JPH02261837A - Preparation of porous film - Google Patents

Abstract

PURPOSE:To make it possible to control diameter, number and distribution of pores and to improve the uniformity of the fine pore diameter by dissolving and removing CaCO3 in a CaCO3-contg. resin film obtd. by coating a base plate with a resin soln. wherein CaCO3 particles are dispersed or spreading the soln. on the base plate. CONSTITUTION:50 to 200 pts.wt. precipitated CaCO3 particles with a mean particle diameter of 0.02 to 20mum and, if necessary, a dispersing agent, a thickening agent, a film-forming auxiliary, a plasticizer, etc., are added to 100 pts.wt. resin (e.g. PVC) soln. with a concn. of 15 to 50wt.% or liq. mixture of a resin (e.g. phenol resin) and a reactive liq. monomer (e.g. styrene). Then, a CaCO3- contg. resin film is obtd. by coating a base plate with this soln. or spreading this soln. on the base plate and evaporating and removing the solvent or curing it. Then, this resin film is immersed in an acid soln. with a concn. of 5 to 20wt.% for 1 to 10hr to dissolve and remove CaCO3.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a porous membrane, and more particularly to a method for manufacturing a porous membrane in which the pore diameter, number of pores, and pore distribution can be freely controlled.

The porous membrane obtained by the method of the present invention has a precise pore structure and can be used, for example, in precision membrane materials, sustained release materials, breathable waterproof membranes, sanitary products such as disposable diapers, etc. Useful as a surcharge material and sustained release material.

Conventional technology The conventional method for producing porous polymer membranes includes (a) dissolving a resin in a good solvent and casting it onto a substrate to a certain thickness;
A dry method in which the conditions are precisely controlled and the solvent is removed by evaporation, (b) a wet method in which the resin is dissolved in a good solvent, cast onto a substrate to a certain thickness, and then coagulated with a poor solvent; (c) Stretching method in which the membrane is stretched under specific conditions, (d) Micropores are formed in the resin using radiation or electron beams, and these areas are dissolved with a specific solvent.
A charged track etching method for enlarging the pores, and (e) a solvent extraction method for mixing an elutable substance into a resin and removing the substance after film formation are known.

The methods (a) to (d) above each have the following drawbacks and are not preferred. That is, in the dry method (a), it is difficult to precisely control the evaporation conditions of the solvent. In the wet method (b), it is easy to control the film forming conditions, but it requires distillation and fractionation to remove the good solvent mixed into the poor solvent during the coagulation process and regenerate the poor solvent.
The cost is also high. In the stretching method (c), a stretching force is applied to the membrane in order to obtain micropores, so there is a risk that the membrane performance will change if an external force such as heat is applied. Also,(
The charged track etching method (d) requires expensive equipment and the process is complicated.

On the other hand, according to the solvent extraction method (e), the film forming process is simple, so a porous film can be produced at low cost.

In the production of porous membranes by the solvent extraction method, which is the problem to be solved by the invention (e), conventionally,
Inorganic salts such as sodium chloride, urea (Japanese Unexamined Patent Publication No. 63-46239), and the like have been used as elutable substances. However, since inorganic salts have a strong corrosive effect, there has been a problem in that they cause corrosion of the crusher, mixer, and elution tank that pulverize the inorganic salts. Furthermore, although urea is not corrosive, its particles have a wide particle size distribution, so the micropores of the resulting porous membrane were not uniform. Furthermore, it was also difficult to completely elute leachable substances mixed into the resin.

Means for Solving the Problems The present inventor has conducted extensive research in view of the problems of the above-mentioned prior art. As a result, in the solvent extraction method (e) above,
The present invention was completed based on the discovery that when calcium carbonate is used as the eluable substance, the calcium carbonate mixed in the resin can be completely removed, and the pore diameter, pore number, and pore distribution can be freely controlled. did.

That is, in the present invention, a resin solution in which calcium carbonate particles are blended and dispersed, or a mixed solution of a resin and a reactive liquid monomer, is applied or cast onto a substrate, and the solvent is evaporated or hardened to form a calcium carbonate-containing solution. The present invention relates to a method for producing a porous membrane, which comprises forming a resin membrane and then eluting and removing calcium carbonate from the membrane.

The method of the present invention includes the following steps (a) to (d).

(a) Step In the method of the present invention, first a resin solution or a mixed solution of a resin and a reactive liquid monomer is prepared.

The resin solution includes, for example, a thermoplastic resin solution, a thermosetting resin prepolymer solution, and the like.

The mixed solution of a resin and a reactive liquid monomer includes, for example, a mixed solution of a thermosetting resin prepolymer and a reactive liquid monomer.

The thermoplastic resin, thermosetting resin prepolymer (hereinafter, unless otherwise specified, these are collectively referred to as resins) and reactive liquid monomers used in the resin solution are not particularly limited, and may be used depending on the purpose of the porous membrane to be obtained. Depending on the situation, it can be used by appropriately selecting from known ones. Specifically, examples of thermoplastic resins include cellulose acetate, polyethersulfone, polysulfone, polyester, polyvinyl chloride, nitrocellulose, polyvinyl alcohol, polystyrene, polyvinyl acetate, and ABS resin. Examples of the thermosetting resin prepolymer include phenol resin, epoxy resin, unsaturated polyester, and polyurethane resin. Further, examples of the reactive liquid monomer include styrene, methyl methacrylate, diallyl phthalate, and the like.

The solvent for dissolving the resin is not particularly limited and can be appropriately selected from known solvents. Specific examples include acetone, methyl ethyl ketone, benzene, thinner, and water. Considering the dissolution stability of the resin, the evaporability of the solvent, the dispersion stability of the calcium carbonate particles to be added later, etc., two or more types of solvents may be used in combination.

The amount of resin contained in the resin solution or the mixed solution of resin and reactive liquid monomer is not particularly limited, and may be selected as appropriate depending on the intended use of the porous membrane, but usually 15 to It may be about 50% by weight.

The resin solution may contain known additives used in this field. Specifically, examples include dispersants, thickeners, film-forming aids, and plasticizers (for example, DOP) for measuring the dispersion stability of the resin.

DBP, epoxy dioctyl hexahydrophthalate, etc.), curing catalysts for thermosetting resin prepolymers (for example, methyl ethyl ketone peroxide, cumene hydroperoxide, benzoyl peroxide, etc.), and crosslinking agents. Furthermore, if necessary, pigment,
A coloring agent such as a dye may be included.

Step (b) Next, calcium carbonate is added to the resin solution or the mixture of the resin and the reactive monomer and uniformly dispersed. Compounding and dispersion are carried out according to known methods.

Calcium carbonate is not particularly limited, and both natural and synthetic calcium carbonates can be used. Among them, calcium carbonate produced by the precipitation method (precipitated calcium carbonate)
and surface-modified products thereof are particularly preferred. Examples of precipitated calcium carbonate include precipitated calcium carbonate produced by known precipitation methods such as carbonation method and soluble chlorination method. Specific examples include calcite, aragonite, and vaterite crystalline precipitated calcium carbonate. In addition, surface-modified products include, for example, precipitated calcium carbonate that has been surface-modified with one or more types of organic and/or inorganic substances, and calcium carbonate produced by the precipitation method without going through a drying process. Examples include precipitated calcium carbonate whose surface is solvent-substituted with the organic solvent used to dissolve the resin.

In the present invention, commercially available calcium carbonate may be used.

Specifically, for example, PC1 White Glossy CC1 White Glossy CC-
R1 Hakuenhana 01 Hakuenhana PZ, Homocal DSBril11
Examples include those commercially available under trade names such as ant-15 (hereinafter referred to as Shiroishi Kogyo Co., Ltd.).

The amount of calcium carbonate added to the resin solution is not particularly limited and may be selected appropriately depending on the intended use of the porous membrane, but it is usually determined by the resin solid content of the resin solution or the resin and reactive liquid monomer. 50 to 100 parts by weight of the mixed solution of
The amount is preferably about 200 parts by weight. The particle size of calcium carbonate is also not particularly limited, and may be selected appropriately depending on the intended use of the porous membrane, but is usually 0.02 to 20 μm.
It is best to set it to about m.

Calcium carbonate can be used alone or in combination of two or more.

(c) Step The calcium carbonate-containing resin solution obtained in step (b) above is applied or cast onto a substrate, and the solvent is evaporated or removed, or in the case of thermosetting resins, by proceeding with a curing reaction, A calcium carbonate-containing resin film is prepared. The substrate is not particularly limited as long as it does not adhere to the resin.

(d) Step A porous membrane is obtained by removing calcium carbonate from the calcium carbonate-containing resin membrane obtained in the above step (C).

As a method for removing calcium carbonate from the resin film,
For example, a method may be used in which the resin film is treated with an acid solution or the like. The treatment with an acid solution may be performed, for example, by immersing the resin film in the acid solution for about 1 to 10 hours.

The acid is not particularly limited, and examples include mineral acids such as hydrochloric acid, phosphoric acid, and sulfuric acid, and organic acids such as acetic acid and acrylic acid. Further, the concentration of the acid solution is not particularly limited, but it may normally be about 5 to 20% by weight.

Effects of the Invention According to the present invention, the following excellent effects can be achieved by using calcium carbonate as a leaching substance.

(1) Gas generated by the reaction of calcium carbonate and acid solution (
carbon dioxide) ensures a path for the acid solution to penetrate inside the resin membrane. Therefore, the precipitated calcium carbonate mixed into the resin film can be completely eluted.

(2) As calcium carbonate, it is possible to obtain one whose particle size and particle size distribution are more highly controlled than those of common salt, urea, and the like. Therefore, the method of the present invention that uses calcium carbonate has a lower pore diameter than the conventional method that uses common salt, urea, etc.
Pore number and pore distribution can be freely controlled.

(3) By using various calcium carbonates in combination, various porous membranes with different pore structures can be manufactured.

(4) The porous membrane obtained by the method of the present invention has higher uniformity of pore diameter than that obtained by the conventional method, and has excellent performance as a precision offshore material.

In addition, the pores formed in the film have a structure in which calcium carbonate particles are connected three-dimensionally, similar to the structure of connected ink bottles. Since such an ink bottle structure functions as a reservoir, it is also useful as a sustained release material for perfumes and the like.

(5) The porous membrane obtained by the method of the present invention can be used as a breathable waterproof membrane as it is or as a composite membrane in combination with a base material for clothing, waterproof covers, sanitary products such as disposable diapers, coats, etc. It is.

EXAMPLES Examples and comparative examples are given below to make the present invention even clearer.

Example 1 20 parts by weight of a thermoplastic polyester resin [Vylon 200, manufactured by Toyobo Co., Ltd.] was mixed with toluene/methyl ethyl ketone (=1
/1) Dissolved in 80 parts by weight to obtain a 20 w/w% resin solution. To this resin solution, precipitated calcium carbonate powder surface-modified with resin acid [Homocal D1 average particle diameter 0.0
40 parts by weight of 7 μm 1 (manufactured by Shiraishi Kogyo ■) were mixed, and calcium carbonate powder was further dispersed using Peyton conditioner. Next, this calcium carbonate-containing resin solution was applied onto the Tetron sheet using a film applicator to a dry film thickness of 20 μm, and dried at room temperature to completely remove the solvent in the coating film, leaving a calcium carbonate-containing resin film. Obtained. When this resin film was immersed in 18% hydrochloric acid for 2 hours, the calcium carbonate in the resin film was completely eluted. Thereafter, it was washed with water and dried to obtain a porous membrane.

The obtained porous membrane had a thickness of 20 μm and a porosity of 48.9%.
Met. As a result of pore size distribution measurement by mercury porosimetry, the distribution was mostly concentrated in the range of 0.05 to 0.08 μm, and the average pore size was 0.06 μm. When a non-film-forming polystyrene emulsion (concentration 0.005%) having a diameter of 0.20 μm was passed through this porous membrane, the P liquid was transparent and no turbidity due to emulsion particles was observed.

Comparative Example 1 A urea powder-containing paint was prepared in the same manner as in Example 1, except that a 40-layer plate of finely powdered urea with a particle size of 10 to 40 μm was used in place of the resin acid surface-modified precipitated calcium carbonate of Example 1. was prepared, coated and dried to obtain a resin film containing urea powder. This was immersed in warm water for 2 hours. The elution and elution of urea was insufficient.

Moreover, as a result of observing the obtained porous membrane with a scanning electron microscope, the pore diameters were widely distributed, ranging from 8 to 35 μm, and were not uniform.

Example 2 Thermosetting unsaturated polyester resin [Evolac G-15
2. To a mixed solution of 25 parts by weight of Nippon Shokubai Kagaku Kogyo Co., Ltd. and 75 parts by weight of styrene monomer [Wako Pure Chemical Industries, Ltd.], precipitated calcium carbonate powder surface-modified with resin acid [Homocal D1 average particle size 0] was added. .07μm, Shiroishi Industrial Co., Ltd.] 100
Parts by weight and 0.5 parts of cobalt naphthenate (polymerization accelerator) were mixed, and calcium carbonate powder was dispersed using a paint conditioner. Furthermore, 1 part by weight of methyl ethyl ketone peroxide (polymerization initiator) was added to this calcium carbonate-containing resin solution, mixed well, and applied onto a polyester sheet using a film applicator to a dry film thickness of 30 μm. A calcium carbonate-containing resin film was obtained. When this resin film was immersed in 18% hydrochloric acid for 2 hours, the calcium carbonate in the resin film was completely eluted. Thereafter, it was washed with water and dried to obtain a porous membrane.

The obtained porous membrane had a thickness of 30 μm and a porosity of 28.5%.
Met. As a result of pore size distribution measurement by mercury porosimetry, the distribution was mostly concentrated in the range of 0.05 to 0.08 μm, and the average pore size was 0.06 μm. When a non-film-forming polystyrene emulsion (concentration 0.005%) having a diameter of 0.20 μm was filtered through this porous membrane, the liquid was transparent and no turbidity due to emulsion particles was observed.

Comparative Example 2 A salt powder-containing paint was prepared in the same manner as in Example 2, except that 100 weight and full weight of finely powdered common salt with a particle size of 10 to 40 μm was used in place of the resin acid surface-modified precipitated calcium carbonate of Example 2. was prepared, and further coated and dried to obtain a salt powder-containing resin film. This was immersed in warm water for 2 hours. Elution of salt was insufficient.

Moreover, as a result of observing the obtained porous membrane with a scanning electron microscope, the pore diameters were widely distributed, ranging from 7 to 33 μm, and were not uniform.

Table 1 shows the performance of the porous membranes obtained in the above Examples and Comparative Examples.

Examples 3 and 4 A thermoplastic polyester resin (Toyobo ■, Vylon 200) was used as the resin, the particle size of precipitated calcium carbonate mixed and dispersed in the resin was changed, and the method of Example 1 was applied to a Teflon sheet. After drying, the resulting resin membrane was immersed in hydrochloric acid to obtain a porous membrane.

Table 2 shows the performance of the porous membrane obtained in the above example.

Claims (3)

[Claims] (1) A resin solution in which calcium carbonate particles are blended and dispersed;
Alternatively, a mixture of a resin and a reactive liquid monomer is applied or cast onto a substrate, the solvent is evaporated or cured to form a calcium carbonate-containing resin film, and then the calcium carbonate in the film is eluted and removed. A method for producing a porous membrane, characterized by: (2) The method according to claim 1, wherein the calcium carbonate particles are calcium carbonate with an average particle diameter of 0.02 to 20 μm produced by a precipitation method or surface-modified products thereof. (3) The method according to claim (1), wherein 50 to 200 parts by weight of precipitated calcium carbonate is mixed with 100 parts by weight of the resin content in the resin solution or the mixed solution of the resin and the reactive liquid monomer.