JP2002339287A - Undrawn polyester fiber for paper-making use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper-making polyester fiber having excellent adhesivity without lowering the dispersibility of fiber in water in a paper-making process for the production of a polyester fiber paper. SOLUTION: A polyether-polyester copolymer is applied in an amount of >=0.03 wt.% to the surface of an undrawn polyester fiber having a fiber length of 2-20 mm and the water content of the fiber is set to 5-40 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an unstretched polyester fiber for papermaking which has excellent dispersibility in water in a papermaking process and has excellent heat adhesion.

[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 particular, polyester fiber paper in which almost all of the papermaking raw materials are made of polyester fibers can make use of almost 100% of the excellent properties of polyester fibers. Also, as a binder component of synthetic fiber paper, conventionally polyethylene-based fibers,
Binder fibers such as polyvinyl alcohol fibers are used. However, when such a binder fiber is used in papermaking in which the main fiber is a polyester fiber, the compatibility between the polyester fiber and the polyester fiber is insufficient, so that the problem of insufficient interfiber adhesion and the mixing of heterogeneous polymers. This causes a problem that excellent characteristics of the polyester fiber are lost. Therefore, as the papermaking binder fiber mainly composed of the polyester fiber, the polyester fiber itself having an adhesive force is optimal. As a method for imparting adhesive force to polyester fibers, there is a polyester composite fiber in which a low-melting polyester is used as a sheath and polyester having a normal melting point is used as a core. However, such a polyester conjugate fiber requires a plurality of types of polyester, complicated spinning equipment and advanced operation management, and becomes an extremely expensive binder fiber. On the other hand, there has been an attempt to use unstretched polyester fibers as binder fibers, but polyester fibers have poor dispersibility in water.
No. 20 must be provided with a dispersion improver. There is a problem that the dispersing agent significantly inhibits the adhesion between the polyester fibers, and it has been difficult to use undrawn polyester fibers as binder fibers as they are.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide an unstretched polyester fiber for papermaking which has excellent adhesion without impairing dispersibility in water during the papermaking process when producing polyester fiber paper. And

[0004]

Means for Solving the Problems The present inventor has conducted intensive studies in order to achieve the above object, and as a result, the fiber length was 2 to 2
0 mm unstretched polyester fiber having a polyether / polyester copolymer adhered to the fiber surface at 0.03% by weight or more based on the fiber weight and having a water retention of 5 to 40% by weight. It has been found that this can be achieved by an unstretched polyester fiber for papermaking, which is characterized by a certain characteristic.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. The polyester constituting the unstretched 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. In addition, these polyesters have known additives, for example, pigments, dyes, matting agents, antifouling agents, antibacterial agents, deodorants, fluorescent brighteners, flame retardants, stabilizers, ultraviolet absorbers, lubricants Etc. may be included.

The unstretched fiber of the present invention comprising the above polyester has a fiber length of 2 to 2 for use in papermaking.
20 mm, preferably 2-10 mm,
If the fiber length is less than 2 mm, not only does the dispersibility in water decrease, but also the cutting resistance during production increases,
Unstretched fibers are stretched or single fibers are easily entangled,
It is not preferable because stable cutting becomes difficult and the resulting unstretched fiber has a large amount of fiber lumps and dispersibility in water becomes extremely poor. On the other hand, if the fiber length is longer than 20 mm, the dispersibility of the fiber in water deteriorates during papermaking, which is not preferable. . It is said that the upper limit of the fiber length of ordinary papermaking polyester fibers is 30 mm. However, in the case of undrawn polyester fibers, since the Young's modulus is low, the fibers are easily entangled in water and the upper limit fiber length is set. Is thought to be shorter.

The unstretched polyester fiber for papermaking of the present invention has 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. There is a need. If the amount is less than 0.03% by weight, dispersion of the fibers in water in the papermaking step becomes insufficient, which is not preferable. If the amount of adhesion is too large, not only does the adhesiveness between fibers tend to be inhibited, but also a large amount of polyether / polyester copolymer increases the water quality load on the circulating water in the papermaking process. Therefore, the content is preferably 1.5% by weight or less.

The polyether / polyester copolymer used in the present invention comprises terephthalic acid and / or isophthalic acid, lower alkylene glycol, and polyalkylene glycol and / or its monoether. 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.

[0009] 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 unstretched polyester fiber of the present invention to which the polyether / polyester copolymer has been imparted must have a water retention of 5 to 40% by weight in addition to the above requirements. If the water retention is less than 5% by weight, it is presumed that the polyether / polyester copolymer film formed on the fiber surface is unlikely to fall off from the fiber surface in the papermaking process, which causes adhesion failure. This is not preferred because the paper strength decreases. On the other hand, when the water retention ratio exceeds 40% by weight, there is no problem in terms of paper strength, but when the undrawn polyester fiber is cut to the fiber length, water scattering increases and the cutter is stably cut. Not only is it difficult, but also uneconomical in terms of transportation costs.

The single fiber fineness of the unstretched polyester fiber for papermaking of the present invention may be appropriately set according to the intended use of the paper to be obtained, and may be 0.2 to 5.0 dtex (hereinafter referred to as dtex).
And the birefringence is 0.05.
The following is preferred.

[0012]

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 undrawn polyester fibers containing water
Dry until absolutely dry in a hot air circulation type dryer at 20 ° C. From the weight W ₀ of the sample before drying and the weight W ₁ of the sample after drying, it was determined by 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 a net 0.1 g of polyester fiber is put therein. When the fibers reach the bottom of the graduated cylinder, cover the opening of the graduated cylinder, hold the top and bottom with both hands, and turn the graduated cylinder once to disperse the fibers. Is determined. Very good: No undispersed fiber bundles, and each single fiber is well spread 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 single fibers are entangled.

(E) Break length (paper strength) The adhesiveness of the undrawn polyester fiber was evaluated by the strength of the polyester fiber paper. Using a square sheet machine manufactured by Kumagai Riki Kogyo Co., Ltd., the fineness is 1.7 dtex and the fiber length is 5
60% of the polyethylene terephthalate fiber and 40% of the undrawn polyester fiber, which have been subjected to a stretching heat treatment of 40 mm, are well stirred and mixed in water to be dispersed, and have a size of about 25 cm × about 25 c.
A sheet having a basis weight of about 50 g / m ² is prepared. This sheet is sandwiched between filter papers, and using a KRK high-temperature rotary dryer manufactured by Kumagai Riki Kogyo Co., Ltd., the surface temperature of the drum is 140 ° C., the contact time with the drum is 2 minutes, and the drying and bonding heat treatment I do. This heat treated sheet is
The tensile strength was measured according to 8113 and expressed as the breaking length.

[Examples 1 to 4, Comparative Examples 1 to 3] A polyethylene terephthalate chip having an intrinsic viscosity of 0.64 is dried, melted at 300 ° C., and discharged through a spinneret having 1192 holes at 180 g / min. Then, the fiber was taken up at a speed of 1150 m / min, and the fineness of the single fiber was about 1.3 dtex, and Δn was 0.3 mm.
015 undrawn polyester fiber was obtained. The unstretched polyester fiber was made into a tow of about 200,000 dtex, an acid component of 80 mol% of terephthalic acid and 20 mol% of isophthalic acid, and 70 wt% of polyethylene glycol having an average molecular weight of 3000 (based on the weight of the copolymer). In an aqueous dispersion of a polyether / polyester copolymer having an average molecular weight of about 12,000 comprising a glycol component of ethylene glycol, 7
The tow was passed at a speed of 0 m / min, and the water content of the tow was variously changed by adjusting the squeezing ratio with a pair of rollers. Further, the amount of adhesion was changed by variously changing the concentration of the aqueous dispersion of the polyether / polyester copolymer. The tow provided with the polyether / polyester copolymer was supplied to a drum type cutter and cut into 5 mm. Polyether / polyester copolymer adhesion amount in each example,
Table 1 summarizes the measurement results of the water content, dispersibility in water, and breaking length.

[0018]

[Table 1]

In Example 1 in which the polyether / polyester copolymer adhesion amount was 0.04% by weight and the water content was 14% by weight,
The dispersibility in water of the polyester fiber was good, there was no water scattering with a cutter, and the paper strength (tear length) of the polyester fiber paper after papermaking showed an excellent value. In Comparative Example 1 in which the adhesion amount of the polyether / polyester copolymer was 0.02% by weight and the water content was 15% by weight, the dispersibility of the polyester fiber in water was poor, and the surface of the formed polyester fiber paper was poor, resulting in a normal product. The quality to use has not been reached.

Example 2 with 0.08% by weight of polyether / polyester copolymer attached and 6% by weight of moisture and Example 2 with 0.08% by weight of attached polyether / polyester copolymer and 15% by weight of moisture In Example 3, the dispersibility of the polyester fiber in water was extremely good, there was no water scattering with a cutter, and the paper strength (breaking length) of the polyester fiber paper after papermaking.
Also showed excellent values. In Example 4 in which the amount of the polyether / polyester copolymer attached was 0.15% by weight and the water content was 35% by weight, slight water scattering was observed when cutting the tow, but this did not hinder the operation of the cutter. The dispersibility in water of the polyester fiber was extremely good, and the paper strength (rupture length) of the polyester fiber paper also showed an excellent value. In Comparative Example 2 in which the adhesion amount of the polyether / polyester copolymer was 0.08% by weight and the moisture content was 3% by weight, the dispersibility of the polyester fiber in water was good, and there was no water scattering with a cutter. The paper strength (breaking length) of the fiber paper was extremely low. In Comparative Example 3 in which the polyether / polyester copolymer adhesion amount was 0.15% by weight and the water content was 45% by weight, water scattering during tow cutting was extremely large, and the cutter operation became impossible.

Examples 5 to 8 and Comparative Examples 4 to 5 A 10 mol% copolymerized polyethylene phthalate chip having isophthalic acid of 0.64 was dried, melted at 290 ° C., and spun with 1,192 holes. Discharged at 200g / min through a die, withdrawn at a speed of 1100m / min, and fineness of about 1.6d
An undrawn polyester fiber having a tex and Δn of 0.018 was obtained. 0.1% of a polyether / polyester copolymer was added to the undrawn polyester fiber in the same manner as in Examples 1 to 4.
0% by weight was provided, the water content was adjusted to be 15% by weight, and supplied to a drum type cutter, and cut into fiber lengths (1.5 to 25 mm) shown in Table 2 respectively. Table 2 shows the results of measuring the dispersibility in water of the polyester fibers in each example.

[0022]

[Table 2]

[0023]

According to the unstretched polyester fiber for papermaking of the present invention, it is possible to obtain a polyester fiber paper in which the fibers are firmly adhered to each other without impairing the dispersibility of the fibers in water in the papermaking process.

Claims (1)

[Claims] 1. An undrawn polyester fiber having a fiber length of 2 to 20 mm, wherein a polyether / polyester copolymer adheres to the surface of the fiber in an amount of 0.03% by weight or more based on the weight of the fiber. An undrawn polyester fiber for papermaking, having a water retention of 5 to 40% by weight.