JP2503008B2 - High mesh screen Polyester monofilament for weaving - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a polyester monofilament for screen gauze, and particularly to a high-strength, fine denier polyester monofilament with improved weavability in high-mesh screen gauze.

[Conventional technology]

Polyester monofilaments, especially polyethylene terephthalate monofilaments, have been widely used as materials for screen gauze due to their many excellent fiber characteristics. In recent years, with the progress of electronics and the precision of printing, the screen mesh has been made more and more highly meshed, and the demand for higher strength and fine denier of monofilaments has been increased.

However, when weaving a screen gauze using polyester monofilament, it is known that white powder scum occurs and causes various problems. The obstacle caused by the generation of the white powder scum is remarkable when a polyester monofilament having a fineness of 15 denier or less is used and a high mesh screen gauze of 250 mesh or more is woven. This white powder scum is generated by rubbing of the reed, and particularly when using a polyester monofilament having a fineness of 15 denier or less, when weaving a high mesh screen gauze, usually the reed spacing is almost equal to the filament cross-section diameter, It is a little large, and the filament is constantly subjected to strong abrasion by the reed and the filament surface is easily scraped, so white powder scum mixed with the fiber scraps scraped by the reed and the dropped oil agent is generated. . Due to the clogging of the white powder scum, warp breakage and unevenness of warp lines in the raw fabric occur, which significantly deteriorates both the quality and the production efficiency of the screen gauze.

On the other hand, for high-precision printing, when obtaining a high-mesh screen gauze of 250 mesh or more, in order to improve the open area in the gauze, the finer the fineness of the monofilament used, the better, for example, 15 denier or less A thin monofilament is needed. However, as the denier becomes finer, the strength of the thread decreases, and while the thread of the screen gauze often breaks during weaving, it also causes a decrease in the tear strength of the gauze, causing various troubles in the post-processing step of the gauze. Therefore, development of a fine denier and high strength monofilament yarn is strongly desired.

As a general method for producing high-strength monofilaments with such fine denier, a method in which a high-polymerization degree polyester is used, melt-spun to obtain an undrawn yarn, and the undrawn yarn is drawn at a high draw ratio There is. However, although the monofilament obtained by this method exhibits high strength and high Young's modulus, the elongation is inevitably reduced, the rigidity becomes high, and the monofilament becomes a hard monofilament. The white powder scum, which is mainly composed of the fiber scraps that are scraped and scraped by the reed, is generated rapidly, that is, the white powder scum is generated, so that the weaving cannot be performed.

Further, in order to reduce the generation of white powder scum, a high-strength, high Young's modulus monofilament having a subtle unevenness on the surface has been proposed by incorporating an amorphous and non-reactive polymer or silica gel into polyester. However, according to this method, since the non-crystalline and non-reactive polymer or silica gel is contained in the monofilament, the strength and elongation of the monofilament are lowered. The tensile strength, elastic recovery, and durability of the obtained screen gauze were reduced, and the screen gauze was not sufficiently satisfactory.

It is also treated with a reactive silicone resin, and the surface has 0.1 to 0.7
A monofilament containing the resin by weight% has been proposed (JP-A-58-169540). In this case, a relatively small amount of the treating agent having a relatively high viscosity is uniformly attached to the surface of the monofilament. Is extremely difficult, and because the adhesiveness of the silicone resin that has undergone a crosslinking reaction on the surface of the polyester filament is insufficient, part of it peels off during warping or weaving and is woven into the screen gauze, which reduces the quality of the gauze. Alternatively, there is a problem that the printing accuracy is deteriorated by peeling off during the finishing process of the screen gauze.

A filament in which a fine particle substance is attached to the filament surface or coated with an adhesive water-soluble resin together with the fine particle substance has been proposed (Japanese Patent Laid-Open No. 59-1164412).
The filament obtained by such a method has a reduced dynamic friction coefficient and improved smoothness, but the fine particles do not uniformly adhere to the surface of the filament and its adhesive force is insufficient. There was a problem that the fine particles fell off due to the strong rubbing due to the reeds during weaving and were woven into the screen gauze, degrading the quality of the screen gauze. Further, when a water-soluble resin is used, it is difficult to uniformly remove the particulate matter in the refining process of the screen gauze, and there is a problem that the opening accuracy of the high mesh screen gauze is lacking.

Furthermore, the intrinsic viscosity is 0.7 to 1.2, and the content of titanium oxide is
A monofilament for screen gauze, which has high toughness, high modulus, and improved fibrillation property on the fiber surface, has been proposed, which is obtained from a polyester having 0.1 wt% or less and a carboxylic acid residue amount of 25 eq / 10 ⁶ or less. Kai 61-28
However, since this monofilament has a high coefficient of friction with metal, the problem of filament abrasion due to reeds could not be solved.

Therefore, despite the various proposals above,
It is the current situation that no high-mesh high-strength screen gauze with satisfactory practical performance is known.

[Problems to be solved by the invention]

In order to solve the above problems and drawbacks, the present inventors have developed a white powder scum of a high-strength polyester monofilament and a friction coefficient, smoothness, surface morphology uniformity of the high-strength polyester monofilament, or a substrate of a polymer constituting the monofilament. As a result of diligent studies on the relationship between the internal structure centered on the crystal structure, and the finishing oil that adheres in the spinning process, as a result of the higher draw ratio, it becomes a highly oriented yarn, while the internal structure of the monofilament also changes. However, the crystal size, the degree of crystal orientation, and the degree of non-crystalline orientation also change, and in addition, the macroscopic density also changes, but it was revealed that there is a close relationship between chipping on the reed and density. That is, it has been clarified that the effect of preventing abrasion with a reed appears only in a specific density range.

On the other hand, as the draw ratio is increased, the obtained high-strength monofilament is apt to become a monofilament having large Wooster yarn unevenness because the shape thereof is rapidly changed during neck drawing. It was revealed that this Worcester yarn unevenness is closely related to the scraping on the reed.

However, it was revealed that the causal relationship between and was particularly closely related to fine denier and high-strength monofilaments, and the occurrence of white powder scum as a main component in the reeds of fine denier and high-strength monofilaments was significantly reduced. , Fine denier that was impossible to weave until now,
The weaving of high-strength monofilaments has become possible, and it has succeeded in obtaining a high-strength screen gauze with a high mesh, which has led to the present invention.

That is, the object of the present invention is to solve the problems and drawbacks of the known polyester monofilament for high-strength screen gauze, high strength with excellent weavability, fine denier polyester monofilament, particularly useful for high-mesh screen gauze To provide polyester monofilament.

[Means for solving problems]

The object of the present invention is to melt-spun polyester to obtain an undrawn yarn, cool the undrawn yarn to a temperature not higher than the glass transition point Tg of polyester at a position within 2 m below the spinneret, and then heat by combining in multiple stages. Rolling temperature of 90 to 120 depending on the roller
℃, heat setting temperature 90-140 ℃ multi-stage drawing fineness obtained 6-15 denier, breaking strength 5.5-8.0g / D, density 1.3
It can be achieved by a high-mesh screen polyester monofilament for weaving, characterized by having a Worcester yarn unevenness of 580 to 1.3700 g / cm ³ and 0.3 to 1.0.

In the present invention, the monofilament has a density of 1.3580 to 1.3700 measured according to a density measuring method described later.
It is important to be in the range of g / cm ³ , preferably 1.3
The range of 580 to 1.3670 g / cm ³ is good. Density 1.3580g / cm ³
If it does not satisfy the above condition, the heat shrinkage of the obtained monofilament is high, the heat stability of the obtained screen gauze is poor, and it is not suitable for precision printing in which the accuracy of the opening is important. Further, when the density is higher than 1.3700 g / cm ³ , the generation of shavings of monofilament and white powder scum on the reed extremely increases. Therefore, the breaking strength is 5.5 g / d or more, and the monofilament having the effect of suppressing the generation of white powder scum has a density of 1.3580 to 1.3700 g / cm.
It is important to satisfy the range of ³ .

More preferably, from the microstructure surface of this monofilament, the crystal size in the (100) plane obtained by wide-angle X-ray diffraction is in the range of 20 to 30 angstroms, and the density distribution in the cross-sectional direction of the monofilament is: By further lowering the surface layer portion of the monofilament from that of the central portion, a further effect can be exhibited.

In the present invention, it is necessary that the Worcester yarn unevenness measured according to the Worcester yarn unevenness measuring method described below is within the range of 0.3 to 1.0, and preferably within the range of 0.3 to 0.8.

That is, in the present invention, even if the above density is satisfied, the occurrence of white powder scum extremely increases if it is larger than the Worcester yarn unevenness of 1.0. Worcester yarn unevenness
0.3 is a limit value that can be achieved by the current technology, and no Wurster yarn unevenness of 0.3 or less is known.

It is not clear why the high-strength monofilament specified by the density and the Worcester yarn unevenness has a remarkable effect of suppressing the generation of white powder scum. However, it is assumed that the monofilament with an internal structure that increases the amorphous content by lowering the density and fixes the molecular chains with fine crystals absorbs the strong rubbing energy of the reeds during weaving. It has a softness and is hard to be scraped by the reed, and by making the Worcester yarn unevenness uniform, the morphology of the yarn surface is made uniform, and the synergistic effect of preventing scraping on the reed due to morphological change is an excellent white powder scum. It is considered that the suppression effect of That is, it is considered that the effects of the internal structural surface and the morphological surface of the monofilament act synergistically to exert a great effect on the scraping by the reed.

The monofilament of the present invention has a fineness of 6 to 15 denier, preferably 10 denier or less. That is, if the denier is 15 denier or more, improvement of the opening area cannot be expected in the case of high mesh of 250 mesh or more. The monofilament of the present invention has a breaking strength of 5.5 to 8.0 g / D, preferably 6.0 to 7.0 g / D.
Is. If it exceeds 8.0 g / D, white powder scum is often generated.

The polyester monofilament of the present invention is a monofilament made of polyethylene terephthalate (hereinafter,
The main target is a monofilament. Especially ethylene terephthalate is the main repeating unit,
Terephthalic acid (TPA) component and ethylene glycol (E
G) components other than phthalic acid, adipic acid, sebacic acid, oxalic acid, and other dicarboxylic acids, propylene glycol, butanediol, polyethylene glycol, polytetramethylene glycol, and other diols, or 5-sodium sulfoisophthalic acid, etc. Small amount of ingredients (usually
It may be a monofilament made of polyester which is copolymerized and / or mixed (20 mol% or less).

The degree of polymerization of the polyester is such that the intrinsic viscosity measured with an O-chlorophenol solution at 35 ° C. is 0.5 or more, preferably 0.7.
~ 1.4 is suitable.

Further, for the purpose of improving the matte effect and weaving property, a polymer containing 0.15 to 5% of fine particles of titanium dioxide, silicon dioxide or the like, or particles formed in the polymer in the polymer manufacturing process, that is, a polymer containing so-called internal particles May be Further, a polymer containing an ultraviolet absorber may be used in order to prevent halation during exposure to ultraviolet light in the screen plate making process.

The polyester mesh monofilament for high-mesh screen gauze fabric of the present invention having such specific fineness, breaking strength, density and Worcester yarn unevenness is usually wound at a winding speed of 600 using a pressure melt type or extruder type melt spinning machine. It is wound up at a speed of up to 2000 m / min to obtain an unstretched yarn, and further stretched 3.5 to 6.0 times by changing the rotation speed of a heating roller combined in multiple stages. What is important in such a process is that, for example, in order to make the Wooster yarn unevenness of the obtained monofilament 1.0 or less, cooling air is forcibly applied to the monofilament within a position within 2 m below the spinneret to make the monofilament Tg or less. Until it is cooled. Then, stretching is performed by heating rollers combined in multiple stages. Moreover, the density of the monofilament necessarily depends on the heat setting temperature and the time, and therefore cannot be generally stated. However, the stretching temperature and the heat setting temperature are determined so that the monofilament having the density range defined in the present invention can be obtained. The neck stretching temperature must be 90 to 120 ° C, and the heat setting temperature must be 90 to 140 ° C.

In addition, a direct drawing method in which, after spinning, the film is not wound once but continuously drawn can be adopted. Further, a method of producing a stretched monofilament by spinning as a multifilament and separating the fibers can also be adopted.

The methods for measuring the breakage strength, density, and Worcester yarn unevenness of the monofilaments specified in the present invention were as follows.

Breaking strength: Tensile length of 20 cm and speed of 20 cm / min in a sample with an Instron universal tensile tester in an atmosphere of a temperature of 20 ° C. and a relative humidity of 65%. The value is divided by.

Density: The apparent density d ′ of the monofilament was obtained by the density gradient tube method using a density gradient composed of carbon tetrachloride / n-heptane, and the density d was calculated according to the following formula.

d = [d ′ (1-A / 100)] / {1- (A × d ′) / 100B} In the above formula, A is the amount of additives (fine particles, etc.) other than the polymer contained in the polyester. (% By weight) and B
Is the density (g / cm ³ ) of additives (such as fine particles) other than the polymer contained in the polyester.

Wooster thread unevenness tester: USTER TESTER MONITOR C
SERVICE SELECTOR NORMAL, RANGE OF SCALE
(%) ± 12.5, the value measured under the condition of a yarn speed of 200 m / min.

〔Example〕

 Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1 Polyethylene terephthalate containing an intrinsic viscosity of 0.84 and a titanium dioxide content of 0.3% by weight obtained from an orthochlorophenol solution at 25 ° C. was drawn at a spinning temperature of 295 ° C. using a spinneret having four holes to obtain a drawn yarn fineness of 12 denier. As described above, the discharge amount was changed, melt spinning was performed, and a finish oil was applied and wound.

The surface temperature of the obtained unstretched monofilament is 60 to 24
As shown in Table 1, the draw ratio, the distribution of the draw ratio, and the hot roll temperature were changed with a multistage drawing machine having three hot rolls controllable at 0 ° C. to obtain drawn monofilaments having the physical properties shown in Table 1. The amount of carboxylic acid residues in this drawn monofilament was in the range of 40 to 50 eq / 10 ⁶ g.

This stretched monofilament was stretched at a tension of 10 to 14 g / piece, and 200 monofilaments were rubbed with a 300 mesh screen gauze woven reed at 400 strokes / minute, and the amount of white powder scum generated on the reed was 15 sequentially from the start of rubbing. 30 minutes
Minutes, 60 minutes each time, observe with the naked eye, and the result is the first
Shown in the table.

In addition, the white powder scum after 60 minutes of rubbing was observed with a microscope, and the amount of fiber scraps in the white powder scum was observed.
It is also shown in the table.

In Table 1, Level 2 satisfying the requirements specified in the present invention,
Nos. 3 and 4 are high-strength monofilaments with less white powder scum. On the other hand, in Level 1, the density of white powder scum is small, but the density is low, and the shrinkage rate of boiling water is high, so that the thermal stability of the screen gauze is poor and uneven opening occurs during processing of the gauze. In Level 5, the density was high, the amount of white powder scum was large, and the white powder scum contained a large amount of fiber shavings. Further, since the level 6 was carried out at a drawing temperature of 85 ° C. during drawing, the Worcester yarn unevenness was large, and a large amount of white powder scum containing a large amount of fiber shavings was also generated.

Example 2 In accordance with Example 1, the atmosphere under the spinneret at the time of melt spinning was controlled by heating with a heating cylinder, and wound at a winding speed of 900 m / min, and subsequently drawn at a drawing stage with a multi-stage drawing machine having three heating rolls. Was drawn at a temperature of 92 ° C, a heat setting temperature of 130 ° C, and a total draw ratio of 4.5, and a monofilament with an intrinsic viscosity of 0.72, a single yarn denier 9D, a breaking strength of 6.2g / D, a density of 1.3640g / cm ³ , and a Wooster yarn unevenness of 0.72. Got

A screen gauze having a weaving density of 300 filaments / inch was woven with this monofilament using a sulzer loom. The occurrence of white powder scum on the reed during weaving is small, and when observing the white powder scum with a microscope, there is little fiber scrap due to the scraping of monofilaments, and weaving can be performed up to about 200 m without the occurrence of warp yarn breakage. did it. The strength of the obtained screen gauze was 30 kg / 5 cm or more, and an extremely high-strength screen gauze was obtained.

Comparative Example 1 Stretching in Example 2 was performed with a heat pin having a surface temperature of 115 ° C.
Conducted at a total draw ratio of 4.0 using a hot plate at 30 ° C, intrinsic viscosity 0.72, single yarn denier 9D, breaking strength 6.3g / D, density 1.37.
A monofilament having a Worcester yarn unevenness of 1.02 at ³ g / cm ³ was obtained. When this monofilament was woven in the same manner as in Example 2, white powder scum was often generated in the reed during weaving, and many fiber shavings were observed in the white powder scum by microscopic observation. Occurred, and weaving could not be performed.

Example 3 According to Example 1, a known chimney device was used for the spinning yarn path.
Air was blown onto the yarn at 20 ° C. under the conditions shown in Table 2 to cool it, and the undrawn yarn was wound at a speed of 1000 m / min.

The glass transition point Tg of this undrawn yarn was 72 ° C. when measured by DSC.

In addition, the yarn temperature of the spun yarn was measured using a non-contact infrared yarn thermometer, and the distance from the spinneret surface where the yarn temperature reached a temperature of Tg or less was measured and shown in Table 2.

The above undrawn yarn was drawn by a multistage drawing machine according to Example 1 at a drawing temperature of 95 ° C., a heat setting temperature of 135 ° C. and a total draw ratio of 4.0 times to obtain a drawn monofilament having a fineness of 15 denier.

This stretched monofilament was rubbed with a 250 mesh screen gauze woven reed as in Example 1 to observe the amount of white powder scum generated in the reed and the amount of fiber scraps in the white powder scum.
The results are shown in Table 2.

From Table 2, in the experimental levels 9 and 10 of the product of the present invention, the Tg reaching point is within 2 m below the spinneret, and the Worcester yarn unevenness is less than 1%. Therefore, the amount of white powder scum generated is small, and the amount of fiber waste in the white powder scum is extremely small. On the other hand, in the experimental levels 11 and 12 of the comparative product, the cooling condition of the chimney was weak and Tg
The arrival point exceeds 2 m below the spinneret, and Worcester yarn unevenness exceeds 1%, and although the density is less than 1.370, the amount of white powder scum is large and the amount of fiber waste in the white powder scum is large.

〔The invention's effect〕

The high-mesh screen gauze polyester monofilament of the present invention has an undrawn yarn within 2 m below the spinneret when producing a polyester monofilament having a relatively large fineness due to melt spinning and easily causing Worcester yarn unevenness due to uneven cooling. Glass transition point of polyester at position
Cooling to a temperature below Tg, then using a heating roller combined in multiple stages, stretching temperature 90 ~ 120 ℃, heat setting temperature 90 ~ 140
By multi-stage drawing at ℃, the Wooster yarn unevenness is reduced and the uniformity is excellent, and by setting the density of the fiber within the specified range, weaving properties are excellent and the occurrence of white powder scum during weaving is suppressed. Since the yarn breakage can be reduced, it is possible to manufacture a high-mesh screen gauze excellent in tear strength of 250 mesh or more.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-61-282424 (JP, A) JP-A-59-207289 (JP, A) "Screen Printing Handbook" edited by the Japan Screen Printing Technology Association Editorial Committee, Japan Published by Screen Printing Technology Association (September 20, 1974, second edition) 25 <Volume 1> Characteristics of screen material

Claims (1)

(57) [Claims] 1. A heating roller in which polyester is melt-spun to obtain an unstretched yarn, the unstretched yarn is cooled to a temperature not higher than the glass transition point Tg of polyester within 2 m below the spinneret, and then combined in multiple stages. Depending on the stretching temperature 90 ~ 120 ℃,
The fineness obtained by multi-stage drawing at a heat setting temperature of 90 to 140 ° C is 6
~ 15 denier, breaking strength 5.5 ~ 8.0g / D, density 1.3580
Polyester monofilament for weaving of high mesh screen gauze characterized by having a Wooster yarn unevenness of 0.3 to 1.0 at 1.3700 g / cm ³ .