JP2001295131A - Method for producing polyolefin ultra fine fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a polyolefin ultra fine fiber in a god yield, which enables mixed paper having excellent formation to be obtained when blended with natural pulp, and have an excellent heat sealing properties even in a small quantity. SOLUTION: In the method for producing a polyolefin ultra fine fiber in which a polyolefin is kneaded in a molten state together with an acid-modified polyolefin in the foregoing part of an extruder, an aqueous solution of a surfactant is added to the kneaded mixture in an intermediate part of the extruder, the above kneading is continued until the aqueous solution added is homogeneously dispersed in the last part of the extruder and the mixture is extruded from the output end of the extruder to obtain a water retaining ultra fine fiber bundle, the method features using a blend between two or more kinds or polyolefins mutually having a difference in density of at least 0.01 g/cm3. In a preferable embodied producing method, the content of particles in the above water-retaining ultra fine fiber bundle is <=10 wt.% and the maximum fiber diameter of the ultra fine fiber is <=30 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing ultrafine polyolefin fibers. More specifically, the present invention relates to a method for producing a polyolefin-based ultrafine fiber formed into a fiber in an extruder with excellent productivity.

[0002]

2. Description of the Related Art One of the major uses of synthetic short fibers is as a paper modifier, which is expected to impart heat sealability or improve water resistance and paper strength by mixing with natural pulp. You. This mixed paper is obtained by uniformly dispersing natural pulp and short fibers in water and filtering this through a mesh or the like. At this time, if the fiber diameter of the short fibers is large, a mixed paper having good formation cannot be produced. When heat-sealing properties are imparted to the mixed paper, the smaller the fiber diameter of the short fibers, the lower the amount of heat-sealing properties that can be obtained.

[0003] The present applicant has previously disclosed a simple method for producing short fibers in Japanese Patent Publication No. 2-58361, in which a thermoplastic resin, a compatibilizing agent and water are kneaded with an extruder. A method for producing microfibers without the need for special spinning equipment,
Japanese Patent Publication No. 6-53967 discloses a method for shortening ultrafine fibers using a screen mesh attached to the tip of an extruder.

Unfortunately, the ultrafine fibers obtained from the extruder in the above two patents have a so-called particle content (in the present invention, 100% of the fibers which are defibrated and dispersed in a large amount of water).
It cannot be filtered through a mesh sieve. )
And the yield of ultrafine fibers may be low. Further, the fiber diameter distribution tends to be widened, and a fiber having a large maximum diameter may be obtained.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyolefin-based ultrafine fiber which can form a mixed paper having good formation when mixed with natural pulp and which can impart heat sealability with a small amount. The aim is to provide a good manufacturing method.

[0006]

The process for producing a polyolefin-based ultrafine fiber according to the present invention comprises melt-kneading a polyolefin (A) together with an acid-modified polyolefin (B) in a former stage of an extruder, and melting and kneading the melt-kneader in a middle stage of the extruder. A surfactant (C) aqueous solution is added to the product, and kneading is continued at the subsequent stage of the extruder until the added aqueous solution is uniformly dispersed, and extruded from the outlet of the extruder to obtain a hydrated ultrafine fiber bundle. The polyolefin (A) is characterized by using a mixture of two or more polyolefins having a difference in density of at least 0.01 g / cm ³ .

In a preferred embodiment of the method for producing a polyolefin-based ultrafine fiber according to the present invention, the particle content in the hydrated ultrafine fiber bundle is 10% by weight or less, and the maximum fiber diameter of the ultrafine fiber is 30 μm or less.

In the present invention, the polyolefin (A) is preferably a polyethylene resin mixture.

Further, the polyethylene-based resin mixture comprises:
It is preferably a mixture of at least two types of polyethylene selected from low density polyethylene, medium density polyethylene, and high density polyethylene.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The polyolefin (A), acid-modified polyolefin (B), and surfactant (C) used in the production method of the present invention will be described below. Polyolefin (A) The polyolefin (A) used in the present invention has a density difference of at least 0.01 g / cm ³ , preferably 0.1 g / cm ³ .
It is composed of a mixture of two or more polyolefins having a weight of 03 to 0.06 g / cm ³ .

The polyolefin (A) includes, for example, high-pressure low-density polyethylene, medium-low pressure low-density polyethylene, medium-density polyethylene, high-density polyethylene, ultra-high-molecular-weight polyethylene, polypropylene, ultra-high-molecular-weight polypropylene, poly 1-butene, poly 1 3-methyl-1-butene, poly-4-methyl-1-pentene; ethylene, propylene, 1-butene, 3-methyl-1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, −
Α-olefin random or block copolymers such as decene; ethylene-butadiene copolymer, ethylene
Ethylidene norbornene copolymer, ethylene-propylene-butadiene terpolymer, ethylene-propylene-
Dicyclopentadiene terpolymer, ethylene propylene / 1,5-hexadiene terpolymer, ethylene
Examples thereof include a copolymer of one or more olefins such as a propylene / ethylidene norbornene terpolymer and a conjugated or non-co-projected diene.

[0012] Among these, high-pressure low-density polyethylene, medium-low pressure low-density polyethylene, medium-density polyethylene, high-density polyethylene, ultra-high-molecular-weight polyethylene, random or block copolymers of ethylene with other α-olefins; A mixture composed of a polyethylene resin such as a copolymer composed of ethylene and a conjugated or non-co-diene is preferred. In particular, a mixture of at least two kinds of polyethylene selected from low-density polyethylene, medium-density polyethylene, and high-density polyethylene is preferable. In addition,
In the present invention, the density ranges of low-density polyethylene, medium-density polyethylene, and high-density polyethylene are based on JIS K6.
748.

The polyolefin (A) of the present invention contains a low-density polyolefin (A1) and a high-density polyolefin (A2) having a difference in density of 0.01 g / cm ³ or more. The mixing ratio of these is determined by the weight ratio (A1) of the low-density polyolefin (A1) and the high-density polyolefin (A2).
/ A2) is preferably 10/90 to 90/10, more preferably 20/80 to 60/40. Within this range, ultrafine fibers having a small fiber diameter can be obtained with high yield. Mixing of the polyolefin (A1) and the polyolefin (A2) can be performed by a known method.

Acid-Modified Polyolefin (B) The acid-modified polyolefin (B) used in the present invention functions as a compatibilizer for the polyolefin (A) and water to be injected. Therefore, it is preferable to select an acid-modified polyolefin (B) having a chemical property close to that of the polyolefin (A). For example, when a polyethylene-based resin is used as a main component, acid-modified polyethylene is used, and when a polypropylene-based resin is used as a main component, acid-modified polypropylene is used.

The acid-modified polyolefin (B) can be classified into two types, a graft type and a copolymer type. The acid-modified polyolefin (B) in the present invention is a graft-type polyolefin (B) because of its easy development of hydrophilicity. Modified polyolefins are preferred.

The graft type acid-modified polyolefin is a thermoplastic resin obtained by graft-modifying the above-mentioned polyolefin with an unsaturated carboxylic acid. For example, a homopolymer of a monomer such as ethylene, propylene, 1-butene, or 4-methyl-1-pentene, or a polymer obtained by grafting an unsaturated carboxylic acid to a copolymer of two or more monomers including these. . Examples of the unsaturated carboxylic acids used herein include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, tetrahydrophthalic acid, tetrahydrophthalic anhydride, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, and the like. Can be

The copolymerizable acid-modified polyolefin is a thermoplastic polymer obtained by copolymerizing at least one kind of lipophilic monomer and at least one kind of hydrophilic monomer. , Ethylene, propylene, 1-butene, 4-methyl-1-pentene, vinyl acetate, styrene, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, hexyl acrylate,
Hexyl methacrylate, hydroxyethyl acrylic acid,
Examples thereof include hydroxyethyl methacrylic acid, hydroxypropyl acrylic acid, and hydroxypropyl methacrylic acid. Examples of the hydrophilic monomer include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, tetrahydrophthalic acid, tetrahydrophthalic anhydride, itaconic acid, citraconic acid, crotonic acid, and isocrotonic acid.

The preferred modification rate of the acid-modified polyolefin (B) is from 30 to 150 mg-KOH / g as the acid value. When the acid value is within this range, sufficient affinity with added water is easily obtained, and compatibility with the polyolefin is also improved.

The mixing ratio of the polyolefin (A) and the acid-modified polyolefin (B) is usually 3 to 30 parts by weight, preferably 5 to 15 parts by weight per 100 parts by weight of the polyolefin (A). Parts by weight. When the amount of the acid-modified polyolefin (B) is within this range, the surfactant-containing aqueous solution to be injected sufficiently penetrates into the polyolefin (A), and the expected physical properties of the polyolefin (A) are not lost.

Surfactant (C) In the present invention, the above-mentioned polyolefin (A) is supplied to an extruder together with the acid-modified polyolefin (B) and melt-kneaded in the former stage of the extruder. A surfactant (C) aqueous solution is added in the middle section.

The surfactant (C) used in the present invention comprises:
Like the acid-modified polyolefin (B), it acts as a compatibilizer between the water to be added and the polyolefin (A), and subsequently forms fibers by kneading. Surfactant (C) is dissolved in water and pumped as an aqueous solution.

Specific examples of the surfactant (C) that can be used in the present invention include polyoxyethylene fatty acid esters, polyoxyethylene fatty acid ethers, polyoxypropylene / polyoxyethylene block copolymers, higher fatty acid salts, and higher fatty acid salts. Alcohol sulfate, higher alkyl sulfonate, higher alkyl disulfonate, higher fatty acid ester sulfonate, higher alkylbenzene sulfonate, higher alkylphenol sulfonate,
Examples thereof include polyoxyethylene sorbitan monofatty acid ester and sorbitan monofatty acid ester.

In the present invention, since fibers are produced at 120 to 160 ° C., among these, those exhibiting surface activity even at a high temperature (having a high cloud point) are preferable. For example, polyoxyethylene oleyl ether (POE) Are preferred.

The surfactant (C) is usually used in an amount of 3 to 20.
%, Preferably 5 to 15% by weight. The injection amount is usually 15 to 35 parts by weight, preferably 18 to 30 parts by weight of the aqueous solution having the above concentration range per 100 parts by weight of the total amount of the melt-kneaded product of the polyolefin (A) and the acid-modified polyolefin (B), More preferably, it is 19 to 25 parts by weight.

Next, the method for producing the polyolefin-based ultrafine fiber of the present invention will be described. In the production method of the present invention, in order to obtain ultrafine fibers, the polyolefin (A) is supplied to an extruder together with the acid-modified polyolefin (B), and the mixture is melt-kneaded in a stage preceding the extruder. Next, an aqueous solution of the surfactant (C) is added to the melt-kneaded product in the middle stage of the extruder, and then kneading is continued and extruded until the aqueous solution added in the latter stage of the extruder is uniformly dispersed.

The kneading of the resin by the extruder may be performed at a temperature at which the kneading can be sufficiently performed.
It is performed within the range of ~ 200 ° C. Further, kneading after the addition of the surfactant aqueous solution is preferably performed in a temperature range in which the effect of the surfactant is not reduced, and usually 120 to 1
It is performed within the range of 60 ° C.

The injected surfactant aqueous solution is gradually dispersed in the polyolefin (A) resin due to the compatibilizing effect of the surfactant. And in this invention, kneading is continued until water is uniformly disperse | distributed in the latter stage of an extruder. Here, the state in which the water is uniformly dispersed means that the dispersion of the water in the resin proceeds and the acid-modified polyolefin (B)
Swelling, which causes the resin to become increasingly fragmented. As a result, it refers to a state where an aqueous dispersion in which the continuous phase is water is formed, as in the case where dispersed water causes phase inversion and the resin is dispersed in water.

By extruding the kneaded material in this state, a hydrated ultrafine fiber bundle is obtained from the outlet of the extruder. Since the kneading temperature of the extruder is 100 ° C. or higher, most of the water is extruded and evaporates, but the ultrafine fiber bundle in this state contains residual water. The water-containing ultrafine fiber bundle is an ultrafine fiber bundle having a substantially circular cross-sectional shape and a shape in which a large number of ultrafine fibers having an indefinite length and a fiber diameter of 1 to 30 μm are bundled in a substantially parallel state without being twisted.

Next, the hydrated ultrafine fiber bundle is defibrated into short fibers. For the defibration treatment, various defibration devices, crushers and the like can be used. Alternatively, a screen mesh may be attached to the extruder tip. By the defibration treatment, the ultrafine fiber bundle has an average fiber length of 2.5 mm or less, preferably 0.1 to 2.0 mm, more preferably 0.5 to 1.5 mm.
mm short fibers.

The defibrated and shortened fibers are dried to obtain ultrafine fibers. At that time, in order to remove so-called particles, the defibrated fibers are usually dispersed in a large amount of water and sieved with a predetermined mesh sieve. At this time, if there are many particles,
Although the yield of the obtained ultrafine fibers is reduced, according to the production method of the present invention, the particle content in the hydrated ultrafine fiber bundle can be reduced to 10% by weight or less. Drying must be performed at a temperature at which the fibers do not fuse with each other, and is usually performed at a temperature lower than the melting temperature of the resin forming the fibers. By drying, a surfactant dissolved in water can be coated on the fiber surface to impart hydrophilicity.

In the present invention, the particle content was measured by the following method. The water-containing fiber bundle extruded from the extruder is collected (collected weight: W), put into 10 times the amount of water of the bundle, and defibrated with a household mixer for 1 minute. The defibrated fibers were sieved with a 100-mesh sieve, and the dry weight (W ₀ ) of the fibers obtained on the mesh was calculated by the following equation. Particle content (%) = [1- {W ₀ / (W-content water amount)}] × 100 where water content = {supply water supply amount / (resin supply amount + injection water supply amount)} × W The injection water supply amount is the weight per hour of the surfactant aqueous solution supplied to the extruder, and the resin supply amount is the weight per hour of the resin (polyolefin and acid-modified polyolefin) supplied to the extruder.

The manufacturing method according to the present invention will be described with reference to the following specific examples. FIG. 1 is a schematic view of an example of an extruder used for producing the water-containing ultrafine fiber bundle of the present invention. As the extruder, a meshing twin-screw extruder is desirable because the production amount can be increased. The inside of the barrel at the middle stage of the extruder is filled with molten resin, and resin pressure is generated. The pump is preferably a plunger pump or a gear pump in order to inject the surfactant aqueous solution against the resin pressure.

In the production of ultrafine fibers, first, a mixed resin obtained by dry blending a polyolefin (A) and an acid-modified polyolefin (B) at a predetermined ratio is put into a hopper 2 and fed to an extruder 1. And the extruder front section (C1 to C
3)), and sufficiently knead while heating. After the resin is sufficiently melt-kneaded, the surfactant (C) aqueous solution 3 is injected at a predetermined flow rate by the pump 4 in the middle part (C4 part) of the extruder.

Subsequently, in the latter stage of the extruder, kneading is continued until the added aqueous surfactant solution is uniformly dispersed, and then extruded. In this way, at the extruder outlet 5, ultrafine fibers can be spun in the extruder without requiring a device for spinning, and a hydrated ultrafine fiber bundle is obtained.

Next, the hydrated ultrafine fiber bundle is defibrated into short fibers. The defibration treatment may be performed using a natural pulp refiner or a beater, or may be performed using a pulverizer after drying. It is preferable that the crusher simultaneously applies a shearing force and an impact force to the fiber bundle. In addition, if a screen mesh is attached to the tip of the extruder, the water-containing ultrafine fibers can be extruded after shortening.

Various dryers can be used for drying the ultrafine fibers. Usually, before drying, the defibrated fibers are dispersed in a large amount of water, and sieved with a predetermined mesh sieve to remove particles. As the dryer, for example, hot air dryer,
Infrared heaters, hot plates, etc. can be used without restriction. Among these, a hot-air dryer is preferable in that no fusion occurs due to local heating of the fibers.

The polyolefin-based ultrafine fiber thus obtained has an average fiber length of 2.5 mm or less and a fiber diameter of 1 to
It is a short fiber made of ultrafine fibers of 30 μm. This short fiber has a good blending property with natural pulp, a uniform, well-formed blended paper can be obtained, a heat sealing property can be imparted with a small amount of addition, and it is suitable as a short fiber for blending natural pulp. is there. The mixing ratio (weight ratio) of the natural pulp and the polyolefin-based ultrafine fiber of the present invention is usually 100: 3 to 100: 3.
0 is determined according to the desired physical properties of the mixed paper.

[0038]

The present invention will be described in detail with reference to the following examples and comparative examples, but the present invention is not limited to these examples. In addition, the measuring method of the fiber used by the Example and the comparative example is shown below.

The fibers were photographed by the maximum fiber diameter of the electron microscope, to determine the maximum fiber diameter.

The equipment and raw materials used in Examples and Comparative Examples are described below. Equipment Extruder: twin screw, the same direction intermeshing type, diameter 30mm
φ, L / D = 42, manufactured by Plastic Engineering Laboratory Co., Ltd. Pump: Double plunger type PU617, manufactured by GL Sciences Corporation

Raw material low density polyethylene: Mirason ^™ FL-60 (0.915 g density)
/ cm ² , manufactured by Mitsui Chemicals, Inc., high-density polyethylene: Neozex ^™ 50300, (density 0.948 g / cm ² , Mitsui Chemicals, Inc.)
Hyzex ^™ 1300J (density 0.965 g / cm ² , manufactured by Mitsui Chemicals, Inc.), acid-modified polyolefin: Nucrel ^™ N
1560 (manufactured by DuPont-Mitsui Polychemicals); High Wax ^™ 2203A (manufactured by Mitsui Chemicals, Inc.); Surfactant: Newpole ^™ PE108 (manufactured by Sanyo Chemical Co., Ltd.); Emulgen
^TM 430 (made by Kao Corporation),

(Example 1) Polyolefin (A
1) Mirason ^™ FL-60 as 1) and HIZEX ^™ 1300J as polyolefin (A2) on the high density side in a ratio of 1: 1.
(A) (density of mixed resin)
0.940 g / cm ² , MFR (according to ASTM D1238, temperature 190 ° C, load 2.16 kg
Dry blending of 100 parts by weight of 30 g / 10 min) and 15 parts by weight of Nucrel ^TM N1560 as an acid-modified polyolefin (B) was fed from a hopper to an extruder, melt-kneaded, and surface-active. As an agent (C), a 10% by weight aqueous solution of Newpol ^™ PE108 was injected into the middle stage of the extruder by a pump so that the ratio was 20 parts by weight with respect to 100 parts by weight of the polyolefin (A). Subsequently, a hydrated fiber bundle was obtained from the outlet of the extruder. The temperature conditions of the extruder are as follows: C1: 120 ° C., C2: 140 ° C., C
3: 155 ° C, C4: 135 ° C, C5: 135 ° C, C
6: 135 ° C, C7: 120 ° C, D: 110 ° C. The particle content and the maximum fiber diameter of this water-containing fiber bundle were measured. Table 1 shows the results.

Example 2 As a polyolefin (A),
A resin in which Mirason ^™ FL-60 and Neozex ^™ 50300 are mixed in a ratio of 2: 8 (density of mixed resin: 0.932 g)
/ cm ² and MFR (35 g / 10 min according to ASTM D1238, measured at a temperature of 190 ° C. and a load of 2.16 kg) were obtained in the same manner as in Example 1 to obtain a hydrated fiber bundle. Table 1 shows the measurement results of the hydrous fiber bundle.
Shown in

Comparative Example 1 As polyolefin (A),
A hydrated fiber bundle was obtained in the same manner as in Example 1 except that only Mirason ^™ FL-60 was used. Table 1 shows the measurement results of the water-containing fiber bundle. (Comparative Example 2) As a polyolefin (A), HIZEX
^A hydrated fiber bundle was obtained in the same manner as in Example 1 except that only ^TM 1300J was used. Table 1 shows the measurement results of the hydrous fiber bundle.
Shown in (Comparative Example 3) Neozex as polyolefin (A)
^A hydrated fiber bundle was obtained in the same manner as in Example 1 except that only ^TM 50300 was used. Table 1 shows the measurement results of the hydrous fiber bundle.
Shown in

Example 3 As polyolefin (A),
Mirason^TMFL-60 and HIZEX^TM1300J and
(Mixed resin density 0.950g)
/cm^Two, MFR (according to ASTM D1238, temperature 190 ℃, load 2.16kg
Measurement) 22g / 10min) and acid-modified polyolefin (B)
Then high wax^TM2203A, as surfactant (C)
Emulgen ^TMExcept using a 15 wt% aqueous solution of 430
In the same manner as in Example 1, a water-containing fiber bundle was obtained. This hydrous
Table 1 shows the measurement results of the fiber bundle.

[0046]

[Table 1]

[0047]

According to the production method of the present invention, it is possible to obtain a mixed paper having good mixing properties with natural pulp, uniform and good formation, and to provide a heat sealing property with a small amount of addition. Microfibers can be produced in a simple manner with high productivity without requiring special spinning equipment.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an extruder for producing a polyolefin-based ultrafine fiber according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Extruder 2 Hopper 3 Surfactant aqueous solution 4 Pump 5 Extruder outlet C1, C2, C3 Heater of extruder front part C4 Heater of extruder middle part C5, C6, C7 Heater of extruder rear part D Die

Claims (4)

[Claims] 1. A polyolefin (A) is melt-kneaded together with an acid-modified polyolefin (B) in a former stage of an extruder, an aqueous solution of a surfactant (C) is added to the melt-kneaded product in a middle stage of the extruder, and further a second stage of the extruder. In this method, the kneading is continued until the added aqueous solution is uniformly dispersed, and extruded from the extruder outlet to obtain a hydrated ultrafine fiber bundle, wherein the polyolefin (A) has a density difference of at least 0.1.
A method for producing a polyolefin-based ultrafine fiber, comprising using a mixture of two or more polyolefins having a weight of 01 g / cm ³ . 2. The method for producing a polyolefin-based ultrafine fiber according to claim 1, wherein the content of particles in the hydrated ultrafine fiber bundle is 10% by weight or less, and the maximum fiber diameter of the ultrafine fiber is 30 μm or less. . 3. The method for producing a polyolefin-based ultrafine fiber according to claim 1, wherein the polyolefin (A) is a polyethylene-based resin mixture. 4. The polyolefin microfiber according to claim 3, wherein the polyethylene resin mixture is a mixture of at least two types of polyethylene selected from low density polyethylene, medium density polyethylene, and high density polyethylene. Manufacturing method.