JP2562350B2 - Heat resistant composite fiber and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyvinylidene fluoride-based composite fiber with improved heat resistance, more specifically, a polyvinylidene fluoride-based resin (hereinafter, “PVDF-based resin”). Abbreviated as) sheath layer (surface layer)
And a polyarylene sulfide resin (hereinafter, abbreviated as “PAS resin”) in a core layer (inner layer).

[Conventional technology]

Fibers made from PVDF-based resins (hereinafter referred to as "PVDF-based fibers") have excellent weather resistance, chemical resistance, water resistance, mechanical properties such as tensile strength, flex fatigue resistance, and high It has knot strength and is used as a fiber for various chemical and fish industry materials such as fish nets, filters, meshes, hoses, and woven fabrics for reinforcement.

By the way, the melting point of the PVDF resin varies depending on the molecular weight and the type of the copolymerization component, and ranges from low melting point to high melting point, but even the high melting point is usually in the range of about 165 to 185 ° C. , Insufficient heat resistance. So PVDF
When the system fibers are used under high temperature conditions, the temperature range in which they can be continuously used is only up to about 120 to 130 ° C.
In a high temperature atmosphere above ℃, the strength decreases and it becomes unusable.

Here, the temperature range in which continuous use is possible refers to a temperature range in which the tensile strength after heating the fiber for 1000 hours is 50% or more of the initial value (tensile strength before heating). Given the high strength properties of PVDF fiber, a 50% retention level of tensile strength allows it to be used in normal applications.

Conventionally, in order to improve the physical properties of PVDF-based fibers, it is known to use PVDF-based resins to form sheath-core type composite fibers.
For example, JP-B-60-24846 describes that a composite fiber having excellent knot strength can be obtained by using a PVDF resin for the sheath and a polyamide for the core.
Further, in JP-A-59-144614, both sheath and core are made of PVDF type resin, the logarithmic viscosity of the core is 1.10dl / g or more,
A PVDF composite yarn having a high knot strength, which is a composite yarn having an apparent viscosity of a sheath portion smaller than that of a core portion, is described. However, these PVDF-based composite fibers are insufficient in terms of improving heat resistance.

On the other hand, polyphenylene sulfide resin (hereinafter "PPS
PAS resin represented by "resin") has a high melting point of about 280 ° C and is excellent in heat resistance, and the fiber produced from PAS resin has a high temperature range of about 180 to 190 ° C that can be continuously used. . In addition, PAS fiber has excellent chemical resistance and excellent resistance to acids and alkalis. However, PAS
The fibers have a low knot strength and are easier to cut than the knots, which makes it difficult to make a net. In particular, those having a knot elongation of less than 10% are brittle and difficult to make a net.

[Problems to be Solved by the Invention]

An object of the present invention is to obtain a composite fiber having improved heat resistance while maintaining the excellent chemical resistance, strength characteristics, knot strength and the like of PVDF fibers.

Furthermore, the object of the present invention is to dispose PVDF resin in the sheath layer,
By disposing a resin having excellent heat resistance in the core layer, it is possible to obtain a composite fiber having improved heat resistance while maintaining the excellent properties of the PVDF fiber such as high knot strength.

As a result of intensive studies to overcome the problems of the above-mentioned conventional techniques, the present inventors have found that in a sheath-core type composite fiber having a sheath layer and a core layer, PVDF resin is arranged in the sheath layer and PAS is used in the core layer. It has been found that by disposing a resin, it is possible to maintain excellent properties of the PVDF fiber while improving the net-forming property and to improve the heat resistance, and based on this finding, the present invention has been completed.

[Means for solving the problem]

According to the present invention, the logarithmic viscosity (ηinh) is 0.7 to 1.4 dl / g.
With a sheath layer made of polyvinylidene fluoride resin having a melting point of 165 to 185 ° C and a melt viscosity of 1000 to 10000 poise (value measured at 310 ° C, shear rate of 1200 / sec), Provided is a heat-resistant composite fiber comprising a core layer made of a chain-like polyarylene sulfide resin and having a core layer cross-sectional area ratio of 20 to 60 ° C.

Further, according to the present invention, the melt viscosity is 1000 to 10000 poise (value measured at 310 ° C., shear rate of 1200 / sec).
And a logarithmic viscosity (ηinh) of 0.7 to 1.4 dl / g and a melting point of 1 around the substantially linear polyarylene sulfide resin.
After melt extruding so as to cover the polyvinylidene fluoride resin at 65 to 185 ° C. and performing composite melt spinning, the obtained composite fiber is stretched at a stretching ratio of 3 to 8 in an atmosphere of 80 to 180 ° C., Then, comprising a sheath layer made of polyvinylidene fluoride resin characterized by heat setting at 150 ~ 270 ℃, and a core layer made of polyarylene sulfide resin, and,
Provided is a method for producing a heat resistant composite fiber having a core layer having a cross-sectional area ratio of 20 to 60%.

Thus, according to the present invention, a screen in various chemical industry fields, fiber performance such as knot strength suitable for netting into mesh, etc., chemical resistance, etc., and a composite with improved heat resistance Fibers can be provided.

 The constituent elements of the present invention are described in detail above.

(PVDF Resin) The PVDF resin used in the present invention is a polyvinylidene fluoride homopolymer, a copolymer containing vinylidene fluoride as a main component, or a blend containing any of these as a main component. Here, as the copolymer, 70 mol% or more of vinylidene fluoride monomer and a monomer copolymerizable with vinylidene fluoride, for example, ethylene trifluoride, ethylene tetrafluoride,
A copolymer with 30 mol% or less of a vinyl halide monomer such as ethylene monochloride trifluoride, propylene hexafluoride, vinyl fluoride, etc., in particular, a copolymerization monomer up to 10 mol%,
More preferably, a copolymer containing up to 5 mol% is preferably used.

Among the PVDF-based resins, a polyvinylidene fluoride homopolymer alone or a composition containing 95% by weight or more of the polyvinylidene fluoride homopolymer is particularly preferably used.
Polyvinylidene fluoride having a high degree of crystallinity is preferable, and one obtained by polymerizing vinylidene fluoride at a temperature of 60 ° C. or lower, preferably 30.5 ° C. or lower which is the critical temperature of vinylidene fluoride is preferable.

As constituents of the composition, additives such as stabilizers, ultraviolet absorbers, pigments, crystal nucleating agents and processing aids are used.

The PVDF resin used in the present invention has a logarithmic viscosity (ηinh)
Is in the range of 0.7 to 1.4 dl / g.

The logarithmic viscosity (ηinh) is dimethylformamide as a solvent, the dissolution concentration of PVDF resin is 0.4g / dl, temperature 3
It is the value measured under the condition of 0 ° C.

In the present invention, the reason for using a PVDF resin having an inherent viscosity of 0.7 to 1.4 dl / g is extrudability, spinnability, excellent moldability such as drawability, and composite fiber excellent in mechanical strength. Because you can get

If the logarithmic viscosity of the PVDF resin is too low, the mechanical strength of the resulting composite fiber, particularly the knot strength, will be low, and the net-forming property will be poor. And, such a low viscosity PVDF resin is insufficient to overcome the disadvantage of PAS resin, which is low knot strength, by forming a composite structure. Conversely, if the logarithmic viscosity of the PVDF resin is too high and high, the viscosity difference with the relatively low viscosity PAS resin becomes large, and the PAS resin stabilizes the inner layer (core layer) during composite spinning. Is difficult to flow, and the spinnability is poor.

The PVDF resin used in the present invention has a high melting point (Tm) of 165 to 185 ° C. from the viewpoint of heat resistance and mechanical strength. Two or more PVDF resins may be blended for use, but the logarithmic viscosity of the blend must be in the range of 0.6 to 1.6.

(PAS Resin) The PAS resin used in the present invention is a repeating unit of p-phenylene sulfide as a main constitutional unit of the polymer. Is 50% by weight or more, more preferably 70% by weight or more, and further preferably 90% by weight or more. Among them, polyarylene sulfide having a substantially linear structure is more preferable because it has good spinnability and stretchability. Here, the term “substantially linear structure” does not mean a polymer obtained by a treatment for increasing melt viscosity (curing) by oxidative crosslinking, but a polymer obtained from a monomer mainly containing a difunctional monomer. Say. However, as long as stable spinnability and stretchability are not impaired, a partially crosslinked structure or a cured product may be used.

Corresponding to a p-phenylene sulfide unit content of 50% by weight or more, the PAS resin may contain less than 50% by weight of other copolymerized constitutional units. Examples of such a constitutional unit include, for example, a metaphenylene sulfide unit. Diphenyl ketone sulfide unit, Diphenyl sulfone sulfide unit Diphenyl sulfide unit Diphenyl ether sulfide unit 2,6-naphthalene sulfide unit Trifunctional unit And the like.

In the above PAS resin, the polymer having a high melt viscosity described later is
For example, it can be produced by a known method as described in JP-A-617332.

In addition, a block copolymer containing a p-phenylene sulfide repeating unit as a main component, for example, Repeating unit 70-95 mol% and metaphenylene sulfide Repeating unit A block copolymer containing 5 to 30 mol% of B in a block form can also be preferably used from the viewpoint of physical properties as well as processability in spinning and stretching. Such a block copolymer having a high melt viscosity can be produced, for example, by a known method described in JP-A-61-14228.

The PAS resin used in the present invention preferably has a relatively high viscosity, and has a melt viscosity of 1000 poise or more, preferably 2000 poise or more, measured at 310 ° C. and a shear rate of 1200 / sec. The upper limit of melt viscosity of PAS resin is about 10,000 poise. The melt viscosity of PAS resin is PVDF that constitutes the sheath layer.
It is desirable that the viscosity be close to the viscosity of the system resin, but if the viscosity is too high, poor appearance such as melt fracture tends to occur on the surface of the spun yarn, which is not desirable.

If the melt viscosity of the PAS resin is lower than 1000 poise, the viscosity difference between the two is large during composite spinning with the PVDF resin, and stable spinning is difficult. If it exceeds 10,000 poises, the PAS resin contains a considerable proportion of cross-linked parts, which causes clogging of the filter for removing foreign matters and development that reduces the spinnability of the spun yarn, which hinders stable spinning. There is a risk of coming.

Melt viscosity is measured by Toyo Seiki "Capirograph"
(1B type), hole diameter 1.0mmφ (D) × length 10.0mmφ
(L), using a nozzle with an inflow angle of 90 ° (material tungsten carbide). The measurement method is to press the raw material powder at 320 ° C. and 60 kg / cm ² for 40 seconds to make a sheet, and cut the sheet into small pieces. this
After drying at 150 ° C. for 1 hour, the capyrograph cylinder is filled. After the preheating time including the pressure filling and the degassing operation is set to 5 minutes, the plunger is lowered at a constant pressure to extrude the molten resin from the nozzle.

Using the pressure of the plunger ΔPkg / cm ² and the discharge rate Qcm ³ / sec obtained from the descending speed of the plunger, the melt viscosity ηa is obtained from the following equation.

* G: Gravity acceleration (980 cm / sec ² ) (Composite fiber) The composite fiber of the present invention is a fiber having a composite structure in which PVDF resin is arranged in the sheath layer and PAS resin is arranged in the core layer. Inner layer P
The cross-sectional area ratio of AS resin is 20 to 60% of the whole composite fiber. When the cross-sectional area ratio of PAS resin is less than 20%, the heat resistance is slightly improved compared with the case of using PVDF resin alone,
On the other hand, if it exceeds 60%, the mechanical properties such as knot strength and knot elongation of the PVDF resin of the sheath layer are not expressed, and the workability such as net-making property is deteriorated.

The composite structure of the composite fiber of the present invention comprises at least a two-layer structure of a sheath and a core, wherein the sheath layer is a PVDF resin and the core layer is
There is no particular limitation as long as it is a PAS resin. As a specific example, the horizontal cross section of the composite fiber is a concentric sheath core type in which the sheath layer and the core layer have a concentric circular structure, and the core layer has a shape other than a circular shape such as a triangle, a quadrangle, or a star shape. Molds, multi-core type having many core layers in the sheath layer, and the like. The shapes of the sheath layer and the core layer can be adjusted to desired shapes by changing the shape of the sheath-core composite yarn nozzle used during melt spinning. Further, a structure or the like in which the shape between the sheath layer and the core layer continuously changes can be arbitrarily adopted. However,
A two-layer structure of a sheath and a core is preferably used from the viewpoint of ease of processing.

It is not particularly necessary to provide an adhesive layer at the interface between the PVDF resin of the sheath layer and the PAS resin of the core layer, but it may be provided if desired.

The size of the conjugate fiber (thread diameter) is not particularly limited and may be appropriately determined according to the purpose of use, but is usually 10 μm to
It is 2 mm.

(Method for producing conjugate fiber) As a method for producing the conjugate fiber of the present invention, a usual composite melt spinning method can be adopted. For example, by using a composite yarn nozzle having a structure corresponding to the composite structure of the various sheaths and cores described above, PVD-based resin and PAS resin are co-extruded by PVD.
Composite melt spinning is performed so that the F-based resin constitutes the sheath layer and the PAS resin constitutes the core layer.

Coextrusion is carried out by melt-extruding each resin with an extruder. In that case, the melt-extrusion temperature is 250 to 320 ° C for PVDF resin and 290 to 350 ° C for PAS resin.

The spun yarn is usually introduced into water at 10 to 80 ° C and cooled.
The conditions of this cooling temperature must be selected appropriately according to the desired diameter of the yarn. It is better to set the thread with a small diameter to a low temperature and the thread with a large diameter to a high temperature. As the refrigerant, water containing glycerin, alcohol, etc. may be used.
By adding these, you can raise the boiling point of the refrigerant,
Further, it is possible to improve the cooling effect by improving the wettability. In the case of thin yarn such as multifilament, air cooling is also possible.

After cooling, the composite yarn is continuously drawn in an atmosphere (dry heat or wet heat) of 80 to 180 ° C. at a draw ratio of 3 to 8 times. After that, in an atmosphere (dry heat or wet heat) of 150 to 270 ° C., preferably 160 to 230 ° C., it is stretched to a length of 0.8 to 2 times, fixed length or relaxed, and heat set.

Examples of the dry heat atmosphere include hot air and a hot plate, and examples of the wet heat atmosphere include a boiling water bath and a glycerin bath.

The reason why the stretching temperature is 80 to 180 ° C. is that if it is lower than 80 ° C., the PVDF layer is likely to be fibrillated, and if it exceeds 180 ° C., the degree of orientation of the PVDF layer is lowered and the strength is lowered.

The reason for setting the draw ratio to a total of 3 to 8 times is that if the draw ratio is lower than 3 times, the PVDF layer will have a constricted part and the appearance will be impaired.
This is because if it is more than double, there is a problem in practical use due to stretching breakage, delamination and the like.

The reason for heat setting at 150 to 270 ℃ is that it is less than 150 ℃ 1
This is because the heat-resistant strength retention rate decreases at 50 ° C. or higher, and if it exceeds 270 ° C., it tends to melt and the drawn yarn is difficult to obtain. Further, the preferable heat setting temperature differs depending on the ratio of the PVDF resin and the PAS resin, but when there are many PVDF resins, it is desirable to select a temperature close to 150 ° C.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1 (1) PVDF resin for sheath layer Polyvinylidene fluoride homopolymer having an inherent viscosity (ηinh) of 1.10 dl / g was extruded at 230 ° C to obtain pellets. The melting point of this polymer was 178 ° C. (DSC: measured at a temperature rising condition of 10 ° C / min).

(2) PAS resin for core layer Synthesis of PPS resin 11.0 kg of N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) and hydrous sodium sulfide (purity 46% by weight, manufactured by Nagao Soda Co., Ltd.) in a 20-liter autoclave. Charge 4.239 kg and gradually stir in a nitrogen atmosphere for about 2 hours with stirring
Heat up to 203 ℃, water 1.585Kg, NMP 1.96Kg and 0.58
Molar hydrogen sulfide was distilled off.

After cooling to 130 ° C., 3.59 kg of p-dichlorobenzene (hereinafter abbreviated as p-DCB) and 3.17 kg of NMP are added,
Polymerization was carried out by heating at 215 ° C for 8 hours. Then 1.275 kg of water
Was added, the temperature was raised to 265 ° C. in a nitrogen atmosphere, and polymerization was performed for 4 hours. After cooling, the obtained polymer is filtered off from the oligomer and the like, and then repeatedly washed with deionized water,
It was dried under reduced pressure at 100 ° C.

The polymer obtained was poly-p-phenylene sulfide (PPS resin) and had a melt viscosity of 3000 poise (310 ° C,
It had a high shear rate of 1200 / sec) and a melting point Tm of 282 ℃. This polymer was melt extruded at 330 ° C. to obtain pellets.

The above two resin pellets were extruded from each (35 mmφ) extruder at 280 ° C. for the former and 340 ° C. for the latter, and introduced into a concentric sheath-core type composite yarn nozzle, and the sheath layer was polyvinylidene fluoride and the core layer was Composite melt spinning was performed from a 0.8 mmφ nozzle hole as PPS resin. This was air-cooled and taken up by a bobbin at 100 m / min.

This yarn was drawn 3.5 times on a hot plate (surface temperature 110 ° C.), and then heat set on the hot plate (surface temperature 240 ° C.) under a fixed length of 1 time. The diameter of the obtained yarn was 30 μm, and it was a composite fiber having a structure in which the cross-sectional area ratio of the sheath layer to the core layer was 50% of the sheath layer and 50% of the core layer.

The tensile strength of this composite fiber is 51.5 kg / mm ² (elongation 31.0
%), And the knot strength was 31.5 kg / mm ² (nodule elongation 12.0%).

The tensile strength after leaving this composite fiber for 1000 hours in a gear open at 160 ° C was 35.8kg / mm ² (retention rate 70.2%),
The knot strength was 14.5 kg / mm ² (retention rate 46.0%).

Measurement method Measurement of knot strength and knot elongation, using a Toyo Baldwin Co., Ltd. Tensilon UTM-III type, when the filament of the test length 300 mm having a knot point at the center of the test length was pulled at a pulling speed of 300 mm / min. The breaking strength and knot elongation at room temperature.

The measurement conditions for tensile strength and elongation are the same as those for knot strength and knot elongation, except that no knot points are provided.

The above measurement environment conditions are in accordance with JIS L-1013, 23
The conditions were ℃ and 65% RH.

Comparative Example 1 The polyvinylidene fluoride homopolymer pellets used in Example 1 were extruded at 280 ° C., spun through a 0.8 mmφ nozzle, air-cooled, and taken at 100 m / min.

This was stretched and heat-set under the same conditions as in Example 1 to produce a stretched yarn.

This yarn diameter is 30 μm, tensile strength is 50.0 kg / mm ² (elongation is 38.0
%), And the knot strength was 43.0 kg / mm ² (knot elongation 31.0%).

After this was left for 1000 hours in a gear oven at each temperature shown in Table 1, the tensile strength and knot strength were measured.

As is clear from Table 1, the temperature range in which the PVDF fiber can be continuously used is up to about 130 ° C., and in the temperature range over that range, the tensile strength and the knot strength rapidly decrease.

Comparative Example 2 The PPS resin used in Example 1 was extruded with the same equipment as in Example 1 while changing the discharge rate, and was taken out at 100 m / min. This was drawn and heat-set under the same conditions to obtain a drawn yarn.

The diameter of this drawn yarn was 30 μm, and the physical properties of this single yarn were tensile strength 54.0 kg / mm ² (elongation 23.0%) and knot strength 22.0 kg / mm ² (knot elongation 4.0%).

This was left to stand in a gear oven at 160 ° C. for 1000 hours, and the strength was measured. Its tensile strength is 53.8 kg / mm ² (holding rate 99.6
%) (Elongation 21.0%), knot strength 18.0 kg / mm ² (holding ratio 81.2
%) (Nodular elongation of 3.0%).

Examples 2 to 6 and Comparative Examples 3 to 8 Using the PVDF and PPS resins used in Example 1 and using the same manufacturing method, the discharge amount of each resin was changed,
The undrawn yarn was taken at 100 m / min.

This was stretched and heat-set under the same conditions as in Example 1 to obtain yarns of 30 μm each. Tensile strength of the single yarn and 100 at 160 ℃
The tensile strength, knot strength and elongation after heating for 0 hour were measured. The measurement results are shown in Table 2.

As is clear from Table 2, in terms of heat resistance (after 1000 hours at 160 ° C), improvement can be recognized by including 20% or more of PPS resin in the inner layer.

However, if the content exceeds 70%, the nodule elongation becomes too small, and some net tears are observed.

Example 3 (1) PVDF resin for sheath layer Polyvinylidene fluoride homopolymer having an inherent viscosity (ηinh) of 1.15 dl / g was extruded at 230 ° C to obtain pellets. The melting point of this polymer was 178 ° C. (DSC: measured at a temperature rising condition of 10 ° C./min).

(2) PAS resin for the core layer The PPS resin pellets used in Example 1 were used.

The above two resin pellets are extruded from a 35 mmφ extruder, the former at 290 ° C and the latter at 320 ° C, and guided to a concentric sheath core type composite yarn nozzle, the sheath layer is polyvinylidene fluoride and the core layer is PPS.
As a resin, a monofilament was spun through a 3.0 mmφ nozzle hole.

This was cooled in 50 ° C. water, continuously stretched 4 times in a 140 ° C. glycerin bath, and then heat set at 210 ° C. in hot air at a constant length under constant length. The diameter of the obtained thread is 250μ
In terms of m, the cross-sectional area ratio of the sheath layer and the core layer was a composite fiber having a structure of the sheath layer 40% and the core layer 60%.

The tensile strength of this composite fiber is 56.5 kg / mm ² (elongation 25.0
%), And the knot strength was 37.0 kg / mm ² (knot strength 17.0%). After the composite fiber was left in a gear oven at 160 ° C. for 1000 hours, the tensile strength was 51.0 kg / mm ² (retention rate 90%), and the knot strength was 31.0 kg / mm ² (retention rate 84%).

〔The invention's effect〕

According to the present invention, excellent chemical resistance of PVDF fiber,
A composite fiber having improved heat resistance while maintaining properties such as strength properties and knot strength can be obtained. The conjugate fiber of the present invention can be used in a wide range of fields as a fiber for various chemical industrial materials.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Mitsuru Ito 18-66 Shinbayashi, Kamizamaji, Tamari-son, Shinji-gun, Ibaraki Prefecture (56) Reference JP-A-63-112717 (JP, A) JP-A-61- 75812 (JP, A) JP 60-240731 (JP, A) JP 59-38042 (JP, A)

Claims (2)

(57) [Claims] 1. A sheath layer made of polyvinylidene fluoride resin having a logarithmic viscosity (ηinh) of 0.7 to 1.4 dl / g and a melting point of 165 to 185 ° C., and a melt viscosity of 1000 to 10000 poise (310 ° C., shearing). It is a value measured at a speed of 1200 / sec.), And is composed of a core layer made of a substantially linear polyarylene sulfide resin, and the cross-sectional area ratio of the core layer is 20 to 60 ° C. A characteristic heat-resistant composite fiber. 2. A logarithmic viscosity (ηinh) around a substantially linear polyarylene sulfide resin having a melt viscosity of 1000 to 10000 poise (measured at 310 ° C. and a shear rate of 1200 / sec). Is 0.7-1.4 dl / g, and the melting point is 165-185 ° C. Melting extrusion is performed so as to coat the polyvinylidene fluoride-based resin and the composite melt spinning is performed. , A draw ratio of 3 to 8 and then 150
It is composed of a sheath layer made of polyvinylidene fluoride-based resin and a core layer made of polyarylene sulfide resin, which is heat-fixed at ~ 270 ° C, and the cross-sectional area ratio of the core layer is 20-60%. A method for producing a heat-resistant composite fiber.