JPH0250876B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to polyester screen shear, and its purpose is to provide a screen shear with excellent quality and less generation of white powder scum during weaving. Polyester monofilaments, especially polyethylene terephthalate monofilaments, have many excellent properties and have traditionally been used in screen shearing, and in recent years have been used in electronics,
It has also entered the field of high-end printing, and demands for finer monofilament, higher strength, and improved durability are increasing. However, when weaving screen shears using such polyester monofilaments, white powder scum is likely to be generated, causing various problems. Problems caused by the generation of white powder scum are particularly common when weaving high-density screen shears of 250 meshes or more using polyester monofilament with a fineness of 20 denier or less as warp threads. This white powder scum is generated by repeated abrasion of the reed, and when using polyester monofilament with a fineness of more than 20 denier, the reed width (the gap between the reed and the cross-sectional diameter of the filament) is wide, so the abrasion occurs. The degree of this is mild and its influence is small. Moreover, since the fineness is high, no actual damage to the gray fabric due to the generated white powder scum is observed. However, when using polyester monofilament with a fineness of 20 deniers or less, the reed gap is usually smaller than the cross-sectional diameter of the filament, so the filament is repeatedly subjected to strong abrasion, resulting in significant surface damage and white powder scum. . Therefore, this white powder scum clogging causes warp breakage and warp streak spots on the gray fabric, resulting in a significant deterioration in both quality and production efficiency. In order to solve such problems, the applicant
We previously proposed a polyester monofilament for screen shearing with a breaking elongation of 35 to 60% (Japanese Patent Application Laid-open No. 16948/1983). When using this monofilament, it is possible to prevent the generation of white powder scum during screen shear weaving, but since a high elongation monofilament is used, the strength of the monofilament inevitably decreases, and the resulting screen A new problem arose in that the shear's tensile strength, elastic recovery, and durability decreased. As a result of intensive studies in an attempt to eliminate the above-mentioned drawbacks, the present inventor has discovered that by changing the surface condition of the polyester monofilament used, white powder scum occurs during screen shear weaving without deteriorating the properties of screen shear. We have discovered that this can be prevented, and have arrived at the present invention. That is, the present invention is a polyester screen shear characterized by being made of a polyester monofilament with a fineness of 20 denier or ^less and having at least 30 hemispherical and/or semiellipsoidal convex portions on the surface and a fineness of 20 denier or less. . The polyester monofilament referred to in the present invention is primarily a monofilament made of polyethylene terephthalate. However, ethylene terephthalate is the main repeating unit, and a third component other than the terephthalic acid component and the ethylene glycol component is
Copolymerization of a small proportion of components (usually 20 mol% or less) and/or
Alternatively, it may be a monofilament made of mixed polyester. The degree of polymerization of the polyester is such that the intrinsic viscosity measured with a 0-chlorophenol solution at 35°C is 0.5 or more, preferably 0.7 to 1.0. Further, on the surface of the polyester monofilament according to the present invention, convex portions having a hemispherical shape and/or a semiellipsoidal shape are present. In addition, in order to obtain molded products from these thermoplastic resins,
It is heated to soften and melt, or it is dissolved in an appropriate solvent and molded into a resin, film, or fiber by injection, extrusion, film formation, spinning, or other molding processes. In the present invention, smooth convex portions exhibiting a hemispherical shape and/or semiellipsoidal shape are provided on the surface of the molded product made of the thermoplastic resin. Because such smooth convex portions are formed, the surface is less likely to be damaged, the friction property (smoothness) is improved, and the generation of white powder scum is significantly prevented. In order to achieve the effect of preventing the generation of white powder scum,
The number of protrusions on the surface of the polyester monofilament must be 30 pieces/ ^100μ2 or more, and their size is ^3μ2 to ^15μ2 in base area and 0.5μ to height.
2.0μ is preferable. A height of 100 protrusions/ ^μ2 is sufficient for the number of protrusions on the surface of the polyester monofilament, and in order to increase the number of protrusions higher than that, it is necessary to add a large amount of polysulfone or silica gel.
There is a tendency for the strength of the monofilament to decrease. As a method for obtaining the polyester monofilament used in the present invention, for example, the glass transition temperature is adjusted to 150°C or higher at any stage before or after the completion of polymerization of the polyester, and the polyester monofilament is amorphous and non-reactive with the polyester. There is a method of melt spinning a composition to which 1 to 15% of polymer is added. Examples of the amorphous and non-reactive polymer having a glass transition temperature of 150° C. or higher include polysulfone compounds, and compounds having the following repeating units are particularly preferred. Furthermore, the polyester monofilament having convex portions on the surface used in the present invention can also be obtained by adding silica gel to polyester and performing melt spinning. Furthermore, additives such as catalysts, ether formation inhibitors, stabilizers, flame retardants, antistatic agents, hydrophilic agents, colorants, fluorescent whitening agents, and matting agents may be mixed into the polyester. good. Such a monofilament may be melt-spun as a multifilament and then split, or may be melt-spun as a monofilament from the beginning. The above polyester monofilament has a fineness of
Targeting monofilaments of 20 denier or less,
The effect is particularly remarkable when monofilaments with a fineness of 5 to 15 deniers are targeted. As mentioned above, if the fineness is greater than 20 denier, there is no actual harm even if it is a conventional monofilament, and there is no need to form convex portions on the surface of the monofilament as in the present invention. In the present invention, a polyester monofilament having a fineness of 20 denier or less and having at least 30 hemispherical and/ ^or semiellipsoidal convex portions on the surface is used. By forming smooth protrusions on the monofilament surface, the coefficient of dynamic friction between the fibers and the metal is reduced, improving smoothness and making the monofilament surface less likely to be scraped off. The generation of white powder scum is significantly reduced.
Furthermore, in order to obtain screen shear with good tensile strength, elastic recovery force, and durability with conventional polyester monofilaments with a flat surface, the strength of the monofilament was increased to 5.0 g/de or more, and the breaking strength in the stretching curve was increased. Young's modulus at 80% part is 60~
When using 140Kg/ ^mm2 , it was not possible to prevent the generation of white powder scum during screen shear weaving, but the above-mentioned monofilament with convexities formed on the surface has a strength of 5.0g/de or more and a loading curve of 140Kg/mm2. Young's modulus at 80% of the breaking strength at 60
Since the generation of white powder scum is prevented even at ~140 Kg/mm ² , there is no problem during screen shear weaving, and screen shear with excellent tensile strength, elastic recovery power, and durability can be obtained. The Young's modulus at 80% of the breaking strength in the loading curve is the breaking strength a in the loading curve shown in the figure.
From the tangent line b drawn to the stretching curve at the position of 80% strength a', calculate the strength increment s at 1% extension based on the contact point c, and use the formula 12.4 x s/de x 100. Young's modulus. Strength is 5.0g/de or more,
This Young's modulus is 60~140Kg/mm ² , preferably 100~
Screen shear woven using monofilament with a density of 120 kg/mm ² has improved tensile strength and durability, and has a large elastic recovery force, allowing it to instantly return to its original state after being deformed by rolling. Therefore, clear and good printing can be performed. Such products have a strength of 5.0 g/de or more and a Young's modulus of 60 to 60 at the 80% point of breaking strength in the stretching curve.
The polyester filament is 140Kg/ ^mm2 .
A polyester having an intrinsic viscosity of 0.5 or more, preferably 0.7 to 1.0 as measured with a 0-chlorophenol solution at 35°C and containing a polysulfone compound, silica gel, etc., is melted and spun at a spinning speed of about 800 to 1300 m/min. Spun and stretched 3.4-4.0 times, then
It can be obtained by heat setting at 120-160°C. As explained above, the polyester screen shear of the present invention dramatically reduces the generation of white powder scum during weaving, can prevent warp breakage and warp streak spots on gray fabric, and has excellent tensile strength, elastic recovery power, and durability. It will be of excellent quality. Hereinafter, the present invention will be explained in more detail with reference to Examples. Examples 1 to 4, Comparative Examples 1 to 2 Polyethylene terephthalate with an intrinsic viscosity of 0.64 measured in a 0-chlorophenol solution at 35°C was After adding various amounts of polysulfone compounds having repeating units as shown in the following table and melting them,
The fibers were spun and wound at a spinning speed of 1000 m/min. then
The film was stretched 4.27 times with rollers heated to 83°C, heated for 0.03 seconds in a slit heater at 140°C, and wound at a speed of 600 m/min to obtain a monofilament of 11 de. Various characteristic values of the obtained monofilament were as shown in the following table. A part of the obtained monofilament was used for the warp and weft to weave a plain weave of 300 meshes.
The tear strength was measured using an Instron tensile tester at a head speed of 5 cm/min for a sample cut into a size of 10 mm in width and 50 mm in length from a screen shear obtained by scouring at 80°C for 20 minutes in an alkaline bath of was measured. The results are also shown in the table below.

[Table] Among the characteristic values in the table, the interfiber friction coefficient μ _FF was measured by the radar method at a speed of 300 m/min, and the rubbing white powder development time was measured using 10 fibers stretched with a tension of 5 g. monofilament,
The material was rubbed with a reed for 300 mesh screen shear weaving at a reed speed of 140 strokes/min, and the time until white powder began to be observed with the naked eye was determined. As is clear from the table, when the number of protrusions on the monofilament surface is 30/100μ2 or ^more , the generation of white powder scum during screen shear weaving is reduced, and the screen shear has excellent tensile strength, elastic recovery power, and durability. is obtained. Comparative Example 3 In Comparative Example 1, the stretching ratio was lowered and the strength
A monofilament of 4.4 g/de and elongation of 45% was obtained.
The rubbing white powder development time of this monofilament is 100
20 minutes, and white powder scum was less likely to occur.
% elongation elastic recovery rate is 34.6%, which is poor elastic recovery force.Furthermore, the strength is low, and the Young's modulus at 80% of the breaking strength in the loading curve is as low as 46 kg/ ^mm2 . The tensile strength was only 4.93Kg, and the tensile strength and durability were poor. Examples 5 to 7, Comparative Example 4 Polyethylene terephthalate with an intrinsic viscosity of 0.75 measured with a 0-chlorophenol solution at 35°C,
Adding the polysulfone compound used in Example 1 or silica gel (average particle size 23μ) in the polymerization step,
A monofilament of 11 de was obtained by spinning and drawing under the same conditions as in Example 1. The various characteristic values of the obtained monofilament and the tear strength of the screen shear woven under the same conditions as in Example 1 are shown in the following table. For comparison, the following table also shows the characteristic values of monofilaments obtained under the same conditions as Examples 5 to 7 without adding the polysulfone compound and silica gel.

[Table] In Comparative Example 4, in which there are no convex portions on the monofilament surface, white powder scum is generated in a very short time, but in the present invention, which uses a monofilament that has convex portions on the surface, white powder scum is not generated. Screen shear with excellent tensile strength, elastic recovery, and durability can be obtained.

[Brief explanation of drawings]

The figure is a graph for explaining a method for measuring Young's modulus at a position of 80% of the breaking strength in a stretching curve.

Claims (1)

[Scope of Claims] 1. A polyester screen shear comprising a polyester monofilament having a fineness of 20 denier or ^less and having at least 30 hemispherical and/or semiellipsoidal convex portions on its surface and a fineness of 20 denier or less. 2 The breaking strength of polyester monofilament is
5.0g/de or more, 80 breaking strength in loading curve
The polyester screen shear according to claim 1, which has a Young's modulus of 60 to 140 Kg/mm ² at the % position. 3. The polyester screen shear according to claim 1 or 2, which has a fineness of 5 to 15 deniers. 4. The polyester screen shear according to any one of claims 1 to 3, wherein the polyester is polyethylene terephthalate.