JP2008007534A - Porous molded article and half-sealed container composed of the same and method for producing the same molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an inexpensive and heat-resistant vent cap replacing an existing vent cap using a PTFE nonwoven fabric and corresponding to environmental problems. <P>SOLUTION: Pentaerythritol is melt-mixed with PBT and a third component and the mixture is extruded to form pellets and the pellets are used as a raw material and then molded into a vent cap-shaped material by injection molding and the vent cap-shaped material is immersed in water or warm water in order to extract a water-soluble component to produce a porous molded article. Since the molded article is obtained from a composition containing the third component, air permeation rate of the molded article after extraction with hot water is equivalent to that of the existing molded article. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a porous molded product for guaranteeing internal pressure and preventing water intrusion used in mobile machines, electronic devices, home appliances, and lighting devices, a semi-sealed container provided with a porous molded product, and a method for producing a porous molded product. About. More specifically, light emitters, electronic circuits, relay circuits, motors, and other driving parts are often sealed with porous molded products to prevent dust and water from entering, but when they are completely sealed, the inside changes in temperature. The air pressure change due to this is undesirable, so that air and water vapor are permeable to eliminate fluctuations in the internal pressure in the sealed container, and a vent plug having sealing properties against liquid water is arranged, that is, Semi-hermetic containers are common. The present invention relates to a porous molded product used for a vent plug or the like, a semi-sealed container provided with a porous molded product, and a method for producing a porous molded product.

  Vent plugs such as those described above are used in many parts that are not visible to the human eye but are in daily contact with humans. For example, an automobile headlamp is made of a large transparent resin molded product, in which a light bulb is fitted. When it emits light, it is close to 100 ° C, but when it is not lit, it is considerably below freezing in Hokkaido and mountainous areas in winter. When this headlamp is sealed, there is no trouble on the electrical circuit due to water collecting inside, but the pressure is increased during lighting and the pressure is reduced during the winter, and repeated thermal stress is applied to the resin structure. Eventually, it will be destroyed by thermal fatigue. A vent plug prevents this.

  Although this is an inconspicuous part, the role of the vent plug is great. At present, a non-woven fabric made of polytetrafluoroethylene resin (hereinafter referred to as “PTFE”) is used for such a vent plug as a vent portion. An injection molding made of ABS resin (hereinafter referred to as “ABS”), polycarbonate resin (hereinafter referred to as “PC”), polybutylene terephthalate resin (hereinafter referred to as “PBT”) or the like is provided in the structure of the vent plug. The product is used. A hole penetrating the inside and outside of the injection molded product is formed, and a non-woven fabric made of PTFE is bonded to the hole so as to close the hole. This nonwoven fabric allows air and water vapor to pass through but does not allow water droplets to pass through, because it uses the water repellency of PTFE. A vent plug made of a non-woven fabric made of PTFE does not have a problem in performance. However, if it is dared to say, adhesion failure or the like occurs when the non-woven fabric is stuck to the plug body at the time of manufacture.

  In general, PTFE is a resin that is difficult to bond, and the adhesive is improved, but the reliability of the bonding process is low, and 100% inspection is essential. Another problem is when a car is discarded. Since PTFE is not a thermoplastic resin, PTFE becomes insoluble when it is melted without removing the nonwoven fabric after the bulb is removed from the headlamp. In the extruder for recycling the molten resin, it is necessary to install parts to be filtered and separated by a net and periodically disassemble and take out the parts for cleaning. Moreover, although it is not exactly known, there is a problem that hydrogen fluoride generated by decomposition of the nonwoven fabric may accelerate the wear of the metal constituting the extruder. When a resin mixture containing PTFE as a fuel is burned without treatment, hydrogen fluoride is generated, which may damage the furnace and lead to an unexpected accident.

  Furthermore, it is unclear that it is the same type of halogen as chlorine and bromine that produce dioxins, but it gives anxiety. Even if the above-mentioned concern has occurred, it is considered to be within an allowable value in terms of the environmental load, so it is determined that this is not a matter that should be regarded as an environmental problem. However, there are points of concern from the automobile industry, etc., and there has never been a solution to the concern. The present inventors have earnestly researched and developed whether or not a ventilation structure that can be used as a substitute for the above-described vent plugs currently used can be obtained by a very simple means.

  The present invention is functionally equivalent to the current product, but on the other hand, the whole is a thermoplastic resin, and there is no process that impairs the reliability of adhesion, etc., environmental problems can be cleared, and the cost can be reduced. The target was high. The inventors of the present invention manufactured a compound of pentaerythritol and polypropylene resin (hereinafter referred to as “PP”), injection-molded the compound as a raw material, immersed the molded product in warm water, and dissolved in water in the molded product. We succeeded in producing a porous molded article with excellent gas permeability by eluting the components and drying them.

However, it was judged that the strength of the porous product was insufficient and it was insufficient for use as a substitute for the current vent plug. Therefore, PBT-based porous molded products that can be expected to have higher strength and heat resistance were expected. The present inventors paid attention to a method for producing a porous body using pentaerythritol (molecular formula: C ₅ H ₁₂ O ₄ ) that has already been developed. That is, in Patent Document 1, pentaerythritol and a thermoplastic resin are melted at a temperature equal to or higher than the melting point of pentaerythritol, this is used as a raw material for injection molding, and the molded product is immersed in some alcohol-soluble solvent to extract pentaerythritol, A method of making this a porous molded article is disclosed.

JP 2001-2825 A

  On the other hand, PBT has been adopted in automotive electrical components such as lamp sockets, fuse cases, and harness connectors, taking advantage of its high heat distortion temperature and high rigidity, electrical characteristics, mechanical characteristics, and the like. In addition, it is also used for mechanical parts such as seat belt components and gears. Therefore, the inventors of the present invention have thought to make a gas-permeable porous product having a PBT structure using the PBT that is often used. As a result, it is possible to realize the above-described environment-free load and to solve the reproduction process. In Patent Document 1 mentioned above, there is no description that a porous molded product was obtained from pentaerythritol and PBT. Therefore, considering a specific production method, the combination of pentaerythritol and PBT is expected to be difficult. There are many things to do.

  Before explaining this expectation, the chemical properties of pentaerythritol will be described. Commercial pentaerythritol usually contains around 10% dimer. This is because when pentaerythritol, which is a solid at room temperature, is heated, the dehydration and dimerization reaction occurs before the melting point is reached unless the temperature is raised at a very high speed and rapidly cooled. As long as it is mass-produced, it becomes a product containing a dimer by a high-temperature process in the manufacturing process. In short, commercially available pentaerythritol contains about 10% of a dimer and its melting point is around 190 ° C., but this dimer ratio is also an equilibrium value at 190 ° C.

  According to the chemical handbook and the like, the melting point of 100% pure pentaerythritol is about 250 ° C. However, for the reasons described above, 100% pure pentaerythritol cannot be obtained from the market. In addition, although it is not impossible for many chemists to use this commercial product as a raw material and purify it to 100%, it is meaningless in the present invention. This is because the dimer is also water-soluble, and even if these are contained in the molded product, they are similarly extracted with a solvent that dissolves pentaerythritol (for example, water, hot water, ethanol).

  Therefore, the pentaerythritol referred to in the present invention is rather made by using commercially available pentaerythritol as a raw material. Therefore, the substantial melting point is around 190 ° C., and importantly, when heated to 190 ° C. or higher, the dimer ratio at equilibrium exceeds 10%, and a new dehydration dimerization starts. When the present inventors charged a commercially available pentaerythritol into an autoclave and raised the temperature at a rate of about 2 ° C./min, melting was observed around 190 ° C., and the internal pressure rapidly increased at 225 to 240 ° C., It was found that a sudden generation of water vapor occurred. Therefore, when a compound is made from pentaerythritol as a raw material using an extruder, a hot roll, or the like, it is clear that a large amount of water vapor is generated when the operation is performed at about 230 ° C. or higher.

  As a result, it can be seen that the temperature range that can be used for mixing and melting a thermoplastic resin in pentaerythritol to be compounded is in the range of 190 to 230 ° C., and the handling should be performed smoothly. On that basis, problems expected when PBT is adopted as the thermoplastic resin will be described. One is that the melting point of PBT is as high as around 225 ° C. This temperature range is also a temperature at which new dehydration and dimerization of the commercially available pentaerythritol starts. In order to prevent dehydration and dimerization from hindering the preparation of the compound, there is no choice but to liquefy at a temperature not higher than 230 ° C., that is, not higher than the melting point of PBT. This was considered the first challenge.

  Assuming the case where the first difficulty can be removed, it is only that PBT dissolves in molten pentaerythritol. When the possibility was considered chemically, it was thought that PBT, that is, an ester, may be sufficient due to its inherently alcoholic nature. If PBT was dissolved in molten pentaerythritol as expected, two new difficulties were anticipated. One is that when an ester is allowed to coexist in a large amount of alcohol liquid at a high temperature of 200 ° C. or higher, an ester decomposition reaction occurs. In particular, in a polyester, a molecular bond is broken and a low molecular weight reduction reaction occurs.

  This low molecular weight reaction is inconvenient for the purpose of creating a high-strength porous body, and can be another difficulty. That is, the melt is highly likely to be uniform without a sea-island structure as viewed from the microscopic structure. When a melted and uniform melt is rapidly cooled and solidified, there is a high possibility that the microscopic structure will be solidified while being almost uniform. It was assumed that the extraction of uniform hot water was slow and the gas permeability of the porous material after extraction was inferior. This is because, according to the experience of the present inventors, in a molded product that gives a porous material with high gas permeability after hot water extraction, the microscopic structure of the molded product is basically pentaerythritol is sea and resin is island. It was because it became the sea-island structure. In short, even if the compound could be successfully compounded and formed, the porous material obtained by hot water extraction was expected to be inferior in gas permeation rate.

The present invention has been developed in the background as described above, and achieves the following object.
An object of the present invention is to provide a porous molded product that can be used for a vent plug or the like with little environmental load such as disposal after use, a semi-sealed container provided with a porous molded product, and a method for producing a porous molded product. provide.

  Another object of the present invention is to provide a porous molded article that can be molded by highly productive injection molding and can be used for a vent plug and the like, and a method for producing the same.

  The porous molded product of the present invention 1 is one or more selected from pentaerythritol 60 to 85 parts by weight, polybutylene terephthalate resin 15 to 40 parts by weight, and polyfunctional alcohol, polyethylene glycol, and polypropylene glycol that are liquid at room temperature. Of 0.25 to 3 parts by weight of this product, and by immersing this molded product in water, water-soluble components in the molded product are dissolved in the water and removed, thereby allowing gas to pass through the molded product. A porous material having properties is formed.

  The porous molded article of the present invention 2 is the porous molded article of the present invention 1, wherein the molded article immersed in the water is immersed in an aqueous emulsion of a tetrafluoroethylene polymer in order to improve water resistance. Thereafter, the molded article is dried, and a tetrafluoroethylene polymer is adhered to the surface of the porous body and the inner surface of the pores inside the porous body.

  The method for producing a porous molded article of the present invention 3 includes a pelletizing step in which a mixture containing pentaerythritol, polybutylene terephthalate resin, and a third component is melt-mixed at 200 to 235 ° C. and extruded into pellets, and injection molding It consists of an injection molding process for molding a molded product by injection molding and an extraction process for extracting the water-soluble component by immersing the molded product in water or hot water.

  The method for producing a porous molded article according to the present invention 4 comprises the dipping step of immersing in an aqueous emulsion of a tetrafluoroethylene polymer and drying after the extraction step in the method for producing a porous molded article according to the present invention 3. It is characterized by that.

  The semi-sealed container of the present invention 5 is a semi-sealed container using the porous molded product of the present invention 1 or 2 as a vent plug, and has a through-hole penetrating the porous molded product through the wall surface of the container. A fixing means for fixing the porous molded product to the wall surface in order to close the wall is provided.

  The semi-sealed container of the present invention 6 is the semi-sealed container of the present invention 5, wherein the fixing means is an internal screw formed on the inner peripheral surface of the through hole and a fixing screw screwed into the internal screw. And

  Details will be described below. The difficulty in obtaining a porous PBT molded article having a high gas permeation rate using pentaerythritol was as predicted by the present inventors as described above. That is, PBT was dissolved in liquid pentaerythritol at 200 ° C. or higher, and when the compatible material was placed at this temperature for a long time, PBT was alcoholic decomposed and the molecular weight rapidly decreased. Although the molecular weight reduction of PBT was suppressed by shortening the time from dissolving PBT in pentaerythritol to quenching, the gas permeation rate was low as expected. The present inventors have made trial and error and found that the addition of a specific third component is effective in overcoming this. Hereinafter, material adjustment and each process are demonstrated concretely.

[Pentaerythritol]
Commercially available products are not 100% pure and contain about 10% dimer, but can be used in the present invention as they are, and those containing about 10% dimer are themselves pentaerythritol in the following description. Called. This pentaerythritol has a melting point of about 190 ° C. These commercially available products are generally powders, and there are classified products showing an average particle size. However, the pentaerythritol used in the present invention has no effect on the particle size, and any product can be used.

[PBT]
The PBT used in the present invention may be a PBT alone and not including any other PBT, but a commercially available PBT containing glass fibers or inorganic fillers may be used in addition to the PBT. Although the shape of PBT used as a raw material can be used in pellets or powder, when actually making a compound, the way of handling is slightly different depending on the form.

[Preparation of mixture]
Stir the pentaerythritol powder, PBT pellet or powder, and the third component with a mixing stirrer such as a tumbler or Henschel mixer. The resulting loose mixture is the feedstock to the extruder. The mixing ratio is 0.25 to 3 parts by weight of one or more selected from pentaerythritol 60 to 85 parts by weight, PBT 15 to 40 parts by weight, and a liquid polyfunctional alcohol, polyethylene glycol, and polypropylene glycol. .

  Considering PBT as a reference, if the pentaerythritol is larger than the above ratio, the injection-molded product becomes brittle and the injection molding itself becomes difficult. For example, the product is likely to be chipped or broken at the time of mold release in the injection molding process, and it is difficult to discharge the runner at the time of injection molding. Further, when the content of pentaerythritol is smaller than the above ratio, the gas permeability of the final product is low.

  Examples of the liquid polyfunctional alcohol include ethylene glycol, diethylene glycol, propylene glycol, glycerin, and glycerin dimer. If the third component such as a liquid polyfunctional alcohol or polyethylene glycol or polypropylene glycol is larger than the above ratio, the mechanical properties in the final product are weakened. Conversely, if it is smaller than the above ratio, the gas permeability is remarkably lowered.

[Preparation of pellets]
The preparation of the pellets is a step of applying the loose mixture obtained in the previous step as a raw material to an extruder, cooling and cutting into pellets. When the extruder is a biaxial type, the raw material PBT is preferably a powder rather than a pellet. Further, it is preferable that the residence time in the extruder is short and the kneading is small. If pellets are used as raw materials, it is not impossible to achieve a balance, but it is a little difficult. The reason is that there is an increased possibility that the previously dissolved PBT is reduced in molecular weight while the pellet PBT is dissolved. However, even if some insoluble PBT remains in the extrudate as it is, there is little actual damage, so pellets cannot be used as a raw material, and there is a high probability that the stable production of practical products will be hindered.

  The cylinder temperature of the extruder is preferably set to 235 to 225 ° C. for any type of extruder, and the reason is as described above. What can be said from many experiments actually conducted by the present inventors is that it is easy to dissolve PBT in pentaerythritol, which is a high-temperature liquid, and that the simultaneous alcoholysis reaction of PBT is faster than expected. Two points. Therefore, it is preferable that the material passing time in the extruder is the shortest among the conditions under which the melt can be discharged from the nozzle, and the kneading may be less, i.e., the screw rotation speed is higher than the generally used conditions. A lower one is preferred. A model with a small L / D is also suitable as an extruder. It is preferable that the melt extruded from the extruder nozzle is air-cooled on a belt conveyor, and the resulting noodle-like material is cut with a pelletizer.

〔injection molding〕
Next, injection molding will be described. The pellets obtained in the above process are used as raw materials and injection molded. The injection temperature at this time is preferably 220 to 230 ° C. Of course, it is possible to mold by a molding method other than the injection molding means, but injection molding is suitable for supplying a practical product at a low cost. When the injection molding method is employed, there is no particular difference from normal injection molding. The mold temperature is preferably 40 to 80 ° C. Since the polymer component is less than usual, the molding shrinkage is small, and the solidified product is brittle. Therefore, in the mold production, it is necessary to design a mold in consideration of characteristics different from those of other resins such as molding shrinkage rate. That is, in the runner, sprue, etc., it is necessary to increase the tip end area of the ejector pin in order to increase the draft and to smoothly release the molded product.

[Hot water extraction process]
In this step, the molded product is immersed in warm water of 60 to 100 ° C., water-soluble components such as pentaerythritol are dissolved in warm water, and the remaining molded product is made porous. The extraction time varies depending on the extraction method and the thickness of the molded product. In the experiments by the present inventors, if the maximum thickness was about 3 mm, the countercurrent extraction method could extract 99% or more with 75 ° C. hot water for 6 to 10 hours. It was placed in a warm air dryer set at 80 to 90 ° C. for about 1 hour and dried to obtain a final product.

[Porous molded product]
The air permeation rate of the obtained porous body is measured. The air permeation speed is indicated by a Gurley value in accordance with JIS P8117. The Gurley value is the number of seconds required for 100 cc of air to pass through a circular area of 28.6 mmφ (6.42 cm ² ) at a gauge pressure of 0.013 atmospheres (definition is a pressure that weighs 567 g in 43 cm ² ). . The air permeation rate can be changed mainly by the addition amount of the third component, and when the addition amount is increased, the air permeation rate is increased and at the same time the physical strength is lowered. The opposite is true when the amount added is low. In terms of the Gurley value, when the thickness is 3 mm, it can be controlled almost in a few seconds to a few tens of seconds.

  In order to use it as a practically inexpensive vent plug, it must be shown that it can be used for a structure part though it is porous. In other words, an example is shown in FIG. 2, but it is conceivable that the shape is circular, the periphery is thick and the structure can withstand compression, the center is thin, and the air permeation is fast. Since the peripheral portion of the molded product of the present invention is fastened and fixed with a screw having a hole, the peripheral portion needs to be strong enough not to be broken by compression. PBT is a hard polymer compared to PP and has a certain strength even if it becomes porous, but in addition, it is used in a state where it has an appropriate physical strength without unnecessarily increasing the air permeation rate. Is preferred.

  When the surface of the porous body is viewed with a microscope, openings having a diameter of 0.5 to 10 μm are observed at an area ratio of about 5 to 30% of the surface area. Moreover, as an example, a porous body made from a compound containing about 1% glycerin has a plate-like material with a thickness of about 3 mm, a Gurley value of 5 to 10 seconds, and a water resistance of 0.005 to 0.01 MPa. It turns out that water also passes quite well. Since air passes at high speed and water passes sufficiently, it was found that many holes are continuous holes and are connected from the front to the back while intersecting. Although the diameter of the narrowest part of the hole cannot be imagined from the size of the opening of 0.5 to 10 μm, it is clear that it is not a nano-order fine diameter from the viewpoint of Gurley value and water resistance.

  Therefore, this porous body can be used as a filter medium. The end of the polyester polymer is probably an ester with pentaerythritol because the fabric should be polyester and baptized with alcoholysis. Therefore, the surface of the porous body is all hydrophilic including the inner surface of the pores. Therefore, it can be used for filtration and fractionation of aqueous emulsion. In particular, the inventors believe that blood filter media, aqueous bacterial culture media, and other biochemical functional filter media can be used. In addition to being inexpensive to manufacture, incineration is easy, safe and free from troublesome problems.

[Grant water repellency]
If the above-mentioned porous body can have water repellency, it is excellent in gas permeation while not allowing permeation of water or water droplets. For example, it can play the role of a vent plug in an in-vehicle lamp structure. . Many types of water repellents are sold in the market, but it seems that the porous body of the present invention is suitable for use of an aqueous PTFE emulsion material because the outer surface and the inner surface of the pores are hydrophilic.

  These are obtained by emulsifying a slightly low molecular weight PTFE using a surfactant. If the emulsion particle size is large, it is difficult to enter the pores. Therefore, it is preferable to enter the dipping process after cutting the emulsion using a homogenizer (high-speed rotating mixer). The immersion time is in balance with the water resistance of the final product, but is generally from several minutes to 1 hour. Pulled up from the emulsion, dried at around room temperature for about a day, and then forced-dried with a hot air dryer to obtain the final product.

[Operation of the present invention]
In general, when a light emitter, electronic circuit, relay circuit, motor, or other driving parts are used in a sealed container or a sealed type member to prevent ingress of dust or water, the sealed structure may be destroyed due to changes in internal pressure due to temperature changes. However, when the porous molded article of the present invention is used for a vent plug that is air permeable and sealable against water, this fear does not occur. In addition, the porous molded product of the present invention and the method for producing the same are functionally and functionally the same as the current product used for vent plugs made of PTFE nonwoven fabric, etc., due to the porous body of PBT, and the cost is low. Inexpensive.

  The porous molded article and the manufacturing method thereof of the present invention can provide an inexpensive and heat-resistant vent plug. Compounding pentaerythritol, which is a water-soluble, high-melting solid, and PBT resin, and having been able to injection-mold it, opened the way to the porous molded product used for the vent plug of the present invention. It was necessary to include a third component of the compound in the compound. A practical level of air permeation rate was obtained by adding the third component.

  Hereinafter, embodiments of the present invention will be described in the following examples.

Hereinafter, the Example which manufactured the porous molded article mentioned above is described in detail.
[Example 1]
Pentaerythritol (Mitsubishi Gas Chemical Co., Ltd.) 7.0 Kg, Glycerin (Wako Pure Chemical Industries, Ltd.) 0.15 Kg, and PBT “Tuffpet N1000 (Mitsubishi Rayon Co., Ltd.)” pulverized to 1 mm or less with a recycle crusher PBT 3 Kg Was stirred and mixed with a Henschel mixer, and this was adjusted to 250 ° C. under the supply port, but the others were controlled at 225 to 235 ° C. 32 mm biaxial extruder “BTN-32 (Plastics Engineering Laboratory Co., Ltd., Osaka, Japan) Fu)] Extrusion was performed at a rotational speed of 300 rpm at L / D = 30, and the molten extrudate was guided onto a belt conveyor and cooled and solidified by spraying and cold air, leading to a pelletizer and continuously cut.

  An injection mold for producing a disk-shaped molded product 1 having a diameter of 46 mm and a thickness of 2 mm was produced. This injection mold is mounted on a 50-ton type injection molding machine. In this injection mold, a cavity that is a section for molding the disk-shaped molded product 1 is disposed, and a gate 2 is disposed on the inner peripheral surface of the cavity. Molten resin is injected into this cavity via the gate 2. FIG. 1 is an external view of this disk-shaped molded product 1 that has been injection-molded. The injection molding conditions were injection molding with an injection temperature of 225 ° C. and a mold temperature of 50 ° C. The obtained 50 disk-shaped molded articles 1 were immersed in hot water at 75 ° C., and the hot water was replaced with a clean one every 4 hours and kept immersed for 10 hours. It was taken out from the hot water and left in a hot air dryer set at 80 ° C. for 2 hours.

  Although this disk-shaped molded product is a porous body, it was bent. I felt that there was a certain level of quickness because it broke from the center when bent to 90 degrees. The other five disk-shaped molded articles 1 were left for one day, and the air permeation rate was measured with an “automatic Gurley air permeability meter (manufactured by Matsubo Co., Ltd., Tokyo, Japan)”. Gurley values averaged 7 seconds. Thereafter, the water resistance was measured with a “high water pressure type water resistance tester WP-1000K (manufactured by Daiei Scientific Instruments Co., Ltd., Kyoto, Japan)”. The water resistance was 0.008 MPa.

  170 g of water is added to 30 g of PTFE emulsion type water repellent “Panaquiron wood / concentrated water-soluble type (Sawada Chemical Co., Ltd.)” and homogenizer “Hiscotron NS-310E (manufactured by Microtech Nichion Co., Ltd., Japan, Chiba) ) ”For 30 seconds. The obtained aqueous emulsion is transferred to a beaker placed in a large desiccator, and the above-described disc-shaped porous body 1 is put into the beaker and forcedly submerged in water like a holding lid with a metal net from above, and the desiccator lid Was closed and decompressed.

  The operation of reducing the pressure to about 200 mmHg and then slowly returning the pressure to normal pressure was repeated five times to remove air from the hole. The desiccator lid was opened for 15 minutes after returning to normal pressure, the porous body was taken out from the beaker, stood diagonally against the vertical wall, and allowed to stand and air-dried for 1 day. Next, corrugated paper was laid in a hot air dryer, and the porous bodies were arranged on the cardboard paper, and dried at 90 ° C. for 1 hour. Five of the obtained products were left for 1 day, and the air permeation rate was measured with an “automatic Gurley permeability meter (manufactured by Matsubo)”. The average Gurley value was 9 seconds. Thereafter, the water resistance was measured with a “high water pressure type water resistance tester WP-1000K (manufactured by Daiei Scientific Instruments)”. The water resistance was greatly improved to 0.098 MPa.

[Example 2]
Pentaerythritol (Mitsubishi Gas Chemical Co., Ltd., Tokyo, Japan) 7.0 Kg, Glycerin (Wako Pure Chemical Industries, Ltd., Tokyo, Osaka) 0.15 Kg, PBT “Toughpet N1000 (Mitsubishi Rayon Co., Ltd., Tokyo) Japan)) 32 kg twin screw extruder “BTN-32” L / D = 30, which was stirred and mixed with a Henschel mixer at 250 ° C. under the feed port, but the others were controlled at 225 to 235 ° C. The molten extrudate was guided onto a belt conveyor and cooled and solidified with spraying and cold air, and the tip was guided to a pelletizer and continuously cut.

  An injection mold was manufactured that had the same shape as in Example 1 and a disk-shaped molded product 1 (FIG. 1) having a diameter of 46 mm and a thickness of 2 mm under injection molding conditions. Ten obtained molded articles were submerged in 75 ° C. hot water, and the hot water was replaced with a beautiful one every 4 hours and kept immersed for 10 hours. It was taken out from the hot water and left in a hot air dryer set at 80 ° C. for 2 hours. When this plate-like product was bent, it was bent up to 35 degrees and cracked from the center, and it was found that it was inferior to the product obtained in Example 1. When the crack surface was observed with a magnifying glass, it was possible to imagine that there was a granular material with a large particle size and there was an undissolved PBT part at the time of extrusion. The air permeation rate was measured with an “automatic Gurley permeability meter (Matsubo Co., Ltd., Tokyo, Japan)”. Gurley values averaged 15 seconds.

[Comparative Example 1]
Compound pellets were produced in the same manner as in Example 1 except that glycerin was not added, injection molded, extracted with hot water, and the air permeation rate was measured with the obtained product. As a result, the Gurley value was 900 seconds on average of 10 pieces. Even if glycerin was not added, the air permeation rate was reduced by an order of magnitude or more.

[Example 3]
The final porous plate-shaped molded article was obtained by the same molding method and processing method as in Example 1 except that 0.2 kg of polypropylene glycol “PPG900 (manufactured by Showa Chemical Co., Ltd.)” was used instead of 0.15 kg of glycerin. Created. When this air permeation rate was measured, the average Gurley value was 30 seconds.

[Example 4]
Final porous disc-shaped product in the same manner as in Example 1 except that 0.2 kg of polyethylene glycol “PEG1000 (manufactured by Showa Chemical Industry Co., Ltd., Tokyo, Japan)” was used instead of 0.15 kg of glycerin. Created until. When this air permeation rate was measured, the average Gurley value was 80 seconds.

[Structural example 1 of porous molded product]
FIG. 2 is an external view of a porous molded product used for a vent plug. FIG. 3 is a cross-sectional view of the vent plug fixing structure when the porous component shown in FIG. 2 is incorporated. The porous molded product 3 shown in FIG. 2 has a cylindrical appearance, and a conical hole 4 is formed at the center. The porous molded product 3 constitutes a component of a vent plug, and is a vent component that is entirely porous and allows air to pass through. Since the thickness of the bottom 5 of the hole 4 is the thinnest, it becomes a main passage through which air passes. FIG. 3 is a cross-sectional view showing an example of a vent plug fixing structure using the porous molded product 3. A hole 7 is formed through the wall 6 of a container or the like that needs to be sealed. A large-diameter hole 8 is coaxially formed in the hole 7. An inner screw 9 is formed on the inner peripheral surface of the large-diameter hole 8.

  At the bottom of the large diameter hole 8, the porous molded product 3 is inserted and arranged. A fixing screw 10 is used to fix the porous molded product 3 to the bottom of the large-diameter hole 7. A male screw 11 is formed on the outer periphery of the fixing screw 10, and the male screw 11 is screwed into the inner screw 9 to press the porous molded product 3 against the bottom of the large-diameter hole 8 and fix it. The outer periphery of the porous molded product 3 is required to have such strength that it is not compressed and crushed by this pressing. A taper hole 12 for allowing air to pass therethrough is formed in the center of the fixing screw 10. Therefore, outside air passes through the tapered hole 11 of the fixing screw 10, the hole 4 of the porous molded product 3, and the bottom 5 thereof, and communicates with the inside and outside of the container.

  In this structure, a simple pressure test was performed as follows. The porous molded product 3 was inserted into the large-diameter hole 8, and the porous molded product 3 was temporarily fixed in the large-diameter hole 8 with a fixing screw 10. The temporary fixing position of tightening with the fixing screw 10 is an angular position where the fixing screw 10 is rotated until it does not turn lightly. From this temporary fixing position, the fixing screw 10 was further rotated 30 degrees and tightened and fixed. The 1300 parts thus obtained were subjected to this tightening test and then all were again disassembled and microscopically observed, but no cracks or the like were found in the periphery of the porous molded product 3.

  In addition, the fixing structure to the wall surface 6 of the semi-sealed container of the porous molded product 3 described above is based on the inner screw 9 and the fixing screw 10. However, the structure is not limited to this. When the semi-sealed container is molded, other fixing means such as a method of inserting the porous molded product 3 and fixing it at the time of molding, bonding with an adhesive, or mechanical press-fitting may be used.

FIG. 1 is an external view of a plate-like molded product for Gurley value measurement. FIG. 2 is an external view of a porous molded product used for a vent plug. FIG. 3 is a cross-sectional view of the vent plug fixing structure when the porous component shown in FIG. 2 is incorporated.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Molded product for Gurley measurement 3 ... Porous molded product 4 ... Hole 6 ... Wall part 7 ... Through-hole 9 ... Internal screw 10 ... Fixing screw

Claims (6)

It consists of 60 to 85 parts by weight of pentaerythritol, 15 to 40 parts by weight of polybutylene terephthalate resin, and one or more 0.25 to 3 parts by weight selected from polyfunctional alcohol, polyethylene glycol, and polypropylene glycol that are liquid at room temperature. Make a molded product,
By immersing this molded article in water, the water-soluble component in the molded article is dissolved in the water and removed to form a porous material having gas permeability in the molded article. Goods. In the porous molded article shown in claim 1,
In order to improve the water resistance, the molded article immersed in the water is immersed in an aqueous emulsion of a tetrafluoroethylene polymer, and then the molded article is dried to obtain the surface of the porous body and the porous A porous molded article obtained by adhering a tetrafluoroethylene polymer to the inner surface of the pores in the porous body. A pelletizing step in which a mixture containing pentaerythritol, polybutylene terephthalate resin, and a third component is melt-mixed at 200 to 235 ° C. and extruded into pellets;
An injection molding process for molding a molded product by injection molding by an injection molding method;
A method for producing a porous molded article comprising an extraction step of immersing the molded article in water or hot water to extract a water-soluble component. In the manufacturing method of the porous molded article of Claim 3,
A method for producing a porous molded article comprising a dipping step of dipping in an aqueous emulsion of a tetrafluoroethylene polymer after the extraction step and drying. A semi-sealed container using the porous molded article according to claim 1 or 2 as a vent plug,
A semi-hermetic container having fixing means for fixing the porous molded product to the wall surface in order to dispose the porous molded product so as to close a through-hole penetrating the wall surface of the container. The semi-sealed container according to claim 5,
The semi-sealed container, wherein the fixing means is an inner screw formed on an inner peripheral surface of the through hole and a fixing screw screwed into the inner screw.

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