JPH04100914A - Polyethylene-2,6-naphthalate monofilament for screen gauze - Google Patents

Abstract

PURPOSE:To obtain the subject high-strength and high-elastic modulus monofilament, having a breaking strength, breaking elongation and elastic modulus satisfying specific ranges with a specified value of above of knot strength thereof, capable of providing screen gauzes under a high tension and suitable for highly precise printing. CONSTITUTION:The objective monofilament is composed of polyethylene-2,6- naphthalate monofilament and simultaneously satisfying >=6.0(g/d) breaking strength, 3-30 (%) breaking elongation and >=170(g/d) elastic modulus with >=3.5g(g/d) knot strength. Furthermore, a polymer having 0.55-1.0 intrinsic viscosity [eta] (35 deg.C) is preferably employed as the polymer used for the spinning.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a polyethylene-2,6-naphthalate monofilament for screen gauze.

[Prior Art] In recent years, screen printing has become a printing method that is simpler and more productive than other printing techniques, not only for printing various electronic circuits but also for other printing fields.
Its spread is remarkable.

In this type of screen printing, the screen gauze is
It is fixed to a gauze frame with high tension and is repeatedly rubbed with a squeegee during printing. Therefore, printing screen gauze is required to have strength and dimensional stability that can withstand a high degree of stress, but what is important in high-performance printing is how much the misalignment between the original figure and the printed figure can be minimized. This misalignment is caused by the so-called dimensional change of the original plate that gradually increases with repeated printing, and the distance between the screen original plate and the printing material due to the low elastic modulus of the screen gauze, that is, the large off-contact. There is a discrepancy that occurs between the two, and it is required to satisfy the characteristics of both.

For example, the use of a screen made of nylon has the drawbacks of low elastic modulus and dimensional changes due to moisture absorption.

On the other hand, screens made of polyethylene terephthalate fibers have excellent dimensional stability and an elastic modulus of 100.
It has a high yield of ~150 g/d and is suitably used for screen printing electronic circuits. However, the integration of electronic circuits is progressing rapidly, and for high-precision printing, materials with even higher initial elastic modulus are required.

In response to this requirement, stainless steel fiber screens are known as high elastic modulus metal materials that are not organic fibers.

Stainless fibers have a high elastic modulus and do not change in size due to moisture absorption or temperature changes, but they are prone to yielding even under minute strain. Therefore, it has the disadvantage that it becomes unusable due to excessive deformation or impact during handling, and permanent deformation occurs during repeated printing, and it is also expensive.

Therefore, there is a need for a monofilament material for screen gauze, which is an organic fiber with good dimensional stability and a high modulus of elasticity.

For example, in the case of polyethylene terephthalate, the initial tensile modulus exceeds 200 g/d by using a polymer with an extremely high degree of polymerization and performing multi-stage stretching using the action of a solvent, as shown in JP-A-198711. High modulus yarns can also be obtained. However, such a manufacturing method is extremely complicated, and although it is suitable for manufacturing thick denier multifilament for materials such as tire cords and ropes, it is undesirable for manufacturing fine denier monofilament around LOd because it imposes a large cost burden. . Furthermore, the high modulus polyethylene terephthalate fibers obtained in this manner generally have low elongation and are not suitable for weaving high-density screen gauze of over 300 meshes in which the weave has severe bending.

When applying such high modulus fibers to screen gauze applications, a method for improving weavability and printing properties has been proposed in JP-A-63-247093. The publication is 200
Fibers with a high elastic modulus of g/d or more are coated with polyamide resin. However, the above method also has the following drawbacks. Polyamide certainly has good adhesion with photosensitive resins and does not cause scum during weaving, but it has poor dimensional stability when wet, and even if polyamide is used as a coating, dimensional stability is poor. This has a negative impact on the accuracy of precision printing.This problem can be alleviated by reducing the thickness of the coating layer, but peeling may occur at the interface due to the adhesiveness with the high elastic modulus yarn that serves as the core. This could easily encourage scum.

Furthermore, it is extremely difficult to obtain fibers with high roundness and small diameter fluctuations by coating, and this method is not suitable as a method for obtaining screen gauze fabrics with uniform openings, which are essential for precision printing.

[Problems to be Solved by the Invention] An object of the present invention is to provide a monofilament for screen gauze that has excellent mechanical properties such as breaking strength and modulus of elasticity and is less likely to cause scum or scraping during the weaving process.

In particular, the present invention provides a polyester-based high-strength, high-modulus monofilament that has excellent dimensional stability and is suitable for producing screen printing plates with high gauze tension and low off-contact.

[Means for Solving the Problems] The structure of the monofilament for screen gauze of the present invention that achieves the above-mentioned objects of the present invention is as follows.

That is, polyethylene-2 for screen gauze is a monofilament made of polyethylene-2,6-naphthalate that satisfies the following (a) to (c) at the same time and has a knot strength of 3.5 g/d or more. ,6-
Naphthalate monofilament, (a) 6.0≦ Breaking strength (g/d) (b) 3≦
Elongation at break (%) ≦30 (c) 170 ≦ Elastic modulus
(g/d).

In the present invention, polyethylene-2,6-naphthalate is typically a polyethylene-2,6-naphthalate homopolymer;
Copolymerized components can also be used. Here, as the main third component, any known components such as dicarboxylic acid components such as terephthalic acid and isophthalic acid, and glycol components such as polyethylene glycol and butanediol can be used.

The polyester may also contain titanium dioxide, alumina, a calcium compound, a coloring pigment, and especially an ultraviolet absorber that suppresses the scattering and reflection of ultraviolet rays that are irradiated when curing the photosensitive resin. Stabilizers such as phosphorous acids and their esters may also be included.

Furthermore, polyethylene terephthalate or the like may be mixed and used, or may be used as a core component of a core-sheath composite fiber. In this case, it is preferable to select a polyester with a relatively low Tg that does not easily form scum for the sheath.

Regarding polyethylene-2,6-naphthalate fiber,
Special Publication No. 47-49769, Special Publication No. 47-4977
Publication No. 0, Special Publication No. 47-50329, Special Publication No. 5B
-42682, etc., and is used for various industrial materials that require mechanical properties and thermal properties, such as tires,
It has been suggested that it is useful as a reinforcing material for belts, hoses, etc., and as an electrical insulation material.

It is well known that polyethylene-2,6-naphthalate fiber can have a higher elastic modulus than polyethylene terephthalate fiber, which is conventionally widely used as a raw yarn for screen gauze. It is difficult to weave a high-density mesh fabric just by having a high That is, in the weaving process of mesh fabric,
In particular, the warp yarns are repeatedly scratched by an extremely fast reed of several hundred strokes - 27 minutes. Also, the distance between the intersection points of the latitude and longitude is
In a high-density fabric with more than 300 meshes, the fiber diameter will be approximately twice the fiber diameter. Therefore, the fibers must be bent at very small intervals.

Therefore, it is necessary to have flexibility, which at first glance seems contradictory to high strength and high elastic modulus. The inventors of the present invention have diligently investigated this problem and found that the knot strength of the monofilament is extremely important, leading to the present invention.

The monofilament in the present invention is polyethylene-2
, 6-naphthalate by melt-spinning, stretching, and optionally heat-treating.

First, polyethylene-2,6-naphthalate is melt-spun to obtain an undrawn monofilament. The polymer used for spinning is a mixed solution of phenol and orthodichlorobenzene (mixing ratio 6:4) at 35°C. The measured intrinsic viscosity [η is 0.45 or more, preferably 0.55 to
Use L and O. Those with an intrinsic viscosity [η] of less than 0.45 have a strength of 6 g/d or more and a nodule strength of 3.5.
It is difficult to obtain fibers having a g/d or higher, and fiber shavings and scum due to the loom belt and reed are likely to occur during screen gauze weaving, which is undesirable.

As the intrinsic viscosity [η] increases, the knot strength and knot elongation tend to increase, which is advantageous in preventing fiber abrasion and scum generation. For polymers, the melt viscosity is high, and the fluidity is poor and the melt viscosity is high.
It is difficult to spin a yarn of such a high quality. It may be possible to lower the melt viscosity by increasing the spinning temperature, but this would result in a decrease in molecular weight due to thermal decomposition, and its fluctuation would also increase, making it difficult to obtain uniform yarns.

Although the number of holes in the melt spinneret may be one, it is preferable to use two to four holes to simultaneously discharge, split, and wind the fibers, as productivity is higher and the intrinsic viscosity of the spun yarn [η] is less likely to decrease.

The polyethylene-2,6-naphthalate monofilament of the present invention is particularly effective when used as a monofilament with a fineness of 20 deniers or less. For high-precision printing, we use Narube (a fine-grained monofilament).
A high mesh fabric is required, and fine yarns with a fineness of less than LOd, in some cases up to about 5d, are used.

It is necessary that the breaking strength of the monofilament of the present invention is 60 g/d or more. When weaving high-modulus monofilament with an elastic modulus exceeding 170 g/d, the impact force on the fibers due to shedding, beating, wefting, etc. during weaving is much lower than that of polyethylene terephthalate fibers and nylon fibers. The threads are large and tend to break frequently.

When the breaking strength is 6 g/d or more, thread breakage during weaving can be significantly improved, and when the breaking strength is 7 g/d or more, it can be almost completely eliminated.

On the other hand, the elongation at break of the monofilament of the present invention is 3 to 3.
It is necessary that the range is 0%.

If the elongation at break is 3% or less, warp tension fluctuations and weft tension fluctuations during weaving are large, and thread breakage is likely to occur, which is undesirable. Particularly in high-speed looms where the loom rotation speed exceeds 200 revolutions/min, tension fluctuations in the warp and weft are large and yarn breakage is likely to occur. Furthermore, thread breakage is likely to occur when the gauze is stretched onto the gauze frame and during printing, which is undesirable.

By setting the elongation at break to 3% or more, the aforementioned yarn breakage can be reduced. The occurrence of yarn breakage decreases as the elongation at break increases, but since it is also related to the strength at break, it is more preferable to set it to 6% or more.

Incidentally, the higher the elongation, the better from the viewpoint of handling during weaving and scum generation. However, in order to achieve high strength and high elastic modulus, which are the objectives of the present invention, the elongation needs to be 30% or less, more preferably 15% or less.

The elastic modulus of the monofilament of the present invention must be 170 g/d or more. In screen printing, especially in high-precision screen printing of electronic circuits, materials with high elastic modulus and excellent dimensional stability are required, and in the case of polyethylene-2,6-naphthalate, the elastic modulus is 170 g/
By making it d or more, dimensional stability is greatly improved. In particular, stress relaxation can be reduced.

This is preferable because a high gauze tension can be obtained and a printing original plate with less tension relaxation can be obtained.

In this way, high-strength, high-modulus polyethylene-2,6-
Naphthalate fiber cannot be satisfactorily woven by itself. This is because if the orientation and crystallization in the fiber axis direction progresses too much, the fibers become brittle, and the surface layer is scraped off by friction during weaving, forming so-called scum that accumulates in various parts of the loom. For this purpose, a certain degree of flexibility is required, and knot strength was found to be a good indicator of this.

That is, the knot strength of the monofilament of the present invention is 3.5 g/
d or more is required. More preferably 4.
It is 2 g/d or more. If the knot strength is less than 3.5 g/d, the monofilament surface is likely to be scraped by the belt and reed blades during screen gauze weaving, making it necessary to frequently stop the machine for cleaning the reed blades. moreover,
When short fiber-like shavings become woven into a product, repair work is required to remove it, making it difficult to use it for high-precision screen printing. The inventors have discovered that polyethylene-2,6
- As a result of intensive research to maintain the high strength and high elastic modulus properties of naphthalate fibers and prevent scraping during weaving, we found that by increasing the knot strength to 3.5 g/d or more,
We discovered that it is possible to reduce the amount of scraping to a practical level. The knot strength is closely related to the fragility of the fiber; the higher the knot strength, the lower the brittleness.

In order to specifically achieve such knot strength, it is important to optimize and set the draw ratio according to the spinning speed. If the stretching ratio is low, the strength itself will not be sufficiently developed, and the knot strength will also be low. On the other hand, if the stretching ratio is too high, oriented crystallization will proceed too much and the fiber will be strong against tension in the fiber axis direction, but weak against bending, resulting in a brittle fiber.

According to studies conducted by the present inventors, it has been confirmed that the standard is represented by the density of the drawn monofilament. The density of the drawn yarn depends on the heat treatment conditions, but in order to provide the knot strength of 3.5 g/d or more required in the present invention, the density of the drawn yarn is 1.
．． 36g/cmt or less, preferably 1.345 to 1.3
This is achieved by setting it to 57 g/cmf.

Next, an example of the method for manufacturing the monofilament of the present invention will be described in the first example.
This will be explained using figures.

A polymer with an intrinsic viscosity [η] of 0.45 to 1.0 is spun at a spinning temperature of 300 to 320°C, and
Wind it up at min. to obtain an undrawn yarn. 5cm below the spinneret surface
The area above 40cm is considered a heat retention area, and the temperature of the cap surface is set to 290℃.
~Keep at ~305℃, from this point on by chimney ~10~
The fibers are cooled with air at a wind speed of 30 m/min, and then a fiber treatment agent is applied at a concentration of 0.1 to 0.5% owf by a known method.

This undrawn yarn 1 is passed through a feed roller 2 to a temperature of 130°C to
It is heated with the first heating roller 3 and the second heating roller 4 at 150°C and stretched to a predetermined magnification of 400 to 1000 m/m.
The drawn yarn 6 (monofilament) of the present invention is obtained by winding the yarn at a drawing speed of 1.5 in.

Here, the stretching between the first heating roller 3 and the second heating roller 4 may be one-stage stretching, or may be two-stage stretching using an intermediate heating roller. Note that the surface temperature of the draw roller is preferably 140° C. or less, preferably room temperature.

Alternatively, the undrawn yarn may be directly stretched and wound without being wound up once.

[Examples] The present invention will be explained in more detail below using Examples. In addition, the physical properties in Examples were measured as follows.

(A) Breaking strength and elongation samples were tested using an Instron universal testing machine at a temperature of 20°C and a relative humidity of 65%, with a sample length of 20 cm and a speed of 20 cm.
The strength and elongation at break is the measured stress strain curve under the condition of /min, and is the average value of the strength and elongation at break obtained by repeatedly measuring 10 times at an arbitrary part.

(B) It is a value calculated from the straight line portion up to the 1% elongation point of the stress-strain curve obtained by measuring the elastic modulus and strength at break.

(C) Nodule strength Measured according to JIS L 1070.

Examples 1 to 6, Comparative Examples 1 to 4 Polyethylene-2,6-naphthalene having an intrinsic viscosity of 0.62 was spun at a temperature of 305°C, with a number of holes of 2, a hole diameter of 0.5 mm, and a hole length of 0.
．． Using a 6 mm spinneret, melt spinning was carried out at a discharge rate of 13 g/min, a finishing oil of 0.3% owf was applied, and the winding speed was 1.
The fibers were separated at a speed of 000 m/min and wound up. The mouth surface temperature at this time was 300°C.

The obtained undrawn yarn was used in the drawing apparatus shown in FIG. 1 at a drawing speed of 800 m/mjn and the drawing ratio and drawing temperature were varied to obtain monofilaments shown in Table 1. Note that the draw roller was kept at room temperature.

Using a flat steel belt for screen gauze weaving, the stretched monofilament was brought into contact with the mail part of the flat steel belt, and the monofilament was bent at a bending angle of 180' and a static time series tension of 1.5 g/d, 150
It was rubbed at one stroke per minute and the number of strokes required to break was measured.

Table 1 shows the average value of the values measured 10 times.

Further, 400 monofilaments were arranged on this drawn monofilament at a tension of 10 to 1427, and rubbed with a mesh screen gauze weaving reed at 400 strokes/10, and the amount of white powder scum generated on the reed was observed with the naked eye.

(The following is a blank space) In Table 1, Example 1 that satisfies the requirements stipulated in the present invention,
2, 3, 4. 5.6 was a high-strength, high-modulus monofilament that had a large number of strokes to break due to stroke friction with a flat still belt, had excellent abrasion resistance to metals, and produced a small amount of white powder scum on the reed. On the other hand, although Comparative Example 1 has excellent abrasion resistance against metal due to stroke abrasion, the amount of white powder scum generated in the reed is slightly higher than that of the monofilament of the present invention, and the surface quality of the gauze is inferior. Ta.

In addition, in Comparative Examples 9 and 10, the wear resistance against metal due to stroke abrasion was extremely poor, a large amount of white powder scum was generated on the reed, and some of them broke in a short period of time.

[Effects of the Invention] Since the monofilament of the present invention has high strength and high elastic modulus, it can be easily made into a high-tension screen gauze. In particular, by having a high modulus of elasticity, it is possible to reduce off-contact during screen printing to 2 mm or less, making it suitable for high-precision printing.

Furthermore, since the glass transition point temperature is as high as 125°C, the dimensional stability against temperature changes in the printing room is excellent, and the tension relaxation of the printing original plate is also small. It is a figure showing an example.

undrawn yarn 2: Feed roller 3: First heating roller 4: Second heating roller 5. Draw roller 6: Stretched yarn

Claims (1)

[Scope of Claims] A monofilament made of polyethylene-2,6-naphthalate monofilament satisfies the following (a) to (c) at the same time, and has a knot strength of 3.5 g/d or more. Polyethylene for screen gauze-2
, 6-naphthalate monofilament. (B) 6.0≦Strength at break (g/d) (B) 3≦Elongation at break (%)≦30 (C) 170≦Modulus (g/d)