JP2019210566A - Polyester-based binder fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester-based binder fiber for papermaking having a fineness. SOLUTION: The fiber is mainly composed of polyester resin, has a fineness of less than 0.5 dtex, a birefringence of 0.05 or less, a specific gravity of 1.37 or less, and is crystallized by differential thermal measurement. A polyester binder fiber having a temperature of 80 to 150 ° C. Furthermore, it is preferable that the polyester resin is a polyethylene terephthalate resin and that the fiber length is 0.5 to 15 mm. Alternatively, a method for producing a binder fiber in which a polyester resin is melt-spun and cut after stretching, the stretching is flow stretching, the fineness after flow stretching is less than 0.5 dtex, and the crystallization temperature is 80 to 150 ° C. A method for producing a binder fiber. And the wet non-woven fabric containing the binder fiber of the present invention is included. [Selection diagram] None

Description

  The present invention relates to a polyester-based binder fiber, and more particularly to a polyester-based binder fiber suitable for producing polyester fiber paper using polyester fiber as a main fiber.

  Conventionally, cellulosic fibers such as pulp and rayon have been used as raw materials for papermaking, but in terms of excellent physical properties such as mechanical properties, electrical properties, and heat resistance, a papermaking method using polyester fibers as raw materials The use of synthetic fiber paper by is expanding.

  In such synthetic fiber paper, it is already known to use unstretched polyester fibers as binder fibers for bonding main fibers made of stretched fibers (Patent Documents 1 to 3, etc.). In recent years, there has been an increasing demand for denser synthetic fiber paper in various industrial applications such as separators and filter applications, and fibers with finer fineness are required not only for drawn fibers, which are the main fibers, but also for binder fibers. ing.

  For example, Patent Document 4 discloses unstretched binder fibers thinner than 1 dtex, which are fibers spun from a polyester resin containing 0.1 to 5.0% by mass of a polymer having a predetermined composition and polyester. However, the lower limit of the fineness of the fiber disclosed in the examples is 0.8 dtex.

  With the binder fibers described in these patent documents, it is currently difficult to obtain binder fibers with a sufficiently small fineness.

Japanese Patent Publication No.49-8809 JP-A-57-82599 JP-A-1-104823 International Publication No. 2015/152082 Pamphlet

  An object of the present invention is to provide a polyester binder fiber for papermaking having a fineness.

The polyester-based binder fiber of the present invention is a fiber mainly composed of a polyester-based resin, having a fineness of less than 0.5 dtex, a birefringence of 0.05 or less, a specific gravity of 1.37 or less, and a differential. The crystallizing temperature by heat measurement is 80 to 150 ° C.
Furthermore, it is preferable that the polyester-based resin is a polyethylene terephthalate resin and the fiber length is 0.5 to 15 mm.
Another method for producing a polyester-based binder fiber of the present invention is a method for producing a binder fiber in which a polyester-based resin is melt-spun and cut after stretching, wherein the stretching is flow-stretching, and the fineness after flow-stretching is It is characterized by being less than 0.5 dtex and a crystallization temperature of 80 to 150 ° C.
And this invention includes the wet nonwoven fabric containing the polyester-type binder fiber of the said invention described above.

  According to the present invention, a polyester binder fiber for papermaking having a fineness is provided.

  The polyester binder fiber of the present invention is a fiber mainly composed of a polyester resin, having a birefringence of 0.05 or less, a specific gravity of 1.37 or less, and a crystallization temperature by differential heat measurement. It is a fiber which is 80-150 degreeC.

  Polyesters used in the present invention include polyesters of aromatic dicarboxylic acids and aliphatic diols such as polyalkylene terephthalates such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyalkylene naphthalates such as polyethylene naphthalate, Polyesters of alicyclic carboxylic acids and aliphatic diols such as polyalkylenecyclohexanedicarboxylate, polyesters of aromatic carboxylic acids and alicyclic diols such as polycyclohexanedimethanol terephthalate, polyethylene succinate, polybutylene succinate, polyethylene adipate Polyesters of aliphatic carboxylic acids and aliphatic diols such as, polyhydroxycarboxylic acids such as polylactic acid and polyhydroxybenzoic acid, etc. It is exemplified. Depending on the purpose, isophthalic acid, phthalic acid, adipic acid, sebacic acid, α, β- (4-carboxyphenoxy) ethane, 4,4-dicarboxyphenyl, 5-sodium sulfoisophthalic acid, 2 , 6-Naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid or esters thereof, diethylene glycol as a diol component, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, One or more components such as 1,4-cyclohexanedimethanol, polyalkylene glycol and the like may be copolymerized, and further, three or more carboxylic acid components such as pentaerythritol, trimethylolpropane, trimellitic acid, trimesic acid, etc. Branched by copolymerizing components It may be allowed.

  In addition, when a polymer obtained by copolymerizing isophthalic acid or 5-sodium sulfoisophthalic acid is used, fluidity is improved and adhesiveness as a binder fiber is improved. When isophthalic acid is copolymerized, it is preferable to copolymerize 2 to 20 mol%. If the amount is less than 2 mol%, the effect of improving adhesiveness is small. If the amount is more than 20 mol%, the fibers tend to stick together, and the dispersibility in water when paper is made deteriorates. When 5-sodium sulfoisophthalic acid is copolymerized, it is preferable to copolymerize 3 to 6 mol%. When the amount is less than 3 mol%, the effect of improving adhesiveness is small. If it is more than 6 mol%, the increase in viscosity at the time of melting becomes large, the spinnability becomes poor, and the softening deformation at the time of the bonding process at the time of papermaking is insufficient due to the thickening effect, so that the adhesive strength is lowered. Also included are mixtures of polyesters having different compositions as exemplified above. These polyesters include known additives such as pigments, dyes, matting agents, antifouling agents, antibacterial agents, deodorants, fluorescent whitening agents, flame retardants, stabilizers, ultraviolet absorbers, and lubricants. Etc. may be included.

  Moreover, the range of the intrinsic viscosity of the polyester-type binder fiber of this invention has the preferable range of 0.35-0.60. More preferably, it is 0.40 to 0.55. If the intrinsic viscosity is too high, the shrinkage rate increases and the strength of the finally obtained polyester fiber paper decreases. On the other hand, if the intrinsic viscosity is too small, the spinnability is deteriorated and spinning tends to be difficult.

  The single yarn fineness of the polyester binder fiber of the present invention needs to be less than 0.5 dtex. Furthermore, it is preferably less than 0.2 dtex. The lower limit of the single fiber fineness is not particularly limited, but is usually about 0.01 dtex from the viewpoint of stable yarn forming properties. When the binder fiber of the present invention is used as a polyester fiber paper, it is preferably bonded by thermal calendering. By using such a binder fiber, it is dense and uniform, but has high air permeability. It becomes possible to set it as the nonwoven fabric of this. Furthermore, the fineness of the binder fiber used in the present invention is preferably in the range of 0.02 to 0.15 dtex, particularly 0.06 to 0.10 dtex.

  The specific gravity of the polyester binder fiber of the present invention needs to be 1.37 or less. When it is larger than 1.37, the crystallization of the binder fiber is advanced, and the adhesiveness of the paper at the time of papermaking is insufficient. Furthermore, the specific gravity is preferably 1.34 to 1.36.

  The birefringence of the polyester binder fiber of the present invention is required to be 0.05 or less. If it is higher than 0.05, softening hardly occurs during the thermal bonding process in the paper making process, and the strength of the resulting polyester fiber paper is lowered. Furthermore, the birefringence is preferably in the range of 0.01 to 0.03.

  And the polyester-type binder fiber of this invention needs to show crystallization temperature in a differential heat measurement. The crystallization temperature is the temperature at the top of the crystallization peak at the time of temperature rise measured by a differential thermal analyzer. In general, oriented polyester fibers undergo oriented crystallization and do not show a crystallization peak, but the polyester fibers of the present invention suppress crystallization in a medium higher than the glass transition temperature (hereinafter referred to as Tg). In order to extend the film while suppressing the orientational crystallization, the crystallization temperature can be indicated. The crystallization temperature is preferably in the range of 80 to 150 ° C, more preferably 90 to 130 ° C, particularly preferably 100 to 120 ° C. When the crystallization temperature is lower than 80 ° C., the crystallization of the binder fiber proceeds when the finished paper is dried, and the adhesiveness in the calendering (hot pressing) processing during the subsequent processing is insufficient. Further, in order to raise the crystallization temperature, it is necessary to raise the stretching temperature. However, if this occurs, the fibers tend to stick together, and the dispersibility of the fibers in water during subsequent papermaking tends to be poor.

  In particular, in the polyester-based binder fiber of the present invention, it is important to use a polyester-based binder fiber that simultaneously satisfies the requirements for crystallization temperature by the above-described birefringence, specific gravity, and differential heat measurement, and satisfies these requirements. As a result, a polyester fiber paper excellent in denseness can be obtained. The fiber of the present invention is useful particularly in a polyester fiber paper that is finally densified by calendering.

  Moreover, as a fiber length of such a binder fiber of this invention, it is preferable that it is the range of 0.5-15 mm. More preferably, it is the range of 1-10 mm. When the fiber length is shorter than 0.5 mm, the number of adhesion points with other fibers decreases, and sufficient paper strength cannot be obtained. On the other hand, when the fiber length is longer than 15 mm, the dispersibility of the fiber in water during papermaking deteriorates.

And such a polyester-based binder fiber of the present invention is, for example, another present invention, a method for producing a binder fiber in which a polyester-based resin is melt-spun and cut after stretching, and the stretching is flow-stretching, It can be obtained by a production method characterized in that the crystallization temperature after flow stretching is 90 to 125 ° C.
This manufacturing method will be described in more detail. For example, it can be manufactured by the following method.

  That is, pelletized polyester having an intrinsic viscosity of 0.36 to 0.65, preferably polyethylene terephthalate, is dried by a conventional method, melt-spun in a spinning facility equipped with a screw type extruder, etc., cooled and solidified, and 700 Take up at a speed of ~ 1500 m / min. Here, the moisture content of the pellet, the drying temperature, the melt spinning temperature, and the residence time of the molten polymer in the spinning machine are set and adjusted so that the intrinsic viscosity of the polyester fiber is in the range of 0.35 to 0.60. . Further, the spinning speed is set according to each intrinsic viscosity and discharge amount.

  Then, the polyester unstretched fiber obtained is converged, and the unstretched polyester fiber is stretched at a temperature higher than its Tg, so-called flow stretching is performed. By doing so, it is possible to reduce the fiber diameter while maintaining the orientation of the unstretched fibers. In the present invention, in order to perform more stable stretching, it is desirable to stretch in a medium higher by 10 ° C. or more than the Tg of the polyester used. Further, it is preferable to use water or water vapor as the medium, for example, in wet heat of 80 to 110 ° C., that is, in warm water of 80 ° C. or higher and lower than 100 ° C. or in wet heat of less than 110 ° C. .

  The flow stretching ratio is desirably 5.0 times or more. By setting it to 5.0 times or more, it can be set as an advantageous condition for obtaining a fine fiber having difficulty in obtaining by a normal drawing method. Furthermore, the flow draw ratio for obtaining this binder fiber is preferably 10 times or more, more preferably 15 to 140 times, and particularly preferably 20 to 90 times. By performing high-magnification stretching under such conditions, it becomes easy to obtain a binder fiber having a fineness that is difficult to obtain by a normal stretching method.

  It is preferable that the stretched fiber bundle is provided with a paper-making surfactant and then supplied to a cutter in a state where 5 to 40% by weight of moisture is retained, and is cut into a predetermined fiber length. In addition, when the moisture content is lower than 5% by weight, the dispersibility of fibers at the time of papermaking deteriorates. When the moisture content exceeds 40% by weight, the scattering of water at the time of cutting with a rotary drum cutter increases, and the operation of the cutter becomes difficult.

Moreover, it is possible to obtain another wet nonwoven fabric of this invention by containing the binder fiber of this invention obtained by the above manufacturing methods.
In order to obtain such a wet nonwoven fabric, so-called paper, it can be obtained by the following production method.

  First, when obtaining such a polyester wet nonwoven fabric or polyester paper, it is preferable to use a stretched polyester fiber in addition to the binder fiber of the present invention. Such a drawn fiber may be a normal drawn fiber, but after the flow drawing as described above, the drawn polyester fiber is further sufficiently neck-drawn so as not to exhibit a crystallization temperature. It is also preferable.

  The drawn fiber preferably has a single fiber fineness of 1.0 dtex or less, more preferably less than 0.5 dtex, more preferably in the range of 0.005 to 0.1 dtex, still more preferably 0.01 to 0.05 dtex. Range. The neck draw ratio for obtaining drawn fibers is preferably in the range of 1.5 to 4 times, and more preferably in the range of 2.0 to 3.5 times. Similar to the binder fiber, this stretched fiber is preferably carried out in a medium as in the case of the flow drawing, particularly preferably in hot water of 60 to 80 ° C.

  The weight ratio of the stretched fiber (or main fiber) constituting the wet nonwoven fabric to the binder fiber is preferably 95/5 to 0/100, more preferably 70/30 to 0/100, and more preferably 60/40 to 0. / 100 is preferable. When the content of the binder fiber is too small, the number of fibers constituting the wet nonwoven fabric is extremely reduced, and a uniform nonwoven fabric cannot be produced, and the strength tends to be insufficient.

  Generally, a wet nonwoven fabric composed of main fibers and binder fibers has a high blending ratio of binder fibers, and the binder fibers may become a film during later calendering processing, which may impair the air permeability that is a characteristic of the nonwoven fabric. When an undrawn yarn having a low crystallization temperature is used as a binder fiber, crystallization proceeds due to heat applied in the production process, and thus a characteristic that it is difficult to form a film during hot pressing is exhibited. Therefore, even if the weight ratio of the main fiber to the binder fiber is 0/100, it is possible to produce a wet nonwoven fabric that maintains air permeability.

  And the wet nonwoven fabric which consists of such polyester can be manufactured by a general papermaking process. More specifically, it is also preferable to disperse the fibers in the pulper, and then to make a multi-layered paper by using a long net paper making method, a circular net paper making method, a short net paper making method, or a combination of a plurality of these. In order to obtain a more uniform wet nonwoven fabric, it is also preferable to add a dispersant or an antifoaming agent to the pulper.

  The drying process after papermaking can use a Yankee dryer, an air through dryer, etc. according to a conventional method. The drying temperature is preferably in the range of 70 to 150 ° C. More preferably, it is 80-120 degreeC, More preferably, it is preferable that it is the range of 80-105 degreeC. When the drying temperature is too low, the drying becomes insufficient, and the strength of the wet nonwoven fabric tends to be insufficient. On the other hand, when the drying temperature is too high, the binder fibers are crystallized, and the strength of the wet nonwoven fabric tends to decrease.

  And as a manufacturing method of a wet nonwoven fabric, after making paper by a conventional method as mentioned above, in order to improve paper strength, it is preferable to heat-press by calendar processing. As a calendar roll used at this time, it is preferable to use a metal / metal roll, a metal / paper roll, a metal / elastic roll, or the like.

  In such a heat treatment using a calendar, the temperature of the calendar press is preferably in the range of 100 to 250 ° C. More preferably, it is 150-250 degreeC, Most preferably, it exists in the range of 170-230 degreeC. If the temperature is too low, the fibers are less likely to be crushed and the strength of the wet nonwoven fabric tends to be difficult to develop. On the other hand, if the temperature is too high, the fiber tends to melt and tends to be a non-uniform wet nonwoven fabric. The press pressure at the time of calender heat treatment is preferably within a range of 100 to 2500 N / cm (10 to 255 kgf / cm), more preferably 300 to 2200 N / cm (31 to 224 kgf / cm), particularly 400 to 2000 N. / Cm (41 to 204 kgf / cm) is preferable.

  By using the polyester binder fiber of the present invention, the polyester main fiber can be thermally bonded to obtain a dense polyester fiber paper.

  Furthermore, such polyester fiber paper (wet non-woven fabric) has excellent physical properties such as mechanical properties, electrical properties, heat resistance, dimensional stability and hydrophobicity, and can be formed into a film by thermal calendering. It is a wet nonwoven fabric that is difficult and maintains high air permeability. In particular, the wet nonwoven fabric of the present invention is excellent in uniformity and porosity, and is particularly useful for low-weight applications such as filters and separators.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, each item in an Example was measured with the following method.

(1) Intrinsic viscosity
The measurement was performed with an Ubbelohde viscosity tube at a temperature of 35 ° C. using orthochlorophenol as a solvent.

(2) Crystallization temperature Thermal analyzer 2200 manufactured by TA Instrument Japan Co., Ltd. was used, and the temperature was measured at a heating rate of 20 ° C./min.

(3) Fineness Measured according to JIS L1015 8.5.1 B method.

(4) Birefringence (Δn)
Using a commercially available polarizing microscope, a sodium lamp was used as a light source, and the retardation was calculated from the Berek compensator method in a state where the sample was immersed in α-bromonaphthalene.

(5) Specific gravity
The density was measured according to ISO1183-2: 2004 with a density gradient tube made of an aqueous calcium nitrate solution.

(6) Moisture content
About 100 g of polyester binder fiber containing moisture is dried in a hot air circulating drier at 120 ° C. until it is completely dried. From the weight W ₁ of the sample after drying and the weight W ₀ of the sample before drying, it was determined by the following equation.
Moisture content (%) = {(W ₀ −W ₁ ) / W ₁ } × 100

(7) Air permeability Measured based on JIS L1913 (general short fiber nonwoven fabric test method) and used as an index of the density of nonwoven fabrics having the same basis weight.

[Example 1]
Polyethylene terephthalate pellets having an intrinsic viscosity of 0.47 dl / g are dried at 170 ° C., melted at 290 ° C., discharged through a die having a pore number of 2504 at a discharge rate of 340 g / min, and drawn at a spinning speed of 500 m / min. An unstretched polyethylene terephthalate fiber was obtained. The polyethylene terephthalate fiber was made into a tow of about 200,000 dtex, 34 times flow drawing was performed in warm water at 85 ° C., and after applying an oil agent, the water content of the tow was reduced to about 15% by weight, It cut | disconnected with the length of 3 mm with the type cutter, and obtained the polyester-type binder fiber. The intrinsic viscosity of this fiber was 0.43 dl / g, the fineness was 0.08 dtex, the birefringence was 0.04, the specific gravity was 1.36, and the crystallization temperature was 109 ° C.

Mixing and stirring were performed using 40% by weight of the obtained polyester-based binder fiber and 60% by weight of polyethylene terephthalate fiber having a single fiber fineness of 1.7 dtex and a length of 5 mm, which had been heat-treated by stretching. At this time, in the stretched polyethylene terephthalate fiber, the crystallization temperature was not measured. After that, these two types of fibers are made with a hand paper machine (manufactured by Kumagai Riki Kogyo, model number: No. 2555, standard square sheet machine) with a basis weight of 70 g / m ² , and then a dryer (Kumagaya Riki Kogyo). Using a model No. 2575? II, a rotary dryer (high temperature type)), a drying treatment was performed at 110 ° C. for 1 minute. Thereafter, calendar processing (210 ° C. × 50 kg (490 N) / cm) made of metal / metal was applied to obtain a wet nonwoven fabric (polyester paper). This was a dense wet nonwoven fabric having an air permeability of 0.3 cm ³ / cm ² / s.

[Comparative Example 1]
Polyethylene terephthalate pellets with an intrinsic viscosity of 0.63 dl / g are dried at 170 ° C., melted at 290 ° C., discharged through a die having a pore number of 2504 at a discharge rate of 390 g / min, and drawn at a spinning speed of 1200 m / min. An unstretched polyethylene terephthalate fiber having a single fiber fineness of 1.3 dtex was obtained. The polyethylene terephthalate fiber is made into a tow of about 200,000 dtex, and after applying an oil agent, the tow is squeezed so that the water content of the tow is about 15% by weight, cut to a length of 5 mm with a drum cutter, and a polyethylene terephthalate short fiber Got. The intrinsic viscosity of this fiber was 0.6 dl / g, the fineness was 1.3 dtex, the birefringence was 0.012, the specific gravity was 1.34, and the crystallization temperature was 128 ° C.

A wet nonwoven fabric was obtained by using 40% by weight of this polyethylene terephthalate fiber instead of the binder fiber of Example 1, and using 60% by weight of polyethylene terephthalate fiber that had been stretch-heat treated in the same manner as in Example 1. This product had a high air permeability of 1.2 cm ³ / cm ² / s and was not suitable for applications such as a separator substrate.

[Comparative Example 2]
Polyethylene terephthalate pellets having an intrinsic viscosity of 0.47 dl / g are dried at 170 ° C., melted at 290 ° C., discharged through a die having a pore number of 2504 at a discharge rate of 340 g / min, and drawn at a spinning speed of 1200 m / min. An unstretched polyethylene terephthalate fiber having a single fiber fineness of 1.3 dtex was obtained. The polyethylene terephthalate fiber is made into a tow of about 200,000 dtex, stretched twice in warm water at 88 ° C., which is higher than the glass transition temperature, and after applying an oil agent, the water content of the tow is about 15% by weight. A polyester fiber cut into a length of 5 mm with a drum cutter was obtained. This fiber had physical properties of 0.43 dl / g, fineness of 0.5 dtex, birefringence of 0.02, specific gravity of 1.35, and a crystallization temperature of 124 ° C.

An attempt was made to prepare a wet nonwoven fabric using 40% by weight of this polyester fiber in place of the binder fiber of Example 1, and 60% by weight of polyethylene terephthalate fiber that had been heat-treated by stretching in the same manner as in Example 1. This product had a high air permeability of 0.7 cm ³ / cm ² / s, and was not suitable for applications such as a separator substrate.

  The polyester binder fiber of the present invention has excellent physical properties for papermaking (wet non-woven fabric), and the wet non-woven fabric using the binder fiber of the present invention becomes a polyester fiber paper excellent in denseness and low air permeability and filtered. It can be preferably used for applications such as membranes, separator substrates, high-performance filters and separators.

Claims (5)

  A fiber mainly composed of a polyester-based resin having a fineness of less than 0.5 dtex, a birefringence of 0.05 or less, a specific gravity of 1.37 or less, and a crystallization temperature of 80 to A polyester binder fiber having a temperature of 150 ° C.   The polyester binder fiber according to claim 1, wherein the polyester resin is a polyethylene terephthalate resin.   The polyester binder fiber according to claim 1 or 2, wherein the fiber length is 0.5 to 15 mm.   A method for producing a binder fiber in which a polyester resin is melt-spun and cut after stretching, wherein the stretching is flow stretching, the fineness after flow stretching is less than 0.5 dtex, and the crystallization temperature is 80 to 150 ° C. A process for producing a polyester-based binder fiber characterized by The wet nonwoven fabric containing the polyester-type binder fiber of any one of Claims 1-3.