JP2887380B2 - Highly shrinkable polyphenylene sulfide monofilament and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-shrinkable polyphenylene sulfide monofilament having properties particularly suitable for a spiral canvas fabric for papermaking and a method for producing the same.

[0002]

2. Description of the Related Art Polyphenylene sulfide is a polymer which is excellent in heat resistance and chemical resistance and can be melt-molded. Therefore, in addition to so-called molded article applications, techniques for application to fibers and films have been studied. For the production of fibers, see, for example, U.S. Pat. Nos. 1,895,091; 54
617, JP-B-52-12240, JP-B-52-30609, JP-A-57-143518, JP-A-58-18409, and JP-A-57-1
43518, JP-A-58-18409, JP-A-58-31112 and JP-A-61-758.
No. 12, etc.

A technique for applying a monofilament made of polyphenylene sulfide to a canvas fabric for papermaking by utilizing its excellent properties is also disclosed in Japanese Patent Application Laid-Open No. Sho 6 (1988).
It is proposed by JP-A-6390.

On the other hand, in the papermaking industry in recent years, there has been an increasing movement to produce economically efficient and higher quality paper. In order to satisfy these requirements, weaving canvas fabric for papermaking has been required. Improvement of the organization itself is considered first.

[0005] That is, the general weaving structure of the conventional canvas fabric for papermaking includes plain weaving, satin weaving, twill weaving, double weaving, and triple weaving. These weaving structures satisfy the above requirements. There was a limit.

[0006] On the other hand, among the weaving structures, a spiral weaving structure is considered to be the most suitable as a weaving structure for obtaining economically efficient and higher quality paper. This spiral weave is completely different from the above-mentioned general weave structure, and the contact surface between the woven fabric and the paper to be made is kept almost flat, and the drying efficiency of the paper is high. The beauty of the surface and the homogeneity of the whole paper are particularly excellent, and can give high-quality paper.

However, the monofilament constituting the spiral weave has a dry heat shrinkage measured in a free state,
For example, it is required to be as high as 15 to 32% at 200 ° C. In other words, spiral weaving is generally made by winding a monofilament around a spindle to form a spiral yarn and weaving it. At this time, in order to develop uniform and stable shaping properties, the monofilament has a sufficiently high height. Shrinkability is required.

In the papermaking canvas, polyethylene terephthalate (PET) is one of the most frequently used materials at present.

Here, when comparing PET and polyphenylene sulfide, polyphenylene sulfide is
Although it is a polymer that is extremely difficult to achieve high shrinkage as compared with ET, it is a polymer that can easily achieve low shrinkage. Specifically, the dry heat shrinkage at 200 ° C. of the fiber produced under normal conditions is at most about 7 to 8% in the case of polyphenylene sulfide, and the fiber greatly exceeding 10% has not been realized. Is the current situation.
On the other hand, in the case of PET fiber, a fiber having a dry heat shrinkage at 200 ° C. of 15 to 18% can be easily obtained under ordinary spinning conditions.

In addition, the monofilament constituting the spiral weave has a high dry heat shrinkage at a high temperature of, for example, 200 ° C. and a dry heat shrinkage at around 140 ° C. which is a practical temperature when used for papermaking. Similarly, it is required that the heat shrinkage at 200 ° C.
It is also required that the absolute value of the difference from the dry heat shrinkage at 0 ° C. is small, but polyphenylene sulfide monofilament has a low dry heat shrinkage at 200 ° C., and also has an absolute value of the difference in shrinkage. Because of the large tendency, application to spiral canvas for papermaking canvas was also hesitant.

Further, in order to increase the dry heat shrinkage of polyphenylene sulfide monofilament,
The strength tended to decrease, and it was also difficult to achieve both high dry heat shrinkage and high strength.

As described above, polyphenylene sulfide monofilaments have excellent properties as a papermaking canvas as described above, but in the prior art, monofilaments having a high dry heat shrinkage and a high tensile strength are produced in a balanced manner. In fact, the application to papermaking canvases made of spiral weave was limited because of the inability to do so.

[0013]

SUMMARY OF THE INVENTION The present invention has been achieved as a result of studies in view of the above-mentioned conventional circumstances.

Accordingly, an object of the present invention is to provide a polyphenylene sulfide monofilament having extremely high shrinkage and having sufficient strength, and particularly suitable for a spiral canvas for papermaking, and to establish a stable production method of the monofilament. It is in.

[0015]

In order to achieve the above-mentioned object, the high-shrinkable polyphenylene sulfide monofilament of the present invention comprises p-phenylene sulfide units in which at least 85 mol% of the constituent units are present, and has a melt flow rate of 20%. Is a monofilament having a diameter of 0.20 to 0.80 mm obtained by spin-drawing polyphenylene sulfide of about 120 to 120 ° C., and a dry heat shrinkage Sd200 at 200 ° C. measured in a free state, and a dry heat shrinkage measured at 140 ° C. The absolute value of the difference from the ratio Sd140 △ Sd (Sd200−Sd140
) Is 3.0% or less, the Sd200 is 15 to 32%, and the strength is 3.5 g / d or more.

In the method for producing a high-shrinkable polyphenylene sulfide monofilament of the present invention, melt-extrusion spinning of polyphenylene sulfide having a melt flow rate of 20 to 120, comprising at least 85 mol% of constituent units of p-phenylene sulfide unit. When the spun yarn is cooled and then subjected to two-stage drawing, the first-stage drawing temperature T1 is set to be higher than the glass transition point (Tg) of polyphenylene sulfide by 3%.
And the second-stage stretching temperature T2 is controlled to be 5 to 55 ° C higher than the above-mentioned Tg and T2 ≧ T1, and the second-stage stretching ratio is set to the second-stage stretching ratio / total stretching. It is characterized in that the magnification ratio is regulated to be in the range of 0.22 to 0.28.

First, the method for producing the highly shrinkable polyphenylene sulfide monofilament of the present invention will be described in detail, and then the performance of the obtained polyphenylene sulfide will be described.

The polyphenylene sulfide used in the present invention is a polymer in which at least 85 mol% of the structural units are composed of p-phenylene sulfide units, and may contain other copolymer components in the range of 15 mol% or less. In addition, when the p-phenylene sulfide unit is less than 85 mol%, heat resistance is unfavorably deteriorated.

Further, the polyphenylene sulfide used may contain a heat-resistant agent, a weathering agent, a light-proofing agent, an antistatic agent, a dye, a pigment and a small amount of a crosslinking component such as trichlorobenzene.

The polyphenylene sulfide used in the present invention has a polymer melt flow rate measured by JIS K-6900: a melt flow rate (hereinafter referred to as MFR) in the range of 20 to 120, particularly 50 to 100. is important.

The MFR of polyphenylene sulfide is 1
If it is more than 20, the tensile strength of the obtained monofilament is lowered, and if it is less than 20, the viscosity is too high to require special spinning conditions and the spinning properties are remarkably deteriorated.

In the method of the present invention, polyphenylene sulfide is first melt-extruded from a spinneret, but the spinning conditions are not particularly limited. The melt extrusion temperature is usually 20 to 60 ° C. higher than the melting point of the polymer, particularly 30 to 50 ° C.
C. higher temperatures are preferred.

The melt spun yarn is then cooled and solidified in warm water at 60 ° C. or higher. Here, the cooling temperature is 60 ° C.
If the cooling rate is too low, the running speed of the yarn becomes unstable because the cooling rate is too high, and furthermore, uniform drawing becomes impossible, and the strength level of the obtained monofilament is unfavorably reduced. Therefore, the cooling temperature is particularly preferably 5 to 20 ° C. lower than the Tg of polyphenylene sulfide.

The obtained undrawn monofilament is subsequently subjected to a two-step drawing step. In order to obtain the high-shrinkable polyphenylene sulfide monofilament of the present invention, the drawing temperature in this two-step drawing is set to be lower than that of the conventional one. It is important that the temperature is also in a low temperature range, and that the stretching temperature, particularly the second-stage stretching ratio, is strictly controlled as described below.

First, the first-stage stretching temperature T1 is set at the glass transition point (hereinafter, Tg) of the polyphenylene sulfide used.
3 to 15 ° C. higher, especially 5 to 10 ° C.
High temperature range. Here, the first-stage stretching temperature T1 is (T
(Tg + 3 ° C.), the drawing tension is remarkably increased, thereby deteriorating the spinnability.

Here, the polyphenylene sulfide T
g means a sample amount of 15 mg using a differential calorimeter (DSC),
This is a value measured under the condition of a temperature rising rate of 10 ° C./min.

As the first-stage stretching atmosphere, a warm water bath, a dry heat bath, a steam bath, or the like is used, and the first-stage stretching ratio is usually in the range of 3.5 to 4.4 times.

Next, the second-stage stretching is performed. The second-stage stretching temperature T2 is determined by adjusting the T of the polyphenylene sulfide to be used.
It is necessary to control the temperature to be higher than the temperature by 5 to 55 ° C., particularly 5 to 35 ° C., and to satisfy T2 ≧ T1.

That is, when the second-stage stretching temperature T2 is (Tg +
If the temperature is less than 5 ° C.), the dry heat shrinkage ratio is improved, but not only a sufficient draw ratio cannot be obtained, but also a decrease in strength,
Yarn breakage or the like may occur, resulting in a decrease in the spinning property, and (Tg + 55
C.), high strength can be achieved, but the dry heat shrinkage is extremely low, which is not preferable.

Further, when T2 is lower than T1,
Although a high dry heat shrinkage ratio can be obtained, the strength is significantly reduced, which is not preferable.

As the second-stage stretching atmosphere, a dry heat bath is most preferably employed, and the stretching ratio in the second-stage stretching is such that the ratio of the second-stage stretching ratio / total stretching ratio is 0.22 to 0.
It is necessary to regulate to be in the range of 28. Here, if the ratio of the second-stage stretching ratio / total stretching ratio is less than 0.22, it is difficult to increase the strength, and if it exceeds 0.28, the stretching ratio is too high, causing troubles such as yarn breakage, It is not preferable because the spinning property is reduced.

The drawn polyphenylene sulfide monofilament can be subjected to a heat setting treatment if necessary. In this case, the heat setting temperature must be controlled so as not to exceed T2.

The obtained polyphenylene sulfide monofilament has a cross-sectional shape of usually a perfect circle, but is not limited thereto, and may have an irregular cross-section or a rectangular or elliptical cross-section.

The thus obtained highly shrinkable polyphenylene sulfide monofilament of the present invention has the following excellent properties.

That is, the highly shrinkable polyphenylene sulfide monofilament of the present invention has a dry heat shrinkage Sd200 of 200 ° C. measured in a free state and a 140 ° C.
Absolute value of the difference from the dry heat shrinkage Sd140 measured in step △ Sd
(Sd200-Sd140) is 3.0% or less,
Is 15 to 32% and the strength is 3.5 g / d or more.
It is maintained over a wide diameter range of 0 mm, especially 0.40 to 0.70 mm.

It should be noted that the temperature of 140.degree.
The dry heat shrinkage ratios Sd200 and Sd140 at a temperature of 140 ° C. are obtained by placing a sample length L0 under a load of 0.05 g / d on a monofilament before dry heat treatment, placing the sample in a dry state in dry hot air at 140 ° C. Alternatively, when the sample length measured by applying a load of 0.05 g / d to the monofilament after being subjected to the dry heat treatment at 200 ° C. for 30 minutes is defined as L 1, L 0 −L 1 /
It is a value obtained by the formula of L0 × 100.

The polyphenylene sulfide monofilament of the present invention has an unprecedented Sd200 of 15 to 32%.

Further, the polyphenylene sulfide monofilament of the present invention has Sd200 and dry heat shrinkage Sd1.
The absolute value △ Sd (Sd200-Sd140) of the difference from 40 is 3.0% or less, and the difference in shrinkage between the high temperature side and the low temperature side is extremely small.

Here, the absolute value △ Sd of the difference in shrinkage ratio indicates the shaded portion shown in FIG. That is, in FIG. 1, the dry heat treatment temperature is shown on the horizontal axis, and the dry heat shrinkage measured in the free state is shown on the vertical axis, and the polyphenylene sulfide monofilament of the present invention is 140 to 200.
In the dry heat treatment temperature range of ° C., ΔSd is as small as 3% or less on both the positive side and the negative side.

The ΔSd characteristic is, for example, 20 which is originally required for a monofilament for forming a spiral weave.
It means that the dry heat shrinkage at a high temperature of 0 ° C. is high, and the dry heat shrinkage at a practical temperature (140 ° C.) when used as a papermaking canvas is also high, and polyphenylene sulfide is used as a papermaking spiral. This can be said to be a very convenient property to apply as a canvas weave.

Further, the polyphenylene sulfide monofilament of the present invention has a high strength of 3.5 g / d or more as measured according to JISL1013-1981, and is therefore excellent as a spiral canvas for papermaking. Has characteristics.

[0042]

The configuration and effects of the present invention will be further described with reference to examples.

Examples 1 to 6 and Comparative Examples 1 to 6 Polyphenylene sulfide (E1880, manufactured by Toray Phillips) having an MFR of 70 and a Tg of 90.5 ° C.
It was melted at 330 ° C. by an extruder spinning machine having a diameter of mm and extruded from a die having a hole diameter of 1.7 mm.

The spun yarn was immediately introduced into a hot and cold water bath at 80 ° C., cooled, then subjected to first-stage drawing in a steam bath at 98 ° C., and subsequently to a dry heat bath at a temperature shown in Table 1. Was used to perform the second-stage stretching.

The second-stage stretching ratio was changed as shown in Table 1, the total stretching ratio was fixed at 5.10 times, and the ratio of the second-stage stretching ratio / total stretching ratio was as shown in Table 1. .

At this time, the discharge amount per one hole of the base is 30.
3 g / min, and the diameter of the obtained monofilament was 0.60 mm.

After the completion of the stretching, a constant-length heat setting treatment was performed at the same temperature as the second-stage stretching temperature.

The results of evaluating the physical properties of the obtained polyphenylene sulfide monofilament are also shown in Table 1.

Under the conditions of Comparative Examples 2, 4, and 6, yarn breakage occurred frequently and the yarn-making properties were unstable.

[0050]

[Table 1] As is evident from the results in Table 1, according to the method of the present invention, a polyphenylene sulfide monofilament having an excellent balance between dry heat shrinkage and strength and suitable performance as a spiral canvas for papermaking can be obtained.

Examples 7-9, Comparative Examples 7-8 Except that the second stage stretching ratio / total stretching ratio was fixed at 0.25 and the second stage stretching temperature was changed as shown in Table 2, In the same manner as in Examples 1 to 6, polyphenylene sulfide monofilaments having a diameter of 0.60 mm were obtained.

The results of evaluating the physical properties of the obtained polyphenylene sulfide monofilament are also shown in Table 2.

[0053]

[Table 2] As is evident from the results in Table 2, according to the method of the present invention, polyphenylene sulfide monofilaments having excellent dry heat shrinkage and strength and having suitable properties as a spiral canvas for papermaking can be obtained.

[0054]

As described in detail above, the polyphenylene sulfide monofilament of the present invention has an extremely high shrinkage, has a sufficient strength, and has properties particularly suitable for a spiral canvas for papermaking.

Further, according to the method of the present invention, a polyphenylene sulfide monofilament having the above performance can be stably manufactured.

[Brief description of the drawings]

FIG. 1 is a graph showing an absolute value range of a difference between dry heat shrinkage rates at 200 ° C. and 140 ° C. in the present invention.

Claims (2)

(57) [Claims] 1. A monofilament having a diameter of 0.20 to 0.80 mm obtained by spin-drawing polyphenylene sulfide having a melt flow rate of 20 to 120, wherein at least 85 mol% of the constituent units are composed of p-phenylene sulfide units. The dry heat shrinkage Sd200 measured at 200 ° C. in the free state and the dry heat shrinkage S measured at 140 ° C.
The absolute value ΔSd (Sd200−Sd140) of the difference from d140 is 3.0% or less, the Sd200 is 15 to 32%, and the strength is 3.5 g / d or more. Shrinkable polyphenylene sulfide monofilament. 2. A polyphenylene sulfide having a melt flow rate of 20 to 120, wherein at least 85 mol% of the constituent units are composed of p-phenylene sulfide units, are melt-extruded and spun. The first-stage stretching temperature T1 is 3 to 15 ° C. higher than the glass transition point (Tg) of polyphenylene sulfide, the second-stage stretching temperature T2 is 5 to 55 ° C. higher than the Tg, and T2 ≧ T1. And the ratio of the second-stage stretching ratio / the total stretching ratio is 0.22 to 0.28.
The method for producing a high-shrinkable polyphenylene sulfide monofilament having the characteristics according to claim 1, wherein the content is regulated to fall within the range of: