JP2007113151A - Melt spinning method of polyester monofilament for screen gauze and polyester monofilament for screen gauze - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a polyester monofilament for screen gauze, having excellent fiber diameter uniformity. <P>SOLUTION: The melt spinning method of a polyester monofilament for screen gauze by using a polyester having ≤270°C melting peak temperature in a differential scanning calorimetry and 0.45-1.20 intrinsic viscosity comprises, in melt spinning of a monofilament, using an extruder having ≤50ppm oxygen concentration at a chip supply part and ≤295°C chip melt temperature, keeping the retention time of ≤20 minutes for the polymer from the biting of chips in an extruder screw to discharging at a spinneret and controlling the spinning temperature ≤295°C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a melt spinning method for polyester monofilaments for screen wrinkles, and more specifically, it suppresses the generation of heat-degraded products such as gelled products during melt spinning, and produces compact disc (CD) printing, graphic printing, and plasma display. The present invention relates to a method for melt spinning polyester monofilaments for screen wrinkles, in which the uniformity of the fine diameter in the longitudinal direction used in the heat-sensitive stencil printing is particularly important.

  Conventionally, mesh fabrics made of natural fibers such as silk and inorganic fibers such as stainless steel have been widely used as printing screen fabrics. However, in recent years, synthetic fabric meshes that excel in flexibility, durability, and cost performance have been favored. Among them, polyester monofilaments are widely used because they have high dimensional stability and are suitable for screens.

  In recent years, the spread of CDs in the home appliance industry and the printing and publication of design products by computer graphics have become mainstream, and further, the spread of plasma displays has been attempted, and attempts have been made to use synthetic mesh for thermal stencil printing. There is a demand for a screen with a finer mesh and particularly excellent opening uniformity. For this reason, for example, if there is a portion where the diameter of the monofilament is locally thick, unevenness occurs in the opening of the screen wrinkle, which immediately causes a printing defect and the commercial value is lost. That is, in order to satisfy the required quality in the above applications, it is an important issue to provide a monofilament for screen wrinkles with fineness, high strength, high modulus and excellent longitudinal diameter uniformity. .

  When producing a monofilament using polyester, a method of drawing after winding an undrawn yarn once, and a direct spinning drawing method of drawing without winding up an undrawn yarn are known. However, the melt spinning method is very important in securing the high elongation and uniformity of the fine diameter. This is because no matter how foreign material is mixed in the unstretched fiber structure, stretching stress concentrates on the foreign material and induces uneven stretching even when uniform stretching is achieved in the stretching process. is there.

  Various methods for suppressing thermal degradation in polyester melt spinning have been proposed.

  For example, when an aromatic polyester having a flow temperature of 280 to 380 ° C. and exhibiting anisotropy at the time of melting is melt-spun by an extruder-type spinning machine, a supply section of the polyester to the extruder and, if necessary, the periphery thereof Substituting with an inert gas or pre-vacuum, and then substituting with an inert gas, the oxygen concentration of the portion where the polyester is inserted into the extruder is spun to 5 vol% or less (see Patent Document 1) It is.

  As another proposal, when spinning polyester, the atmosphere under the discharge holes is set to 300 ° C. or higher, and the atmosphere under the discharge holes is set to an oxygen concentration of 1% or less and a water concentration of 100 ppm or less (see Patent Document 2). It is.

  In the former proposal, an anisotropic aromatic polyester having a flow temperature of 280 to 380 ° C. is used. Therefore, the spinning temperature during actual melt spinning needs to be 300 ° C. or higher. If the polymer stays in the bent portion existing in the polymer pipe or the polymer flow path of the spinning pack, the polyester gels with the passage of time and becomes a substantially foreign substance. The diameter change cannot be suppressed. Further, the obtained fiber has high strength and modulus, but the elongation is as low as 5% or less, so that it is difficult to industrially weave screen wrinkles.

In the latter proposal, the oxygen concentration in the atmosphere below the discharge hole is reduced to suppress a decrease in molecular weight immediately after discharge. However, this does not prevent deterioration in the melted part or the polymer pipe. It acts on the surface of the fiber structure of the yarn, but the thread passing time of the discharge part is very short compared to the melted part and the polymer piping, and does not act inside the fiber structure. Although an improvement effect is observed with respect to yarn breakage due to dirt adhesion, it is difficult to substantially suppress the generation of fine foreign matters on the order of several microns such as gelled products.
Japanese Patent Laid-Open No. 61-1113816 (Claims) JP-A-2-234910 (Claims)

  The present invention solves the above-mentioned problems, and printing due to unevenness in opening when used for screen printing when applying paste used as a dielectric or an electrode to a substrate during CD printing, graphic printing, or plasma display manufacturing. To provide a method for obtaining a monofilament for screen wrinkles that has fineness, high strength, and high modulus without causing defects, and also has fine diameter uniformity in the longitudinal direction.

  In order to achieve the above object, the present invention provides a polyester chip for melt spinning a monofilament using polyethylene terephthalate having an intrinsic viscosity of 0.45 to 1.20 having a melting peak temperature of 270 ° C. or less in differential scanning calorimetry. Is supplied to an extruder extruder under an oxygen concentration of 50 ppm or less, melted at a temperature of 295 ° C. or less, and the polymer residence time from when the tip is caught in the screw of the extruder until it is discharged by the spinneret is within 20 minutes. As described above, the method is a melt spinning method for polyester monofilaments for screen wrinkling, characterized by discharging and spinning at a spinning temperature of 295 ° C. or lower.

  The melt spinning method of the polyester monofilament for screen wrinkles of the present invention uses the most suitable polyester for the screen wrinkle monofilament, and is particularly important for obtaining the fine diameter uniformity in the longitudinal direction. By making the temperature, polymer residence time, and spinning temperature appropriate, it has high diameter uniformity that could not be achieved by conventional manufacturing methods. Polyester monofilaments for screen wrinkles suitable for all high-precision printing such as screen wrinkling printing when applying a paste used as an electrode can be obtained.

  Hereinafter, the present invention will be described in detail.

  The polyester in the present invention is polyethylene terephthalate (hereinafter abbreviated as PET) whose repeating unit is ethylene terephthalate, and is melt-spun using PET. The melting peak temperature in differential scanning calorimetry (hereinafter abbreviated as DSC) of the PET used is 270 ° C. or less. When a polymer having a high peak temperature exceeding 270 ° C. is used, the melting temperature and the spinning temperature must be 300 ° C. or higher, and it becomes difficult to suppress thermal degradation of the polymer. Since the resulting monofilament has a significantly low elongation, it is unsuitable for screen knot weaving. Preferably, PET having a melting peak temperature of 245 to 260 ° C is preferably used.

  The intrinsic viscosity of PET is 0.45 to 1.20 in order to obtain a monofilament strong elongation. The intrinsic viscosity of PET used for the single component yarn is preferably 0.68 to 1.20, more preferably 0.70 to 1.00. In the case of a core-sheath composite yarn, the intrinsic viscosity of PET used for the core component is preferably 0.68 to 1.20, more preferably 0.70 to 1.00. The limit of PET used for the sheath component of the core-sheath composite yarn is 0.45 to 0.70, and suppresses the occurrence of scum during weaving of screen silkworms. When the sheath component is copolymerized PET or polyamide, peeling from the core component is likely to occur, the scum suppressing effect is not sufficient, and the strength is hardly exhibited. The PET used for the sheath component of the core-sheath composite yarn is more preferably one having an ultimate limit of 0.50 to 0.65.

  Regarding PET, it is known that when heated under aerobic conditions, carboxyl end groups and the like cause a crosslinking reaction and gelation proceeds, and the gelled product usually has a significantly higher melting point than PET and is extremely gelled. As it progresses, the DSC melting peak temperature exceeds 500 ° C. In the production of a polyester monofilament, if a gelled product is mixed in the discharged yarn, it becomes a foreign matter in the fiber structure, and stress is concentrated on the gelled product at the time of stretching, thereby inducing fine stretching unevenness. For example, in a monofilament having a fineness of 10 dtex and a fine diameter of 30 μm, when an irregular gelled material of about 2 to 10 μm is mixed, the fine diameter is increased to about 35 to 55 μm over a length of 2 to 5 mm. When a screen wrinkle is woven using a monofilament containing this thickened part, the opening of the part becomes smaller than that of the normal part, resulting in a printing defect. .

  In order to obtain a high fiber diameter uniformity so as to avoid the above-mentioned screen defects, in the melt spinning method of the present invention, in particular, with PET having a melting peak temperature of 270 ° C. or lower, It is necessary to make the oxygen concentration of the steel be 50 ppm or less and at the same time the melting temperature is 295 ° C or less. That is, when supplying the polyester chip to the extruder extruder, the oxygen concentration is 50 ppm or less, preferably 20 ppm or less, more preferably 0 to 10 ppm, and the melting temperature of the polyester chip is 295 ° C. or less, preferably 275 to 290 ° C. More preferably, it is 275-285 degreeC.

  Moreover, the extruder used for the melt spinning of the present invention is an extruder extruder. Suppresses the polymer from remaining abnormally in the melted part by continuously biting the chip into the extruder and forcibly discharging it with a screw, and minimizing the gap between the screw and the cylinder. It is. Note that the tip supply section of the extruder in the present invention indicates the portion directly above the barrel of the extruder, and the melting temperature of the tip indicates the temperature of the cylinder heater that covers and heats the extruder cylinder. The cylinder heater temperature which heats the melt part of a ruder screw is shown. For example, the temperature of the cylinder heater 2 is shown in the P25-25A type extruder manufactured by Nippon Steel Works.

  In the melt spinning method of the present invention, the polymer residence time from the time when the tip is caught in the screw of the extruder to the time when the tip is discharged by the spinneret is within 20 minutes. Generation and gelation progress are suppressed. More preferably, it is within 15 minutes.

  The fineness of the monofilament in the present invention is conventionally known to be 18 dtex or less, especially for screen printing used for CD printing, graphic printing, and paste application to a plasma display substrate. In order to stabilize the dimensions of the heel, a tension of a certain value or more is required, and the tension is determined by strength (cN / dtex) × mesh. In order to increase the density, it is generally sufficient to use a monofilament having a fineness. However, since the monofilament fineness and the mesh density are not completely inversely proportional, it is necessary to increase the breaking strength as the fineness is increased. For this reason, in the case of the monofilament in the present invention, the breaking strength is preferably 5.6 cN / dtex or more, more preferably 6.0 cN / dtex or more. In general, the polyester fiber has a breaking elongation that decreases as the breaking strength is increased. However, when the elongation is excessively reduced, the appropriate flexibility when used in a screen wrinkle is impaired and repeated. It is preferable to set the elongation at break to 10% or more in order to increase the dimensional change of the wrinkles at the time of printing or induce scraping during weaving. More preferably, it is 15% or more, More preferably, it is 18% or more.

  The monofilament of the present invention may be produced by a method in which an undrawn yarn is once wound and then drawn, or a direct spinning drawing method in which an undrawn yarn is drawn without being taken up once. The melting conditions such as the spinning temperature satisfy the scope of the present invention. For example, in the method in which the undrawn yarn is wound up and then drawn, the undrawn yarn is drawn at a spinning speed of 800 to 1500 m / min. After winding, the yarn is preheated with a hot roller at a temperature of 85 to 95 ° C, drawn at a draw ratio of 3.75 to 5.30, and then heat set with a hot roller or a hot plate heater at a temperature of 120 to 220 ° C. By doing so, the physical properties can be obtained. In the direct spinning drawing method, the physical properties are obtained by drawing at a spinning speed of 200 to 1000 m / min, drawing in one to three stages while preheating at a temperature of 85 to 110 ° C., and heat setting at a temperature of 120 to 220 ° C. However, in particular, in order to obtain a breaking strength of 6.0 cN / dtex or more, stretching in two to three stages is preferable in terms of uniform stretching and operability.

  The cross-sectional shape of the monofilament in the present invention is that it is easy to obtain stable yarn-making property and screen weaving property, and in order to suppress the occurrence of halation when coating and exposing the emulsion after weaving, In view of the stability of the shape of the lattice space formed by the intersection of the warp yarn and the weft yarn, a round cross section is preferable. Further, in order to improve the effect of suppressing the halation, an ultraviolet absorber may be included in the monofilament, and when the ultraviolet absorber is included, in order to suppress the occurrence of scum at the cocoon blades when weaving the screen cocoon. Organic compounds are preferred, and benzotriazole compounds and anthraquinone compounds are preferred. More preferably, an anthraquinone-based yellow pigment is preferably used, which eliminates the need for a dyeing process after weaving screen screen and can reduce the weaving cost.

Hereinafter, the present invention will be described in detail with reference to examples. The evaluation in the examples followed the following method.
1. Intrinsic viscosity (IV)
It calculated from the value measured at 25 degreeC in orthochlorophenol.
2. DSC melting peak temperature Using DSC821e manufactured by Mettler, high-purity indium (Tm = 156.61 ° C., ΔHm = 6.86 cal / g) was used for temperature and calorie calibration, under N ₂ inflow of 50 ml / min. The measurement was performed at a temperature elevation rate of 10 ° C./min and a sample amount of 10 mg.
3. Fineness, rupture strength and elongation Using a measuring instrument having a circumference of 100 cm, the value (g) obtained by measuring the casserole 100 times with an electronic balance was multiplied by 100. This was repeated 5 times for one monofilament, and the average value was taken as the measured fineness (dtex). In addition, using a Tensilon tensile tester manufactured by Orientex Co., Ltd., a tensile elongation curve measured 5 times per drawn yarn at an initial sample length of 20 cm and a tensile speed of 2 cm / min. A value obtained by dividing the average value by the drawn yarn fineness (dtex) was used.
4). Uniformity of diameter Fineness of the surface roughness Rz 0.8μm or less Yuasa Yarnichi ceramics guides are fixed in a slit shape, using a gap gauge with work accuracy of ± 1.0μm, to the fineness D of the monofilament to be evaluated 1,961 × {D / (10,000 × π)} prepared by adjusting the slit width to a width of ^0.5 . For example, for a monofilament having a fineness of 10 dtex, the slit width is 35 μm. This is called a slab catcher. This slab catcher was installed on the yarn path of production time, the monofilament was allowed to pass at the same time as production, and the number of monofilaments captured at the slit was counted and converted to the number per million meters. The trapped portion is a portion where the fine diameter is large compared to the normal portion, and the trapped number is less than 0.6 / 1,000,000 m, △, 0.6 to 1 / 1,000,000 m, △ / The thing exceeding 1 million m was set as x, and ◯ and Δ were set as pass.

Example 1
Using a composite spinning machine made of Nippon Steel Works Extruder Extruder P25-25A type, PET with a melting peak temperature of 265 ° C. and an intrinsic viscosity of 1.20 was used as the core polymer, the tip supply part oxygen concentration was 50 ppm, The melting temperature was 295 ° C., the sheath polymer was PET containing a melting peak temperature of 255 ° C., an intrinsic viscosity of 0.65, and titanium oxide containing 0.3 wt%, the tip supply portion oxygen concentration was 10 ppm, the tip melting temperature was 285 ° C. The polymer discharge rate is adjusted so that the composite cross-sectional area ratio (core: sheath) is 80:20, the yarn is discharged from the die at a spinning temperature of 295 ° C., and the distance from the yarn at an inner wall temperature of 300 ° C. Was passed through a heating zone having a length of 4.5 cm and a length of 10 cm, and then cooled and solidified, and the core-sheath composite monofilament undrawn yarn was once wound at a spinning speed of 900 m / min. At this time, the polymer pipe and the flow path in the pack and the filter layer are set so that the residence time until the tip of the core component is caught in the extruder screw and discharged from the die is 20 minutes and the residence time of the sheath component is 15 minutes. The volume of the part was adjusted.

  This undrawn yarn was drawn at a rate of 4.39 times between a first hot roll having a surface temperature of 90 ° C. and a second hot roll having a surface temperature of 100 ° C., and then a second hot roll and a third hot roll having a surface temperature of 200 ° C. Then, the core-sheath composite monofilament having a fineness of 9.9 dtex was wound up by giving a relaxation of 4.2% between the third hot roll and the cold roll having a surface temperature of room temperature. The monofilament obtained had a breaking strength of 8.1 cN / dtex and a breaking elongation of 13.5%. Using this monofilament, a 315 mesh screen wrinkle was woven using a slewer weaving machine. The number of diameter-decreasing portions was 0.9 / 1,000,000 m, which was an occurrence frequency with no problem in weaving screen wrinkles used for industrially high-precision printing. The trapped thickened diameter portion was collected, and the amorphous insoluble material after immersion in a hexafluoroisopropanol solvent was analyzed by FT-IR. As a result, it was found to be a PET gel product.

Example 2
Using a composite spinning machine comprising an extruder similar to that in Example 1, PET having a melting peak temperature of 255 ° C. and an intrinsic viscosity of 0.70 was used as the core polymer, the tip supply portion oxygen concentration was 10 ppm, and the tip melting temperature was 285 ° C. The sheath polymer is PET having a melting peak temperature of 253 ° C., an intrinsic viscosity of 0.51, and titanium oxide containing 0.35 wt%, the tip supply portion oxygen concentration is 10 ppm, the tip melting temperature is 275 ° C., and the composite cross-sectional area ratio is 80:20. The polymer discharge rate was adjusted so as to be, after passing through the same heating zone as in Example 1 at a spinning temperature of 290 ° C., cooling and solidifying, and a core-sheath composite monofilament undrawn yarn at a spinning speed of 1200 m / min Was wound up once. At this time, the volume of the polymer pipe and the polymer flow path in the pack and the filter layer were adjusted so that the residence time of the core component was 14 minutes and the residence time of the sheath component was 15 minutes.

  This unstretched yarn is stretched by 4.27 times between a first hot roll having a surface temperature of 90 ° C. and a second hot roll having a surface temperature of 130 ° C., and then between the second hot roll and a cold roll having a surface temperature of room temperature. A core-sheath composite monofilament having a fineness of 9.9 dtex was wound with a 1.35% relaxation. The resulting monofilament had a breaking strength of 6.1 cN / dtex and a breaking elongation of 23.5%. As a result of weaving a 315 mesh screen wrinkle with a slewer weaving machine using this monofilament, a thick slab catcher captured. The number of diameter-decreasing portions was 0.3 / 1,000,000 m, and a good-quality screen wrinkle was obtained.

Example 3
Using a single component spinning machine composed of the same extruder as in Example 1, using a PET containing a melting peak temperature of 256 ° C., an intrinsic viscosity of 0.78, and a titanium oxide content of 0.35%, a tip supply part oxygen concentration of 50 ppm, a tip After adjusting the volume of the polymer flow path in the polymer pipe / pack and the filtration layer so that the melting temperature is 285 ° C. and the polymer residence time is 10 minutes, the monofilament yarn is discharged and cooled and solidified at a spinning temperature of 285 ° C. The single component monofilament undrawn yarn was once wound up at a spinning speed of 800 m / min.

  This unstretched yarn was stretched 4.43 times between the first hot roll having a surface temperature of 90 ° C. and the second hot roll having a surface temperature of 130 ° C., and then between the second hot roll and the cold roll having a surface temperature of room temperature. A single component monofilament having a fineness of 13.0 dtex was wound up by stretching at a .01 magnification. The resulting monofilament had a breaking strength of 5.9 cN / dtex and a breaking elongation of 32.1%. As a result of weaving a 330-mesh screen wrinkle using this monofilament with a slewer weaving machine, The number of diameter-decreasing portions was 0.2 / 1,000,000 m, and a screen flaw of good quality was obtained.

Example 4
Other than adjusting the volume of the polymer flow path and the filter layer in the polymer piping / pack so that the chip melting temperature is 295 ° C., the spinning temperature is 295 ° C., the oxygen concentration of the chip supply part is 20 ppm, and the polymer residence time is 15 minutes. A single component monofilament was obtained in the same manner as in Example 3. The resulting monofilament had a breaking strength of 5.8 cN / dtex and a breaking elongation of 30.8%. A monofilament was used to weave a 330 mesh screen wrinkle with a slewer weaving machine. The number of diameter-decreasing portions was 0.7 / 1,000,000 m, and a screen wrinkle having no problem was obtained.

Comparative Example 1
A core-sheath composite monofilament was obtained in the same manner as in Example 1 except that the spinning temperature was 310 ° C. Although there was no problem in the strength and elongation characteristics of the obtained monofilament, the number of thickened diameter parts captured by the slab catcher was 2.5 / 1,000,000m as a result of weaving a 315 mesh screen with a Sulzer weaving machine. It was not only a screen with poor quality for use in high-precision printing, but also the abnormal diameter of the fine diameter was extracted by inspection, but the extraction work took a lot of time and the fine diameter Product loss due to abnormalities also increased, resulting in inferior manufacturing efficiency.

Comparative Example 2
A core-sheath composite monofilament was obtained in the same manner as in Example 2 except that the oxygen concentration of the chip supply part of the core component was 100 ppm. Although there is no problem in the strength and elongation characteristics of the obtained monofilament, as a result of weaving a screen mesh of 315 mesh with a Sulzer weaving machine, the number of thickened diameter parts captured by a slab catcher was 3.8 / 1 million m. As with the result of Comparative Example 1, the results were poor in quality and production efficiency.

Comparative Example 3
A single-component monofilament was obtained in the same manner as in Example 3 except that the volume of the polymer pipe and the polymer flow path in the pack and the filter layer were adjusted so that the polymer residence time was 40 minutes. As a result of weaving a 330-mesh screen wrinkle using this monofilament with a Sulzer weaving machine, the number of thickened diameter parts captured by a slab catcher is 3.0 pieces / 1,000,000 m, similar to other comparative examples. In addition, the quality and production efficiency were inferior.

Comparative Example 4
Using a PET containing a melting peak temperature of 265 ° C., an intrinsic viscosity of 1.20 and titanium oxide of 0.35%, the chip melting temperature is 300 ° C., and the polymer residence time is 20 minutes. A single component monofilament was obtained in the same manner as in Example 4 except that the volume of the filter layer was adjusted. As a result of weaving a 330-mesh screen wrinkle using this monofilament with a Sulzer weaving machine, the number of thickened diameter parts captured by a slab catcher was 3.6 pieces / 1,000,000 m, similar to other comparative examples. In addition, the quality and production efficiency were inferior.

Claims (3)

  When a monofilament is melt-spun using polyethylene terephthalate having an intrinsic viscosity of 0.45 to 1.20 having a melting peak temperature of 270 ° C. or lower in differential scanning calorimetry, a polyester chip is extruded under an oxygen concentration of 50 ppm or lower. Supply to the extruder, melt at a temperature of 295 ° C or lower, discharge the polymer at a spinning temperature of 295 ° C or lower with a polymer residence time of 20 minutes or less from the time when the chip is caught in the screw of the extruder to the time when it is discharged from the spinneret. A process for melt spinning polyester monofilaments for screen wrinkles.   A polyester monofilament for screen wrinkles produced by the melt spinning method according to claim 1, wherein the fineness is 18 dtex or less, the breaking strength is 5.6 cN / dtex or more, and the breaking elongation is 10% or more. Monofilament.   The monofilament is a core-sheath composite yarn, the intrinsic viscosity of polyethylene terephthalate used for the core component is 0.68 to 1.20, the intrinsic viscosity of the polyester used for the sheath component is 0.45 to 0.70, and the core: sheath 3. The polyester monofilament for screen wrinkles according to claim 2, wherein the composite cross-sectional ratio is 90:10 to 70:30.