JPH03180506A - Production of synthetic pulp - Google Patents

Abstract

PURPOSE:To obtain the title pulp excellent in water retentivity, for water- resistant papers, papers for electrical applications, etc., by flash spinning of an oil-in-water-type polymer solution consisting of specified proportions of polyvinyl alcohol, polyolefin and surfactant and a solvent and water followed by recovery and heating the polyolefin. CONSTITUTION:An oil-in-water-type polymer solution in an emulsified or suspended state, consisting of (A) polyvinyl alcohol, (B) a polyolefin, (C) a surfactant, (D) water and (E) a solvent with a boiling point lower than that of water, with the weight ratio of the component A to the component B being (0.1:100)-(30:100) and the weight ratio of the component A to the component C (1:0.7)-(1:20), is put to flash spinning. Thence, the polyolefin is recovered in the form of a water-dispersed fibrous material and beaten, thus obtaining the objective synthetic pulp.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a method for producing synthetic pulp, and more particularly to a method for producing polyolefin synthetic pulp by a so-called emulsion flash spinning method.

Technical background of the invention Polyolefin synthetic pulp can be used as battery separators,
It is widely used in electrical paper such as insulating paper, sanitary materials such as disposable diapers, water-resistant cardboard, water-resistant paper, fiber cement board, heat seal paper, etc.

However, conventional polyolefin synthetic pulp
Separators for batteries In certain applications, such as fiber cement boards, water retention has not always been sufficient.

Therefore, the emergence of polyolefin-based synthetic pulp with excellent water retention has been desired for some time.

By the way, as a conventionally known method for manufacturing polyolefin synthetic pulp, an emulsified or suspended polyolefin polymer solution under high temperature and high pressure is jetted (flashed) into a receiving tank under low temperature and low pressure to produce polyolefin synthetic pulp. There is a method in which a fibrous material in which a polymer is dispersed in water is recovered (a type of so-called emulsion flash spinning method), and then this fibrous material is beaten with a refiner or the like to obtain a polyolefin synthetic pulp.

For example, Japanese Patent Publication No. 53-12604 describes a solvent selected from aliphatic hydrocarbons and alicyclic hydrocarbons having a boiling point lower than that of water, a polyolefin of up to 15% by weight of the solvent, polyvinyl alcohol, and two solvents. It consists of a mixture containing water in an amount equal to or less than twice the volume, and a surfactant,
Furthermore, a method is disclosed in which a polymer solution in an emulsified or suspended state at a high temperature is jetted (flashed) into a low pressure region to recover polyolefin as a fibrous material dispersed in water.

According to the publication, fibrillated pulp can be easily obtained by beating the fibrous material obtained by such a method using a refiner beater. Note that this publication does not describe anything about the water retention properties of synthetic pulp obtained from fibrous materials.

Japanese Patent Publication No. 51-30808 discloses that a water-in-oil emulsion consisting of a solvent solution of a hydrophobic synthetic polymer such as polyolefin and an aqueous solution of a hydrophilic polymer such as polyvinyl alcohol is pumped through an orifice under low pressure. Disclosed is a method for producing synthetic polymeric fibrous structures by spraying a synthetic polymeric fiber structure into a synthetic polymeric fiber structure. According to the same publication, the fiber structures obtained by such a method can be produced very easily by simply cutting the stable ones as they are, or cutting the filament structures appropriately, suspending them in water, and beating them. It is said that by splitting and fibrillating, a synthetic pulp with extremely excellent properties for use in paper making etc. can be obtained. Although the same publication states that the synthetic polymer fibrous structure obtained by the above method has appropriate hydrophilicity, the synthetic polymer fibrous structure obtained by beating the synthetic polymer fibrous structure There is no mention of the water retention properties of the pulp.

JP-A No. 53-24410 discloses that a liquid containing an organic solvent for a thermoplastic resin such as polyolefin and an aqueous solution of a hydrophilic resin such as polyvinyl alcohol is heated at elevated temperature and pressure and the average residence time is 5 minutes or less. Mix to form an emulsion using a continuous emulsifier having an internal volume of
A method for flash spinning this emulsion is disclosed. According to the publication, it is possible to stably obtain synthetic pulp with advanced microfibrillation, high opacity, and disintegrability for horses by such an emulsion spinning method. Note that this publication does not describe anything about the water retention properties of the synthetic pulp obtained by beating the above-mentioned degradable synthetic pulp for horses.

Purpose of the Invention The present invention is directed to the production of polyolefin-based synthetic pulp that has an extremely fine average fiber diameter of 1 μm or less for the entire fibers of the main fibers and branched fibers, retains the characteristics of conventional polyolefin-based synthetic pulp, and has excellent water retention. The purpose is to provide a method.

Summary of the Invention The first method for producing synthetic pulp according to the present invention comprises a solvent having a boiling point lower than that of water, a polyolefin, water, polyvinyl alcohol, and a surfactant, and the weight ratio of the polyvinyl alcohol to the polyolefin is 0.1/100 to 30/100, and the weight ratio of the polyvinyl alcohol to the surfactant is in the range of 110.7 to 1/20.
The oil-in-water type polymer solution in an emulsified or suspended state is flash-spun to recover the polyolefin as a fibrous material decomposed in water, and then the polyolefin fibrous material is beaten to obtain synthetic pulp. It is characterized by

Further, the second method for producing synthetic pulp according to the present invention includes a solvent having a boiling point lower than that of water, a polyolefin, water,
Contains polyvinyl alcohol and a surfactant, and the weight ratio of the polyvinyl alcohol to the polyolefin is within the range of 0.1/100 to 30/100, and the weight ratio of the polyvinyl alcohol to the surfactant is 110.7 to 1. consisting of a mixture within the range of /20,
An oil-in-water polymer solution in an emulsified or suspended state is stirred at a rotation speed of 400 to 10,000 using a high-speed stirrer.
After stirring under rpm conditions, the polymer solution is flash-spun to recover polyolefin as a fibrous material dispersed in water, and then the polyolefin fibrous material is beaten to obtain synthetic pulp. There is.

DETAILED DESCRIPTION OF THE INVENTION The method for producing synthetic pulp according to the present invention will be specifically described below.

First, an oil-in-water polymer solution in an emulsified or suspended state is prepared.

The polymer solution in an emulsified or suspended state used in the present invention is an oil-in-water emulsion, and includes a solvent,
The groove bottom contains polyolefin, water, polyvinyl alcohol and a surfactant.

The type of polyolefin used in the present invention is not limited as long as there is a solvent that dissolves the polyolefin and the polyolefin has molecular orientation. Specifically, the polyolefin used in the present invention includes polyethylene, polypropylene, polybutene (, poly4
Examples include α-olefins such as -methylpentene-1, and copolymers thereof. Among them, polyethylene and polypropylene are preferred. In particular, polyethylene with a viscosity average molecular weight of 10,000 or more and a molecular weight of 5
Polypropylene of 0.0 CIO or more is preferred.

In the present invention, the concentration of polyolefin in the solvent (at room temperature) is usually 0.1 to 500z/D, preferably 1
It is within the range of 0 to 200 s-/R.

In the present invention, the concentration of polyolefin in the solvent (
If the polymer solution is subjected to emulsion flash spinning while the temperature (at normal temperature) is set within the above range, short fibers with a small diameter can be obtained without forming continuous strings.

The solvent used in the present invention has a boiling point lower than that of water, and typically a hydrocarbon solvent is used. For example, hydrocarbon solvents used for polyolefins such as polyethylene and polypropylene include aliphatic hydrocarbons such as pentane, n-hexane, isohexane, heptane, hexene, and pentene, cyclopenkune, and cyclohexane. , alicyclic hydrocarbons such as cyclohexene, aromatic hydrocarbons such as benzene, toluene, and xylene, and halogenated hydrocarbons such as carbon tetrachloride and chlorobenzene. Among them, n-hexane,
Isohexane, heptane, cyclohexane, etc. are preferably used.

In the present invention, water is used, and the volume ratio of water to the solvent (water/solvent) is usually in the range of 1/1 to 10/1, preferably 115 to 5/1.

In the present invention, by setting the concentration of polyolefin to the solvent (at room temperature) and the volume ratio of water to the solvent within the above ranges, the average fiber diameter of the entire fibers of the main fibers and branched fibers is 1 μm or less. Extremely thin,
A polyolefin synthetic pulp that retains the properties of conventional polyolefin synthetic pulp and has excellent water retention can be obtained.

In the present invention, polyvinyl alcohol is used in a weight ratio of 0.1/100 to polyolefin (polyvinyl alcohol/polyolefin).
30/100, preferably 0.3/100 to 10/10
It is used in amounts within the range of 0.

Polyvinyl alcohol has the effect of imparting hydrophilicity to synthetic pulp as well as water dispersibility to synthetic pulp.

The surfactant used in the present invention is appropriately selected depending on the type of polyolefin and solvent, and the quantitative relationship between the solvent and water.

Specifically, the surfactants used in the present invention include:
Examples include nonionic surfactants, cationic surfactants, anionic surfactants, amphoteric surfactants, polyacrylic acid, gelatin, and the like, with anionic surfactants being preferred.

In the present invention, the surfactant is used in a weight ratio of polyvinyl alcohol to surfactant (polyvinyl alcohol/surfactant) of 110.7 to 1/20, preferably 1/20.
It is used in an amount within the range of /2 to 1/10.

In the present invention, by using the surfactant in the above amount, the emulsion stability of the polymer solution is further improved, and short fibers with a small diameter can be recovered by flash spinning. A polyolefin-based synthetic pulp in which the average fiber diameter of the branched fibers as a whole is even finer can be obtained.

Further, in the present invention, a neutralizing agent such as sodium carbonate may be used as necessary within a range that does not impair the purpose of the present invention.

The oil-in-water type polymer solution in an emulsified or suspended state used in the present invention is composed of the above-mentioned components. Examples include a method of stirring and mixing a polyolefin solution prepared by dissolving polyolefin in a solvent, an aqueous polyvinyl alcohol solution, and a surfactant, and a method of stirring and mixing a solvent, polyolefin, water, polyvinyl alcohol, and a surfactant at the same time.

Next, the oil-in-water type polymer solution in the emulsified or suspended state is flash-spun to recover the polyolefin as a fibrous material dispersed in water.

Examples of the above-mentioned flash spinning method include the method disclosed in Japanese Patent Publication No. 12804/1983 filed by the applicant of the present application. That is, in this method,
An oil-in-water type polymer solution that is emulsified or suspended at a temperature of 130 to 160°C is heated under autogenous pressure to 15 kg.
By ejecting (flashing) from a pressure region of /cj (gauge pressure) to a low pressure region, all of the solvent and a portion of the water are flash-evaporated, and the polyolefin is recovered as a polyolefin fibrous material dispersed in water.

In the present invention, immediately before flash spinning the above polymer solution, a high-speed stirrer is used to spin the polymer solution at a rotation speed of 400 to 1000 rpm.
,000 rpm1 preferably 2.000-10,000
It is preferable to stir at rpm.

Finally, the polyolefin fibers dispersed in the water recovered as described above are beaten to obtain synthetic pulp.

The above-mentioned beating can be carried out using a conventionally known beating machine, such as a sofiner beater. Further, in the present invention, the polyolefin fibrous material is beaten by adjusting the concentration of the polyolefin fibrous material to usually 1 to 100 g/ff, preferably 5 to 50 g/.rho.

In the present invention, an oil-in-water polymer solution in an emulsified or suspended state containing a solvent, polyolefin, water, polyvinyl alcohol, and a surfactant in specific proportions is spun by flash spinning or high speed spinning. Since flash spinning is carried out with stirring, short fibers with a narrow diameter are obtained, which are degradable for horses.Furthermore, since these short fibers are beaten, the overall fiber content of the main fibers and branch fibers is reduced. A polyolefin synthetic pulp with an extremely fine average fiber diameter of 1 μm or less, extremely strong capillary action, and excellent water retention can be obtained.

Effects of the Invention According to the present invention, a polyolefin synthetic pulp has an extremely fine average fiber diameter of 1 μm or less for the entire fibers of the main fibers and branched fibers, retains the characteristics of conventional polyolefin synthetic pulp, and has excellent water retention properties. is obtained.

The above-mentioned effects of the present invention are usually greater when a high-speed stirrer is used, and when a surfactant is used as a component of the polymer wave dissipation.

The polyolefin fha pulp obtained by the present invention has an average fiber diameter of 1 μm as a whole of the main fibers and branched fibers.
It is ultra-fine, less than 1.2 ft (m) in diameter, and has excellent water retention properties, so it can be used as battery separators, fiber cement products, paint thixotropy agents, gas filters, liquid filters, tea bag paper, masks, ceramic paper, water, oil, solvents, etc. Absorbent sheets or water-absorbing mats that absorb urine, etc., additives for sealers, additives for sealants, additives for caulking materials, additives for adhesives, electric wire and cable covering materials, insulating paper, bu-nkukano〈-, label paper, Waterproof paper, molded paperboard such as paper plates, sterile paper, knob paper, heat seal paper, tissue paper, towel paper, wipes, wallpaper, backing material for cushion floors, reinforcing fibers for wall materials, tile grout, filter aids. It can be used for purposes such as.

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

In addition, the average fiber diameter of the entire fibers of the main fibers and branched fibers of the synthetic pulp in Examples and Comparative Examples and the water retention degree of the synthetic pulp are determined by the following method.

[Measurement method] (1) Average fiber diameter of all main fibers and branched fibers Measure the average fiber diameter using a scanning electron microscope.

(2) Water retention of synthetic pulp First, in a cylinder with an inner diameter of 50 mm with a wire mesh attached to the bottom, a synthetic pulp concentration of 5sr1500ml (water temperature 20±2
Add 500 ml of a synthetic pulp water slurry adjusted to a temperature of

Next, the water is drained from the bottom of the cylinder, and the water-containing synthetic pulp remaining on the wire gauze is taken out, its weight is measured, and the water retention degree of the synthetic pulp is calculated using the following formula.

(Weight of six precepts pulp containing water) - (Dry 11 l of synthetic pulp) Water retention - (Dry weight of synthetic pulp) In the present invention, the average value of the water retention obtained by measuring three times is used to determine whether the synthetic pulp The water retention level is assumed to be .

Example 1 In a 30 g autoclave equipped with a stirrer and equipped with a baffle plate, 1011 n-hexane (23°C) and 1 O water were added.
N (23°C), 8 ml of 2.5% by weight aqueous sodium carbonate solution, high-density polyethylene [melt flow rate (ASTM D 1238-86): 6 g
/ 10 minutes, density: 0.968g/a! ] 1kg
, and 240 g of sodium dodecylbenzenesulfonate [trade name: Neoperex F-25, manufactured by Kako Oki Co., Ltd., an aqueous solution with a solid content of 25%] as an anionic surfactant, and stirred and mixed. :99
%, 4% aqueous solution viscosity (20°C): 5.0 cps, trade name Gohsenol Nu, -05, manufactured by Nippon Gosei Chemical Industry ■] 1
0g of the mixture was added, and while stirring at a rotational speed of 900 rpm, the temperature of the mixed liquid was raised to 140°C. Then, the temperature of the mixed solution is maintained at 140° C., and stirring is continued for an additional 30 minutes to obtain a suspension.

Next, this suspension is flashed through a vibrator from a nozzle with a diameter of 3 mm attached to an autoclave into a drum under a nitrogen atmosphere and under pressure below atmospheric pressure to obtain a fibrous material.

Next, the fibrous material is made into a water slurry with a concentration of 10z/M in a receiver, and then refined in a disc-type refiner with a diameter of 12 inches to obtain a pulp-like material.

The synthetic pulp thus obtained has an average fiber diameter of 0.5 μm for the entire fibers of the main fibers and branched fibers, and has a water retention degree 30 times that of the synthetic pulp.

Example 2 In Example 1, n-hexane IOI (
23°C) Water 10II (23°C) High density polyethylene [melt flow rate (ASTM D 1238-88
): 1, Og / 10 minutes, density = 0.964g
/-1500g, Poval [PVA.

Saponification degree: 98%, 4% aqueous solution viscosity (20°C): 6, Q
cps, trade name Denka Poval -05, manufactured by Denki Kagaku Kogyo ■] 10 g, and sodium alkanesulfonate as an anionic surfactant [trade name Latemul PS1 manufactured by Kao ■]
A pulp-like material is obtained in the same manner as in Example 1, except that .

The synthetic pulp thus obtained has an average fiber diameter of 0.3 μm for all the main fibers and branched fibers, and has a water retention degree 35 times that of the synthetic pulp.

Example 3 In Example 2, the suspension of Example 2 was passed through a pipe from an autoclave at a flow rate of 847/min,
High-speed stirrer with a rotational speed of 4.20 Orpm [Product name: TK Homo Mic Line Flow, manufactured by Tokushu Kika Kogyo Co., Ltd., capacity: 1.3
II, rotor diameter: 3cI1110-gap between rotor and stator: 0.5m+s], and passed through a pipe from a 3m+s diameter nozzle attached to the outlet of the high-speed stirrer under a nitrogen atmosphere and at less than atmospheric pressure. A pulp is obtained in the same manner as in Example 1, except that it is flushed into a drum under pressure.

The synthetic pulp obtained in this way has an average fiber diameter of 0.0000. 1 μm,
Also, the water retention rate is 50 times higher than that of synthetic pulp.

Comparative Example 1 A pulp-like material is obtained in the same manner as in Example 1, except that the anionic surfactant is not used.

The synthetic pulp thus obtained has an average fiber diameter of 20 μm for all the main fibers and branched fibers, and has a water retention degree 15 times that of the synthetic pulp.

Comparative Example 2 In Example 3, the amount of anionic surfactant was 5g.
A pulp-like material is obtained in the same manner as in Example 3 except that.

The synthetic pulp thus obtained has an average fiber diameter of 0.6 μm for all the main fibers and branched fibers, and has a water retention degree 25 times that of the synthetic pulp.

Claims (2)

[Claims] (1) Contains a solvent with a boiling point lower than the boiling point of water, polyolefin, water, polyvinyl alcohol and a surfactant,
and the weight ratio of the polyvinyl alcohol to the polyolefin is within the range of 0.1/100 to 30/100, and the weight ratio of the polyvinyl alcohol to the surfactant is within the range of 1/0.7 to 1/20. consisting of a mixture,
An oil-in-water polymer solution in an emulsified or suspended state is flash-spun to recover polyolefin as a fibrous material dispersed in water, and then the polyolefin fibrous material is beaten to obtain synthetic pulp. A method for producing synthetic pulp, characterized by: (2) containing a solvent with a boiling point lower than the boiling point of water, polyolefin, water, polyvinyl alcohol, and a surfactant;
and the weight ratio of the polyvinyl alcohol to the polyolefin is within the range of 0.1/100 to 30/100, and the weight ratio of the polyvinyl alcohol to the surfactant is within the range of 1/0.7 to 1/20. consisting of a mixture,
An oil-in-water polymer solution in an emulsified or suspended state is stirred at a rotation speed of 400 to 10,000 using a high-speed stirrer.
After stirring under rpm conditions, the polymer solution is flash-spun to recover polyolefin as a fibrous material dispersed in water, and then the polyolefin fibrous material is beaten to obtain synthetic pulp. A method for producing synthetic pulp.