JP2002339257A - Ultrafine polyester drawn fiber for papermaking - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide ultrafine polyester drawn fibers for papermaking highly dispersible in water in the papermaking process in producing ultrafine polyester fibrous paper. SOLUTION: The ultrafine polyester drawn fibers each <=0.5 dtex in fineness and 2-20 mm in length are such as to be borne with >=0.03 wt.% of a polyether- polyester copolymer and designed to be >=5 wt.% in moisture retention.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drawn polyester fiber having a fineness and excellent dispersibility in water in a papermaking process.

[0002]

2. Description of the Related Art Conventionally, vinylon fibers, polyacrylonitrile fibers, polypropylene fibers, polyester fibers and the like have been used as synthetic fibers for papermaking. In recent years, mechanical properties, electrical properties, heat resistance, excellent dimensional stability, etc.,
In addition, polyester fibers having high cost advantage are often used for a part or all of papermaking raw materials. In recent years, polyester fibers having a single-fiber fineness of less than 1 dtex for heat-sensitive stencil printing base paper, filters and the like have been increasingly used.

[0003] Polyester fibers that are hydrophobic have poor dispersibility in water during papermaking, and various measures for improving the dispersibility in water are necessary to produce high quality polyester fiber paper. For example, Japanese Patent Publication No. 1-35120 proposes a method of improving the dispersibility of polyester fibers in water by attaching a polyester / polyether block copolymer in an amount of 0.02 to 2% based on the weight of the fibers. However, the single yarn of the ultrafine polyester stretched fiber whose single yarn fineness is less than 1 dtex is extremely flexible, and the single yarns are easily entangled with each other.
Simply adding the polyester / polyether block copolymer does not improve the dispersibility of the fiber in water.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a drawn polyester fiber which is extremely fine and has excellent water dispersibility in a papermaking process.

[0005]

Means for Solving the Problems The present inventor has conducted intensive studies to solve the above-mentioned problems, and as a result, it has been found that the drawn polyester fiber has a fineness of 0.5 decitex or less and a fiber length of 2 to 20 mm, On the fiber surface, 0.03% of a polyether / polyester copolymer based on the fiber weight was used.
5% by weight with moisture retention of more than 5% by weight
It has been found that the above can be achieved by the drawn polyester fiber.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. The polyester constituting the drawn polyester fiber for papermaking of the present invention is a polyester in which 85 mol% or more, preferably 95 mol% or more of all repeating units are composed of ethylene terephthalate. A small amount (usually 15 mol% or less based on the terephthalic acid component) of a component other than the terephthalic acid component and the ethylene glycol component may be copolymerized. Incidentally, these polyesters, known additives, for example, pigments, dyes, matting agents,
It may contain an antifouling agent, an antibacterial agent, a deodorant, a fluorescent whitening agent, a flame retardant, a stabilizer, an ultraviolet absorber, a lubricant and the like.

The drawn fiber of the present invention comprising the above-mentioned polyester is intended to be drawn so that the birefringence becomes 0.05 or more, and its fineness is 0.5 decitex or less. If the fineness exceeds 0.5 decitex, the performance as a base paper for heat-sensitive stencil printing, a high-performance filter or a polyester fiber paper for an artificial leather substrate is not sufficiently exhibited, which is not preferable. Note that the lower limit of the fineness does not need to be particularly limited, but if it is too low, the production cost increases and the cost becomes high. Therefore, it is preferable that the fineness be 0.1 decitex or more.

The above drawn polyester fiber having a fineness of 0.5 decitex or less (hereinafter referred to as an ultrafine drawn polyester fiber) has a fiber length of 2 to be used for papermaking.
２０20 mm, preferably 2-10 mm. If the fiber length is shorter than 2 mm, the cutting resistance increases, the fibers tend to be entangled with each other, and quality irregularities of the fibers occur. On the other hand, when the fiber length is longer than 20 mm,
At the time of papermaking, the dispersibility of the fibers in water deteriorates, which is not preferable. The upper limit of the fiber length of ordinary drawn polyester fiber for papermaking is said to be 30 mm.
It is estimated that the upper limit fiber length becomes short because the next moment is low and the fibers tend to be entangled in water.

The drawn ultrafine polyester fiber of the present invention must have a polyether / polyester copolymer adhered to the fiber surface at 0.03% by weight or more, preferably 0.05% by weight or more, based on the fiber weight. is there. If the amount is less than 0.03% by weight, dispersion of the fibers in water in the papermaking process becomes insufficient. If the amount of adhesion is too large, not only does the adhesiveness between fibers tend to be impaired, but also a large amount of polyether / polyester copolymer increases the water quality load on the circulating water in the papermaking process,
It is preferable that the content be 1.5% by weight or less.

The above-mentioned polyether / polyester copolymer used in the present invention comprises terephthalic acid and / or isophthalic acid, lower alkylene glycol and polyalkylene glycol and / or monoether thereof. Preferred examples of the lower alkylene glycol include ethylene glycol, propylene glycol, and tetramethylene glycol. on the other hand,
The polyalkylene glycol has an average molecular weight of 60
Examples thereof include polyethylene glycol of 0 to 6000, a polyethylene glycol / polypropylene glycol copolymer, and polypropylene glycol. Further, examples of the monoether of polyalkylene glycol include monomethyl ether such as polyethylene glycol and polypropylene glycol, monoethyl ether, and monophenyl ether. The copolymer had a molar ratio of terephthalate unit to isophthalate unit of 95: 5 to 40: 6.
A range of 0 is preferable from the viewpoint of dispersibility in water, but a small amount of an alkali metal salt sulfoisophthalic acid, adipic acid, sebacic acid, or the like may be copolymerized. The average molecular weight of the polyether / polyester copolymer composed of the above components depends on the molecular weight of the polyalkylene glycol used, but is usually from 1,000 to 20,000, preferably from 3,000 to 150.
00. If the average molecular weight is less than 1,000, the effect of improving dispersibility in water is not sufficient, while if it exceeds 20,000, emulsification and dispersion of the polymer become difficult.

Such a polyether / polyester copolymer is usually attached to the fiber surface as an aqueous dispersion, but the copolymer can be relatively easily dispersed in water. In order to further improve the stability of the obtained aqueous dispersion, a small amount of a surfactant or an organic solvent may be added, or various kinds of treating agents such as oils may be mixed and used. An ordinary method such as dipping, spraying, or roller touching is adopted as the attaching method, but a dip method is suitable for uniform attachment.

The drawn ultrafine polyester fiber of the present invention to which the polyether / polyester copolymer has been imparted must have a water retention of 5% by weight or more in addition to the above requirements.
If the water retention is less than 5% by weight, the dispersion of the fibers in water in the papermaking process becomes insufficient. Further, when the fiber is cut to the fiber length, scattering of the fiber becomes severe. In addition,
If the water retention rate is too large, the water is scattered at the time of cutting, which makes it difficult not only to cut stably, but also becomes uneconomical in terms of transportation costs. It is preferable to set the following.

[0013]

Next, the present invention will be described specifically with reference to examples. Each item in the examples was measured by the following method. (A) Intrinsic viscosity Using orthochlorophenol as a solvent, the viscosity was measured with an Ubbelohde viscosity tube at a temperature of 35 ° C. (B) Birefringence (Δn) Using a commercially available polarizing microscope, a sodium lamp was used as a light source, and the retardation was calculated from the Berk compensator method while the sample was immersed in α-bromonaphthalene. (C) Moisture content About 100 g of water-containing ultrafine polyester drawn fiber is dried in a hot air circulation type dryer at 120 ° C. until it is completely dried. The weight W ₀ of the sample before drying and the weight W ₁ of the sample after drying
From the following equation. Moisture percentage (%) = [(W ₀ −W ₁ ) / W ₁ ] × 100

(D) Dispersibility in water 500 mL of tap water is put into a 1000 mL measuring cylinder, and net 0.1 g of drawn polyester fiber is put therein. When the fiber reaches the bottom of the graduated cylinder,
Cover the opening of the measuring cylinder, hold the top and bottom with both hands,
The measuring cylinder is inverted once to disperse the fibers, and the quality of the underwater dispersibility is determined based on the following criteria. Very good: no undispersed fiber bundles, and each single fiber is spread beautifully in water. Good: almost no undispersed fiber bundles. Slight entanglement between single fibers is observed but acceptable range is bad. There are several or more undispersed fiber bundles and many entanglements between single fibers.

[Examples 1 to 3, Comparative Example 1]
After drying the 43 polyethylene terephthalate chips, 3
Melted at 00 ° C and passed through a spinneret with 1192 holes
It was discharged at a rate of 160 g / min and was taken off at a speed of 1300 m / min to obtain an undrawn yarn. The undrawn yarn was made into an undrawn tow of about 500,000 dtex, and drawn in warm water at two stages at a drawing speed of 70 m / min so that the total drawing ratio was 3.3 times.

The stretched tow is prepared by mixing an acid component of terephthalic acid 80 mol% and isophthalic acid 20 mol% with an average molecular weight of 30.
And a glycol component of 70% by weight of polyethylene glycol and 30% by weight of ethylene glycol, and passed through an aqueous dispersion of a polyether / polyester copolymer having an average molecular weight of about 10,000. Was reduced to 15% by weight.

Here, the amount of adhesion was changed by variously changing the concentration of the aqueous dispersion of the polyether / polyester copolymer. Further, after the stretched tow is subjected to relaxation heat treatment in an atmosphere of 110 ° C., water is applied by a roller-applied water application device so that the water content becomes 17% by weight, supplied to a drum type cutter, and cut into a length of 5 mm. did. The fineness of the obtained ultrafine polyester drawn fiber was 0.35 dtex, and the birefringence (Δn) was 0.173. Table 1 shows the relationship between the adhesion amount of the polyether / polyester copolymer and the dispersibility in water.

[0018]

[Table 1]

[Examples 4 to 6, Comparative Example 2]
After drying the polyethylene terephthalate chip of No. 47, 3
Melted at 00 ° C and passed through a die with 1192 holes,
Discharge was performed at 0 g / min, and a drawn undrawn yarn was obtained at a speed of 500 m / min. The undrawn yarn was made into an undrawn tow of about 2,000,000 dtex, and the first-stage drawing was performed 5.2 times in hot water at 90 ° C., followed by 2.9 times the drawing in hot water at 70 ° C. Two-stage stretching was performed.

The unstretched tow is passed through the same aqueous dispersion of the polyether / polyester copolymer as in Examples 1 to 3, and the squeezing rate and the degree of drying after squeezing are changed in various ways, and the resulting tow is supplied to the cutter. The tow was changed in moisture content and cut into 3 mm lengths. The fineness of the obtained drawn polyester fiber was 0.23 dtex, and the birefringence (Δn) was 0.152. The amount of the polyether / polyester copolymer was adjusted so as to be in the range of 0.3 to 0.5% by weight. Table 2 shows the obtained results.

[0021]

[Table 2]

[0022]

According to the drawn ultrafine polyester fiber for papermaking of the present invention, the dispersibility of the fiber in water during the papermaking process is improved, and a fine polyester fiber paper of high quality can be obtained.

Claims (1)

[Claims] A polyester stretched fiber having a fineness of 0.5 decitex or less and a fiber length of 2 to 20 mm,
A polyether / polyester copolymer adhered to the fiber surface by 0.03% by weight or more based on the fiber weight, and a water retention rate of 5% by weight or more, fiber.