JP3486132B2 - Modified polyethylene naphthalate monofilament and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a modified polyethylene naphthalate monofilament having a fineness, which is useful as a screen gauze, particularly as a high mesh screen gauze. More specifically, the modified polyethylene naphthalate monofilament, which has high tensile strength, high torsional elastic modulus, excellent abrasion resistance due to the reeds during weaving, and excellent compatibility with the photosensitive resin, and high-speed spinning method can be produced with high productivity. On how to do.

[0002]

2. Description of the Related Art Screen gauze fabrics are used in the field of printing electronic circuits and the like, but there is an increasing demand for improvement in printing accuracy. Therefore, a high strength and highly elastic screen gauze is required. In addition, since a high mesh is required, the monofilament forming the screen gauze must also have high strength, high elasticity and fineness.

Conventionally, such high-strength, high-modulus monofilaments include stainless steel, nylon, polyethylene terephthalate (PET) and the like. Among them, the monofilament made of PET is most often used because of its strength, elastic modulus, dimensional stability, price and the like.
However, such a PET monofilament is not satisfactory either, and as a material having higher strength and elasticity, which does not change with time, and has a strong wear property, for example, Japanese Patent Laid-Open No.
As disclosed in Japanese Patent Publication No. 45741-, polyethylene naphthalate monofilaments are used.

However, in the above prior art method, 1
Although it is possible to obtain a monofilament having a fineness of about 2 denier, the strength is somewhat insufficient and is not satisfactory, and a process for drawing the once-wound product at a spinning speed of 1000 m / min or less is obtained. , Production efficiency is very poor. Further, in this publication, the polyethylene naphthalate homopolymer is applied, and there is a drawback that the compatibility with the photosensitive resin is poor.

Japanese Unexamined Patent Publication (Kokai) No. 2-104723 proposes to copolymerize polyester with a glycol component having a molecular weight of 300 to 6000 to improve the compatibility with a photosensitive resin. However, in this publication, polyethylene terephthalate is the main component, and the strength is low and problems such as yarn breakage during weaving occur.

On the other hand, Japanese Patent Laid-Open No. 4-100914 proposes that the knot strength of polyethylene naphthalate monofilament for screen gauze must be 3.5 g / denier or more in order to suppress scum generation in the weaving process. ing. However, the monofilament disclosed in the publication is applied to a monofilament having a denier of more than 5 denier, and a monofilament having an ultrafineness of 5 denier or less is caused by reed abrasion even if the knot strength is 3.5 g / denier or more. It was not possible to prevent the occurrence of scum. Further, in this publication, a technique in which a material wound at a spinning speed of 1500 m / min is stretched in multiple stages, and since two steps are performed, the production efficiency is poor.

To increase productivity, Japanese Patent Laid-Open No. 5-2956
According to the publication No. 17, in the step of producing a polyester monofilament, the spinning speed is 300 by the direct spinning drawing method.
It is disclosed that spinning is performed at 0 m / min or more. However, the monofilament of the polyester monofilament in the publication is 12 denier, which is not applicable to high mesh screen gauze. Further, the spinning take-up speed is at most 5000 m / min, and improvement in productivity cannot be expected.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a monofilament having an ultrafineness suitable for high mesh screen gauze applications, which does not have the above-mentioned defects, by high-speed spinning with high production efficiency.

[0009]

Means for Solving the Problems In the present invention, as a result of extensive studies on such problems, a polyethylene naphthalate polymer copolymerized with a polyethylene glycol component in an amount of less than 10% by weight was used, and a monofilament having a fineness of 5 denier or less was specified. It was found that by spinning under the conditions of 1), a monofilament having high strength, high torsional elastic modulus, excellent abrasion resistance due to a reed, and excellent adhesiveness with a photosensitive resin can be obtained.

That is, according to the present invention, the fineness is 5 denier or less, the strength is 6.0 g / denier or more and the twist is made of a modified polyethylene naphthalate obtained by copolymerizing a polyethylene glycol component in an amount of less than 10% by weight. A modified polyethylene naphthalate monofilament having an elastic modulus G of 40 kg / cm ² or more and excellent compatibility with a photosensitive resin is provided.

According to the present invention, when a modified polyethylene naphthalate monofilament having a fineness of 5 denier or less is wound at a spinning speed of 6000 m / min or more, an oil agent is applied 1 m or more below the spinneret surface, and Provided is a method for producing a modified polyethylene naphthalate monofilament, wherein the surface roughness of the first goded roller is 3S to 8S and the roughness of the second goded roller is 6S to 12S.

Furthermore, the screen gauze of the present invention is characterized by using the modified polyethylene naphthalate monofilament obtained by the above-mentioned manufacturing method and having the above-mentioned characteristics.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.
The polyethylene naphthalate polymer used in the present invention is mainly composed of polyethylene-2,6-naphthalate and is obtained by copolymerizing less than 10% by weight of polyethylene glycol.

The molecular weight of polyethylene glycol is not particularly limited, but it is preferably 300 to 1000. When the molecular weight is 300 or more, since the boiling point is high, the scattering of glycol to the outside of the reaction system is suppressed, and the yield during polymer polymerization is excellent. Further, when the molecular weight is 1000 or less, compatibility with the photosensitive resin is excellent, which is preferable.

On the other hand, the copolymerization rate of polyethylene glycol must be less than 10% by weight. When it is 10% by weight or more, the strength of the polyethylene naphthalate monofilament is less than 6.0 g / denier, and a screen gauze having the desired performance cannot be obtained. It is preferably 4 to 8% by weight. When the copolymerization rate is in this range, the strength of the monofilament is sufficient and the compatibility with the photosensitive resin is excellent, which is preferable.

Further, the polyethylene naphthalate includes
A small amount of stabilizers, matting agents, coloring agents, ultraviolet absorbers, etc. may be added.

The intrinsic viscosity [η] of the polyethylene naphthalate after melt extrusion is preferably in the range of 0.4 to 0.6. When the intrinsic viscosity is within this range, the spinnability is excellent and the strength of the obtained filament is sufficient, which is preferable.

The monofilament should have a fineness of 5 denier or less and a strength of 6.0 g / d or more.
If the fineness exceeds 5 denier, the required ultra-high mesh screen gauze cannot be obtained. Conventionally, high-mesh screen gauze has been provided using high-strength monofilaments having a denier of about 12 to 28 denier, but high-strength monofilaments of 5 denier or less are required to perform printing with higher precision. Also,
In the case of a monofilament having a denier of 5 denier or less, the strength of the monofilament as a whole becomes weak because of the fineness, and therefore the strength of the monofilament needs to be 6.0 g / d or more. 6.0 g /
If it is less than d, the strength of the screen gauze is insufficient during weaving or gauze, and thread breakage occurs.

Next, the torsional elastic modulus, which is the most characteristic feature of the present invention, will be described with reference to the drawings. (Figure 1) is
It is a principle view of a torsion measuring machine (KES-YN1 manufactured by Kato Tech) used when measuring the torsional elastic modulus. Sample 1
Is set on the upper chuck 2 and the lower chuck 3, a constant load 4 is applied to the lower chuck, and the lower chuck is fixed to a horizontal rod 5. The rod is fitted in a groove provided in the rotating ring 6 and twisted to the sample. Drive it. The rotation speed of the rotating ring 6 is constant, and the forward and reverse reversal is possible. Further, the torque generated by applying the torsional drive to the monofilament is detected by the detector 7 connected to the upper chuck 1. Torque-torsion angle obtained by this device
One embodiment of the curve of FIG. The torsional elastic modulus is a value defined by the following equation (Equation 1) from the initial slope of the curve.

(Equation 1) G = (32 × T _f × l) / (π × d ⁴ × θ) G: Torsional elastic modulus (kg / cm ² ) T _f : Torsional torque (kg · cm) l: Sample Length (cm) π: Circumferential ratio θ: Torsional angle (rad)

According to the studies made by the present inventors, when the torsional elastic modulus of the monofilament is 40 kg / cm ² or more, the screen gauze is not worn due to the reed during weaving, and is excellent in durability. Can be obtained, 40kg /
If it is less than cm ² , even if the strength is high, the abrasion property due to the reed becomes poor. That is, since the torsional elastic modulus is the shearing elastic modulus of the skin of the monofilament, the higher the torsional elastic modulus, the stronger the abrasion of the skin due to external factors such as reeds.

The torsional elastic modulus has a correlation with the crystal morphology of the fiber. Although the tensile strength and tensile elastic modulus of the fiber increase as the crystals inside the fiber are oriented in the fiber axial direction, the strength and elastic modulus in the direction perpendicular to the fiber axis. Further, the torsional elastic modulus decreases. That is, it has been clarified by the present inventors that the torsional elastic modulus is increased when a crystal having a structure slightly tilted with respect to the fiber axis is taken.

It is known that polyethylene naphthalate fibers take two types of crystal forms depending on the spinning method. A fiber obtained by a two-step drawing method of spinning, winding, and drawing at a normal low spinning speed or a direct spinning drawing method of spinning, drawing, and winding at a low spinning speed has molecular chains arranged in the fiber axis direction. It takes the α type structure. On the other hand, 3000m /
A fiber spun at a high speed of not less than a minute and wound up without a drawing step has a β-type structure in which the molecular chain is slightly inclined with respect to the fiber axis. That is, it has been clarified that the high-speed spinning method is optimal for obtaining the modified polyethylene naphthalate monofilament having a high torsional elastic modulus.

The modified polyethylene naphthalate monofilament of the present invention having the above characteristics can be manufactured by the following method. That is, a modified polyethylene naphthalate polymer was obtained by adding 4% by weight of polyethylene glycol having a molecular weight of 600 to an oligomer obtained by transesterification of methyl 2,6-naphthalenedicarboxylate and ethylene glycol by a conventional method. The polymer is melted, extruded from a die, and the extruded monofilament having an intrinsic viscosity [η] of 0.4 to 0.6 is wound through two pairs of goded rollers having a peripheral speed of 6000 m / min or more.

Here, it is important that the spinning speed is 6000 m / min or more. It is necessary to spin at preferably 6000 m / min or more and 7500 m / min or less. 60
If it is less than 00 m / min, the crystallinity is low and a yarn having satisfactory strength cannot be obtained, and the production efficiency is not good. 60
When it is from 00 m / min to 7500 m / min, the production efficiency is excellent and the monofilament does not have a skin-core structure, which is preferable.

Further, when cooling the extruded monofilament from one side, it is preferable that the cooling air is blown at a speed of 0.3 m / sec or less. By using cooling air of 0.3 m / sec or less, nonuniform cooling on the side closer to the cooling air outlet and on the side farther away from the cooling air outlet is eliminated, and the resulting monofilament is free from actual crimping, which is preferable.

Here, if the monofilament has an actual crimp, uniform tension cannot be applied in the step of stretching the screen gauze to cause spots, and further problems such as yarn breakage occur, which is not preferable.

It is necessary to apply the oil agent to the cooled monofilament at a distance of 1 m or more below the die surface. In the region less than 1 m from the surface of the die, the temperature of the monofilament is equal to or higher than the glass transition point. Therefore, when the oil agent is applied in this region, non-uniform cooling occurs, and the crimps that are apparent are generated in the obtained monofilament.

The monofilament to which the oil agent is applied is the first
It is picked up by a goded roller. Here, the surface roughness of the first goded roller needs to be 3S to 8S. If it is less than 3S, the nipability of the monofilament to the roller surface is good, but the yarn separation is poor and it causes yarn breakage. If it is more than 8S, the monofilament has a poor nip property and the yarn bounces, resulting in remarkable operability. descend.

The monofilament passing through the first goded roller is guided to the second goded roller. The surface roughness of the second goded roller needs to be 6S to 12S.
If it is less than 6S, the nip property is good, but the yarn separation is bad, so that it is necessary to increase the speed of the winding machine, and the winding tension increases, and winding tightening and bulge deterioration of the winding shape occurs. If it exceeds 12S, the yarn will bounce on the surface of the roller, resulting in poor operability.

[0031]

EFFECTS OF THE INVENTION According to the present invention, a monofilament of ultrafineness having high strength and excellent compatibility with a photosensitive resin, which is suitable for an ultrahigh mesh screen gauze, is stable without yarn sway or yarn breakage. Operability allows efficient manufacturing.

[0032]

The present invention will be described in more detail with reference to the following examples. The characteristic values in the following examples are measured by the following methods.

(1) Intrinsic Viscosity [η] After Melt Extrusion The extruded yarn intrinsic viscosity [η] is a polyethylene naphthalate polymer melted by a conventional method and extruded from a die,
It was measured by a Ubbelohde method at 20 ° C. in a mixed solvent of phenol / tetrachloroethane = 6/4 (weight ratio).

(2) Strength, Elongation and Elastic Modulus Using an autograph (AGS-1kNG) manufactured by Shimadzu Corporation, a fiber having an initial sample length of 200 mm was subjected to an initial load of 1/30 of the fineness and pulled at a speed of 200 mm / min. A test was conducted to determine the breaking strength and the breaking elongation. Further, the elastic modulus was obtained from the initial slope of the strength / elongation curve.

(3) Birefringence The birefringence of the monofilament was measured by the Berek compensator method using α-bromonaphthalene as an immersion liquid and a polarizing microscope BH2 manufactured by Olympus.

(4) Knot strength It was measured according to JIS L-1013.

(5) Torsional elastic modulus KES-YN1 manufactured by Kato Tech was used and measured by the above-mentioned method.

(6) Number of reed abrasion breakages (FIG. 3 ) is a schematic view of an apparatus used for measuring the number of reed abrasion breakages. Constant load 9 on the measurement monofilament 8
(0.2 g / denier) is laid and threading is performed on the 300 reeds / inch reed 10. The monofilament 8 is installed straight in the vertical direction and fixed between the upper comb teeth 11 and the lower comb teeth 12. Next, in the upper comb tooth 11, the monofilament 8 is placed by being shifted to the right by four teeth (4.5 mm) from the vertical direction. The reed 10 is vertically moved at a speed of 140 rotations / minute in a width of 10 cm by driving a motor, and forcibly rubs the monofilament 8 inclined with respect to the reed teeth. The number of times until the monofilament is cut by friction is measured by a counter, and the measurement is finished at the time of cutting.

(7) β-type / α-type crystal intensity ratio wide-angle X-ray diffractometer RINT-2500 (manufactured by Rigaku Denki)
Using, the aluminum holder around which the fibers aligned in the fiber axis direction are wound is set on the fiber sample stand. The thickness of the sample was set to 0.5 mm, the sample was irradiated with X-rays at an output of 60 kV and 200 mA, and the intensity of the sample in the equatorial direction was measured. The intensity distribution curve in the equatorial direction was separated into peaks based on crystals and amorphous, and the integrated intensity of the peak at the Bragg angle 2θ = 18.7 ° (β type crystal) and 2θ = 15.6 ° (α type crystal). The ratio of integrated intensities was calculated based on.

(8) Compatibility evaluation of photosensitive resin Using the polyethylene naphthalate monofilament,
A 500 mesh screen gauze was woven. A photosensitive resin is applied to this with a coating thickness of 20 μm, a potch-shaped pattern is placed, and then exposed by a mercury lamp to a diameter of 0.1 mm
A 1.0 mm potch-shaped pattern was exposed on the screen cloth. After that, a mending tape was attached to the surface coated with the potch, and the tape was peeled off after rubbing 10 times, and the compatibility of the photosensitive resin was determined by the number of the potches peeled off on the tape surface.
Evaluation was made in three levels of Δ and ×.

Examples 1 and 2, Comparative Examples 1 to 5 4% by weight of polyethylene glycol having a molecular weight of 600 was added to the oligomer obtained by transesterification of methyl 2,6-naphthalenedicarboxylate and ethylene glycol by a conventional method. A modified polyethylene naphthalate polymer was obtained by polycondensation. This intrinsic viscosity [η] is 0.
57 modified polyethylene naphthalate polymer was melt extruded and extruded at a discharge rate of 3.6 g / min for each hole using a die having a hole number of 2 holes and a hole diameter of 0.65 mm.
The oil agent was applied over a length of 1 m by cooling with cooling air at 35 ° C. at a speed described in (Table 1). After that, it is taken up by a goded roller 1 having a surface roughness described in (Table 1) at a spinning speed of 7000 m / min, and is separated by a goded roller 2 having a surface roughness described in (Table 1) and wound into a winder. It was wound up at. The spinning condition and the actual crimped state of the wound modified polyethylene naphthalate monofilament are shown in (Table 1).

Under the conditions of Examples 1 and 2, the spinning was very smooth, and in the wound modified polyethylene naphthalate monofilament, no apparent crimp due to uneven cooling in the cross-sectional direction of the monofilament was observed and the yarn quality was improved. There were no problems such as spots or fineness spots.

On the other hand, under the conditions of Comparative Example 1, the surface roughness of the goded roller 1 and the goded roller 2 was within the range of the present invention, and the spinnability was good, but the application position of the oil agent was within the range of the present invention. The modified polyethylene naphthalate monofilament wound up due to the occurrence of cooling spots in the cross section of the monofilament because it was dislocated was found to have actual crimps, and yarn irregularities and fineness spots were observed.

In Comparative Examples 2 and 3, the surface roughness of the goded roller 1 is outside the range of the present invention, and in Comparative Examples 4 and 5, the surface roughness of the goded roller 2 is outside the range of the present invention. Is too coarse, the monofilaments bounce on the roller surface to cause yarn breakage. In Comparative Examples 3 and 5, the nip property was too good, and the monofilament was wound up on the rollers to cause yarn breakage.

[0045]

[Table 1]

Examples 3 to 6 Polyethylene glycol having a molecular weight of 600 was added to 4% by weight in Examples 3 to 4 to an oligomer obtained by transesterification of methyl 2,6-naphthalenedicarboxylate and ethylene glycol by a conventional method. By polycondensation, the modified polyethylene naphthalate polymer having an intrinsic viscosity [η] of 0.57, and in Examples 5 to 6 was added 8 wt% to obtain a modified polyethylene naphthalate polymer having an intrinsic viscosity [η] of 0.55. The modified polyethylene naphthalate polymer was melted at each temperature so as to have the intrinsic viscosity [η] of the discharged yarn described in (Table 2), and the number of holes was 2
The discharge amount of each hole is 3.6g / min from the hole diameter of 0.65mm, and over the length of 1.8m, 35
The oil was applied by cooling with cooling air having a temperature of 0.2 m / sec. Then, it was taken up by a goded roller 1 having a surface roughness of 4S at a spinning speed described in (Table 2), and was separated by a goded roller 2 having a surface roughness of 8S and wound by a winder. .

The physical properties of the obtained modified polyethylene naphthalate monofilament and the number of times of repulsive abrasion breakage are shown (Table 2).
It was shown to. In each of Examples 3 to 6, the strength was 6.0 g /
It was a good monofilament having a denier or more and a torsional elastic modulus of more than 40 kg / cm ^{2. The} number of breaks due to reed abrasion was high, and it did not break even after 30,000 times. Further, when a screen gauze was woven from the monofilament and the compatibility with the photosensitive resin was examined, all were excellent.

[0048]

[Table 2]

Comparative Example 6 In Comparative Example 6, the polyethylene glycol copolymerization rate is within the range of the present invention, but the spinning speed is as slow as 5500 m / min, which is outside the range of the present invention, and the strength and the torsional elastic modulus are low, so that reed abrasion is caused. The characteristics were poor and the monofilament broke at 9,500 times.
In addition, when a 500 mesh screen gauze was woven using the monofilament of Comparative Example 6, yarn breakage occurred frequently in the weaving stage.

Comparative Example 7 Polyethylene naphthalate homopolymer having an intrinsic viscosity [η] of 0.56 was obtained by polycondensation of methyl 2,6-naphthalenedicarboxylate and ethylene glycol by a conventional method. This polyethylene naphthalate homopolymer was melted so as to have the intrinsic viscosity [η] of the discharged yarn described in (Table 3), and the discharge amount of each hole was 3.6 g / min from the number of holes of 2 holes and the hole diameter of 0.65 mm. Extrusion, over a length of 1.8 m,
The oil was applied by cooling with cooling air at 35 ° C. and a wind speed of 0.2 m / sec. Then, a goded roller 1 with a surface roughness of 4S
At a spinning speed of 6000 m / min, the fiber was separated by a goded roller 2 having a surface roughness of 8S and wound by a winder.

The physical properties of the obtained polyethylene naphthalate monofilament and the number of times of repulsive abrasion breakage are shown in (Table 3). The monofilament had a strength of 6.0 g / denier or more and a torsional elastic modulus of more than 40 kg / cm ² . However, when the screen gauze was woven from the monofilament and the compatibility with the photosensitive resin was examined, a large amount of peeling of the photosensitive resin was observed, and the compatibility was poor.

Comparative Example 8 An oligomer obtained by subjecting methyl 2,6-naphthalenedicarboxylate and ethylene glycol to an ester exchange reaction by a conventional method was added with 10% by weight of polyethylene glycol having a molecular weight of 600 and an intrinsic viscosity [η ] Is 0.
61 modified polyethylene naphthalate polymer was obtained.
Melt this modified polyethylene naphthalate polymer,
The number of holes is 2 holes, the discharge amount of each hole is extruded from the hole diameter of 0.65 mm at 3.6 g / min, and it is cooled with a cooling air of 35 ° C. and a wind speed of 0.2 m / sec over a length of 1.8 m. An oil agent was applied. Then, it was taken up by a goded roller 1 having a surface roughness of 4S at a spinning speed of 6000 m / min, separated through a goded roller 2 having a surface roughness of 8S, and wound by a winder.

The physical properties of the obtained modified polyethylene naphthalate monofilament and the number of times of repulsion abrasion breakage are shown (Table 3).
It was shown to. The monofilament had a strength of less than 6.0 g / denier and had a problem that the number of breaks due to reed abrasion was low and yarn breakage occurred immediately. When a screen gauze was woven using the monofilament, thread breakage occurred immediately.

Comparative Example 9 The modified polyethylene naphthalate polymer of Example 3 was
The undrawn monofilament was once wound up under the conditions described in Table 3 below. After that, a stretching treatment was performed to obtain a modified polyethylene naphthalate monofilament.

The monofilament had a high strength and a high knot strength, but the torsional elastic modulus was lower than the range of the present invention, and the reed abrasion property was very poor. This is because α-type crystals were preferentially formed by the low spinning speed and the two-step stretching. Also, when the screen gauze was woven, yarn breakage frequently occurred at the weaving stage.

[0056]

[Table 3]

[Brief description of drawings]

FIG. 1 is a drawing showing the principle of a torsion measuring machine used for measuring the torsional elastic modulus of a modified polyethylene naphthalate monofilament of the present invention.

FIG. 2 is a drawing showing a typical example of torque-torsion angle obtained by twist measurement of a modified polyethylene naphthalate monofilament of the present invention.

FIG. 3 is a diagram showing an outline of a reed abrasion tester used to measure the number of reed abrasion breakages of the modified polyethylene naphthalate monofilament of the present invention.

[Explanation of symbols]

1 sample 2 Upper chuck 3 Lower chuck 4 Weight for load 5 horizontal bars 6 rotating ring 7 Torque detector 8 monofilaments 9 Weight for load 10 reed 11 upper comb teeth 12 Lower comb teeth

Front page continued (72) Hideo Ueda, 4-1, Kanebocho, Hofu-shi, Yamaguchi Prefecture, Kanebo Synthetic Co., Ltd. (72) Shikiki Honda, 4-1-1, Kanebocho, Hofu-shi, Yamaguchi, Kanebo Synthetic Co., Ltd. (56 ) References JP-A-4-100914 (JP, A) JP-A-4-153312 (JP, A) JP-A-11-279833 (JP, A) JP-A-5-163612 (JP, A) JP-B 44-20471 (JP, B1) (58) Fields surveyed (Int.Cl. ⁷ , DB name) D01F 6/62 D01F 6/84 D01F 6/86 B41N 1/24

Claims (3)

(57) [Claims] 1. A modified polyethylene naphthalate obtained by copolymerizing a polyethylene glycol component in an amount of less than 10% by weight, having a fineness of 5 denier or less and a strength of 6.0 to 6.0.
6.7 g / denier and a torsional elastic modulus G of 40 to
Modified polyethylene naphthalate monofilament having a weight of 48.78 kg / cm 2 . 2. A polyethylene glycol component of 10% by weight
% Of the modified polyethylene naphthalate monofilament copolymerized with less than 1% of the spinneret at a spinning speed of 6000 m / min or more, an oil agent is applied 1 m or more below the spinneret surface, and the surface roughness of the first goded roller is 3S. ~ 8S,
A method for producing a modified polyethylene naphthalate monofilament, characterized in that the roughness of the second goded roller is 6S to 12S. 3. A screen gauze comprising the modified polyethylene naphthalate monofilament according to claim 1.