the base line where the slope is maximum in the DSC curve indicating the temperature drop crystallization, and the slope is the minimum. The difference (A1−A2) between the temperature A2 (° C.) at the intersection of the tangent line and the baseline, and b is the heat amount B1 (mW) of the baseline and the heat amount B2 (mW) of the peak top at the peak top temperature. It is a value obtained by dividing the difference (B1-B2) by the sample amount (mg).

  b / a is an index representing the crystallinity when the temperature is lowered, and the higher the b / a value, the faster the crystallization rate, and vice versa, the closer to 0, the slower the crystallization rate. When b / a is less than 0.01 (mW / mg · ° C.), the crystallization rate is low, and therefore, blocking tends to occur in polyester chip formation, storage / transport and drying processes.

  b / a can be made into the range prescribed | regulated by this invention by making the copolymerization composition of a polyester resin into the above-mentioned 4 component system, and containing a crystal nucleating agent suitable amount.

  The polyester resin of the present invention contains 0.01 to 5.0% by mass of a crystal nucleating agent, preferably 0.5 to 3.5% by mass. When the content of the crystal nucleating agent is less than 0.01% by mass, the crystallization speed at the time of temperature reduction cannot be improved, and it becomes difficult to satisfy the above-described formula (1). On the other hand, if it exceeds 5.0% by mass, the content of the crystal nucleating agent is excessively increased, and the operability at the time of spinning and drawing is deteriorated when fiberizing.

As the crystal nucleating agent, inorganic fine particles, polyolefin, sulfate and the like can be used. Among these, inorganic fine particles are preferably used, and inorganic fine particles having an average particle size of 3.5 μm or less or a specific surface area of 15 m ² / g or more are preferably used.
As the inorganic fine particles, those mainly composed of silicon oxide such as talc are preferable. When the above average particle diameter or specific surface area is not satisfied, the function as a crystal nucleus is poor, and the polyester resin is as described above (1 It is difficult to satisfy the formula.

  The polyester resin of the present invention is preferably used as a binder fiber because it has crystallinity while having a low melting point, and has an intrinsic viscosity of 0.6 to 1.2. Among these, 0.8 to 1.0 is preferable. When the intrinsic viscosity is less than 0.6, various physical, mechanical, and chemical properties are inferior, and spinnability is impaired when a fiber is used. On the other hand, when the intrinsic viscosity exceeds 1.2, the melt viscosity becomes high, so that extrusion becomes difficult, and when the fiber is made, if the spinning temperature is raised to lower the melt viscosity, the thermal decomposition of the polyester becomes remarkable. Tends to be difficult to spin.

The polyester resin of the present invention can be produced by a conventional method. That is, the polyester resin composition of the present invention can be produced by subjecting a dicarboxylic acid component and a diol component to an esterification reaction or a transesterification reaction and performing a polycondensation reaction.
Specifically, the polycondensation reaction is usually performed under a reduced pressure of about 0.01 to 10 hPa at a temperature of 220 to 280 ° C. until a product having a predetermined intrinsic viscosity is obtained. The polycondensation reaction is carried out in the presence of a catalyst. As a catalyst, conventionally used metals such as antimony, germanium, tin, titanium, zinc, aluminum, magnesium, potassium, calcium, sodium, manganese and cobalt are commonly used. In addition to the compounds, organic sulfonic acid compounds such as sulfosalicylic acid and o-sulfobenzoic anhydride can be used.

  In addition, various additives such as phosphoric acid ester compounds and hindered phenol compounds, stabilizers such as phosphate compounds and hindered phenol compounds, cobalt compounds, fluorescent whitening agents, color tone improvers such as dyes, and titanium dioxide. One or more kinds of various additives such as a matting agent, a plasticizer, a pigment, an antistatic agent, a flame retardant, and an easy dyeing agent may be added.

  When the polyester reaches a predetermined intrinsic viscosity in the polycondensation reaction, it is discharged into a strand shape, cooled and solidified, and cut to form a chip.

Next, the binder fiber of the present invention is obtained by arranging the polyester resin of the present invention on the fiber surface, and the polyester resin of the present invention occupies a part or all of the fiber surface.
That is, it may be a composite fiber made of the polyester resin of the present invention and another resin, or a single type fiber made of only the polyester resin of the present invention.
When the composite fiber is used, it is preferable to use a composite fiber such as a core-sheath type, a side-by-side type, or a sea-island type. As other components in the case of the composite fiber, polyethylene terephthalate (PET), polybutylene terephthalate, and high melting point polyester mainly composed of these are preferably used. As the composite form of the composite fiber, the core-sheath type is preferable from the viewpoint of spinnability and fiber properties.

When obtaining a binder fiber of a composite fiber using such a polyester resin of the present invention, melt spinning by a conventional method using a composite spinning apparatus, and the resulting undrawn yarn is converged in a tow shape and then drawn. Then, after crimping as necessary, it is cut into short fibers.
Furthermore, when manufacturing a nonwoven fabric using this binder fiber, after mixing this with the short fiber (main fiber) which consists of polyethylene terephthalate etc., it forms in a web, Tm- (Tm + 30 degreeC) [Tm is the polyester resin of this invention The polyester resin of the present invention is melted and the main fibers are spot-bonded to obtain a nonwoven fabric.

Next, the present invention will be specifically described using examples. The measurement and evaluation methods for various characteristic values in the examples are as follows.
(A) Average particle size of inorganic fine particles The average particle size of the sample in ethylene glycol was measured using a particle size distribution analyzer (SALD-2000) manufactured by Shimadzu Corporation.
(B) Specific surface area of inorganic fine particles Measured by BET method.
(C) Intrinsic viscosity [η]
Measurement was carried out based on a conventional method under the conditions of a sample concentration of 0.5% by mass and a temperature of 20 ° C. using an equal mass mixture of phenol and ethane tetrachloride as a solvent.
(D) Melting | fusing point of polyester resin, DSC curve which shows temperature-fall crystallization calculated | required from DSC It measured by the said method.
(E) Polymer composition of polyester resin The obtained polyester resin was dissolved in a mixed solvent having a volume ratio of deuterated hexafluoroisopropanol and deuterated chloroform of 1/20, and the mixture was applied to a LA-400 NMR apparatus manufactured by JEOL Ltd. 1H-NMR was measured and determined from the integrated intensity of the proton peak of each copolymer component in the obtained chart.
(f) Operability 1. Chip formation When the obtained polyester resin is chipped with USG-600 type cutter made by AUTOMATIK, two or more chips are fused due to the wrapping of polyester around the feed roller or cutter blade and the fusion between strands. If the operation of the cutter is interrupted, ×, problems such as fusing will occur, but if the chip can be formed without interrupting the operation of the cutter, Δ, the chip can be formed without causing problems due to fusing The case was marked with ○.
2. Chip blocking When the chip storage / transport and drying process produces a block-like lump or a fusion product on the wall that does not collapse even when touched by hand, although there is a block-like lump or deposit on the wall △ indicates that the problem is solved by touching with a hand or applying an impact to the wall surface with a hammer or the like, and ◯ indicates that no block-like lump or fusion to the wall surface occurs.
(g) Nonwoven fabric strength The obtained short fibers are used as binder fibers, PET fibers (fineness 2d, fiber length 51 mm) are used as the main fibers, the two companies are mixed at a mass ratio of 1: 1, and then the web is formed. Then, a non-woven fabric having a basis weight of 40 g / m ² was obtained by performing a heat bonding treatment at 180 ° C. for 100 seconds and a heat-resistant heat treatment at 100 ° C. for 5 minutes.
About the obtained nonwoven fabric, the nonwoven fabric strength was measured as follows. Using a UTM-4 type Tensilon manufactured by Orientec Co., a nonwoven fabric having a width of 2.5 cm and a length of 15 cm was stretched and cut under the conditions of a tensile speed of 10 cm / min and a gripping interval of 10 cm, and the maximum point strength was read. A nonwoven fabric strength of 3000 g or more was considered acceptable.
(h) Strength retention of nonwoven fabric (heat resistance of nonwoven fabric)
The nonwoven fabric strength in an atmosphere at 100 ° C. was measured by the above-described nonwoven fabric strength measurement method, and the strength retention rate for the nonwoven fabric strength at room temperature [measured in (g)] was determined. If the strength retention was 60% or more, the heat resistance was evaluated as good.

Example 1
A slurry having a molar ratio of terephthalic acid (TPA) to ethylene glycol (EG) (TPA / EG) 1 / 1.6 is continuously supplied to the esterification reactor, under conditions of a temperature of 250 ° C. and a pressure of 0.2 MPa. The oligomer was reacted for a residence time of 8 hours to obtain an esterification reaction rate of 95%. In another esterification can, a slurry of isophthalic acid (IPA) and ethylene glycol (EG) molar ratio (IPA / EG) 1 / 3.1 was charged, and the esterification reaction was carried out at a temperature of 200 ° C. for 3 hours. A reaction solution of ethylene glycol was obtained.
Charge 45.2 kg of oligomer of terephthalic acid and ethylene glycol to the polymerization reactor, then 8.1 kg of reaction solution of isophthalic acid and ethylene glycol, 17.4 kg of butanediol (BD), 34 mass of titanium dioxide as matting agent EG slurry containing 0.5% of EG slurry, 3.5 kg of EG slurry containing 10% by mass of talc having an average particle size of 1.0 μm and a specific surface area of 35 m ² / g as a crystal nucleating agent, and tetrabutyl titanate as a polycondensation catalyst. 0.9 kg of EG solution containing 4% by mass was added, the reactor was decompressed, and after 60 minutes, a polymerization reaction was carried out for 4 hours at a final pressure of 0.9 hPa and a temperature of 240 ° C. The obtained polyester resin was dispensed into strands by a conventional method to form chips.

  Next, in order to obtain a composite fiber using the obtained polyester resin chip as a sheath component and polyethylene terephthalate having an intrinsic viscosity [η] of 0.68 as a core component, Using a spinneret of several 225, spinning was performed at a composite ratio (volume ratio) of 1: 1 at a spinning temperature of 270 ° C., a discharge rate of 228 g / min, and a spinning speed of 700 m / min. The spun yarn was cooled with cold air at 18 ° C. and taken out to obtain an undrawn yarn. The obtained undrawn yarn is bundled and made into a tow of 100,000 dtex, drawn at a draw ratio of 3.3 times and a draw temperature of 60 ° C., then crimped with a push-in crimper, and then cut into a length of 51 mm. Thus, a short fiber (binder fiber) having a single yarn fineness of 4 dtex was obtained.

Example 2
A polyester resin and short fibers were obtained in the same manner as in Example 1 except that 7.0 kg of EG slurry containing 10% by mass of talc was added as a crystal nucleating agent.

Example 3
A polyester resin and short fibers were obtained in the same manner as in Example 1 except that 7.0 kg of EG slurry containing 10% by mass of talc having an average particle size of 3.2 μm and a specific surface area of 25 m ² / g was added as a crystal nucleating agent. .

Example 4, Comparative Examples 2-3, 7
A polyester resin and short fibers were obtained in the same manner as in Example 1 except that the amount of the reaction solution of terephthalic acid and ethylene glycol and the reaction solution of isophthalic acid and ethylene glycol was changed so that the polymer composition shown in Table 1 was obtained. It was.

Example 5, Comparative Example 4
A polyester resin and short fibers were obtained in the same manner as in Example 1 except that the amount of butanediol was changed and the polymer composition shown in Table 1 was obtained.

Comparative Example 1
A polyester resin and short fibers were obtained in the same manner as in Example 1 except that the crystal nucleating agent was not added.

Comparative Example 5
The same operation as in Example 1 was carried out except that 0.018 kg of EG slurry containing 10% by mass of talc was added as a crystal nucleating agent.

Comparative Example 6
Except for charging 42.7 kg of an oligomer of terephthalic acid and ethylene glycol into the polymerization reactor, and subsequently charging 1.0 kg of ε-caprolactone and 14.6 kg of butanediol in place of the reaction solution of isophthalic acid and ethylene glycol, A polyester resin and short fibers were obtained in the same manner as in Example 1.

  Table 1 shows the characteristic values of the obtained polyester resin, the operability during chip formation, and the evaluation results of the nonwoven fabric.

As is clear from Table 1, the polyester resins of Examples 1 to 5 satisfy the formula (1), are excellent in crystallinity, have a melting point in the range of 140 to 190 ° C., and are chipped. The operability in the process was also good. Moreover, the nonwoven fabric using the obtained short fiber had high nonwoven fabric strength and strength retention, and had good performance.
On the other hand, since the polyester resin of Comparative Example 1 did not contain a crystal nucleating agent, the amount of the crystal nucleating agent was too small for the polyester resin of Comparative Example 5, so that the polyester resin of Comparative Example 2 contained too much isophthalic acid. Therefore, none of them satisfied the formula (1) and did not have crystallinity. For this reason, it is inferior to the operativity in a chip-forming process, and chip blocking occurred. Since the polyester resin of Comparative Example 3 has a small amount of terephthalic acid copolymerization, the polyester resin of Comparative Example 4 has a low butanediol copolymerization amount. Since the polyester resin of Comparative Example 6 did not contain isophthalic acid and had a composition containing ε-caprolactone, the glass transition temperature was low, and chip-to-chip blocking occurred after chip formation. Since the polyester resin of Comparative Example 7 contained too much isophthalic acid, it did not satisfy the formula (1) and did not have crystallinity. Further, the glass transition temperature was less than 45 ° C., making it difficult to form chips, and blocking between chips also occurred.

Claims (3)

Among all acid components, terephthalic acid is composed of 70 to 95 mol%, isophthalic acid is composed of 5 to 30 mol%, glycol component is composed of ethylene glycol 20 to 80 mol%, butanediol 20 to 80 mol%, and melting point 140 to 190 ° C., glass transition temperature of 45 ° C. or higher, containing 0.01 to 5.0% by mass of a crystal nucleating agent, and a DSC curve showing temperature-fall crystallization determined by DSC satisfies the following formula (1): Characteristic polyester resin.
b / a ≧ 0.01 (mW / mg · ° C.) (1)
Note that a is the temperature A1 (° C.) of the intersection between the tangent line and the baseline having the maximum inclination in the DSC curve indicating the temperature-falling crystallization, and the temperature A2 (° C.) of the intersection of the tangent line and the baseline having the minimum inclination. B) is the difference (B1-B2) between the baseline heat quantity B1 (mW) and the peak top heat quantity B2 (mW) at the peak top temperature (mg) The value divided by. The polyester resin according to claim 1, wherein the crystal nucleating agent is an inorganic fine particle having an average particle diameter of 3.5 µm or less or a specific surface area of 15 m ² / g or more. Binder fiber which arranged the polyester resin of Claim 1 or 2 on the fiber surface.