JP2010024361A - Vent plug and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a PBT resin porous body vent plug, which has high air permeability and improved water repellency and is mass-producible at low cost; and to provide a material for the vent plug. <P>SOLUTION: A compound of PBT, pentaerythritol and glycerine is produced. The compound is injection-molded into a molded material. From the molded material, pentaerythritol is extracted with hot water. The molded material after extraction with hot water becomes a PBT porous body. After drying, the porous body is impregnated with an organic solvent solution containing 1-5% concentration of methyl silicone compound. When the porous body is taken out to be dried, and then, heated to be cured, the vent plug is obtained. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a ventilation component that is generally used in mobile machinery, electronic equipment, electrical equipment, general machinery, and other manufacturing fields. More specifically, the present invention relates to a vent plug used for a part that needs to be sealed, for example, a case part of a headlight or a backlight of an automobile, a case of a rotating device such as a motor of an electronic device or a home appliance, and a manufacturing technique thereof.

  Sealed parts such as cases of automobile headlights and backlights, motors of mobile electronic devices, cases of important parts, and the like are exposed to low or high temperatures of the outside air and high temperatures due to heat generation of internal parts. It is most preferable to completely seal these cases to prevent intrusion of foreign matter such as water and dust. However, if a sealed space is created, the air enclosed in the interior may be affected by long-term temperature changes, temperature shocks, etc. The internal pressure changes, which can lead to the destruction of the case.

  For this reason, a large number of parts that prevent the intrusion of water and dust while making the internal pressure equal to the external pressure, that is, a vent plug that has water repellency and prevents the ingress of water while allowing air to enter the outside. Also, in the case of important parts such as motors for indoor electronic devices and household appliances, it is equally important to prevent dust from entering, although it is not as susceptible to temperature changes as parts used outdoors. In many environments, vent plugs having similar functions are frequently used.

  Various types of such vent plugs have been developed, but most of the current vent plugs are made by bonding a nonwoven fabric made of polytetrafluoroethylene resin (hereinafter referred to as “PTFE”) to a cylindrical plastic part. It is. As an example of this technique, a ventilation member configured as a ventilation sheet is known (see, for example, Patent Document 1). The ventilation member has a breathability and a waterproof property. For example, a packing made of a nonwoven fabric as a waterproof breathable membrane made of PTFE in which a large number of irregularly shaped micropores having a pore diameter of 0.1 μm to 10 μm are formed. A sheet is laminated.

  As described above, the functions described above have been achieved by using vent plug parts in the past, and no new product has yet been found to compete with the current product. However, the current product also has many problems, for example, that the PTFE nonwoven fabric is expensive, the reliability of the process of pasting the PTFE nonwoven fabric is not high, and therefore 100% inspection is required before shipment. And so on. Therefore, the high cost is a difficult point.

  The inventors have already prototyped a vent plug by another method different from the conventional one and have already disclosed that it has sufficient performance (see Patent Document 2). First, a polybutylene terephthalate resin (hereinafter referred to as “PBT”), pentaerythritol, and a small amount of a third component (compound) are prepared, and injection molding is performed using this as a raw material. The molded product is subjected to an extraction process in which it is immersed in hot water to obtain a porous body from which pentaerythritol and the like are extracted.

  After drying, it is immersed in a suspension in which a PTFE emulsion-based water repellent is dissolved and left for a long time, and then dried to form a vent plug. This vent plug has high breathability and water repellency, and uses PBT, which is also a heat-resistant engineering plastic. Therefore, it is more reliable and lower in cost than the PTFE vent plug described above. Cost reduction is possible and effective.

On the other hand, as the water repellent, a silicone-based one is applicable over many fields as having water repellent effect, and is commercially available. A methyl silicone polymer compound is an example, and its properties are disclosed in Non-Patent Document 1.
JP 2006-315725 A JP 2008-007534 A Toray Dow Corning Technical Data N0. F001, p9

  However, as a result of research and development of a mass production method for the manufacturing method of the vent plug of Patent Document 2, it has been found that the method is still unstable in obtaining water repellency. Theoretically, it can be manufactured as described above. However, particularly in mass production, there are still places where the water repellency is maintained and there is room for improvement. Briefly describing the instability, the average diameter of the continuous bubbles possessed by the vent plug itself is not sufficiently large compared to the PTFE emulsion diameter in the water-repellent agent-provided aqueous solution.

  The water repellency-imparting material used by the present inventors is a PTFE emulsion produced by emulsion polymerization, and a PTFE polymer is made hydrophilic by surrounding surfactant molecules. The particle diameter range of the commercially available PTFE emulsion is not particularly determined, and basically it is adsorbed on the surface of cloth or paper to impart water repellency. Therefore, the diameter (emulsion diameter) was large, probably because PTFE polymer was aggregated or associated.

  In response to this fact, the present inventors have not yet achieved a stable and highly dispersed PTFE emulsion with ultrafine particles of tetrafluoroethylene emulsion polymerization. In order to stably supply ultra-fine and highly dispersed PTFE emulsions, the storage time is long, and even when the storage temperature is increased, the emulsions do not aggregate or associate with each other and can maintain the particle size during production. is necessary. Therefore, the present inventors tried to create a large-diameter open-cell PBT porous body that can adsorb a commercially available PTFE emulsion to the hole wall at the back of the porous body. As a result, there was a problem such as a sharp drop in the mechanical strength, which was insufficient for the construction of mass production technology for stable production.

  The inventors reviewed the current product and made efforts to improve it. The current PTFE nonwoven fabric is expensive, and when it is burned after automobiles are discarded and shredded dust, it may change to hydrogen fluoride and damage the combustion furnace. On the other hand, the materials used in the above-mentioned invention (Patent Document 2) obtained by the present inventors are PBT and pentaerythritol, which is an inexpensive chemical material. In addition, pentaerythritol can be easily recycled and lost resources. There is very little material.

  In addition, the vent plugs considered by the present inventors require a water repellent treatment, and the water repellent is generally expensive. However, in the present invention, the amount used is only the amount adsorbed on the surface area including the pores of the PBT porous body, and the amount of adsorption is not so great even if the surface area is large. If the vent plug according to the present invention can be mass-produced, the environmental load is reduced and the cost is likely to be reduced.

  The present inventors used the technique up to obtaining a porous molded product made of PBT because the technique shown in Patent Document 2 described above can be used. On that basis, we selected a suitable water repellent and conducted research on its application. Accordingly, the possibility of a vent plug suitable for mass production was sought, and an organic solvent was used when imparting water repellency.

  On the other hand, as described above, the methyl silicone polymer compound has a water repellent effect. It is well known that silicone has the basic property of repelling water, is commercially available and can be easily purchased. This silicone is known to be used for lipsticks and the like, but recently it has been used as a textile treatment agent for sportswear. Commercial products of this methyl silicone polymer compound are all polymer solutions having molecular weights of several thousand to several tens of thousands. If it is made easy to adhere to the PBT and the water repellency is increased, it can be manufactured at low cost and capable of mass production.

  Already, water repellents that can be dissolved in an organic solvent by imparting water repellency to fabrics and paper products have been developed and used, and there are examples of mass production processing of umbrellas and waterproof fabrics. Since the immersion liquid is not an emulsion type but a solution type, the dissolved water repellent molecular diameter is considered to be easily adsorbed on the surface of the porous body without aggregation or association. The present inventors improved a porous body obtained by the technique of Patent Document 2 and then tried a soluble water repellent to search for an optimum water repellent to be applied to the porous body.

  The present invention has been developed based on the above technical background, and achieves the following object. An object of the present invention is to provide a vent plug and a manufacturing technique thereof that enhance the water repellency effect, realize cost reduction, and enable mass production.

The present invention takes the following means in order to achieve the object.
The vent plug according to the present invention 1 comprises a compound containing 25 to 40% by mass of polybutylene terephthalate resin, 75 to 60% by mass of pentaerythritol, and 0.25 to 2.5% by mass of a liquid polyfunctional alcohol compound. Then, the compound was injection molded, and the vent plug-type injection molded product obtained by the injection molding was immersed in water to extract alcohols, and then dried to form a porous body. The injection-molded article is manufactured by immersing in an organic solvent solution of a methyl silicone polymer compound to adsorb the silicone polymer compound, and then drying and volatilizing the organic solvent. And
When this vent plug is a plate having a thickness of 2 mm, the air permeability is a Gurley value of 25 seconds or less and the water repellency is a water pressure resistance of 1 m or more.

The method for producing a vent plug according to the present invention 2 includes 25 to 40% by mass of polybutylene terephthalate resin, 75 to 60% by mass of pentaerythritol, and 0.25 to 2.5% by mass of a liquid polyfunctional alcohol compound. A compound creating step for creating a compound, a molding step for obtaining a vent plug type injection molded product by injection molding the compound with an injection molding machine, and alcohols were extracted by immersing the injection molded product in water. Thereafter, an extraction step for drying to form a porous body, and an immersion step for immersing the injection molded article that has become the porous body in an organic solvent solution of a methyl silicone polymer compound to adsorb the silicone polymer compound; And a drying step of drying the injection molded product that has undergone the dipping step to volatilize the organic solvent.
When the vent plug obtained by this manufacturing method is a plate having a thickness of 2 mm, the air permeability is a Gurley value of 25 seconds or less, and the water repellency is a water pressure resistance of 1 m or more.

  The vent plug manufacturing method according to the present invention 3 is the vent plug manufacturing method according to the present invention 2, wherein the drying step comprises heating the injection-molded product to a temperature of 140 ° C. or higher to form the methyl silicone polymer. And a step of fixing the compound.

  The vent plug manufacturing method according to the present invention 4 is the vent plug manufacturing method according to the present invention 2 or 3, wherein the organic solvent solution has a methyl silicone polymer compound concentration of 0.5% by mass or more. It is characterized by that.

  The method for producing a vent plug according to the present invention 5 is characterized in that, in the method for producing a vent plug according to 1 selected from the present inventions 2 to 4, the polyfunctional alcohol compound is glycerin.

Hereinafter, a preferable manufacturing process of the target air vent plug will be described in detail.
[Preparation of PBT / pentaerythritol compound]
As raw materials for the compound, pentaerythritol, PBT, and liquid polyfunctional alcohol are used. As pentaerythritol, commercially available pentaerythritol can be used, and the dimer (exactly dehydrated dimer) and trimer (exactly dehydrated trimer) may be included. Those containing the dimer and trimer are collectively called “pentaerythritol”.

  As PBT, commercially available PBT pellets can be used, but PBT powder can be preferably used. As the liquid polyfunctional alcohol, glycerin, ethylene glycol, propanediol, butanetriol and the like can be used. However, it is inexpensive and most suitable for the functions required by the present inventors is glycerin, and its use is particularly preferred.

  In preparing the compound, the mixing composition ratio may be 25 to 40% by mass of PBT, 75 to 60% by mass of pentaerythritol, and 0.25 to 2.5% by mass of glycerin, which is a polyfunctional alcohol compound. preferable. Even when the amount of PBT used is 25% by mass or less, a porous body having a desired air permeability and water pressure resistance can be produced. However, the strength (structural strength) is low, and there is a possibility that it may be damaged in the field use as a vent plug, and it is difficult to release in injection molding. On the other hand, when the PBT usage fee is 40% by mass or more, the air permeability of the final product is low.

  Further, if the composition ratio of glycerin is 0.25% by mass or less, the air permeability of the final product is insufficient, and if it is 2.5% by mass or more, the strength (structural strength) of the final product is unsatisfactory. Not enough and practical. Therefore, it is not recommended that the ratio of PBT and glycerin is other than the above-mentioned preferred ratio. All the raw materials which become the predetermined mixture ratio selected preferably are mixed with mixing agitators, such as a Henschel mixer, and let it be a feed material to an extruder.

(Extruded molding)
The stirred raw material is heated and melted and extruded by an extruder, and cut into pellets. The extrusion method described below is based on the application of the present inventors. Since the details of the technical contents are described in Patent Document 2, detailed description thereof is omitted, but the principle includes a different method from a simple melt extrusion method. These have been found by the present inventors and contain important contents related to the present invention, and will be described again.

  That is, when commercially available pentaerythritol is heated, it melts at a temperature of approximately 190 ° C., and when heated further exceeds a temperature in the vicinity of 230 ° C., a dangerous situation similar to a boiling situation in which water vapor is generated occurs. According to a general chemical manual, the melting point of pentaerythritol is around 260 ° C., which is different from the melting point (˜190 ° C.) of the commercial product. The difference is that when pentaerythritol melts and becomes liquid, it is easily dehydrated and dimerized, and the equilibrium of pentaerythritol and its dehydrated dimerized product is more than 10% over the latter at a temperature around 250 ° C. It is by giving.

  The temperature of about 190 ° C. is the melting point of pentaerythritol containing about 10% of the dehydrated dimerized product, and the commercial product is this composition. The following method is employed to accurately measure the melting point of pentaerythritol. That is, the recrystallization method using a solvent is repeated to obtain a high purity pentaerythritol crystal, and the melting point is measured using this as a sample. When measured by this method, the melting point is a temperature of 255 to 260 ° C.

  However, in this melting point measurement, pentaerythritol melts and at the same time emits water vapor to a boiling state, and immediately a dimer is formed nearly 10%. When the dimer-containing pentaerythritol obtained by immediately cooling the sample is heated again, it melts at a temperature around 190 ° C., and when the temperature is further raised, water vapor is emitted at a temperature around 230 ° C. The reaction proceeds.

  That is, the temperature of 190 ° C. is the melting point of pentaerythritol containing about 10% of the dimer, and water vapor is emitted again at a temperature of 230 ° C. or higher because of the equilibrium reaction to the dimer and the dimer. This seems to be because the equilibrium reaction to the trimer proceeds further. However, since the dimer and the trimer are solid alcohols and have high water solubility, the role in the present invention remains unchanged. Therefore, the whole including these dehydrated oligomers is referred to as “pentaerythritol” in the present invention.

  On the other hand, the commercially available PBT has a substantial melting point of 250 to 260 ° C., and if it is attempted to melt and mix with the above-mentioned commercially available pentaerythritol, it will exceed the dangerous temperature of 230 ° C. In short, when the temperature is raised to the melt mixing temperature, commercially available pentaerythritol undergoes a dehydration condensation reaction and generates steam violently, so that the internal pressure rapidly rises in the extruder and is dangerous.

  The present inventors have described this countermeasure in the above-mentioned Patent Document 2, but the generation of the dehydration reaction is suppressed by extruding while keeping the screw / cylinder temperature of the extruder at a single temperature of 230 ° C. did. By this method, any polyester dissolves somewhat in hot alcohol, but particularly in a pentaerythritol solution at a temperature of 230 ° C., PBT, which is a polyester, dissolved very well. It is thought that it was caused by pentaerythritol, which is a polyfunctional alcohol having 4 hydroxyl groups, that dissolved well.

  The inventors noted the transesterification of PBT with pentaerythritol. Even if there is no catalyst at a high temperature, a transesterification reaction occurs between the polyester and the alcohol. When the transesterification reaction occurs, the polyester molecules are eventually cleaved and shortened. If the PBT is shortened, it is not preferable because the mechanical strength of the final vent plug is lowered even if compounding is frequently performed. Therefore, the main point of the extrusion process is that the cylinder temperature is not set to 230 ° C. or more, and the L / D of the extruder is substantially shortened to speed up the discharge.

  Most preferably, the melt extruded from the extruder is solidified with cold air. However, cold air solidification is expensive to create process equipment. For this reason, it is effective that the melt is solidified and cut after passing through cold water. Cold water having a temperature close to 0 ° C. is effective because pentaerythritol has low solubility in water and solidifies quickly.

  Although the composition of the pellets to be obtained varies slightly, in other words, the pellets only need to have the target composition, and a slightly larger amount of pentaerythritol may be added to prepare the raw material. The cooling water is circulated while being cooled by a cooling device so as not to raise the temperature. Pentaerythritol crystals adhere to the cooling part of the cooling water after a long period of use, but this may be removed and reused.

〔injection molding〕
The pellets obtained in the above step are injection molded using the raw material to obtain a vent plug shape. The shape of the test prototype obtained by the present inventors was a disk-like product having a thickness of 2 mm and a diameter of 46 mm. The injection temperature was up to 240 ° C, and the mold temperature was about room temperature to about 70 ° C. If the injection temperature is raised too much, water vapor is generated in the injection cylinder due to the dehydration condensation reaction of pentaerythritol. For this reason, the molding operation becomes difficult, and it is necessary to suppress the temperature to 245 ° C. at the highest. Even in this case, smooth molding is required so that the residence time in the injection cylinder does not become too long.

  However, what should be noted is the shape of the molded product. That is, since the raw material uses a much lower proportion of the polymer in the injection product than that of normal resin molding, the molded product has a molding shrinkage rate close to zero. If the molding shrinkage is close to zero, the mold may not be released smoothly. Therefore, at the time of mold release, a hole is formed in the molded product due to the extrusion of the ejector pin, and even if the mold can be released, the molded product may be broken, which is likely to cause trouble. In order to solve this problem, it is necessary to use a shape with a high draft so that it can be easily released, or to design a die for ejector pins and ejector plates that have a large area of extrusion. It is preferable to take such considerations.

[Pentaerythritol extraction]
It is preferable that the molded product obtained in the above step is put in a large amount of water at a temperature of 50 to 80 ° C. and left to extract pentaerythritol and glycerin in the molded product. When immersed for 6 hours, most of the components dissolve in hot water. Then, it is preferably taken out from the hot water and dipped in another new hot water, dipped for another 6 hours, taken out, put into a hot air dryer at a temperature of about 90 ° C. for 24 hours and dried. When there is a large amount of immersion material and there is a possibility of overlapping in the tank, slow stirring is necessary to prevent overlap.

  In a large amount of continuous mass production processing, a countercurrent extraction device as shown in FIG. 1 can be used. Water tank 1, water tank 2, and water tank 3 in FIG. 1 are water tanks in which water can be stored and temperature controlled, and the water in each water tank 1, water tank 2, and water tank 3 is automatically controlled to a temperature around 70 ° C. Yes. A small amount of tap water or industrial water is always supplied to the water tank 1 from the supply pipe 6. The water overflowing from the water tank 1 is supplied to the water tank 2, the water overflowing the water tank 2 is supplied to the water tank 3 in order, and the water overflowing the water tank 3 is supplied to the cooling tank 4. In the cooling tank 4, the refrigerant cools water through the refrigerant pipe 9 to a temperature near 5 ° C. In the cooling bath 4, dissolved pentaerythritol is deposited, and the deposit adheres to the inner wall of the cooling bath 4 and the refrigerant pipe 9.

  As a result, the concentration of pentaerythritol in the water decreases, and the water is returned to the water tank 2 through the pump 5 and the pipe 7. A part of the water in the cooling tank 4 is discharged through the pipe 8. Since the discharged water contains pentaerythritol and glycerin and has a high BOD, it is treated with activated sludge after drainage. The immersion jig 10 is an immersion jig containing a molded product, and the immersion jig 10 is immersed in the water tank 3 in the opposite direction of the water flow.

  Next, in the method of immersing in the water tank 2 and then in the water tank 1, it is fed in the direction indicated by the arrow in FIG. The immersion time in the water baths 3, 2, 1 is about several hours, and finally 99% or more of pentaerythritol is extracted. Moreover, 90% or more of pentaerythritol can be collect | recovered by collect | recovering the deposits in the cooling tank 4 occasionally, and drying naturally. Thus, the molded product in the immersion jig 10 becomes a porous body.

[Water repellent and its supporting method on the porous body]
A wide variety of water repellents have been developed as described above. Among them, the property required by the present inventors for the water repellent is firstly that the size (the diameter of molecules, ions, emulsion, etc.) is small when dispersed in a solvent. This is to ensure that the water repellent can penetrate from the surface of the porous body through the hole to the central portion. The emulsion type has a large diameter and cannot be penetrated deeply, so use a solvent-soluble one.

  Further, it is preferable not to desorb or move (desorb and re-adsorb) after adsorption, and it is desirable that the moving speed is slow even if there is movement. For this purpose, a polymer having a certain molecular weight, that is, a polymer having a molecular weight of several thousand or more is desirable. However, a so-called injection molding polymer having a molecular weight of 100,000 is too low in solubility in a solvent. Therefore, the water repellent is preferably a polymer having a molecular weight of about several thousand to 10,000.

  What is generally known as a water repellent is either a fluorinated hydrocarbon polymer compound or a silicone polymer compound. The water repellency is superior to the former, but more expensive than the latter. The latter are products such as silicone oil, silicone sealant, and silicone rubber that are consumed in large quantities, and can be obtained at low cost thanks to these mass-consumed products.

  In the present invention, the carrier to which the water repellent is adsorbed is a thick porous body, the surface area of the carrier is sufficiently wide, and the pore diameter is small, so that the water repellent is likely to approach water droplets. Therefore, in the present invention, even if a silicone-based water repellent is used, it is possible to provide a water repellent function at a level that can be used as well as a fluorine-based compound. In the present invention, among commercially available silicone materials for coating, a silicone material for coating using a methyl silicone polymer compound is used. There are many manufacturers of silicone materials in Japan and overseas, and each manufacturer handles several types of commercial products. Each is a polymer having a molecular weight of thousands to tens of thousands, and is commercially available as a solution of a hydrocarbon-based organic solvent.

  These commercially available products have a basic structure of dimethylpolysiloxane and are modified so that they can be further polymerized and cured after coating. The principle of curing differs depending on the product, but the molecular end is partially modified to condense the compounds with other molecular ends by dealcoholization reaction, deoxime reaction, etc. And a method such as bonding by radical reaction is employed. Many of these commercially available products are the condensation-curing type, but in these systems, there are catalysts that accelerate the curing, and there are some that have already been added at the time of commercialization.

  Such a catalyst capable of promoting curing is dibutyltin or the like. However, there is a problem that tributyltin, which is an environmental hormone, is produced as a by-product in the production of dibutyltin and cannot be completely removed in the purification process. Recently, research and development have been conducted to change the catalyst to a non-tin product. In order to cope with environmental problems, the present invention considers the use of a methyl silicone compound that does not contain a curing accelerating catalyst, and has a sufficient water-repellent function over the long term.

  That is, the basic structure of the methyl silicone compound that the present inventors use as a water repellent is dimethylpolysiloxane. Dimethylpolysiloxane is a kind of so-called silicone oil, and itself has water repellency. Non-Patent Document 1 described above describes a case where dimethylpolysiloxane is applied to some material (herein referred to as a carrier).

  According to this, the oxygen atom of dimethylpolysiloxane itself is semi-bonded with the carrier, and the silicon atom is floated and aligned along the carrier, and two methyl groups from each silicon atom are exposed from the carrier surface to the outside. It is said that strong water repellency occurs when it is lined up in the opposite direction (in a state where it is evenly forested). In short, a thick dimethylpolysiloxane layer like a liquid phase has water repellency but is not so strong, and when it is coated very thinly, it has a high water repellency when it is evenly aligned on the carrier with some transition. It is a description of birth.

  Chemically speaking, it is an interpretation that a silicon atom is not a water-repellent root, but a methyl group bonded to silicon, and a methyl group standing in a group is a water-repellent root. In the present invention, since the support is PBT which is a heat-resistant polymer, it can be heated to a temperature of hundreds of degrees Celsius after being thinly coated, and dimethylpolysiloxane molecules can obtain thermal motion and be aligned as described above. The application is possible. In addition, by maintaining the high temperature for a long time, the condensation reaction proceeds even without a catalyst, the polymer can be polymerized, and the methyl group can be baked onto the support surface.

  That is, to repeat, in order to make the methyl group evenly forested on the support, after the dimethylpolysiloxane is placed on the support, the temperature is raised to increase the thermal vibration of the polysiloxane molecule. This is to increase the chance of interference between the oxygen atom and the carrier (PBT in the present invention), and increase the number of semi-bonds with the carrier in the process. The support is a heat-resistant PBT, and no significant change in the porous material occurs up to a temperature of about 170 ° C.

  However, even if it is below the PBT melting point or softening point, if it is placed under a high temperature close to this, the microstructure changes as in the case of annealing. Specifically, it has been confirmed by experimental results that the air permeability becomes unstable at a temperature higher than this, with a temperature of 180 to 200 ° C. as a boundary.

  The present inventors believe that heating at a temperature of 120 ° C. or higher is necessary in order to increase the water repellency by evenly growing the methyl groups of dimethylpolysiloxane on the carrier. At the same time, dimethylpolysiloxanes are condensed to form a polymer and fixed (baked) on the carrier. Therefore, if no catalyst is used, heating at 120 ° C. or higher, preferably 150 to 160 ° C. is desired.

  Furthermore, baking conditions will be described. It is difficult to say that 120 ° C. is a sufficiently high temperature for the condensation of dimethylpolysiloxane without a catalyst. However, the purpose can be achieved by setting the heating time to a long time of several days. In consideration of these, the present inventors set the water-repellent baking conditions for manufacturing a standard vent plug for one day and night for a temperature of 120 ° C. and several hours for a temperature of 150 ° C.

  However, it is not limited to this baking condition, and it is only necessary to conduct experiments in accordance with the obtained porous body and set conditions appropriately. That is, the evaluation of the vent plug is determined by repeating the air permeability, the water pressure resistance, and the temperature shock cycle of −55 ° C./+100° C. level about 1000 times, and the subsequent water pressure test. The water repellent is attached to the porous body by immersing the porous body in a water repellent solution using a light organic solvent.

  Many coating silicone materials using commercially available methyl silicone compounds are dissolved in isoparaffin, toluene, xylene, etc., and these can be preferably used if they are further diluted with the same solvent as they are. After soaking, it is dried with warm air to volatilize the solvent, and a water repellent is placed on the carrier. Although only the solvent is volatilized has water repellency, as described above, it is preferable to heat these at higher temperatures to further increase the water repellency. In this case, the heating temperature is 120 ° C. or higher, preferably about 150 ° C.

  Next, a specific process for imparting water repellency will be described. First, in order to adhere the water repellent thinly and uniformly to the porous body, the water repellent is diluted with a light hydrocarbon such as hexane so that the concentration of the methyl silicone material in the liquid is 0.25% by mass or more. A dipping solution is used. The concentration is preferably 1 to 5% by mass. The water repellent solution is taken in a container, and the molded article after the water immersion extraction / drying process is put into the container, left for 1 hour to several hours, and then the molded article is taken out from the container and air-dried.

  This air drying is suitable for volatilizing most of the light volatile solvent. Next, it is desirable to remove most of the solvent by putting in a drier and performing hot air drying at a temperature of 90 to 100 ° C. for about 1 hour. Then, it is preferable to raise the set temperature of a warm air dryer to the temperature of 120-150 degreeC, hold | maintain and bake for several hours-several days.

[Product Evaluation / Air permeability]
Next, the product of the present invention is evaluated using a Gurley type air permeability meter which is originally a measuring machine for measuring the air permeability of paper or cloth. Since the PTFE nonwoven fabric product which is the current vent plug is also evaluated using the same air permeability meter, it is a comparative measurement. The air permeability is indicated by a Gurley value, which is expressed as the number of seconds in which 100 cc of air passes through a paper or cloth when air having a differential pressure of 1220 Pa (0.012 atm) is applied to an area of 6.42 cm ² . The product manufactured according to the present invention has a thickness because it is shaped by injection molding, but the air permeability of the product of the present invention is inversely proportional to the thickness.

  In general, thin Gurley values can be lowered and can be used for products that require high air permeability, but in actuality, the product of the present invention is a porous body, compared to general resin molded products. Then the mechanical strength is low. That is, the present inventors believe that a product having a thickness of 0.5 mm or less should not be used as a practical product. However, if the Gurley value as a 2 mm-thick flat plate shaped product is about 10 seconds, the Gurley value is 5 seconds for a 1 mm thick product and 2.5 seconds for a 0.5 mm thick product. This level of air permeability satisfies the requirements for sufficient use as a vent plug.

  Furthermore, in applications where air permeability is not good, reduce the glycerin content in the original compound or change the type of liquid polyfunctional alcohol in the compound (change glycerin to ethylene glycol) Or any one of them may be performed. As a result, the air permeability can be lowered without changing the shape of the vent plug. If the shape of the vent plug may be changed, the thickness of the ventilation portion may be increased or the area of the ventilation portion may be reduced.

[Product Evaluation / Water Repellency / Water Pressure Resistance]
A commercially available measuring machine was used to measure the water pressure resistance. The purpose of the water pressure measuring machine is to measure the water pressure resistance of umbrella cloth, waterproof cloth and waterproof paper, and the measuring object is usually a large object having a diameter of about 150 mm or more. A vent plug having such a size is not required, and the porous body obtained by the present inventors is about 50 mm in diameter and smaller than the above, so the following device has been devised. That is, a vinyl chloride sheet having a thickness of 1 mm was purchased, cut into a square with a side of 200 mm, and a hole with a diameter of 30 mm was formed in the center. A vent plug sample was attached with an adhesive so as to cover the hole. The water pressure resistance was measured after the adhesive was fully cured.

  Since the PTFE non-woven fabric used for the vent plug is also required for the water pressure resistance by the above-described method, the water pressure resistance is measured using this kind of apparatus in the present invention. From the measurement results, when the vent plug of the product of the present invention is a flat plate having a thickness of 2 mm, a water pressure resistance of 1 m or higher and a high one of 3.0 m or higher can be obtained. The water pressure resistance of the product of the present invention is almost proportional to the product thickness. This is because the water repellent is adsorbed on the entire inside of the open cell.

  The PBT vent plug, which is the porous molded article of the present invention, can enhance the water repellent effect by using a methyl silicone compound as the water repellent. The air permeability when a plate-like material having a thickness of 2 mm is a Gurley value of 25 seconds or less, and the water repellency is a water pressure resistance of 1 m or more. In addition, it was possible to manufacture a vent plug that could be mass-produced and reduced in cost by using an inexpensive material.

  Embodiments of the present invention will be described below in place of the following examples.

Hereinafter, examples of the present invention will be described in detail along with comparative examples.
The evaluation / measurement methods for the composites obtained from the examples are shown below.
(A) Air permeability measurement (Gurley value measurement)
A “Gurley Densometer” (manufactured by Toyo Seiki Seisakusho (Tokyo, Japan)) was used.
(B) Water pressure measurement A “high water pressure type water resistance tester” (manufactured by Daiei Kagaku Seiki Co., Ltd. (Kyoto, Japan)) was used.
(C) Temperature shock test A "TCC-150W temperature shock tester" (manufactured by ESPEC Corporation (Osaka, Japan)) was used.

[Example 1] (Preparation of PBT porous body)
Commercially available PBT “Toraycon 1401 (manufactured by Toray Industries, Inc., Tokyo, Japan)” was pulverized with a resin crusher “Turbo Disc Mill TD-150 (manufactured by Matsubo, Inc., Tokyo, Japan)”. The pulverized product was applied to a 20 mesh shifter, and the powder side was recovered and used as a PBT raw material. As the pentaerythritol, a commercially available product “Pentaerythritol (Mitsubishi Gas Chemical Co., Ltd., Tokyo, Japan)” was used. This contained about 10% dehydrated dimer. As glycerin, “glycerin (manufactured by Showa Chemical Co., Ltd.)” was used.

  In a Henschel mixer, 30 parts by mass of PBT, 69 parts by mass of pentaerythritol, and 1 part by mass of glycerin were mixed well. Subsequently, the cylinder temperature was all set to 230 ° C. with an extruder “FS50-22 (manufactured by Ikekai Tekko Co., Ltd.)” and high-speed extrusion was performed. The extruded product was solidified at high speed through cold water at a temperature of 5 ° C. and crushed with a pelletizer. The cured product was hard but brittle, and the pelletizer was cut into pellets slightly mixed with powder, but was used as it was.

  The above extruded product is applied to a 60T type injection molding machine “PS-60 (manufactured by Nissei Plastic Industry Co., Ltd. (Nagano, Japan))”, the injection temperature is 230 ° C., the mold temperature is 50 ° C., the thickness is 2 mm and the diameter 200 pieces of 46 mm disk-shaped objects were injection molded. Dip several discs into 20 liters of hot water at a temperature of 70 ° C. Stir lightly for about 1 minute every hour for the first 8 hours and leave for 24 hours. Replace the hot water with a new one and keep the temperature at 70 ° C. The same operation was carried out for 24 hours and then taken out after 24 hours. Further, the hot water was replaced with a new one, and the same operation was carried out at a temperature of 70 ° C., followed by taking out after 24 hours. When the air permeability of the disk-shaped material after drying was measured, the Gurley value was in the range of 11 to 21 seconds, and the average was 16.8 seconds.

[Example 2] (Preparation of PBT porous material)
Except that the initial compound recipe was 30 parts by weight of PBT, 69.5 parts by weight of pentaerythritol, and 0.5 parts by weight of glycerin, the same experiment as in Example 1 was performed. The obtained porous body had an average Gurley value of 20.8 seconds, and the air permeability was slightly lower than that of Example 1.

[Comparative Example 1] (Preparation of PBT porous material)
Except that the initial compound recipe was 30 parts by weight of PBT, 70 parts by weight of pentaerythritol, and 0 parts by weight of glycerin, the same experiment as in Example 1 was performed. The Gurley value of the obtained porous body was 150 seconds or more for all 10 sheets measured, and the average was 190 seconds. The air permeability was significantly lower than in Examples 1 and 2.

[Example 3] (Preparation of PBT porous body)
Except that the initial compound recipe was 30 parts by weight of PBT, 67.5 parts by weight of pentaerythritol, and 2.5 parts by weight of glycerin, the same experiment as in Example 1 was performed. Although a porous material was obtained, the production process was somewhat difficult. In other words, the runners were often broken during the mold release in the injection molding process, and it took time to collect the runners. Therefore, the molding cycle was not stable. Furthermore, it was not considered that the porous body obtained by extracting hot water from a molded product had a sufficient strength as a PBT structure because there were many things whose surface roughness could be visually confirmed. However, since there is a possibility that these can be improved by further increasing the draft angle of the mold runner portion, it was not always possible to determine that the production was impossible. The Gurley value of the obtained porous material varied greatly from 5 to 300 seconds, but this was caused by the fact that the internal column supporting the porous material was broken in the pores because the stirring was slightly intense during hot water extraction. It seems that it was clogged or the pore structure itself was crushed. There was also a slight difference in the way of tightening when the porous plate was tightened and sealed when measuring the air permeability. The air permeability was 5 to 30 seconds in terms of Gurley value for 5 samples that were lightly tightened, and 10 to 50 seconds for 5 samples that were tightly tightened. It was found that the pores were too large, resulting in a brittle sponge-like structure and its collapse. When the shape of the vent plug is a plate, if the stirring is not performed in the hot water extraction process, the plates are likely to overlap each other and cause poor extraction. In anticipation of mass production, they stir vigorously. This is what called partial destruction in this porous body with large air holes. The actual air permeability should be higher than that of Example 1, but is structurally weak. Whether or not it has practicality as a vent plug depends on the shape of the hole, and it can be said that the composition ratio of the glycerin is the upper limit as a recipe.

[Comparative Example 2] (Preparation of PBT porous material)
Except that the initial compound recipe was 45 parts by mass of PBT, 54 parts by mass of pentaerythritol, and 1 part by mass of glycerin, the same experiment as in Example 1 was performed. The Gurley value was 98 seconds on average and the air permeability was low.

[Example 4] (Preparation of PBT porous material)
Except that the initial compound recipe was 25 parts by weight of PBT, 74 parts by weight of pentaerythritol, and 1 part by weight of glycerin, the same experiment as in Example 1 was performed. Somehow a porous material was obtained, but the process was difficult. That is, the extrudate was very fragile, and the product obtained from the pelletizer was excessively crushed, and the powdery product became the majority. Furthermore, at the time of mold release of injection molding, one of the two parts was broken or damaged by the ejector extrusion, and the runner was broken for each molding. These are due to the small amount of polymer composition in the injection. Although it may be possible to improve the injection molding process by changing the mold design, the PBT composition ratio of this recipe is the lower limit in mass production. The Gurley value of the porous body which was free from destruction was 5 to 11 seconds.

[Example 5] (Preparation of PBT porous material)
Except that the initial compound recipe was 25 parts by mass of PBT, 74.5 parts by mass of pentaerythritol, and 0.5 parts by mass of glycerin, the same experiment as in Example 4 was performed. The difficulty of the process was similar to Example 4. The obtained porous body had a Gurley value of 5 to 10 seconds.

[Example 6] (Water repellent solution)
A water repellent solution “SR2406 (manufactured by Dow Corning Toray)” in which a methyl silicone compound was dissolved in toluene was obtained. The solid concentration was 50%. Hexane (manufactured by Showa Chemical Industry Co., Ltd. (Tokyo, Japan)) was added thereto to prepare solutions having solids concentrations of 0.5%, 1%, 2%, and 5%. The names of these water repellent solutions were “SR2406 / 0.5”, “SR2406 / 1”, “SR2406 / 2”, and “SR2406 / 5”, which were applied to each example.

[Example 7] (Dipping and drying: Completion of vent plug)
Eight porous plate-like materials prepared in Example 1 were immersed in the water repellent solution “SR2406 / 0.5” prepared in Example 6 for 1 hour. The liquid was taken out from the liquid, placed on a stainless steel (SUS) net, allowed to stand for several tens of minutes in a fume hood, and then placed in a hot air drier at a temperature of 80 ° C. and dried for 1 hour. The temperature of the hot air dryer was raised to 150 ° C. and left at this temperature for 2 hours. The air permeability and water pressure resistance of this product were measured.

[Examples 8 to 10] (Dipping and drying: Completion of vent plug)
The same experiment as in Example 7 was performed by changing the water repellent solution to “SR2406 / 1” in Example 8, “SR2406 / 2” in Example 9, and “SR2406 / 5” in Example 10. It was.

[Example 11] (Dipping and drying: Completion of vent plug)
Eight porous plate-like materials prepared in Example 2 were immersed in the water repellent solution “SR2406 / 0.5” prepared in Example 6 for 1 hour. The liquid was taken out from the liquid, placed on a stainless steel (SUS) net, allowed to stand for several tens of minutes in a fume hood, and then placed in a hot air drier at a temperature of 80 ° C. and dried for 1 hour. The temperature of the hot air dryer was raised to 150 ° C. and left at this temperature for 2 hours. The air permeability and water pressure resistance of this product were measured.

[Examples 12 to 14] (Dipping and drying: Completion of vent plug)
The water repellent solution was changed to “SR2406 / 1” in Example 12, “SR2406 / 2” in Example 13, and “SR2406 / 5” in Example 14, respectively. It was.

  The measurement results in Examples 7 to 14 are shown in Table 1. All of the air permeability and the water pressure resistance showed extremely excellent values as a vent plug, and were good results.

[Examples 15 to 18] (Durability test of vent plug)
The vent plug-shaped products obtained in Examples 9, 10, 13, and 14 were subjected to 1000 cycles of a thermal shock test at −55 ° C./+100° C., respectively. That is, the temperature is kept at −55 ° C. for 30 minutes, and the temperature is set to + 100 ° C. within 5 minutes for 30 minutes, and then returned to the original −55 ° C. within 5 minutes. This is a temperature shock test. The air permeability and water pressure resistance were measured after this test. The results are shown in Table 2. All the measured values were almost the same as those before the temperature shock test, and the durability of the vent plug against temperature shock could be confirmed.

FIG. 1 is a process schematic diagram of equipment for mass production of a porous body by extracting pentaerythritol from a molded product.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Water tank 2 ... Water tank 3 ... Water tank 4 ... Cooling tank 5 ... Pump 6 ... Supply pipe 7 ... Pipe 8 ... Pipe 9 ... Refrigerant pipe 10 ... Immersion jig

Claims (5)

A compound containing 25 to 40% by mass of polybutylene terephthalate resin, 75 to 60% by mass of pentaerythritol, and 0.25 to 2.5% by mass of a liquid polyfunctional alcohol compound,
This compound is injection-molded, and the vent plug-type injection-molded product obtained by the injection molding is immersed in water to extract alcohols, and then dried to form a porous body.
The porous molded article was produced by immersing the injection-molded product in an organic solvent solution of a methyl silicone polymer compound to adsorb the silicone polymer compound, and then drying and volatilizing the organic solvent. A vent plug characterized by being a thing. A compound preparation step of preparing a compound containing 25 to 40% by mass of polybutylene terephthalate resin, 75 to 60% by mass of pentaerythritol, and 0.25 to 2.5% by mass of a liquid polyfunctional alcohol compound;
A molding step of obtaining an injection-molded product of a vent plug type by injection molding the compound with an injection molding machine,
An extraction step of immersing the injection-molded product in water to extract alcohols and then drying to form a porous body; and
Immersion step of adsorbing the silicone polymer compound by immersing the injection molded article that has become this porous body in an organic solvent solution of a methyl silicone polymer compound;
A drying step of drying the injection-molded product that has undergone the dipping step to volatilize the organic solvent. In the manufacturing method of the vent plug according to claim 2,
The drying step includes a step of fixing the methyl silicone polymer compound by heating the injection molded article to a temperature of 140 ° C. or higher. In the manufacturing method of the vent plug according to claim 2 or 3,
The organic solvent solution has a methyl silicone polymer compound concentration of 0.5% by mass or more. In the manufacturing method of the vent plug as described in 1 selected from Claim 2 thru | or 4,
The method for producing a vent plug, wherein the polyfunctional alcohol compound is glycerin.

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