JPH06256559A - Production of porous resin molded body - Google Patents

Abstract

PURPOSE:To obtain the subject molded body useful as a separation membrane for battery separators, etc., clothes, etc., by adding a specific compound to a matrix resin, molding the resultant mixture and then removing the compound from the molded body without using an organic solvent having strong inflammability. CONSTITUTION:(A) A compound, sparingly soluble in water and having <=100 deg.C) melting point and compatibility with a matrix resin such as polyethylene is added to (B) the matrix resin and then molded. The resultant molded body is then subjected to the treatment with (C) an aqueous solution of a surfactant, heated at the melting point of the component (A) or above, preferably at 50-98 deg.C and preferably converted into steam together with mechanical vibration to remove the component (A) from the resultant molded body. Thereby, the objective molded body is obtained. Furthermore, the removed components (A) and (C) can be circulated for use.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to the production of a porous resin molding useful as a battery / separator, a separation membrane such as a microfiltration membrane, clothing such as an air-permeable jumper, sanitary articles such as diapers and sanitary articles. It is about the method.

[0002]

2. Description of the Related Art Porous resin moldings such as porous films and sheets have been widely used for various purposes. For example, a porous resin molding for use as a battery separator generally forms a film or sheet from a resin composition composed of ultra-high molecular weight polyethylene and a plasticizer such as stearyl alcohol, and then,
The plasticizer contained in the film or sheet is treated with an organic solvent such as isopropanol, ethanol or hexane,
It was manufactured by extracting and removing.

[0003]

However, since the organic solvent used in the conventional plasticizer removing step is highly flammable, it is possible to form a continuous process with the film or sheet extrusion molding step which is the preceding step. It was extremely difficult and productivity was extremely poor. In addition, even if an attempt is made to recover the plasticizer extracted in the organic solvent in order to reuse it, the organic solvent is a good solvent for the plasticizer, so it is difficult to separate it, and the production cost of the porous resin molding can be reduced easily. I couldn't.

[0004]

The inventors of the present invention have conducted extensive studies to provide a method for producing a porous resin molded body in which the above problems have been solved. It has been found that the intended purpose can be achieved by removing the plasticizer from the molded body by making the plasticizer in a molten state and removing the plasticizer from an aqueous solution containing a surfactant in water which is a poor solvent for the plasticizer. The present invention has been completed.

That is, the gist of the present invention is that it is difficult to dissolve in water,
A compound having a melting point of 100 ° C. or less and having compatibility with the matrix resin under the melt-kneading condition of the matrix resin is added to the matrix resin and molded, and the obtained molded body is heated to a temperature not lower than the melting point of the compound. The method for producing a porous resin molded body is characterized in that the compound is removed from the molded body by treating with an aqueous solution of a surfactant to obtain a porous molded body.

The present invention will be described below. As the matrix resin of the resin composition used in the present invention, a matrix resin having a melting point higher than that of a compound which is hardly soluble in water (referred to as a poorly water-soluble compound) will be described later. There is no particular limitation, and examples thereof include polyolefin resins such as polyethylene and polypropylene, nylon resins, and polyester resins.

Among them, the viscosity average molecular weight is 5 × 10.^Five~ 4x
10⁶, Preferably 1.5 × 10 ⁶~ 2.5 × 10⁶
Ultra-high molecular weight polyethylene can be preferably used. The present invention
The sparingly water-soluble compound used in
Has good compatibility (dispersibility) with a matrix resin
Melting point lower than that of matrix and melting temperature of matrix resin
Has a higher boiling point. For example, conventional porous resin moldings
Examples of the plasticizer used in the production of
Paraffin wax, which is solid at room temperature, or
Is high in stearyl alcohol, ceryl alcohol, etc.
-Grade aliphatic alcohols, n-decane and n-do which are liquid at room temperature
N-alkanes such as decane, liquid paraffin, kerosene
Which can be suitably used.

The compatibility of the water-insoluble compound with the matrix resin is good or poor depending on whether or not the melt-kneaded body of these two components is a uniform dispersion system at a temperature of 160 to 200 ° C. and can be stably melt-extruded. Divide. Specifically, when a large number of apparent viscosities of the melt-kneaded product are measured with a flow tester, those having stable fluidity with a swing range of 30% or less, preferably 10% or less are considered to have good compatibility. To do.

The ratio of the matrix resin and the poorly water-soluble compound used is usually 5 to 60% by weight, preferably 10 to 50% by weight of the matrix resin and 40% by weight of the poorly water-soluble compound.
To 95% by weight, preferably 50 to 90% by weight. In the present invention, the resin composition may further contain various known additives such as antioxidants in an amount of about 0.01 to 5% by weight in the resin composition.

The respective components of the above resin composition are uniformly kneaded by a known uniaxial or biaxial extruder and melt-extruded.
A twin-screw extruder is preferably used in terms of extrusion amount and extrusion stability. The melt extrusion molding is usually carried out at a temperature of 140 to 240 ° C. and extruded into a film or sheet with a thickness of 5 to 50 μ or 50 to 300 μ.

In the present invention, the melt-extruded film or sheet is cooled by a conventional method, and then the poorly water-soluble compound contained in the film or sheet is removed to make it porous. The removal of the poorly water-soluble compound is performed by treating the molded body with an aqueous solution containing a surfactant.

[0012] For example, the obtained molded product is prepared by subjecting it to a melting point of the poorly water-soluble compound to a boiling point of the aqueous solution, usually 50 to 98.
Examples include a method of immersing in an aqueous solution containing a surfactant kept at 80 ° C., preferably 80 to 95 ° C., a method of treating with an aqueous solution containing a surfactant with steam, and the like.
Examples of the surfactant include anionic surfactants that form anions such as sodium carboxylate, sodium sulfonate, and sulfate / sodium, and cationic surfactants that form amino groups, imide groups, quaternary ammonium bases, and the like. Although any of nonionic surfactants such as polyoxyethylene glycol type and polyhydric alcohol type can be used, anionic surfactants, particularly sodium alkylbenzenesulfonate, sodium alkylnaphthalenesulfonate, etc. It can be preferably used.

The surfactant is contained in water in an amount of 0.1% or more, preferably 0.5 to 20%, particularly preferably 1.5 to 10.
It is contained in the range of 4%. When the sparingly water-soluble compound is removed by the dipping treatment, the removal efficiency can be improved by applying mechanical vibration such as ultrasonic waves or stirring. When performing ultrasonic treatment, the frequency is usually 10KH
z or more, preferably 20 to 60 KHz, ultrasonic output per unit amount of water is 2 W / l or more, preferably 10 W / l or more, particularly 15 to 50 W / l, for 30 seconds or more, preferably for 1 to 30 minutes It is good to do under the conditions.

When the stirring treatment is carried out, the power required for stirring per unit volume is usually 5 W / m ³ or more, preferably 40 to 2,200 W / m ³ , and 30 seconds or more, preferably 2 to It can be performed under the condition of 30 minutes. The film or sheet perforated as described above may be uniaxially or biaxially stretched according to a conventional method in order to improve mechanical strength or air permeability, or to make the pores microporous depending on its use. Alternatively, heat setting may be performed at about 100 to 180 ° C.

Thus, the porous resin molding of the present invention having good mechanical strength and air permeability can be obtained.

[0016]

EXAMPLES The present invention will be described in more detail with reference to the following examples. Example 1 20 parts by weight of ultra-high molecular weight polyethylene powder having a melting point of 135 ° C. and a molecular weight (viscosity average) of 2 × 10 ⁶ and 80 parts by weight of stearyl alcohol were supplied to an extruder having a diameter of 40 mm.
Continuously extruding from a T-die with a width of 400 mm and a die gap of 1 mm while kneading at 230 ° C, and the draft rate was 13
And then cooled to obtain a sheet having a film thickness of 70 μm.

The sheet obtained was kept at 80 ° C. for 4 minutes.
Immersed in an aqueous solution containing sodium alkylbenzene sulfonate (%), frequency 40 KHz, output 25 W per unit amount of water
Ultrasonication was performed for 170 seconds under the condition of 1 / l to remove the stearyl alcohol in the sheet until the concentration in the sheet became 0.3%. Then, heat treatment was performed for 30 seconds with a heating pinch roll having a surface temperature of 125 ° C. to obtain a porous resin molded body having a film thickness of 34 μm. The characteristics of this molded product are shown in Table 1.

Example 2 30 parts by weight of ultra high molecular weight polyethylene powder having a melting point of 135 ° C. and a molecular weight (viscosity average) of 2 × 10 ⁶ and 70 parts by weight of stearyl alcohol were fed to an extruder having a diameter of 40 mm.
Continuously extruding from a T-die with a width of 400 mm and a die gap of 1 mm while kneading at 230 ° C, and the draft rate is 1
The film thickness is 100 μm after being taken to 1.4 and cooled.
Got a sheet of.

The sheet obtained was kept at 90 ° C. for 2 minutes.
% Alkylbenzene sulfonate aqueous solution and treated with a stirrer equipped with a propeller blade for 290 seconds while stirring with a power equivalent to 75 W / m ³ required for stirring per unit volume. It was removed until the inside concentration became 0.5%. Then, heat treatment was performed for 30 seconds with a heating pinch roll having a surface temperature of 125 ° C. to obtain a porous resin molded body having a film thickness of 66 μm. The characteristics of this molded product are shown in Table 1.

[0020]

[Table 1]

[0021]

INDUSTRIAL APPLICABILITY In the present invention, since the poorly water-soluble compound is removed with an aqueous solution which is a poor solvent, the poorly water-soluble compound contained in the treatment liquid can be easily separated and recovered, and the poorly water-soluble compound and the aqueous solution can be circulated. It can be used. Further, since there is no problem of ignition in the conventional organic solvent method, it becomes possible to form a continuous process with the film or sheet extrusion molding step.

Claims (4)

[Claims] 1. A molding obtained by adding a compound having a melting point of 100 ° C. or less, which is hardly soluble in water, and having compatibility with the matrix resin under the conditions of melt-kneading of the matrix resin, to the matrix resin and molding the mixture. A method for producing a porous resin molded article, characterized in that the compound is removed from the molded article by treating the body with an aqueous solution of a surfactant heated to a temperature above the melting point of the compound to obtain a porous molded article. . 2. The temperature of the aqueous solution of the surfactant is 50 to 98.
The method for producing a porous resin molded product according to claim 1, wherein the temperature is set to be ° C. 3. The method for producing a porous resin molded product according to claim 1, wherein mechanical vibration is also used when the treatment is carried out with an aqueous solution of a surfactant. 4. The method for producing a porous resin molded product according to claim 1, wherein the aqueous solution of the surfactant is treated with steam.