JPWO2019146620A1 - Mesh woven fabric made of liquid crystal polyester fiber - Google Patents

Abstract

A mesh woven fabric made of liquid crystal polyester fiber, characterized in that the number of meshes is 350 lines / inch or more and the gauze thickness is 25 μm or less. A mesh fabric made of liquid crystal polyester fiber with a large number of meshes and a low thickness, which has a small permeation volume of the paste when made into a screen plate, and is suitable for thin film printing. It is provided with high strength and excellent chemical resistance that is hard to be plastically deformed while preventing fibrillation and deterioration of wear resistance.

Description

Since the present invention is made of liquid crystal polyester fiber, it has high strength, is not easily plastically deformed, has excellent chemical resistance, has a large number of meshes, and has a low gauze thickness, so that the permeation volume of the paste is small when it is used as a screen plate, and it is a thin film. It relates to a mesh fabric suitable for printing.

Liquid crystal polyester fiber is the only super fiber produced by melt spinning among super fibers represented by its characteristics of high strength, high elastic modulus, and chemical resistance, and has excellent fiber roundness, making it a monofilament for mesh fabrics. Is suitable. On the other hand, the liquid crystal polyester fiber is inferior in abrasion resistance, and in particular, fibrillation is likely to occur in the weaving process. Therefore, improvement in abrasion resistance is desired in order to form a mesh fabric.

Regarding the improvement of wear resistance of the liquid crystal polyester fiber, the temperature of the heat absorption peak temperature (Tm1) + 10 ° C. or higher observed when the liquid crystal polyester fiber is measured under the heating condition of 50 ° C. to 20 ° C./min in the differential calorimetry. That is, a technique for heat treatment at a melting point of + 10 ° C. or higher has been proposed (see Patent Documents 1 and 2). Abrasion resistance is improved by this technology, and weavable liquid crystal polyester fibers are obtained. However, for mesh fabrics for filters, screen printing, etc., the weaving density is increased (high mesh) to improve performance. In addition, for screen printing mesh fabrics related to electronic circuits, a reduction in transmission volume is required in order to reduce the amount of conductive paste used.

Here, the transmission volume of the mesh will be described. The transmission volume (cc / m ² ) is an index showing the volume of the opening (transmission portion) in the mesh woven fabric 1 m ² . It is known that the transmission volume has a positive correlation with the amount of paste held in the mesh in screen printing, and the smaller the transmission volume, the smaller the amount of paste used, and the thinner the printing film thickness can be printed. This permeation volume can be calculated by the following formula using the thickness (μm).
Permeation volume = OPA / 100 x thickness

Here, OPA (%) is the opening area. The opening area is an index showing the area ratio of the opening of the mesh, and is calculated by the following formula.
OPA = OP ² / (OP + fiber diameter) ² x 100

Here, OP (μm) is the opening and represents the distance between the fibers in the mesh fabric, that is, the length of the side of the opening. OP (μm) can be calculated by the following formula from the number of meshes (fibers / inch) and the fiber diameter (μm), which is the number of fibers per 2.54 cm (= 1 inch) width of the mesh fabric.
OP = 25400 / number of meshes-fiber diameter

As can be seen from the above relationship, it is necessary to reduce the OPA and the thickness of the gauze in order to reduce the permeation volume, and it is effective to reduce the OP and increase the fiber diameter in order to reduce the OPA. Further, in order to reduce the OP, it is effective to increase the number of meshes and increase the fiber diameter.

However, when the fiber diameter is too large, there is a problem that the height of the intersection of the fibers in the mesh woven fabric is related to the gauze thickness, so that the gauze thickness becomes large and the permeation volume becomes large. Furthermore, in screen printing, the paste does not pass through the fiber part of the mesh, but the paste wraps around behind the fiber part and leveling with the surface tension of the paste after printing makes the film thickness uniform. If is too large, there is a problem that the wraparound of the paste becomes insufficient and uneven film thickness occurs. From these facts, a mesh having a large number of meshes and a small gauze thickness is desired for reducing the transmission volume.

To solve this problem, a thin film printing screen using polyarylate, which has almost the same meaning as liquid crystal polyester, as a part of the fiber raw material has been proposed (Patent Document 3). In this technology, a mesh woven fabric is obtained by using a core-sheath composite fiber with liquid crystal polyester as the core component, thermoplastic polymer as the sea, and liquid crystal polyester as the sea island blend polymer as the sheath component, and this is calendar-processed. I am getting a screen with a small thickness.

As another technique, a technique of a mesh woven fabric made of a melt anisotropic (liquid crystal) aromatic polyester fiber having an ultrafine diameter has been proposed (Patent Document 4). In this technique, a mesh woven fabric is woven using a core-sheath composite fiber in which the core component is a melt anisotropic (liquid crystal) aromatic polyester and the sheath component is a polyolefin polymer, and then the sheath component of the composite fiber is dissolved in a solvent. By allowing it to be extracted and removed, a mesh woven fabric having an ultrafine diameter is obtained.

Japanese Unexamined Patent Publication No. 2008-240230 (pages 18 to 19) JP-A-2010-248681 (page 8) Japanese Unexamined Patent Publication No. 2008-74073 (page 2) Japanese Unexamined Patent Publication No. 2001-140141 (page 2)

However, in the technique of Patent Document 3, the gauze thickness can be reduced when the number of meshes is small, and when the number of meshes is large, the gauze thickness cannot be reduced (Comparative Example 5, the gauze thickness is 41 μm in the number of meshes 380). ). Since this contains a component other than liquid crystal polyester as the fiber, a high load is required when crushing the fiber, and it is considered that the gauze thickness cannot be sufficiently reduced in a high mesh having a large number of intersections. In the technique of Patent Document 4, the OPA (opening area) described as the aperture ratio is large, the permeation volume cannot be reduced, and the fiber diameter after solvent extraction is 13 μm in length and 14 μm in width in the examples. The thickness of the gauze, which is related to the height of the intersection of the fibers, has not been reduced.

The subject of the present invention is that since it is made of liquid crystal polyester fiber, it has high strength, is not easily plastically deformed, has excellent chemical resistance, has a large number of meshes, and has a low gauze thickness, so that the permeation volume of the paste is large when it is used as a screen plate. It is an object of the present invention to provide a mesh fabric which is small and suitable for thin film printing.

The above-mentioned problem of the present invention is achieved by the following means.
A mesh woven fabric made of liquid crystal polyester fibers having a mesh number of 350 fibers / 2.54 cm (= 1 inch) or more and a gauze thickness of 25 μm or less.

Since the mesh woven fabric of the present invention is made of liquid crystal polyester fiber, it has high strength, is not easily plastically deformed, and has excellent chemical resistance. In addition, since the number of meshes is large and the thickness is low, the transmission volume of the paste is small when a screen plate is used, which is suitable for thin film printing.

Hereinafter, the mesh woven fabric made of the liquid crystal polyester fiber of the present invention will be described in detail.
The liquid crystal polyester fiber used in the mesh woven fabric of the present invention is substantially composed of a single component of liquid crystal polyester. Substantially means a fiber composed of a single component rather than a composite fiber with another component or a sea island fiber. However, the addition of other polymers or various additives of about 5% by weight or less within a range that does not impair the characteristics of the liquid crystal polyester as described later may be added.

The liquid crystal polyester used in the present invention is a polyester capable of forming an anisotropic molten phase (liquid crystal property) when melted. This characteristic can be confirmed, for example, by placing a sample made of liquid crystal polyester on a hot stage, heating the sample in a nitrogen atmosphere, and observing the transmitted light of the sample under polarized light.

Examples of the liquid crystal polyester used in the present invention include a polymer of aromatic oxycarboxylic acid (a), a polymer of aromatic dicarboxylic acid (b) and aromatic diol, an aliphatic diol, and a polymer of aromatic oxycarboxylic acid. Examples thereof include a copolymer (c) of (a) and an aromatic dicarboxylic acid (b), but a total aromatic polyester that does not use an aliphatic diol is preferable for high strength, high elasticity, and high heat resistance. .. Here, examples of the aromatic oxycarboxylic acid include hydroxybenzoic acid, hydroxynaphthoic acid and the like, or alkyl, alkoxy and halogen substituents of the aromatic oxycarboxylic acid. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, naphthalenedicarboxylic acid, diphenyletherdicarboxylic acid, diphenoxyetanedicarboxylic acid, diphenylethanedicarboxylic acid and the like, or alkyl, alkoxy, etc. of the aromatic dicarboxylic acid. Examples include halogen substituents. Further, examples of the aromatic diol include hydroquinone, resorcin, dioxydiphenyl, naphthalene diol and the like, or alkyl, alkoxy and halogen substituents of the above aromatic diol, and examples of the aliphatic diol include ethylene glycol and propylene glycol. Butanediol, neopentyl glycol and the like can be mentioned.

The liquid crystal polyester used in the present invention is a copolymer of a p-hydroxybenzoic acid component, a 4,4'-dihydroxybiphenyl component, a hydroquinone component, a terephthalic acid component and / or an isophthalic acid component, and a p-hydroxybenzoic acid component. Copolymerization of acid component and 6-hydroxy2-naphthoic acid component, copolymerization of p-hydroxybenzoic acid component, 6-hydroxy2-naphthoic acid component, hydroquinone component and terephthalic acid component, etc. Is excellent in high strength, high elasticity, and chemical resistance, and is mentioned as a preferable example.

The liquid crystal polyester used in the present invention is particularly preferably a liquid crystal polyester composed of the following structural units (I), (II), (III), (IV) and (V). In the present specification, the structural unit refers to a unit that can form a repeating structure in the main chain of a polymer.

With this combination, the molecular chain has appropriate crystallinity and non-linearity, so that the strength and elastic modulus of the fiber can be increased, and the abrasion resistance can be improved, so that it is suitable for high mesh woven fabrics. Since the fibers are easily crushed in the lateral direction (the direction perpendicular to the fiber axis), the thickness of the gauze can be reduced.

Furthermore, it is important to combine components consisting of diols that are not bulky and have high linearity, such as structural units (II) and (III), and by combining these components, the molecular chains are disordered in the fiber. It has a small structure and can maintain the interaction in the direction perpendicular to the fiber axis without excessively increasing crystallinity. As a result, in addition to obtaining high strength and elastic modulus, particularly excellent wear resistance can be obtained by performing high-temperature heat treatment after solid-phase polymerization.

The structural unit (I) described above is preferably 40 to 85 mol%, more preferably 65 to 80 mol%, and further preferably 68 to 68 to the total of the structural units (I), (II) and (III). It is 75 mol%. With such a range, the crystallinity can be set to an appropriate range, and high strength and elastic modulus can be obtained.

The structural unit (II) is preferably 60 to 90 mol%, more preferably 60 to 80 mol%, and further preferably 65 to 75 mol% with respect to the total of the structural units (II) and (III). Within such a range, the crystallinity is not excessively increased and the interaction in the vertical direction of the fiber axis can be maintained. Therefore, the abrasion resistance can be improved, which is suitable for high mesh woven fabrics, and the fibers are further arranged in the lateral direction. Since it is easy to crush in the (vertical direction of the fiber axis), the thickness of the gauze can be reduced.

The structural unit (IV) is preferably 40 to 95 mol%, more preferably 50 to 90 mol%, still more preferably 60 to 85 mol% with respect to the total of the structural units (IV) and (V). In such a range, the linearity of the polymer is appropriately disturbed, so that the abrasion resistance can be improved, which is suitable for high mesh woven fabrics, and the fibers are crushed in the lateral direction (the direction perpendicular to the fiber axis). Because it is easy, the thickness of the gauze can be reduced.

The preferable range of each structural unit of the liquid crystal polyester used in the present invention is as follows. The liquid crystal polyester fiber used in the present invention can be preferably obtained by adjusting the composition so as to satisfy the above conditions within this range.
Structural unit (I) 45-65 mol%
Structural unit (II) 12-18 mol%
Structural unit (III) 3-10 mol%
Structural unit (IV) 5-20 mol%
Structural unit (V) 2 to 15 mol%

In addition to the above structural units, the liquid crystal polyester used in the present invention includes aromatic dicarboxylic acids such as 3,3'-diphenyldicarboxylic acid and 2,2'-diphenyldicarboxylic acid, adipic acid, azelaic acid, sebacic acid, and dodecandione. Aliphatic dicarboxylic acids such as acids, alicyclic dicarboxylic acids such as hexahydroterephthalic acid (1,4-cyclohexanedicarboxylic acid), chlorohydroquinone, 4,4'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfide, Aromatic diols such as 4,4'-dihydroxybenzophenone and p-aminophenol may be copolymerized in a range of about 5 mol% or less that does not impair the effects of the present invention.

Further, in the range of about 5% by weight or less that does not impair the effect of the present invention, polyester, vinyl polymers such as polyolefin and polystyrene, polycarbonate, polyamide, polyimide, polyphenylene sulfide, polyphenylene oxide, polysulfone, aromatic polyketone, aliphatic polyketone. , Semi-aromatic polyesteramide, polyether ether ketone, fluororesin and other polymers may be added, polyphenylene sulfide, polyether ether ketone, nylon 6, nylon 66, nylon 46, nylon 6T, nylon 9T, polyethylene terephthalate, Suitable examples include polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycyclohexanedimethanol terephthalate, polyester 99M and the like.

Further, as long as the effects of the present invention are not impaired, various metal oxides, kaolin, silica and other inorganic substances, colorants, matting agents, flame retardants, antioxidants, ultraviolet absorbers, infrared absorbers, crystal nucleating agents , Fluorescent whitening agent, terminal group encapsulant, compatibilizer and other various additives may be contained in a small amount.

The polystyrene-equivalent weight average molecular weight (hereinafter referred to as molecular weight) of the liquid crystal polyester fiber used in the present invention is preferably 250,000 or more and 200,000 or less. By having a high molecular weight of 250,000 or more, it has high strength, elastic modulus, and elongation. The higher the molecular weight, the higher the strength and elastic modulus. Therefore, 300,000 or more is more preferable. The upper limit of the molecular weight is not particularly limited, but the upper limit that can be reached in the present invention is about 2.0 million, and a sufficiently high effect can be obtained at 100,000. The molecular weight referred to in the present specification is a value obtained by the method described in Examples.

The liquid crystal polyester fiber used in the present invention has a peak half-value width of 15 ° C. or more at the endothermic peak (Tm1) observed when measured under a heating condition of 50 ° C. to 20 ° C./min in differential calorimetry. Is preferable. Tm1 in this measurement method represents the melting point of the fiber, and it can be said that the wider the area of the peak shape, that is, the larger the heat of fusion ΔHm1, the higher the crystallinity, and the narrower the half width, the higher the crystal perfection. Liquid crystal polyester is melt-spun and then subjected to solid-state polymerization to increase Tm1, increase ΔHm1, decrease half-price width, and increase crystallinity and crystal completeness to increase fiber strength, elongation, and elasticity. The rate increases and the heat resistance improves. On the other hand, the wear resistance deteriorates, which is considered to be because the structural difference between the crystalline part and the amorphous part becomes remarkable due to the increased integrity of the crystal, and the fracture occurs at the interface. Therefore, in the liquid crystal polyester fiber used in the present invention, the peak half price width is set to the peak half value width of the liquid crystal polyester fiber which is not solid-phase polymerized while maintaining the high Tm1, high strength, elongation, and elasticity, which are the characteristics of the solid-phase polymerized fiber. By increasing the temperature to 15 ° C or higher, the crystallinity is lowered to reduce the structural difference between crystals and non-crystals, which is the starting point of fracture, the fibril structure is disturbed, and the entire fiber is softened to withstand resistance. Abrasion resistance can be increased. The higher the peak half width at Tm1, the higher the wear resistance, and therefore, it is preferably 20 ° C. or higher. Although the upper limit is not particularly limited, the upper limit that can be reached industrially is about 80 ° C., and a sufficiently high effect can be obtained at 50 ° C.

In addition, by increasing the peak half width to 15 ° C. or higher, the crystallinity is lowered, and the entire fiber is softened, so that the load when the fiber is crushed in the lateral direction (the direction perpendicular to the fiber axis) can be reduced. Therefore, it becomes easy to reduce the thickness of the gauze by calendar processing after weaving.

The liquid crystal polyester fiber of the present invention has one endothermic peak, but two or more peaks may be observed depending on the fiber structure such as when solid-phase polymerization is insufficient. In this case, the peak half-value width is the sum of the half-value widths of each peak.

The melting point (Tm1) of the liquid crystal polyester fiber used in the present invention is preferably 290 ° C. or higher, more preferably 300 ° C. or higher, still more preferably 310 ° C. or higher. Having such a high melting point makes the mesh excellent in heat resistance. In order to achieve a high melting point of the fiber, there is a method such as spinning a liquid crystal polyester polymer having a high melting point, but in order to obtain a fiber having particularly high strength and elastic modulus and excellent uniformity in the longitudinal direction. It is preferable to carry out solid-phase polymerization of melt-spun fibers. The upper limit of the melting point is not particularly limited, but the upper limit that can be reached in the present invention is about 400 ° C.

The value of the heat of fusion ΔHm1 of the liquid crystal polyester fiber used in the present invention varies depending on the composition of the constituent unit of the liquid crystal polyester, but is preferably 6.0 J / g or less. When ΔHm1 is lowered to 6.0 J / g or less, the crystallinity is lowered, the fibril structure is disturbed, the entire fiber is softened, and the structural difference between crystals and amorphous which is the starting point of fracture is reduced, so that the resistance is reduced. Since the wear resistance is improved, it is suitable for high meshing, and the load when crushing the fiber in the lateral direction (the direction perpendicular to the fiber axis) can be reduced. The lower the ΔHm1, the better the wear resistance, so 5.0 J / g or less is more preferable. The lower limit of ΔHm1 is not particularly limited, but 0.2 J / g or more is preferable in order to obtain high strength and elastic modulus.

It is surprising that ΔHm1 is as low as 6.0 J / g or less even though the molecular weight is as high as 250,000 or more. Liquid crystal polyesters having a molecular weight of 250,000 or more have extremely high viscosity even when the melting point is exceeded, and do not flow, making melt spinning difficult. Such high molecular weight liquid crystal polyester fibers melt spin low molecular weight liquid crystal polyesters. It is obtained by solid-phase polymerization of this fiber. When the liquid crystal polyester fiber is solid-phase polymerized, the molecular weight is increased, the strength, elongation, elastic modulus, and heat resistance are improved, and at the same time, the crystallinity is also increased and ΔHm1 is increased. When the crystallinity is increased, the strength, elongation, elastic modulus, and heat resistance are further improved, but the structural difference between the crystalline part and the amorphous part becomes remarkable, the interface is easily broken, and the abrasion resistance is lowered. .. On the other hand, the liquid crystal polyester fiber used in the present invention retains high strength, elongation, elastic modulus, and heat resistance by having a high molecular weight, which is one of the characteristics of the solid-phase polymerized fiber, and solid-phase polymerization is performed. Abrasion resistance can be improved by having a low crystallinity, that is, a low ΔHm1 as in the case of a non-liquid crystal polyester fiber. The liquid crystal polyester fiber used in the present invention is suitable for a high-mesh woven fabric and has a high degree of crystallization because the fiber made of only the liquid crystal polyester can be improved in abrasion resistance by reducing the structural change, that is, the degree of crystallization. Since it is low, the load when crushing the fiber in the lateral direction (the direction perpendicular to the fiber axis) can be reduced, so that it is suitable for low gauze thickness.

The Tm2 of the liquid crystal polyester fiber used in the present invention varies depending on the composition, but is preferably 300 ° C. or higher in order to improve heat resistance. Tm2 is the melting peak temperature observed when the fiber is once held at a temperature higher than Tm1 and then cooled and reheated, and is a temperature close to the melting point of the resin itself, which minimizes the influence of the fiber structure. The upper limit of Tm2 is not particularly limited, but the upper limit that can be reached in the present invention is about 400 ° C.

If the ΔHm2 of the liquid crystal polyester fiber used in the present invention is excessively large, the crystallinity of the polymer itself becomes high and it becomes difficult to improve the abrasion resistance. Therefore, 5.0 J / g or less is preferable, and 2.0 J / g or less is more preferable. preferable. ΔHm2 is the amount of heat of fusion observed when the fiber is once held at a temperature higher than Tm1 and then cooled and reheated, and is the amount of heat of crystallinity of the resin itself that minimizes the influence of the fiber structure. It is an index of crystallinity. In the liquid crystal polyester fiber used in the present invention, the endothermic peak at the time of reheating after cooling under the above measurement conditions is one, but two or more peaks may be observed. In this case, ΔHm2 is the sum of ΔHm2 of each peak.

The Tm1, Tm2, Tm1 peak half width, ΔHm1, and ΔHm2 referred to in the present specification are values obtained by the method described in the examples.
The mesh woven fabric of the present invention has 350 meshes / 2.54 cm (= 1 inch) or more and a gauze thickness of 25 μm or less. When the number of meshes is 350 lines / inch or more and the thickness of the gauze is 25 μm or less, the transmission volume of the mesh is small, and when the screen plate is used, the transmission volume of the paste is small, which is suitable for thin film printing.

The number of meshes of the mesh fabric of the present invention is 350 lines / inch or more. That is, since there are 350 or more fibers per 2.54 cm (= 1 inch) width, the opening (OP) becomes small and the transmitted volume becomes small, which is suitable for thin film printing. From this point of view, the larger the number of meshes, the more preferably 380 lines / inch or more. The upper limit of the number of meshes is not particularly limited, but the upper limit that can be reached in the present invention is about 600 meshes / inch. The number of meshes referred to in the present specification is a value obtained by the method described in the examples.

The thickness of the mesh fabric of the present invention is 25 μm or less. When it is 25 μm or less, the transmission volume becomes small and it is suitable for thin film printing. From this point of view, the thickness of the gauze should be small, and more preferably 23 μm or less. The lower limit of the thickness is not particularly limited, but the lower limit that can be reached in the present invention is about 10 μm. The thickness referred to in the present specification is a value obtained by the method described in the examples.

The fiber diameter of the mesh fabric of the present invention is preferably 25 μm or more. When the fiber diameter is 25 μm or more, the opening can be reduced and the transmitted volume becomes small, which is suitable for thin film printing. From this viewpoint, the fiber diameter is preferably large, and more preferably 30 μm or more. If the fiber diameter is too large, the paste wraps around insufficiently during printing, and there is a concern that film thickness unevenness may occur. Therefore, the fiber diameter is preferably 50 μm or less. The fiber diameter referred to in the present specification is a value obtained by the method described in Examples. The fiber cross section of the mesh woven fabric of the present invention is not a perfect circle, but has a shape close to an elliptical diameter crushed in the direction perpendicular to the fiber axis. Although referred to as the fiber diameter of the mesh fabric in the present specification, it should be noted that the length corresponds to the long axis of the elliptical cross section.

The opening (OP) of the mesh fabric of the present invention is preferably 50 μm or less. When the OP is 50 μm or less, the transmission volume becomes small and suitable for thin film printing. From this viewpoint, the OP should be as small as possible, more preferably 45 μm or less, and even more preferably 40 μm or less. The lower limit of OP is not particularly limited, but the lower limit that can be reached in the present invention is about 10 μm. The OP referred to in the present specification is a value obtained by the method described in the examples.

The opening area (OPA) of the mesh fabric of the present invention is preferably less than 30%. When the OPA is less than 30%, the transmitted volume becomes small and suitable for thin film printing. From this point of view, the OPA should be as small as possible, more preferably 25% or less, still more preferably 20% or less. The lower limit of OPA is not particularly limited, but the lower limit that can be reached in the present invention is about 10%. The OPA referred to in the present specification is a value obtained by the method described in the examples.

The tensile strength of the mesh fabric of the present invention is preferably 200 N / 5 cm or more. If the mesh woven fabric is made of liquid crystal polyester fiber and has a tensile strength of 200 N / 5 cm or more, the strength is sufficiently high, and the mesh is not easily plastically deformed, so that the printing durability is excellent. From this point of view, the higher the tensile strength is, the more preferably 300 N / 5 cm or more. The upper limit of the tensile strength is not particularly limited, but the upper limit that can be reached in the present invention is about 600 N / 5 cm. The tensile strength referred to in the present specification is a value obtained by the method described in the examples.

Since the mesh woven fabric of the present invention is made of liquid crystal polyester fiber, it has high strength, is not easily plastically deformed, and has excellent heat resistance and chemical resistance. Therefore, it is suitably used for screen plates, heat-resistant and chemical-resistant filters, and the like. In particular, since the number of meshes is large and the thickness is low, the transmission volume of the paste is small, and a screen plate suitable for thin film printing can be obtained.

Hereinafter, an example of manufacturing the mesh woven fabric of the present invention will be shown.
The composition of the liquid crystal polyester preferably used in the present invention is as described above. Using the liquid crystal polyester having such a composition, melt spinning, solid phase polymerization, and fibers are run by the techniques described in JP-A-2008-240230, JP-A-2010-248681, and WO2015 / 115259. A liquid crystal polyester fiber having excellent wear resistance can be obtained by performing high-temperature heat treatment while performing the same process. The liquid crystal polyester fiber thus obtained is warped to obtain a high-mesh woven fabric using a known rapier loom or the like.

Next, pressure is applied to the mesh to reduce the thickness of the gauze. The pressure applying method includes press processing using a flat plate and calendar processing in which a mesh is passed between two rotating rolls, but calendar processing is preferable because long mesh woven fabrics can be continuously processed. The mesh woven fabric of the present invention can be obtained by performing calender processing under, for example, a metal (iron) roll, a linear pressure of 100 kgf / cm or more, and a roll temperature of 50 ° C. or more as the calender processing conditions.

Hereinafter, the present invention will be described in more detail with reference to Examples. Each characteristic value in the examples was obtained by the following method.

A. Thermal characteristics (Tm1, Tm2, Tm1 peak half width, ΔHm1, ΔHm2)
The differential calorimetry was measured by DSC2920 manufactured by TA instruments, and the temperature of the endothermic peak observed when measured under the heating condition of 50 ° C. to 20 ° C./min was set to Tm1 (° C.), and the amount of heat of fusion at Tm1 was ΔHm1 (. J / g). After observing Tm1, the temperature is kept at Tm1 + 20 ° C. for 5 minutes, then cooled to 50 ° C. under the temperature lowering condition of 20 ° C./min, and then measured again under the temperature rising condition of 20 ° C./min. The temperature of Tm2 was set, and the amount of heat of fusion at Tm2 was set to ΔHm2 (J / g). The same measurement was performed for both the fiber and the resin, and the melting point of the resin was Tm2.

B. Polystyrene-equivalent weight average molecular weight (Mw)
A mixed solvent of pentafluorophenol / chloroform = 35/65 (weight ratio) was used as a solvent, and the liquid crystal polyester was dissolved so as to have a concentration of 0.04 to 0.08% by volume / volume to prepare a sample for GPC measurement. If there was an insoluble matter even after being left at room temperature for 24 hours, it was allowed to stand for another 24 hours, and the supernatant was used as a sample. This was measured using a GPC measuring device manufactured by Waters, and the weight average molecular weight (Mw) was determined by polystyrene conversion.
Column: Shodex K-806M 2 pcs, K-802 1 pcs Detector: Differential refractive index detector RI
Temperature: 23 ± 2 ° C
Flow rate: 0.8 mL / min Injection volume: 200 μL

C. Total fiber fineness, single fiber fineness 100 m of fiber was taken with a measuring machine, its weight (g) was multiplied by 100, and measurements were taken 3 times per level, and the average value was taken as total fineness (dtex). .. The quotient obtained by dividing this by the number of filaments was defined as the single fiber fineness (dtex).

D. Fiber strength, elongation, elastic modulus According to the method described in JIS L1013: 2010, measurement was performed 10 times per level using Tensilon UCT-100 manufactured by Orientec Co., Ltd. under the conditions of sample length of 100 mm and tensile speed of 50 mm / min. The average value was determined to be strong (cN), strength (cN / dtex), elongation (%), and elastic modulus (cN / dtex). The elastic modulus is the initial tensile resistance.

E. Tensile strength of mesh woven fabric According to JIS L1913 (2010) 63.1, a tensile test of n = 3 was performed under the conditions of sample size 5 cm x 30 cm, grip interval 20 cm, and tensile speed 10 cm / min, and the sample broke. The strength at that time was taken as the tensile strength (N / 5 cm), the average value was calculated, and the value rounded to the second digit after the decimal point was taken as the tensile strength (N / 5 cm).

F. A measurement was performed using a digital indicator manufactured by Mitutoyo Co., Ltd. in a state where a thick mesh woven fabric was stretched on a 300 mm square plate frame. Nine different points in the mesh fabric were measured, and the average of these was taken as the thickness (μm).

G. Fiber diameter, OP, number of meshes, OPA, transmission volume of the mesh woven fabric The fiber diameter and OP were measured using a KEYENCE microscope VHX-2000 with the mesh woven fabric stretched on a 300 mm square plate frame. The measurement position is approximately the midpoint between the intersections of the fibers that make up the mesh, and the fiber diameter and OP are measured at 10 different points in the mesh fabric, and the averaged values are the fiber diameter (μm) and OP (μm). And said. The number of meshes (lines / inch) was calculated by the following formula.
Number of meshes = 25400 / (OP + fiber diameter)

OPA (%) was calculated by the following formula.
OPA = OP ² / (OP + fiber diameter) ² x 100

The permeation volume (cc / m ² ) was calculated by the following formula using the thickness (μm) obtained in the D term.
Permeation volume = OPA / 100 x thickness

The mesh woven fabric of the present invention can be applied to thin film printing with a transmission volume of 6.0 cc / m ² or less. 5.0 cc / m ² or less is more preferable, and 4.0 cc / m ² or less is further preferable.

Reference example 1
870 parts by weight of p-hydroxybenzoic acid, 327 parts by weight of 4,4'-dihydroxybiphenyl, 89 parts by weight of hydroquinone, 292 parts by weight of terephthalic acid, 157 parts by weight of isophthalic acid in a 5 L reaction vessel equipped with a stirring blade and a distillate. And 1460 parts by weight of anhydrous acetic acid (1.10 equivalents of the total phenolic hydroxyl groups) were charged, and the temperature was raised from room temperature to 145 ° C. in 30 minutes while stirring in a nitrogen gas atmosphere, and then the reaction was carried out at 145 ° C. for 2 hours. Then, the temperature was raised to 335 ° C. in 4 hours.

The polymerization temperature was maintained at 335 ° C., the pressure was reduced to 133 Pa in 1.5 hours, the reaction was continued for another 40 minutes, and the polycondensation was completed when the torque reached 28 kg cm. Next, the inside of the reaction vessel was pressurized to 0.1 MPa, and the polymer was discharged into a strand shape via a mouthpiece having one circular discharge port having a diameter of 10 mm, and pelletized by a cutter.

The composition, melting point, and weight average molecular weight (Mw) of the obtained liquid crystal polyester are as shown in Table 1.

After vacuum drying at 160 ° C. for 12 hours using this liquid crystal polyester, the polymer was melt-extruded with a φ15 mm single shaft extruder manufactured by Osaka Seiki Kogyo Co., Ltd., and the polymer was supplied to the spinning pack while weighing with a gear pump. In the spinning pack, the polymer was filtered using a metal non-woven fabric filter, and the polymer was discharged under the conditions shown in Table 2. The introduction hole located directly above the mouthpiece hole was a straight hole, and the connection portion between the introduction hole and the mouthpiece hole was tapered. The discharged polymer is passed through a heat retention region of 40 mm, then cooled and solidified from the outside of the yarn by a cyclic cooling air of an air stream at 25 ° C., and then a spinning oil agent containing a fatty acid ester compound as a main component is applied. All filaments were taken up by a first godet roll at the spinning rates shown in Table 2. After passing this through the second godet roll at the same speed, suction is performed with a suction gun except for one of all the filaments, and the remaining fibers with the number of filaments 1 are passed through the dancer arm to the panwinder (EFT type manufactured by Kozu Seisakusho). It was wound into the shape of a pan with a take-up winder and no contact roll that contacts the winding package). Table 2 shows the physical properties of the obtained spun fiber.

This spun fiber package was rewound using an SSP-MV type rewinder manufactured by Kozu Seisakusho Co., Ltd. (contact length 200 mm, wind number 8.7, taper angle 45 °). The unraveled fibers were unwound in the longitudinal direction (perpendicular to the fiber circumferential direction), and the oil for solid phase polymerization was lubricated using an oiling roller (stainless steel roll with satin finish) without using a speed governor roller. .. Tarku SG-2000 (manufactured by Nippon Tarku Co., Ltd.) was dispersed in an aqueous solution containing 6.0% by weight of a phosphoric acid compound represented by the following chemical formula (1) as an oil for solid phase polymerization in an amount of 1.0% by weight.

As the rewinding core material, a stainless steel perforated bobbin wrapped with Kevlar felt (with a basis weight of 280 g / m ² and a thickness of 1.5 mm) was used, and the surface pressure was 100 gf. Table 3 shows the oil content adhesion rate of the solid phase polymer oil agent to the fibers after rewinding and the rewinding conditions.

Next, the stainless steel perforated bobbin was removed from the rewound package, and solid-phase polymerization was performed in the state of a package in which fibers were wound around Kevlar felt. For solid-phase polymerization, the temperature is raised from room temperature to 240 ° C. in about 30 minutes using a closed oven, held at 240 ° C. for 3 hours, and then raised to the maximum temperature shown in Table 3 at 4 ° C./hour. Then, it was held for the holding time shown in Table 3 and solid-phase polymerization was carried out. As for the atmosphere, dehumidified nitrogen was supplied at a flow rate of 20 NL / min and exhausted from the exhaust port so that the inside of the refrigerator was not excessively pressurized. Table 3 shows the physical properties of the obtained solid-phase polymerized fibers.

Next, the fibers were unwound from the package after solid-phase polymerization, and high-temperature non-contact heat treatment was continuously performed. The package after solid-phase polymerization is fitted into a free-roll creel (having a shaft and bearings, the outer layer can rotate freely. No brake and drive source), and the yarn is pulled out from here in the lateral direction (fiber circumference direction). The fibers were continuously passed through a bath having a bath length of 150 cm (contact length of 150 cm) having slits at both ends (without a guide that contacts the fibers inside), and the oil agent was washed and removed. The cleaning liquid is hot water at 50 ° C. containing 0.2 wt% of a nonionic / anionic surfactant (Grand Up US-30 manufactured by Sanyo Chemical Industries, Ltd.), the temperature is adjusted in an external tank, and the water tank is pumped. Supplied. When supplying to the water tank, a pipe with holes at intervals of 5 cm was passed through the water tank, and the liquid flow was given to the water tank by supplying to this pipe. A mechanism is provided to collect the cleaning liquid overflowing from the slit and the hole for adjusting the liquid level and return it to the external tank.

The washed fibers were subsequently passed through a bathtub with a bath length of 23 cm (contact length 23 cm) having slits at both ends (without a guide that contacts the fibers inside) and rinsed with warm water at 50 ° C. The rinsed fibers were passed through a bearing roller guide, blown off by an air stream to remove them, and then passed through a first roller with a separate roller. Since the creel is a free roll, by applying tension to the fiber by this roller, the fiber is unwound from the solid-phase polymerization package and the fiber is run.

The fibers that passed through the rollers were run between the heated slit heaters, and high-temperature non-contact heat treatment was performed under the conditions shown in Table 4. No guides are provided inside the slit heater, and the heater and fibers are not in contact with each other. After passing through the heater, the fibers were passed through a second roller with a separate roller. The yarn speed before the heat treatment represents the surface speed of the first roller, and the yarn speed after the heat treatment represents the surface speed of the second roller. The fibers that passed through the second roller were subjected to a finishing oil mainly composed of a fatty acid ester compound by a ceramic oiling roller, and wound into a pan shape by an EFT type bobbin traverse winder (manufactured by Kozu Seisakusho). Table 4 shows the physical properties of the fibers after the high-temperature heat treatment.

Reference example 2
Using the liquid crystal polyester obtained in Reference Example 1, melt spinning was carried out in the same manner as in Reference Example 1 except that the discharge amount and the spinning temperature were changed as shown in Table 2. Table 2 shows the physical properties of the obtained spun fiber. Next, solid-phase polymerization was carried out by rewinding in the same manner as in Reference Example 1 except that the rewinding conditions were changed as shown in Table 3. Table 3 shows the physical properties of the fiber after solid-phase polymerization. The unraveling, washing, and high-temperature heat treatment were carried out in the same manner as in Reference Example 1 except that the high-temperature heat treatment conditions were changed as shown in Table 4. Table 4 shows the physical properties of the fibers after the high-temperature heat treatment.

Example 1
Using the liquid crystal polyester fiber obtained in Reference Example 1, warping was performed for warp threads, and weaving was performed using a rapier loom so that the number of meshes was 380 lines / inch. The obtained woven fabric was made of upper and lower iron rolls, and calendered at a heating temperature of 70 ° C., a linear pressure of 200 kgf / m, and a processing speed of 3 m / min to obtain a mesh woven fabric.

The characteristics of this mesh fabric are shown in Table 5. Since the number of meshes is 350 lines / inch or more and the thickness of the gauze is 25 μm or less, the transmission volume is small, and it can be seen that the mesh characteristics are suitable for thin film printing in which the amount of paste used can be reduced.

Comparative Example 1, Example 2
Weaving was carried out in the same manner as in Example 1 to obtain a woven fabric. In Comparative Example 1, this was used as it was without calendering, and in Example 2, the calendering was performed in the same manner as in Example 1 except that the linear pressure was 100 kgf / m to obtain a mesh woven fabric.

The characteristics of these mesh fabrics are shown in Table 5. In Comparative Example 1, the number of meshes is 350 lines / inch or more, but the thickness of the gauze exceeds 25 μm, so that it can be seen that the transmission volume is large. In Example 2 in which the number of meshes is 350 lines / inch or more and the thickness of the gauze is 25 μm or less, the transmission volume is small, and it can be seen that the mesh characteristics are suitable for thin film printing in which the amount of paste used can be reduced.

Comparative Example 2
Using the liquid crystal polyester fiber obtained in Reference Example 1, weaving was performed in the same manner as in Example 1 except that the number of meshes was 330 fibers / inch, and the linear pressure was 100 kgf / m. A mesh woven fabric was obtained by performing calendar processing in the same manner as in 1.

The characteristics of this mesh fabric are shown in Table 5. Although the thickness of the gauze is 25 μm or less, it can be seen that the transmission volume is large because the number of meshes is smaller than 350 lines / inch.

Example 3
Using the liquid crystal polyester fiber obtained in Reference Example 2, weaving was carried out in the same manner as in Example 1. This was subjected to calendar processing in the same manner as in Example 1 to obtain a mesh woven fabric.

The characteristics of this mesh fabric are shown in Table 5. Since the number of meshes is 350 lines / inch or more and the thickness of the gauze is 25 μm or less, the transmission volume is small, and it can be seen that the mesh characteristics are suitable for thin film printing in which the amount of paste used can be reduced.

Claims (1)

A mesh woven fabric made of liquid crystal polyester fibers, having a mesh number of 350 fibers / 2.54 cm or more and a gauze thickness of 25 μm or less.