JP5862076B2 - Polyester monofilament for screens - Google Patents

Description

  The present invention relates to a polyester monofilament suitable for a high mesh fabric for use as a screen wrinkle. More specifically, the present invention relates to a polyester monofilament for a screen bag suitable for a field requiring high precision and strength such as electronic printing.

  Conventionally, mesh fabrics made of natural fibers and inorganic fibers have been widely used as fabrics for screen printing, but in recent years, synthetic fabric mesh fabrics that are excellent in flexibility, durability, and cost performance, especially polyester fibers. A mesh fabric is widely used.

  In recent years, as electronic devices have become highly functional and compact, board circuits have become more precise and compact, and the screen has a high-strength, high-mesh fabric and high printing accuracy. It has been demanded. In order to satisfy these required characteristics, the monofilament that is a component of the screen wrinkle has a finer fineness, higher strength and higher modulus, and further requires a monofilament that is highly uniform and does not cause printing defects. Has been.

  Further, when weaving a high mesh fabric using such a monofilament, the monofilament has a high strength, and therefore, the yarn (monofilament) and the yarn (monofilament) and the weaving apparatus are repeatedly abraded, and the yarn The face layer is shaved into a fibril or powder. The occurrence of such fibrillar and powder-like scraping (scum) causes printing defects in the screen ridge, and the productivity of the screen ridge is significantly reduced. Therefore, it is possible to suppress abrasion and improve wear resistance. is important. It is known that shaving is likely to occur when the fiber surface layer has a low degree of crystallinity and the amorphous fiber has a high fiber orientation. In addition, shaving is more likely to occur as the fiber structure becomes uneven. If there are portions where the crystallinity or fiber orientation is not uniform in the longitudinal direction or cross-sectional direction of the yarn (monofilament), stress is concentrated during weaving. Scraping with the site as a nucleus occurs. For this reason, the control of the fiber structure in the fiber surface layer and the improvement of the fiber cross section perpendicular to the fiber axis and the uniformity in the longitudinal direction are important in order to suppress scraping.

  In order to solve such problems, the orientation difference in the fiber cross-sectional direction was reduced by appropriately reducing the fiber orientation in the amorphous part of the surface layer of the single component yarn, and the uniformity in the cross-sectional direction of the fiber structure was improved. The proposal regarding the polyester monofilament is made (refer patent document 1). In this monofilament, since the surface fiber structure is “broken” by the fine melting of the surface polyester by the vapor drawing nozzle, the crystal part is destroyed, and the amorphous part that causes scraping increases, and the fiber structure in the longitudinal direction Due to the large variation, a sufficient wear resistance effect cannot be obtained. In addition, since the monofilament is produced by a two-step method, uneven orientation over time occurs before stretching is started, and the fiber structure and yarn physical properties are uniform compared to the monofilament produced by the one-step method. Inferiority.

  Separately, the core-sheath type composite monofilament is subjected to multi-stage drawing at a spinning speed of 500 to 1000 mpm, a draw ratio of 2 to 7 times, and a single stage ratio of 60 to 95% by a one-step method or a two-step method. There is a proposal that a monofilament having a low fiber orientation in the portion and a crystallinity of the surface layer of 30% or more can be obtained (see Patent Document 2). In the case of this monofilament, it is possible to improve the wear resistance by increasing the crystallinity of the fiber surface layer and suppressing the orientation of the amorphous part in this way, but the fiber orientation of the fiber surface layer is improved. Since it is low, powdery scum is generated and printing defects occur. In addition, a heat insulating cylinder is not used for the production of this monofilament, resulting in uneven fiber structure over time and variations in physical properties, resulting in poor uniformity.

  In addition, the chimney cooling air speed is set depending on the fineness, and after cooling by multistage slow cooling, a monofilament with high fiber diameter uniformity is obtained by multistage drawing through a heat retaining cylinder in a one-step method. There is a proposal that it is possible (see Patent Document 3). In this proposal, in addition to the control of the chimney cooling conditions, a method of actively keeping the temperature at 290 ± 10 ° C. by using a heat insulating cylinder is incorporated, and it is possible to obtain highly uniform yarns. . However, just controlling the atmospheric temperature of 290 ± 10 ° C. is not sufficient for suppressing the orientation of the entire polymer including the central portion of the polymer to be ejected, and a partially relaxed and oriented portion is produced. Structural unevenness will occur. It is also important to reduce not only the ambient temperature at a certain moment but also the temporal change of the ambient temperature to eliminate the structural unevenness in the longitudinal direction, and this point is insufficient in the proposal of Patent Document 3. Furthermore, there is no discussion about the materials of the first and second hot rollers that have a great influence on the stretchability, and it is difficult to say that sufficient unevenness of the fiber structure is provided due to uneven stretching. Is still insufficient.

Japanese Patent Laying-Open No. 2005-194669 (Claims) JP 2004-232182 A (Claims) JP 2009-84712 A (Claims)

  Therefore, the object of the present invention is to make the fiber structure uniform and appropriate in a high-strength single-component monofilament that is easy to cut compared to the core-sheath monofilament, by making the crystal structure uniform and reducing the amorphous portion of the fiber surface layer and suppressing the orientation. It is an object of the present invention to provide a polyester monofilament for screen wrinkles that suppresses scraping defects that occur when obtaining a screen wrinkle that maintains high strength and high modulus and has improved printing durability and dimensional stability.

  The present invention is intended to achieve the above object, and the polyester monofilament for screen wrinkles of the present invention is a single component polyester monofilament mainly composed of polyethylene terephthalate, and is based on the fiber axis of the polyester monofilament. A polyester monofilament for screen wrinkles characterized in that the difference between the crystallinity at the center of the fiber and the crystallinity at a position of 1 μm from the fiber surface toward the center is 4% or less in any vertical fiber cross section .

  According to a preferable aspect of the monofilament for screen wrinkles of the present invention, in an arbitrary fiber cross section perpendicular to the fiber axis, the crystallinity at a position of 1 μm from the fiber surface toward the center and the position (the position of 1 μm) ) To a crystallinity at a position in the center direction of 2 μm is 2% or less.

  According to a preferred embodiment of the monofilament for a screen wrinkle of the present invention, the standard deviation when the crystallinity is measured arbitrarily at least 5 points from the fiber surface to the fiber center in any fiber cross section perpendicular to the fiber axis. Is 2 or less.

  According to the present invention, in a high-strength single-component monofilament that is easier to cut than a core-sheath monofilament, the fiber structure is made uniform and optimized to maintain high strength and high modulus, printing durability and dimensional stability. Thus, a polyester monofilament for screen wrinkles that can suppress the shaving defect when obtaining a screen wrinkle with improved sash is obtained. As a result, the printing accuracy can be improved, the yarn passing property in high-order processing can be improved, and the opening unevenness and the fluctuation in tension during aging can be suppressed.

FIG. 1 is a schematic perspective view for explaining a sampling method for measuring the crystallinity and birefringence of the polyester monofilament for screen wrinkles of the present invention. FIG. 2 is a schematic side view for explaining a process (one-step method) when producing a polyester monofilament for a screen wrinkle according to the present invention.

  Hereinafter, the polyester monofilament for screen wrinkles of the present invention will be described in detail.

The polyester monofilament for screen wrinkles of the present invention is a single-component polyester monofilament mainly composed of polyethylene terephthalate, and in any fiber cross section perpendicular to the fiber axis of the polyester monofilament, the fiber center crystallinity and fiber The difference from the crystallinity at the position of 1 μm from the surface to the center is 4% or less, and the standard deviation when the crystallinity is measured arbitrarily at least 5 points from the fiber surface to the fiber center is 2 or less. It is 5.0 cN / dtex or more and 7.0 cN / dtex or less, 5% modulus 2.4 cN / dtex or more and 4.0 cN / dtex or less .

  The presence or absence of scraping during weaving of the monofilament has a deep relationship with the fiber structure, particularly the fiber orientation in the amorphous portion of the fiber surface layer. The fiber surface layer here refers to a layer from an arbitrary fiber cross section perpendicular to the fiber axis to a position of 3 μm from the fiber surface toward the fiber center, and is generally an amorphous part of the fiber surface layer. When the fiber orientation in is high, it is known that fibrillation is likely to occur starting from the highly oriented portion, and therefore it is important to suppress the fiber orientation in the amorphous part of the fiber surface layer. Further, by promoting the formation of the crystal structure in the fiber surface layer and increasing the proportion of the crystal portion, the amorphous portion itself that causes scraping can be reduced, which leads to improved wear resistance.

  Usually, in the case of a single component monofilament, the amorphous portion of the fiber surface layer becomes highly oriented over time, such as when a two-step method is used. Therefore, the fiber orientation (birefringence) in the amorphous portion of the fiber surface layer Becomes higher than the inner layer. On the other hand, the proportion of the crystal structure in the fiber surface layer decreases, and the proportion of the amorphous portion increases (the crystallinity of the fiber surface layer decreases). Also, fibrillation is generated in the fiber surface layer by rubbing between the yarn (monofilament) and the weaving apparatus. Therefore, the proportion of the crystal structure in the fiber surface layer (crystallinity) is high and the fiber orientation of the amorphous part is low, that is, the crystallinity and amorphous orientation of the fiber surface layer are at the same level as the inner layer. It is important to obtain a monofilament having a uniform fiber structure in the cross-sectional direction of the fiber.

  The present invention is limited to single component polyester monofilaments comprising polyethylene terephthalate as the main constituent.

  As another technique for preventing fibrillation in the fiber surface layer, a technique called core sheathing in which a low-viscosity polymer is blended with a sheath component is known. However, this method has a problem that the sheath component polymer having low orientation is detached as a powdered scum together with the oil agent. Moreover, in order to form a core-sheath type structure, it is necessary to complicate equipment, a pack, a nozzle | cap | die, etc., Therefore A cost will also become high compared with a single component yarn. From these viewpoints, the present invention aims only at improving the wear resistance of the single component polyester monofilament.

  In the above situation, as a result of intensive studies by the present inventors, the inventors have invented a single component polyester monofilament having a highly uniform fiber structure, particularly a crystal structure, in the fiber cross-sectional direction perpendicular to the fiber axis.

  The polyester monofilament for screen wrinkles of the present invention is formed of polyethylene terephthalate having terephthalic acid as the main acid component and ethylene glycol as the main glycol component, and 90 mol% or more of ethylene terephthalate repeating units. However, it may contain a copolymer component capable of forming another ester bond at a ratio of less than 10 mol%.

  Examples of such copolymer components include, as acidic components, bifunctional aromatic carboxylic acids such as isophthalic acid, phthalic acid, dibromoterephthalic acid, naphthalene dicarboxylic acid, and octethoxybenzoic acid, sebacic acid, oxalic acid, Bifunctional aliphatic carboxylic acids such as adipic acid and dimer acid, and dicarboxylic acids such as cyclohexanedicarboxylic acid.

  Examples of the glycol component include ethylene glycol, diethylene glycol, propanediol, butanediol, neopentyl glycol, bisphenol A, and polyoxyalkylene glycols such as cyclohexanedimethanol, polyethylene glycol, and polypropylene glycol. However, it is not limited to these.

  In addition, titanium dioxide as a matting agent, silica and alumina fine particles as a lubricant, hindered phenol derivatives as an antioxidant, and further flame retardants, antistatic agents, ultraviolet absorbers, and coloring pigments, if necessary, into polyethylene terephthalate. Can be added.

  FIG. 1 is a schematic perspective view for explaining a sampling method for measuring the crystallinity and birefringence of the polyester monofilament for screen wrinkles of the present invention.

  As shown in FIG. 1, the polyester monofilament for screen wrinkles of the present invention exists on an arbitrary fiber cross section C perpendicular to the fiber center axis B in the sample section A having a thickness of 1 μm cut out through the fiber axis. The difference between the crystallinity at the fiber center D and the crystallinity at the position E of 1 μm from the fiber surface I toward the center needs to be 4% or less.

  Usually, the monocomponent monofilament has a low crystallinity in the fiber surface layer H and a large difference in crystallinity from the fiber center D (for example, the crystallinity of the fiber center D: about 19%, centered from the fiber surface I) The crystallinity of the position E at 1 μm toward the surface: about 14%). When the difference in crystallinity between the fiber center D and the position E of 1 μm from the fiber surface toward the center exceeds 4%, the ratio of the amorphous portion is large, and scraping occurs in the highly oriented portion. On the other hand, by reducing the difference in crystallinity between the fiber center D and the fiber surface layer H, that is, by increasing the crystallinity of the fiber surface layer H to the same level (about 19%) as the fiber center D. The ratio of the amorphous part of the fiber surface layer H, which is the generation site, can be reduced, and shaving can be suppressed. The difference in crystallinity at the position E of 1 μm from the fiber center D and the fiber surface I toward the center is preferably as small as possible, more preferably 2% or less.

  In the single component monofilament, as described above, the amorphous portion of the fiber surface layer H becomes highly oriented due to normal orientation relaxation, and this portion serves as a starting point to cause fibrillation. Such a highly oriented portion exists in a very shallow portion of the fiber surface, and therefore a fiber structure gradient is generated even in the fiber surface layer H. That is, in an arbitrary fiber cross section C perpendicular to the fiber center axis B, the degree of crystallinity at a position E of 1 μm from the fiber surface I toward the center and a further 2 μm center direction from the position (the position E of 1 μm). The crystallinity at the position F is about 14% and about 17%, respectively, and a crystal structure difference occurs in the fiber surface layer H, thereby inducing fibrillation. Therefore, reducing the gradient of the fiber structure in the fiber surface layer H is important for improving the wear resistance.

  As shown in FIG. 1, the polyester monofilament for screen wrinkles of the present invention has a crystallinity at a position E of 1 μm from the fiber surface I toward the center in an arbitrary fiber cross section C perpendicular to the fiber center axis B. The difference from the crystallinity at the position F in the center direction of 2 μm from the position (position E of 1 μm) is preferably 2% or less, more preferably 1% or less. When the difference between the crystallinity at the position of 1 μm from the fiber surface I toward the center and the crystallinity at the position F in the center direction of 2 μm from the position (position E of 1 μm) exceeds 2%, the fiber surface In the layer H, there is a clear fiber structure gradient, and stress may concentrate on highly oriented sites and cause scraping.

  The uniformity of the fiber structure in the fiber cross-sectional direction is preferably higher not only in the fiber surface layer H but in the entire fiber. Even if the difference in crystal structure between the fiber surface layer H and the fiber center D and the gradient of the crystal structure in the fiber surface layer are small, if there is a large variation in the fiber structure of the entire fiber, local stress concentration is involved. As a result, fibrillation may occur in the portion.

As shown in FIG. 1, the polyester monofilament for screen wrinkles of the present invention has an arbitrary fiber cross section C perpendicular to the fiber center axis B, and at least 5 points or more from the fiber surface I to the fiber center D (for example, The standard deviation when the crystallinity is measured in G) in FIG. 1 is preferably 2 or less, more preferably 1 or less.
When the standard deviation exceeds 2, the above-mentioned local stress concentration may occur and fibrillation may occur. The standard deviation here is an index representing the degree of variation of the statistical values.

  The polyester monofilament for screen wrinkles of the present invention preferably has not only high uniformity in the fiber cross-sectional direction but also high uniformity in the fiber longitudinal direction. As a feature of the present invention, the difference R between the maximum value and the minimum value when the toughness of the breaking point is measured five times in the longitudinal direction is preferably 5 or less, more preferably 3 or less. When the physical property unevenness exists in the longitudinal direction of the fiber such that the difference R between the maximum value and the minimum value exceeds 5, the thread passing property in the high-order processing is deteriorated, causing the opening unevenness and the tension fluctuation during aging. It can be a factor. The toughness of the breaking point is defined as the product of the square root of the breaking elongation and the breaking strength.

As shown in FIG. 1, the polyester monofilament for screen wrinkles of the present invention is centered from birefringence Δn in the amorphous part of the fiber center D and the fiber surface I in an arbitrary fiber cross section C perpendicular to the fiber center axis B. The difference from the birefringence Δn in the amorphous part at the position E of 1 μm is preferably 0 or more and 10 × 10 ⁻³ or less. If the difference between the birefringence Δn at the fiber center D and the birefringence Δn at the position E of 1 μm from the fiber surface I toward the center is larger than 10 × 10 ⁻³ , the amorphous orientation in the fiber surface layer H becomes high, and the fibril shape More preferably 0 or more and 5 × 10 ⁻³ or less.

As shown in FIG. 1, the polyester monofilament for a screen wrinkle of the present invention has a birefringence Δn at a position E of 1 μm from the fiber surface I toward the center in an arbitrary fiber cross section C perpendicular to the fiber center axis B. The difference from the birefringence Δn at the position F in the center direction of 2 μm from the position (the position E of 1 μm) is preferably 0 or more and 7 × 10 ⁻³ or less, more preferably 0 or more and 5 × 10 ^{−. 3} or less. When the difference between the birefringence Δn at a position of 1 μm from the fiber surface I toward the center and the birefringence Δn at the position F in the center direction of 2 μm from the position (position E of 1 μm) exceeds 7 × 10 ⁻³ In the fiber surface layer H, there is a gradient in the fiber structure, and stress may concentrate on the highly oriented portion and cause scraping.

  The single fiber fineness of the polyester monofilament for screen wrinkles of the present invention is preferably 40 dtex or less from the need for screen wrinkles, and preferably 4 dtex or more from the standpoint of yarn production. In consideration of the load in the weaving process for obtaining a high mesh screen wrinkle from such fine fine monofilaments and the printing durability and dimensional stability in screen printing, the raw yarn needs to have high strength and modulus.

  The strength of the polyester monofilament for screen wrinkles of the present invention is preferably 5.0 cN / dtex or more, 5% modulus is 2.4 cN / dtex or more, and 10% modulus is 3.4 cN / dtex or more. If the strength is too high, there is no room for the yarn to stretch, and thread breakage may occur frequently in the yarn making process and the weaving process. Therefore, the strength is preferably 7.0 cN / dtex or less, and more preferably Is 6.0 cN / dtex or less. On the other hand, if the modulus is too high, the fiber orientation may be high and scraping may occur. Therefore, preferably 5% modulus is 4.0 cN / dtex or less, 10% modulus is 5.5 cN / dtex or less, more preferably 5% modulus is 3.5 cN / dtex or less, and 10% modulus is 10% modulus or less. It is 4.5 cN / dtex or less.

  Further, in order to prevent the yarn from breaking, it is necessary to have an elongation that can absorb not only the strength but also the load, and the toughness represented by the product of the strength and the elongation is preferably 28 or more.

  Next, the manufacturing method of the single component polyester monofilament provided with the orientation uniformity of the fiber cross-sectional direction and the fiber axis direction according to the present invention will be described.

  FIG. 2 is a schematic side view for explaining a process (one-step method) when producing a polyester monofilament for a screen wrinkle according to the present invention.

  As the method for producing a single component polyester monofilament of the present invention, a one-step method as shown in FIG. 2 is preferably used in order to make the fiber structure uniform. That is, in FIG. 2, the polymer (polyester) is discharged from the spinneret 2 in the pack housing 1 and then passed through the heat insulating cylinder 3, and after passing through the yarn cooling air device 4, is not wound once by the one-step method. After passing through the oil supply roller 5 and the first godet roller 6, multistage stretching is performed by three or more hot rollers (first hot roller 8, second hot roller 9, third hot roller 10) in the temperature-controlled warming container 7. It is preferable that the yarn is wound by the yarn winding device 13 through the second godet roller 11 and the third godet roller 12. Thereby, the uniformity of the fiber structure is improved, and in addition, a high toughness yarn can be obtained. It is preferable that the first-stage magnification ratio when performing multi-stage stretching is a natural stretch ratio of 75% to 85%. When outside the above range, it may not be possible to perform uniform stretching by thinning stretching.

  The total draw ratio is preferably 3.0 to 6.0 times in order to obtain a target high strength and high modulus yarn. If the total draw ratio is less than 3.0 times, the required strength can be achieved. If the draw ratio exceeds 6.0 times, the yarn stretches enough to withstand the load during high-order processing. Therefore, thread breakage may occur frequently.

  The spinning speed of the yarn, that is, the speed of the first godet roller 6 is preferably 400 to 1100 mpm. When the speed of the first godet roller 6 is less than 400 mpm, it is difficult to stabilize the running of the yarn, and when the speed of the first godet roller 6 exceeds 1100 mpm, a fiber structure is formed before stretching. Therefore, uniform stretching cannot be performed, and not only the uniformity is lost but also the fracture toughness may be lowered.

  In order to obtain a single component polyester monofilament having a small difference in crystallinity between the fiber surface layer and the fiber center in the fiber cross-sectional direction as in the present invention, temperature control of the heat insulating cylinder 3 is important. By precisely controlling the temperature of the heat insulating cylinder 3 and suppressing the partial orientation of the fibers, it is possible to suppress stretching unevenness by performing multi-stage stretching by a one-step method, thereby forming a uniform fiber structure. .

  It is important that the atmospheric temperature in the heat insulating cylinder 3 in the present invention is 290 ° C to 320 ° C. The atmosphere temperature in the heat insulation cylinder in the present invention is the atmosphere temperature at a position 50 mm vertically downward from the center of the heat insulation cylinder 3 where the heat insulation area is 100 mm, that is, the center of the spinneret surface. When the temperature is lower than the lower limit of the ambient temperature, it is insufficient for suppressing the orientation of the entire polymer including the central portion of the polymer to be discharged. Crystal structure differences may occur between the surface layers. In particular, care should be taken because even if the lower limit temperature is slightly lower, the fracture toughness is lowered and the crystal structure is different. On the other hand, when the upper limit of the atmospheric temperature is exceeded, the uniformity and fracture toughness may be inferior due to thermal degradation of the polymer. The atmospheric temperature is more preferably 300 to 320 ° C.

  Thus, in order to strictly control the temperature of the heat insulating cylinder 3, particularly the ambient temperature, it is important to strengthen the seal of the heat insulating cylinder 3. For example, it is preferable to seal the heat insulating cylinder 3 between the heat insulating cylinder 3 and the pack housing 1 using a felt mat for high temperature insulation made of ceramic fiber and glass fiber.

  Furthermore, in order to reduce the crystal structure difference in the fiber surface layer, that is, the gradient of crystallinity in the fiber surface layer, and to reduce physical property irregularities such as fracture toughness in the fiber longitudinal direction, consideration is given to changes in ambient temperature over time. The time change is preferably 3 ° C./min or less, more preferably 1.5 ° C./min or less. When the time change exceeds 3 ° C./min, the structure may vary in the fiber cross-sectional direction and the fiber longitudinal direction due to the local orientation of the fiber.

  As a method for controlling the time change of the temperature of the heat insulating cylinder 3 as described above, it is necessary to further enhance the sealing property. For example, the material of the heat insulating cylinder 3 has a thermal conductivity of 10 to 360 kcal / m · h · ° C. A method using pure aluminum or pure copper, or a method of integrating the heat insulating cylinder 3 and the pack housing 1 can be used.

  In addition, when a high-strength, fine-fine monofilament is stretched at a high speed at a high speed, the specific surface area is smaller than that of a thick multifilament, etc., so that it is easy to slide on the roller, and between the first hot roller 8 and the second hot roller 9. Variations in the running yarn speed. This is a phenomenon that occurs because the gripping property of the second hot roller 9 is low, and a speed gradient is generated from the outlet of the first hot roller 8 to the inlet of the second hot roller 9, and variation in the yarn speed at the same position is also caused. growing. As a result, stretching unevenness occurs in the stretching process, which is a very important part for constructing the fiber structure, and a decrease in uniformity in the fiber cross-sectional direction and a decrease in uniformity in the fiber longitudinal direction are induced. Therefore, it is preferable to use a mirror roller having a surface roughness of 0.8 S or less with high gripping property for the second hot roller 9.

  The polyester monofilament for screen wrinkles of the present invention is excellent in uniformity in the fiber cross-sectional direction and fiber longitudinal direction. Therefore, in spite of being a monocomponent monofilament that is easier to scrape than a core-sheath monofilament, it is possible to suppress scraping defects during weaving while maintaining printing durability and dimensional stability with high strength and modulus. The printing accuracy of the screen can be improved. The polyester monofilament for screen wrinkles of the present invention can also be used for applications where the quality demands of screen wrinkles are strict, and can be suitably used for, for example, printing of graphic design products such as nameplate printing and compact disc labels.

  Next, the polyester monofilament for screen wrinkles of the present invention will be described in detail with reference to examples. Evaluation in the examples followed the following method.

<Thread properties>
(Single fiber fineness)
The monofilament yarn was scraped 500 m, and the value obtained by multiplying the weight of the skein by 20 was defined as the fineness.

(Measure strength, modulus and toughness)
Using the Tensilon tensile tester manufactured by Orientex, the strength, elongation, and modulus at 5% and 10% elongation were measured at an initial sample length of 20 cm and a tensile speed of 2 cm / min. The average values were taken as strength (cN / dtex), elongation (%), 5% modulus (cN / dtex) and 10% modulus (cN / dtex). In addition, the measurement is repeated five times in succession, and the toughness is calculated from the product of the square root of the elongation and the strength using the obtained strength and elongation. Was calculated.

<Fiber structure evaluation>
(Measurement of crystallinity and birefringence)
The crystallinity and birefringence distribution of the monofilament yarn were measured by laser Raman spectroscopy. For the measurement, Raman T-64000 manufactured by Horiba Joban Yvon Co., Ltd. was used, Ar + laser (514.5 nm, 50 mW) was used as the light source, and the light was condensed to 1 μm by a 100 × objective lens. Raman scattered light was detected by a CCD detector under the conditions of single mode, slit 100 μm, diffraction grating 600 and 1800 gr / mm.

After embedding the resin, the sample was sectioned by a microtome as shown in FIG. The sample slice A had a thickness of 1 μm and was cut out so as to pass through the center of the fiber (fiber center axis B). Next, in the direction of the cross-section C perpendicular to the fiber center axis B, the position E 1 μm inside from the fiber surface I, the position F in the center direction 2 μm further from the position (the position E of 1 μm), and the fiber center D At 3 points and at any 5 points (G in Fig. 1) having both ends of the fiber surface I and the fiber center D, laser Raman spectroscopic measurement is performed 3 times each, and the converted crystallinity and conversion are calculated from the average of the measured values. Birefringence was calculated. The converted crystallinity χ and the converted birefringence Δn were determined according to the following definitions.
Conversion crystallinity: χ (%) = 100 × (ρ−1.335) / (1.455−1.335)
Converted density: ρ (g / cm ³ ) = (305−Δν1730) / 209
[Delta] [nu] 1730: full width at half maximum of Raman band near 1730 cm < ^-1 > (The conversion density was empirically obtained from the half width of various PET samples.)

Converted birefringence: Δn (× 10 ⁻³ ) = 275 × (R−1) / (R + 2)
(Orientation parameter: Intensity ratio R = I1615 parallel / I1615 perpendicular) I1615 parallel: 1615 cm ^{−1 in} a deflection arrangement parallel to the fiber direction I1615 perpendicular: 1615 cm ^{−1 in} a polarization arrangement perpendicular to the fiber direction Raman band strength (converted birefringence was determined using uniaxially drawn fibers as a standard)
<Abrasion resistance evaluation>
(Forced repeated abrasion test)
A thread (monofilament yarn) is hung on a φ3 mm satin metal bar at a contact angle of 35 °, and is held at a thread tension of 2.5 g / dtex at 340 mm from the satin metal bar. Give exercise. Thereafter, the surface of the yarn was observed with a microscope, and the number of reciprocating motions when scraping was confirmed on the surface of the yarn was defined as the number of abrasions. When the number of abrasions is 3000 times or more, ○, 2500 times or more and less than 3000 times is indicated by Δ, 2000 times or more and less than 2500 times is indicated as ×, and less than 2000 times is indicated as XX, and a monofilament having an abrasion number of 2500 times or more (○ and Δ) Passed.

<Screen silk weaving evaluation>
When weaving a 300-mesh screen reed using a polyester monofilament of each of the examples and comparative examples of the present invention for both the warp and weft and a loom loom at a rotational speed of 200 rpm according to a conventional method, 1 m of the obtained screen reed ^The number of chipped defects per ³ was used as an index of wear resistance. In addition, the magnitude of tension fluctuation during weaving is used as an index of thread passage in high-order processing, and a comprehensive evaluation is performed in four stages from the viewpoint of wear resistance and high-order thread passage as described below. A monofilament of △ was accepted.
○: The number of scraping defects generated is 0.01 / m ³ or less, and the fluctuation in tension during weaving is extremely small.
Δ: The number of scraping defects generated is 0.01 / m ³ or more and 0.05 / m ³ or less, and the fluctuation in tension during weaving is small.
X: The number of scraping defects generated is 0.05 / m ³ or more and 0.10 / m ³ or less, and the tension variation during weaving is large.
XX: The number of scraping defects generated is 0.10 / m ³ or more, and the tension fluctuation during weaving is extremely large.

      Or higher evaluation is not possible.

Example 1
PET (polyethylene terephthalate) having an intrinsic viscosity of 0.78 polymerized and chipped by a conventional method and containing 0.5% by mass of titanium oxide was used. The spinning process and the drawing process are based on the one-step method shown in FIG. After the PET was melted by an extruder, the melted PET was passed through a pipe kept at a temperature of 295 ° C., and then a yarn was spun from a known single component type spinneret 2. The discharged yarn was positively warmed by a heat retaining cylinder 3 integrated with the pack housing 1 for 100 mm downward from the base surface. The set temperature of the heat insulating cylinder 3 was 377 ° C., and the material of the heat insulating cylinder 3 was pure aluminum having a thermal conductivity of 196 kcal / m · h · ° C. When the temperature inside the heat insulation cylinder was measured at a position 50 mm vertically downward from the center of the heat insulation cylinder 3, that is, the center of the spinneret surface, it was 301 ° C. and the time change was 0.9 ° C./min.

  Thereafter, air at a temperature of 25 ° C. was blown onto the yarn at a wind speed of 25 mpm by the yarn cooling air device 4 to be cooled and solidified. The cooled and solidified yarn is supplied with a spinning oil agent by an oil supply roller 5, and then a first godet roller 6 having a surface speed of 1024 mpm, a surface speed of 1034 mpm, a surface temperature of 90 ° C., and a mirror roller having a surface roughness of 0.8S are used. The first hot roller 8 having a surface speed of 3276 mpm, a surface temperature of 90 ° C., a second hot roller 9 using a mirror surface roller having a surface roughness of 0.8S, a surface speed of 4095 mpm, a surface temperature of 90 ° C. and a surface roughness of 2.5S. The final third hot roller 10 using a satin roller, the second godet roller 11 and the third godet roller 12 using a mirror surface roller having a surface speed of 4095 mpm and a surface roughness of 0.8S, and then the winding tension Polyester monofilament is wound using the yarn winding device 13 whose speed is controlled to be 0.5 g / dtex. Was Tsu. During winding, each of the first hot roller 8, the second hot roller 9, and the final hot roller 10 was covered with a metal container, and the outer wall of each container was covered with a heat insulating material (temperature control heat insulating container 7). At this time, the total stretching ratio was 4.0 times, and the first stage stretching ratio (first stage stretching ratio / total stretching ratio × 100) was 80%.

The resulting polyester monofilament has a single fiber fineness of 26.7 dtex, strength of 5.5 cN / dtex, 5% Mo (modulus) of 2.9 cN / dtex, and 10% Mo (modulus) of 3.7 cN / dtex. It was. The toughness average during 5 consecutive measurements was 31.2, and the maximum / minimum difference R was 1.8. With respect to the polyester monofilament collected without thread breakage, in the fiber cross section perpendicular to the fiber axis, the fiber center D, the position E 1 μm from the fiber surface I toward the center, the position F 2 μm further in the center direction, and the fiber surface Raman spectroscopic measurement was performed at a total of 5 points from I to the center at 5 μm and 10 μm to determine crystallinity and birefringence. As a result, as shown in Table 1, the difference between the crystallinity of the fiber center D and the crystallinity at the position E of 1 μm from the fiber surface I toward the center is 0.8%, from the fiber surface I toward the center. The difference between the crystallinity at the position E of 1 μm and the crystallinity at the position F in the center direction of 2 μm from the position is 0.5%, from the fiber surface I toward the center, from the position E of 1 μm to the fiber center D arbitrarily When the crystallinity is measured at least 5 points, the standard deviation is 0.6, and the difference between the birefringence Δn of the fiber center D and the birefringence Δn at the position E of 1 μm from the fiber surface I toward the center is 4. × 10 ^-3, the difference between the birefringence Δn in the position F of 2μm central direction from its position as the birefringence Δn in the position E of 1μm toward the center from the fiber surface I was at 4 × 10 ^-3 or less.

  Separately, using a polyester monofilament collected by the same method, a screen flaw forced rubbing test and a screen flaw evaluation were performed. The number of rubbing times in the forced rubbing test was 3000 times or more, and there was a problem of scraping defects in the weaving process. There was no occurrence, and the tension fluctuation during weaving was very small.

(Examples 2 to 4 and Comparative Examples 1 to 3 )
In Examples 2 and 3 and Comparative Examples 1 and 2 , the set temperatures of the heat retaining cylinders were changed to 385 ° C., 375 ° C., 360 ° C., and 400 ° C., respectively, and the center of the heat retaining cylinder 3, that is, the spinneret surface A polyester monofilament was obtained in the same manner as in Example 1, except that the atmosphere temperature in the heat retaining cylinder at a position 50 mm vertically downward from the center was changed as shown in Table 1. In Example 2, there was no significant difference from Example 1, and in Example 3, although the toughness was slightly reduced and the longitudinal R was slightly deteriorated, the number of abrasions in the forced abrasion test was 2500 to less than 3000. There was little fibrillation in the weaving process. On the other hand, the tension fluctuation during weaving was small.

  In Comparative Example 1, the toughness was lowered and the longitudinal R was greatly increased and the variation was increased. Further, the difference in crystallinity between the fiber surface I from the fiber surface I to the center E and the fiber center D, the gradient of the crystallinity in the fiber surface layer H (the position E 1 μm from the fiber surface I to the center and its The difference in crystallinity at position F in the 2 μm center direction further from the position) and the standard deviation of crystallinity in the fiber cross-sectional direction were inferior to those of Example 1, and the number of scratches in the forced scratch test was less than 2000 times. Unfortunately, scraping frequently occurred in weaving, and the tension fluctuation in weaving was very large.

Further, in Comparative Example 2 , the toughness was also lowered, and the longitudinal R was also greatly increased. Further, the standard deviation of the degree of crystallinity in the fiber cross-sectional direction was inferior, and the number of abrasions in the forced abrasion test was 2500 times or more and less than 3000 times. Although there was little fibrillation in the weaving process, thread breakage, which was presumed to be due to insufficient toughness, occurred frequently.

In Example 4 , the pack housing and the heat insulating cylinder are separated, and a high-temperature heat insulating felt mat made of ceramic glass fiber is used between the heat insulating cylinder and the pack housing, and the time change of the ambient temperature is 2.4 ° C./min. Increased. Variation in toughness, difference in crystallinity between position E of 1 μm from fiber surface I toward the center and fiber center D, gradient of crystallinity in fiber surface layer H (position D at 1 μm from fiber surface I toward center) And the standard deviation of the degree of crystallinity in the fiber cross-sectional direction) were slightly worsened, but the number of abrasions in the forced abrasion test was 2500 to 3000 times. Less fibrillation in the weaving process.

In Comparative Example 3 , the pack housing and the heat insulating cylinder were separated, the sealing performance of the felt mat was intentionally lowered, and the time change of the ambient temperature was further increased to 3.5 ° C./min. As a result, the difference in crystallinity between the position E of 1 μm from the fiber surface I toward the center and the degree of crystallinity between the fiber center D was not observed, but the position E of 1 μm from the fiber surface I toward the center and the fiber center. Difference in birefringence of D, crystallinity in the fiber surface layer H and gradient of birefringence (crystallinity and birefringence at a position E of 1 μm from the fiber surface I toward the center and at a position F in the center direction of 2 μm further from the position) (Difference in refraction) and the standard deviation of crystallinity in the fiber cross-sectional direction both deteriorated somewhat, and the toughness variation increased. The number of rubs in the forced rub test was 2500 or more and less than 3,000, and there was little fibrillation in the weaving process.

The results of Examples 1 to 4 and Comparative Examples 1 to 3 are shown in Table 1 above.

(Comparative Examples 4 to 6 )
In Comparative Example 4 , a polyester monofilament was obtained in the same manner as in Example 1 except that the stretching method was one-stage stretching. In Comparative Example 4 , the difference in crystallinity and birefringence between the position of 1 μm from the fiber surface toward the center and the fiber center, and the gradient of crystallinity and birefringence in the fiber surface layer (1 μm from the fiber surface toward the center). The difference in crystallinity and birefringence at a position in the center direction of 2 μm further from the position, the R in the longitudinal direction of the toughness deteriorated, and the standard deviation of the crystallinity in the fiber cross-sectional direction also deteriorated. The number of abrasions in the forced abrasion test was 2,000 times or more and less than 2500 times, and fibrillation was observed in the weaving process. In Comparative Example 5 , yarn production was carried out by a two-step method / multistage drawing, and in Comparative Example 6 , yarn production was carried out by a two-step method / single-stage drawing, and the drawing hot roller speed was changed as shown in Table 2. In both Comparative Examples 5 and 6 , the toughness average value and longitudinal variation, the difference in crystallinity and birefringence at the position of 1 μm from the fiber surface toward the center and the fiber center, and the gradient of crystallinity and birefringence in the fiber surface layer (the difference between the crystallinity and birefringence in the position of the further 2μm central direction from the position and its position of 1μm toward the center from the fiber surface), it is inferior in both the standard deviation of the crystallinity of the fiber cross-sectional direction, the comparative example 6 The worse was the worse. The number of rubbing in the forced rubbing test was less than 2000 in both Comparative Examples 5 and 6 , and weaving frequently occurred in weaving, and the tension fluctuation during weaving was very large.

The results of Comparative Examples 4 to 6 are shown in Table 2 above.

(Example 5 , Comparative Examples 7 and 8 )
In Example 5 and Comparative Examples 7 and 8 , polyester monofilaments were obtained in the same manner as in Example 1 except that the spinning speed and the total draw ratio (drawing hot roller speed) were changed as shown in Table 3. In Example 5 , although the strength and modulus were slightly higher, other than that, there was no significant difference from Example 1, and the number of abrasions in the forced abrasion test was 2500 to less than 3000, and in the weaving process There was little fibrillation, and tension fluctuation during weaving was small.

In Comparative Example 7 , the strength and modulus were significantly reduced, the difference in crystallinity and birefringence between the position E of 1 μm from the fiber surface I toward the center and the fiber center D, and the crystallinity and birefringence in the fiber surface layer H. Gradient (difference in crystallinity and birefringence at a position E of 1 μm from the fiber surface I toward the center and a position F in the center direction of 2 μm further from the position), longitudinal variation in toughness and crystallinity in the fiber cross-sectional direction. The variation was large and the fiber structure was uneven. The number of rubs in the forced rub test was 3,000 or more because of the very low orientation, but the strength and modulus were too low to achieve the strength required for wrinkles, and the fineness was large and the printing accuracy was reduced. Therefore, higher evaluation was impossible.

In Comparative Example 8 , the longitudinal variation in toughness is slightly large, the difference in crystallinity and birefringence between the position E of 1 μm from the fiber surface I toward the center and the fiber center D, the crystallinity and birefringence in the fiber surface layer H. Both the gradient of crystallinity (difference in crystallinity and birefringence at a position E of 1 μm from the fiber surface I toward the center and a position F in the center direction of 2 μm further from that position), and the standard deviation of the crystallinity in the fiber cross-sectional direction are deteriorated. did. As a result, the number of rubbing in the forced rubbing test was less than 2,000, and there were frequent scraping defects during weaving, and the tension fluctuation during weaving was very large.

The results of Example 5 and Comparative Examples 7 and 8 are shown in Table 3.

(Examples 6-7, Comparative Examples 9 to 10)
In Examples 6 and 7 and Comparative Examples 9 and 10 , polyester monofilaments were obtained in the same manner as in Example 1 except that the draw ratio and draw hot roller speed were changed as shown in Table 4. In Examples 6 and 7 , there is no significant difference from Example 1, the number of abrasions in the forced abrasion test is 3000 times or more, there is no fibrillation in the weaving process, and the tension fluctuation in weaving is very small. It was.

In Comparative Example 9 , the toughness average value decreased and the longitudinal variation also deteriorated. Difference in crystallinity between the position E of the fiber surface I from the fiber surface I and the center of the fiber and the gradient of the crystallinity in the fiber surface layer H (position E of 1 μm from the fiber surface I toward the center and further from the position) The difference in crystallinity at position F in the 2 μm central direction) was not significantly different from that in Example 1, but the standard deviation of crystallinity in the cross section direction was inferior to that in Example 1. The number of rubbing in the forced rubbing test was 2500 or more and less than 3000, there was little fibrillation in the weaving process, and the tension fluctuation in weaving was small. Further, in Comparative Example 10 , the difference in crystallinity between the position E of 1 μm from the fiber surface I toward the center and the fiber center, the gradient of crystallinity in the fiber surface layer H (1 μm from the fiber surface I toward the center). The difference in crystallinity at position E and position F in the center direction of 2 μm further from that position), the standard deviation of the crystallinity in the fiber cross-sectional direction deteriorated, and the number of abrasions in the forced abrasion test was 2000 times or more and less than 2500 times There were some flaws in weaving, and there were large fluctuations in tension.

The results of Examples 6 to 7 and Comparative Examples 9 to 10 are shown in Table 4 above.

( Comparative Example 11)
In Comparative Example 11, a polyester monofilament was obtained in the same manner as in Example 1 except that a satin roller having a surface roughness of 2.5S was applied to the second hot roller. The toughness average value slightly decreased, and the longitudinal R was inferior. In addition, the standard deviation of crystallinity in the fiber cross-sectional direction was also deteriorated, the number of abrasions in the forced abrasion test was 2500 or more and less than 3000, there was little fibrillation in the weaving process, and the tension fluctuation in weaving was small. It was slightly inferior to Example 1.

The results of Comparative Example 11 are shown in Table 5.

A: Sample section B: Fiber center axis C: Fiber cross section perpendicular to the fiber axis D: Fiber center E: Position of 1 μm from the fiber surface toward the center F: Position in the center direction of 2 μm further from E G: Fiber surface I And any five points with fiber center D at both ends H: Fiber surface layer I: Fiber surface 1: Pack housing 2: Spinneret 3: Heat insulation cylinder 4: Yarn cooling air device 5: Oil supply roller 6: First godet Roller 7: Temperature control heat retaining container 8: First hot roller 9: Second hot roller 10: Final hot roller 11: Second godet roller 12: Third godet roller 13: Yarn winding device

Claims (2)

A monocomponent polyester monofilament comprising polyethylene terephthalate as a main constituent, and at an arbitrary fiber cross section perpendicular to the fiber axis of the polyester monofilament, the crystallinity of the fiber center and the position 1 μm from the fiber surface toward the center The difference from the crystallinity is 4% or less , the standard deviation when the crystallinity is arbitrarily measured at least 5 points from the fiber surface to the fiber center is 2 or less, and the strength is 5.0 cN / dtex or more and 7.0 cN / A polyester monofilament for screen wrinkles, characterized by a dtex or less, a 5% modulus of 2.4 cN / dtex or more and 4.0 cN / dtex or less .   In an arbitrary fiber cross section perpendicular to the fiber axis, the difference between the crystallinity at a position of 1 μm from the fiber surface toward the center and the crystallinity at a position of 2 μm further from the position is 2% or less. The polyester monofilament for a screen bag according to claim 1.

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