JPH02216295A - Production of highly strong polyester fiber paper - Google Patents

Abstract

PURPOSE:To provide the subject fiber paper having a high strength, readily subjected to a calendering process and useful as a tape material for pressing and winding electric wires or cables, etc., by subjecting polyester drawn fibers having a high thermally shrinkage stress to a wet paper-making process. CONSTITUTION:Polyester drawn fibers having a thermal shrinkage stress of 0.08-0.60g/denier at 200 deg.C and polyester undrawn fibers are subjected to a wet paper-making process and subsequently to a thermal pressing calendering process to provide the objective fibers paper. The undrawn fibers are preferably, e.g. those having a birefringence of 0.002-0.03 and a density of 1.335-1.360.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing a high-strength polyester fiber paper suitable for tape material for holding and winding electric wires.

<Conventional technology> In recent years, against the backdrop of increasingly dramatic technological innovations and social trends toward lighter, thinner, and smaller paper, the performance requirements for paper have become increasingly strict. Traditionally, natural cellulose, rayon, and vinylon have been mainly used as raw materials for papermaking, but as the required performance becomes more sophisticated, polyester fibers are recently replacing some of the raw materials for papermaking. This is because polyester fiber has excellent mechanical properties, electrical properties, FNN thermal 1 method stability, and hydrophobicity.Coupled with the increasing sophistication of required performance due to the sophistication of industrial structures, polyester fiber will become more popular in the future. It is thought that the replacement of

However, most of the conventional polyester fibers for paper making are merely slightly improved versions of polyester '7T4ta for spinning. For example, JP-A-5
No. 5-110545 discloses polyester, T-type fiber,
This is an attempt to improve the bulk and texture of paper by making it into a Y-shaped, double-sided shape, etc.
208500, JP 60-224899, and JP 62-49394 propose surface treatment agents that improve the dispersibility of polyester fibers in water, and JP 63-203875 proposes polyester fibers. The cross-sectional polyester fiber is treated with block cobolyether ester,
This is a proposal to improve the hydrophilicity of polyester fiber paper.

However, recently, attention has been focused on the properties of polyester,
Sheets made of polyester III are increasingly being used in the industrial material field. Particularly, polyester spunbond has been widely used as tape for holding and winding electric wires in the field of electrical materials because of its high strength. However, sheets produced by the spunbond method have a problem in that they have large basis weight irregularities and furthermore, it is difficult to achieve a low basis weight of 50 g/TIt or less, so sheets produced by the wet papermaking method are attracting attention. However, due to the limitations of conventional polyester fibers for papermaking due to water dispersibility, most of the fiber lengths are 20 mm or less, and furthermore, as mentioned above, no special improvements have been made in terms of physical properties, so wet-processing is difficult. Even if the paper was subjected to thermocompression calendering after papermaking, bonoester fiber paper with sufficient strength could not be obtained.

<Problems to be Solved by the Invention> The present invention overcomes the problem of providing polyester fiber paper with excellent uniformity and high strength using a wet papermaking method, which has not been possible with the prior art.

Means for Solving the Problems> The present invention provides a method for producing polyester fiber paper by wet paper-making from drawn polyester fibers and undrawn polyester fibers, and then subjecting the paper to thermocompression calendaring. Heat shrinkage stress is 0.08~0.60g
This is a method for producing high-strength polyester fiber paper, which is characterized by using polyester drawn fibers of /denier.

As the polyester fibers of the present invention, polyester fibers made of polyethylene terephthalate and polyesters mainly composed of polyethylene terephthalate are preferably used, or modified fibers thereof,
Examples include basic dye-dyeable polyester, Ift-flammable polyester, electrostatic polyester, and the like.

In addition, polyester drawn fibers (binder fibers) are
In order to obtain sufficient thermal adhesion between fibers, the birefringence index is 0.0.
02 to 0.03 and a specific gravity of 1.335 to 1.360. Single yarn fineness is 0.2 to 5 denier.

Preferably, the fiber length is 3 to 20 mm, and the fiber cross section is circular or nearly circular. Further, the mixing ratio of the binder and the fibers is preferably 30 to 70% from the viewpoint of the strength of the thermocompression calendered paper, the heat shrinkage properties, and the air permeability.

The polyester drawn fibers constituting the skeleton of the present invention and the polyester undrawn fibers having a thermal bonding effect are mixed and dispersed using a pulper or a heater, and then mixed and dispersed in a circular mesh, y
After paper making with Ω mesh or Fourdrinier paper machine, dry V-temperature 11
After drying at 0 to 150°C, it is rolled up to form a paper sheet. Next, the paper sheet is pressure-calendered at a temperature above the crystallization temperature and below the melting point of the polyester, for example from 180 to 240°C, particularly preferably from 200 to 240°C. Calender processing can be done in one stage or in multiple stages, but the calender linear pressure at that time is 10 to 200 Kg/cm.
is desirable. If it is less than 10 Kg/cm, sufficient pressure will not be applied and the paper will not be strong enough, and if it exceeds 200 Kg/cm, the cross-sectional deformation of the constituent fibers will become severe and air permeability will decrease, which is not preferable. As a result of various studies on the relationship between the strength of calendered paper and the physical properties of polyester fibers, the present inventors found that the heat shrinkage stress of the main polyester fiber has a large effect on the strength of calendered paper. .

That is, the drawn polyester fiber of the present invention has a heat shrinkage stress of 0.08 to 0.60 M denier at 200°C. If the heat shrinkage stress is less than o, oag, z' denier, sufficient paper strength will be (q, conversely, o, 6
If it exceeds og/denier, the shrinkage stress causes the paper to break easily during calendering, and the paper strength also decreases. In addition, the more preferable range of heat shrinkage stress is 0.10
Must be ~0.50c+/denier. The heat shrinkage stress of regular polyester short fibers blended with cotton or wool is 0.
．． Lower than 08q/denier.

Although it is not clear why the strength of calendered paper is greatly affected by heat shrinkage stress, it is thought that shrinkage stress changes the state of pressure bonding with the binder fiber i-fibers, thereby changing the paper strength. The heat shrinkage rate of the polyester drawn fiber is not particularly limited, but the heat shrinkage rate suitable for the present invention (relaxation shrinkage rate in an atmosphere of 200°C) is necessarily 8 to 20%. Paper strength tends to decrease,
If it is higher than 20%, the paper will tend to break during calendering and its strength will also decrease. Furthermore, the fiber form of the polyester fiber is the same as that of the undrawn binder fiber, with a single fiber fineness of 0.2 to 5 deniers and a fiber length of 3 to 20 mm.

The fiber cross section is preferably circular or nearly circular. If the single yarn fineness is smaller than O12 denier, the air permeability of the paper will deteriorate, and if it exceeds 5 denier, the paper strength will decrease. Also, if the fiber length is shorter than 3mm, it will not be strong enough, and 20mm
If it exceeds this value, it becomes difficult to disperse the fibers in water, and the paper tends to become uneven.

Here, the polyester drawn fiber in the present invention can be obtained, for example, by the following method. That is, the intrinsic viscosity is 0.
After melt-spinning ordinary polyester chips of 5 to 0.8 dl/C1, they are stretched in a hot water bath, bowed, subjected to tension heat treatment and/or relaxation heat treatment, and cut into predetermined lengths. Heat shrinkage stress is measured by sampling fibers before cutting, and it is thought that heat shrinkage stress is mostly determined by the degree of orientation of molecular chains in the amorphous portion. Therefore, it is thought that it is determined by melt spinning conditions such as intrinsic viscosity, discharge polymer temperature, and spinning speed, as well as stretching conditions such as drawing temperature and draw ratio, tension heat treatment temperature, relaxation heat treatment temperature, etc., but usually the draw ratio, tension Heat treatment temperature.

By combining various conditions such as the relaxation heat treatment temperature, the heat shrinkage stress can be varied over a fairly wide range. That is, an increase in the stretching ratio and a decrease in the relaxation heat treatment temperature are in the direction of an increase in heat shrinkage stress. Further, regarding the tension heat treatment temperature, the heat shrinkage stress becomes maximum at a certain temperature.

<Example> The present invention will be specifically explained below using Examples.

Each evaluation in the examples was performed according to the following method.

(1) Single fibers of 125 denier are sampled from polyester tow before heat shrinkage stress cutting.

This 125 denier fiber bundle was hung on the upper and lower hooks of a KE-II heat shrinkage stress measuring instrument manufactured by Kanebo Engineering Co., Ltd. (the interval was about 5 cm), and then the fiber bundle was tied to form a 250 denier fiber bundle. Next, an initial load of 15g was applied to the 250 denier fiber bundle, and it was heated for 120sec/300'C.
The temperature is raised until the fiber melts at a heating rate of , and the relationship between temperature and thermal shrinkage stress is determined.

(2) Paper strength Measured according to the tensile strength test method of JIS P8113-1976. However, the weapon is 50mm, the width is 15mm,
The tensile speed was 50 ml/min, and the paper strength (K
! ]/15mm) was determined. Measurements were repeated five times in each of the vertical and horizontal directions, and the average value of each was taken as the vertical and horizontal strength.

Examples] ~4. Comparative Examples 1 to 2 Contains 0.07% by weight of titanium dioxide and has an intrinsic viscosity of 0.6
4 dl/(I polyethylene terephthalate chips 3
It was melted at 00'C, discharged at 285C through a spinneret having 600 round holes, and taken off at a speed of 565 m/min to obtain an undrawn yarn with a single filament fineness of 9.1 denier.

This undrawn yarn was drawn 1 time to form a tow of 650,000 denier, stretched in two stages in a hot water bath, subjected to tension heat treatment, 13 and/or relaxation heat treatment, and cut to a length of iomm. Terephthalate fibers were obtained. At this time, various combinations of stretching ratios and heat treatment conditions were used to obtain polyester w4G# having different heat shrinkage stresses. Incidentally, the single yarn fineness of the polyester fiber was within the range of 1.7 to 2.1 denier. The polyester fiber is 60% by weight, the single fiber fineness is 1.1 denier, the fiber length is 5 mm, and the birefringence index is 0.0.
12, specific gravity is 1.340.

40% by weight of non-crimped polyethylene terephthalate undrawn fibers with a circular fiber cross section were placed in a heater, sufficiently mixed and dispersed, then sent to a cylinder paper machine and dried at a Yankee dryer surface temperature of 120'C. , rolled up. Calendar roller surface temperature 230
°C, calender linear pressure 120Kg/cm, processing speed 2
Polyethylene terephthalate fiber paper of 32 m/min was obtained. The calendering condition at this time and the strength of the resulting paper were determined using polyester fiber]
Table 1 shows the corresponding drawing ratio, tension heat treatment temperature, relaxation heat treatment temperature, and heat shrinkage stress at 200°C of the obtained polyester m-fiber.

Effects of the Invention According to the method of the present invention, polyester IIi fiber paper with good calendering performance and high strength can be obtained by increasing the heat shrinkage stress of polyester m-fibers compared to ordinary polyester m-fibers. Can be done.

Claims (1)

[Claims] 1. A method for producing polyester fiber paper by wet paper making from drawn polyester fibers and undrawn polyester fibers, and then subjecting to thermocompression calendering.
A method for producing high-strength polyester fiber paper, comprising using drawn polyester fibers having a heat shrinkage stress of 0.08 to 0.60 g/denier at 0°C.