JPS6349535B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas permeable membrane, in particular a membrane body for oxygen-carbon dioxide gas exchange in an oxygenator;
Membranes for water vapor permeation in devices for obtaining useful water such as drinking water or industrially useful ultrapure water from seawater or other water, and gas selective absorption membranes used in hazardous or polluting gas concentration measuring instruments. The present invention aims to provide a thin film that can be used as a dust-proof protective film for bodies, sensors for combustible and explosive gases, and various similar uses.

Conventionally, thin films used for the above-mentioned purposes include those formed by forming a large number of protrusions on the surface of a silicone thin film (see Japanese Utility Model Publication No. 55-28270), or a large number of thermoplastically formed thin films. A thin film made of a thermoplastic material having a deformed portion and a thin film portion forming the deformed portion being at least partially thinner than the thin film between the deformed portions (see Japanese Patent Publication No. 54-25360), etc. Are known.

However, in the former thin film, the thin film grooves between the protrusions act like a cut-out structure during compression molding, and rupture occurs easily at the grooves along the protrusions. It is difficult for thin films formed from rubber materials to form clear boundaries in the molecular orientation during film formation, but rather the molecular orientation continues from the periphery along the protrusion shape.
The bursting strength simply indicates the bursting strength due to the average thickness including the protrusions. This means that the thickness is 10~
This is considered to be an extremely important issue in the field of handling 300 μm silicone rubber thin films.
It cannot be said that the above-mentioned thin film sufficiently solves these problems.

In addition, the latter thin film has almost the same problem as above, especially in the protruding parts formed by thermoplastic deformation, there is no essential difference in molecular orientation at the boundary between it and the flat part, and the problem is the same as above. It has the problem of being easily ruptured or torn.

Furthermore, both the former and the latter require a complex and high-precision mold that has protrusions or deformed protrusions with correspondingly limited dimensions such as pitch and height in order to form protrusions or deformed parts on the thin film. However, this has the disadvantage of requiring a large amount of money to produce the mold.

The present invention aims to solve the problems of the conventional thin films as described above and to provide a new thin film that eliminates the disadvantages. It is characterized in that fine grains of silicone rubber crosslinked in an oriented state are uniformly dispersed in the shape of projections.

Hereinafter, the gas permeable membrane according to the present invention will be explained in detail based on the accompanying drawings.

1 and 2 illustrate one basic embodiment of the gas permeable membrane according to the present invention, in which 1 is a thin film made of silicone rubber, and 2 is a silicone rubber film constituting the thin film 1. These are protrusions made of fine grains of silicone rubber that are cross-linked in an orientation different from that of rubber.

The silicone rubber constituting the thin film 1 mentioned above may be silicone (raw) rubber, a polymer blend of silicone (raw) rubber and non-silicone rubber or plastic, or a copolymer of silicone and a compound other than silicone. Products made by appropriately blending reinforcing fillers, semi-reinforcing fillers, heat resistant agents, coloring agents, anti-aging agents, antioxidants, and other additives to optionally selected main components. This depends on its composition, curing mechanism, curing method (e.g. atmospheric pressure hot air vulcanization, pressure molding vulcanization, steam vulcanization, hot liquid vulcanization, radiation vulcanization, room temperature vulcanization, etc.) or liquid vulcanization. There are no particular restrictions on the type (one-liquid type, two-liquid type, etc.).

The silicone (raw) rubber mentioned above includes dimethyl silicone rubber, methyl phenyl silicone rubber,
Examples of rubbers or plastics other than silicone (raw) rubber in polymer blends include methyl vinyl silicone rubber, methyl phenyl vinyl silicone rubber, natural rubber, urethane rubber, isoprene rubber, butyl rubber, butadiene rubber, and rubber. Raw rubber, polysulfide rubber,
Acrylic rubber, styrene-butadiene rubber, styrene-propylene rubber, butadiene-acrylonitrile rubber, ethylene-vinyl acetate copolymer, polyethylene, methyl methacrylate, and copolymers such as diorganopolysiloxane.
Examples include polycarbonate block copolymers.

In addition, examples of the above-mentioned reinforcing filler include silica airgel, finely powdered silica, precipitated silica, dry or wet silica such as diatomaceous earth, and examples of the vulcanizing agent include organic peroxides and platinum-based silica. Examples include compounds and sulfur, but it goes without saying that it is desirable to select and use any vulcanizing agent depending on the type of the main component.

The content of the silicone component in the polymer blend is preferably 30% or more, preferably 50% or more, and the silicone content in the copolymer is 30% by mole or more, preferably 50% by mole or more. .

In the present invention, the silicone rubber constituting the thin film 1 has a rubber hardness (JIS K 6301).
It is desirable to use a material that exhibits a value in the range of 10 to 80% and elongation at break of 100 to 700%.

The thickness of this thin film 1 varies slightly depending on the use of the gas permeable membrane according to the present invention, but generally
A range of 10 to 300 μm is sufficient.

Next, fine particles 2 in the gas permeable membrane of the present invention
There is no particular restriction on the silicone rubber constituting the thin film 1, except that it must be crosslinked in an orientation different from that of the film silicone rubber described above. You can use something similar.

The silicone rubber constituting the fine particles 2 may contain a silica-based reinforcing filler as well as any other additives, similar to those constituting the thin film 1 described above, and the fine particles 2 The hardness or elongation at break of No. 2 is also within the same range as the above thin film (rubber hardness (JIS K 6301) 10 to 80.
Preferably 10-60, elongation at break (JIS K 6301)
100-700%). This is because fine particles with a rubber hardness of less than 10 are substantially ineffective, while those with a rubber hardness of more than 80 tend to be easily broken during handling and the thin film itself is easily damaged.

The rubber hardness of the thin film 1 and the fine particles 2 are each within the above-mentioned ranges, but in the present invention, the difference in hardness between them is preferably 60 or less, preferably 50 or less. This makes the permeable membrane even more difficult to tear. Further, although it is preferable that the physical strength of the fine particles 2 be within the above-mentioned range, it goes without saying that it does not necessarily have to have the same physical strength as the thin film 1.

As mentioned above, it is essential that the fine grains 2 are cross-linked with a different molecular orientation from that of the thin film 1. Or, by approximating it, the surface wettability of the fine particles 2 is developed by the silicone rubber that makes up the thin film 1 in contact with it, promoting bridging of the thin film, and increasing the bonding between the thin film and the fine particles. The chemical bond becomes stronger and as a result the fine grains have a reinforcing filler effect. This means that while conventional silicone rubber thin films have the disadvantage of being easily ruptured due to the directional molecular orientation caused by thermoplastic deformation, the permeable membrane of the present invention does not have such disadvantages. There is no Therefore, it is possible to increase the difference in the thickness of the gas body before and after passing through the permeable membrane, and when trying to obtain the same performance as conventional products, it can be made smaller, which is economically advantageous.
In addition, the capacity is significantly greater for products of the same size as conventional products.

In addition, although a rectangular parallelepiped particle is shown as the fine grain 2 in FIG. 1, the shape of this fine grain is shown in FIG.
As shown in f, it may be any of cylinders, prisms, square pyramids, truncated square pyramids, spheres, ellipsoids, and other irregular shapes. These fine grains 2 are required to have a size that allows them to form protrusions on the thin film 1, and generally they are not thick or have a diameter of 1 to 1.
Although it is assumed to be about 3000 μm, the longitudinal direction is not necessarily limited and can be arbitrarily determined depending on the thickness of the thin film 1, etc. Moreover, regarding the particle size distribution of the fine particles 2, those having a wide particle size distribution may be used as long as they satisfy the above-mentioned conditions, and there is no problem even if particles having different shapes are used in combination. Further, the fine particles 2 may be either solid or hollow, or may have a porous structure.

Regarding the relationship between the thickness (t ₁ ) of the thin film 1 and the height (t ₂ ) of the protrusions protruding from this thin film in the gas permeable membrane according to the present invention, the relationship is expressed as protrusion height (t ₂ )/thin film thickness. ( _t1 ) is 0.01~100, preferably 0.05~
50, more preferably in the range of 0.1 to 10, because if the ratio exceeds 100, the thin film 1 will be easily damaged by the force applied to the protrusions during handling, or fluid movement will be impaired near the interface of the thin film. As a result, the efficiency of gas movement within the membrane becomes poor, and conversely, if it becomes smaller than 0.01, the effect obtained by providing the protrusions cannot be achieved.

The dispersion density of the above-mentioned fine particles 2 in the thin film 1 varies slightly depending on the shape and size of the fine particles, as well as the use of the gas permeable membrane according to the present invention. For example, if the fine particles 2 have a diameter of 1 mm, If the membrane is 100 μm thick and has a cylindrical shape with a height of 1 mm, and the use of this permeable membrane is for an oxygenator, ^then the fine particles are
It is desirable to disperse about ×10 ⁴ to 5 × 10 ⁵ pieces.

In addition, the dispersion angle of the fine particles is not limited to being perpendicular to the thin film 1, as long as the thickness of the thin film and the height of the protrusions do not impair the conditions described above. The fine particles 2 may be dispersed in an oblique direction, and the dispersion state of the fine particles 2 in planar observation may be either regular or irregular. From a product management perspective, it is rectangular,
Iris or random shapes are preferred.

Although FIGS. 1 and 2 show examples in which the protrusions 2 are completely exposed, the protrusions 2 may be removed as shown in FIGS. 3 and 4 as long as the effect of providing the protrusions is not impaired. The structure may be such that the surface of the thin film 1 is covered with silicone rubber.

The gas permeable membrane according to the present invention can be applied, for example, to (1) a curable uncrosslinked or semi-crosslinked silicone rubber and/or silicone rubber in a plasticized state; After dispersing quasi-crosslinked or crosslinked fine particles, the uncrosslinked or semi-crosslinked silicone rubber and/or silicone rubber is maintained in a plastic fluid state and preformed into a film shape, and then the preform is crosslinked. or (2) after maintaining a curable uncrosslinked or semi-crosslinked silicone rubber and/or silicone rubber in a plastic fluid state and forming it into a film, the film-like silicone rubber and/or
Alternatively, curable coagulated crosslinked or crosslinked fine particles made of silicone rubber and/or silicone rubber are dispersed in silicone rubber, and then the uncrosslinked or semi-crosslinked film silicone rubber and/or silicone rubber and silicone rubber are dispersed. And/or it can be produced by a method of crosslinking curable coagulated crosslinked fine particles made of silicone rubber.

First, the former method described above will be explained in detail. As a method for dispersing crosslinked or crosslinked fine particles, any method can be adopted depending on the plasticity or viscosity of the above-mentioned silicone material. , Banbury mixer, kneader or other propeller agitator.

The silicone material used in this dispersion process must be plasticized and curable, uncrosslinked or semi-crosslinked, in order to reliably and firmly disperse and integrate the fine particles into the silicone material. It is said that

The above-mentioned fine particles may be of various forms, such as those obtained by cutting or pulverizing a silicone rubber elastic body of any composition into a desired size, or those obtained by granulating an uncrosslinked silicone rubber compound by a known method and then aging it. A silicone rubber composition that is treated to make it into a coagulated and cross-linked state to increase its plasticity or cross-linked, has fluidity at room temperature and contains a curing catalyst (if necessary, a silicone rubber composition that is insoluble in the composition) (using a solvent) to form fine particles, and silicone rubber compositions with fluidity are added to an insoluble heat medium and the composition is cured into fine particles. can be given.

Specifically, after preforming a curable silicone material by the method described above, the cured or uncured curable fine particles described above are added thereto, and then the material is molded according to a conventional method. Curing (corresponding to Figures 1 and 2), and then applying or spraying silicone material as necessary (corresponding to Figures 3 and 4), or preparing by adding fine particles to the silicone material. A method of performing post-molding curing treatment (corresponding to Figures 3 and 4), in which a silicone material containing a curing catalyst is partially cured into a gel state, and then this is formed into a film and cured. Method: Diorganopolysiloxane constituting the silicone material or a material with a high cohesive force as a reinforcing filler is used to create a state with a high degree of partial aggregation (gel) during the kneading process, and a curing catalyst is added to this to form a sheet. A method of forming and curing into a film or a sheet, in which two types of silicone materials with a difference in plasticity measured by a William plasticity meter of 150 or more are mixed to form a gel dispersion, and then formed into a sheet or film. There are various methods, but from the viewpoint of homogeneously mixing fine particles into silicone-based materials, it is best to use them in a gel or slurry form, which does not become a homogeneous solution even if simply diluted.
Specifically, materials that are crosslinked, semi-crosslinked, coagulated crosslinked, in a gel state with developed molecular aggregation, or have a higher degree of plasticity than the above-mentioned silicone materials, and those that have not been crosslinked reliably are used as curing catalysts or It is essential to contain a vulcanizing agent or a crosslinking agent.

As described above, the silicone material with fine particles dispersed therein is preformed into a desired shape, such as a sheet, film, or tube, and this preform is the final product that is intended to be obtained. Depending on the shape of the gas permeable body, an extrusion device equipped with a T-die or a circular die, or other conventionally known devices may be employed.

In the former method, the desired final product is obtained by curing the silicone material constituting the thin film in the preformed product obtained as described above, but this curing can be carried out by any method depending on the composition of the silicone material, etc. For example, if the material is room temperature curable, it can be simply left in the air, or if it is heat curable, hot air, steam, ethylene glycol, glycerin or Curing may be carried out using a heat medium such as a low melting point inorganic salt, heating and pressurizing using an autoclave, press, etc., or further using a heating roll.

In addition, if fine particles that are not completely cured are used, it is necessary to cure them, but this may be done at the same time as the above rubber, or may be done separately. .

Further, after completion of preforming or curing, a silicone sheet or film having a desired composition may be integrated with the surface provided with projections made of fine particles using an adhesive or the like.

Regarding the latter method, for example, after molding a silicone material into a desired shape by an arbitrary method, fine particles are dispersed on the molded product, and then the molded product is cured (if necessary) in the same manner as the former method. The silicone material can be molded by topping it on a flat plate, sheet, or film made of synthetic resin by casting, roll coating, calender roll, etc., or by topping the silicone material on a carrier. It can be sprayed, dipped, etc.

Further, as a method for dispersing the fine particles on the molded product, a method of allowing the fine particles to fall naturally using a sieve, a method of utilizing electrostatic action, etc. are applied. The mechanism by which the fine particles are dispersed in a molded product made of silicone material and form protrusions is that the fine particles extruded from an extrusion nozzle or calendar roll are initially set to have a greater viscosity or elasticity than the rubber material has. It is thought that this is formed elastically due to the thickness of the channel or the gap between the rolls.

By employing the method described above, the silicone material and the fine particles are firmly bonded and integrated, but the fine particles have a unique molecular orientation during the preforming of the rubber material, and this material has a unique molecular orientation. Due to plastic flow, the molecular orientation does not become the same, and the rubber material is evenly dispersed on a molded article made of the rubber material by physical flow or other physical methods.

Fine grains made of silicone material have affinity at the interface with the silicone material constituting the thin film, so during crosslinking or vulcanization, molecules cohere well at the interface of the fine grains, resulting in an adhesive reaction due to crosslinking or vulcanization. Alternatively, a strong bond or crosslink can be obtained near the interface.

As explained above, the gas permeable membrane according to the present invention has extremely high gas permeability, and the permeable membrane also has excellent physical strength such as tearing and tensile strength even near the formation of protrusions, and has good durability. Therefore, even if the gas passing through it has a large mechanical pressure, its function will not be easily impaired, and furthermore, the fine particles forming the protrusions can be made of any material. Therefore, it can be widely applied to medical applications that are applied directly to the human body, as well as industrial applications such as measuring the concentration of pollutant gases.

Furthermore, the permeable membrane has the advantage that it can be produced very easily without using complicated molds or other equipment as in conventional methods.

[Brief explanation of the drawing]

Figures 1 to 3 are cross-sectional views showing basic aspects of the gas permeable membrane according to the present invention, Figure 4 is a cutaway perspective view showing another aspect of the gas permeable membrane, and Figure 5 is a perspective view of fine particles. It is. 1...Thin film made of silicone rubber, 2...Protrusions made of fine particles.

Claims (1)

[Claims] 1. A gas permeable membrane having protrusions on its surface, characterized in that fine particles of silicone rubber crosslinked in a different orientation are uniformly dispersed in protrusions along the surface of a membrane-like silicone rubber.