JPH1157377A - Adsorbent-encapsulating porous vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adsorbent-encapsulating porous vessel capable of avoiding the scattering of fine powder of an adsorbent to the outside environment and exhibiting excellent adsorption performance. SOLUTION: The adsorbent-encapsulating porous vessel is obtained by laminating 2 pieces of polytetrafluoroethylene porous sheets having >=5000 g/m<2> /day moisture permeability, 0.1-0.15 μm particle diameter and >=99.999% collection efficiency of dust and sealing the end part of the sheets so as to wrap the adsorbent inserted between the sheets.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adsorbent-containing porous container using a polytetrafluoroethylene porous membrane.

[0002]

2. Description of the Related Art Recently, hard disk drives for computers have been reduced in size and capacity. Along with this, it is desired to improve the reliability of the hard disk drive. The causes of the loss of reliability include damage to the disk drive head due to internal fine particles and contamination of the disk surface with organic vapor.

As a means for solving this problem, it is known to use an adsorbent for adsorbing and removing gaseous impurities in the atmosphere in a porous container. In general, as the surface area of the adsorbent increases, the adsorption efficiency increases, and therefore, fine particles having a small particle size are used as the adsorbent.
In addition, fine dust is generated due to the contact between the internal adsorbents. In order to prevent contamination of the external environment due to scattering of these fine particles and dust, it is necessary for the container that contains the adsorbent to be devised so as not to release the fine particles and dust of the adsorbent to the outside.

In a porous container using a nonwoven fabric, a mesh, or the like, the coarse particles are large (the pore diameter is large), so that the fine particles inside the container are scattered to the outside through the container. In contrast, Tokuhei 7
Japanese Patent Application Publication No. 114911 discloses a porous container using a polytetrafluoroethylene (hereinafter, referred to as "PTFE") porous tube having an average pore diameter of 0.1 to 1 [mu] m. Higher rejection of fine particles is realized.

[0005]

However, the PTFE porous tube has a thickness of 0.254 to 1.2.
7mm thick and the porosity is as small as 70% or less,
It is difficult to transmit external gaseous impurities. Therefore, there is a problem that diffusion of the gaseous impurities into the container and adsorption to the adsorbent hardly occur, and sufficient adsorption performance cannot be exhibited.

Accordingly, the present invention provides a container containing an adsorbent, which has excellent adsorption performance and which substantially prevents scattering of adsorbent fine particles to the outside. The purpose is to:

[0007]

In order to achieve the above object, an adsorbent-containing porous container according to the present invention comprises an adsorbent and a polytetrafluoroethylene porous membrane containing the adsorbent. A porous container, wherein the polytetrafluoroethylene porous membrane has a moisture permeability of 5000 g /
m ² / day or more, and the particle size is 0.1 μm to 0.1 μm.
It has a characteristic that the dust collection efficiency of 15 μm is 99.999% or more. With such a configuration, since fine powder and dust are not substantially transmitted, external environmental pollution due to scattering of the adsorbent can be reduced. In addition, it is possible to sufficiently guarantee that the gaseous substance permeates through the porous container and diffuses into the container, thereby exhibiting excellent adsorption performance.

Here, the collection efficiency is as follows, except that the particle size of the particle to be measured is 0.1 to 0.15 μm.
It is a value measured by a method similar to the method described in JIS K3803.

Further, in the adsorbent-containing porous container of the present invention, the adsorbent is contained in a container formed by sealing the ends of a pair of superposed porous PTFE membranes. Preferably, the adsorbent is silica gel, activated carbon or a mixture thereof.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The material constituting the porous container of the present invention has a dust collection efficiency of 99.999% or more with a particle diameter of 0.1 to 0.15 μm and a moisture permeability of 5000.
A PTFE porous membrane having a g / m ² / day or more is used.

An example of a method for producing such a porous PTFE membrane will be briefly described. First, a paste-like mixture obtained by adding a lubricant to PTFE fine powder is preformed. The lubricant is not particularly limited as long as it can wet the PTFE surface and can be removed by a method such as extraction or heating, and petroleum hydrocarbons such as naphtha having a melting point of about 100 to 140 ° C. are frequently used. The amount of lubricant added is
About 20 to 30 parts by weight is appropriate for 100 parts by weight of PTFE. The preforming is performed at such a pressure that the lubricant is not squeezed out.

The preformed body is formed into a sheet or tube by paste extrusion or rolling, and the PTFE formed body is stretched in at least one direction to obtain a porous membrane.
Stretching is preferably performed after removing the lubricant.

In a porous membrane, the gas permeability is mainly determined by the film thickness and the porosity. To improve the moisture permeability, the film thickness may be reduced and the porosity may be increased. On the other hand, the collection efficiency is determined by the pore size of the pores, and the smaller the pore size, the higher the collection efficiency. This film thickness, pore size and porosity can be adjusted by the stretching ratio,
If the stretching ratio is excessively increased for the purpose of improving the porosity, the pore diameter increases, and it becomes difficult to improve both the moisture permeability and the collection efficiency. Therefore, the stretching ratio is preferably about 20 to 50 times in the case of uniaxial stretching. Further, when the stretching is performed in the biaxial direction, fibrillation proceeds effectively and a fine fiber structure is obtained, so that the porosity can be improved without increasing the pore diameter. Therefore, the stretching is preferably performed in the biaxial direction. At this time, the stretching ratio is 5 to 1 in area ratio.
About 00 times is appropriate.

The stretching temperature is not particularly limited, but is preferably not lower than the melting point of PTFE, that is, not lower than 327 ° C.

The porous PTFE membrane obtained as described above has high moisture permeability and collection efficiency as described above, and preferably has a thickness of 5 to 100 μm and an average pore diameter of 0.5. １．５1.5 μm, porosity is 60-95%.

The above-mentioned PTFE porous membrane may be used alone, but may be used by laminating a PTFE porous membrane and a reinforcing material in order to improve the strength. As reinforcement,
A porous material having a large pore diameter such as a nonwoven fabric or a mesh can be used. Examples of the material of the reinforcing material include polyolefins such as polyethylene and polypropylene, nylon, polyester, and composites thereof. However, it is necessary to consider that the film thickness increases due to the lamination, which may adversely affect the adsorption performance.

The above-mentioned PTFE porous membrane or PTFE
A container containing an adsorbent is prepared using a laminate of a porous membrane and a reinforcing material. The shape and dimensions of the container are not particularly limited as long as the container can substantially seal the adsorbent therein. As an example of the shape, two sheets of a porous material in a sheet form are stacked, and the ends of the sheets are sealed so as to enclose the adsorbent sandwiched between the sheets, as shown in FIGS. 1 to 3. No. As a method for sealing the sheet, a method in which a porous material is directly hot-melt bonded, or a method in which a PTFE copolymer such as polyethylene or a tetrafluoroethylene / perfluoroalkylvinyl ether copolymer is used as an adhesive and heated and pressed. A bonding method or the like can be used.

The adsorbent used in the present invention includes:
In addition to the above-mentioned activated carbon and silica gel, activated alumina, calcium sulfate or calcium carbonate can be used.

[0019]

The present invention will be described below with reference to examples. The characteristics of the porous membrane and the porous container produced in the following examples were evaluated by the following methods.

(Collection efficiency) The porous material was set in a circular holder having a predetermined area, and the permeation flow rate of the porous material was set to 5.3.
cm / sec, and polydispersion-type dioctyl phthalate (DOP) was flowed to the upstream side so that the particle concentration of 0.1 μm to 0.15 μm was about 10 ⁷ particles / liter, and the porous material was permeated. The particle concentration on the downstream side was measured by a particle counter, and the collection efficiency was determined by the following equation (1).

Collection efficiency (%) = {1− (downstream concentration / upstream concentration)} × 100 (1) (However, particles to be measured have a particle diameter of 0.1 μm to 0.15.
It is in the range of μm. )

(Moisture Permeability) A porous container in which an adsorbent, which has been sufficiently dried in advance, is sealed, is charged at a relative humidity of 90% RH and a temperature of 4%.
Leave in a thermo-hygrostat at 0 ° C. and remove after 24 hours. The moisture permeability was determined from the weight before and after the introduction into the thermo-hygrostat by the following equation (2).

Water vapor transmission rate (g / m ² / day) = {(weight after charging−weight before charging) / surface area of porous container / time of charging (days)} (2)

(Example 1) 25 parts by weight of a liquid lubricant (liquid paraffin) was uniformly mixed with 100 parts by weight of PTFE fine powder (trade name: "Fluon CD-123", manufactured by Asahi ICI Fluoropolymers Co., Ltd.). . This mixture was preformed under the condition of 20 kg / cm ² , then extruded into a rod shape, and the rod shape was passed between a pair of metal rolling rolls to form a long 0.2 mm thick sheet. A sheet-shaped molded body was obtained. Next, the liquid lubricant was removed from the sheet-like molded body by an extraction method using trichlene (trichloroethylene), and then wound around a tubular core body in a roll shape. This sheet-like molded product was stretched 15 times in the longitudinal direction at 370 ° C. by a roll stretching method. Next, the sheet-shaped PTFE molded article was stretched three times in the width direction at 100 ° C. using a tenter to obtain a PTFE porous membrane. next,
The two porous PTFE membranes are superimposed, and the four sides are pressure-bonded at 400 ° C. so as to encapsulate silica gel.
mm, and a porous container having an effective surface area of 35 cm ² was obtained. FIG. 1 shows a cross section of the porous container.

(Example 2) PTFE produced in Example 1
A porous film was heat-laminated with a spunbonded nonwoven fabric (trade name: Elves, manufactured by Unitika Ltd.) formed of a composite fiber having a core / sheath structure of polyester / polyethylene to obtain a porous material. Two sheets of this porous material are laminated with the non-woven fabric side facing inward, and the four sides are pressure-bonded at 200 ° C. so as to encapsulate silica gel, and a porous sheet having a side of 50 mm and an effective surface area of 35 cm ² A quality container was obtained. FIG. 2 shows a cross section of the porous container.

(Example 3) 25 parts by weight of a liquid lubricant (liquid paraffin) was uniformly mixed with 100 parts by weight of PTFE fine powder (trade name "Fluon CD-123", manufactured by Asahi ICI Fluoropolymers Co., Ltd.). . This mixture was preformed under the condition of 20 kg / cm ² , then extruded into a rod shape, and the rod shape was passed between a pair of metal rolling rolls to form a long 0.2 mm thick sheet. A sheet-shaped molded body was obtained. Next, after removing the liquid lubricant from the sheet-like molded body by an extraction method using trichlene, the sheet-like molded body was wound around a tubular core in a roll shape. This sheet-like molded product is rolled at 370 ° C. in the longitudinal direction at 370 ° C.
It was stretched 0 times to obtain a PTFE porous membrane. Next, this PTF
Two porous membranes were superposed and pressure-bonded at 400 ° C. on the four sides so as to encapsulate silica gel to obtain a porous container having a side of 50 mm and an effective surface area of 35 cm ² .

(Comparative Example) 18 parts by weight of a liquid lubricant (naphtha) was uniformly mixed with 100 parts by weight of PTFE fine powder (trade name "Fluon CD-123", manufactured by Asahi ICI Fluoropolymers Co., Ltd.). 20 kg of mixture
/ Cm ² and then extruded into a tube. The tubular material was dried by heating to remove the liquid lubricant, and then stretched 6 times in the longitudinal direction at 250 ° C. to obtain a PTFE porous tube. The outer diameter of this porous tube was 5 mm, and the wall thickness was 450 μm. Next, silica gel was sealed in the porous PTFE tube, and both ends of the tube were adhered under pressure at 400 ° C. to obtain a porous container having a length of 50 mm and an effective surface area of 7 cm ² .

Table 1 shows the characteristics of the porous membranes and porous containers prepared in Examples 1 to 3 and Comparative Example.

[0029]

[Table 1] PTFE film thickness Porosity Collection efficiency Moisture permeability (μm) (%) (%) (g / m ² / day) Example 1 50 88 99.9998 9200 Example 2 50 87 99.9999 8500 Example 3 70 75 99.9993 6000 Comparative example 450 65 99.996 4500

[0030]

As described above, according to the porous container enclosing the adsorbent of the present invention, the adsorbent is wrapped in a porous film having excellent dust collection efficiency and moisture permeability, so that the adsorbent is present in the container. Does not substantially pass through the adsorbent particles
External environmental pollution due to scattering can be reduced, while sufficient permeation of gaseous substances is ensured, and it has excellent adsorption performance.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an adsorbent-containing porous container according to Examples 1 and 3.

FIG. 2 is a cross-sectional view of an adsorbent-containing porous container according to Example 2.

FIG. 3 is a view showing an example of the shape of a porous container containing an adsorbent of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 PTFE porous membrane 2 Silica gel 3 Nonwoven fabric 4 Sealed part of PTFE porous membrane

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Koji Ota 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation

Claims (3)

[Claims] 1. A porous container containing an adsorbent and a polytetrafluoroethylene porous membrane containing the adsorbent, wherein the polytetrafluoroethylene porous membrane has a moisture permeability of 5000 g / and in m ² / day or more, and, the adsorbent containing a porous container which is characterized by having the property that the collection efficiency of the dust particle size is 0.1μm~0.15μm is 99.999% or more . 2. The adsorbent-containing porous material according to claim 1, wherein the adsorbent is contained in a container formed by sealing the ends of a pair of superposed porous sheets of polytetrafluoroethylene. Quality container. 3. The adsorbent according to claim 1, comprising at least one selected from silica gel and activated carbon.
4. The porous container containing an adsorbent according to 4.