JP4881124B2 - Polyester monofilament for screen wrinkles and method for producing the same - Google Patents

Description

  The present invention relates to a polyester monofilament for screen wrinkles which has a good weaving property and which can provide a high mesh screen wrinkle having excellent durability and printing accuracy.

  Conventionally, in the field of screen printing, high precision, that is, high strength and high elastic modulus has been demanded, and stainless steel screens have been widely used. However, although stainless monofilament has high strength and high elastic modulus and undergoes very little dimensional change with respect to moisture absorption or temperature change, it tends to yield even with minute strains, making permanent deformation during repeated printing and making it unusable.

  In order to solve such problems, various screen cages made of synthetic monofilaments have been proposed. For example, screen cages using monofilaments made of polyethylene terephthalate, which is a thermoplastic polymer, have been proposed in Patent Documents 1-3. Yes. However, the monofilaments proposed for them are low in strength and elastic modulus, so that weaving under high tension is difficult and it is difficult to obtain a high mesh screen wrinkle due to the tension applied to the wrinkle forming process. .

  On the other hand, for the purpose of high strength and high elastic modulus, a screen cage made of polyethylene naphthalate is proposed in Patent Document 4 and the like. Polyethylene naphthalate is expected to produce higher mesh mesh weaves because the strength and elastic modulus of monofilaments are greatly improved compared to polyethylene terephthalate, but it is highly oriented and fluff and fibrils are generated. There is a drawback that yarn breakage occurs frequently during weaving.

  In order to solve this problem, Patent Document 5 proposes a method using polyethylene naphthalate as a core component and polyethylene terephthalate as a sheath component. In this publication, the stress relaxation time is set to 5000 seconds or more by applying a cold stretch treatment after the heat stretching. However, the monofilament obtained by the above method has a problem that the compression force acts at the contact point where the warp and the weft intersect at the pressure during screen printing, fibrils are generated, and the reliability of high-quality printing is low. In addition, the technique called cold stretch treatment has a problem in releasability, such as insufficient shrinkage due to insufficient set, and a whispered appearance. It was also confirmed that the knot strength and hook strength of the monofilament were very low.

  Patent Document 6 discloses that in the core-sheath type composite monofilament, the glass transition temperature of the copolyester forming the sheath is lower than the glass transition temperature (79 ° C.) of the polyester forming the core, and is set to 35 to 73 ° C. Has proposed a monofilament for high performance screens with less fibrils and scum. However, since the sheath component is a polyester having a low glass transition temperature, the sheath component is insufficiently solidified on the spinning line, resulting in fluctuations in spinning tension, which is essential for high-density printing quality. It has been found that the uniformity of the ink is lost, which causes a problem in precision printing.

JP 62-104795 A JP-A-62-215013 JP-A-2-127513 Japanese Patent Laid-Open No. 4-100914 Japanese Patent No. 2959195 Japanese Patent No. 2580816

  The present invention has been made against the background of the above prior art, and an object of the present invention is to provide a polyester monofilament for screen wrinkles having good weaving properties and excellent durability and printing accuracy. Another object of the present invention is to provide a method for stably producing the above-mentioned polyester monofilament for screen wrinkles.

  As a result of the study by the present inventors, the knot strength and hook strength of the monofilament used for the weaving quality and quality of the screen are greatly affected, and furthermore, these physical properties are satisfied simultaneously when a specific production method is selected. The present inventors have found that a monofilament can be obtained.

Thus, according to the present invention, there is provided a core-sheath type composite monofilament comprising a polyester mainly composed of polyethylene naphthalate as a core component and a polyester mainly composed of polyethylene terephthalate as a sheath component, wherein the core-sheath weight ratio is a core component / The sheath component = 80 / 20-40 / 60, the core-sheath weight ratio was compounded as the core component / sheath component = 80 / 20-40 / 60, and the unstretched monofilament melted and discharged from the composite spinneret was spun at a spinning speed of 500- Winding up at 1500 m / min, preheating it at a preheating temperature of 80 to 130 ° C., passing it through a non-contact heater at 120 to 220 ° C., and drawing and heat setting at a draw ratio of 3.6 to 4.5 times obtained by the following (1) to (4), characterized by satisfying simultaneously screen mesh cloth for the polyester monofilament is provided.
(1) Nodule strength ≧ 3.0 cN / dtex
(2) Hook strength ≧ 2.5 cN / dtex
(3) Tensile strength ≧ 4.5 cN / dtex
(4) Elongation at break ≧ 10%

In addition, a polyester having polyethylene naphthalate as a main component is a core component, a polyester having polyethylene terephthalate as a main component is a sheath component, and the weight ratio of core / sheath is core component / sheath component = 80/20 to 40/60. winding a mono filament discharged melted at a spinning speed 500 to 1500 / min from a composite spinneret, which was preheated at a preheating temperature 80 to 130 ° C., stretched by further passing through the non-contact heater of 120 to 220 ° C. A method for producing a polyester monofilament for screen wrinkles is provided, which is drawn and heat-set at a magnification of 3.6 to 4.5 times .

  Since the polyester monofilament for screen wrinkles of the present invention can be woven stably even under high tension, a high-quality high mesh screen wrinkle can be obtained from this monofilament. For this reason, since the screen wrinkles are excellent in fluff and printing accuracy, precise screen printing can be performed stably for a long period of time.

  The polyester monofilament for screen wrinkles of the present invention is a core-sheath type composite monofilament having a polyester whose main component is polyethylene naphthalate as a core component and a polyester whose main component is polyethylene terephthalate as a sheath component.

  The polyethylene naphthalate constituting the core component is a polyester having ethylene-2,6-naphthalenedicarboxylate as a main repeating unit, and a third component other than naphthalene-2,6-dicarboxylic acid and ethylene glycol is converted into a total acid. The copolymer may be copolymerized at a ratio of 20 mol% or less, preferably 10 mol% or less, and polyethylene-2,6-naphthalenedicarboxylate homopolyester is particularly preferable.

  On the other hand, the polyethylene terephthalate constituting the sheath component is a polyester having ethylene terephthalate as a main repeating unit, and the third component other than terephthalic acid and ethylene glycol is 20 mol% or less, preferably 10 mol% or less of the total acid component. However, polyethylene terephthalate homopolyester is particularly preferable.

  Each of the above polyesters has various additives such as titanium oxide, alumina, calcium compounds, color pigments, ultraviolet absorbers, stabilizers such as phosphoric acid, phosphorous acid, and esters thereof as long as the object of the present invention is not impaired. It may be included.

  In the monofilament of the present invention, the cross-sectional shape of the core component and the sheath component may be any shape of circular, triangular, square, multi-loval cross section, and even a flat cross section as long as the above requirements are satisfied, The core component may be either single-core or multi-core, but from the standpoint of yarn production, it is preferable that the core component and the sheath component have a single-core core-sheath type composite cross section having a concentric circular shape.

  Further, at the time of weaving, the monofilament is bent more than 250 times per minute, and it is necessary to suppress the breakage of the monofilament. On the other hand, the present inventors paid attention to the knot strength and hook strength of the monofilament. That is, in the present invention, it is important that the knot strength of the monofilament is 3.0 cN / dtex or more, preferably 3.5 cN / dtex or more, and the hook strength is 2.5 cN / dtex or more, preferably 2.6. With this, it is possible to suppress breakage even with respect to the bending.

  In the present invention, the monofilament must have a tensile strength of 4.5 g / dtex or more, preferably 5.0 g / dtex or more, and a breaking elongation of 10% or less, preferably 12% or less. If the tensile strength is less than 4.5 g / dtex, performance such as sufficient durability as a screen 紗, especially a high mesh screen で き, cannot be exhibited. If the elongation at break is less than 10%, the above hook strength and knot strength are achieved. It tends to be difficult to do.

  The monofilament of the present invention described above has a polyester whose main component is polyethylene naphthalate as a core component and a polyester whose main component is polyethylene terephthalate as a sheath component, and the core-sheath weight ratio is core component / sheath component = 80/20. It can be produced by winding an unstretched monofilament that has been composited as ˜40 / 60 and melted and discharged from a composite spinneret at a spinning speed of 500-1500 m / min and stretched at a preheating temperature of 80-130 ° C.

  In the above melt spinning, the intrinsic viscosity of polyethylene terephthalate is preferably 0.600 to 0.650, and the intrinsic viscosity of polyethylene naphthalate is preferably 0.580 to 0.645. Melt and introduce into core-sheath type spinneret. A range of 5 to 40 cm below the spinneret is a heat-retaining region so that the base surface temperature is maintained in a range of 290 to 300 ° C. And after passing this heat retention area | region, it blows and cools the air speed of 0.1-0.4 m / min with a horizontal blowing type cooling device, and a monofilament processing agent is 0.1-0.5 weight% by a well-known method. Give. A preferred spinning speed is 500 to 1200 m / min.

  In the stretching process, it is necessary to stretch the unstretched monofilament at a preheating temperature of 80 to 130 ° C., so that all of the above-described tensile strength, knot strength, and hook strength suitable for screen wrinkles, particularly high mesh screen wrinkles, can be obtained. At the same time, a satisfactory monofilament can be obtained.

  That is, when the preheating temperature is less than 80 ° C., the film cannot be sufficiently stretched, so that it is difficult to obtain the high strength and high modulus necessary for the high mesh screen. On the other hand, when the preheating temperature exceeds 130 ° C., the knot strength and the catching strength are insufficient, and this is caused by making the preheating temperature higher than 130 ° C. in view of stretching the core component polyethylene naphthalate. In the unstretched monofilament taken at a spinning speed of less than 1500 m / min, although not less than Tg is preferable, crystallization of the polyethylene terephthalate of the sheath component proceeds at the preheating temperature, and fine crystals are formed during preheating. It is presumed that density non-uniformity occurs and the structure becomes very brittle.

Furthermore, from the above viewpoint, the unstretched monofilament is preheated by being wound around a heating roller having a preheating temperature of 80 to 130 ° C., and is further heat-set by passing through a non-contact heater at 120 to 220 ° C., and is wound through the roller. It is necessary to draw and heat set between these rollers at a draw ratio of 3.6 to 4.5 times and wind up at a draw speed of 400 to 1000 m / min. The stretching may be single-stage stretching as described above or multi-stage stretching. Further, the undrawn yarn may be drawn continuously without being wound once.

Hereinafter, the present invention will be described more specifically with reference to examples. In addition, the measurement of each characteristic value in an Example followed the following.
(1) Tensile strength and elongation at break The strength and elongation at break when measured by a tensile tester in an atmosphere of 20 ° C. and 65% RH under the conditions of a sample length of 20 cm and a speed of 20 cm / min. The number of measurements was 10, and the average was obtained.
(2) Weaving property A mesh woven fabric is woven using a sulzer loom at a rotation speed of the loom of 250 rpm. While observing the mesh fabric, weaving was interrupted when monofilament breakage was observed, and the weaving length at that time was measured.
Good weaving evaluation: Weaving of 250 m or more is possible: Slightly poor: 100 m or more but less than 250 m Weaving is poor: 100 m or more is not possible

[Example 1]
Polyethylene terephthalate having an intrinsic viscosity of 0.630 and polyethylene naphthalate having an intrinsic viscosity of 0.620 were melted at 290 ° C. and 315 ° C., respectively, and a core-sheath type composite spinneret (the discharge hole has a diameter of 0.4 mm × a land length of 0.2 mm). 8 mm, 4 holes), the die surface temperature was 300 ° C., and the core component / sheath component = 70/30 composite ratio (weight ratio) was discharged at a total discharge rate of 17.5 g / min. At this time, 13 cm below the spinneret was kept warm. The discharged yarn is cooled by using a horizontal blowing type cooling device, blowing cooling air at a temperature of 25 ° C. and a wind speed of 0.2 m / min, and taking up the solidified yarn at a speed of 800 m / min. After applying 0.25% of the treatment agent, it was separated and wound up. The wound unstretched monofilament was preheated with a heating roller at 90 ° C., passed through a non-contact heater at 180 ° C. and heat-set, and wound through the stretching roller to obtain a monofilament. At this time, the draw ratio (DR) was 4.2 times, and the draw speed was 500 m / min. The results are shown in Table 1.

[Example 2]
A monofilament was obtained in the same manner as in Example 1 except that the core component / sheath component was 80/20 (ratio by weight) and the preheating temperature was 100 ° C. The results are shown in Table 1.

[Example 3]
A monofilament was obtained in the same manner as in Example 1 except that the composite ratio (weight ratio) of core component / sheath component = 50/50 was used. The results are shown in Table 1.

[Comparative Example 1]
A monofilament was obtained in the same manner as in Example 1 except that the preheating temperature was 140 ° C., the set temperature was 150 ° C., and the draw ratio (DR) was 4.4 times. The results are shown in Table 1.

[Comparative Example 2]
A monofilament was obtained in the same manner as in Example 1 except that the composite ratio (weight ratio) of core component / sheath component = 80/20 was set, and the draw ratio (DR) was 4.6 times. The results are shown in Table 1.

[Comparative Example 3]
A monofilament was obtained in the same manner as in Example 1 except that the composite ratio (weight ratio) of core component / sheath component = 50/50 was used and the draw ratio (DR) was 3.5 times. The results are shown in Table 1.

[Comparative Example 4]
A monofilament was obtained in the same manner as in Example 1 except that the composite ratio (weight ratio) of core component / sheath component = 30/70 was used. The results are shown in Table 1.

In Examples 1 to 3, a monofilament having high tensile strength, knot strength and hook strength was obtained, and there was no occurrence of yarn breakage or fluffing, good weaving property, and high mesh screen excellent in durability and printing accuracy. It was also suitable for firewood applications.
In Comparative Examples 1 and 2, monofilaments with high strength were obtained, but the knot strength and hook strength were very low and the weaving property was poor. In addition, yarn breakage frequently occurred during weaving.
In Comparative Example 3, a monofilament with high knot strength and hook strength was obtained, but because the tensile strength was low, it was not suitable for weaving under high tension, and yarn breakage during weaving was not seen. However, the mesh fabric obtained was not uniform.
In Comparative Example 4, a monofilament having sufficient strength could not be obtained, which was not satisfactory for high mesh screen use.

  ADVANTAGE OF THE INVENTION According to this invention, although it is high intensity | strength and high modulus, it can provide the monofilament for screen wrinkles strong also in bending. For this reason, the monofilament has a stable weaving property under high tension, and is excellent in durability and printing accuracy. Therefore, the monofilament can be suitably used for a high mesh screen reed that requires high quality.

Claims (2)

A core-sheath type composite monofilament in which a polyester mainly composed of polyethylene naphthalate is a core component and a polyester mainly composed of polyethylene terephthalate is a sheath component, and the core-sheath weight ratio is a core component / sheath component = 80 / 20- 40/60, the core-sheath weight ratio was combined as a core component / sheath component = 80 / 20-40 / 60, and the unstretched monofilament melted and discharged from the composite spinneret was wound at a spinning speed of 500-1500 m / min. This is obtained by preheating at a preheating temperature of 80 to 130 ° C., passing through a non-contact heater at 120 to 220 ° C., and stretching and heat setting at a stretching ratio of 3.6 to 4.5 times. ) To (4) are satisfied at the same time.
(1) Nodule strength ≧ 3.0 cN / dtex
(2) Hook strength ≧ 2.5 cN / dtex
(3) Tensile strength ≧ 4.5 cN / dtex
(4) Elongation at break ≧ 10% Polyester with polyethylene naphthalate as the main component is the core component, polyester with polyethylene terephthalate as the main component is the sheath component, and the weight ratio of core / sheath is core component / sheath component = 80/20 to 40/60. The monofilament melted and discharged from the die is wound at a spinning speed of 500 to 1500 m / min, preheated at a preheating temperature of 80 to 130 ° C. , and further passed through a non-contact heater at 120 to 220 ° C. to draw ratio of 3.6 to A method for producing a polyester monofilament for screen wrinkles, characterized by stretching and heat setting at 4.5 times .