JP2009275319A - Flame-retardant polyester composite staple fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flame-retardant polyester composite staple fiber which can be processed at a low temperature and can give a product, such as a nonwoven structure, having good dimensional stability and excellent texture, flexibility, mechanical characteristics and flame retardancy, especially when used as a binder fiber and thermally adhered. <P>SOLUTION: Provided is the flame-retardant polyester composite staple fiber formed from: a polyester A which includes a dicarboxylic acid component containing terephthalic acid as a main component and a diol component containing 1,6-hexanediol in an amount of ≥50 mol%, contains a crystal-nucleating agent in an amount of 0.01 to 5.0 mass%, and has a melting point of 100 to 150°C and a DSC curve satisfying an expression (1) of b/a≥0.05 (mW/mg×°C) and showing temperature-falling crystallization determined by DSC; and a polyester B having a low melting point and copolymerized with a phosphorous compound. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is a fiber in which polyester A having a low melting point and excellent crystallinity occupies at least a part of the fiber surface, can be obtained with good operability, and is particularly suitable for use as a binder fiber. The present invention relates to a flame-retardant polyester composite short fiber having thermal adhesiveness and flame retardancy.

  Synthetic fibers, especially polyester fibers, are indispensable as clothing and industrial materials due to their excellent dimensional stability, weather resistance, mechanical properties, durability, and recyclability. Many polyester fibers are used.

  In recent years, non-woven structures in which constituent fibers are bonded using binder fibers have been proposed in automotive interior materials and the like. Since these nonwoven structures are mainly composed of polyester fibers, it is preferable to use fibers composed of polyester polymers as binder fibers for the purpose of adhesion from the viewpoint of recycling.

  Examples of such binder fibers include core-sheath type composite short fibers having polyethylene terephthalate as a core and a polyethylene terephthalate copolymer copolymerized with an isophthalic acid component as a sheath. Since this fiber is composed of a high melting point core and a low melting point sheath, the fiber shape is maintained without melting the core during heat treatment, and only the sheath is melted, thereby providing excellent strength. A nonwoven fabric can be obtained.

  However, since the polyethylene terephthalate copolymer obtained by copolymerizing the isophthalic acid component in the sheath is amorphous and does not exhibit a clear crystal melting point, softening starts at a temperature above the glass transition point. In addition, when producing short fibers using a polymer that does not exhibit a clear crystal melting point, if the heat treatment temperature is 100 ° C. or higher in the drawing / heat treatment step, the fibers are melted and stuck, making it difficult to implement. For this reason, the drawing and heat treatment steps are performed at a low temperature, and the obtained short fibers have a high thermal shrinkage rate and a large shrinkage during thermal bonding.

  And the product which used such a short fiber as a binder fiber had bad dimensional stability, and when it was used in a high temperature atmosphere, the problem that adhesive strength fell and it deform | transformed had arisen.

  As a solution to the above problem, Patent Document 1 discloses a core-sheath type composite fiber. This fiber has a core sheath in which polyethylene terephthalate is disposed in the core portion and a polyester copolymer obtained by copolymerizing a terephthalic acid component, an aliphatic lactone component, an ethylene glycol component, and a 1,4-butanediol component is disposed in the sheath portion. Type composite fiber.

  In this composite fiber, the sheath copolymer is crystalline and has a clear melting point. Therefore, the drawing and heat treatment steps for obtaining the short fiber can be performed at a high temperature, and a short fiber having a low heat shrinkage rate is obtained. be able to. For this reason, the nonwoven structure which is excellent in dimensional stability without shrinkage | contraction in the heat-bonding process, and excellent in heat resistance when used in a high temperature atmosphere can be obtained. However, this copolyester has a melting point in the range of 150 to 200 ° C. and is not yet a low melting point region, and it is necessary to increase the processing temperature when thermally bonding, and also from the viewpoint of cost. It was disadvantageous.

In addition, in automobile interior materials and interior applications, it is also demanded that fiber products obtained using binder fibers have flame retardancy, which gives good flame retardancy to textile products. There is a need for binder fibers that can be used.
JP 2006-118066 A

  The present invention solves the above-described problems, and can be produced with good operability by a normal manufacturing apparatus. Particularly when used as a binder fiber, it can be processed at a low temperature when thermally bonded. It is a technical problem to provide a flame-retardant polyester composite short fiber capable of obtaining a product such as a nonwoven structure excellent in formation, flexibility, mechanical properties, and flame retardancy with good dimensional stability. To do.

The inventors of the present invention have arrived at the present invention as a result of studies to solve the above problems.
That is, the present invention comprises a dicarboxylic acid component mainly composed of terephthalic acid and a diol component of 1,6-hexanediol of 50 mol% or more, and contains 0.01 to 5.0% by mass of a crystal nucleating agent. The melting point (TmA) is 100 to 150 ° C., and the DSC curve indicating the temperature-falling crystallization obtained from DSC satisfies the following formula (1): the melting point (TmA) of the polyester A and the melting point or flow starting temperature ( TmB) is a composite fiber composed of polyester B having a difference (TmB-TmA) of + 5 ° C. or less and a phosphorus compound copolymerized, and polyester A is the fiber surface in the cross-sectional shape of a single yarn Flame retardant, characterized in that it is arranged to occupy at least a part of the fiber, the phosphorus atom content in the fiber is 2000-15000 ppm, and the fiber length is 1-100 mm It is an gist polyester composite staple fiber.
b / a ≧ 0.05 (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.

  Since the flame-retardant polyester composite short fiber of the present invention has a low melting point and is excellent in crystallinity, particularly polyester A having a high crystallization rate when the temperature is lowered is arranged so as to occupy at least a part of the fiber surface. In the spinning process, there is no welding between single yarns, and in the drawing and heat treatment processes, heat treatment can be performed at a high temperature, so that the dry heat shrinkage can be reduced. When the flame-retardant polyester composite short fiber of the present invention is used as a binder fiber, polyester A can be melted at a low temperature during the thermal bonding treatment to be an adhesive component, which is advantageous in terms of cost, Excellent adhesion. Thus, by using the flame-retardant polyester composite short fiber of the present invention as a binder fiber, it is possible to obtain a product such as a nonwoven fabric that can be used for various applications with high dimensional stability.

  Furthermore, since the flame-retardant polyester composite short fiber of the present invention uses polyester B having a low melting point in which a phosphorus compound is copolymerized with polyester A, an adhesive component having flame retardancy when melted by thermal bonding treatment Thus, it is possible to impart good flame retardancy to the obtained product such as a nonwoven fabric.

  Hereinafter, the present invention will be described in detail. The flame-retardant polyester composite short fiber of the present invention is composed of polyester A and polyester B, and is a composite fiber in which polyester A occupies at least a part of the fiber surface.

  That is, the composite short fiber of the present invention may be a multifilament or a monofilament, but in a cross-sectional shape of a single yarn (a cross-sectional shape cut perpendicularly along the fiber axis direction), the polyester A has at least a part of the fiber surface. Occupies. Examples of such a shape include a side-by-side type, an eccentric core-sheath type, and a multi-layer type. Among them, in a cross-sectional shape of a single yarn, polyester A is a sheath and polyester B is a core. The shape is preferred.

  First, polyester A will be described. Polyester A is a copolyester having a melting point of 100 to 150 ° C. composed of a dicarboxylic acid component containing terephthalic acid as a main component and a diol component of 1,6-hexanediol of 50 mol% or more.

  Polyester A has a melting point (TmA) of 100 to 150 ° C, preferably 110 to 140 ° C. When TmA is less than 100 ° C., a product such as a nonwoven fabric obtained using the composite short fiber of the present invention is inferior in thermal stability (heat resistance) when used in a high temperature atmosphere. On the other hand, if the temperature exceeds 150 ° C., it is necessary to increase the heat bonding processing temperature when obtaining the product, which is inferior in workability and economy. Further, it is not preferable because the quality and texture of the product obtained by the heat treatment are impaired.

  Polyester A has terephthalic acid as a main component as a dicarboxylic acid component, and terephthalic acid (hereinafter referred to as TPA) is preferably 60 mol% or more, more preferably 80 mol% or more. If the TPA is less than 60 mol%, the melting point of the polymer is not within the scope of the present invention, and the crystallinity tends to be lowered, which is not preferable.

  In addition, as copolymerization components other than TPA, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, dodecanedicarboxylic acid, 1,3-cyclobutanedicarboxylic acid are used as long as the effects are not impaired. Saturated aliphatic dicarboxylic acids exemplified by acids, 1,4-cyclohexanedicarboxylic acid, dimer acids and the like, or ester-forming derivatives thereof, unsaturated aliphatic dicarboxylic acids exemplified by fumaric acid, maleic acid, itaconic acid and the like Aromatic dicarboxylic acids exemplified by these ester-forming derivatives, phthalic acid, isophthalic acid, 5- (alkali metal) sulfoisophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-biphenyldicarboxylic acid, etc. These ester-forming derivatives can be used.

  As the diol component, 1,6-hexanediol (hereinafter referred to as HD) is 50 mol% or more, and as other components, ethylene glycol (hereinafter referred to as EG) or 1,4-butanediol (hereinafter referred to as HD). BD) is preferably used. In the diol component, HD is 50 mol% or more, and preferably 60 to 95 mol%. When HD is less than 50 mol%, the melting point exceeds 150 ° C.

  When EG or BD is used together with HD as the diol component, EG or BD is preferably 5 to 50 mol%, more preferably 5 to 40 mol% in the diol component.

  Furthermore, as a copolymer component other than HD, EG and BD, the diol component is 1,2-propylene glycol, 1,3-propylene glycol, diethylene glycol, triethylene glycol, tetraethylene as long as the characteristics are not impaired. Exemplified as glycol, 1,4-butylene glycol, 1,5-pentanediol, neopentyl glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, polyethylene glycol, polytrimethylene glycol, polytetramethylene glycol Aliphatic glycol, hydroquinone, 4,4′-dihydroxybisphenol, 1,4-bis (β-hydroxyethoxy) benzene, bisphenol A, 2,5-naphthalenediol, ethylene oxide Can be used aromatic glycols exemplified such as glycols de was added.

  And polyester A contains 0.01-5.0 mass% of crystal nucleating agents, and it is preferable to contain 0.5-3.0 mass% especially.

  Polyester A has crystallinity due to the copolymer composition as described above, but can contain a crystal nucleating agent to improve the crystallization rate during cooling, which will be described later. The expression (1) to be satisfied can be satisfied. And, when the polyester A is made into a fiber, it is possible to heat-treat at a high temperature in the drawing and heat treatment process without causing welding between the single yarns in the melt spinning process. can do.

  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 the polyester A cannot satisfy the formula (1) described later. On the other hand, if it exceeds 5.0 mass%, the content of the crystal nucleating agent is excessively increased, and the operability during spinning and stretching is deteriorated. In addition, the deterioration in operability increases the variation in yarn quality and increases the dry heat shrinkage of the fibers.

As the crystal nucleating agent, it is preferable to use inorganic fine particles, polyolefin, sulfate or the like. As the inorganic fine particles, those mainly composed of silicon oxide such as talc are preferable, and inorganic fine particles having an average particle size of 3.0 μm or less or a specific surface area of 15 m ² / g or more are preferably used. When the average particle diameter or specific surface area is not satisfied, the function as a crystal nucleus is poor, and it is difficult for the polyester A to satisfy the formula (1) described later.

  The polyolefin contained as a crystal nucleating agent melts in the reaction system, so the shape is not particularly limited. For example, a chip-like one having a particle size of about 2 mm or a wax-like one having a particle size of several μm It may be.

  Examples of polyolefins include olefin homopolymers such as polyethylene, polypropylene, poly-1-butene, polymethylpentene, and polymethylbutene, and propylene / ethylene random copolymers. Polyethylene, polypropylene, poly-1- Butene and propylene / ethylene random copolymers are particularly preferred. In the case where the polyolefin is a polyolefin obtained from an olefin having 3 or more carbon atoms, it may be an isotactic polymer or a syndiotactic polymer.

  Examples of the sulfate to be contained as a crystal nucleating agent include lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, barium sulfate, calcium sulfate, and aluminum sulfate. And magnesium sulfate are preferred.

  As a method for adding these crystal nucleating agents, they may be added at an arbitrary stage when the polyester is produced in the form of powder or in the form of a diol slurry. For example, it may be added at the time of esterification or transesterification, or may be added at the stage of polycondensation reaction. Among these, in order to improve the effect as a crystal nucleating agent, it is preferable to add in a slurry state or a dissolved state in a glycol such as ethylene glycol.

  In addition, polyester A contains a stabilizer such as a phosphate ester compound and a hindered phenol compound, a cobalt compound, a fluorescent brightening agent, a color tone improver such as a dye, and a dioxide dioxide within a range not impairing the effects of the present invention. One or more kinds of various additives such as matting agents such as titanium, plasticizers, pigments, antistatic agents and dyeing agents may be added.

Polyester A has a DSC curve showing temperature-fall crystallization determined from DSC satisfying the following formula (1), and it is preferable that b / a ≧ 0.06 among them. On the other hand, the larger b / a, the better the crystallinity when the temperature is lowered. However, in order to achieve the intended effect of the present invention, b / a is preferably 0.5 or less.
b / a ≧ 0.05 (mW / mg · ° C.) (1)

  The DSC curve showing the melting temperature of polyester A 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 temperature rising (falling) rate of 20 ° C./min and a sample amount of 2 mg (mass of short fibers).

  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, a is the temperature A1 (° C.) of the intersection of the tangent line and the base line with the maximum inclination in the DSC curve indicating the temperature-falling crystallization, the tangent line and the base line with the minimum inclination. Is the difference (A1−A2) from the temperature A2 (° C.) at the intersection of the two, and b is the difference (B1−B2) between the baseline heat amount B1 (mW) and the peak top heat amount B2 (mW) at the peak top temperature. ) Divided 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 0.05 (mW / mg · ° C.), the crystallization rate is low, so that welding between single yarns occurs during melt spinning, and the spinning operability deteriorates. Further, when the heat treatment temperature in the drawing / heat treatment step is increased, the fibers are melted and glued, and heat treatment at a high temperature cannot be performed, so that a fiber having a low heat shrinkage rate cannot be obtained.

  As described above, b / a can be in the range specified in the present invention by setting the copolymer composition of polyester to a specific value and the content of the crystal nucleating agent in the above range. .

  Next, polyester B will be described. Polyester B is a copolyester in which a phosphorus compound is copolymerized, and the difference (TmB-TmA) between the melting point of polyester A (TmA) and the melting point or flow start temperature (TmB) of polyester B is + 5 ° C. or less. It will be.

  The flame-retardant polyester composite short fiber of the present invention is preferably used as a binder fiber, and it is preferable that both polyester A and polyester B are melted by thermal bonding treatment to form an adhesive component. And when obtaining fiber structures, such as a nonwoven fabric, it is preferable to use the other fiber which has melting | fusing point higher than the melting | fusing point of the polyester A as a main fiber.

  Polyester B is obtained by copolymerizing a phosphorus compound and contains a specific amount of phosphorus atoms in the composite fiber. Therefore, when polyester B melts and becomes an adhesive component, an appropriate amount of phosphorus atoms is present in the adhesive component. Being contained, the main fibers made of other fibers can be satisfactorily adhered, and it is possible to impart flame retardancy to fiber structures made of the main fibers (woven fabrics, non-woven fabrics, etc.) It is.

  Usually, the heat bonding treatment temperature is 10 ° C. higher than the melting point of the polyester A arranged on the fiber surface. In order to melt the polyester B at such a heat bonding treatment temperature, the polyester B The melting point or the flow starting temperature of the polyester A is preferably 5 ° C. or less, more preferably lower than the melting point of the polyester A.

  Therefore, the difference (TmB−TmA) between the melting point or flow start temperature (TmB) of polyester B and the melting point (TmA) of polyester A is set to + 5 ° C. or less. In addition, when TmB becomes too low, the spinning operability deteriorates, so that (TmA-TmB) is preferably 20 ° C. or higher.

  Furthermore, the melting point or flow start temperature (TmB) of polyester B is preferably 90 to 155 ° C, and more preferably 100 to 135 ° C.

  As the polyester B, those mainly composed of polyalkylene terephthalate such as polyethylene terephthalate (PET), polybutylene terephthalate, and polytrimethylene terephthalate are preferable. And in order to set it as the above melting | fusing point and flow start temperature, it is preferable to use what was copolymerized the following components.

  Examples of copolymer components include aromatic dicarboxylic acids such as isophthalic acid and 5-sulfoisophthalic acid, aliphatic dicarboxylic acids such as adipic acid, succinic acid, suberic acid, sebacic acid, and dodecanedioic acid, and ethylene glycol, propylene glycol, Aliphatic diols such as 1,4-butanediol and 1,4-cyclohexanedimethanol, and hydroxycarboxylic acids such as glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxypentanoic acid, hydroxyheptanoic acid and hydroxyoctanoic acid Examples thereof include aliphatic lactones such as acid and ε-caprolactone.

  Among them, the polyester B preferably has a melting point or flow starting temperature that is the same or lower than that of the polyester A, and is a copolymer polyester containing a TPA component and an EG component, and is preferably amorphous. The copolymer component is preferably an aromatic carboxylic acid component such as isophthalic acid or adipic acid, and the amount of copolymerization is preferably 25 to 40 mol%, particularly 27 to 35 mol, based on the total acid component. % Is more preferable. If the copolymerization amount is less than 25 mol%, the flow start temperature tends to be high, whereas if the copolymerization amount is more than 40 mol%, Tg tends to be low, and single yarn adhesion occurs during spinning, resulting in yarn forming properties It tends to get worse.

  By making polyester B amorphous, it becomes low in fluidity when melted by thermal bonding treatment, and polyester A becomes high in fluidity when melted because it is a crystalline polymer. By becoming a component, it has moderate flow characteristics, can bond main fibers (other fibers) uniformly and well, and can obtain a fiber product with high quality and excellent adhesiveness. Become. And since polyester B contains a flame retardant, when it is melted by thermal bonding treatment, it becomes an adhesive component having flame retardancy, and it becomes possible to impart flame retardancy to the resulting fiber product.

  Polyester B is obtained by copolymerizing a phosphorus compound as a flame retardant. Examples of phosphorus compounds include phosphate esters and derivatives thereof, phosphonic acids and derivatives thereof, phosphinic acids and derivatives thereof, and these can be used alone or in combination of two or more.

  Specific examples of phosphate esters and derivatives thereof include trimethyl phosphate, triethyl phosphate, and tripropyl phosphate. Specific examples of phosphonic acids and derivatives thereof include phenylphosphonic acid, dimethylphosphonic acid, and diethylphosphonic acid. Specific examples of phosphinic acid and its derivatives include phosphorane, a maleic acid adduct of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, an itaconic acid adduct, and the like. Moreover, the compound etc. which added ethylene carbonate to the reaction material of diphenylphosphine oxide and p-benzoquinone are mentioned.

  In polyester B, stabilizers, cobalt compounds, fluorescent brighteners, color tone improvers such as dyes, matting agents such as titanium dioxide, plasticizers, pigments, antistatic agents, and easy dyeing agents. One or two or more of these various additives may be added.

  The flame-retardant polyester composite short fiber of the present invention has a phosphorus atom content of 2000 to 15000 ppm, and preferably 4000 to 10000 ppm.

  When the content of phosphorus atoms in the fiber is less than 2000 ppm, the flame retardancy is insufficient. On the other hand, when the content exceeds 15000 ppm, it is necessary to increase the copolymerization amount of the phosphorus compound, and as a result, spinning becomes difficult. Physical properties such as fiber strength also decrease.

  The composite ratio (mass ratio) of polyester A and polyester B in the flame-retardant polyester composite short fiber of the present invention is preferably 20/80 to 80/20, and more preferably 30/70 to 70/30. Is preferred.

  The flame-retardant polyester composite short fiber of the present invention is a short fiber having a fiber length of 1 to 100 mm, and the fiber length is preferably 3 to 80 mm. When the fiber length is less than 1 mm, the fibers are fused or glued by heat at the time of cutting. When the fiber length exceeds 100 mm, the defibrating property in the card machine is deteriorated, and the resulting fiber structure such as a nonwoven fabric is inferior in uniformity.

  Further, the single yarn fineness of the flame-retardant polyester composite short fiber of the present invention is preferably 1 to 20 dtex, and more preferably 1 to 15 dtex. When the single yarn fineness is less than 1 dtex, single yarn cutting frequently occurs in the spinning and drawing processes, the operability is deteriorated, and the strength of products such as the obtained nonwoven fabric tends to be inferior. On the other hand, when the single yarn fineness exceeds 20 dtex, cooling of the spun yarn becomes insufficient, and the quality of the obtained fiber tends to be lowered.

  And since the flame-retardant polyester composite short fiber of the present invention is arranged so that the polyester A having excellent crystallinity occupies at least a part of the fiber surface, the fusion between the single yarns is performed during melt spinning. It does not occur and can be stretched and heat treated at a high temperature, and can be made into a fiber having a low heat shrinkage rate.

  Specifically, the flame-retardant polyester composite short fiber of the present invention preferably has a dry heat shrinkage rate of 7% or less at (TmA-30) ° C. when the melting point of polyester A is TmA, and in particular, 5 % Or less, more preferably 4.5% or less.

  The dry heat shrinkage in the present invention is measured by the dry heat shrinkage measurement method in the measurement of the shrinkage of JIS L-1015. The initial load is 50 mg / dtex, the gripping interval is 25 mm, and the treatment temperature is ( TmA-30) Measured as ° C. In addition, when the fiber length is short and measurement is difficult, it shall measure using the fiber before cutting into a short fiber.

  (TmA-30) By setting the dry heat shrinkage rate at 7 ° C. or less to 7% or less, the shrinkage when heat-bonding the web or the like is reduced when a nonwoven fabric or the like is produced using this short fiber as a binder fiber, and heat is reduced. Products such as non-woven fabric obtained after the adhesion treatment are excellent in formation and uniformity. On the other hand, when the dry heat shrinkage at (TmA-30) ° C. exceeds 7%, it is difficult to achieve such an effect.

  When producing short fibers using polyester that does not exhibit a clear crystal melting point as in the prior art, welding between single yarns occurs during melt spinning, and if the heat treatment temperature is 100 ° C. or higher in the drawing and heat treatment steps, Fiber melting and sticking occur, making implementation difficult. Therefore, the drawing and heat treatment steps are performed at a low temperature, and the obtained short fibers have a high dry heat shrinkage rate. For this reason, when a nonwoven fabric is produced using such short fibers as binder fibers, the shrinkage when the web is thermally bonded increases, and the resulting nonwoven fabric has a large web shrinkage ratio compared to the area of the web before the thermal bonding treatment. It was inferior to formation and uniformity.

The method for producing the flame-retardant polyester composite short fiber of the present invention will be described using an example.
First, a dicarboxylic acid component and a diol component are esterified or transesterified, and a crystal nucleating agent is added to perform a polycondensation reaction. When the polyester reaches a predetermined intrinsic viscosity in the polycondensation reaction, it is discharged into a strand shape, cooled and cut into chips to obtain polyester A.

  Next, similarly to polyester A, a dicarboxylic acid component and a diol component are added, and further a phosphorus compound is added, and an esterification reaction or a transesterification reaction is performed to perform a polycondensation reaction. When the polyester reaches a predetermined intrinsic viscosity in the polycondensation reaction, it is discharged into a strand shape, cooled, and cut into chips to obtain polyester B.

  Chips of polyester A and polyester B are supplied to an ordinary composite melt spinning apparatus, and melt spinning is performed with polyester A serving as a sheath and polyester B serving as a core. After spinning and solidifying the spun yarn, it is once stored in a container. Then, the yarns are converged into a yarn bundle, and stretched at a stretch ratio of about 2 to 4 times between rollers. Subsequently, heat treatment is performed at 100 to 120 ° C., and after applying the finishing oil, mechanical crimping is applied using a stuffing box or the like, and the fiber is cut to a target fiber length to obtain a flame-retardant polyester composite short fiber.

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) 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.
(B) Melting point of polyester A, DSC curve showing temperature drop crystallization determined from DSC Measured by the above method.
(C) Melting point of polyester B Using a differential scanning calorimeter (Diamond DSC manufactured by Perkin Elmer Co.), the temperature giving the extreme value of the melt absorption curve measured at a heating rate of 20 ° C./min was defined as the melting point.
(D) Flow start temperature of polyester B Using a flotester (Shimadzu CFT-500 type), the temperature was increased at a rate of 10 ° C./minute from an initial temperature of 50 ° C. under a load of 9.8 MPa and a nozzle diameter of 0.5 mm. The temperature was determined as the temperature at which the polymer began to flow out of the die.
(E) Polymer composition of polyester A and polyester B The obtained polyester composite short fiber was dissolved in a mixed solvent having a volume ratio of 1/20 of deuterated hexafluoroisopropanol and deuterated chloroform. 1H-NMR was measured with a 400-type NMR apparatus, and obtained from the integrated intensity of the proton peak of each copolymer component in the obtained chart.
(F) Spinning operability The following two stages were evaluated according to the spinning conditions.
A: The number of cut yarns during spinning is 1 / ton or less, and there is no welding between single yarns.
X: The number of cut yarns during spinning exceeds 1 time / ton, or welding occurs between single yarns.
(G) Dry heat shrinkage (%)
Measurement was performed by the method described above.
(I) Evaluation of nonwoven fabric Formation The formation of the surface of the obtained nonwoven fabric was visually evaluated in two stages: good (◯) and defective (×).
2. Web shrinkage rate A sample of area A0 (vertical 20 cm × width 20 cm = 400 cm ² ) was cut from the web obtained when the nonwoven fabric was obtained, and this sample was taken as (Tm + 10) ° C. when the melting point of the polyester (A) was Tm. It is allowed to stand for 15 minutes in a hot air drier set to 1 (performs a thermal adhesion treatment), and thereafter (after the thermal adhesion treatment), the area of the nonwoven fabric is A1, and is calculated by the following formula. The web shrinkage is preferably 10% or less, more preferably 9.5% or less.
Web shrinkage (%) = {(A0−A1) / A0} × 100
3. Flexibility (feel)
The softness of the obtained nonwoven fabric was judged by tactile sensation and evaluated in two stages: good (◯) and bad (×).
4). Flame retardancy The obtained nonwoven fabric was evaluated with a limiting oxygen index (LOI) according to Fire Safety No. 65, and an LOI value of 27 or higher was accepted.

Example 1
The slurry of TPA and EG is continuously supplied to the esterification reactor and reacted under the conditions of a temperature of 250 ° C. and a pressure of 0.2 MPa, and a residence time of 8 hours is obtained to obtain a reaction product with an esterification reaction rate of 95%. It was. This reaction product was transferred to a polycondensation reaction vessel, HD was charged into the polycondensation reaction vessel, and stirred at a temperature of 240 ° C. and normal pressure for 1 hour. Next, EG slurry containing 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 was put into a polycondensation reaction can, and then the pressure in the reactor was gradually reduced while stirring. The polycondensation reaction was carried out for about 3 hours, and was discharged into a strand form by a conventional method to form chips. The obtained polyester A comprises TPA as an acidic component, 15 mol% of EG as a glycol component, and 85 mol% of HD, contains 0.5% by mass of talc as a crystal nucleating agent, has an intrinsic viscosity of 0.95, and a melting point of 128 ° C. there were.

  To the esterification can, TPA, IPA, EG and the phosphorus compound described in chemical formula (1) are added and stirred for 3 hours under conditions of a temperature of 240 ° C. and a pressure of 0.2 MPa. The product was transferred to a condensation reaction can. Then, the pressure in the reactor was gradually reduced, and the polycondensation reaction was carried out for about 3 hours with stirring, and the strand was discharged into a strand by a conventional method to form chips. The obtained polyester B has an acid content of TPA of 67 mol%, isophthalic acid of 25 mol%, a phosphorus compound of 8 mol%, a glycol component of hexanediol (HD) of 100 mol%, an intrinsic viscosity of 0.79, a flow start temperature of 130 ° C., and a phosphorus atom content It was a copolymer (B-1 in Table 2) so that the amount was 12000 ppm.

  Polyester A chip and polyester B chip are supplied to the compound spinning device, and polyester A is a sheath and polyester B is a core-sheath shape, and melt spinning is performed at a mass ratio of both components of 50/50. It was. At this time, spinning was performed under the conditions of a spinning temperature of 220 ° C., a discharge rate of 600 g / min, a spinning hole number of 1014, and a spinning speed of 800 m / min. Next, the spun yarn was cooled with cold air at 18 ° C. and taken out to obtain an undrawn yarn.

  This undrawn yarn is bundled and drawn into a 110,000 dtex tow-like undrawn fiber at a draw ratio of 3.2 times and a draw temperature of 50 ° C., and then heat-treated with a heat drum (temperature of 110 ° C.). gave. Next, crimping was applied with a push-in crimper, and the fiber length was cut to 51 mm to obtain a flame-retardant polyester composite short fiber having a single yarn fineness of 2.2 dtex.

The obtained flame-retardant polyester composite short fiber is used as a binder fiber, and the main fiber is made of PET having a melting point of 256 ° C., fineness 2.2 dtex, fiber length 51 mm, strength 5.5 cN / dtex, elongation 40%, 170 ° C. Using a short fiber having a dry heat shrinkage of 3.0% in 15 minutes and a mixing ratio of 30/70 (binder fiber / main fiber), a dry web was prepared through a card machine. The obtained dry web was heat-bonded for 1 minute with a continuous heat treatment machine at a temperature of 138 ° C. and an air volume of 20 m ³ / min to obtain a dry nonwoven fabric with a basis weight of 100 g / m ² .

Comparative Examples 1-2
A flame-retardant polyester composite short fiber was obtained in the same manner as in Example 1 except that the amount of talc added to the crystal nucleating agent of polyester A was changed to the content shown in Table 1. Further, a dry nonwoven fabric was obtained in the same manner as in Example 1.

Examples 2-4, Comparative Examples 3-5
As in Example 1, except that the polyester of Example 1 was used as the polyester A constituting the sheath and the polyester B constituting the core was changed to that shown in Table 2, the flame-retardant polyester composite short Fiber was obtained. Further, a dry nonwoven fabric was obtained in the same manner as in Example 1.

Example 5
TPA, HD, and BD are supplied to the esterification reactor, talc having an average particle size of 1.0 μm and a specific surface area of 35 m ² / g is added as a crystal nucleating agent, and the conditions are 3 at a temperature of 230 ° C. and a pressure of 0.2 MPa. After stirring for a period of time and carrying out an esterification reaction, it was transferred to a polycondensation reaction can. Then, the pressure in the reactor was gradually reduced, and the polycondensation reaction was carried out for about 3 hours with stirring, and the strand was discharged into a strand by a conventional method to form chips. The obtained polyester A comprises TPA as an acidic component, 20 mol% of 1,4-butanediol (BD) as a glycol component, and 80 mol% of HD, contains 0.5% by mass of talc as a crystal nucleating agent, and has an intrinsic viscosity of 0 .98, melting point 130 ° C.
The same polyester (B-1 of Table 2) as Example 1 was used as polyester B, and the polyester A chip | tip and the polyester B chip | tip were used like Example 1, and the flame-retardant polyester composite short fiber was obtained. A dry nonwoven fabric was obtained in the same manner as in Example 1 except that the obtained flame-retardant polyester composite short fiber was used and the heat bonding treatment temperature was 140 ° C.

  Table 1 shows the characteristic values and evaluation results of the flame-retardant polyester composite short fibers and dry nonwoven fabrics obtained in Examples 1 to 5 and Comparative Examples 1 to 5.

  As is clear from Table 1, in the flame-retardant polyester composite short fibers of Examples 1 to 5, polyester A satisfies the formula (1) and has high crystallinity. A composite fiber with B as the core could be obtained with good spinning operability. In addition, stretching and heat treatment could be performed satisfactorily, and the dry heat shrinkage rate could be low. And when obtaining a nonwoven fabric from these composite short fibers, the web shrinkage rate is low and can be obtained with good dimensional stability. Polyester B is obtained by copolymerizing a phosphorus compound, and an appropriate amount of phosphorus atoms is contained in the fiber. Since it was contained, the obtained nonwoven fabric was excellent in formation, flexibility and flame retardancy.

  On the other hand, since the polyester composite short fiber of Comparative Example 1 contained a large amount of talc as a crystal nucleating agent, cut yarns were generated during spinning and the operability was poor. As a result, the variation in yarn quality increased, the dry heat shrinkage rate increased, and the web shrinkage rate was large when obtaining a nonwoven fabric. The resulting nonwoven fabric was poor in texture and poor in flexibility. Since the polyester composite short fiber of Comparative Example 2 has too little content of the crystal nucleating agent, the crystallization speed is slow, and the heat drum temperature cannot be heat treated at the same temperature as in Example 1, and the heat treatment temperature is lowered. The obtained fiber had a large dry heat shrinkage. For this reason, the web shrinkage rate at the time of obtaining a nonwoven fabric was large, and the obtained nonwoven fabric had poor texture and poor flexibility. Since the polyester composite short fiber of Comparative Example 3 had a high flow start temperature of Polyester B, polyester B did not flow and did not melt at the same thermal bonding treatment temperature (138 ° C.) as Example 1, and lacked flexibility. It became a non-woven fabric. Since the polyester composite short fiber of Comparative Example 4 had a low content of phosphorus compound, the obtained nonwoven fabric was inferior in flame retardancy. Since the polyester composite short fiber of Comparative Example 5 contained too much phosphorus atom in the fiber, the spinning operability was poor and an undrawn yarn could not be obtained.

It is an example of the DSC curve which shows the temperature-fall crystallization calculated | required from DSC of the polyester A which comprises the flame-retardant polyester composite short fiber of this invention.

Claims (1)

It consists of a dicarboxylic acid component mainly composed of terephthalic acid and a diol component of 1,6-hexanediol of 50 mol% or more, contains 0.01 to 5.0% by mass of a crystal nucleating agent, and has a melting point (TmA). The difference between the polyester A in which the DSC curve indicating the temperature-falling crystallization obtained from DSC with 100 to 150 ° C. satisfies the following formula (1) and the melting point (TmA) of the polyester A and the melting point or the flow start temperature (TmB) ( TmB-TmA) is a composite fiber composed of polyester B having a phosphorus compound copolymerized at a temperature of + 5 ° C. or less, and polyester A occupies at least a part of the fiber surface in the cross-sectional shape of a single yarn A flame-retardant polyester composite short, characterized in that the content of phosphorus atoms in the fiber is 2000-15000 ppm and the fiber length is 1-100 mm Wei.
b / a ≧ 0.05 (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.