JPH03262571A - Method for coating gas permeable porous body with resin - Google Patents

Abstract

PURPOSE:To form a resin film enhanced in bond strength by bringing a part of the surface of a gas permeable porous body into contact with a fluid having a powdery resin dispersed therein to accumulate the powdery resin on the contact surface with the fluid by pressure difference and heating the accumulated film layer to fix the same to the porous body. CONSTITUTION:A part of the surface of a gas permeable porous body is brought into contact with a fluid having a powdery resin (e.g. fluoroplastics) dispersed therein to generate pressure difference between the contact surface with the fluid of the porous body and the other surface thereof. The medium constituting the fluid is allowed to flow from the contact surface with the fluid of the porous body to the other surface thereof by this pressure difference to accumulate the powdery resin on the contact surface with the fluid and the surface layer part thereof. If necessary, drying treatment is applied to the gas permeable porous body to heat the formed accumulated film layer along with the gas permeable porous body and the accumulated film layer is sintered to be fixed to the porous body. By this omitted process, the resin film enhanced in bond strength can be formed to a part of the surface of the air permeable porous body. Further, the thickness of the resin film and the flow resistance of the porous body can be altered to a large extent by the simple alteration of a condition.

Description

Detailed Description of the Invention [Industrial Application Field 1] The present invention relates to a method for coating an air-permeable porous body with a resin, and more specifically, a method for coating a part of the surface of an air-permeable porous body with a resin using a powdered resin. Regarding the method.

[Prior Art] Conventionally, fluororesins have been used to coat other substances, such as metal materials, but it is a well-known fact that fluororesins have difficulty adhering to other substances. To solve this problem, it is common practice to apply a primer before applying the fluororesin. Others■Special Public Service 1986-11
No. 108 describes a method in which fluororesin powder maintained at a low temperature is introduced into the cracks of the metal surface layer, and then the temperature is returned to normal and fixed by thermal expansion of the powder. A method has been proposed in which a mixture of powder and metal or ceramic powder is collided with a metal surface to force the powder into the crevices of the metal surface and fix it.

[Problems to be solved by the invention] However, method (2) requires the steps of primer coating, drying, and baking prior to coating with fluororesin in order to improve adhesion to the substrate material, making the process complicated. It is. In method (2), it is difficult to fill the cracks of the substrate material with powder at a high density, and the powder is fixed in the cracks by fitting due to thermal expansion of the powder, so depending on the purpose of use, The adhesion strength of the powder may be insufficient. In method (2), when filling the cracks of the substrate material with powder at a high density, it is necessary to increase the speed at which the mixture of resin powder and metal or ceramic powder collides with the metal surface. Causes scratches such as nicks. There were problems such as.

[Means for Solving the Problems] The present inventor has arrived at the present invention as a result of intensive research to develop a resin coating method that does not have the above problems and has high adhesion strength in an omitted step. .

That is, in the present invention, a part of the surface of an air-permeable porous body is brought into contact with a fluid in which powdered resin is dispersed, a pressure difference is created between the fluid contact surface and other surfaces of the porous body, and this pressure is Powdered resin is deposited on the fluid contact surface and its surface layer by flowing the medium that makes up the fluid from the fluid contact surface side to the other surface, and if necessary, a drying process is performed. This is a method for coating an air-permeable porous body with a resin, which is characterized by heating the laminated film together with the air-permeable porous body, sintering it, and fixing it to the porous body.

The powdered resin used in the present invention is a sinterable powdered resin, such as a fluorine-based, acrylic-based, polyester-based, or polyolefin-based resin, and has an average particle size of Oj to 200μ.
Preferred examples include powders of m. Among these, fluororesin powder is particularly preferred, as it is technically difficult or involves complicated processes in conventional coating methods.

The gas permeable porous body in the present invention is made of a material that does not deform at the sintering temperature of the powdered resin, such as stainless steel.

It is a porous body made of nickel, ceramic, etc.

The porous body can be manufactured by, for example, sintering a metal powder such as stainless steel or nickel, an aggregate of metal fibers, or a ceramic powder. The porous body may be a single layer structure,
Alternatively, a laminated structure consisting of a plurality of layers having different average pore diameters may be used. The average pore diameter of the porous body is preferably 1 to 200 μm.

However, in the case of a laminated structure, this average pore diameter should be understood as the average pore diameter in the layer with the smallest pore diameter. The air permeability of a porous body is determined by the flow characteristics of air at 25°C, 1,
It is preferable that the pressure loss of the porous body at an air flow rate of 11/min/cd is 1 to 5000 mmH20 of water column.

In the present invention, the medium for dispersing the powdered resin is
Either gas or liquid may be used, depending on workability.

Air or water is convenient from an economic point of view. When using water, add a small amount of a surfactant or a thickener such as high molecular weight polyvinyl alcohol to improve the dispersibility of the powdered resin or to prevent damage to the powder deposit layer formed on the substrate. is valid. In addition, when forming a deposited layer of powder using air as a medium, in order to stabilize the deposited layer coating, a method such as preheating the porous body to a temperature at which the powder starts to stick slightly is recommended. It is valid. To create a pressure difference between the fluid contact surface of a porous body and other surfaces, such as the outer surface and the inner surface, a method is used in which one surface is reduced in pressure, the other surface is pressurized, or a combination thereof. Although it is possible, the reduced pressure method is practically advantageous.

Next, if the powder deposited layer coating is formed by a wet method, the deposited layer coating and the porous body are dried in advance, or if they are formed by a dry method, they are directly subjected to a sintering treatment.

The sintering conditions, such as the sintering temperature for 2 hours, are related to the thermal properties of the powdered resin and the air flow characteristics of the product after sintering, and are therefore preferably determined experimentally in advance.

A feature of the present invention is that a resin coating with high adhesive strength is selectively formed on some surfaces of the porous body. In order to do this, it is necessary to selectively attach the powdered resin near the surface of the porous body on the side where the coating is to be formed. The combination of average pore size and average particle size of the powder is important. Generally, the average particle size of the powder is 115% of the average pore size of the porous body.
~1 is convenient. However, the pore shape of the porous body, such as smooth pores made by sintering spherical powder, or pores with many protrusions made by sintering irregularly shaped powder with many protrusions, depends on the sintering material, its shape, and the sintering conditions, e.g. Sintering temperature.

Pore formation and pore size distribution vary significantly depending on time, etc., and as a result, the characteristics of the porous body that traps the powder that forms the coating change. In addition, since the adhesion situation of the powder changes depending on the shape and particle size distribution of the film-forming powder, it is preferable to find the optimal combination of the porous body and the film-forming powder through experiments in advance.

One simple and reliable means of forming a selective coating on one side of a porous body is to make the porous body a multilayer structure, and to make the structure of the side on which the coating is formed to have a structure with high powder trapping performance. It is.

Depending on the filling conditions of the film-forming powder into the porous body or the subsequent sintering conditions, the air flow characteristics of the coated substrate can be significantly changed.

Another feature of the present invention is that by taking advantage of the fact that the substrate material is an air-permeable porous body, the coating provides new surface properties different from those of the substrate material.

By passing gas or liquid through the substrate, new functions can be added to the substrate. This can be expected to have a wide range of applications. For example, it has been conventionally practiced to coat a sheet contacting member with a fluororesin material in an apparatus for transferring an adhesive sheet material to the next process.

However, due to insufficient mold releasability, it may not be possible to peel off the sheet evenly and smoothly when transferring to the next process, resulting in localized stress unevenness on the sheet and making it impossible to manufacture a uniform product. Using an air-permeable fluororesin coated member manufactured by
If pneumatic pressure is applied from the uncoated surface, this problem can be solved and the adhesive sheet can be peeled off evenly and smoothly.

L Example] Next, the present invention will be specifically explained with reference to Examples.

Note that parts in the examples mean parts by weight.

Example 1 An average pore diameter of 45 μm made by sintering stainless steel powder,
The covered body is a cylindrical body with an air permeable porous body with an air flow resistance of 55 mmH and +O, and an outer diameter of 60 m and a length of 150 mm. One end of this is sealed, and the other end is connected to a pressure reducing device via a hose. Connected.

0.03 parts of fluorosurfactant in 100 parts of water, 0.03 parts of fluorosurfactant, 0.
0.05 parts of high molecular weight polyvinyl alcohol was dissolved, and in the solution was added 3 ethylene fluoride resin powder with an average particle size of about 20 μm.
of the mixture was added and uniformly dispersed using ultrasonic waves to form a slurry.

The object to be coated is placed in the slurry and vacuumed for about 5 minutes to form a deposited layer coating on the outer surface of the porous object, and then air-dried for 3 minutes.
The fluororesin is baked by placing it in a heating furnace at 70°C for 30 minutes.
It was fixed to a porous body.

The obtained resin coating had a uniform fluororesin film formed on its outer surface, and even though the coating surface was scratched by applying a load to the tip of a needle, the coating hardly peeled off and remained firmly adhered to the substrate. was.

Furthermore, as a result of cutting the resin coating and observing its cross section under a microscope, it was found that the fluororesin was dispersed from the surface of the porous body to the inside (surface layer).
The reason for the high adhesion strength of the resin-coated body obtained by the present invention was understood.

The film thickness of the resin coating of this example was approximately 80 μm, and the air flow resistance was 450 nwnH20.

Example 2 The same procedure as in Example 1 was carried out except that the suction time for placing the object to be coated in the slurry and forming the deposited layer coating was extended to 40 minutes.

The obtained resin coating has a dense coating with a film thickness of 250 μm, and an air flow resistance of 0.1 fJ /min /c
It was 10001111IH20 or higher under the conditions of J. That is, by changing the slurry suction conditions, it was possible to significantly change the film thickness and flow resistance.

[Effects of the Invention] According to the present invention, a resin coating with high adhesion strength can be formed on a part of the surface of an air-permeable porous body through an omitted step. Furthermore, the thickness of the resin film and the flow resistance of the porous body can be significantly changed by simply changing the conditions.

Claims (1)

[Claims] 1. A part of the surface of an air-permeable porous body is brought into contact with a fluid in which powdered resin is dispersed, a pressure difference is created between the fluid contact surface and another surface of the porous body, and this Depositing powdered resin on the fluid contact surface and its surface layer by causing the medium constituting the fluid to flow from the fluid contact surface side to the other surface side due to a pressure difference,
A method for coating an air-permeable porous body with a resin, which comprises performing a drying treatment if necessary, heating the formed laminated film together with the air-permeable porous body, and sintering and fixing it to the porous body. 2. The method according to claim 1, wherein the powdered resin is a powdered fluororesin.