JPS62177039A - Production of porous membrane from thermosetting resin - Google Patents

Abstract

PURPOSE:To obtain a porous membrane suitable as a filter membrane, etc., standing steam washing, etc., by forming a porous membrane of a precondensate of thermosetting resin by a specific operation, drying and polymerizing under heating. CONSTITUTION:A precondensate of a thermosetting resin (e.g., polyaminobismaleimide, etc.,) is dissolved in a water-soluble organic solvent, the solution is impregnated into a heat-resistant fibrous material (e.g., glass fibers, carbon fibers, etc.,) or applied to a carrier (e.g., synthetic resin film, etc.,), immersed in water and the water-soluble organic solvent is extracted to form a porous membrane. This membrane is dried and polymerization is completed by heating.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing a porous membrane using a thermosetting resin, and more specifically, to a method for producing a porous membrane using a thermosetting resin. The present invention relates to a method for producing a porous membrane useful for filters, etc., which can sufficiently withstand steam cleaning, and which comprises forming a porous membrane, drying it, and then heating it to complete polymerization.

Prior Art and Problems to Be Solved Hitherto, porous polymer membranes have been widely used in filters and the like, and have been manufactured in a wide variety of ways from a wide variety of resins. However, although porous membranes made of thermosetting resins are partially manufactured using sintering methods, there is a lack of diversity in manufacturing methods, and they are used for applications that require heat resistance such as steam cleaning, or for applications that require radiation resistance such as polyimide resins. The current situation is that it does not fully meet the requirements for nuclear power-related offshore membranes.

As a result of intensive research in order to provide a method for manufacturing porous membranes that satisfies these requirements, the present inventor targeted a wide range of thermosetting resins, including polyimide resins, and developed initial polymers of these resins. A solution dissolved in a water-soluble organic solvent is applied onto a carrier (later peeled off) such as a heat-resistant fiber impregnated with glass cloth or a synthetic resin film, and then immersed in water to extract the water-soluble organic solvent. Then, a porous film of the above-mentioned initial polymer is formed, and the inventors discovered that by drying this and then completing the polymerization by heating, a desired porous film could be obtained, and the present invention was completed. .

That is, the present invention impregnates a heat-resistant fiber material with a solution of a thermosetting resin initial polymer dissolved in a water-soluble organic solvent or coats it on a carrier, and immerses it in water to extract the water-soluble organic solvent. The present invention provides a method for producing a porous membrane using a thermosetting resin, which comprises drying and then heating to complete polymerization.

Thermosetting resins targeted by the present invention include, for example, evaphenol resin (phenol formaldehyde resin), epoxy resin, furan resin (furfuryl alcohol resin),
DAP (diallyl phthalate) resin, polyimide resin (
Examples include triazine bismaleimide, polyamino bismaleimide, polyamideimide), polyurethane resins, and those having good heat resistance even at temperatures of 400° C. or higher, such as polyamino bismaleimide, are particularly preferred.

In the present invention, the initial polymer (
The so-called β-stage polycondensation stage) is used. As a specific example, in the case of polyamino bismaleimide, "Kelimide" manufactured by Nippon Polyimide Co., Ltd., which is commercially available as a material for preparing prepregs, can be mentioned. In the case of phenolic resins, examples include commercially available materials for compression molding, etc., which have already lost their water solubility and are soluble in highly polar organic solvents. In the case of polyurethane resin,
Examples include polyurethane prepolymers blended with blocked incyanate that dissociates and activates upon post-heating.

The initial polymer of the thermosetting resin (hereinafter sometimes referred to as a resin pot) is used in the form of a solution dissolved in a suitable water-soluble organic solvent. Specific examples of the water-soluble organic solvent are as follows. It is as follows. In the case of polyamino bismaleimide, N-methylpyrrolidone, dimethylformamide (DMF
) or mixtures thereof (the same applies to phenolic resins, epoxy resins, etc.). In the case of polyurethane resins DMF, tetrahydrofuran (THF) or mixtures thereof are suitable. In the case of furan resin, alcohols can be used alone or in combination depending on the resin composition. These water-soluble organic solvents are preferably highly purified anhydrous ones, but may contain water as long as they do not interfere with the solvent function. Therefore, it is also possible to separately use water in combination with the water-soluble organic solvent, and in this case, the rate of aggregation of the resin can be accelerated, which may lead to a reduction in process time. Note that not only a solvent that can be mixed with water in an arbitrary ratio, but also a solvent that is partially miscible (for example, acetone) may be used in combination.

In addition, the solution of such an initial polymer in the present invention includes:
It can also be used as a wax-like material obtained by proceeding polymerization to the β stage in the water-soluble organic solvent.

The concentration of the initial polymer solution may be selected so as to obtain a viscosity suitable for processing depending on the type and polymerization state of the initial polymer. In general, when the concentration is high, the porosity of the film pores formed in the extraction process described later decreases, and the pore size becomes finer. Conversely, when the concentration is low, the porosity increases (although the pore size becomes smaller). It tends to become coarser.In order to obtain a viscosity suitable for processing at low concentrations, the use of thickeners or silicon oxide powder may be effective in some cases.If the degree of resin polymerization is relatively high, high viscosity may be obtained even at low concentrations. In the case of polyamino bismaleimide, it exhibits a low viscosity immediately after dissolution, but it is observed that the viscosity increases over time.In addition, a surfactant should be added to the solution to prevent coarsening of the pore size. is also possible.

The heat-resistant fiber material used in the present invention must be resistant to being attacked by water-soluble organic solvents (and the water used in the extraction process described later), such as woven glass fibers, carbon fibers, polyaramid fibers, or metal fibers. Examples include non-woven materials, mat-like materials, and the like.

The carrier used in place of the above-mentioned heat-resistant fiber material does not need to be heat-resistant because it can be peeled off as described later. A film) or a release paper (preferably heat-resistant) may be employed.

The method for producing a porous membrane using a thermosetting resin according to the present invention includes:
It can be carried out as follows.

1) A heat-resistant fiber material is impregnated with the initial polymer solution adjusted to the above-mentioned predetermined concentration (or viscosity). Impregnation may be carried out according to a conventional method, for example, the fiber material is immersed in the system of the initial polymer solution, and if necessary, after removing air bubbles attached to the fiber material, the excess solution is squeezed out, and the impregnated fiber material is taken out from the system. .

In addition, in order to increase the adhesive force between the fiber material and the resin film, it is preferable to perform a primer treatment or a coupling treatment on the surface of the fiber material, if necessary.

Moreover, instead of such an impregnation method, the above-mentioned initial polymer solution is applied onto the carrier in an amount of usually 100 to 1000 f//d.

1) After the above impregnation or coating, the fiber material or carrier is immersed in water at room temperature or 0 to 70°C for 3 to 30 minutes. Here, the water-soluble organic solvent is extracted into water, whereby a porous film of agglomerated initial polymer is formed in the fiber material or on the carrier.

111) After performing the extraction treatment in this manner, it is subjected to a drying treatment according to a conventional method. In addition, when a porous film is formed on a carrier, the carrier is peeled off and removed before or after the drying. Drying is usually carried out at a temperature near the boiling point of water or organic solvent, but if organic solvent remains in the porous film, if the drying is carried out at a suddenly high temperature, the initial polymer will re-dissolve, causing the film to become porous. Since the structure may collapse, it is generally preferable to gradually increase the drying temperature by drying the water and then distilling off the organic solvent. It is also effective to dry in a vacuum dryer to remove the organic solvent.

lv) Finally, it is subjected to a heat treatment (usually carried out in an oven) to complete the polymerization. Heating conditions can be selected depending on the type of thermosetting resin; for polyamino bismaleimide, 200°C x 48 hours to 250°C x 24 hours; for epoxy resin, 150°C - 24 hours. Even in the case of this heat treatment, organic solvent remains. If the temperature is suddenly raised in a state where the
Rapid temperature rises should be avoided as this may result in insufficient curing. Also, when heat treating a large number of sheets at the same time,
A fluororesin-coated cloth or glass cloth is sandwiched between each layer, and heat treatment can be performed in a stacked state.

Incidentally, an inorganic filler, reinforcing short fibers, etc. may be blended into the resin solvent solution using the above method.

In this way, a heat-resistant porous membrane can be obtained with or without support on a fibrous material, and either of these can be used as a membrane for a wide range of applications.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 An initial polymer of polyamino bismaleimide (manufactured by Nippon Polyimide Co., Ltd., Kelimide 601) is dissolved in N-methylpyrrolidone at about 50°C to obtain a resin liquid having a concentration of 45% by weight. When this resin liquid was stored at room temperature, the viscosity gradually increased and reached about 3000 Cps after two weeks.

The resin liquid is put into a flat container, and the weight is about 200 ml.
Soak a 97d plain weave glass cloth. After squeezing the glass cloth in the resin liquid with a stick to remove any air bubbles attached to the glass cloth, hold one end of the glass cloth and squeeze it between the two sticks, and squeeze out the excess. While scraping off the resin liquid, remove the glass cloth from the resin liquid and immediately immerse it in water at room temperature. After 1 page of water immersion, the surface of the glass cloth turned white and resin agglomeration was observed, but it remained as it was for 5 days.
1 minute, then 5 minutes under running water under the tap for a total of 10 minutes. After soaking in water, gently wipe off the water from the surface and dry. First, it was placed in an oven at 95°C for 15 minutes to dry the moisture, and then at 120°C to distill off the residual solvent.
Heat drying is performed at 150° C. for 20 minutes and at 150° C. for 20 minutes to obtain a film-like product. After that, in order to complete the polymerization, a glass cloth was placed between each of the film-like materials, and the stack was placed in an oven for 2 hours.
Heat treatment is performed at 00°C for 48 hours. By straining in this way, a plate-like material having considerable hardness is obtained. The surface of this material was pale yellowish white, and although the pores themselves could not be discerned with the naked eye, cigarette smoke was observed to pass through, indicating that the material was porous.

Claims (1)

[Scope of Claims] 1. A heat-resistant fiber material is impregnated with a solution of a thermosetting resin initial polymer dissolved in a water-soluble organic solvent, or applied onto a carrier, and immersed in water to remove the water-soluble organic solvent. A method for producing a porous membrane using a thermosetting resin, which comprises extracting, drying, and then heating to complete polymerization. 2. The manufacturing method according to item 1 above, wherein the thermosetting resin is a phenol resin, an epoxy resin, a furan resin, a DAP resin, a polyimide resin, or a polyurethane resin. 3. The manufacturing method according to item 1 above, wherein the heat-resistant fiber material is a woven, nonwoven, or mat-like material of glass fiber, carbon fiber, polyaramid fiber, or metal fiber. 4. The manufacturing method according to item 1 above, wherein the carrier is a synthetic resin film or a release paper.