JPH09176983A - Polyvinyl alcohol-based pulp and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a nonsticky and homogeneous polyvinyl alcohol-based pulp by beating an island-in-sea type fiber composed of a polyvinyl alcohol-based polymer and a water-insoluble polymer in water under a shearing force and then adding a nonionic or a cationic surfactant thereto. SOLUTION: This polyvinyl alcohol-based pulp comprises a fibrillated material of an island-in-sea type fiber, comprising (A) a polyvinyl alcohol-based polymer and (B) a water-insoluble polymer and containing either thereof as the sea component and the other as the island component and further a nonionic or a cationic surfactant added thereto. The pulp is obtained by forming the island-in-sea type fiber from (A) the polyvinyl alcohol-based polymer having >=500, preferably >=1,500 polymerization degree and >=80% saponification degree and (B) the water-insoluble polymer such as cellulose acetate at a weight ratio (A)/(B) of (90/10) to (20/80), using either thereof as the sea component and the other as the island component, cutting the formed island- in-sea type fiber to 3mm fiber length, then beating the cut fiber in water with a disk refiner, dehydrating the fiber, providing the fibrillated material, adding the 10-50C, preferably the 12-50C nonionic or cationic surfactant selected from among the quaternary ammonium salts and the silicone-based surfactants in an amount of 0.01-5% based on the fibrillated material thereto and drying the resultant material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is composed of polyvinyl alcohol fibers, has good thermal characteristics, strength, and chemical resistance, has little sticking between pulp constituent fibers, and has a very small fiber diameter. The present invention relates to a polyvinyl alcohol-based synthetic pulp having The pulp of the present invention is
It can be used for various filters, battery separators such as alkaline manganese batteries, and powder holding materials for friction materials typified by brake materials.

[0002]

2. Description of the Related Art Conventional pulping technology uses para-aramid fibers, polyarylate fibers, cellulose fibers, etc., in which the molecules are oriented in the fiber axis direction to a relatively high degree, and cuts them to a certain length. After that, a method is known in which a fiber is fibrillated by applying a high shearing force in water with a desk refiner or the like, and then dried. on the other hand,
As an attempt for pulping using polyvinyl alcohol (hereinafter sometimes simply referred to as PVA) fiber, a method proposed by the present inventors in Japanese Patent Application No. 7-100874, that is, PVA is a sea component and water is used. It is a method of fibrillating a sea-island structure fiber in which an insoluble polymer is an island component, by the same method as the above known method.

[0003]

However, when the fibrillation is carried out by this method, the PVA component does not have a high degree of water resistance, so that the fibers constituting the pulp are stuck to each other in the drying step, and normal fibrillation occurs. There is a problem in that it is difficult to obtain pulp that is separated into pieces. The present invention is a PVA
The present invention proposes a good pulp having an average single fiber denier with an extremely thin fiber diameter and almost no interfiber sticking, and a method for producing the same, using a base fiber as a starting material.

[0004]

[Means for Solving the Problems]
-Using the fibers proposed in the application of No. 100874, by beating the fibers by conventional means, at least before dipping, dipping / adhering in an aqueous solution of a specific surfactant, and then drying, It was found that an extremely good PVA-based pulp with almost no sticking of the above can be obtained, and the present invention was completed.

More specifically, the present invention comprises a PVA-based polymer (A) and a water-insoluble polymer (B), and one of (A) and (B) is a sea component and the other is an island component. A fibrillated product of sea-island structure fibers, which is a PVA-based pulp in which a nonionic or cationic surfactant is added in an amount of 0.01 to 5% based on the weight of the fibrillated product, and the PVA-based polymer (A) and water. Made of insoluble polymer (B) and has a weight ratio of (A) / (B) of 90 /
At 10 to 20/80, one of (A) and (B) is a sea component and the other is an island component, and the sea-island structural fiber is beaten by adding shearing force in water to give a nonionic or cationic interface. A method for producing a PVA-based pulp, which comprises applying 0.01 to 5% of an activator to the weight of a beaten product, and then drying.

More preferably, the surfactant is selected from quaternary ammonium salt type and silicon type.
One type or a combination of two or more types, and a surfactant having a constituent carbon number of 10 to 50 is used.

Here, in order to obtain ultrafine pulp, the fiber used for producing the pulp of the present invention needs to have a sea-island shape in cross section (perpendicular to the fiber axis direction),
The constituent polymers must be the PVA-based polymer (A) and the water-insoluble polymer (B), and the polymer weight ratio (A) / (B) is preferably 90/10 to 20/80. In PVA-based polymers, the molecular chains are easily oriented and crystallized,
Since high-strength fibrils are easily obtained and they have great hydrophilicity, fibrillation can be easily performed by utilizing this property, and PVA-based polymers have excellent alkali resistance and mechanical performance. A pulp suitable for various purposes is obtained.

The method described in Japanese Patent Application No. 7-100874 can be applied as a method for producing a beating fiber.
That is, the PVA-based polymer (A) is not particularly limited as long as it has a vinyl alcohol unit of 70 mol% or more.
For the water resistance and strength of the obtained pulp, vinyl alcohol units having 95 mol% or more, particularly 98 mol% or more, are preferable, and most preferably 99.8 mol% or more. Further, the degree of polymerization of the PVA-based polymer (A) is not particularly limited, but in order to obtain high-strength fibrils, the degree of polymerization is preferably 500 or more, more preferably 1
It is 500 or more. The PVA-based polymer of the present invention includes ethylene, itaconic acid, vinylamine, acrylamide,
Monomers such as vinyl pivalate, maleic anhydride, and vinyl compounds containing sulfonic acid are used as vinyl alcohol units.
Those which are copolymerized in a proportion of less than 0 mol% are also included. There is no limitation as long as the degree of saponification is 80 mol% or more. Further, the fibers may be cross-linked by acetalization or cross-linking agent in the PVA molecule or between the molecules with formaldehyde, glutaraldehyde or the like for improving hot water resistance.

Examples of the water-insoluble polymer in the fiber of the present invention include substantially water-insoluble polymers selected from polyacrylonitrile-based polymers and cellulose-based polymers. Representative examples of the cellulose-based polymer include cellulose acetate and cellulose itself. These polymers are not compatible with PVA-based polymers, so blending these polymers with PVA-based polymers resulted in phase separation, one polymer being the sea component and the other polymer being the island component, It becomes a so-called sea-island structure. Usually, the major component is the sea component and the minor component is the island component.

A suitable weight ratio of the PVA polymer (A) to the water-insoluble polymer (B) is 90/10 to 20/8.
It is within the range of 0. If it is out of this range, there is a problem in fiber formation of the sea / island structure, which is not preferable. Also good P
In order to obtain VA type pulp in high yield, PVA is a sea component,
Amount ratio of water-insoluble polymer as island component, ie (A)
The weight ratio of / (B) is more preferably within the range of 90/10 to 40/60, and even more preferably within the range of 75/25 to 50/50. In addition to the polymers (A) and (B), the fibers used in the present invention are added with polymers, modifiers, various stabilizers, etc. that do not significantly deteriorate the performance of the fibrillated pulp or the obtained pulp. Good.

The method for producing the fibers used in the present invention is as follows:
Both polymers (A) and (B) are dissolved in a common solvent such as dimethylformamide or dimethylsulfoxide,
The obtained spinning dope is wet- or dry-wet spun through a spinning nozzle into a solidifying bath consisting of alcohols such as methanol and ethanol, ketones such as acetone, methyl ethyl ketone and methyl isopropyl ketone, and aromatic hydrocarbons such as toluene and xylene. , And 2 to 5 times wet drawing, drying at 50 to 130 ° C. and 3 at 200 to 240 ° C.
A method is used in which fibers are formed by carrying out a hot drawing of 15 times to 15 times, and if necessary, a water resistance improving treatment such as saponification and acetalization of PVA. By increasing the draw ratio, due to the difference in drawability between the PVA polymer and the water-insoluble polymer, strain is likely to occur at the sea-island interface, cracking is likely to occur, and fibrillation is facilitated, which is preferable. Therefore, the product of the wet draw ratio and the hot draw ratio is obtained. The total draw ratio represented by is preferably 8 times or more.

Of course, the sea-island structure fiber used in the present invention is
In addition to the method of producing by the polymer blending method as described above, for example, the PVA-based polymer (A) and the water-insoluble polymer (B) are separately dissolved in a solvent, and both polymer streams are added at or immediately before the spinneret portion. A method may also be used in which the fibers are joined, passed through a mixing portion such as a kneading element if necessary, and then discharged from a spinneret and spun. However, the above-mentioned polymer blending method in which both polymers are mixed in advance is preferable from the viewpoint of easy production and easy obtaining of fine fibrils.

The diameter of the fibers which can be stably and easily produced by the above method is usually 10 μm or more. However, this fiber diameter is too thick to be used as a high-performance filter, a powder-holding material for friction materials, and the like, and is not suitable for these applications. For these purposes, the average fiber diameter is preferably 5 μm or less. In the present invention, in order to make the average fiber diameter 5 μm or less, a method of beating the fibers by applying a shearing force in water is used. A preferred specific method is to first cut the fiber to a length of 1 to 10 mm, beat it in water using an ordinary disc refiner or the like to reduce the diameter of the fiber, and then dry it. With this method,
Since the PVA-based polymer (A) in the fiber swells with water, while the water-insoluble polymer (B) does not substantially swell, a large strain occurs in the fiber, and a mechanical shearing force is applied to the fiber having such strain. The addition easily causes the fibers to fibrillate.

The PVA-based pulp obtained by such a method is dried, but the PVA-based polymer has a water-swelling property, so that fibers are stuck to each other in the drying step and the pulp-constituting fibrous material is obtained. It is not possible to obtain a good pulp which is separated. Even if the PVA-based polymer has improved water resistance due to acetalization or the like, the PVA-based polymer has water swelling property, and similarly fibers are stuck together in the drying step.

The greatest feature of the present invention is to avoid such inconvenience, that is, at least 0.01 to 5% of a nonionic or cationic surfactant is added to the above-mentioned water-beaten pulp before drying with respect to the weight of the fiber. After applying owf, it is dried. If the amount of adhesion is less than 0.01% owf, it will be insufficient to prevent interfiber sticking during drying, and conversely if more than 5% owf is applied, the effect of improving the prevention of interfiber sticking will not be improved. No more can be obtained, and the amount of the surfactant used is unnecessarily increased. This surfactant adhesion may be carried out by beating the fibers in an aqueous solution containing a surfactant and as a result adhering to the pulp, or by applying the adhesion treatment before drying in another step. When an anionic surfactant is used, it is not possible to prevent sticking between fibers.

Examples of the above-mentioned surfactants include cationic surfactants represented by quaternary ammonium salts, and examples of the nonionic surfactants include silicon-based ones. Typical examples of the quaternary ammonium salt-based compound include compounds represented by the following chemical structural formulas (1) to (3), and examples of silicon-based compounds include compounds represented by the following chemical structural formula (4). Is mentioned. And
A surfactant having a constituent carbon number of 10 or more and 50 or less is preferable because it effectively prevents interfiber sticking.

[0017]

Embedded image

[0018]

Embedded image

[0019]

Embedded image

[0020]

Embedded image

In the above formulas (1) to (4), R represents an alkyl group. When the number of carbon atoms of the surfactant is less than 10, the effect of preventing interfiber sticking is diminished, which is not preferable. On the other hand, when the carbon number exceeds 50, the hydrophobicity becomes so large that the water solubility is lowered and the solution thereof becomes difficult. Therefore, a carbon number of 10 to 50 is preferable. In this way, the pulp-like material to which the surfactant has been added is dried. The drying temperature is preferably 120 ° C or lower, more preferably 110 ° C or lower. If necessary, the pulp thus obtained may be further fibrillated by a mixer or the like.

As described above, the PVA pulp of the present invention is used for various filters, battery separators such as alkaline manganese batteries, powder holding materials for friction materials such as brakes and shoes, and the like. When
Other synthetic fibers, natural fibers, regenerated fibers, the pulp of the present invention,
Alternatively, they may be used by mixing with a beaten product of these fibers, and as a mixing method, these fibers are added to the PVA sea-island structure fibers and beaten at the same time in the beating step performed when producing the pulp of the present invention. Good.

The present invention is described below with reference to examples, but the present invention is not limited to these examples.
Note that the fiber diameter is obtained from the micrograph of the cross-sectional area of the fiber,
It is the diameter of a circle corresponding to the cross-sectional area, and the diameters of 30 arbitrary diameters were calculated, and the arithmetic mean was calculated from the values.

Example 1 PVA having a degree of polymerization of 1750 and a degree of saponification of 99.9 mol%.
Then, cellulose acetate having a degree of polymerization of 180 and an acetylation degree of 55% (hereinafter sometimes simply referred to as CA) was weighed at a weight ratio of 6: 4, dimethyl sulfoxide (DMSO) was added, and the mixture was heated at 80 ° C. for 10 minutes. In a nitrogen stream for an hour, the mixture was dissolved by stirring to obtain a polymer solution. Using this solution as the spinning dope,
Wet spinning was carried out in a solidification bath at a temperature of 10 ° C. with a DMSO / methanol weight ratio of 30/70 from a spinneret having 400 holes and a pore diameter of 0.10 mmφ, and wet drawing was performed 3 times. After complete extraction at 80 ° C., it is dried with hot air at 80 ° C., and hot-rolled at 225 ° C. with a total draw ratio of 13 times, 1200 denier / 40 consisting of PVA and CA.
A blended fiber of 0f was obtained. Then, it was treated in 1N caustic soda at 50 ° C. for 30 minutes to saponify CA to obtain cellulose. When the cross section of this fiber was observed with a transmission electron microscope, it was a sea-island fiber in which PVA was a sea component and cellulose was an island component.

This fiber was cut into a length of 3 mm using a guillotine cutter. This cut fiber: water bath ratio 1: 2
At 0, using a KRK type desk refiner manufactured by Rigaku Kumagai, with a desk gap of 0.2 mm and a rotation speed of 2OO rpm, 1
Beat for 5 minutes in water. This fiber beating solution was centrifugally dehydrated, and then, against the fiber weight, Brian NS made by Matsumoto Yushi Co., Ltd.
-I70K-2 (a quaternary ammonium salt type cationic surfactant: constituent carbon number 14: belonging to the surfactant represented by the above chemical formula 3) was immersed in an aqueous solution of various concentrations, and
100 ° C after treatment to obtain the same surfactant attachment ratio
It was dried for 30 minutes to obtain a pulp.

With respect to this pulp, the average fiber diameter and the presence or absence of inter-fiber knee attachment were evaluated by a scanning electron microscope. The freeness was measured by a Canadian standard method according to JIS P8121 "Pulp freeness test method". Further, in order to evaluate the powder retaining property as a friction material, calcium carbonate was used for the powder, and fiber / calcium carbonate = 5/1
After mixing in a weight ratio of 00, the mixture was mixed in the above mixer for 10 minutes, and 100 g of the mixture was transferred to a 32 mesh wire mesh sieve, and 1
The vertical vibration was applied 75 times per minute, the weight of the powder that did not fall from the sieve was determined, and the powder retention rate was determined by the following formula. Table 1 shows the results. Powder retention rate (%) = 100 x (amount not passed through sieve-fiber) / powder weight

According to this, the embodiment of the present invention has no inter-fiber sticking, has a small freeness, shows excellent performance in powder retention, and corresponds to the prior art in which no surfactant is added. It was found that the pulp is better than the comparative example and the comparative example in which the amount of the surfactant applied is extremely small.

[0028]

[Table 1]

Example 2 The fibrillated fiber beaten in water and centrifugally dehydrated by the same fiber and method as in Example 1 was used as a quaternary ammonium salt system (Matsumoto Yushi Co., Ltd. VISTA FR-220: constituent carbon number 28: in the above chemical formula 1). Similarly, quaternary ammonium-based (Matsumoto Yushi: Zontes B-8: constituent carbon number 15: belongs to the chemical formula 2), silicon-based (Matsumoto Yushi: Silicon Softener N-20: constituent carbon number 36: the above) The surfactant of the chemical formula 4) was added to the fibers in an amount of 1.0% by weight, and the interfiber adhesion, freeness and powder retention were measured in the same manner as in Example 1. As a comparative example, 1% owf of anionic surfactant sodium oleate was applied and the same evaluation was performed.

As a result, when the three types of the quaternary ammonium salt-based and silicon-based surfactants were used, No. 1 of Example 1 was used. Although the same performance as that of No. 4 was exhibited, when sodium oleate was used, the interfiber adhesion could not be prevented, and the freeness,
The powder retention rate was as poor as that of the prior art of Example 1.

[0031]

According to the present invention, the PVA possessed by the prior art
In the drying step, which was a defect of the system pulp after the fiber fibrillation process by the wet process, the problem of partial pulp sticking between fibers and unevenness of pulp quality was solved, and good productivity was achieved. It enabled the production of homogeneous quality PVA pulp. INDUSTRIAL APPLICABILITY The PVA pulp of the present invention can be used as a fiber material for reinforcing various powders, battery separators such as alkaline manganese batteries, powder holding materials for friction materials such as brakes and shoes, and sealing materials such as gaskets.

Front page continuation (72) Inventor Eiichi Sasakawa 1-1239 Umeda, Kita-ku, Osaka Kuraray Co., Ltd.

Claims (4)

[Claims] 1. A fibril of a sea-island structure fiber comprising a polyvinyl alcohol polymer (A) and a water-insoluble polymer (B), wherein one of (A) and (B) is a sea component and the other is an island component. And a nonionic or cationic surfactant is 0.1.
Polyvinyl alcohol-based pulp provided with 01 to 5%. 2. The pulp according to claim 1, wherein the nonionic or cationic surfactant is a surfactant having 10 to 50 constituent carbon atoms selected from quaternary ammonium salts and silicon. 3. A polyvinyl alcohol polymer (A) and a water-insoluble polymer (B), and (A) / (B)
A weight ratio of 90/10 to 20/80 (A) and (B), one of which is the sea component and the other of which is the island component, is beaten by applying shearing force in water. A nonionic or cationic surfactant is added to the beating material weight of 0.
A method for producing a polyvinyl alcohol-based pulp, which comprises applying 01 to 5% and then drying. 4. The method according to claim 3, wherein the nonionic or cationic surfactant is a surfactant having 12 to 50 constituent carbon atoms selected from quaternary ammonium salt and silicon.