JPS5815502B2 - Gouseijiyushitakoutainoseizohouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a synthetic resin porous body, such as a porous film or a perforated plate, exhibiting high flux from a synthetic resin monoemulsion.

The manufacturing process for synthetic resin porous plates is to first obtain a powdered resin by emulsion polymerization, etc., form a powder layer with this resin, and then heat soften or heat press to fuse the powder particles appropriately. A method is known in which a perforated plate has a continuous pore structure from one surface to another surface, that is, a capillary-type pore structure.

However, the above method requires a drying process to obtain a powdered resin, and the pore structure of the perforated plate varies depending on the selected particle size, heat softening or heat compression conditions, etc., making it possible to obtain the desired flux with simple operations. The disadvantage is that it is difficult to obtain a perforated plate as shown.

Therefore, the present invention does not use dry powdered resin as in the conventional method described above, and therefore does not employ means such as heat softening or heat compression bonding, but directly from a synthetic resin emulsion obtained by emulsion polymerization. The object of the present invention is to provide a new and useful manufacturing method capable of obtaining a synthetic resin porous body exhibiting high flux.

That is, this invention takes advantage of the property of a synthetic resin emulsion to coagulate with an electrolyte, and also increases the volume of the emulsion particles by swelling the emulsion particles by absorbing a medium exhibiting an appropriate swelling property and replacing the medium with water. This method makes good use of shrinkage, and involves contacting a synthetic resin emulsion with an organic acid or an inorganic acid that coagulates the synthetic resin emulsion as an electrolyte, dissolved in a medium that exhibits appropriate swelling properties for the polymer of the emulsion particles. A porous coagulate is obtained by swelling the emulsion particles, a part of which is fused, and then replacing at least the L medium in the coagulate with water to form a porous coagulate by shrinking the volume of the fused emulsion particles. It is characterized by producing microscopic cracks in the porosity and drying without collapsing the pore structure.

The synthetic resin emulsion used in this invention can be easily produced by a conventionally known emulsion polymerization method.

Examples include polymerization catalysts such as ammonium persulfate and hydrogen peroxide, and alkyl sulfate esters, alkylbenzene sulfonic acid sorters, alkylaryl sulfonate sodium, polyethylene glycol alkyl ether,
A predetermined monomer is dispersed in an aqueous solution containing 0.05 to 10% of an emulsifier such as polyethylene glycol alkyl phenol ether, and polymerization is initiated by heating to usually 30 to 100°C, and the desired temperature is maintained at a predetermined temperature. The polymerization rate is

Thereafter, the emulsion obtained is filtered to remove some coagulated parts, and if necessary, a small amount of a surfactant is added as a storage stabilizer to obtain a synthetic resin emulsion.

The concentration of the polymer (solid content) in this emulsion is preferably about 10 to 60% by weight; if it is lower than about 10%, it is difficult to obtain a synthetic resin porous body exhibiting the desired flux; When the temperature increases, it becomes sensitive to mechanical shearing force, has poor storage stability, and tends to solidify early.

Since the particle size of the emulsion affects the quality, especially the pore diameter, of the porous synthetic resin, it is determined appropriately by changing the type and concentration of the emulsifier, the concentration of the initiator, the polymerization temperature, the stirring speed, etc.

By selecting the type of organic or inorganic acid and medium for coagulating the electrolyte, it is possible to obtain a porous body having any pore size of about 0.5 μm or less from an emulsion of usually 0.01 to 1 μm.

The monomer used in the production of this synthetic resin emulsion is preferably a polymer whose glass transition temperature is higher than room temperature, particularly preferably 50°C or higher, from the viewpoint of producing or using the porous body. Choose what you can give.

Specifically, for example, monomers such as methacrylic acid ester (the alkyl group in the ester residue has 1 to 4 carbon atoms), styrene, vinyl chloride, vinylidene chloride, ethylene, and other unsaturated copolymerizable monomers that can be used in combination with these monomers. Examples include monomers.

In materials such as natural rubber, which has a glass transition temperature below room temperature, particles fuse together during the process of replacing the medium in the porous coagulate with water and the subsequent drying process in the series of manufacturing processes of this invention. This results in a transparent or translucent synthetic resin body, making it difficult to obtain the desired porous body.

Moreover, when used, the porous material easily fuses together, and when the porous material is used, for example, as a filtration membrane, it tends to become compacted by water pressure, gas pressure, etc. during use, and its permeability tends to decrease.

However, especially when the above manufacturing process is carried out at a temperature lower than the glass transition temperature and the use temperature is lower than the above temperature, such problems are rare, and even polymers with a glass transition temperature below the above room temperature are effective. Available for

In this invention, in the above synthetic resin emulsion,
The synthetic resin emulsion is brought into contact with an electrolyte in which an organic or inorganic acid that coagulates is dissolved in a medium that has an appropriate swelling property for the polymer of the emulsion particles.

The organic acids or inorganic acids used here include a wide range of conventionally known electrolyte coagulants, such as formic acid, acetic acid, propionic acid, saturated or unsaturated monocarboxylic acids such as acrylic acid, or oxalic acid. Examples of inorganic acids include hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid.

Further, the medium having an appropriate degree of swelling for the polymer is one whose degree of swelling is in the range of about 101 to 50, preferably 2 to 10.

However, the above swelling degree is obtained by cutting 1.5 g of the polymer obtained by drying the synthetic resin emulsion into approximately 0.1 g pieces and placing them in an Erlenmeyer flask, adding 50 g of medium to this, and keeping it at room temperature for 5 hours. After standing, the contents were poured onto NO4 Whatman filter paper and filtered, and the weight of the swollen polymer on the filter paper was measured and expressed as the ratio of the weight of the swollen polymer to the weight of the original sampled polymer. It is.

Specific examples of media with such characteristics include acetone, methyl ethyl ketone, methanol, isopropanol, bukunol, dimethylformamide, and tetrahedron.
One or two organic polar media that dissolve at least 1% by weight in water, such as furan and ethylene glycol.
Examples include a mixture of more than one type of medium or a mixture of the above-mentioned medium and water. Organic polar media with a strong swelling effect are used by increasing the proportion of water used to adjust the degree of swelling of the medium as a whole to within the above range. The concentration of the organic acid or inorganic acid in these media is usually 0.01 to 3N, preferably 0.05 to 3N.
It is preferable to set it within the range of 0.5 regulation.

When trying to obtain a porous filtration membrane using a synthetic resin porous body, the contacting means is, for example, a roll coater after adding various thickeners as necessary to the synthetic resin emulsion.
It is cast onto a glass plate or other sheet-like part with a smooth or rough surface using a conventional coating method such as a knife coater, a spray coater, extrusion or dipping, and the organic acid or inorganic acid is immediately dissolved therein. Simply immerse it in a medium bath for a short time.

The medium absorbed into the emulsion in the above contacting step swells the emulsion particles and causes the particles in that part to equally fuse together.

The emulsion is then solidified under the action of an organic or inorganic acid in the above state, and eventually becomes a porous solidified product in which a portion of the emulsion particles are appropriately fused.

In this invention, it is necessary to appropriately fuse a part of the emulsion particles to form a porous coagulate, and this coagulate is made of a medium exhibiting the swelling degree and an organic acid or an inorganic acid having the concentration range mentioned above. This can be obtained by using .

On the other hand, if a medium that dissolves the emulsion polymer well is used, most of the emulsion particles will essentially fuse together, forming a transparent or translucent synthetic resin body with the desired porous structure. If the swelling property of the polymer is too large, the degree of fusion will be too large, and the volume of the emulsion particles will shrink too much in the subsequent process of replacing the absorbed medium with water, resulting in a solidified product. This also results in large cracks in the
Furthermore, if the swelling property is too low, the degree of fusion will be reduced and the result will be a mere porous solidified material, and the product obtained in the final drying step will be granulated or a discontinuous porous material.

Also, if the concentration of the organic acid or inorganic acid is too high, the synthetic resin emulsion will solidify rapidly and the swelling effect of the medium will not work properly, while if the concentration is too low, the solidification will be slow. There is a risk that the emulsion particles will be dispersed in the medium, making it difficult to obtain a porous coagulation in which some of the emulsion particles are properly fused.
As a result, it becomes difficult to manufacture the desired synthetic resin porous body.

In this invention, the medium contained in the above-mentioned porous coagulum is then replaced with water.

The replacement method may be carried out by immersion in water or spraying with water.

If the organic acid contained in the porous coagulum is replaced during this substitution,
Although the inorganic acid is also removed, the purpose of this step is to replace the medium with water, and the process is usually carried out until the medium in the coagulate reaches an equilibrium state.

The equilibrium state is considered to be when the content of the organic polar medium having a swelling effect contained in the immersion water or the water after spraying reaches a certain level.

When the medium is removed, the emulsion particles that were fused and swelled due to the replacement of the medium and water contract in volume, and as a result of this contraction, small cracks occur between the particles or inside the particles. However, in the end, the porous solidified product as a whole has a void structure consisting of a porous structure between particles and the above-mentioned micro-crack structure, resulting in a porous body exhibiting a higher flux than a mere porous structure between particles.

Moreover, since the above-mentioned minute cracks mainly occur between the fused particles which are limited to the appropriate ratio, there is no fear that the crack structure will become too large and deviate from the original role of the porous body.

Next, the porous solidified material having the above-mentioned pore structure is washed with water as necessary to almost completely remove the residual organic acid or inorganic acid, and then heated to room temperature or at a temperature lower than the glass transition temperature of the polymer to form the above-mentioned pore structure. Dry without disintegrating.

When a porous coagulated material is formed on a glass plate as described above for the purpose of obtaining a filtration membrane or the like, it may be peeled off from the glass plate and dried before or after washing with water.

The above peeling can be easily performed.

The synthetic resin porous body thus obtained is an opaque white porous body, and in the case of a thin film, it exhibits a high water permeation flux of about 0.1 ml/min.atm-cff1 or more.

As detailed above, the present invention does not use dry powdered resin as in the conventional method, but instead obtains a synthetic resin porous body exhibiting high flux directly from a synthetic resin emulsion obtained by emulsion polymerization. This method makes good use of the properties of a synthetic resin emulsion that coagulates with an electrolyte, the swelling of the emulsion particles by absorbing a medium that exhibits appropriate swelling properties, and the volumetric contraction of the emulsion particles by replacing the medium with water. be.

According to the method of the present invention, it is possible to easily obtain a synthetic resin porous body exhibiting a desired flux reliably with ease of operation, and it has many advantages as an industrial manufacturing method over the above-mentioned conventional methods.

The inventors have already found a method for obtaining a synthetic resin porous body having a high flux similar to that of the present invention by using a metal salt instead of the organic acid or inorganic acid in this invention. It has been confirmed that this method of the invention, which uses an acid, yields a thin film with a higher water permeability flux than the above method, and that the organic or inorganic acid is easy to remove from the porous coagulum. Since it can be almost completely washed away in the step of replacing the medium with water and the subsequent washing step, there is no fear that it will remain in the synthetic resin porous body after drying and adversely affect the quality of the porous body.

Utilizing its characteristics, the porous body of the present invention can be widely applied to materials such as filtration membranes and other films, and various porous plates that require air permeability or water permeability.

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

In addition, in the following, the term "person in charge" refers to the person in charge of "juuka".

Example 1 100 parts of a monomer mixture consisting of 55% methyl methacrylate and 45 parts ethyl acrylate was mixed with 0.5% ammonium persulfate and 5% emulsifier (Neugen EA160, manufactured by T-Gyo Seiyaku Co., Ltd.). Disperse in 150 parts of an aqueous solution, start polymerization at 70°C with stirring, and maintain at about 75°C for 5 hours to complete polymerization.

After completion of polymerization, some coagulates contained in the emulsion are removed by filtration to make the emulsion almost uniform in particle size.

The resulting synthetic resin emulsion has a nonvolatile solid content of 43
In this case, the average particle size of the particles was 0.05μ.

Spread this emulsion on a glass plate for about 1. After casting to a thickness of OOμ, it is immediately immersed for about 5 minutes in a medium (water: methyl ethyl ketone = 7:3, swelling degree about 10) made by dissolving a certain amount of acetic acid to a concentration of 0.3 normal. The particles are partially fused to form a porous solidified material.

This coagulated material is immersed in pure water and the absorbed medium is replaced with water until it reaches an equilibrium state.Then, the coagulated material is peeled off from the glass plate, washed repeatedly with water to almost completely remove the acetic acid, and then kept at room temperature. Alternatively, dry with warm air at a temperature below the glass transition temperature (50°C) of the polymer.

The synthetic resin porous body thus obtained has a pore diameter of about 0.1 μm or less and exhibits a water permeation flux of about 3 ml/min·atm-d.

Example 2 After adding about 1% sodium alginate to the synthetic resin emulsion according to Example 1, this was cast onto a polyester film to a thickness of about 80 μm.

Next, the particles are immediately immersed in a medium (water:acetone-8:2, swelling degree: approximately 7) for 3 minutes in which a predetermined amount of hydrochloric acid is dissolved to give a concentration of 0.2N, so that some of the particles are fused. A porous coagulum is formed.

The coagulated material is immersed in pure water and the absorbed medium is replaced with water until an equilibrium state is reached.

At this time, hydrochloric acid in the coagulated material is also removed.

After that, it is peeled off from the polyester film and dried at room temperature.

The synthetic resin porous body obtained in this way is approximately 0.04
It has a pore size of less than μ and exhibits a water permeation flux of approximately 3 m 17 min·atm·d.

Example 3 Methyl methacrylate 80, butyl acrylate 15f0
, and 1-joxyl ethyl acrylate 5 parts was emulsion polymerized in the same manner as in Example 1 to obtain a synthetic resin emulsion with an average grain size of 0.1 μ and a non-volatile solid content of 30 parts. .

This emulsion was applied to a thickness of about 150μ on a glass plate, and immediately immersed in a medium (methanol, swelling degree about 5) prepared by dissolving a certain amount of oxalic acid to a 0.3 normal concentration for about 5 minutes. The emulsion particles are immersed to form a porous solidified product in which some of the emulsion particles are fused.

Water is sprayed onto the coagulated material to replace methanol in the coagulated material with water until an equilibrium state is reached, and at the same time, oxalic acid is also removed.

Finally, the coagulated material is peeled off from the glass plate and dried at room temperature to form a porous synthetic resin body.

The pore diameter of the resulting synthetic resin porous body was 0.02 μ, and the water permeation flux was approximately 2 m 11 min·atm-ffl.

Claims (1)

[Claims] 1. A synthetic resin emulsion is brought into contact with an organic acid or inorganic acid that coagulates the synthetic resin emulsion as an electrolyte, dissolved in a medium that exhibits an appropriate swelling property for the polymer of the emulsion particles, and the swelling of the emulsion particles causes the swelling of the emulsion particles. a porous coagulate in which parts are fused together, and then replacing at least the medium in the coagulate with water to cause minute cracks in the porous coagulate due to volumetric contraction of the fused emulsion particles; A method for producing a porous synthetic resin material exhibiting a high flux from an emulsion, which is characterized by drying without disintegrating the void structure.