JPH055209A - High-modulus conjugate monofilament for screen plain gauge - Google Patents

Abstract

PURPOSE:To provide the title monofilament having specific physical properties, excellent in mechanical strength and stress relaxation characteristics etc., also causing no scumming during the weaving process, made up of polyethylene terephthalate as sheath component and polyethylene naphthalate as core component. CONSTITUTION:The objective monofilament >=160g/d in elastic modulus and >=5000sec in stress relaxation time, made up of (A) as sheath component, polyethylene terephthalate or a modified polyester predominant in polyethylene terephthalate and (B) as core component, polyethylene-2,6-naphthalate. For the stress relaxation time to be attained at >=5000sec., it is recommended that the monofilament tension be set at >=0.4g/d in the cold stretching treatment after hot drawing; for this purpose, the cold stretch ratio is recommended to set at >=1.01.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high elastic modulus composite monofilament for screen gauze which is excellent in weaving property and stress relaxation property and suitable for high precision screen printing.

[0002]

2. Description of the Related Art In recent years, not only printing of various electronic circuits,
Screen printing has also been used in the field of high-level printing, and high precision is required. As the screen gauze, polyester screen gauze mainly composed of polyethylene terephthalate and screen gauze using stainless fiber are known. However, the elastic modulus of the monofilament mainly composed of polyethylene terephthalate was at most about 140 g / d, and further improvement was difficult. In addition, although the stainless fiber has an extremely high elastic modulus, it is likely to be accompanied by plastic deformation, requires careful handling when used as a screen gauze, and is expensive. Regarding the increase in the elastic modulus of the polyester screen gauze, Japanese Patent Laid-Open No. 3-45741 discloses a screen gauze made of polyethylene naphthalate, and a screen gauze having a high elastic modulus and less tarmi at the time of printing is presented. .. Further, JP-A-2-289120 discloses a core-sheath type composite monofilament made of polyester for a screen gauze, and presents a monofilament having high strength and excellent weavability. However, in the invention of JP-A-3-45741, although physical properties such as higher strength and higher elastic modulus can be obtained as compared with conventional polyethylene terephthalate, scum frequently occurs during weaving, and the generated scum is woven into the final product. The product is prone to defects. In particular, weaving a high-mesh screen gauze having a size of more than 310 mesh was extremely difficult. In addition, 38
Since it easily reflects ultraviolet rays of a short wavelength of 0 nm or less, there is a problem that the masking resin is hardened by irradiation with ultraviolet rays, so that halation tends to be exceeded in the plate making process, and it is difficult to obtain a high-performance printing screen gauze that requires sharp contours. Met.

Further, in the invention of Japanese Patent Application Laid-Open No. 2-289120, the use of polyethylene-2,6-naphthalate as a core component is disclosed, and although it is effective in suppressing scum and preventing halation, it is merely that. It has been found that there is a problem that the stress relaxation time of the screen gauze stretched on the gauze frame with a high tension is large, and that it takes a long time to stabilize. This is because polyethylene-2,6-naphthalate is composed of rigid molecular chains as compared with polyethylene terephthalate, so there is less entanglement between the molecular chains, and tension such as creep and stress relaxation due to sliding of the molecular chains. This is because the dimensional changes below tend to occur.

[0004]

DISCLOSURE OF THE INVENTION The present invention improves the drawbacks of the prior art and is excellent in mechanical properties such as strength, elastic modulus and stress relaxation, and has less scum and scraping in the weaving process. The purpose is to provide a monofilament.

[0005]

DISCLOSURE OF THE INVENTION The inventors of the present invention have a specific drawing in a core-sheath composite monofilament using polyethylene-2,6-naphthalate as a core and polyethylene terephthalate or a modified polyester mainly containing polyethylene terephthalate as a sheath. It has been found that the treatment makes it possible to reduce scum generation during weaving and to provide excellent stress relaxation characteristics, which is suitable as a screen gauze. That is, the present invention is a core-sheath composite monofilament in which the sheath component is polyethylene terephthalate or a modified polyester mainly composed of polyethylene terephthalate, and the core component is polyethylene-2,6-naphthalate, and the elastic modulus is 160 g / d or more, and A high elastic modulus composite monofilament for screen gauze, characterized in that the stress relaxation time is 5000 seconds or more.

In the present invention, polyethylene-2,6-naphthalate having a high molecular chain rigidity and an excellent elastic modulus is used for the purpose of obtaining a monofilament having a high elastic modulus, and the elastic modulus of the monofilament is 160 g / d or more. Can be achieved. The elastic modulus is more preferably 180 g /
It is d or more. In screen printing, generally, in order to improve the dimensional accuracy of a print pattern, a method of increasing the tension of the cloth and reducing the distance between the screen cloth and the object to be printed, that is, off-contact is adopted. The upper limit of the tension of the gauze is determined by the elastic modulus and the elastic limit strength of the gauze. The off-contact of the current polyester screen gauze is usually about 2 mm, and it is required to further reduce the off-contact for more precise printing.

The present inventors have made it possible to increase the modulus of elasticity of a monofilament made of an organic compound so that the off-contact is 2 to 0.5.
As a result of earnest studies for realizing the mm, it was found that the off-contact of 2 mm or less can be sufficiently realized by setting the elastic modulus of the monofilament to 160 g / d or more. Further, by setting the elastic modulus of the monofilament to 180 g / d or more, the off contact of 1 mm or less can be realized. However, it has been found that the naphthalate-based polyester has the following drawbacks. That is, the fibril resistance is poor, and scum tends to occur during weaving. UV rays are easily reflected, and halation is likely to occur when the masking resin is cured by UV rays. Filaments that have only been subjected to a high degree of drawing heat treatment tend to cause stress relaxation.

In the present invention, the above-mentioned drawbacks are solved by adopting a core-sheath composite, and further drawbacks are obtained by subjecting a stress relaxation time defined in the text to 5000 seconds or more by performing a specific stretching treatment. It has been resolved. That is, compared with polyethylene-2,6-naphthalate, polyethylene terephthalate has high toughness and scum hardly occurs even when stretched to a high degree. Since the scum during weaving is generated by friction with the lure and the like, the occurrence of scum can be effectively suppressed by disposing polyester having high toughness in the sheath. Further, by using a modified polyester having a low glass transition temperature, more flexibility and low crystallinity, the effect becomes more remarkable. Monomers suitable for copolymerization for such a purpose are monomers or low molecular weight polymers that enhance the flexibility of the molecular chain and are less likely to cause steric hindrance. Specifically, dicarboxylic acids such as isophthalic acid, adipic acid, sebacic acid and dimer acid, low molecular weight glycols such as diethylene glycol, butanediol and neopentyl glycol, molecular weight 600 to 150.
Examples thereof include polyalkylene glycols such as polyethylene glycol and polytetramethylene glycol of 0. The copolymerization amount cannot be unconditionally determined depending on the selected copolymer, but it is preferable to determine it so that the glass transition temperature is 35 ° C. to 73 ° C. as an index of flexibility. Further, in order to improve the toughness of the sheath component, it is preferable that the modified polyester is a high viscosity polymer having an intrinsic viscosity [η] of 0.55 or more. In the present invention, both the core and the sheath are made of polyester, and therefore peeling is less likely to occur at the composite interface, so that the thickness of the sheath component can be reduced to about 0.5 μm. A thinner sheath makes it easier to obtain a high-modulus monofilament, but a thicker sheath is preferable from the viewpoint of preventing scum. From this, the thickness of the sheath is 0.5 μm or more, preferably 1 to 5 μm.

Further, according to the present invention, by using the core-sheath composite structure, it is possible to solve the above-mentioned drawback, that is, the problem of halation upon irradiation with ultraviolet rays. Polyethylene-2,6-naphthalate has a property of easily reflecting ultraviolet rays having a wavelength of 380 nm or less. Moreover, since the glass transition temperature is as high as 112 ° C., the dyeability is inferior and it is difficult to introduce an ultraviolet absorber by dyeing and finishing. Therefore, there is a problem that halation is likely to occur when the ultraviolet curable masking resin pattern is baked on the screen mesh. On the other hand, polyethylene terephthalate-based polyester absorbs ultraviolet rays of 320 nm or less. Therefore,
By arranging it as a sheath component on the surface layer, reflection of ultraviolet rays can be suppressed. Furthermore, the surface layer can be effectively dyed with an ultraviolet absorber, and the halation defect can be eliminated. The core component of the present invention is intended for polyethylene-2,6-naphthalate, but a small proportion of the third component other than the naphthalene-2,6-dicarboxylic acid component and / or the ethylene glycol component (usually 10 mol% or less). It may be a copolymerized and / or mixed polyester. The intrinsic viscosity [η] of the core component polyethylene-2,6-naphthalate is preferably within the range of 0.5 to 1.0. When the intrinsic viscosity is less than 0.5, the molecular chain length is short, strength is difficult to develop, and it becomes difficult to obtain a stress relaxation time of 5000 seconds or more as described below. On the other hand, if it exceeds 1.0, the melt viscosity of the polymer becomes extremely high, so that the spinning temperature at the time of spinning needs to be high, and polyethylene terephthalate as a sheath component or a modified polyester mainly composed of polyethylene terephthalate is significantly deteriorated by heat. This is not preferable because not only the yarn breakage during spinning increases but also the scum preventing effect during weaving decreases.

Thus, in the present invention, polyethylene-
By using 2,6-naphthalate as a core and a polyethylene terephthalate polymer as a sheath, a composite monofilament having high strength and high elastic modulus can be obtained. However, in the composite monofilament simply subjected to the stretching heat treatment, the above-mentioned drawback, that is, stress relaxation is likely to occur, and particularly, until the printing step after stretching on the gauze frame,
It was also found that there was a problem with dimensional stability during repeated printing. Here, the stress relaxation means a phenomenon in which the stress generated in the fiber decreases with time when the fiber is held under tension in a constant length state. The stress relaxation time λ (second) is defined as the time until the initial stress decreases to 1 / e (e is the base of natural logarithm).

That is, F = F ₀ e ^{− (t / λ)}
However, F ₀ = initial stress (2 g / d) F = stress after t seconds (g / d) t = measurement time (1200 seconds) λ = stress relaxation time (sec) e = base of natural logarithm Is.

Specific measurement conditions are shown in the examples, but can be determined by using a Tensilon type tensile tester. The polyethylene-2,6-naphthalate fiber has a shorter stress relaxation time than the polyethylene terephthalate fiber. Since it is composed of rigid molecular chains, there is little entanglement between the molecular chains. This can be judged from the fact that slippage of the molecular chain is likely to occur in the step of heating and winding the undrawn yarn and winding, and the drawing tension is as low as 1/2 or less of that of polyethylene terephthalate fiber. The present inventors have conducted studies to make the stress relaxation time of the polyethylene-2,6-naphthalate fiber to be 5000 seconds or more, which is comparable to that of polyethylene terephthalate fiber, and as a result, heat stretching is followed by cold stretching. It was found that the stress relaxation time is significantly increased by the above, and it was found that the above stress relaxation time is further greatly increased by using a core-sheath composite in which polyethylene terephthalate-based polyester is arranged in the sheath. It is a thing. In the present invention, the stress relaxation time of 5000 seconds or more can be realized by specifically setting the yarn tension in the cold stretch treatment after hot drawing to 0.4 g / d or more. Such a yarn tension has a cold stretch ratio of 1.
It is obtained by setting the ratio to be 01 times or more. The stress relaxation time of the monofilament corresponds well to the elongation of the gauze when the screen gauze is stretched on the gauze frame, and the tension relaxation after the gauze is stretched. In order to obtain a screen plate for high precision printing, The stress relaxation time of the monofilament must be 5000 seconds or longer. More preferably 60
It is better to set it to 00 seconds or more.

Next, an example of the method for producing the monofilament of the present invention will be described with reference to FIG. Intrinsic viscosity [η] is 0.5
A polyethylene-2,6-naphthalate of 1.0 to 1.0 is used as a core component polymer, and polyethylene terephthalate or a modified polyester having polyethylene terephthalate as a main component is prepared as a sheath component polymer. Spin at 295 ℃ ~ 310 ℃, 60
The core-sheath type composite undrawn yarn 1 is wound at 0 to 1500 m / min. Although the spinneret may have one hole, it is usually 2 to 8 holes, and is separated and wound up when winding the undrawn yarn, but it may be formed into drawn yarn and then separated, and further drawn and false twisted. A monofilament may be obtained by subjecting the fiber to the subsequent separation. This undrawn yarn 1 is drawn through the feed roller 2 between the first heating roller 3 and the second heating roller 4 at 130 to 150 ° C. to a predetermined ratio, and subsequently 90 ° C. or less, preferably at room temperature. A stretching process (cold stretching in the present invention) is performed with the draw roller 5. The monofilament of the present invention can be obtained by setting the yarn tension in this stretching treatment to 0.4 g / d (d is the denier of the drawn yarn) or more and setting the breaking elongation of the obtained drawn yarn to 20% or less. Alternatively, the undrawn yarn may be directly drawn and wound at 3000 to 5000 m / min without being wound once. Even in this case, 90 ° C. corresponding to the draw roller 5 described above.
Hereafter, the monofilament of the present invention can be obtained by subjecting it to a stretching treatment preferably through a roller at room temperature and winding it.

[0014]

EXAMPLES The effects of the present invention will be described below with reference to examples. The measurement conditions for each physical property in the examples are as follows. Measurement of stress relaxation time λ (second) of monofilament. That is, using a Tensilon type tensile tester, a tensile speed of 10 mm / min, a full scale of 100 g, and a chart speed of 1
0 cm / min, sample length 20 cm, temperature and humidity 20 ± 1 ° C, 65
Performed at ± 3% RH. Stress relaxation time λ is 2g
/ D (F ₀ ) is reached, elongation is stopped, stress F after stress relaxation for 1200 seconds (t seconds) is read from this elongation stop time, and λ (second) = 1200 / ln (F ₀ /
It is a value obtained by calculation from F). The fineness d used for the stress calculation is the fineness of the sample used for the measurement.

Measurement of Elastic Modulus A sample was pulled at a pulling speed of 20 using a Tensilon type tensile tester.
cm / min, the value calculated from the straight line portion up to the 1% elongation point of the stress strain curve measured at a sample length of 20 cm, and is the average value of elastic modulus obtained by repeatedly measuring 10 times at an arbitrary portion. ..

Examples 1 to 6 and Comparative Examples 1 to 7 Polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.62 was used as a core component polymer, and polyethylene terephthalate having an intrinsic viscosity of 0.80 and a molecular weight of about 1000 when polyethylene terephthalate were polymerized. The modified polyester having an intrinsic viscosity of 0.75 obtained by adding 8.0% by weight of polyethylene glycol is prepared as a sheath component polymer, and the composite ratio of core: sheath is 80:20 (using a known composite spinning machine. Volume ratio),
Melt spinning was performed at a spinning temperature of 305 ° C. with a spinneret having four holes, a hole shape of 0.5 mm, and a hole length of 0.6 mm, and 0.25% owf of a conventionally known oil agent for fibers was applied, and a winding speed was 1000.
It was wound at m / min to obtain a concentric core / sheath composite unstretched monofilament. On the other hand, an unstretched polyethylene-2,6-naphthalate monofilament was obtained from the above core component polymer using an ordinary single component spinning machine and a single component pack under the same conditions as above. The obtained unstretched monofilament was stretched at a stretching speed of 800 m / min using the stretching device shown in FIG.
The heating roller 140 ° C., the second heating roller 150 ° C., and the draw roller were not heated, and the draw ratio and cold stretch tension were changed to obtain the monofilaments shown in Table 1. The monofilament fineness of each of the obtained monofilaments was 12 denier. However, in Comparative Example 3, it was 13.5 denier. In the stretching conditions in Table 1, r ₁ is the stretching ratio between the first heating roller and the second heating roller, r ₂ is the stretching ratio between the second heating roller and the draw roller, and the cold stretching tension is the second heating roller. It is the tension due to the draw ratio r ₂ between the draw rollers and is the value obtained by dividing the measured yarn tension by the denier of the drawn monofilament. The composite monofilaments Examples 1 to 6 of the present invention shown in Table 1 had a high elastic modulus, a stress relaxation time of 5000 seconds or more, and had excellent physical properties as a monofilament for screen gauze. On the other hand, even a composite monofilament is likely to cause stress relaxation when r ₂ is small and cold stretch tension is low as in Comparative Examples 1 and ₂ . Moreover, even if it is a composite monofilament,
When r ₁ is small as in Comparative Example 3, the elastic modulus is low, and there is a problem that stress relaxation is likely to occur. As comparative examples of the present invention, single monofilaments of polyethylene-2,6-naphthalate are shown in Comparative Examples 4 to 7. The single monofilament had a higher elastic modulus than the composite monofilament but a low cold stretch tension and a poor stress relaxation property.

Next, the monofilament of the present invention and the monofilament of the comparative example were woven by a conventional method into a 305 mesh screen gauze by a conventional method. As a result, Example 1 of the composite monofilament of the present invention
For Nos. 6 to 6, the weaving property was good, with no warp scraping due to warp rubbing of the feather. Also in Comparative Examples 1 to 3, warp yarn scraping was good. On the other hand, for Comparative Examples 4 to 7, there was warp warping from the initial stage of weaving,
Moreover, the scraped material was woven into the screen, which was not suitable for use in precision screen printing.

[0018]

[Table 1]

[0019]

INDUSTRIAL APPLICABILITY The composite monofilament of the present invention, despite its high strength and high elastic modulus, is less likely to cause scum due to abrasion during weaving and can easily weave a high mesh screen gauze. Further, since the stress relaxation characteristic can be made excellent, the off contact at the time of screen printing can be 2 mm or less. In addition, there is little halation obstacle when the photosensitive emulsion is exposed and baked by ultraviolet irradiation. Further, a screen gauze excellent in abrasion resistance against squeegee abrasion can be obtained, and it is a monofilament suitable for a screen gauze for high precision printing.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a stretching device for obtaining a monofilament of the present invention.

[Explanation of symbols]

 1: undrawn yarn 2: feed roller 3: first heating roller 4: second heating roller 5: draw roller 6: drawn yarn

Claims (1)

Claims: 1. A core-sheath composite monofilament in which the sheath component is polyethylene terephthalate or a modified polyester mainly composed of polyethylene terephthalate, and the core component is polyethylene-2,6-naphthalate. A high elastic modulus composite monofilament for screen gauze, which has a stress relaxation time of 5000 seconds or more and 160 g / d or more.