JP2932611B2 - Polytetrafluoroethylene resin porous tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a high-performance porous tube of ethylene tetrafluoride resin used for a separation membrane, an artificial blood vessel, a catheter, an incubator, and the like. The present invention relates to an integrally molded porous ethylene tetrafluoride tube having a multilayer structure of two or more layers having different pore diameters, porosity or fiber length.

[Conventional technology]

BACKGROUND ART Polytetrafluoroethylene resin porous tubes are used in various applications such as separation membranes, artificial blood vessels, catheters, and incubators.

This porous tetrafluoroethylene resin tube is usually mixed with a liquid lubricant in a fine powder of tetrafluoroethylene resin as a raw material, compacted into a cylindrical shape by pre-molding, and then extruded into a tube-like paste. It is manufactured by a method in which an extruded product is stretched in the longitudinal direction to be porous, and then fired. Porosity can be obtained by a method other than the stretching method, such as extraction of a pore-forming agent or foaming with a foaming agent, or a combination of two or more of these methods.

By the way, a porous tube of ethylene tetrafluoride resin is required to have desired average pore diameter, transmittance, permeation flow rate, strength and the like according to various uses. However, it is extremely difficult or practically impossible to improve a specific function without reducing the strength and other functions of the porous tube by the conventional manufacturing method.

For example, in the case of using a tetrafluoroethylene resin porous tube as a separation membrane, in order to improve the permeation flow rate, a method of increasing the tube film thickness, increasing the porosity, or combining them may be considered. In any case, the strength of the porous tube is reduced, which is not suitable for practical use.

When used as an artificial blood vessel, the average pore diameter and porosity are increased or the film is made thinner in order to improve the penetration of living tissue from the outer surface of the tetrafluoroethylene resin porous tube and promote the so-called healing effect. Then, the strength of the tube is reduced and the antithrombotic property is deteriorated.

As described above, it is extremely difficult to independently control and improve the desired function of the porous tetrafluoroethylene resin tube without deteriorating properties such as strength in the prior art.

By the way, in general, as a high-performance separation membrane, an asymmetric membrane in which a dense active layer and a porous support layer are formed in one step using the same material, or an ultrathin film layer contributing to separation and a support layer that supports this Is known in two steps, but these known techniques cannot be applied to porous tetrafluoroethylene resin tubes as they are. No effective means has been proposed.

Until now, as an attempt to multi-layer a porous polytetrafluoroethylene resin tube, the main purpose is to reinforce the main purpose of reinforcement by wrapping a porous polytetrafluoroethylene resin tape around the porous tube in a spiral shape. It is only proposed to attach and process it and use it as an artificial blood vessel or the like. However, when a polyethylene tetrafluoride resin porous film tape is wound around the porous surface of the polyethylene tetrafluoride resin porous tube, although the reinforcement is possible, the porosity is significantly impaired and the function cannot be improved. In addition, the winding operation is complicated.

[Problems to be solved by the invention]

An object of the present invention is to provide a porous tetrafluoroethylene resin tube having a multilayer structure of two or more layers having different average pore diameters, porosity or fiber length.

Further, an object of the present invention is to use a paste extrusion method to form a porous tetrafluoroethylene resin tube having a multilayer structure,
It is to provide by integral molding.

The inventor of the present invention has conducted intensive studies to overcome the problems of the prior art, and as a result, each of them contains a tetrafluoroethylene resin fine powder and a liquid lubricant, and has different compositions (compounding components and / or mixing ratios). After performing pre-molding, preferably using two or more compositions, a tube having a multilayer structure of two or more layers composed of each composition is integrally molded by paste extrusion, followed by ordinary porosity and firing. Were sequentially obtained, it was found that a porous tube of a polytetrafluoroethylene resin having a multilayer structure having two or more layers having different average pore diameters and porosity was obtained.

And, for example, in a porous tube used as a separation membrane, by thinning a layer having an average pore diameter required for separation, the permeation flow rate is improved while maintaining the separation efficiency, and on the other hand, the strength that is reduced by the thinning is reduced. This can be compensated for by providing a relatively thick porous layer (coarse layer) having a high porosity and having almost no effect on the permeation flow rate. Further, by devising a laminated structure, it is possible to produce a porous tube of tetrafluoroethylene resin having a new function.

Moreover, according to the above-described method, a multilayer tetrafluoroethylene resin porous tube can be obtained by integral molding.
Porosity is not impaired.

The present invention has been completed based on these findings.

[Means for solving the problem]

Thus, according to the present invention, pre-molding was performed as desired using two or more types of compositions containing at least the tetrafluoroethylene resin fine powder and the liquid lubricant and having different blending components and / or blending ratios. Thereafter, a tube having a multilayer structure of two or more layers of each composition is integrally molded by paste extrusion, and then porous and baked sequentially to obtain a porous tetrafluoroethylene resin. A tube is provided.

 Hereinafter, the present invention will be described in detail.

(Polytetrafluoroethylene Resin Tube) The porous tetrafluoroethylene resin tube of the present invention has a multilayer structure having at least two layers having different physical properties selected from the average pore diameter, fiber length and porosity. Things.

The porous tube of a tetrafluoroethylene resin having a multilayer structure of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic sectional view showing a specific example of the porous tube of the present invention. 1 is a dense layer having a small pore size and / or low porosity, 2 is a porous layer having a large pore size and / or high porosity (coarse layer), and these two layers form one integrally formed porous tube. ing. 3 represents a lumen. The average pore size and the porosity are relative to each other.

FIG. 2 is a schematic view of an enlarged portion of the area A (rectangle) in FIG. 1, and has a multilayer structure having a thick dense layer 2 having a large average pore diameter inside a thin dense layer 1 having a small average pore diameter. Here is an example.

FIG. 3 shows a specific example in which a dense layer 1 is provided inside and a coarse layer 2 is provided outside.

FIG. 4 shows a specific example in which the dense layers 1 and 1 are provided inside and outside the rough layer 2.

By integrally molding a multi-layered porous tube having two or more layers having different average pore diameters and porosity as described above, it is possible to add a new function or reduce a desired function without reducing strength and other functions. Function can be improved.

For example, when a porous tube having a multilayer structure as shown in FIG. 1 or FIG. 3 is used as a separation membrane, a layer (usually a dense layer) 1 having an average pore diameter required for separation is made thinner, and the thickness is reduced by thinning. By supplementing the strength with the coarse layer 2 having a high average porosity and a high porosity that hardly affects the permeation flow rate, it is possible to achieve both improvement in permeation flow rate and strength.

When a porous tube having a multilayered structure as shown in FIG. 3 is used as an artificial blood vessel, the inner surface that comes into contact with the solution is a dense layer 1 having good antithrombotic properties, and living tissue from the outside is removed. The size and porosity of the holes required for entry can be secured by the outer coarse layer 2.

Further, the porous tube having a multilayer structure as shown in FIG. 4 uses two porous portions of the coarse layer between the two dense layers 1 and 1 as a room-like space, for example, an enzyme in a bioreactor, Encloses bacterial cells or various drugs,
By fixing, a porous tube having a new function can be obtained.

(Manufacturing method) The tetrafluoroethylene resin porous tube of the present invention contains two or more kinds of compositions containing a tetrafluoroethylene resin fine powder and a liquid lubricant and having different blending components and / or blending ratios. Preferably, after pre-molding, a tube having a multilayer structure of two or more layers of each composition is integrally molded by paste extrusion, followed by successively performing porosity and sintering.

Two or more types of compositions having different blending components and / or blending ratios are prepared by changing the molecular weight of the tetrafluoroethylene resin, the blending ratio of the liquid lubricant, the presence or absence of the pore-forming agent, or the blending ratio. .

Two or more compositions are used, preferably in a pre-molding step, to form a pre-molded article arranged in a multilayer. As a method of pre-molding, a pre-molded article is prepared by arranging various kinds of compositions in a multi-layered form and then compressing them by applying pressure or by pre-molding using one or more kinds of compositions. There is a method of preparing a compacted preform, placing another composition in the outer layer and / or inner layer thereof, compacting it again once or more times, and producing a preformed product.

The multi-layer tube can be obtained by extruding the preformed product which has been solidified into a cylindrical shape at a temperature lower than the sintering temperature of the ethylene tetrafluoride resin, usually at room temperature.

In addition, the cylinder of the paste extruder in the extrusion process is formed in multiple layers, and the tetrafluoroethylene resin composition and / or the preform having a different composition is arranged in each layer in the cylinder, and the multilayer structure is formed simultaneously with the extrusion. A method of making a tube can also be adopted.

The extruded tube is then made porous by removing the liquid lubricant (auxiliary oil) by a method such as drying and extraction, or without removing it, and extending in the longitudinal direction or in the longitudinal and radial directions. it can. Porosity can be obtained by a method other than the stretching method, such as extraction of a pore-forming agent and foaming with a foaming agent. Further, the porosity may be obtained by combining two or more of these methods.

The tube that has been made porous by stretching or the like is fired by heating it to a temperature equal to or higher than the sintering temperature of the tetrafluoroethylene resin (327 ° C.), and a porous tube having improved strength is obtained.

The ethylene tetrafluoride resin used in the present invention is usually a fine powder having a number average molecular weight (Mn) of 200,000 to 20,000,000. To form a dense layer with a small pore size and / or low porosity, Mn uses a relatively large tetrafluoroethylene resin, and conversely, to form a coarse layer with a large pore size and / or high porosity, Mn uses a relatively small tetrafluoroethylene resin. Mn
The magnitude of is relative, and depending on the desired separation efficiency, permeation flow rate, etc., an appropriate size of Mn-containing tetrafluoroethylene resin is selected and used in combination as each raw material constituting the multilayer. In general, a resin having Mn in the range of 2 to 20 million is used to form a dense layer, a resin having Mn in the range of 200 to 2 million is used to form a coarse layer, and It is preferable that the Mn of the ethylene tetrafluoride resin forming the dense layer is relatively increased.

As the liquid lubricant, various lubricants conventionally used in the paste extrusion method can be used. Specific examples include solvent naphtha, petroleum solvents and hydrocarbon oils such as white oil, toluene, ketones, esters, silicone oil, polyisobutylene, a solution of a polymer such as polyisoprene in these solvents,
Examples thereof include a mixture of two or more of them, water or an aqueous solution containing a surfactant, and the like.

In the paste extrusion method, usually, tetrafluoroethylene resin 100
10 to 40 parts by weight of liquid lubricant with respect to parts by weight, preferably
Extrusion molding is performed by blending 15 to 30 parts by weight. The average pore size, porosity, fiber length, and the like can also be changed by changing the mixing ratio of the liquid lubricant in the composition used for each layer. Generally, to form a dense layer, it is preferable to make the ratio of the liquid lubricant relative to the tetrafluoroethylene resin relatively small, and to form a coarse layer, it is preferable to make the ratio of the liquid lubricant relatively large. .

Porosity can be achieved by using a pore-forming agent. Alternatively, a pore-forming agent may be blended in order to assist the formation of a porous structure by the stretching method. Examples of such pore formers include substances that can be removed or decomposed by heating, extraction, dissolution, and the like, such as powders or solutions of ammonium chloride, sodium chloride, other plastics, rubber, and the like. The average pore diameter, porosity, fiber length, and the like can also be changed by changing the presence or absence or the mixing ratio of the pore-forming agent in the composition used for each layer. Generally, in order to form a dense layer, it is preferable to make the ratio of the pore forming agent relative to the tetrafluoroethylene resin relatively small, and to form a coarse layer, it is preferable to make the ratio of the pore forming agent relatively large. .

If desired, pigments for coloring, carbon black, graphite, silica powder, asbestos powder, glass powder, glass fiber, etc. for improving abrasion resistance, preventing low-temperature flow and facilitating generation of pores, etc. Inorganic fillers such as silicates and carbonates, metal powders, metal oxides, metal sulfides, and the like can be appropriately added.

(Operation)

By making the polytetrafluoroethylene resin porous tube a multi-layered structure, for example, in the case of a separation membrane, a layer having a pore diameter necessary for separation is made thinner, and a decrease in strength that occurs when the flow rate is improved is reduced by a sufficiently large pore diameter. This can be compensated for by providing a rough layer that does not affect the flow rate.

In the artificial blood vessel, the inner surface that comes into contact with blood is a dense layer with high antithrombotic properties, and the size and porosity of pores necessary for invasion of living tissue from the outside are maintained by a coarse layer provided on the outside. The strength and shape generated by the thinning of the layer can be compensated.

Further, if a triple structure (dense layer / rough layer / dense layer) is used as shown in FIG. 4, a room-like space composed of a coarse layer of pores sandwiched between the dense layers is formed within the thickness of the porous tube. A substance can be enclosed and fixed here depending on the purpose.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to only these Examples.

In addition, the measuring method of the physical property in these examples is as follows.

Porosity: According to ASTM-D-792, porosity is a value obtained from the specific gravity (apparent specific gravity) obtained in water and the specific gravity of the tetrafluoroethylene resin. The larger the value, the more excellent the permeability.

Average pore size: The pore size distribution was determined according to ASTM-F-316-80, and the average pore size was calculated.

Valve point: Measured using isopropyl alcohol according to the method of ASTM-F-316-80.

The permeation flow rate was measured with isopropyl alcohol at 20 ° C. at a differential pressure of 1 atm. The larger the value, the better the transmittance.

Fiber length: Obtain the obtained porous tube with a microscope,
The visual field was shown as an average value of 150 lines each, a total of 150 lines.

Burst pressure: One end of the porous tube was sealed, water was allowed to flow into the tube lumen from the other end, the water pressure was gradually increased, and the water pressure at which the tube burst was measured, which was defined as the burst pressure. The magnitude of the burst pressure is an index of the magnitude of the strength of the porous tube.

[Example 1] A first composition was prepared by mixing 100 parts by weight of a tetrafluoroethylene resin fine powder CD-123 (Mn = about 20 million) manufactured by Asahi IC Fluoropolymers Co., Ltd. with 26 parts by weight of solvent naphtha. .

Also, fine powder of ethylene tetrafluoride resin CD-1 (Mn = 2,000,000) 100
By weight, 30 parts by weight of solvent naphtha were mixed to prepare a second composition.

After arranging the first composition and the second composition in a multilayer form, after pre-molding by compressing with a pressure of 50 kg / cm ² ,
It was extruded into a tube by a paste extruder.

The thickness of the outer layer made of the first composition is 0.05 mm (inner diameter / outer diameter = 4.1 mm / 4.2 mm), and the thickness of the inner layer made of the second composition is
It was 0.55 mm (inner diameter / outer diameter = 3.0 mm / 4.1 mm).

After drying at 50 ° C. for 48 hours, the film was stretched 275% in the longitudinal direction under dry heat at 200 ° C., and then fired in a heating furnace at 400 ° C. for 1 minute.

The obtained multilayer porous tube of tetrafluoroethylene resin has an outer diameter of 3.0 mm and a total thickness of 0.5 mm (inner layer of 0.05 mm).
mm, outer layer 0.45 mm).

The physical properties of this porous tube of ethylene tetrafluoride resin are shown in Table 1 together with the production conditions.

[Comparative Example 1] A 0.5 mm thick tube (inner diameter / outer diameter = 3.0 mm / 4.0 mm) was obtained by paste extrusion using only the first composition of Example 1, and the stretching ratio was set to 300%. In the same manner as in Example 1, a single-layered porous polyethylene tetrafluoride resin tube was obtained.

 The results are shown in Table 1.

As is clear from Table 1, the multilayer structure of the dense layer (outer layer) and the coarse layer (inner layer) (Example 1) makes the average pore diameter and the strength higher than those of the single layer (Comparative Example 1). Were almost the same, and the permeation flow rate could be improved about twice.

[Example 2] A first composition was prepared by mixing 100 parts by weight of a tetrafluoroethylene resin fine powder CD-123 (Mn = about 20 million) manufactured by Asahi IC Fluoropolymers Co., Ltd. and 27 parts by weight of solvent naphtha. .

Also, a second composition was prepared by mixing 100 parts by weight of fine powder of ethylene tetrafluoride resin F-104 (Mn = 4 to 5,000,000) manufactured by Daikin Industries, Ltd. and 23 parts by weight of solvent naphtha.

After arranging the first composition and the second composition in a multilayer shape, they were pressed and compacted by applying a pressure of 50 kg / cm ² , and then extruded into a tube by a paste extruder.

The thickness of the inner layer made of the first composition is 0.1 mm (inner diameter / outer diameter = 3.0 mm / 3.2 mm), and the thickness of the outer diameter made of the second composition is
It was 0.5 mm (inner diameter / outer diameter = 3.2 mm / 4.2 mm).

After drying at 50 ° C for 48 hours, under 350 ° C dry heat, supply line speed
Under the conditions of 2.0 m / min, the film was stretched by 500% in the longitudinal direction, and then fired in a heating furnace at 400 ° C. for 0.75 minutes.

The obtained multilayer porous tube of tetrafluoroethylene resin has an outer diameter of 3.0 mm and a total thickness of 0.5 mm (inner layer of 0.05 mm).
mm, outer layer 0.45 mm).

Table 2 shows the physical properties of the porous tetrafluoroethylene resin tube together with the production conditions.

The obtained tube has the same fiber length of the inner layer in contact with blood and has the same level of antithrombotic properties as compared with a commercially available artificial blood vessel of this type. The hole just outside the thin inner layer has a large hole, and it has been confirmed that the structure has a structure that facilitates invasion and organization of living tissue from the outside of the artificial blood vessel.

[Effects of the Invention] Conventionally, porous polytetrafluoroethylene resin tubes are often used for applications utilizing porosity, but resistance (flow rate) when passing through the pores and limitation of the substance passing therethrough (pore diameter) ), It was difficult to independently control the strength of the tube itself against breakage. Therefore, it is necessary to compensate for the characteristics sacrificed to satisfy one condition. If this is performed by reinforcement after forming the tube, as in the prior art, the porosity of the tube body will be impaired.

On the other hand, according to the present invention, the characteristics can be supplemented by the layer added by integral processing without impairing the porosity.

According to the present invention, for example, by adopting a dense layer / rough layer / dense layer configuration, a three-dimensional structure can be provided in the tube thickness direction. That is, the space between the dense layers can be provided inside the tube. This allows
For example, enzymes, bacterial cells, etc. in a bioreactor are confined in this space and used as a reaction chamber, and the reaction system as a bioreactor, such as from the tube lumen to the internal space (reaction chamber) and from the internal space to the outside of the tube. It can also be used for applications such as establishment or bioreactor modules using this tube.

Furthermore, it is also possible to encapsulate a drug in the internal space and release the drug from the inner and outer surfaces of the tube.For example, an antithrombotic agent can be encapsulated and used as the outer wall of a catheter, as a tube for an artificial lung. So-called DDS, such as use
(Drug delivery system) can be expected.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a tetrafluoroethylene resin porous tube of the present invention, and FIG. 2 is an enlarged view of a square (A) in FIG. 3 and 4 are schematic cross-sectional views showing specific examples of other combinations of the multilayer structure of the porous tetrafluoroethylene resin tube of the present invention. 1: dense layer with small pore size and / or low porosity, coarse layer with large pore size and / or high porosity compared to 2: 1, 3: tube lumen.

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Claims (3)

(57) [Claims] 1. A pre-molding method comprising the use of two or more compositions containing at least a fine powder of ethylene tetrafluoride resin and a liquid lubricant and having different blending components and / or blending ratios. A porous tube of ethylene tetrafluoride resin, which is obtained by integrally molding a tube having a multilayer structure of two or more layers of each composition by extrusion, and then sequentially performing porosity and firing. 2. The composition according to claim 1, wherein the composition and / or two or more compositions having different blending ratios have different molecular weights of ethylene tetrafluoride resin.
2. The ethylene tetrafluoride resin porous tube according to claim 1, wherein at least one of the compounding ratio of the liquid lubricant, the presence or absence of the pore-forming agent, and the compounding ratio is different. 3. The porous tube of claim 1, wherein the porous tube has two or more layers having at least one layer having different physical properties selected from an average pore diameter, a fiber length and a porosity.