JP2004232182A - Polyester monofilament for screen gauze and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester monofilament suitable for high-precision screen printing, by overcoming such difficulty that high breaking strength and resistance to scum are not conventionally attained at the same time in the polyester monofilament. <P>SOLUTION: This polyester monofilament for a screen gauze is formed out of a polyester, wherein the monofilament satisfies the following requisites (1) to (3) at the same time: (1) the breaking strength of ≥6.0 cN/dtex; (2) an elongation percentage of ≥10%; and (3) a birefringence (Δn<SB>S</SB>) of ≤180×10<SP>-3</SP>on a surface of a fiber thereof. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a polyester monofilament suitable for a mesh fabric used for screen printing and a method for producing the same. More specifically, the present invention relates to a polyester monofilament suitable for forming a high-mesh screen gauze suitable for a field requiring high precision, such as an electronic circuit, and a method for producing the same.

  Conventionally, mesh fabrics made of natural fibers such as silk and inorganic fibers such as stainless steel have been widely used as screen gauze, but silk has problems in breaking strength and dimensional stability, and stainless steel has problems in elastic recovery. .

  In recent years, mesh fabrics made of organic fibers such as polyester and nylon have been generally used. Particularly, screen gauze made of polyester fiber, which has less influence on dimensional stability due to moisture than nylon, has excellent heat resistance and is inexpensive, has been widely used. However, in the field of printing electronic circuits in recent years, there has been an increasing demand for improved printing accuracy, so that high-mesh finer ones have been required, and the fiber diameter is smaller and the tension during weaving has been reduced. There is a demand for a durable fiber, that is, a high breaking strength monofilament.

  Generally, in order to increase the breaking strength of a fiber, it is sufficient to perform high-magnification stretching in the method of producing a raw yarn to highly orient and crystallize a molecular chain (see Patent Documents 1 and 2).

  However, in the screen gauze manufacturing process, an extremely high-density woven fabric is woven at a high speed, so that it is repeatedly rubbed with a single fiber / single fiber or a single fiber / device component (metal, etc.), and a part of the filament is cut off. Powder and fibril-like scum are likely to be generated. In particular, the higher the degree of orientation and crystallization, the greater this tendency, and the need to temporarily suspend weaving and clean the weaving machine arises. Connect. In addition, even if cleaning is not necessary, scum is generated because a part of the generated scum is woven into the gauze or the scum peels off due to rubbing by a squeegee and causes clogging, which deteriorates printing accuracy. Prevention is a very important consideration.

  In order to solve this problem, “a core / sheath composite monofilament made of polyester has a breaking strength of 6 g / d (= 5.3 cN / dtex) or more and a modulus at an elongation of 10% of 3.5 g / d (= 3 .1 cN / dtex) or more, the elongation at break is less than 33%, the glass transition temperature of the polyester constituting the sheath is lower than that of the core, 35 to 73 ° C., and the area ratio of the core: sheath is 70. : A high breaking strength polyester monofilament for screen gauze characterized by being in the range of 30 to 95: 5 (see Patent Document 3).

  This technology has a high breaking strength and is intended to suppress the generation of powdery or fibril-like scum, and the surface layer of the monofilament is covered with a soft polyester whose Tg is reduced by copolymerization, thereby causing abrasion during weaving. This is a technique for suppressing scum. However, the ultimate breaking strength of the fiber shown in the example is at most 8.2 g / d (= 7.2 cN / dtex), which does not satisfy the breaking strength level required for recent high-precision screen printing. However, because the Tg of the core component and the Tg of the sheath component are different, for example, if heating and stretching is performed under a temperature condition suitable for the core component, the sheath has a low melting point because the Tg of the sheath is low. When the fiber surface is disturbed, the scum resistance is deteriorated, and when the core component is heated and drawn under the temperature conditions suitable for the sheath component, the drawing tension is applied while the softening of the core component is insufficient, so that the core component is This leads to the generation of voids and a decrease in breaking strength, making it difficult to obtain a high breaking strength monofilament suitable for high precision printing. Furthermore, since the scum resistance is improved by softening the sheath component, it is effective against abrasion of a single fiber / single fiber, but is scraped by abrasion with a single fiber / metal (equipment parts, etc.). It has a drawback that it occurs and is inferior in the scum evaluation and does not reach the required level.

  A screen gauze comprising an aromatic polyester exhibiting melt anisotropy as a core component and a sheath-core composite fiber whose sheath component is a polymer not exhibiting melt anisotropy is disclosed (see Patent Document 4). This technique uses a wholly aromatic polyester made of a rigid polymer as a core component in order to increase both the breaking strength and the elastic modulus, and furthermore, there is a problem that the fiber made of the rigid polymer is liable to fibrillation, which is a drawback. To compensate for the problem, a polymer that does not exhibit melt anisotropy is used as a sheath component to prevent the generation of fluff and fibrillation. Certainly, the fiber has properties such as high breaking strength and high elastic modulus derived from the melt anisotropic polymer, but the elongation is very low as 2.5 to 3.0% as disclosed in Examples. However, when weaving screen gauze, there is a problem in the manufacturing process that yarn breakage occurs due to impact as compared with conventional polyester-based monofilaments. In addition, since the core / sheath component of the fiber is incompatible, fibrillation is improved, but the component / interface separation of the core / sheath is likely to occur, and the peeled sheath portion causes clogging of the screen gauze. Very difficult to apply to high precision screen printing. Further, since the wholly aromatic polyester is very expensive, there remains a substantial problem that the production cost of the target monofilament becomes very high.

In addition, there is a technical disclosure related to a fiber composed of a single yarn having a unique structure such that the viscosity and the birefringence are continuously reduced from the center of the cross section of the single yarn to the outside of the fiber ( Patent Document 5). The purpose of this technology is to "provide a polyester fiber having a high breaking strength and a low heat shrinkage by overcoming the difficulties of simultaneously achieving a high breaking strength and a low heat shrinkage" and "providing a birefringence of a single yarn cross section. The distribution becomes uniform, and it is possible to disperse the stress over the entire cross section of the single yarn in response to stress from the outside, and the highest high-strength physical properties are expressed. '' The fiber structure is used to achieve high strength. Are highly and uniformly oriented in the direction of the yarn cross section, so that the orientation of the fibers is very high in the final product stage. Therefore, even if the high-strength fiber is used as a monofilament for screen gauze, it is repeatedly rubbed with a single fiber / single fiber or a single fiber / metal (device part) at the time of weaving, whereby a powdery or fibril-like scum is obtained. Is produced, resulting in a screen gauze with many defects.
JP-A-63-262289 (2 pages) JP-A-5-295617 (paragraph [0007]) JP-A-2-289120 (Claims) JP-A-3-220340 (Claims) Japanese Patent Application Laid-Open No. 5-31513 (Claims)

  In order to apply a polyester monofilament to high-precision screen printing, a polyester monofilament having an even higher breaking strength and excellent scum resistance has been desired. There is also a need for a method for stably producing such fibers.

  An object of the present invention is to provide a polyester monofilament suitable for high-precision screen printing, overcoming difficulties in simultaneously achieving high breaking strength and scum resistance with respect to polyester monofilament.

  The present invention has been intensively studied to solve the problems in the polyester monofilament for screen gauze and the method for producing the same, and as a result, while having a high breaking strength, the fiber structure required for the polyester monofilament having significantly improved scum resistance has been developed. It has been discovered and led to the present invention.

The monofilament for screen gauze of the present invention is a monofilament for screen gauze characterized by simultaneously satisfying (1) to (3) among the core-sheath composite monofilament made of polyester.
(1) The breaking strength is 6.0 cN / dtex or more. (2) The elongation is 10% or more. (3) The birefringence Δn _S of the sheath component is 180 × 10 ^-3 or less. In addition, while having a high breaking strength, it has an appropriate elongation and is excellent in scum resistance, which is a characteristic that could not be achieved by the conventional technology.

  The polyester monofilament of the present invention, while having high breaking strength, completely prevents scum generation during weaving, and achieves a high mesh screen gauze suitable for high precision screen printing.

  In screen printing, generally, in order to improve the accuracy of a printing pattern, a method of increasing the tension of the gauze and reducing the distance between the screen gauze and the print target is adopted. In order to increase the tension at the time of gauging, it is necessary to improve the strength per fiber.

  In addition, the demands of the printing industry are severe, and demands a high-mesh, high-mesh, high-mesh mesh fabric. The tension applied to the yarn in the weaving process is not necessarily proportional to its fineness, and it is necessary that the strength per one monofilament be high. The thinner the yarn, the higher the breaking strength.

  It depends on the type of weaving machine used and the number of revolutions during weaving. However, according to the study by the present inventors, weaving can be practically carried out if the strength is about 50 g / or more.

  That is, if the breaking strength is about 5 cN / dtex, a monofilament of about 10 dtex can be provided, and if it is about 6 cN / dtex, fineness of up to 7.5 dtex can be achieved. Therefore, in order to apply to high-precision printing, a breaking strength of 6.0 cN / dtex or more is required. As described above, in order to increase the tension of the gauze and enable more precise printing, the breaking strength of the fiber is preferably 7.0 cN / dtex or more, more preferably 8.0 cN / dtex. That is all.

  In order to achieve such a high breaking strength, it is essential to perform a high degree of drawing at the stage of producing the raw yarn. As a result, the elongation is low. However, according to the study of the present inventors, it is clear that if the elongation is less than 10% during weaving, yarn breakage during weaving frequently occurs. Therefore, the elongation of the polyester monofilament for screen gauze of the present invention needs to be 10% or more, and preferably 15% or more.

  Since the polyester monofilament for screen gauze of the present invention has a unique fiber structure, even if the breaking strength is 8.0 cN / dtex or more, the weaving can be stably performed because it has an elongation of 10% or more. .

  Generally, in a polyester fiber, when trying to achieve high breaking strength, scum is generated during weaving. This is because, as the orientation and crystallization of the polyester fiber progress, the strength of the fiber increases in the fiber axis direction, but the fiber becomes brittle and becomes weak against bending, shearing, shaving, and the like. As long as a high breaking strength is required as a final product, the fiber itself needs to have the above-mentioned mechanical properties, but in the present invention, it is also an important subject to improve the scum resistance.

  The second feature of the present invention is a monofilament having such a high breaking strength, which is in a device for maintaining good weavability. That is, in a polyester monofilament for screen gauze, how to have high breaking strength It is to improve the scum resistance.

  The present inventors have succeeded in solving this major problem by using a polyester in which only two types of IV are changed without using a copolymer to form a core-sheath type composite monofilament and reducing the orientation of only the sheath component. Solved this problem.

  As described above, the occurrence of scum greatly correlates with the orientation and the degree of crystallinity. The lower the orientation of the fiber surface, that is, the lower the birefringence, the better the scum resistance. If the only purpose is to improve the scum resistance, the lower the orientation of the fiber surface (sheath component), the more effective it is. However, in order for the fiber to have high breaking strength, the orientation of the sheath component is also moderate. Is required.

Then, the present inventors diligently studied and found that when the birefringence was 180 × 10 ⁻³ or less, the generation of powdery or fibril-like scum was remarkably suppressed, and reached the present invention. Therefore, the polyester monofilament for screen gauze of the present invention preferably has a birefringence Δn _S of the fiber surface (sheath component) of 180 × 10 ⁻³ or less. In order to further improve the scum resistance, Δn _S is more preferably 175 × 10 ⁻³ or less, and further preferably 170 × 10 ⁻³ or less.

However, since the breaking strength is substantially borne by the core component, the difference (Δn _C −Δn _S ) between the birefringence Δn _C of the core component and the birefringence Δn _S of the sheath component is 5 × 10 ⁻³ or more and 20 × 10 ³ or more. ^-3 or less is preferable. When (Δn _C −Δn _S ) is in the above range, a monofilament for screen gauze having high strength and very excellent scum resistance can be obtained.

  Further, they have also found that the generation of powdery or fibril-like scum is remarkably suppressed even when the degree of amorphous orientation of the fiber surface layer is less than 0.70. Therefore, in the polyester monofilament for screen gauze of the present invention, the degree of amorphous orientation of the fiber surface layer is preferably less than 0.70, more preferably 0.68 or less, further preferably 0.60 or less. It is.

  The mechanism of improving the scum resistance by setting the degree of amorphous orientation of the fiber surface layer to less than 0.70 is not clear, but the degree of amorphous orientation is an index of looseness of the fiber structure, and the structure of the fiber surface layer is 0%. It is considered that the cause is that the structure has become easy to absorb the impact of repeated rubbing due to the decrease to less than 0.70. By doing so, while the structure of the fiber surface layer is protected by rigid crystals, it will be constituted by loose amorphous parts, and the occurrence of fubrill-like scum caused by the destruction of the amorphous parts due to repeated scratching will be reduced. It is considered that the suppression effect can be exhibited.

  In order to further improve the scum resistance, the crystallinity of the fiber surface layer is preferably 30% or more, more preferably 35% or more, and still more preferably 40% or more. By doing so, the ratio of the amorphous portion is reduced, and the effect of suppressing the generation of fibril-like scum caused by the destruction of the amorphous portion due to repeated rubbing is further improved.

  The fiber surface layer of the present invention depends on single fiber fineness (single yarn diameter), but it is sufficient that the average value from the fiber surface layer to 3 μm is the value described above.

  The method for producing a monofilament for screen gauze of the present invention is not particularly limited as long as a polyester monofilament having a unique structure as described above can be produced, but special yarn production conditions and special equipment are prepared. Is inferior in terms of productivity and cost. Therefore, it is necessary to produce the monofilament for screen gauze of the present invention without requiring special equipment. The present inventors have found that it is possible to produce the polyester monofilament for screen gauze of the present invention using conventional equipment by the production method described below. Hereinafter, the production method of the present invention will be described.

  The production method of the present invention comprises a step of stretching a non-stretched core-sheath type composite monofilament yarn made of polyester at a multistage stretching of 2.0 to 7.0 times, followed by a final stretching roller held at 180 to 230 ° C and a non-heating take-off roller. By performing a 2 to 10% relaxation treatment between them, the polyester monofilament for screen gauze of the present invention can be significantly produced from the viewpoint of process stability and cost without requiring special equipment.

  As a general method for producing a high breaking strength polyester monofilament, there is a method in which a high IV polyester is used, melt-spun to obtain an undrawn yarn, and the undrawn yarn is drawn at a high magnification. In addition, it is a known technique to perform high-magnification drawing by a heating roller in which polyester undrawn yarns are combined in multiple stages to obtain a drawn yarn having high strength.

  However, the monofilament obtained by this method has a high breaking strength as described above, but not only does the elongation necessarily inevitably decrease, but also the fiber structure, particularly the structure of the fiber surface, is significantly oriented. Therefore, there are defects such as frequent occurrence of yarn breakage during weaving, and scum due to repeated rubbing with single fibers / single fibers and single fibers / device parts (metals, etc.), making it impossible to weave. Precision screen printing has limited applications.

  The feature of the production method of the present invention is that, first, the undrawn yarn used is a core-sheath type composite polyester monofilament, and second, a multi-stage drawing and a final drawing roller held at 180 to 230 ° C. To perform a 2 to 10% relaxation treatment between the take-off rollers. The present inventors have made it possible to produce the polyester monofilament for screen gauze of the present invention by combining the first and second techniques, completely preventing scum during weaving while having high breaking strength, A high mesh screen gauze suitable for high precision screen printing is achieved.

  As described above, for example, in a core-sheath type conjugate fiber, a technique for improving the scum property by using a high IV polyester as a core component to increase the breaking strength and covering this with a soft sheath component is known. Things. However, simply stretching the fiber at a high magnification does not reach the level required for high-precision screen printing in both breaking strength and scum resistance.

  However, in the manufacturing method of the present invention, a 2 to 10% relaxation treatment is performed between the final stretching roller kept at 180 to 230 ° C and the unheated take-off roller. Therefore, the core component and the sheath component that are highly oriented before the final drawing roller instantaneously crystallize on the high-temperature final drawing roller, thereby completing the fiber structure. (Usually 90 ° C. to 140 ° C.), the fiber is subjected to a relaxation treatment between the final drawing roller and the take-off roller while the temperature is high, and the low sheath component of the polymer IV is quickly removed. The structure relaxes and the orientation decreases.

  As a result, it is possible to obtain a reduction in sheath orientation, that is, scum resistance, which has conventionally been difficult to obtain. On the other hand, since the core component has a highly formed structure on the final stretching roller, the structure is hardly relaxed, and high breaking strength can be maintained. As described above, in the production method of the present invention, the polyester for screen gauze of the present invention, which does not require special equipment, has a high breaking strength that was difficult to obtain by the conventional technique, and has excellent scum resistance It is possible to obtain a monofilament.

  The final stretching roller temperature of the present invention needs to be in the range of 180 to 230 ° C. If the temperature of the final stretching roller is less than 180 ° C., it is difficult to relax the sheath portion described above. On the other hand, when the temperature exceeds 230 ° C., fusion to the final stretching roller is apt to occur, and the spinning property deteriorates. In order to make the scum resistance more effective, the final stretching roller temperature is more preferably in the range of 200 to 230 ° C.

  The relaxation treatment in the present invention is performed by changing the number of revolutions of the roller between the final stretching roller and the unheated take-off roller.

  Usually, a technique called a relaxation heat treatment is performed between two pairs of heating rollers to sufficiently crystallize, fix the fiber structure, and reduce the heat shrinkage of the drawn yarn. The technical content and the purpose are different from the relaxation process of the above.

The relaxation treatment of the present invention aims at lowering the orientation of the sheath component, and needs to have a relaxation rate of 2 to 10%. Specifically speed ratio of the final drawing roller speed (V ₁₎ and non-heated take-off roller speed _{(V 2) (V 2 /} V 1) is made to be 0.90 to 0.98. When the relaxation ratio is less than 2%, the orientation of the sheath component is insufficiently reduced, and the scum resistance is reduced. On the other hand, if the relaxation rate is more than 10%, the winding around the final stretching roller is likely to occur, which is not preferable. In order to stabilize the spinnability and make the present invention more effective, the relaxation rate is more preferably 2 to 6%, and still more preferably 3 to 5%.

  The multi-stage drawing according to the present invention refers to a process in which an undrawn yarn is drawn 2.0 to 7.0 times by changing the number of rotations of a heating roller combined in multiple stages. The number of heating rollers is not particularly limited. In order to achieve the object of the present invention, it is necessary to stretch the undrawn yarn at a high magnification, but if this is performed with a pair of heating rollers, the drawing tension increases, so that yarn spots increase, Since problems such as frequent breakage occur, it is necessary to perform the operation by combining multiple rollers. However, considering the cost, the device space, and the operability, the number of the heating rollers is preferably 3 to 6.

  The surface condition of the heating roller used in the present invention is not particularly limited, but the first heating stretching roller has a mirror finish for fixing the stretching point, and thereafter has a matte finish for preventing fusion, thereby reducing thread spots. In addition, it is preferable because the spinning is improved.

  In the multi-stage stretching, the temperature condition of the heating roller can be appropriately set at a temperature at which the running yarn does not fuse to the roller, but the first heating roller usually has a glass transition temperature (hereinafter, Tg) of the core and sheath polymer. It is appropriate that the temperature is set to +10 to 30 ° C. and the temperature is gradually increased after the second heating roller. However, it is preferable that the roller temperature before the final stretching roller is equal to or lower than the final stretching roller temperature.

  The stretching ratio of the multi-stage stretching in the present invention can be carried out without any particular limitation, but it is preferably 2.0 to 7.0 times in order to obtain a high breaking strength monofilament suitable for the purpose of the present invention. When the draw ratio is less than 2.0 times, the fiber structure of the obtained drawn yarn is low-oriented, so that it is difficult to obtain a high breaking strength monofilament. When the stretching is performed at a magnification exceeding 7.0 times, the stretching tension becomes extremely high, so that the yarn breakage frequently occurs, and not only the yarn-making properties are deteriorated, but also the scum resistance due to yarn spots is promoted. Therefore, the stretching ratio in the case of multi-stage stretching is preferably 2.0 to 7.0 times, more preferably 4.0 to 6.5 times, and still more preferably 4.5 to 6.0 times. It is. When the draw ratio is in the range of 4.5 to 6.0 times, a monofilament having high breaking strength and excellent scum resistance suitable for high-precision screen printing can be obtained with good spinning properties.

At this time, the following formula [I] is applied between the first heating roller and the second heating roller.
0.6Rn ≦ R1 ≦ 0.95Rn ... [I]
Here, Rn: the limit stretching ratio of the undrawn yarn R1: the stretching ratio (second heating roller speed / first heating roller speed)
When the film is stretched so as to satisfy the following condition, the Worster spots (hereinafter referred to as U%) of the obtained monofilament can be reduced.

  The first heating roller and the second heating roller referred to in the present invention are two pairs of rollers in which the first stage of the multistage stretching is performed. In addition, Rn (limit drawing ratio of undrawn yarn) means a supply roller and a drawing roller with the speed and temperature conditions according to the implementation, and while keeping the speed of the supply roller, increasing the speed of the drawing roll, It refers to the speed ratio between the supply roller and the stretching roller when the strip cannot run.

  When the first stage stretching ratio is 0.6 Rn to 0.95 Rn, the stretching point is fixed, and a very uniform monofilament for screen gauze can be obtained. Therefore, the first stage stretching ratio is preferably set in the range of 0.6Rn to 0.95Rn, more preferably 0.70Rn to 0.95Rn. In particular, when the first-stage stretching is performed at 0.70 Rn to 0.95 Rn, the value of U% is low, and a monofilament excellent in uniformity can be obtained.

  The core-sheath type composite polyester monofilament undrawn yarn in the production method of the present invention can be produced using a conventionally known composite spinning method. For example, by independently melting and weighing the polymer forming the core and the sheath, merging them so as to form a core-sheath structure on the back of the mouthpiece, once discharging from the same discharge hole, once cooling and solidifying to a glass transition temperature or less, and taking off. can get. At this time, the drawing may be performed after the undrawn yarn is continuously or temporarily drawn.

  As the polyester constituting the core component and the sheath component of the core-sheath type composite polyester monofilament undrawn yarn in the present invention, a small amount of a third component other than polyethylene terephthalate, terephthalic acid component and ethylene glycol component having ethylene terephthalate as a main repeating unit ( (Usually 20 mol% or less). It may be composed of a copolymerized and / or mixed polyester. As the core component, polyethylene 2,6 naphthalate or the like having a high elastic modulus can also be used. Polyethylene terephthalate is preferred in terms of heat resistance, cost, and the like. Further, additives such as a flame retardant, a water repellent, an antistatic agent, a static eliminator, and an ultraviolet absorber may be contained in the polymer as needed.

In the present invention, in order to achieve high strength in the IV _C of the polymer constituting the core component at least 0.8, IV ratio of the polymer constituting the IV _S and core of the polymer constituting the sheath (IV _S / IV _C ) is preferably 0.7 or less, and the composite ratio of the core component and the sheath component is preferably in the range of 60/40 to 90/10.

  The reason for adopting such a configuration is that, when the molten polymer is discharged from the die hole, the orientation of the molecules in the surface portion of the single yarn is generally promoted by the shearing force generated between the hole wall surface and the polymer, and the discharge is performed. This is because the uniformity of the orientation of the molecules in the cross section direction of the single yarn is impaired, and the subsequent stretchability is considered to be greatly reduced.

  Therefore, by using a high IV polymer as a core component and a low IV polymer as a sheath component for the purpose of increasing the breaking strength, which is the object of the present invention, a large shear force with the pore wall surface is absorbed by the low IV sheath component. In addition to making the state of the molecular chain of the core polymer uniform, taking advantage of the fact that the sheath component polymer that has received a large strain relaxes instantaneously after ejection, resulting in a smaller strain, and the subsequent stretchability is improved. They are trying to improve. Accordingly, even if the area ratio of the core component is less than 50%, the effect of structural uniformity of the molecular chain can be obtained, but since the core component plays the role of the drawn yarn breaking strength substantially, the high breaking strength screen gauze aimed at by the present invention is intended. It may not be suitable for obtaining a monofilament for use. On the other hand, when the area ratio of the core component is larger than 90%, it is difficult to form a uniform core-sheath structure, the core is partially exposed, and the fibril resistance and the sheath peel resistance decrease. May be undesirable. Accordingly, the area ratio of the core / sheath is preferably 60/40 to 90/10, and more preferably 70/30 to 80/20.

In this case, it is preferable that the polymer constituting the sheath component IV (IV _S) and IV ratio of the polymer constituting the core component (IV _S / IV _C) and 0.7 or less. IV ratio of the polymer constituting the IV _S and fiber center of the polymer constituting the fiber surface (IV _S / IV _C) and the improved uniformity of the shear stress when 0.7 or less, the wound undrawn yarn Since the core component has a uniform structure, the draw ratio can be increased. Further, in order to lower the orientation of the sheath component and further improve the scum resistance, the IV ratio is more preferably 0.4 or less, further preferably 0.2 or less.

  It is known that the higher the polymer IV, the higher the drawn yarn properties are, the higher the breaking strength. However, since the core-in-sheath type polyester monofilament of the present invention substantially bears the breaking strength, When the IV of the polymer is 0.8 or more, an undrawn yarn suitable for the purpose of the present invention can be easily obtained. Considering substantial productivity, the IV of the polymer constituting the core is preferably 0.8 or more, more preferably 1.0 or more, and further preferably 1.2 or more.

  The take-up speed of the undrawn yarn can be carried out without any particular limitation, but the take-up speed of the undrawn yarn is preferably in the range of 500 to 1000 m / min, more preferably 600 to 900 m / min. Is within the range.

  When the take-off speed is set to 500 to 1000 m / min, it is possible to draw at a high magnification without forming a fiber structure of an undrawn yarn on a spun wire, and it is possible to obtain a high-strength monofilament with good productivity. Become.

  The fineness of the core-sheath composite polyester monofilament undrawn yarn used in the present invention is not particularly limited, and may be determined by the drawn yarn fineness according to the intended use. However, since the technique of the present invention is to produce a monofilament suitable for high-precision screen printing, considering the productivity, handleability and fineness of the final product, the fineness of the undrawn yarn is preferably 25 dtex to 150 dtex, It is more preferably 30 dtex to 70 dtex, and still more preferably 30 to 50 dtex.

  Further, the monofilament preferably has a circular cross section. This is because when hardening the photosensitive emulsion with a woven screen gauze, in the case of a monofilament having a deformed cross section, halation occurs, which adversely affects the printing accuracy and may cause problems such as loss of uniformity of the opening. Because there is.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto. The physical properties in the examples were measured by the following methods.
[Intrinsic viscosity (IV)]
It was calculated from the value measured at 25 ° C. in orthochlorophenol.
[Glass transition temperature Tg (° C)]
Using a differential scanning calorimeter (Perkin Elmer: DSC-4 type), 10 mg of a powder of the polymer to be used was sampled, and the temperature was raised at 16 ° C./min. The glass transition temperature Tg (° C.) is obtained by processing with a data processing system manufactured by Perkin Elmer.
[Elongation at break, modulus of elasticity cN / dtex,%]
Using an Orientex Tensilon tensile tester, the measurement was performed at an initial sample length of 50 mm and a tensile speed of 400 mm / min for an undrawn yarn, and at an initial sample length of 200 mm and a tensile speed of 200 mm / min for a drawn yarn.
[The birefringence of the whole fiber ΔnALL × 10 ^-3 ]
It was determined from the retardation and the fiber diameter by a normal interference fringe method using a BH-2 polarizing microscope compensator manufactured by OLYMPUS.
[Measurement of birefringence of core component and sheath component]
After embedding the sample in an epoxy resin, the sample was processed into a section having a thickness of 1 μm using a microtome, and the measurement was performed using Ramanor T-64000 manufactured by Horiba Joban Yvon. An Ar ⁺ laser (514.5 nm, 50 mW) was used as a light source, and the light was condensed to 1 μm by a 100 × objective lens. Raman scattered light was detected by a CCD detector under the conditions of a single mode, a slit of 100 μm, and a diffraction grating of 1800 gr / mm.

  The measurement was performed at each of the five points of the sheath component and the core component, and Raman band parameters were calculated for each measurement result, and the average value was obtained. The following equation was used for the PET Raman band parameters.

Intensity ratio R = I ₁₆₁₅ parallel / I ₁₆₁₅ vertical I ₁₆₁₅ parallel: the intensity I ₁₆₁₅ vertical 1615 cm ^-1 Raman band at parallel deflection arrangement the fiber direction: the 1615 cm ^-1 Raman band at the fiber direction perpendicular polarization arrangement Intensity-converted birefringence is defined as follows.

Δn (× 10 ⁻³ ) = 275 × (R−1) / (R + 2)
(The converted birefringence was determined using a uniaxially drawn fiber as a standard.)
[Measurement of degree of amorphous orientation and crystallinity of fiber surface layer]
After embedding the sample in an epoxy resin, the sample was processed into a section having a thickness of 1 μm using a microtome, and the measurement was performed using Ramanor T-64000 manufactured by Horiba John Ban Yvon. An Ar ⁺ laser (514.5 nm, 50 mW) was used as a light source, and the light was condensed to 1 μm by a 100 × objective lens. Raman scattered light was detected by a CCD detector under the conditions of a single mode, a slit of 100 μm, and a diffraction grating of 1800 gr / mm.

The measurement was performed every 1 μm from the fiber surface layer to 3 μm, the Raman band parameter was calculated for each measurement result, and the average value was obtained. The following equation was used for the PET Raman band parameters.
Intensity ratio R = I ₁₆₁₅ parallel / I ₁₆₁₅ vertical I ₁₆₁₅ parallel: intensity of ₁₆₁₅ cm ^-1 Raman band in deflection arrangement parallel to fiber direction I ₁₆₁₅ vertical: ₁₆₁₅ cm ^-1 Raman band in deflection arrangement perpendicular to fiber direction The intensity conversion birefringence (Δn) and conversion density (ρ) are defined as follows.
Δn (× 10 ⁻³ ) = 275 × (R−1) / (R−2)
ρ (g / cm ³ ) = (305−Δν1730) / 209
Δν 1730: Raman band full width at half maximum around 1730 cm ⁻¹ (converted birefringence and converted density were determined using a uniaxially drawn fiber as a standard).
The crystallinity χ is determined from the above-mentioned ρ according to the following definition.
χ (%) = 100 × (ρ-1.335) / (1.455-1.335)
The degree of amorphous orientation fa is determined from the values of Δn and χ according to the following definition.
fa = (Δn-χ · Δn c 0) / {(1-χ) · Δn a 0}
Δn _c 0: limiting crystal birefringence 0.220
Δn _a 0: Ultimate amorphous birefringence 0.235
[Worcester spots (U%)]
Using a Worcester spot tester manufactured by Zellbeger Worcester Co., Ltd., the yarn speed was measured at 100 m / min and the measurement type was normal, and the U% value was determined.
[Fibril resistance evaluation (times)]
Using a single yarn, a yarn is hung on a matte metal rod of φ3 mm at a contact angle of 35 °, and gripped at a position of 340 mm from the metal rod with a yarn tension of 1.5 cN / dtex, with a stroke length of 30 mm and a speed of 100 times / min. A reciprocating motion was applied, and the number of times of fluff (peeling, fibrillation) occurred was measured.
[Abrasion resistance (reed cleaning cycle) (m)]
The mesh woven fabric is woven from a sluser type loom at a rotation speed of the loom of 350 rpm. When it was determined that it was impossible to continue weaving while observing the degree of dirt on the reed, the machine was stopped and the reed was washed. The weaving length at that time is defined as a reed cleaning cycle (m). The shorter the cleaning cycle, the more scum is generated.

Examples 1-4, Comparative Examples 1-3
Polyethylene terephthalate having an intrinsic viscosity IV of 1.2 was prepared as a core component of a core-sheath type composite polyester monofilament, and polyethylene terephthalate having an intrinsic viscosity IV of 0.5 was prepared as a sheath component.

  According to a conventionally known composite spinning method, the discharge ratio is adjusted so that the area ratio of the core / sheath composite ratio becomes 80/20, and the concentric composite monofilament is spun at a spinning temperature of 300 ° C. at a spinning speed of 600 m / min. An undrawn yarn of a sheath composite type monofilament was obtained.

  The obtained undrawn yarn was stretched in two stages so that the drawn yarn fineness was 8 dtex using a hot roller maintained at a first heating roller of 90 ° C., a second heating roller of 140 ° C., and a final drawing roller of 230 ° C. The final stretch roller and the unheated take-off roller speed ratio were changed stepwise to take up. The monofilament was woven and finished to give a 330 mesh high mesh gauze.

  The details of the yarn-making conditions, the physical properties of the drawn yarn and the evaluation results of the gauze are shown in the table below.

Examples 5 to 7
Polyethylene terephthalate having an intrinsic viscosity of 1.2 or 1.5 was prepared as a core component of the core-sheath composite polyester monofilament, and polyethylene terephthalate having an intrinsic viscosity IV of 0.4 or 0.6 was prepared as a sheath component.

  According to a conventionally known composite spinning method, the discharge rate is adjusted so that the composite ratio of the core and the sheath becomes an area ratio of 80/20, and the concentric composite monofilament is spun at a spinning temperature of 300 ° C. at a spinning speed of 600 m / min. An undrawn yarn of the type composite monofilament was obtained.

  The obtained undrawn yarn was subjected to two-stage drawing using a hot roller maintained at 90 ° C. for the first heating roller, 140 ° C. for the second heating roller, and 230 ° C. for the final drawing roller so that the drawn yarn fineness was 8.5 dtex. Thereafter, the final stretch roller and the unheated take-off roller speed ratio were set to 0.96, and then subjected to a 4% relaxation treatment, followed by winding.

  The monofilament was woven and finished to give a 330 mesh high mesh gauze.

  The details of the yarn-making conditions, the physical properties of the drawn yarn and the evaluation results of the gauze are shown in the table below.

Example 8, Comparative Example 4
Except that the final stretching roller temperature was set to 140 and 180 ° C., all the procedures were performed according to Example 2.

  The details of the yarn-making conditions, the physical properties of the drawn yarn and the evaluation results of the gauze are shown in the table below.

Examples 9 and 10
Except that the total stretching ratio was 4.5 times and 6.0 times, all were carried out in accordance with Example 2.
The details of the yarn-making conditions, the physical properties of the drawn yarn and the evaluation results of the gauze are shown in the table below.

Examples 11 to 13
Except that the speed ratio between the final stretching roller and the unheated take-off roller was set to 0.98, 0.94, and 0.90, the same procedure was performed as in Example 6.

  The details of the yarn-making conditions, the physical properties of the drawn yarn and the evaluation results of the gauze are shown in the table below.

Examples 14 and 15
Except that the total stretching ratio was 4.5 times and 6.0 times, the same procedure was performed as in Example 6.
The details of the yarn-making conditions, the physical properties of the drawn yarn and the evaluation results of the gauze are shown in the table below.

Examples 16 and 17
Except that the spinning speed was 900 m / min and the total draw ratio was 4.5 times or 3.4 times, the same procedure was performed as in Example 6.

  The details of the yarn-making conditions, the physical properties of the drawn yarn and the evaluation results of the gauze are shown in the table below.

Comparative Examples 5 to 8
Polyethylene terephthalate having an intrinsic viscosity IV of 1.2 was spun at a spinning temperature of 300 ° C. and a spinning speed of 600 m / min according to a conventionally known melt spinning method to obtain a single monofilament undrawn yarn.

  The obtained undrawn yarn was stretched in two stages so that the drawn yarn fineness was 8 dtex using a hot roller maintained at a first heating roller of 90 ° C., a second heating roller of 140 ° C., and a final drawing roller of 230 ° C. The final stretch roller and the unheated take-off roller speed ratio were changed stepwise to take up. The monofilament was woven and finished to give a 330 mesh high mesh gauze.

  The details of the yarn-making conditions, the physical properties of the drawn yarn and the evaluation results of the gauze are shown in the table below.

Comparative Examples 9 and 10
Polyethylene terephthalate (A) having an intrinsic viscosity IV = 0.80 was prepared as a core component of the core-sheath type composite monofilament. On the other hand, as the sheath component, a polymer (B) having an intrinsic viscosity IV = 0.67 was prepared by adding 8% by weight of polyethylene glycol having a molecular weight of 1000 during the polymerization of polyethylene terephthalate.

  According to a conventionally known composite spinning method, the discharge rate is adjusted so that the composite ratio of the core and the sheath becomes an area ratio of 90/10, and a concentric composite monofilament is spun at a spinning temperature of 295 ° C. at a spinning speed of 600 m / min. An undrawn yarn of a sheath-type composite monofilament was obtained.

  After stretching the obtained undrawn yarn using a pair of hot rollers holding the first heating roller at 90 ° C. and the second heating roller at 140 ° C. so that the drawn yarn fineness becomes 8.9 dtex, the final drawn roller Without using the second heating roller and the unheated take-off roller speed ratio was 1.05.

  The monofilament was woven and finished to give a 330 mesh high mesh gauze.

  The details of the yarn-making conditions, the physical properties of the drawn yarn and the evaluation results of the gauze are shown in the table below.

Comparative Example 11
Stretching is performed by a pair of heating rollers maintained at a first heating roller 90 and a second heating roller 140 ° C., and without using a final stretching roller, the speed ratio between the take-up roller and the non-heating roller is 0.96, and the relaxation rate is 4 The procedure was the same as in Example 2 except that the film was wound as a percentage.

  The details of the yarn-making conditions, the physical properties of the drawn yarn and the evaluation results of the gauze are shown in the table below.

Comparative Examples 12 to 14
The procedure was performed in the same manner as in Example 6 except that the speed ratio between the final stretching roller and the unheated take-off roller was 1.01, 1.05, and 1.10.

  The details of the yarn-making conditions, the physical properties of the drawn yarn and the evaluation results of the gauze are shown in the table below.

Comparative Example 15
Except that the speed of the final stretching roller and the unheated take-off roller was set to 1.01, all the procedures were performed in accordance with Example 16.

  The details of the yarn-making conditions, the physical properties of the drawn yarn and the evaluation results of the gauze are shown in the table below.

  The present invention relates to a polyester monofilament suitable for a mesh fabric used for screen printing and a method for producing the same. More specifically, the present invention relates to a polyester monofilament suitable for forming a high-mesh screen gauze suitable for a field requiring high precision, such as an electronic circuit, and a method for producing the same.

1 is an example of an apparatus for describing a stretching method that can be suitably adopted in the present invention.

Explanation of reference numerals

1: undrawn yarn 2: supply roller (not heated)
3: First heating roller 4: Second heating roller 5: Final stretching roller (heating)
6: take-up roller (not heated)
7: Winding thread 8: Winding device (spindle)

Claims (7)

A polyester monofilament for screen gauze, wherein (1) to (3) are simultaneously satisfied in a core-sheath type composite monofilament made of polyester.
(1) The breaking strength is 6.0 cN / dtex or more. (2) The elongation is 10% or more. (3) The birefringence Δn _{S of the} sheath component is 180 × 10 ^-3 or less.   The polyester monofilament for screen gauze according to claim 1, wherein the degree of amorphous orientation of the fiber surface layer is less than 0.70.   The polyester monofilament for screen gauze according to claim 2, wherein the crystallinity of the fiber surface layer is 30% or more. 4. The polyester monofilament for screen gauze according to claim 1, wherein the core-sheath type composite monofilament made of polyester has a filament configuration of (1) to (3). 5.
(1) The IV (IV _C ) of the polymer constituting the core component is 0.8 or more. (2) The ratio (IV _S / IV _C ) of IV (IV _S ) to the IV _C of the polymer constituting the sheath component is 0. 7 or less (3) The composite area ratio of core / sheath is 60/40 to 90/10   After multi-stretching the core-sheath type composite monofilament undrawn yarn made of polyester by 2.0 to 7.0 times, 2 to 10% is applied between the final drawing roller held at 180 to 230 ° C and the unheated take-off roller. A method for producing a polyester monofilament for screen gauze, which comprises performing a relaxation treatment. 6. The process of stretching the unstretched core-sheath composite monofilament yarn made of polyester, wherein the stretching is performed between the first heating roller and the second heating roller so as to satisfy the following formula [I]. Of producing polyester monofilament for screen gauze.
0.6Rn ≦ R1 ≦ 0.95Rn ... [I]
Here, Rn: the limit stretching ratio of the undrawn yarn R1: the stretching ratio (second heating roller speed / first heating roller speed)   The method for producing a polyester monofilament for screen gauze according to claim 5 or 6, wherein the core-sheath type composite monofilament undrawn yarn made of polyester drawn at a speed of 500 to 1000 m / min is drawn.

Images