JPS5815503B2 - 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 porous plate.

The method for producing a synthetic resin perforated plate is to obtain a powdered resin in advance 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 of forming a perforated plate having a continuous pore structure from one surface to another surface, that is, a capillary-type pore structure, is known.

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

Another object of the present invention is to provide a synthetic resin porous body that exhibits high flux and has excellent strength.

That is, this invention takes advantage of the property that a synthetic resin emulsion undergoes electrolyte coagulation with a metal salt, and also creates an emulsion by swelling the emulsion particles by absorbing a medium exhibiting an appropriate swelling property and replacing the medium with water. Taking advantage of the volumetric shrinkage of particles, furthermore, in synthetic resin emulsions that have acidic groups such as carboxyl groups and sulfonic groups in their polymers, the polymers can be easily ionically crosslinked by metal salts for electrolyte coagulation. In this method, a metal salt that coagulates the synthetic resin emulsion as an electrolyte is dissolved in a medium that exhibits an appropriate swelling property for the polymer of the emulsion particles and is brought into contact with the synthetic resin emulsion. A part of the solidified material is fused by swelling to form a porous solidified material, and then at least the above-mentioned medium in this solidified material is replaced with water, thereby causing minute cracks in the porous solidified material due to volumetric shrinkage of the fused emulsion particles. The above synthetic resin emulsion contains acidic groups in its polymer, and the acidic groups are removed during the contact step with the metal salt. is reacted with a metal salt to generate ionic crosslinking bonds that crosslink the polymer in the porous coagulated material.

The synthetic resin emulsion used in this invention must contain an acidic group in the polymer, and this acidic group reacts with the metal salt for electrolyte coagulation to ionically crosslink the polymer and achieve the desired purpose. Improves the strength of synthetic resin porous bodies.

This type of emulsion can be easily produced, for example, by emulsion polymerization of the main monomer and the monomer having an acidic group.

The main monomer used here is preferably a polymer obtained by copolymerizing with a monomer having an acidic group for the production or use of the porous body, and the glass transition temperature of the polymer is preferably higher than room temperature, particularly Preferably, one is selected that can provide a polymer at a temperature of 50°C or higher.

Specifically, for example, an ester of acrylic acid or methacrylic acid (the number of carbon atoms in the thylkyl group in the ester residue is 1 to 4)
, styrene, vinyl chloride, vinylidene chloride, ethylene, and other unsaturated monomers that can be copolymerized with these monomers.

For materials that have a glass transition temperature below room temperature, such as polyisobutylene, the process of this invention involves replacing the medium in the porous coagulum with water, followed by drying, during which the particles fuse together. As a result, it becomes 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

Furthermore, in this invention, since the polymer is ionically crosslinked during the manufacturing process of the synthetic resin porous body, the glass transition temperature of the polymer can be raised slightly by this ionic crosslinking. By adjusting the density, it is possible to produce or use a desired porous body without causing the above-mentioned problems even if the glass transition temperature of the initial polymer is low.

Examples of monomers having acidic groups used in combination with the above main monomers include various copolymerizable monomers having carboxyl groups, sulfone groups, phosphonic groups, phosphine groups, phenolic hydroxyl groups, arsone groups, etc. as acidic groups. It broadly includes acrylic acid, methacrylic acid, icconic acid, crotonic acid, sulfopropyl meccrylate-1, sulfopropyl acrylate, 2-acrylamido-2-methylpropanesulfonic acid, vinylsulfonic acid, 1- Examples include methylvinylphosphonic acid, allylphosphonic acid, 2-phenylvinylphosphonic acid, allylphosphinic acid.

These acidic group-containing monomers are usually 0% relative to the main monomer.
．． It is preferable to use it in a proportion of 1 to 20 moles.

If too much is used, it will be difficult to carry out emulsion polymerization, and even if emulsion polymerization is successfully carried out, the resulting polymer will be extremely water-soluble or water-swellable, making it unsuitable for producing the desired porous body. do not have.

On the other hand, if the amount is too small, the crosslinking density due to ionic crosslinking will become low, making it impossible to improve the strength of the porous body.

Emulsion polymerization may be carried out by a conventionally known conventional method, for example, using 0.05 to 5% of a polymerization catalyst such as ammonium persulfate or hydrogen peroxide, an alkyl sulfate, an alkylbenzene sulfonic acid sorter, an alkylaryl sulfonate, or polyethylene. A predetermined monomer is dispersed in an aqueous solution containing 0.05 to 10% of an emulsifier such as glycol alkyl ether or polyethylene glycol alkyl phenol ether, and is heated to usually 30 to 100°C to initiate polymerization, and then heated to a predetermined temperature. Maintain the desired polymerization rate.

Thereafter, the resulting emulsion is filtered to remove some coagulated matter, 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 metal salt 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.

In this invention, in the above synthetic resin emulsion,
A metal salt that coagulates the synthetic resin emulsion with an electrolyte is dissolved in a medium that has an appropriate swelling property for the polymer of the emulsion particles and brought into contact with the emulsion.3 As the metal salt used here, conventionally known electrolyte coagulants are widely used. Typical examples include monovalent or divalent metal salts such as sodium acetate, zinc acetate, rutium nitrate, magnesium chloride, sodium sulfate, and zinc ethylenediaminetetraacetate.

Further, the medium having an appropriate degree of swelling for the polymer is one whose degree of swelling is in the range of about 1.01 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 properties include acetone, methyl ethyl ketone, methanol, impropateol, buknol, dimethylform, amide, tetrahydrofuran, ethylene glycol, etc., which are at least 1-4 soluble in water. Examples include one type or a mixture of two or more types of organic polar media, or a mixture of the above-mentioned media and water. For organic polar media with a strong swelling effect, the proportion of water used is increased to bring the degree of swelling of the entire medium to the above range. It is used with adjustment within.

The metal salt is brought into contact with the synthetic resin emulsion in a state in which it is dissolved in a concentration range from 0.5% by weight to the medium indicating its saturation solubility.

When trying to obtain a porous filtration membrane using a synthetic resin porous body, the contacting means is, for example, a synthetic resin emulsion, which has been added with various thickeners as necessary, and then rolled coke.
It is cast onto a glass plate or other sheet-like material with a smooth or rough surface by a conventional coating method such as knife coke, spray coater, extrusion or dipping, and the metal salt is immediately dissolved therein. The medium absorbed into the emulsion in the above-mentioned welding step swells the emulsion particles and causes some of the particles to fuse together.

The metal salt in the medium coagulates the emulsion in the above state, and reacts with the acidic groups contained in the polymer to cause the above-mentioned heavy metal salt to solidify mainly at the fused particle interface or inside the vicinity of the particle interface, where the concentration of metal salt is high. The aggregate is ionically crosslinked by metal ions.

As a result, the synthetic resin emulsion becomes a porous coagulated material in which a portion of the emulsion particles are appropriately fused and ionic crosslinking is mainly generated to crosslink the internal polymer at or near the fused particle interface.

In the present invention, it is necessary to form such a porous coagulated product, and this coagulated product can be obtained by using the medium exhibiting the swelling degree, the metal salt, and the synthetic resin emulsion having the acidic group. .

On the other hand, if a medium that dissolves the emulsion polymer well is used, most of the emulsion particles will essentially fuse together, making it impossible to obtain the desired porous body, and the polymer will have a large swelling property. If it is too thick, the degree of fusion will become too large, and in the subsequent step of replacing the absorbed medium with water, the volume of the emulsion particles will shrink too much, resulting in large cracks in the coagulated material, which is not beneficial from any point of view. A desired porous body cannot be obtained.

On the other hand, if the swelling property is too low, the degree of fusion will be low, resulting in a mere porous solidified material, and the product obtained in the final drying step will be granulated or a discontinuous porous material.

Furthermore, in a synthetic resin emulsion that does not have acidic groups, it is not possible to generate ionic crosslinking in the porous coagulated material, and it is not possible to improve the strength of the porous body by ionic crosslinking.

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.

During this substitution, metal salts that are not involved in ionic crosslinking contained in the porous coagulated material are also removed, but the purpose of this step is to replace the medium with water, and usually in the coagulated material. Continue until the medium 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 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.

On the other hand, the ionic crosslinks formed in the porous coagulate remain unaffected in this step.

Next, the porous solidified material having the above-mentioned pore structure is washed with water as necessary to remove residual metal salts that do not participate in ionic crosslinking, and then heated at room temperature or at a temperature lower than the glass transition temperature of the polymer after ionic crosslinking. Drys without disrupting the pore structure.

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,
In the case of a thin film, the water permeation flux is approximately 0.1ml.
/min.atm-ff1 or higher, indicating a high flux.

Furthermore, this porous body contains ionic crosslinking bonds that ionically crosslink the polymer, and these bonds significantly improve the strength of the porous body.

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.

Moreover, as the above synthetic resin emulsion, one containing acidic groups such as carboxyl groups and sulfone groups is selected.
The acidic group is reacted with a metal salt for electrolyte coagulation to incorporate ionic crosslinking bonds that crosslink the polymer into the desired synthetic resin porous body.

According to such an inventive method, a synthetic resin porous body that exhibits a desired flux reliably and is excellent in strength can be obtained with simple operation, and has many advantages as an industrial manufacturing method over the above-mentioned conventional methods.

The porous body thus obtained can be widely applied to materials such as filtration membranes and other films, and various porous plates requiring air permeability or water permeability by utilizing its properties.

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

Note that in the following, parts and parts refer to parts by weight, respectively.

Moreover, the pore diameter of the porous body was measured by mercury intrusion method.

Example 1 50 parts of methyl methacrylate, 45 parts of ethyl acrylate,
100 parts of a monomer mixture consisting of 5 parts of acrylic acid, 0.5% ammonium persulfate and an emulsifier (Inogen EA16)
0, manufactured by Dai-Kogyo Seiyaku Co., Ltd.) Aqueous solution 15 containing 5
0 parts, polymerization is started at 70° C. under stirring in a nitrogen stream, and is maintained at about 75° C. for 5 hours to complete the polymerization.

After the polymerization is completed, some coagulated substances contained in the emulsion are removed by filtration to make the emulsion particle size almost uniform.

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.

After casting this emulsion on a glass plate to a thickness of about 100 μm, it is immediately poured into a medium (water: methyl ethyl carbonate - 7:3, degree of swelling of about 10) made by dissolving 20% calcium acetate. By soaking for a minute, some of the particles are fused to form a porous solidified product in which ionic crosslinks that crosslink the polymer are formed.

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

Next, the coagulated material is peeled off from the glass plate, washed repeatedly with water to sufficiently remove metal salts that do not participate in ion crosslinking, and then left at room temperature or at the glass transition temperature (approximately 5
Dry with warm air at a temperature below 5°C.

The pore diameter, water permeation flux, and strength of the synthetic resin porous body thus obtained are shown in Table 1 below.

For reference, a synthetic resin emulsion produced without using 5 parts of acrylic acid in the monomer mixture according to Example 1 (however, the number of parts of the aqueous solution was 142.5 parts) was used in the same manner as above. Example 2 The property results of the synthetic resin porous body obtained in Example 1 are also listed in Table 1 as Reference Example 2. After adding 100 g of the synthetic resin emulsion according to Example 1 and 0.4 ml of 28% aqueous ammonia, this was applied to a polyester film. to a thickness of approximately 80μ.

Next, the particles are immediately immersed in a medium containing about 20% calcium chloride (water:acetone-8:2, swelling degree about 7) for 3 minutes to fuse some of the particles together, and A porous solidified material is formed with ionic crosslinking bonds that crosslink the polymer.

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, metal salts not involved in ionic crosslinking are also removed.

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

The characteristic values of the synthetic resin porous body thus obtained are shown in Table 2 below.

For reference, 10 g of the synthetic resin emulsion according to Reference Example 1 was thickened by adding 10 g of sodium alginate with a ratio of 10 to 100 g, and the characteristic results of the synthetic resin porous body obtained in the same manner as in Example 2 were used for reference. It is also listed in Table 2 as Example 2.

Example 3 80 parts of methyl methacrylate, 15 parts of butyl acrylate,
A monomer mixture consisting of 5 parts of sulfopropyl methacrylate was emulsion polymerized in the same manner as in Example 1, and the average particle size was 0.
A synthetic resin emulsion with a nonvolatile solid content of 30% was obtained using 11Z.

Using this emulsion, a synthetic resin porous body is obtained in exactly the same manner as in Example 2.

The characteristic values of this porous body are shown in Table 3 below.

For reference, a synthetic resin emulsion with the same average particle size and nonvolatile solid content as that of Example 3, which was produced without using 5 parts of sulfopropyl methacrylate in the monomer mixture according to Example 3 above, was used. The characteristic results of the synthetic resin porous body obtained in exactly the same manner as in Example 3 are also listed in Table 3 as Reference Example 3.

Example 4 60 parts of methyl methacrylate, 15 parts of acrylonitrile,
A monomer mixture consisting of 5 parts of hydroxyethyl acrylate, 15 parts of butyl acrylate, and 5 parts of 1-methylvinylphosphonic acid was emulsion polymerized in the same manner as in Example 1, and the average particle size was 0.05μ and the nonvolatile solid content was obtained. A 40% synthetic resin emulsion was obtained.

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) containing about 20% calcium nitrate for about 5 minutes to remove some of the emulsion particles. A porous coagulated material is obtained in which the polymers are fused and ionic crosslinking bonds are formed to crosslink the polymer.

The coagulum is sprayed with water to replace the methanol in the coagulum with water until an equilibrium state is reached, and at the same time also removes metal salts that are involved in ionic crosslinking.

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

The characteristic values of this synthetic resin porous body are shown in Table 4 below.

For reference, the average particle size and nonvolatile solid content of the monomer mixture according to Example 4 above, which were produced without using 5 parts of 1-methylvinylsulfonic acid, were the same as those according to Example 4 above. The property results of a synthetic resin porous body obtained in exactly the same manner as in Example 4 using a resin emulsion are also listed in Table 4 as Reference Example 4.

Example 5 A monomer mixture consisting of 50 parts of styrene, 20 parts of vinyl acetate, 15 parts of 2-ethylhexyl acrylate, and 15 parts of allyl phosphinic acid was emulsion polymerized in the same manner as in Example 1,
A synthetic resin emulsion with an average grain size of 0.05 μm and a nonvolatile solid content of 40 parts was obtained.

This emulsion was applied to a thickness of approximately 200μ on a glass plate, and immediately immersed in a medium prepared by dissolving 5% zinc ethylenediaminetetraacetate (methanol:water, -8:2, swelling degree: 2) for approximately 10 minutes. By dipping, a portion of the emulsion particles are fused to form a porous solidified product in which ionic crosslinking bonds that crosslink the polymer are formed.

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

Next, the coagulated material was peeled off from the glass plate and washed repeatedly with water.
After sufficiently removing metal salts that do not participate in ion crosslinking, the polymer is dried with warm air at a temperature below about 60° C., the glass transition temperature of the ionically crosslinked polymer.

Table 5 shows the pore diameter, water permeation flux, and strength of the synthetic resin porous body thus obtained.

For reference, - among the monomer mixtures according to Example 5 above, the average particle size and non-volatile solid content produced without using 15 parts of allyl phosphinic acid are the same as those according to Example 5 above. The characteristic results of a synthetic resin porous body obtained in exactly the same manner as in Example 5 using a resin emulsion are also listed in Table 5 as Reference Example 5.

As can be seen from Tables 1 to 5 above, according to the method of the present invention, a porous synthetic resin material having a water permeation flux of 1 ml/min/atrrrc77 or more can be obtained. It can be seen that the strength is far superior to that of the reference example, which uses a synthetic resin emulsion that does not contain acidic groups such as sulfone groups or sulfone groups.

Furthermore, as a result of infrared spectroscopic analysis of the porous bodies obtained by the method of this invention, sharp absorption was observed in all cases, indicating that the acidic groups were salt-formingly bonded with metal ions, and this bond was found to be strong. It was confirmed that this was significantly involved in the improvement.

Claims (1)

[Claims] 1 A synthetic resin emulsion is brought into contact with a metal salt 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,
The swelling of the emulsion particles results in a porous coagulation in which some of the particles are fused, and then at least the above-mentioned medium in the coagulated substance is replaced with water, whereby the volume of the fused emulsion particles shrinks to form a porous coagulation. The synthetic resin emulsion described above contains acidic groups in its polymer, and during the contact process with the metal salt, A synthetic resin porous body produced from a synthetic resin emulsion that exhibits excellent strength and high flux, characterized in that the acidic group is reacted with a metal salt to generate an ionic crosslinking bond that crosslinks the polymer in the porous coagulum. manufacturing method.