WO2003042454A1 - Polyester binder fiber for papermaking - Google Patents

Abstract

A polyester binder fiber for paper making, which has an intrinsic viscosity of 0.35 to 0.49 and a single fiber fineness of 1.5 dtex or less, and exhibits an sheet area shrinkage percentage of 70 % or less, the shrinkage percentage being represented by the following formula: sheet area shrinkage percentage (%) = {(A0-A1)/A0} X 100 wherein A0 is the area of a sheet before shrinking treatment, A1 is the area of the sheet after shrinking treatment, the sheet is prepared by agitating and mixing 80 wt % of polyester binder fibers cut into pieces having a length of 5 mm and 20 wt % of NBK in water, to disperse them in water, and making a sheet having a size of ca. 25 cm × ca. 25 cm and a grammage of about 50 g/m2, and the shrinking treatment is carried out in a manner wherein the sheet is dried for a day or more at room temperature, and then is placed on a perforated Teflon sheet and subjected to relaxation shrinkage in a hot circulating dryer at 140˚C for 5 min.

Description

 Description Polyester binder fiber for papermaking Technical field

 The present invention relates to a polyester binder fiber suitable for producing a polyester fiber paper using a polyester fiber as a main fiber. Background technology

 In recent years, from the viewpoint of excellent physical properties such as mechanical properties, electrical properties, heat resistance, dimensional stability, hydrophobicity, and cost advantage, and synthesis by a papermaking method using polyester fiber as part or all of the raw material Fiber paper is increasing. Conventionally, polyethylene fibers, polyvinyl alcohol fibers, etc. have been used as the binder fibers of the synthetic fiber paper. However, the same polyester fibers are most suitable for making synthetic fiber paper mainly made of polyester fibers. It has been used as an active binder.

 For example, a core-sheath type polyester-based composite fiber in which a modified polyester having a low softening point is disposed in a sheath portion and a polyester having a normal melting point is disposed in a core portion is used as one polyester-based binder fiber. However, such a conjugate fiber requires complicated spinning equipment and advanced operation management, so that it becomes a high-cost binder fiber and cannot be used for applications requiring heat resistance.

On the other hand, Japanese Patent Publication No. 49-8809 and Japanese Patent Application Laid-Open No. 1-104883 propose the use of undrawn polyester fibers as binder fibers. In particular, Japanese Unexamined Patent Publication (Kokai) No. 11-104,823 discloses, as a polyester-based binder fiber which strongly adheres to the drawn polyester fiber of the main fiber and gives a soft feeling to the obtained synthetic fiber paper, an unstretched polyester fiber. The intrinsic viscosity (hereinafter referred to as intrinsic viscosity) is 0.5 to 0.58, the single-fiber fineness is 1.2 denier (about 1.3 dtex) or less, and the birefringence (hereinafter referred to as Δη). ) Is less than 0.02 and the specific gravity is less than 1.35. However, such undrawn polyester fibers Since fibers have high shrinkage, they were used in the process of producing high-strength synthetic fiber paper with a low basis weight (30 g // m ² or less), that is, in the papermaking process at high speed and high drying temperature. In this case, excessive heat shrinkage of the undrawn polyester fiber deteriorates the texture of the obtained polyester fiber paper and lowers the strength of the paper. Disclosure of the invention

 An object of the present invention is to provide a papermaking polyester binder fiber which has a small shrinkage during drying and excellent adhesiveness when producing polyester fiber paper. The present inventors have found that a binder fiber which can achieve the above object can be obtained by using a polyester having a very low intrinsic viscosity and selecting proper spinning conditions.

 That is, according to the present invention, the intrinsic viscosity is 0.35 to 0.49, the single fiber fineness is 1.5 decitex or less, and the sheet area shrinkage defined below is 70% or less. Polyester binder fibers for papermaking are proposed.

 Sheet area shrinkage (%) = {(Ao- Ai) / Ao} X I 0 0

Here, AQ is the area of the sheet before shrinkage processing, is the area of the sheet after shrinkage processing, and the sheet is 80% by weight of polyester binder fiber cut to 5 mxn length and 20% by weight of NBKP. % And well mixed in water. Mix and disperse the mixture. The size is about 25 cm X about 25 cm and the basis weight is about 50 gm ² . After shrinking the sheet, dry it at room temperature for one day or more, place it on a perforated Teflon sheet, and relax and shrink in a hot air circulating dryer at 140 ° C for 5 minutes. Perform the processing operation. BEST MODE FOR CARRYING OUT THE INVENTION

The polyester constituting the polyester binder fiber for papermaking of the present invention is 85 mol of the main repeating unit. /. Or more, preferably 9 5 mole _^0/0 or a polyester comprising ethylene terephthalate tallates, or may be obtained by a small amount copolymerized terephthalic acid component and / or components other than E Ji render recall component. Incidentally, these polyesters, pigments, matting agents, as long as the effects of the present invention are not impaired, It may contain known additives such as antibacterial agents, deodorants, fluorescent whitening agents, and ultraviolet absorbers.

 The intrinsic viscosity of the polyester fiber of the present invention ranges from 0.35 to 0.49, preferably from 0.40 to 0.47. If the intrinsic viscosity exceeds 0.49, the shrinkage will be too high, and the strength of the obtained polyester fiber paper will be low. On the other hand, when the intrinsic viscosity is less than 0.35, spinnability deteriorates and spinning becomes extremely difficult.

 The single fiber fineness of the polyester fiber of the present invention is 1.5 dtex or less, preferably 1.3 dtex or less. When the single fiber fineness exceeds 1.5 dtex, the strength of the obtained polyester fiber paper becomes low. The lower limit of the single fiber fineness is not particularly limited, but is usually about 0.2 decitex from the viewpoint of stable spinning properties.

 Further, the polyester fiber of the present invention has a sheet area shrinkage ratio as defined above of 70% or less, and preferably 65% or less. If the area shrinkage exceeds 70%, the formation of the polyester fiber paper will be poor and the strength of the paper will be low. The area shrinkage can be set by adjusting physical properties of the polyester fiber, such as intrinsic viscosity, Δη, and specific gravity, to an appropriate range. If the intrinsic viscosity of the polyester fiber is 0.35 to 0.49, to reduce the sheet area shrinkage to 70% or less, the Δη of the polyester fiber should be 0.012 or less, and the specific gravity should be 1.35 or less. It is preferable to adjust it.

The polyester fiber of the present invention can be produced by the following method. That is, pelletized polyester having an intrinsic viscosity of 0.36 to 0.51 and preferably polyethylene terephthalate is dried by an ordinary method, and then melt-spun in a spinning facility equipped with a screw-type extruder, cooled, and solidified. Take off at a rate of 700-150 OmZ. 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 0.49. To be. In addition, the spinning speed is set according to each intrinsic viscosity and discharge amount, so that the Δn of the polyester fiber is 0.012 or less and the specific gravity is 1.35 or less. The obtained polyester fiber is converged, and supplied to a dying machine while keeping the water content of 5 to 40% by weight, and cut into a predetermined fiber length. If the water content is lower than 5% by weight, the dispersibility of the fibers during papermaking deteriorates. If the moisture content exceeds 40% by weight, water scattering when cutting with a drum-type cutter increases, making it difficult to operate the cutter. The fiber length is 2 to 20 mm, preferably 3 to 10 mm. If the fiber length is shorter than 2 mm, the cutting resistance of the drum type power cutter will increase, and the polyester fibers will be stretched and the single fibers will easily become entangled, making stable cutting difficult. If the fiber length is longer than 20 mm, the dispersibility of the fiber in water during papermaking deteriorates. The polyester fiber produced in this manner has a small drying shrinkage in the papermaking process, has a strong adhesive force to the polyester fiber, and has excellent performance as a binder fiber for polyester fiber paper.

Example

 Hereinafter, the present invention will be described more specifically with reference to examples. Each item in the examples was measured by the following method.

 (a) Intrinsic viscosity '

 The measurement was carried out in a Ubbelohde viscosity tube at a temperature of 35 ° C using orthochlorophenol as a solvent.

 (b) Sheet area shrinkage

Using a square sheet machine manufactured by Kumagai Riki Kogyo Co., Ltd., 80% by weight of polyester binder fiber and 20% by weight of NBKP cut to a length of 5 mm are thoroughly stirred and mixed in water to disperse. a size of about 25 CMX about 25 cm, a basis weight to create about 50 'gZm ² sheet. Next, after drying the sheet at room temperature for one day or more, the sheet is placed on a perforated Teflon sheet and subjected to a relaxation shrinkage treatment in a hot air circulating drier at 140 ° C for 5 minutes. The sheet area shrinkage ratio is calculated from the area Αο before the sheet shrinkage processing and the area 収縮 ι after the sheet shrinkage processing by the following equation.

 Sheet area shrinkage (%) = {(Ao-Ai) / Ao} X I 00

 (c) Birefringence ^ rate (Δη)

Using a commercially available polarizing microscope, a sodium lamp was used as the light source, and the sample was immersed in sodium pronaphthalene. Calculated.

 (d) Specific gravity

 The sample was charged into a density gradient tube (25 ° C) consisting of a mixed solvent of n-heptane and carbon tetrachloride, and the value after 6 hours was taken as the specific gravity.

 (e) Moisture percentage

 About 100 g of polyester binder fiber containing water is dried in a hot air circulating drier at 120 ° C. until it is completely dried. From the weight WQ of the sample before drying and the weight of the sample after drying, it was determined by the following equation.

 Moisture percentage (%) = {(Wo-Wi) / Wi} X 100

 (f) Break length (paper strength) and formation

 The adhesiveness of the polyester binder fiber was evaluated by the strength of the polyester fiber paper. The paper strength was measured by measuring the tensile strength according to JIS SP 8113, and expressed as the breaking length. The quality of the formation of the polyester fiber paper was visually determined.

 Level 1: The distribution of the constituent fibers is uniform, and there are very few spots

 Level 2: The distribution of the constituent fibers is slightly uneven, and the spots are slightly noticeable.

 Level 3: The distribution of constituent fibers is very uneven, and spots are noticeable.

 [Examples 1-3, Comparative Example 1]

 Polyethylene terephthalate pellets with different intrinsic viscosities are dried at 170 ° C, melted at 300 ° C, discharged through a mouthpiece with a hole count of 1192 at a discharge rate of 180 g / min. The yarn was drawn at a spinning speed of 1150 m / min to obtain an undrawn polyethylene terephthalate fiber having a single fiber fineness of 1.3 dtex. The polyethylene terephthalate fiber was made into a tow of about 200,000 decitex, and after the oil agent was applied, it was squeezed so that the water content of the toe became about 15% by weight, and cut into a length of 5 mm with a drum type cutter. An undrawn polyethylene terephthalate fiber having the properties shown in Table 1 was obtained.

And unstretched polyethylene terephthalate obtained phthalate fibers 4 0 wt _^0/0, a single fiber fineness of 0 6 dtex, length of 5 mm stretched heat-treated polyethylene terephthalate of -. DOO fibers 6 0 disperses the weight percent in water The fiber is adjusted to a fiber concentration of 0.04% by weight and fed to a round paper machine. After papermaking, the fiber is dried with a Yankee dryer at 130 ° C and the basis weight is about 25 g. Zm ² polyethylene terephthalate fiber paper was obtained. This paper Table 1 shows the characteristics. table 1

[Examples 4 and 5, Comparative Example 2]

 Melt spinning was carried out under the same conditions and conditions as in Example 1 except that unstretched fibers differing in shrinkage were obtained by changing the discharge rate and spinning speed, and unstretched polyethylene terephthalate fibers having the properties shown in Table 2 respectively. I got These undrawn polyethylene terephthalate fibers were cut into a length of 5 mm in the same manner as in Example 1, and paper was made under the same conditions as in Example 1. Table 2 shows the properties of the obtained paper. Table 2

[Examples 6 and 7, Comparative Example 3]

Dry polyethylene terephthalate pellets with intrinsic viscosity of 0.47 at 170 ° C Thereafter, the mixture was melted at 300 ° C., discharged through a mouthpiece having a number of holes of 119, and taken out at a spinning speed of 115 Om / min. At this time, the discharge amount was changed to obtain undrawn polyethylene terephthalate fibers having different single fiber finenesses. Table 3 shows the properties of these undrawn polyethylene terephthalate fibers. These unstretched polyethylene terephthalate fibers were cut to a length of 5 mm in the same manner as in Example 1, and paper was made under the same conditions as in Example 1. Table 3 shows the properties of the obtained paper. Table 3

産業上の利用可能性

Industrial applicability

 Since the polyester binder fiber of the present invention has an extremely small shrinkage during papermaking drying, it is possible to obtain a polyester fiber paper excellent in formation and firmly bonded to each other from the fiber.

Claims

The scope of the claims 1. Polyester 5 terbinder fiber for papermaking having an intrinsic viscosity of 0.35 to 0.49, a single fiber fineness of 1.5 decitex or less, and a sheet area shrinkage defined below of 70% or less. ,  Sheet area shrinkage (%) = {(Ao-Ai) ZAQ} X I 00 Here, Αο is the area of the sheet before the shrinkage treatment, Ai is the area of the sheet after the shrinkage treatment, and the sheet is 80% by weight of polyester binder fiber cut to 5 mm length and 20% by weight of NBKP. well were stirred and mixed to be dispersed in water, a size of about 10. 25 CMX about 25 cm, refers to the basis weight without about 50 gZm ^2. After shrinking the sheet, dry the sheet at room temperature for a day or more, place it on a perforated Teflon sheet, and relax and shrink in a hot air circulating dryer at 140 ° C for 5 minutes. Perform the processing operation.  2. The papermaking polyester binder fiber according to claim 1, wherein the polyester binder fiber has a birefringence of 0.012 or less.  3. The papermaking polyester binder fiber according to claim 1, wherein the specific gravity of the polyester binder fiber is 1.35 or less.  4. The polyester for papermaking according to any one of claims 1 to 3, wherein the moisture content of the polyester binder fibers is 5 to 40% by weight based on the weight of the fibers.