JPH10130947A - Polyolefin-based fiber excellent in hydrophilicity and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a polyolefin fiber excellent in hydrophilicity without deteriorating mechanical strength, chemical resistance, etc., essentially possessed by a polyolefin. SOLUTION: Oxygen functional groups are introduced into the surface of (1) a polypropylene fiber comprising a syndiotactic polypropylene, (2) a blend fiber comprising an olefinic polymer containing >=30wt.% syndiotactic polypropylene or (3) a core-sheath type conjugated fiber comprising a core part composed of an olefinic polymer and a sheath part composed of the syndiotactic polypropylene or an olefinic polymer containing >=30wt.% syndiotactic polypropylene by carrying out oxidizing treatment according to methods such as an electron ray irradiation, a γ-ray irradiation and an ultraviolet ray irradiation methods, a photon method, a flame method, a corona discharge method or a glow discharge method. Thereby, the hydrophilicity is imparted thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyolefin fiber, and more particularly, to a polyolefin fiber having excellent hydrophilicity without lowering the mechanical strength of the fiber.

[0002]

2. Description of the Related Art In general, polyolefins such as polyethylene and polypropylene are excellent in mechanical properties, low in specific gravity, excellent in fiber workability and cost, and extremely excellent in chemical resistance, especially alkali resistance at high temperatures. ing. In recent years, utilizing these characteristics, there has been a remarkable advancement of polyolefin fibers into the industrial materials field, particularly into the nonwovens field. However, polyolefins are adhesive,
At present, the applications of polyolefin fibers are limited due to their inferior hydrophilicity, and it is desired to expand their applications by improving these drawbacks.

For example, asbestos substitute fibers for cement reinforcement are required to have strength, alkali resistance at high temperatures, affinity with cement, water dispersibility, etc., but polypropylene is significantly inferior in affinity with cement and the like. The improvement is desired. Further, the alkali battery separator is required to have alkali resistance, hydrophilicity, oxidation resistance and the like. Polyolefins, especially polypropylene, are also used in wet filters such as filter cloths in terms of chemical resistance and mechanical strength, but improvement in hydrophilicity is desired. However, those in which a sulfonic acid group is introduced by a hydrophilization treatment method using sulfuric acid or the like are accompanied by deterioration of the polyolefin fiber due to the treatment, and have poor mechanical strength. Similarly, a polyolefin fiber is also deteriorated by a hydrophilization treatment method by a gas phase method using plasma treatment, electron beam irradiation, or the like. Therefore, development of a polyolefin fiber having an excellent balance between mechanical properties and hydrophilicity is desired. That is, when the hydrophilic treatment is performed by the above-described method, fiber degradation occurs,
Originally, the mechanical properties of the polyolefin-based fiber would not be exhibited, so that there was a drawback that the level of hydrophilization had to be reduced or the mechanical strength had to be sacrificed. Further, when the level of hydrophilization is too high, the chemical resistance is lowered.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and provides hydrophilicity without impairing the properties inherent to polyolefins, such as mechanical strength and chemical resistance. An object of the present invention is to provide an excellent polyolefin fiber.

[0005]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventors have found that the above problems can be solved by using syndiotactic polypropylene at least on the fiber surface, and complete the present invention. Reached. That is, the present invention provides (1) a polypropylene fiber composed of a syndiotactic polypropylene, (2) a blend fiber composed of an olefin-based polymer containing 30% by weight or more of syndiotactic polypropylene, or (3) an olefin-based core. A fiber selected from the group consisting of a polymer and a core-sheath composite fiber whose sheath portion is composed of syndiotactic polypropylene or an olefin polymer containing at least 30% by weight of syndiotactic polypropylene, An oxygen functional group is introduced into the surface of the fiber by an oxidation treatment, and the fiber has hydrophilicity.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Syndiotactic polypropylene used in the present invention means one having a pendat fraction of 0.5 or more. Here, the pendat fraction is 13C-
It is the ratio between the intensity of about 20 ppm (corresponding to syndiotactic pendat) observed by NMR and the peak intensity attributed to the methyl group of all propylene units. Conventionally,
When producing syndiotactic polypropylene,
Although a vanadium compound was used as a catalyst, it was only possible to obtain a pentad having a pentad fraction of about 0.5, and it was not possible to industrially produce it in large quantities. However, in recent years, a polypropylene having a high tacticity with a pendat fraction of more than 0.7 has been obtained by a catalyst comprising a transition metal compound having an asymmetric ligand and an aluminoxane. The syndiotactic polypropylene used in the present invention preferably has a pendat fraction of 0.6 or more, more preferably 0.7 or more. The syndiotactic polypropylene may be any syndiotactic polypropylene substantially composed of a propylene homopolymer or a copolymer of propylene and ethylene and / or an α-olefin.

As a method for producing the above syndiotactic polypropylene, for example, Sakai Kaihei 3-17900
No. 6 and other publications. Examples of the polymerization catalyst include a crosslinked transition metal compound having asymmetrical ligands and a co-catalyst, and even a catalyst having a different structure can produce a polypropylene having a pendat fraction of 0.6 or more. Any polymerization method can be used, and the polymerization method is not particularly limited, and a solvent polymerization method using an inert catalyst, a bulk polymerization method, or a gas phase polymerization method can also be used.

Next, the olefin-based polymer in the present invention means polyethylene, polypropylene, polymethylpentene, etc., and these random copolymers, graft copolymers, such as ethylene-propylene copolymers, etc. It may be a block copolymer. In the present invention, these olefin-based polymers may be used alone or in a blend.

In the blend fiber of the syndiotactic polypropylene and the olefin polymer, it is desirable to use the syndiotactic polypropylene in an amount of 30% by weight or more, preferably 40% by weight or more. If the amount is less than 30% by weight, the effect of syndiotactic polypropylene that the polymer chains are hardly deteriorated at the time of imparting hydrophilicity is not exhibited.

[0010] The spinning conditions for producing the polyolefin-based fiber of the present invention are not particularly limited, and the fiber is produced by an ordinary method. That is, in the case of the syndiotactic polypropylene fiber of (1), the spinning temperature is 230
To 300 ° C., and in the case of the core-sheath composite fiber of (3),
As for the spinning temperature, the sheath portion is 230 to 300 ° C. due to the use of syndiotactic polypropylene, and the core portion is 200 to 300 ° C. depending on the polyolefin polymer used.
C is common. Similarly, in the case of the blend fiber (2), the temperature is generally set to 200 to 300 ° C. according to the blend ratio. The blending method is not particularly limited, and pellets obtained by blending with an extruder in advance may be spun, or each pellet or powder may be spun while being supplied in a predetermined amount by a weight feeder. . In the present invention, in order to improve the mechanical strength, it is desirable to stretch the spun fiber three times or more, and hot water stretching is preferred.

Incidentally, it is needless to say that stabilizers such as antioxidants and ultraviolet absorbers, antistatic agents, flame retardants, and coloring agents such as dyes and pigments can be used in the fiber of the present invention as required. Absent.

Next, the oxidation treatment in the present invention means that an oxygen functional group (-COOH, -OH, -C
ＯO, —SO ₃ , and —NO ₃ groups). By introducing these functional groups to the fiber surface, hydrophilicity can be imparted to the olefin fiber as described above.

In the present invention, the oxidation treatment for introducing an oxygen functional group into the fiber surface includes electron beam irradiation, γ-ray irradiation, ultraviolet irradiation, photon, flame, corona discharge and glow discharge. And other plasma processing methods. These oxidation treatment methods may be used alone or in combination of two or more. These methods are used at room temperature
It may be carried out under normal pressure, but He, A
r, reactive gases such as air, oxygen, nitrogen, CO, CO
₂ , sulfur oxides (eg, SO ₂ , SO _3, etc.) or nitrogen oxides (eg, NO, NO ₂ , N ₂ O, etc.). These inert gases and reactive gases generate various chemical species (electrons, ions, radicals, excited molecules, etc.) when an electric field is applied. As a result, the polymer easily reacts with the polymer constituting the fiber, and an effect of effectively introducing an oxygen functional group to the fiber surface is brought about.

In introducing an oxygen functional group on the fiber surface, a monomer exhibiting hydrophilicity may be coated on the fiber surface in advance, and then the oxygen functional group may be introduced by oxidation treatment. In this case, examples of the compound to be coated on the fiber surface include monomers exhibiting hydrophilicity such as acrylic acid, methacrylic acid, methallylsulfonic acid, allylsulfonic acid, and styrenesulfonic acid. After coating, these compounds are fixed to the fiber surface using the above-mentioned oxidation treatment method such as an electron beam irradiation method, a γ-ray irradiation method, and a plasma treatment method. These compounds may be used alone or in combination of two or more.

In the present invention, the method of oxidizing the fiber surface by contacting with an acid may include:
And chlorosulfonic acid. These may be used alone or as a mixture of two or more. The method of contacting the fiber surface with the acid is not particularly limited, but a method of directly immersing the polyolefin fiber in these acids is often used. For example, when using concentrated sulfuric acid, immersion at 50 to 120 ° C. for 5 to 60 minutes is common.

[0016]

According to the present invention, by using syndiotactic polypropylene, the surface of the polyolefin fiber can be subjected to a hydrophilic treatment without causing deterioration of the polyolefin fiber. As a result, it is possible to provide a polyolefin fiber excellent in balance between hydrophilicity, mechanical properties, and chemical resistance without impairing the mechanical properties and chemical resistance inherent to the polyolefin fiber.

[0017]

The present invention will be specifically described below with reference to examples. The present invention is not limited to the following embodiments.

(Resin Properties) Table 1 shows the properties of the resins used in the following Examples and Comparative Examples.

[0019]

[Table 1]

(Polymerization of syndiotactic polypropylene) The syndiotactic polypropylene shown in Table 1 was polymerized as follows. First, J.I.
Am. Chem. Soc. 1987, No. 109, p6
As described in 544, isopropyl (cyclopentadienyl-1-fluorenyl) zirconium dichloride was synthesized by converting isopropylcyclopentadienyl-1-fluorene to a lithium salt and reacting the lithium salt with zirconium tetrachloride. Next, 0.33 mmol of triethylaluminum was dissolved in 2 ml of toluene and added to the reactor, and the reactor temperature was set to 70 ° C. And 1500
ml of propylene was added to the reactor and stirred for 10 minutes.
After dissolving 45 mg of tris (pentafluorophenyl) boron in 20 ml of toluene and similarly dissolving 35 mg of isopropyl (cyclopentadienyl-1-fluorenyl) zirconium chloride in 25 ml of toluene, the two kinds of the toluene solutions are dissolved for 5 minutes. Mixed together. After adding this catalyst mixture to a 50 ml stainless steel cylinder, 200 ml of propylene was added to the reactor through the cylinder. The contents of the reactor were stirred and reacted for about 30 minutes. After exhausting unreacted propylene from the reactor, the reaction product was washed with acetone and dried under vacuum.

(Measurement of Tacticity of Syndiotactic Polypropylene) Approximately 2 measured by 13 C-NMR
The ratio between the intensity of 0 ppm (rrrr) and the peak intensity (mm, mr, rr) attributed to the methyl group of all propylene units was measured, and the syndiotactic pendat fraction was calculated by the following equation.

Syndiotactic pendat fraction (%)
= Rrrr / (mm + mr + rr) × 100

Example 1 Syndiotactic polypropylene was melt-spun under the conditions shown in Table 2 and then hot-drawn to obtain a filament having a fineness of 3d (denier, the same applies hereinafter) and a staple having a fiber length of 51 mm. Next, using this staple, a web was formed through a roller card machine, and a nonwoven fabric sheet having a basis weight of 40 g / m ² was obtained with a spunlace machine. Next, the nonwoven fabric sheet and the filament were placed in a reactor and subjected to a corona discharge treatment at a normal temperature and a normal pressure using an applied voltage of 200 KV, thereby performing a hydrophilic treatment on the fiber surface.

(Example 2) Under the conditions shown in Table 2, a blend of 60% by weight of polypropylene (1) and 40% by weight of syndiotactic polypropylene was melt-spun and then hot-stretched. Filament and fiber length 51m
m of staples were obtained. Next, a nonwoven fabric sheet having a basis weight of 40 g / m ² was obtained in the same manner as in Example 1. Next, the nonwoven fabric sheet and the filament were subjected to a corona discharge treatment under the same conditions as in Example 1 to perform a hydrophilic treatment on the fiber surface.

Example 3 Under the conditions shown in Table 2, a blend of 30% by weight of polyethylene (1) and 70% by weight of syndiotactic polypropylene was melt-spun and then hot-drawn to obtain a filament having a fineness of 3d. Fiber length 51mm
Staples. Next, the same as in Example 1, the basis weight 4
A non-woven fabric sheet of 0 g / m ² was obtained. Next, the nonwoven fabric sheet and the filament were subjected to a corona discharge treatment under the same conditions as in Example 1 to perform a hydrophilic treatment on the fiber surface.

Example 4 The same filament and nonwoven fabric sheet as obtained in Example 2 were immersed in acrylic acid.
The fiber surface was hydrophilized by placing it in a reactor and irradiating it with 4 Mrad of electron beam under a nitrogen atmosphere.

Example 5 The same filament and nonwoven fabric sheet as obtained in Example 2 were immersed in acrylic acid.
The fibers were placed in a reactor and irradiated with ultraviolet light having a wavelength of 200 nm or more to perform a hydrophilic treatment on the fiber surface.

Example 6 The same filament and nonwoven fabric sheet as obtained in Example 2 were placed in a reactor, and He7
A high-frequency voltage of 5 KHz was applied at normal temperature and normal pressure in an atmosphere of 0% and air at 30% to perform glow discharge, thereby performing a hydrophilic treatment on the fiber surface.

Example 7 The same filament and nonwoven fabric sheet as obtained in Example 1 were heated to 80 ° C.
After immersion in 8% concentrated sulfuric acid for 20 minutes, neutralize, wash and dry,
The fiber surface was subjected to a hydrophilic treatment.

[0030]

[Table 2]

(Example 8) Under the conditions shown in Table 3, a core-sheath type composite fiber having polypropylene (1) in the core and syndiotactic polypropylene in the sheath was melt-spun and then hot-stretched. A staple having a filament and a fiber length of 51 mm was obtained. Next, using this staple, a web was formed through a roller card machine, and a nonwoven fabric sheet having a basis weight of 40 g / m ² was obtained with a spunlace machine. Next, the nonwoven fabric sheet and the filament were placed in a reactor and subjected to a corona discharge treatment at a normal temperature and a normal pressure using an applied voltage of 200 KV, thereby performing a hydrophilic treatment on the fiber surface.

Example 9 Under the conditions shown in Table 3, melt-spun core-sheath type composite fibers having polypropylene (1) in the core and a blended polymer of syndiotactic polypropylene and polypropylene (1) in the sheath. After that, the resultant was thermally drawn to obtain a filament having a fineness of 3d and a staple having a fiber length of 51 mm. Next, a web was formed using the staples through a roller card machine, and a nonwoven fabric sheet having a basis weight of 40 g / m ² was obtained with a spunlace machine. Next, the nonwoven fabric sheet and the filament are put into a reactor,
The surface of the fiber was subjected to a hydrophilization treatment by performing a corona discharge treatment using an applied voltage of 200 KV under normal pressure.

(Example 10) The same nonwoven fabric sheet and filament as those obtained in Example 8 were immersed in styrene sulfonic acid, and then placed in a reactor.
By performing Mrad irradiation, a hydrophilic treatment was performed on the fiber surface.

Example 11 The same filament and nonwoven fabric sheet as obtained in Example 8 were placed in a reactor,
A high-frequency voltage of 5 KHz was applied at normal temperature and normal pressure in an atmosphere of 90%, a mixed gas of nitrogen, hydrogen, oxygen, and CO ₂ at 10%, and glow discharge was applied to the fiber surface to perform a hydrophilic treatment.

[0035]

[Table 3]

Comparative Example 1 Polypropylene shown in Table 1
Using only (1), the mixture was melt-spun under the conditions shown in Table 4 and then hot-drawn to obtain a filament having a fineness of 3d and a staple having a fiber length of 51 mm. Next, using this staple fiber, a nonwoven fabric sheet having a basis weight of 40 g / m ² was obtained in the same manner as in Example 1.

Comparative Example 2 The filament strength of the syndiotactic propylene obtained in Example 1 and the water absorption of the non-woven sheet were measured.

Comparative Example 3 The same filament and nonwoven fabric sheet obtained in Comparative Example 1 were subjected to a corona discharge treatment under the same conditions as in Example 1, and the fiber surface was subjected to a hydrophilic treatment.

(Comparative Example 4) The same filament and nonwoven fabric sheet as obtained in Comparative Example 1 were immersed in acrylic acid under the same conditions as in Example 4, placed in a reactor, and irradiated with 4 Mrad of electron beam under a nitrogen atmosphere. By doing so, the fiber surface was subjected to a hydrophilic treatment.

(Comparative Example 5) Under the conditions shown in Table 4, 90% by weight of polypropylene (1) and 10% by weight of syndiotactic polypropylene were blended and melt-spun, followed by hot drawing, and a 3d weave filament. And fiber length 51m
m of staples were obtained. Next, using this staple fiber, a nonwoven fabric sheet having a basis weight of 40 g / m ² was obtained in the same manner as in Example 1. Next, the nonwoven fabric sheet and the filament were subjected to a corona discharge treatment under the same conditions as in Example 1, and the fiber surface was subjected to a hydrophilic treatment.

[0041]

[Table 4]

Examples 1 to 11 and Comparative Examples 1 to 5
Table 5 shows the results of measuring the strength of the filaments obtained in the above and the water absorption of the nonwoven fabric sheet. In addition, the physical property evaluation method is as shown below.

[Water Absorption] The obtained nonwoven fabric sheet was prepared to have a sample width of 25 mm and a length of 300 mm, and one end of the sheet was vertically immersed in ion-exchanged water (immersion height: 20 mm).
The liquid absorption height (mm) after one minute was determined, and this was defined as the water absorption.

[Tensile strength of fiber] The obtained filament (before and after the hydrophilic treatment) was subjected to JIS L 101
3 was measured.

[0045]

[Table 5]

From Comparative Examples 1 and 2, it can be seen that the water absorption is extremely poor when no hydrophilization treatment is carried out using either ordinary polypropylene or syndiotactic polypropylene. Further, as shown in Examples 1 to 11, the water absorption was greatly improved by using any of the hydrophilic treatment methods,
Further, it can be seen that the fiber strength before and after the hydrophilic treatment hardly changes. On the other hand, as is apparent from Comparative Examples 3 and 4,
If you do not use syndiotactic polypropylene,
It can be seen that although the degree of water absorption is improved by the hydrophilization treatment, the fiber strength after the hydrophilization treatment is significantly reduced. Also, as shown in Comparative Example 5, when the amount of the syndiotactic polypropylene in the blend fiber is outside the range of the present invention, similarly, it is found that the fiber strength after the hydrophilization treatment is significantly reduced.

[0047]

As described above, according to the present invention, it is possible to provide a polyolefin fiber excellent in hydrophilicity without impairing the inherent properties of polyolefin such as mechanical strength and chemical resistance. That is, a core-sheath type composite comprising a syndiotactic polypropylene fiber, a blended fiber of a syndiotactic polypropylene and an olefin-based polymer, or a core comprising a polyolefin-based polymer and a sheath comprising a syndiotactic polypropylene-containing olefin-based polymer. By oxidizing the fiber surface of the fiber, the above object is achieved. As a result, it has become possible to apply the polyolefin-based fiber to a field which has heretofore been inferior in hydrophilicity and thus could not be used or where the market has not expanded.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI D06M 13/256 D06M 11/02 13/30

Claims (5)

[Claims] 1. A fiber selected from the following fibers (1) to (3), wherein an oxygen functional group is introduced into the surface of the fiber by an oxidation treatment to have a hydrophilic property. A polyolefin fiber characterized by the following. (1) Polypropylene fiber composed of syndiotactic polypropylene. (2) 30% by weight of syndiotactic polypropylene
A blend fiber comprising the olefin polymer contained above. (3) A core-sheath type composite fiber whose core is composed of an olefin-based polymer and whose sheath is composed of syndiotactic polypropylene or an olefin-based polymer containing 30% by weight or more of syndiotactic polypropylene. 2. The method for producing a polyolefin fiber according to claim 1, wherein an oxygen functional group is introduced into the fiber surface by an oxidation treatment, wherein an electron beam irradiation method, a γ-ray irradiation method, an ultraviolet irradiation method, A method for producing a polyolefin fiber, wherein the oxidation treatment is performed using at least one method selected from the group consisting of a method, a flame method, a corona discharge method, and a glow discharge method. 3. Upon introducing oxygen functional groups on the fiber surface by oxidation treatment, air, oxygen, nitrogen, CO, CO _2,
3. The method for producing a polyolefin fiber according to claim 2, wherein at least one gas selected from He, Ar, sulfur oxides and nitrogen oxides is used. 4. After coating at least one compound selected from acrylic acid, methacrylic acid, methallyl sulfonic acid, allyl sulfonic acid, and styrene sulfonic acid on the fiber surface, the fiber surface is oxidized by oxidation treatment. The method for producing a polyolefin-based fiber according to claim 2 or 3, wherein a functional group is introduced. 5. The method for producing a polyolefin fiber according to claim 1, wherein when introducing an oxygen functional group into the fiber surface by oxidation treatment, the fiber surface is treated with fuming sulfuric acid, concentrated sulfuric acid, and chlorosulfonic acid. A method for producing a polyolefin-based fiber, comprising contacting with at least one acid selected from the group consisting of: