JPH078725A - Filter - Google Patents

Abstract

PURPOSE:To obtain a filter wherein the transmission pores of a porous member are formed into a smaller pore size by forming a vapor deposition film composed of a specific polymeric substance on the surface of the porous member having fine transmission pores. CONSTITUTION:Poly-p-xylylene being a specific polymeric substance is deposited on the surface of a porous member under specific thermal vapor deposition conditions to form a filter whose pore size is uniformly contracted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous filter useful in the fields of manufacturing electric / electronic parts vapor-deposited with polyparaxylylene, medical treatment, and food.

[0002]

2. Description of the Related Art Porous filters are used in various fields for removing fine solids. For example, it is used for purification of ultrapure water and chemicals for semiconductor production, removal of yeast in beer and wine, and production of pyrogen-free water.

Although there are many characteristics required for filters used for these applications, it is important to control the pore size corresponding to the size of the sieve in order to carry out the intended substance removal. Therefore, techniques for controlling the pore size of these filters have been studied conventionally. These are roughly classified into a method of controlling the pore size by using a special method at the time of producing the filter and a method of performing some processing after producing the filter.

Regarding the one in which the pore size is controlled by controlling the production conditions during the production of the filter, for example, in Japanese Patent Laid-Open No. 63-145345, a polyacrylonitrile-made porous body by a phase inversion method is used to control the liquid temperature. It is described that the pore size is controlled by doing so.

Further, Japanese Patent Application Laid-Open No. 2-180940 describes a method for producing a porous body by precipitating fine crystals or spherulites of a thermoplastic resin in an organic solvent to carry out cross-linking fusion between particles. , Type of organic solvent, molecular weight of raw polymer,
The pore size is controlled by controlling the polymer concentration in the solution.

Further, in JP-A-2-271976,
The pore diameter is controlled by preliminarily blending crystallized glass having a dense structure when sintered and ceramic powder having a porous structure.

On the other hand, as a method for controlling the pore size by subjecting the surface of the porous filter to a vapor deposition treatment, for example, JP-A-62-2 is used.
No. 70473 describes a method of controlling a pore size on a surface of ceramic or metal by a vacuum vapor deposition method, a physical vapor deposition method such as a sputtering method and an ion chemical vapor deposition method, and a chemical vapor deposition method such as a CVD method and a plasma CVD method. .

Further, in JP-A-4-104822, one component of a two-component gas that produces a solid by mixing and reacting is made to flow from both sides of a porous body to form a thin film on the surface of a substrate to control the pore diameter. It is described that

Further, it is described in JP-A-1-224325 that the pore size is controlled to be reduced by compressing a porous filter.

[0010]

Problems to be Solved by the Invention One of the problems with the above-mentioned treatment methods at the time of producing a filter is that they are not versatile because of their limited materials. For example, in JP-A-63-145345, it is necessary to select an appropriate solvent / coagulation bath for the filter material to be produced.
Further, Japanese Patent Laid-Open No. 2-271976 is limited to ceramics and is not applicable to polymer materials. Moreover,
In JP-A-64-344078, since a strong acid is used to remove the fiber-forming polymer, the filter material must be able to withstand the strong acid.

Regarding the method of performing some treatment after the filter is manufactured, for example, in the method of JP-A-62-270473, as shown in FIG. 1, there is a difference in the vapor deposition amount between the front surface portion and the side surface portion of the porous body. A thick film cannot be avoided. Increasing the film thickness of the filter leads to a decrease in filtration speed, which is a practical problem.

Further, the method disclosed in Japanese Patent Laid-Open No. 4-104822 requires heating during vapor deposition, and is not suitable for materials having low heat resistance.

Further, in JP-A-1-224325, only a filter having a pore size calculated from the bubble point of 7 μm or more can be produced, and the controllable pore size is limited.

[0014]

In order to solve the above problems, the inventors have invented a pore size control method for reducing the pore size by depositing polyparaxylylene on a porous filter which can be stored in a dry state. .

[0015]

DETAILED DESCRIPTION OF THE INVENTION Some porous filters become more difficult to stably exist as the pore size becomes smaller. Therefore,
In the case of a filter having a small pore size, in order to maintain the stability of the pores, it may be stored in a wet state or a state in which oils and fats such as glycerin are applied. In such a case, vapor deposition of polyparaxylylene is hindered, which is not preferable.

The porous filter used in the present invention is
Any material that can be stored in a dried state other than the above-mentioned wet state can be used. In general, polyparaxylylene is vapor-deposited on any material, so that pore diameter can be controlled by vapor-depositing it on filters made of various materials without considering heat resistance and chemical resistance. As the material of these filters, for example, cellulose acetate, nitrocellulose, polyvinylidene fluoride, polytetrafluoroethylene, nylon, glass fiber, stainless steel, alumina, silica and the like can be used.

The polyparaxylylene used in the present invention is the polymer shown in Chemical formula 1.

[0018]

[Chemical 1]

Of these polyparaxylylenes, those shown in Chemical formula 2 are particularly preferable.

[0020]

[Chemical 2]

Polyparaxylylene is usually dissociated from paraxylylene dimers into sublimation monomer radicals.
After being condensed on a porous filter and polymerized, it is deposited on various substrates. The reaction conditions are usually as follows. Trueness: 1.3 × 10 ⁻² to 133 Pa
{10 ⁻⁴ to 1 Torr} Sublimation temperature:
100 to 200 ° C Pyrolysis temperature: 400 to 700 ° C Condensation polymerization temperature: 250 ° C or less

The above-mentioned value is practical for the degree of vacuum, but if necessary, an inert gas atmosphere of nitrogen, helium, argon or the like may be used instead of reducing the pressure.

Regarding the sublimation temperature, paraxylylene dimer does not sublime at 100 ° C. or lower. Further, at a temperature of 200 ° C. or higher, the concentration of the para-xylylene dimer that evaporates becomes abnormally high, or air leaks into the reduced pressure system to make the para-xylylene film brittle. Although these sublimation steps are not always necessary, direct thermal decomposition causes local heating and deterioration of the dimer to effectively prevent decomposition into monomer radicals. Therefore, it is preferable to include a sublimation step.

When the thermal decomposition temperature is 400 ° C. or lower, the paraxylylene dimer does not decompose. Further, at 700 ° C. or higher, the substituent in the dimer decomposes and the desired polymer cannot be obtained.

Condensation of paraxylylene monomer radicals occurs below 250 ° C. and condenses even at room temperature. Therefore, it is not necessary to heat the material to be vapor-deposited, and the condensed monomer radicals are continuously polymerized to form a film.

In the vapor deposition step, a thin film is uniformly formed on the front surface and the side surface of the porous body as shown in the cross section of FIG. 2, so that the pore diameter can be easily controlled and the film thickness should be made thicker than necessary. Without reducing the hole diameter. Further, the amount of vapor deposition is affected by sublimation temperature, condensation polymerization temperature, etc., but is particularly affected by the amount of paraxylylene dimer, so that it can be adjusted to a desired pore size by appropriately adjusting the amount of dimer. is there.

[0027]

【Example】

Examples 1 and 2 Polyparaxylylene was vapor-deposited on the various filters shown in Table 1 under the vapor deposition conditions described below.

[0028]

[Table 1]

Deposition conditions: Vapor: 1.3 Pa {10 ⁻² Torr) Sublimation temperature: 120 ° C. Pyrolysis temperature: 690 ° C. Condensation polymerization temperature: Room temperature Polymer structure: ONo. V dimer amount: described in Table 2

The test results are shown in Table 2 below.

[0031]

[Table 2]

The evaluation items in Table 2 are as follows. [Observation of cross-sectional structure] After vapor deposition, the cross-sectional structure of the filter was observed using SEM. In the table, ◯: The filter is uniformly deposited on the front and side surfaces of the filter, and is deposited over the entire filter. X: No uniform thin film was formed [Change in film thickness] The change in film thickness was measured from the SEM cross-sectional photograph. [Change in Pore Size] The maximum pore size was measured by the method described in ASTM F316-86 (bubble point method).

Examples 3 to 6 A polyparaxylylene vapor deposition film was formed on the cellulose ester circular flat membrane filter having a diameter of 47 mm used in Example 1 under the following vapor deposition conditions by changing the amount of raw material dimer. .

Deposition conditions: Vapority: 1.3 Pa (10 ⁻² Torr) Sublimation temperature: 120 ° C. Pyrolysis temperature: 690 ° C. Condensation polymerization temperature: Room temperature Polymer structure: No. 5 Dimer amount: As shown in Table 3

The results are shown in Table 3.

[0036]

[Table 3]

INDUSTRIAL APPLICABILITY In the present invention, the pore size can be easily reduced by vapor-depositing polyparaxylylene on a porous filter which does not require storage in a wet state or a state in which oils and fats such as glycerin are applied. it can. Further, since the film thickness of the polyparaxylylene deposited on the adhered surface of the porous filter is uniform, it is possible to secure a uniform and stable pore size by controlling the deposition amount.

[Brief description of drawings]

FIG. 1 is a schematic enlarged cross-sectional view of a surface layer of a porous body according to a conventional processing method.

FIG. 2 is a schematic enlarged cross-sectional view of a surface layer of a porous body according to the present invention.

FIG. 3 is a schematic cross-sectional view of a porous body according to the present invention.

[Explanation of symbols]

 1 Porous Body Passage 2 Porous Body 3a, 3b Coating Layer on the Surface of Porous Body

Claims (1)

[Claims] 1. A filter characterized by depositing polyparaxylylene on the surface of a porous filter.