JPH08127915A - Polyolefin synthetic pulp and its production - Google Patents

Abstract

PURPOSE: To obtain a polyolefin synthetic pulp comprising uniformly ultra-fine fibers, excellent in water-holding ability, and capable of quantitatively controlling water filtration time through applying thereto a small amount of a hydrophilicity-imparting agent. CONSTITUTION: This polyolefin synthetic pulp comprises branch-free fibers each 0.2-2.0μm in diameter and/or fiber bundles composed of such fibers. It is preferable that the number of the fibers making up one of the fiber bundles be <=100 and the length(s) of the single fiber and/or bundle >=100 times the diameter of the single fiber. For this synthetic pulp, application of impact force on the fibers or fiber bundles can control the specific surface area to 2-11m<2> /g, bring the water-holding degree to 70-200%, and extend the water filtration time by a factor of <=200.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin-based synthetic pulp and a method for producing the same. More specifically, the fiber diameter is extremely fine, the number of branches in each fiber is small, and the fiber diameter distribution is small. The invention relates to a polyolefin-based synthetic pulp having a narrow size, excellent water retention, and a long drainage time, and a method for producing the same.

[0002]

2. Description of the Related Art Polyolefin-based synthetic pulp is widely used for battery separators, electric paper such as insulating paper, sanitary materials such as disposable diapers, water resistant cardboard, water resistant paper, fiber cement board, heat seal paper, etc. Has been done. As a method for producing this type of polyolefin synthetic pulp, there is one disclosed in Japanese Patent Publication No. 53-12604. That is, a mixture of a solvent selected from aliphatic hydrocarbons and alicyclic hydrocarbons having a boiling point lower than the boiling point of water, 15% by weight or less of the solvent of polyolefin, polyvinyl alcohol, and water in an amount of 2 times or less the volume of the solvent. Is emulsified or suspended at 130 to 160 ° C. and released (flashed) to a low pressure range to obtain a fibrous substance polyolefin dispersed in water. If the fibrous material obtained by such a method is beaten with a refiner or a beater, a fibrillated pulp can be easily obtained.

However, according to the above manufacturing method,
The obtained polyolefin-based synthetic pulp was not always sufficient in water retention when used in certain fields such as battery separators and fiber cement boards, and it was not possible to secure a long drainage time.

The polyolefin synthetic pulp obtained by the above production method has a fiber diameter of 0.2 to 2.
Fibers without branching of about μm are used as basic fibers (basic fibers), and a plurality of these are collected into a bundle, and most of them are 1
It is composed of a bundle of 00 or more. However, since these basic fibers are in close contact with each other and strongly bonded to each other, it is impossible to obtain the large water-retaining power found in synthetic pulp composed of thin fibers such as basic fibers.

On the other hand, by improving the method for producing synthetic pulp by the above-mentioned flush, changing the emulsifying or suspending conditions by adding a surfactant or using a high-speed rotary emulsifier, or polyolefin in a solution. There is known a method of reducing the polymer concentration or changing the volume ratio of water and a polyolefin solvent to increase the water retention capacity at the same time as making the fibers extremely fine (for example, JP-A-3-1805).
No. 04, JP-A-3-180505, JP-A-3
-180506, JP-A-3-180507).

However, the fibers produced by these methods have an inhomogeneous morphology consisting of trunk fibers and branched fibers branching from them, and are therefore used as a material for battery separators. However, the uniform pores cannot be obtained, which adversely affects the battery performance (lifetime, capacity, etc.). In addition, when used by mixing with paint, the trunk fibers impede the smoothness of the coating film after coating, and the diameter distribution of each fiber is
A narrow, thin, and uniform product has not been obtained. Further, in the field of the sealed battery separator, it is required to be effective in low electric resistance and long life. Therefore, the synthetic pulp used in this field is required to be composed of fibers having a finer and uniform fiber diameter, and to have a smaller pore size when paper is made from the fibers. Further, in the coating field of paints, in order to impart dripping prevention property and to maintain smoothness after coating, a polyolefin-based synthetic pulp composed of fibers having a finer and uniform fiber diameter is required. ing.

[0007]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to synthesize a polyolefin-based composition in which the fiber diameter is extremely uniform and extremely fine, has excellent water retention, and the drainage time can be quantitatively controlled by adding a small amount of a hydrophilicity-imparting agent. To provide pulp.

[0008]

The present invention has been proposed to achieve the above object and is characterized by having the following constitution. That is, according to the present invention, the fiber diameter is 0.2 to 2.0 μm and the fiber is composed of a single fiber without branching and / or a fiber bundle in which a plurality of the fibers are assembled. A polyolefin-based synthetic pulp is provided.

Further, according to the present invention, there is provided the above-mentioned polyolefin-based synthetic pulp in which the number of constituent fiber bundles is 100 or less.

Further, according to the present invention, there is provided the above-mentioned polyolefin-based synthetic pulp, wherein the diameter of the constituent fiber bundle is within the range of 0.2 to 2.0 μm.

Further, according to the present invention, there is provided the above-mentioned polyolefin-based synthetic pulp, wherein the constituent single fibers and / or fiber bundles have a length of 100 times or more the diameter of the single fibers.

Further, according to the present invention, there is provided the above-mentioned polyolefin-based synthetic pulp which has a reduced number of aggregates due to the impact of the constituent fiber bundles.

Further, according to the present invention, there is provided the above-mentioned polyolefin synthetic pulp in which the specific surface area of the synthetic pulp is set within the range of ² to 11 m ² / g by reducing the number of aggregated fiber bundles. It

Further, according to the present invention, there is provided the above-mentioned polyolefin synthetic pulp in which the water retention of the synthetic pulp is set within the range of 70 to 200% by reducing the number of aggregated fiber bundles. .

Further, according to the present invention, there is provided the above-mentioned polyolefin-based synthetic pulp in which the drainage time of the synthetic pulp is increased by up to 200 times by reducing the number of aggregated fiber bundles.

Further, according to the present invention, there is provided the above-mentioned polyolefin-based synthetic pulp, wherein the synthetic pulp is a polyethylene-based or polypropylene-based synthetic pulp.

Further, according to the present invention, the synthetic pulp is 2.
The above-mentioned polyolefin-based synthetic pulp containing 0% by weight or less of polyvinyl alcohol is provided.

Further, according to the present invention, there is provided the above-mentioned polyolefin-based synthetic pulp, wherein impact force for reducing the number of aggregated fiber bundles is applied by using a high pressure homogenizer.

In addition, according to the present invention, the number of fiber bundles, which composes the polyolefin-based synthetic pulp and has a fiber diameter of 0.2 to 2.0 μm and is not branched, is set to a high pressure. Provided is a method for producing a polyolefin-based synthetic pulp, which comprises reducing the amount with a homogenizer.

[0020]

DETAILED DESCRIPTION OF THE INVENTION The synthetic pulp according to the present invention will be specifically described below. The polyolefin synthetic pulp according to the present invention has a fiber diameter of 0.2 to 2.0 μm and is composed of a single fiber without branching and / or 0.2 to 2. It is an important technical fact that a single fiber having a fiber diameter of 0 μm and no branching is aggregated and is composed of a fiber bundle in which the fiber diameters of the respective fibers are substantially uniform. This is a feature, which makes the fiber diameter extremely thin,
Provided is a polyolefin-based synthetic pulp which is excellent in water retention and whose drainage time is quantitatively controlled by adding a small amount of a hydrophilicity-imparting agent.

The polyolefin synthetic pulp of the present invention is
It is preferable that the number of aggregated fiber bundles constituting it is 100 or less, particularly 1 to 10. because,
Since the hydrophilicity-imparting agent is attached around the single fibers constituting the fiber bundle, if the single-fiber bundle is small, most of the hydrophilicity-imparting agent is exposed on the fiber surface. When the number of aggregates is 100 or more, most of the hydrophilicity-imparting agent is buried in the fiber bundle, and the amount of the hydrophilicity-imparting agent that exerts an effect on the water retention and hydrophilicity of the fiber is reduced.

The diameter of the constituent fiber bundle is preferably 0.2 to 2.0 μm, more preferably 0.5 to 2.0 μm, since uniform strength after sheet formation is exhibited. The length of one fiber and / or fiber bundle is preferably 100 times or more, particularly preferably 300 times or more of the diameter of a single fiber. When the fiber length is less than 100 times the single fiber diameter, it is difficult to form a sheet and it cannot be used for battery separators.

Specific examples of the polyolefin constituting the synthetic pulp according to the present invention include polyethylene, polypropylene, polybutene-1, and poly-4-methylpentene-.
Examples thereof include polymers of α-olefins such as 1 and copolymers thereof. Of these, polyethylene and polypropylene are preferable.

The polyethylene used in the present invention has a melt flow rate (MFR, ASTM D1238) of usually 0.01 to 30 g / 10 min, preferably 0.03 to 20 g / 10 min, and more preferably 0.5 to 1 g.
It is 5 g / 10 minutes. The polypropylene used in the present invention is a melt flow rate (MFR, ASTM
D1238) is usually 0.01 to 1000 g / 10
Min, preferably 0.1 to 100 g / 10 min, more preferably 1 to 50 g / 10 min. The diameters of these fibers are distributed in the range of 0.2 to 2 μm,
Most of them exist in a narrow range of 0.5 to 2 μm.

In the synthetic pulp having such a form, the hydrophilicity-imparting agent polyvinyl alcohol (PVA) adhering to the fiber at the time of flushing is exposed on the surface without being taken into the inside of the fiber, and thus the hydrophilicity-imparting agent is exposed. It effectively acts to keep the fibers hydrophilic even when the addition amount of is small.
Therefore, the water retention and the drainage time of the physical properties affected by the hydrophilicity of the fiber surface become significantly larger than those of the conventional synthetic pulp.

In the conventional synthetic pulp, when the composition of PVA is 2% or less, the water retention cannot exceed 100% and is almost 90% or less, but the water retention of the synthetic pulp according to the present invention is Although the composition of PVA is 2% or less, it stably exceeds 100%, and the bundle of fibers is loosened according to the impact and shearing energy applied by the high pressure homogenizer. As a result, the number of aggregated fibers is reduced, and it is controlled to a small number of bundles or individual basic fibers, and the water retention is 130 to 200%
Can be

Further, in the conventional synthetic pulp, PV
Under the condition that the composition of A is 2% or less, the drainage time is 4 sec.
However, the water retention of the synthetic pulp according to the present invention exceeds 4 sec / g even if the composition of PVA is 2% or less, and the number of aggregated fibers should be controlled. Can be set to 4 to 30 sec / g.

The method for producing a polyolefin-based synthetic pulp according to the present invention is an Encyclopedia of Ch
electronic Technology 3rd ed.
Vol. 19 pp420 to 425, the method includes, for example, a method in which melt-spun fibers are cut into short pieces and then beaten, and a method in which solution flash or emulsion flash is performed and then beaten. As an example of these manufacturing methods, Japanese Patent Publication No.
The technology disclosed in Japanese Patent No. 2604 can be disclosed.

In the present invention, the synthetic pulp produced by the above-mentioned conventional technique or a commercially available synthetic pulp (for example, "SWP" (registered trademark)) is dispersed in water,
Apply strong impact force and strong shearing force to this dispersion,
By tearing the fibers of the synthetic pulp in the length direction, a synthetic pulp having a fine and uniform fiber diameter is produced.

Here, as the impact force, for example, when the slurry is made to flow from the orifice-shaped pores to the low-pressure side in a state where the pulp slurry is at a high pressure, cavitation, that is, a sudden pressure drop occurs in the liquid. It is possible to exemplify a mode in which bubbles are generated and an impact force caused thereby is applied to the fibers in the slurry. The shearing force may be exemplified by a mode in which the shearing force is applied to the fibers due to the velocity distribution in the flow of the liquid when the high-pressure pulp slurry is flown through the orifice-shaped pores at a high speed. it can.

When the synthetic pulp is magnified and observed with a microscope, the synthetic pulp has a small diameter of about 0.2 μm.
It is composed of non-uniform tissues of various diameters, even those with a large diameter of about μm. However, when the fibers having the large diameter are also closely observed, it is found that the fibers (basic fibers) having a fine diameter of 0.2 to 2.0 μm are gathered and formed. Therefore, when a strong impact force or a strong shearing force is applied, a thin fiber (basic fiber) of 0.2 to 2.0 μm does not become thinner than that,
Thick fibers are unraveled to their constituent fibers of 0.2 to 2.0 μm fine diameter (basic fibers).

Therefore, by increasing the impact force and the shearing force, the distribution of about 0.2 to 100 μ becomes 0.2
To 5 μm, and by further increasing the impact force and the shearing force, a fiber having a uniform fiber diameter distribution of 0.2 to 2 μ is obtained. Further, in the synthetic pulp of the present invention, the impact fiber and the shearing force are applied as described above, so that the aggregate number of the basic fibers constituting the synthetic pulp is 1 to 100.
Controlled by the book.

As a method of applying an impact force and a shearing force, the synthetic pulp dispersion liquid is treated with a pressure difference of at least 100 Kg / cm ² through a small diameter orifice, and collision and cavitation on the vessel wall caused at this time are treated. There is a method to use. The degree to which the fiber diameters are finely uniformized can be set to a desired degree by appropriately changing the pressure difference when passing through the orifice, the number of treatments, and the concentration of the synthetic pulp.
Increase the pressure difference, increase the number of treatments,
Reducing the concentration of the synthetic pulp is effective for making the fibers of the synthetic pulp fine and uniform. These are operations to increase the energy applied to the synthetic pulp per unit weight, and in the end, increasing the impact force and shearing force applied to the synthetic pulp per unit weight is effective in making the fiber diameter thin and uniform. It is thought that there is.

There is a high-pressure homogenizer as a device that gives sufficient impact force and shearing force to loosen the fibers of the synthetic pulp. This is a high-pressure pump for pressurizing the liquid to be treated and a container for supplying the liquid to be treated on its suction side. And a valve for adjusting the differential pressure is attached to the discharge side. Examples of these devices are commercially available as "homogenizers" from APV GAULIN. When the synthetic pulp is treated with this high-pressure homogenizer, the synthetic pulp is dispersed to about 1 to 30 g / liter and treated with a high-pressure homogenizer at a differential pressure of 200 kg / cm ² or more to loosen the fibers of the synthetic pulp. Becomes thin. By repeatedly treating the treated liquid or increasing the differential pressure, the distribution of the fiber diameter becomes 0.2 to 2.0 μm, and at the same time, the specific surface area, water retention and drainage time also increase.

That is, in the polyolefin-based synthetic pulp of the present invention, by repeating the above treatment a predetermined number of times,
The specific surface area can be set within the range of ² to 11 m ² / g, and the water retention is 70 to 200%.
Can be set within the range of, and the drainage time can be increased within the range of up to 200 times.

[0036]

Industrial Applicability According to the present invention, a polyolefin-based synthetic pulp having an extremely fine fiber diameter, a small number of branches of each fiber, and a uniform diameter thereof, which is excellent in water retention. Will be provided. This synthetic pulp, by having the above properties, liquid-retaining articles such as battery separators, cement products such as fiber cement plates, paint thixotropy imparting agents, gas filters, liquid filters, tea bag paper, masks, Absorption sheet or water absorption mat that absorbs ceramics paper, water, oil, solvent, urine, etc., additives for sealers, additives for sealants, additives for caulking materials, additives for adhesives, wire cable covering materials, insulating paper, Book covers, label paper, waterproof paper, paperboard and other molded paperboard, sterilized bag paper, heat-sealed paper, tissue paper, wipes, wallpaper, cushioning floor lining materials, wall reinforcing fibers, tile grout, filter aids. It can be suitably used for applications such as.

[0037]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1 Commercially available synthetic pulp (“SW
30 g of fiber component of "P" (registered trademark) brand: E-400)
(Polyvinyl alcohol content 1.3 wt%) was dispersed in water to prepare a total of 3 liters, and the mixture was preliminarily dispersed by stirring for about 1 minute with a household mixer. After that, apply this to a high pressure homogenizer (APV G
AULIN15MR-8TA) was charged at room temperature and the differential pressure was 5
By repeating the treatment with 00 Kg / cm ² ,
A bundle of fibers (a diameter of about 10 μm) was loosened, and when the number of treatments was increased to 10 or more, the fiber diameter became 2 μm or less. Number of treatments (0 times (before treatment), 5 times, 10
1) to (C), and Table 1 shows the relationship between the number of treatments and these physical properties. In addition, the physical properties change simultaneously with the number of treatments, and as the number of treatments increases, the specific surface area, water retention, drainage time, and the respective measured values also increase. Table 1 shows the relationship between the number of treatments and these physical properties.

Below, the water retention, drainage time and specific surface area were measured.
The setting method is shown.Water retention : J. TAPPI standard method NO. According to 26
Was measured. That is, a sample equivalent to 0.5 g of absolutely dried sample
From the pulp suspension and suction filtered to obtain a uniform mat
Then, spin-dry it with a centrifuge (3000G, 15 minutes
Interval) and weigh the mat after dehydration. Weight before and after dehydration
The water retention was calculated by the following calculation formula.Where A is the weight of the wet pulp after centrifugal dehydration (g) B is the absolute dry weight of the pulp (g) Drainage time : Measured according to TAPPI standard method T221
Was done. That is, with TAPPI standard method T205
Specified sheet machine (diameter 15.88 cm, height 35
Standard sheet (60g / m) using 0mm cylinder² )
The drainage time at 20 ° C at the time of preparation is the drainage time
Was.Specific surface area : N as an adsorption gas according to the BET method₂ 
Ratio table of surface area per sample weight measured using gas
The area. (CARLO EBRA STRUMENTAZIONE SORPTY 17
(Measured by 50)

[0040] From Table 1 above, it became clear that the values of specific surface area, water retention, and drainage time increase as the number of treatments increases.

Example 2 Commercially available synthetic pulp (“SW
30 g of fiber component of "P" (registered trademark) brand: EST-2)
Was dispersed in water, adjusted so as to be 3 liters in total, and treated with a household mixer for about 1 minute to carry out preliminary dispersion. Then, add this to a high pressure homogenizer (A
PV GAURIN 15MR-8TA) is charged at room temperature and treated at a differential pressure of 500 Kg / cm ² . Further, as the number of times of treatment was increased by repeating the operation, the bundle of fibers (diameter of about 10 μm) was loosened, and when the number of times of treatment was 10 or more, the fiber diameter became 2 μm or less. The relationship between the number of treatments (0 times, 5 times, 10 times) and the fineness of the fibers is shown in FIGS. 2A to 2C, which are photographs taken by a transmission optical microscope. Table 2 shows the relationship between the number of treatments and these physical properties.

[0042] From Table 2 above, it has been clarified that the values of water retention and drainage time increase as the number of treatments increases.

Example 3 Commercial synthetic pulp (“SW
30 g of fiber component of "P" (registered trademark) brand: Y-600)
Was dispersed in water, adjusted so as to be 3 liters in total, and treated with a household mixer for about 1 minute to carry out preliminary dispersion. After that, add this to a high pressure homogenizer (APV
GAULIN 15MR-8TA) at room temperature,
Repeating the treatment at a differential pressure of 500 Kg / cm ² , the bundle of fibers (diameter around 10 μm) is loosened as the number of treatments is increased, and when the treatment number is 10 or more, the fiber diameter is 2 μm or less. Became thin. The relationship between the number of treatments (0 times, 10 times, 30 times) and the fineness of the fiber is shown in FIGS. 3 (A) to 3 (C), which are photographs taken by a transmission optical microscope. In addition, the physical properties change simultaneously with the number of treatments, and as the number of treatments increases, the specific surface area, water retention, drainage time, and the respective measured values also increase. Table 3 shows the relationship between the number of treatments and these physical properties.

[0044]

[Brief description of drawings]

FIG. 1 is a drawing-substitute optical micrograph of a polyolefin-based synthetic pulp according to the present invention, in which (A) is a treatment number of 0 times (before treatment), (B) is a treatment number of 5 times, and C)
Indicates the case where the number of processing times is 10.

FIG. 2 is a drawing-substitute optical micrograph of a polyolefin-based synthetic pulp according to the present invention, in which (A) is a treatment number of 0 times (before treatment), (B) is a treatment number of 5 times, C)
Indicates the case where the number of processing times is 10.

FIG. 3 is a drawing-substitute optical micrograph of a polyolefin-based synthetic pulp according to the present invention, where (A) is the number of treatments 0 times (before treatment), (B) is the number of treatments 10 times,
(C) shows the case where the number of times of processing is 30 times.

Front page continuation (72) Inventor Koji Horimoto 3 Chikusaigan, Ichihara-shi, Chiba Mitsui Sekiyu Kagaku Kogyo Co., Ltd. Within the corporation

Claims (12)

[Claims] 1. A fiber having a fiber diameter of 0.2 to 2.0 μm and having no branching, and / or is composed of a bundle of a plurality of fibers. Polyolefin synthetic pulp. 2. The polyolefin-based synthetic pulp according to claim 1, wherein the number of aggregated fiber bundles is 100 or less. 3. The polyolefin synthetic pulp according to claim 1, wherein the diameter of the constituent fiber bundle is in the range of 0.2 to 2.0 μm. 4. The polyolefin synthetic pulp according to claim 1, wherein the constituent single fibers and / or fiber bundles have a length of 100 times or more the diameter of the single fibers. 5. The polyolefin-based synthetic pulp according to claim 1, wherein the constituent fiber bundles have a reduced number of aggregates when an impact force is applied. 6. The specific surface area of synthetic pulp is reduced to 2 to 11 m ² by reducing the number of aggregated fiber bundles.
6. The polyolefin-based synthetic pulp according to claim 5, which is set within a range of / g. 7. The water retention of the synthetic pulp is 70 to 200% by reducing the number of aggregated fiber bundles.
The polyolefin-based synthetic pulp according to claim 5, which is set within the range. 8. The polyolefin synthetic pulp according to claim 5, wherein the drainage time of the synthetic pulp is increased up to 200 times by decreasing the number of aggregated fiber bundles. 9. The polyolefin-based synthetic pulp according to claim 1, wherein the synthetic pulp is a polyethylene-based or polypropylene-based synthetic pulp. 10. The polyolefin-based synthetic pulp according to claim 9, wherein the synthetic pulp contains 2.0% by weight or less of polyvinyl alcohol. 11. The polyolefin-based synthetic pulp according to claim 5, wherein impact force application for reducing the number of aggregated fiber bundles is performed by using a high-pressure homogenizer. 12. A high-pressure homogenizer is used to reduce the number of aggregated fiber bundles of a plurality of single fibers having a fiber diameter of 0.2 to 2.0 μm and having no branching, which constitutes the polyolefin-based synthetic pulp. A method for producing a polyolefin-based synthetic pulp, comprising: