JP2001302839A - Microporous body and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing microporous bodies in which a variety of thermoplastic resins can be used and water having little environmental loading, can be used for extracting the foaming-agent from the bodies, and provide microporous bodies having a fine three-dimensionally communicating foam structure produced by this method. SOLUTION: As the foaming material that is soluble in water and to be admixed to a thermoplastic resin, a substance that is thermally stable at the temperature at which the thermoplastic resin melts thermally, is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microporous body and a method for producing the same, and more particularly, to a microporous body having a three-dimensional open-cell structure obtained by water extraction from various thermoplastic resins, and The present invention relates to a method for producing a microporous body.

[0002] In the case of producing a porous body having air bubbles in a so-called three-dimensionally communicating state, a foaming method in which a foaming material is mixed into a main material and bubbles are formed by a gas such as nitrogen generated from the foaming material, An extraction method in which a bubble forming material is mixed and dispersed in a main material in advance and then the bubble forming material is removed to form bubbles is generally employed. In the case of the foaming method, while there is an advantage that various main materials can be used, it is difficult to control the uniformity of the generated bubble diameter, and it is difficult to form bubbles having a small diameter of several tens of μm. On the other hand, in the case of the extraction method, the diameter and the like of the formed bubble depend on the type of the bubble material to be used. Therefore, there is an advantage that the above-mentioned uniformity and size can be arbitrarily controlled.

The above-mentioned extraction method is roughly classified into two methods, a wet method and a dry method, and each method is roughly as follows. Wet method: After dissolving the main material in a good solvent, mixing and kneading the foam-forming material into the same and uniformly dispersing it, obtain a main material molded into a predetermined shape, and then use a poor solvent for the main material. And dissolving and removing only the bubble forming agent using a solvent capable of dissolving the bubble forming material. Dry method: After heating the main material to make it dissolved, and mixing and kneading the air-forming material with it to uniformly disperse it, obtain a main material formed into a predetermined shape, and then use a poor solvent for this main material. And dissolving and removing only the bubble forming agent using a solvent capable of dissolving the bubble forming material.

[0004]

In the above-mentioned wet method, the solvent used for the main material includes a good solvent and a poor solvent. The condition is that the main material can be dissolved in a good solvent at around normal temperature. However, since the type is usually limited, the wet method cannot be used for thermoplastic resins such as olefins. For example, a well-known TPU (thermoplastic polyurethane) is used as a main material, and this is dissolved in DMF (N, N-dimethylformamide) as a good solvent to produce a viscous body. After mixing and kneading the foam forming agent into a predetermined shape, the DMF and the foam forming agent are dissolved and removed using a poor solvent for the TPU. In this case, the main material that can be used is the T
In addition to being limited to one kind of PU, the working environment during the kneading process of dissolving this main raw material is deteriorated by the use of a solvent, and it is regulated by TRTR (Law on the Transfer and Registration of Chemical Substances) in a poor solvent. Said DM
Difficulties such as elution of F are also pointed out.

[0005] On the other hand, in the case of the dry method, the main material only needs to be melted at a predetermined temperature by heating, and the raw material used is not limited. In addition, since the main raw material is dissolved by heating, it is possible to avoid a problem that the working environment is deteriorated due to the use of various solvents. However, in the case of the bubble forming material mixed and kneaded in the main material, acetone, alcohol, an aromatic solvent, or another organic solvent is used for extraction and removal. For this reason, in the extraction and removal stage, the working environment becomes inferior as in the case of the mixing / kneading step in the above-mentioned wet method, and further, there are serious drawbacks such as a problem with waste.

In this regard, the applicant has disclosed in Japanese Patent Laid-Open No. 11-16 / 1999.
As described in the patent application No. 6071, by using a water-soluble organic compound such as urea as a foam-forming material, the extraction solvent used so far can be changed from various organic solvents to water, and finely divided. A technique for obtaining a microporous body having a three-dimensional communicating cell structure has already been proposed.

However, in the technology disclosed in the above-mentioned patent application, since a thermally unstable organic compound such as urea is used as a bubble forming material, the main material is melted by heat during kneading. It is difficult to apply a sufficient temperature to the water.
For this reason, for example, when urea is used as the bubble forming material, there is a disadvantage that the main material that can be used is limited to those that are thermally melted at 130 ° C. or lower.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems inherent in the conventional microporous material and the method for producing the same, and has been proposed to suitably solve the problem. It is an object of the present invention to provide a method for producing a microporous body which is capable of using water with a low environmental load when extracting a cell forming material, and a microporous body having a fine three-dimensional communicating cell structure produced by the method. And

[0009]

In order to overcome the above-mentioned problems and achieve the intended object, the microporous body according to the present invention comprises at least one kind of thermoplastic resin, and the thermoplastic resin is melted by heat. A water-soluble bubble-forming material, which is thermally stable at a temperature, and a water-soluble polymer compound acting as a lubricant, which are mixed under heating to form a mixture of the water-soluble bubble-forming material and water. It is characterized in that a soluble polymer compound is extracted and removed with water to form a three-dimensional communicating cell structure.

[0010] Similarly, in order to overcome the above-mentioned problems and achieve the intended object, a method for producing a microporous body according to another invention of the present application comprises at least one kind of thermoplastic resin, A water-soluble bubble-forming material, which is thermally stable at a temperature to be heated, and a water-soluble polymer compound acting as a lubricant are mixed under heating, and the obtained mixture is formed into a predetermined shape, and then the obtained mixture is obtained. The obtained molded body is brought into contact with water, and the water-soluble bubble-forming material and the water-soluble polymer compound are extracted and removed from the molded body to obtain a microporous body having a three-dimensional communicating cell structure. .

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a microporous body having a three-dimensional communicating cell structure according to the present invention and a method for producing the same will be described below with reference to the accompanying drawings by way of preferred embodiments. The inventor of the present application kneads a thermoplastic resin, a water-soluble bubble-forming material, and a water-soluble polymer compound in an arbitrary mixing ratio under a heated state, forms the mixture into a predetermined shape, and immerses the formed body in water. By extracting and removing the water-soluble bubble-forming material and the water-soluble polymer compound, a porous body having a structure in which fine bubbles communicate three-dimensionally, a microporous material having a so-called three-dimensional communication bubble structure It was found that a body was obtained.

Examples of the thermoplastic resin include TPE (polyester, polyether, polyether polyester, styrene and polyamide) and olefin resins (PE (LD-PE, HD-PE, LL-PE, α- Any resin that can be melted by heating can be used, such as olefinated PE), PP and TPO), TPU, polyamide, polyimide or polyacetal.

As the water-soluble bubble-forming material, any material can be used as long as it is soluble in water and is thermally stable when the thermoplastic resin is melted by heat. For example, inorganic substances include NaC1, KCl, CaC1, and NH4.
Cl, NaNO ₃ , NaNO _{2 and the} like. As organic substances, TME (trimethylolethane), trimethylolpropane, trimethylolbutane, sucrose, soluble starch, sorbitol, glycine or each organic acid (malic acid, citric acid, glutamic acid, succinic acid, succinic acid)
And the like.

Further, as the water-soluble polymer compound,
Polyethylene glycol, polyethylene glycol diacrylate, polyethylene glycol dioleate, polyethylene glycol derivatives such as polyethylene glycol diacetate, and any other compound that dissolves in water and acts to lower the viscosity of the resin. Can also be used. Particularly, polyethylene glycol can be suitably used because it has a high melt flow and high water solubility. In addition, when an organic substance is selected as the water-soluble bubble forming material, an effect of promoting the extraction and removal of the water-soluble bubble forming material has been confirmed. Further, when molding is performed by an extrusion molding method, the molecular weight of the polyethylene glycol is 2,000 to 30,000, preferably 5,000.
~ 25,000, more preferably 15,000 ~ 25.0
It has been found that the range of 00 is suitable.

Further, for example, when an olefin resin is used as the thermoplastic resin and polyethylene glycol having low compatibility with the olefin resin is used as the water-soluble polymer compound, The particle size of the polyethylene glycol can be controlled by using the solubility. That is, the water-soluble polymer compound as a lubricant can be used as a water-soluble bubble forming material.

The mixing ratio of the thermoplastic resin to the water-soluble bubble-forming material and the water-soluble polymer compound (water-soluble substance) is preferably in the range of 10:90 to 40:60 by vol. is there. If the content of the thermoplastic resin is less than 10 vol%, the molded product itself will be separated when the water-soluble substance is extracted and removed. On the other hand, if the amount of the water-soluble substance exceeds 60 vol%, a sufficient number of bubbles will not be formed in the molded body.

The mixing ratio of the water-soluble bubble-forming material constituting the water-soluble substance and the water-soluble polymer compound is vo
A range of 45:55 to 95: 5 in 1% is preferred. When the water-soluble bubble-forming material is less than 45 vol%,
A three-dimensionally connected porous body structure cannot be obtained.
If the content exceeds vol%, the extraction ratio of the water-soluble substance is reduced, and a sufficient cell rate, that is, porosity cannot be obtained.

In particular, the mixing ratio of the thermoplastic resin is 12
The mixing ratio of the water-soluble bubble-forming material and the water-soluble polymer compound is preferably v-35 vol%.
It is preferable that the ol% is in the range of 65:35 to 88:12.

When the mixing ratio of the thermoplastic resin, the water-soluble bubble-forming material and the water-soluble polymer compound is set in the above-mentioned range, water is immersed in a molded product obtained by molding these mixtures. The water-soluble bubble forming material and the water-soluble polymer compound can be easily and sufficiently extracted and removed. That is, it is possible to obtain a microporous body having the three-dimensional communicating cell structure having the homogeneity and the strength by using the thermoplastic resin as a main material. Further, by setting the mixing ratio of the thermoplastic resin, the water-soluble bubble-forming material and the water-soluble polymer compound in the above-mentioned preferred range, the mixture has a bubble diameter of 500 μm or less and a bubble ratio of 75 μm or less. It is also possible to obtain a microporous body having a three-dimensional communicating cell structure of 以上 85 vol% or more. Furthermore, by further optimizing the mixing ratio of the three, a microporous body having a cell diameter of 30 μm or less can be produced.

In order to produce the microporous body according to the present invention, first, as shown in FIG. 1, a thermoplastic resin, a water-soluble bubble-forming material and a water-soluble polymer compound as raw materials are used by using predetermined equipment. Then, the mixture is kneaded and kneaded, and the obtained mixture is formed into a predetermined shape using an extruder or the like. The molded body thus obtained is immersed in water or warm water at a predetermined temperature to extract and remove the water-soluble bubble forming material and the water-soluble polymer compound, and to provide a large number of fine bubbles to provide a three-dimensional structure. A microporous body having a communicating cell structure is obtained.

For mixing and kneading the thermoplastic resin, the water-soluble bubble-forming material and the water-soluble polymer compound, a single-screw or twin-screw extruder, a kneader, a pressurized kneader, a co-kneader may be used. A Banbury mixer, a Henschel mixer, a rotor mixer or other kneaders are preferably used. For this kneading, no special device is required, and the kneading speed and the like are not limited. The temperature at the time of kneading is appropriately set according to the thermal melting point of the thermoplastic resin or the like to be used.In the present invention, the water-soluble bubble forming material is melted or sublimated at the thermal melting point of the thermoplastic resin. Because there is no, any temperature can be set. The kneading time depends on the physical properties of the various mixtures, but it is sufficient that the mixture is sufficiently mixed and kneaded, and usually about 30 to 40 minutes is sufficient. At this time, care must be taken because excessively long kneading may cause deterioration of the thermoplastic resin as the main material. The kneaded raw material can be formed into a required shape by extrusion, injection, press, roller, or blow, but in particular, extrusion with high mass productivity or injection molding capable of forming a complicated shape is preferable.

Each of the components is mixed and molded into a required shape. The water-soluble bubble-forming material and the water-soluble polymer compound are added to water as a solvent for a predetermined time (for example, 24 to 48).
(Depends on time, shape, thickness, etc. of the molded body). In addition, immersion at this time may be any method, but extraction and removal by immersion in water in which the whole mixture is brought into contact with water is preferable. The temperature of the water used at this time is not particularly limited and may be about room temperature. For efficient removal of the water-soluble substances, hot water of 15 to 60 ° C. is used. May be.

[0023]

[Experimental Examples] Experimental examples of the microporous body according to the present invention will be described below. This microporous body is prepared by mixing a preselected thermoplastic resin, a water-soluble bubble-forming material and a water-soluble polymer compound at a predetermined ratio, and using a general-purpose extruder or injection machine to obtain the resulting mixture. After forming into a required shape and processing the formed body to obtain a test piece having a width of 100 mm, a length of 200 mm, and a thickness of 2 mm, a 48-hour extraction treatment with water and a drying treatment with a hot air drier are performed. It is obtained. Formability, density (g / cm ³ ), tensile strength (kg
/ cm ² ), elongation (%), hardness (C), average cell diameter (μm) and melting point (° C.) were observed and measured, respectively.

(Experimental example 1) Mixing ratio of thermoplastic resin and water-soluble substance-Equipment used: Labo Plastomill extruder (manufactured by Toyo Seiki)-Raw materials used and mixing ratio: Styrene-based elastomer (commercial product) Name Clayton G Shell Chemical)
KCl silvin is used as a water-soluble bubble-forming material, and polyethylene glycol (trade name: PEG2000, manufactured by Sanyo Chemical Industries) is used as a water-soluble polymer compound. The thermoplastic resin: water-soluble substance ratio is 5 to 50 vol%: 50 to 50%.
A total of five types of test pieces were prepared while varying within 95%, and the extraction rate was calculated for each test piece. The mixing ratio of the water-soluble bubble forming material and the water-soluble polymer compound was 9: 1. -Results: shown in Table 1 below.

[0025]

The mixing ratio of the thermoplastic resin is 10 to 40 vol.
In the case of 1%, the extraction rate achieved 90% or more in each case, indicating that the mixed water-soluble bubble forming material and water-soluble polymer compound were almost completely extracted. That is, only the mixed thermoplastic resin remained, and a sponge-like porous body communicating in three dimensions was obtained. On the other hand, when the mixing ratio of the thermoplastic resin was 5%, the molded body was separated apart during the extraction of the water-soluble substance, and the shape could not be maintained as a porous body. When the mixing ratio of the thermoplastic resin is 5
In the case of 0%, the water-soluble substance was not sufficiently extracted, and as a result, the extraction rate was extremely low, on the order of 50%. From these facts, it was found that the mixing ratio of the thermoplastic resin and the water-soluble substance is preferably about 10:90 to 40:60.

(Experimental Example 2) When an olefin resin is used as a thermoplastic resin and molded by extrusion. Equipment used: Labo Plast Mill extruder (manufactured by Toyo Seiki). Raw material used: α-olefin as a thermoplastic resin. Polyethylene (trade name Tapmer A4090 manufactured by Mitsui Chemicals)
NaCl (trade name Uzushio Fine Particles M, manufactured by Naruto Salt Industry Co., Ltd.) was used as a water-soluble bubble-forming material, and polyethylene glycol (trade name PEG 20000, manufactured by Sanyo Chemical Industries) was used as a water-soluble polymer compound (1 and 2). As a comparative example,
The results in which the ratio of the water-soluble polymer compound was set to 0 and the results in which a general-purpose stearic acid was used were also described (ratio 1).
And ratio 2). The mixing ratio of the thermoplastic resin and the water-soluble substance was determined to be 30: 7 based on the results of Experimental Example 1.
0 was set. -Mixing ratio and results: shown in Table 2 below.

[0028]

(Experimental Example 3) When a styrene-based elastomer is used as a thermoplastic resin and molded by extrusion. Equipment used: Extruder Labo Plast Mill (manufactured by Toyo Seiki). Raw material used: a styrene-based elastomer as the thermoplastic resin.
(Claton G Shell Chemical Co., Ltd.), KCl silvin as a water-soluble bubble-forming material, and polyethylene glycol (trade name PEG 20,000, manufactured by Sanyo Chemical Industries) as a water-soluble polymer compound (3 and 4). As comparative examples, the results in which the ratio of the water-soluble polymer compound was set to 0 and the results in which general-purpose stearic acid was used were also described (ratio 3 and ratio 4). Further, the mixing ratio of the thermoplastic resin and the water-soluble substance was set to 3 based on the result of the experimental example 1.
0:70. -Mixing ratio and results: shown in Table 3 below.

[0030]

From the results of Experimental Examples 2 and 3, the following facts were confirmed. -According to the comparison of 1, 2, 3 and 4, the average cell diameter is smaller when the amount of polyethylene glycol (water-soluble polymer compound as a lubricant) is smaller, and conversely when the amount is larger, the average cell diameter is smaller. It became coarse. That is, the mixing amount of polyethylene glycol and the average cell diameter were in a proportional relationship. From the comparison of 1, 2, 3 and 4 with the ratios 1 and 3, only the thermoplastic resin and the water-soluble bubble-forming material showed that
It has been found that the flowability sufficient for extrusion cannot be maintained. That is, the addition of a water-soluble polymer compound as a lubricant is indispensable. From the comparison of 1, 2, 3 and 4 with the ratios 2 and 4, when stearic acid is used as a lubricant, the effect as a lubricant is exhibited, so that extrusion molding is possible, but polyethylene glycol is used. As a result, the solubility in water is low, and as a result, extraction is not completely performed and remains. That is, it was confirmed that physical properties such as tensile strength, elongation, and hardness deteriorated. -From these facts, it was found that the microporous body according to the present invention can suitably produce a porous body having low hardness and excellent tensile strength and elongation by extrusion. As the water-soluble polymer compound as a lubricant, polyethylene glycol is desirable.

(Experimental Example 4) When an olefin-based resin is used as a thermoplastic resin and molded by injection. Equipment used: TCD20-5AP (manufactured by Nissei Plastics Industries). Raw materials used: According to Experimental Example 2 described above (5, 6, ratio 5 and ratio 6). Mixing ratio and results: shown in Table 4 below.

[0033]

(Experimental Example 5) When a styrene-based elastomer is used as a thermoplastic resin and molded by injection. Equipment used: TCD20-5AP (manufactured by Nissei Plastics Industries). Raw materials used: According to Experimental Example 3 (7, 8, ratio 7 and ratio 8). -Mixing ratio and results: shown in Table 5 below.

[0035]

From the results of Experimental Examples 4 and 5, the following facts were confirmed.・ Comparing 5, 6, 7 and 8, the average cell diameter is smaller when the amount of polyethylene glycol (water-soluble polymer compound as a lubricant) is smaller, and when the amount is larger, the average cell diameter is smaller. It became coarse. That is, the mixing amount of polyethylene glycol and the average cell diameter were in a proportional relationship. From the comparison of 5, 6, 7 and 8 with the ratio 5 and the ratio 7, only the thermoplastic resin and the water-soluble bubble-forming material showed that
It has been found that the flowability sufficient for extrusion cannot be maintained. That is, the addition of a water-soluble polymer compound as a lubricant is indispensable. From the comparison of 5, 6, 7 and 8 with the ratio 6 and the ratio 8, when stearic acid is used as a lubricant, the effect as a lubricant is exhibited, so that extrusion molding is possible, but polyethylene glycol is used. As a result, the solubility in water is low, and as a result, extraction is not completely performed and remains. That is,
It was confirmed that physical properties such as tensile strength, elongation, and hardness were deteriorated. -From these, it turned out that the microporous body according to the invention of the present application can suitably produce a porous body having low hardness and excellent tensile strength and elongation ratio by injection molding.
As the water-soluble polymer compound as a lubricant, polyethylene glycol is desirable.

(Experimental Example 6) T was used as a water-soluble bubble forming material.
When ME (trimethylolethane) is used:-Equipment used: Labo Plastomill extruder (manufactured by Toyo Seiki Co., Ltd.)-Raw materials used: Same as in Experimental Example 2 except for the water-soluble bubble-forming material. TME (trade name: Trimethylolethane, manufactured by Mitsubishi Chemical Corporation) as a water-soluble bubble-forming material-Mixing ratio and results: shown in Table 6 below.

[0038]

Similar results were obtained even when the water-soluble bubble-forming material was replaced with an inorganic material and TME which could be used stably at high temperatures was used.

[0040]

As described above, according to the microporous body and the method for producing the same according to the present invention, a water-soluble inorganic substance or an organic substance having high thermal stability is used as a cell forming material. Since any thermoplastic resin can be used at any heat melting temperature, a microporous body having a three-dimensional open cell structure can be produced without being limited to the type of the thermoplastic resin. At this time, there is no problem even if a plurality of thermoplastic resins are mixed. Further, in both the mixing of the raw materials and the extraction of the water-soluble substance, an organic solvent such as acetone is not used, so that the working environment can be improved and the environmental load can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a process chart showing a preferred method for producing a microporous body of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 3/00 C08K 3/00 5/00 5/00 C08L 101/00 C08L 101/00 101/14 101 / 14 // B29K 101: 12 B29K 101: 12 509: 00 509: 00 (72) Inventor Shinsuke Yamada 380-5 Horiyamashita, Hadano-shi, Kanagawa F-term in INOAC Technical Research Institute Co., Ltd. 4F074 AA01 AA18 AA20 AA21 AA24 AA32. EF066 EG056 EN116 FD206

Claims (8)

[Claims] At least one thermoplastic resin, a water-soluble bubble-forming material that is thermally stable at a temperature at which the thermoplastic resin is melted, and a water-soluble polymer compound that acts as a lubricant. A water-soluble bubble-forming material and a water-soluble polymer compound are extracted and removed with water from a molded article of a mixture obtained by mixing under heating to obtain a three-dimensionally open cell structure. 2. The three-dimensionally communicating bubble has a diameter of 500.
The microporous body according to claim 1, wherein the bubble rate is 75 vol% or less when the diameter is not more than μm. 3. At least one kind of thermoplastic resin, a water-soluble bubble-forming material which is thermally stable at a temperature at which the thermoplastic resin is thermally melted, and a water-soluble polymer compound which acts as a lubricant. Are mixed under heating, and the obtained mixture is molded into a predetermined shape. Then, the obtained molded body is brought into contact with water, and the water-soluble bubble-forming material and the water-soluble polymer compound are molded from the molded body. A method for producing a microporous body, wherein a microporous body having a three-dimensional communicating cell structure is obtained by extraction and removal. 4. The method according to claim 3, wherein the water-soluble bubble forming material is an inorganic substance. 5. The method according to claim 3, wherein the water-soluble bubble forming material is trimethylolethane. 6. The method for producing a microporous body according to claim 3, wherein the water-soluble polymer compound is polyethylene glycol. 7. The mixing ratio of the thermoplastic resin to the water-soluble bubble-forming material and the water-soluble polymer compound is 1
The method for producing a microporous body according to any one of claims 3 to 6, wherein the method is between 0:90 and 40:60. 8. The water used to extract and remove the water-soluble bubble-forming material and the water-soluble polymer compound is at 15 to 60 ° C.
The method for producing a microporous body according to any one of claims 3 to 7, wherein