JPH0698280B2 - Method for manufacturing support tube for permeable membrane - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a support tube for a porous permeable membrane, and more specifically, it is made of laminated porous nonwoven fabric or woven fabric and has excellent mechanical strength and , A method for manufacturing a support tube for a permeable membrane, the entire inner surface of which is substantially flat.

(Prior Art) A separation method using a permeable membrane such as an ultrafiltration membrane or a reverse osmosis membrane is already widely known. Here, the permeable membrane usually has a thickness of about 50 to 500 μm, and the strength of the membrane itself is extremely small. Therefore, the permeable membrane is generally formed on the inner surface of a support pipe such as a non-woven fabric pipe or a perforated reinforced resin pipe. Such a permeable membrane is formed, and thus it is practically used as a reinforced tubular permeable membrane in which the permeable membrane is reinforced by a support tube.

As a method of manufacturing a supporting tube for such a reinforced tubular permeable membrane, conventionally, for example, as described in JP-B-57-24165, a nonwoven fabric tape made of a thermoplastic resin fiber is provided on the side of the core body. There is known a method in which the layers are superposed on each other and wound in a spiral shape, and the overlapping portion is heat-welded.

However, in such a method, in order to impart negative pressure resistance and mechanical strength to the obtained support tube, it is usually 200 to 500 μm.
Since a comparatively thick non-woven tape having a thickness of about m is used, as shown in FIG. 2, a step 24 is generated as a result of the step 24 in the superposed part 23 where the non-woven tape 22 is heat-welded on the core body 21. The support tube provided does not have a uniform inner diameter and the inner surface is not flat. Therefore, when a permeable membrane is formed on the inner surface of such a support tube, the permeable membrane becomes thin at the step portion 24, and the strength of the permeable membrane is reduced. As a result, the permeable membrane is easily damaged during the membrane treatment. Moreover, the welded overlapped portion
In No. 23, since the non-woven fabric loses its porosity, such a superposed portion becomes impermeable and reduces the flow path of the membrane permeate.
In addition, the permeable film formed on the superposed portion is
When no pressure is generated in the permeable membrane during membrane treatment, the membrane is easily peeled off from the support tube, which causes membrane damage.

Furthermore, when the non-woven fabric tape is wound around the core body, fluffing of the non-woven fabric fiber occurs on the inner surface of the support tube due to friction between them, and therefore when forming a permeable membrane on the inner surface of the support tube, the fluffing occurs. Penetration of the permeable membrane causes film defects such as pinholes, which significantly impairs the reliability of the film.

On the other hand, a nonwoven fabric sheet containing heat-fusible fibers is wound around a core body to have a predetermined outer diameter, and then heat-treated to melt only the heat-weldable fibers to bond the whole. A method for producing a cylindrical filter having a wall thickness of several tens of mm is described in, for example, Japanese Patent Laid-Open No. 34680/50. However, in the support tube for the permeable membrane, in order to ensure a high membrane permeate flux, the porosity of the non-woven tape laminated on the core is ensured and the inner diameter is uniform, and the internal cost is low. Since it is strongly required that the surface is flat, it is not possible to obtain a support tube for a permeable membrane that can meet the above-mentioned demands, simply by winding the nonwoven fabric tape around the core and then heating it.

(Object of the Invention) The present invention has been made in order to meet the above-mentioned requirements, and a laminated non-woven fabric or woven fabric is uniformly bonded to the whole while maintaining a porous structure, and the mechanical strength is improved. Excellent,
Moreover, there is no fluff on the inner surface, and the entire inner surface is substantially flat. Therefore, when forming a permeable membrane such as a reverse osmosis membrane or an ultrafiltration membrane on the inner surface, a pinhole or the like is formed in the membrane. It is an object of the present invention to provide a method for manufacturing a support tube for a permeable membrane, in which the membrane defect does not occur and a reinforced permeable membrane having extremely high reliability can be obtained.

(Structure of the Invention) A first method of manufacturing a support tube for a permeable membrane according to the present invention is to spirally wind a first tape made of a non-woven fabric or a woven fabric containing heat-welding fibers with its side edges abutting against a core body. , The side edges are abutted on top of each other so as not to overlap the abutting portion, and a second tape made of a non-woven fabric or a woven fabric is spirally wound and then heated to melt or soften the heat-weldable fiber. Then, the tapes are adhered to each other.

The second method of manufacturing the support tube for a permeable membrane according to the present invention
Is a non-woven fabric or woven fabric containing the heat-weldable fiber
Spirally wrap the core tape on the core body with side edges abutting, and then wrap the spiral tape with a second tape made of non-woven fabric or woven fabric by abutting the side edges on the core body so as not to overlap the abutting portion. Then, after winding or braiding the heat-welding fibers, heating is performed to melt or soften the heat-welding fibers in the first tape to bond the tapes to each other, and the wound heat-welding fibers Is welded to the tape.

In the present invention, the non-woven fabric or woven fabric containing the heat-fusible fiber is preferably a thermoplastic resin having a relatively low melting point or softening point (hereinafter referred to as a low-melting resin, which is softened or melted to have the heat-welding property). .) And a thermoplastic resin (hereinafter, referred to as a high melting point resin) that is substantially softened or does not melt at a temperature heated for welding, a non-woven fabric or a woven fabric. It is cloth.
The first tape is made of such non-woven fabric or woven fabric.

One preferable specific example of such a composite fiber is a fiber having a multi-layer structure in which a high-point resin fiber as an inner layer is covered with a low-melting resin as an outer layer. However, the structure of the composite fiber is not limited to the above as long as heat fusion occurs between the fibers due to heating, and in general, at least a part of the surface of the high melting point resin fiber is a low melting point resin. The conjugate fiber formed by being coated with is preferably used. Such conjugate fibers are already known, for example, as described in JP-A-55-24575.

Further, in the present invention, as a non-woven fabric or woven fabric containing heat-fusible fibers, as described in JP-A-50-34680, a low melting point thermoplastic resin fiber and a high melting point thermoplastic resin, It is also possible to use a fiber-mixed non-woven fabric or a woven fabric in which the above is mixed to form a web, and the web is heated to heat-weld the fibers together.

The low melting point resin and the high melting point resin are not particularly limited, but in consideration of the melting point or the softening point, for example, polyethylene, polypropylene, polyamide, polyester, etc. are appropriately combined and used. Natural fibers are also used as needed.

In the method of the present invention, among the non-woven fabrics or woven fabrics containing the above-mentioned heat-fusible fibers, in particular, about 10 to 70% of the fiber weight is composed of the low melting point resin, and the melting point or softening point has a high melting point. Nonwoven fabrics and woven fabrics containing heat-fusible fibers containing a low melting point resin that is at least about 10 ° C. lower than the resin are preferably used. When the low melting point resin in the non-woven fabric or the woven fabric containing the heat-fusible fibers is less than about 10%, the welding between the fibers is insufficient even if the support tube is formed by the method described later, Inferior in strength. On the other hand, about 70%
When it is more than the above range, the fusion between the fibers due to heating becomes excessive, the porosity of the supporting tube decreases, and the permeation resistance of the membrane permeate increases.

When the difference in melting point or softening point between the low-melting point resin and the high-melting point resin is less than about 10 ° C., not only the low-melting point resin but also the high-melting point resin is melted or softened by heating, and the same as above. It is not preferable because it lowers the porosity of the support tube. To retain the porous structure of the non-woven fabric or the woven fabric and to weld them to each other and adhere them uniformly over the whole,
The difference in melting point or softening point between low melting point resin and high melting point resin is about 30 ℃
Is preferably larger than.

In the method of the present invention, the thickness of the first tape made of a non-woven fabric or a woven fabric containing heat-fusible fibers is not particularly limited, but it is usually preferably 100 μm or less.

The second tape made of a non-woven fabric or a woven fabric may or may not include the heat-welding fiber as described above. The first tape may be the same as the second tape when the second tape comprises heat fusible fibers. In this case, in the method of the present invention, at least two tapes made of a non-woven fabric or a woven fabric containing the heat-welding fibers are spirally wound so that the abutting portions do not overlap each other on the core body.

The second tape can be wrapped in more than one layer,
If the second tape does not contain heat fusible fibers, it is necessary to wind the first tape between them as described above and to interpose the first tape between the second tapes.

The thickness of the second tape is also not particularly limited, but is usually preferably 100 μm or less.

In this way, after the first tape and the second tape are wound around the core body, they are introduced into a heater to uniformly heat the whole body to melt or melt the heat-welded fibers contained in the first tape. It is softened and the whole is evenly welded, thus obtaining the support tube according to the invention. The heating means is not limited at all, for example,
A hot plate, infrared rays, heating, etc. are used.

According to the method of the present invention, in order to obtain a supporting tube which is porous and has excellent strength, the whole is uniformly joined in a net-like shape by such welding of the tape by heating. And the second tape, the basis weight is a (g /
m ² ), thickness t (mm), density of raw material polymer ρ (g / c
m ³ ), it is preferable to use a tape having an apparent porosity defined by 1− (a / tρ) × 10 ⁻³ of 0.15 to 0.85, preferably 0.25 to 0.80.

Further, according to the method of the present invention, after the first and second tapes are wound, the heat-welding fiber itself can be further wound or braided on the first and second tapes. According to this method,
A more reinforced support tube can be obtained. As the heat-fusible fiber for this purpose, the composite fiber formed by coating at least a part of the surface of the high melting point resin fiber with the low melting point resin as described above is preferably used.

The method of the present invention will be described with reference to FIG. A first tape 12 made of a non-woven fabric or a woven fabric containing heat-fusible fibers is butted on the core body 11 so as not to overlap the side edges 13 and wound in a spiral shape. The tape (not shown) is wrapped in one or more layers in multiple layers.
At this time, the tape wound around the outer layer is wound so that the butted portion does not overlap the butted portion of the inner layer tape.

Then, a second tape 14 made of a non-woven fabric or a woven fabric is further placed on the core body around which the first tape 12 is wound in this way so that the side edges 15 thereof do not overlap and the first tape is placed inside.
The tape 12 is spirally wound while forming the butted portion 17 so as not to overlap the butted portion 16 of the tape 12.

In this way, the first tape and the second tape wound around the core body 1 are passed through the heater 18 while rotating and advancing the tape, and the tape on the core body is uniformly heated to the first tape. The low melting point resin is melted or softened, and thus uniformly welded between the first tape and the second tape to obtain the support tube 19 according to the present invention.

In the method of the present invention, it is desirable for the tapes to be perfectly butted and spirally wrapped, but it is unavoidable that laps or gaps between the side edges occur.

(Effects of the Invention) As described above, according to the method of the present invention, the nonwoven fabric or the woven fabric tape is abutted on the core body so that their side edges do not overlap each other, and the tape is wound in a spiral shape. The heat-sealable fibers contained in the tape ensure uniform welding between the tapes. Therefore, in the support tube thus obtained, unlike the conventional support tube, a laminated non-woven fabric or a woven cloth does not have a step portion based on the welded overlapped portion and a non-porous portion, and is a tube. While maintaining a uniform porous structure over the entire surface, it is welded uniformly over the entire surface, so it has excellent mechanical strength, and there is no fluff on the inner surface, and the entire inner surface is substantially flat. .

Therefore, a reinforced permeable membrane formed by forming a permeable membrane such as a reverse osmosis membrane or an ultrafiltration membrane on the inner surface of such a support tube is
It has no film defects such as pinholes and has extremely high reliability.

(Examples) Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1 A polyethylene fiber was coated around the polypropylene fiber as an inner layer in a layered manner, and the weight ratio of polyethylene was 50%.
28.0 mm width, 70 μm thickness, and 0.75 apparent porosity of heat-weldable non-woven fabric tape made of heat-weldable fiber, the side edges of which are abutted against each other on the core having an outer diameter of 12.0 mm, and Two layers were spirally wound so that the abutting portion did not overlap the abutting portion of the inner layer.

In addition, a width of 28.0 made of the same heat-welding fiber as above
The heat-welding nonwoven fabric tape having a thickness of 150 mm, a thickness of 150 μm, and an apparent porosity of 0.40 was spirally wound with its side edges abutted so that the abutting portion of the outer layer tape did not overlap the abutting portion of the inner layer.

Then, while rotating the core body in which the non-woven fabric tape is wound in three layers in this manner, the non-woven fabric tape is passed through a heater equipped with a heating plate at 160 ° C. to uniformly heat the whole non-woven fabric tape, and thus the support tube according to the present invention. Got

The thus-obtained support tube had a porous structure as a whole, no non-porous portion was observed, it had a uniform inner diameter, the inner surface was flat, and fluffing did not occur. Nakatsuta.

The inner surface of this support tube was coated with a film-forming solution consisting of 25 parts by weight of cellulose acetate, 30 parts by weight of formamide and 45 parts by weight of acetone to a thickness of 300 μm, and then immersed in water to solidify the cellulose acetate to reinforce it. A tubular permeable membrane was obtained.

This reinforced tubular permeable membrane was inserted into a perforated stainless steel tube with an inner diameter of 13.0 mm, and while circulating water colored with red ink in the tubular permeable membrane, pressurizing the cormorant pressure to 50 kg / cm ^{2 and} then the atmospheric pressure. Returned to. Similarly, after repeating such pressurizing operation 100 times, the reinforced tubular permeable membrane was taken out of the stainless steel tube and the membrane surface was observed in detail, but no abnormality was observed.

Further, no pressure of 60 cmHg was applied to the reinforced tubular permeable membrane obtained in the same manner for 3 minutes, but no peeling of the membrane occurred.

Example 2 A pulp-like fiber made of polypropylene fiber and polyethylene was mixed at a weight ratio of 2: 3 to have a width of 28.0 mm and a thickness of 100 μm.
m, heat weldable non-woven tape with apparent porosity of 0.65
The layers were spirally wound into one layer with their side edges abutting each other on a 2.0 mm core. Further, a heat-welding nonwoven fabric tape having a width of 28.1 mm, a thickness of 150 μm, and an apparent porosity of 0.40 made of the same heat-welding composite fiber as in Example 1 was butted against the side edges, and the tape of the inner layer was butted. It was wound in a spiral so that it would not overlap the part. Then, while rotating the non-woven tape thus wound around the core body in two layers in the same manner as in Example 1, the whole was heated by a heating plate at 160 ° C. by a heater to obtain a support tube according to the present invention.

The support tube thus obtained retains a porous structure as a whole, no non-porous portion is observed, and the inner tube has a uniform inner diameter and a flat inner surface. There was no fuzz.

Using this support tube, a reinforced tubular permeable membrane was produced in the same manner as in Example 1, and the membrane surface was observed in detail after repeating the pressurizing operation in the same manner, but no abnormality was observed. It was In addition, in the reinforced tubular permeable membrane obtained in the same manner, 60
A negative pressure of cmHg was applied for 3 minutes, but no peeling of the film occurred.

Comparative Example Width 28.0 mm and thickness 30 made of the same heat-welding fiber as in Example 1
A 0 μm, apparent porosity 0.41K heat-welding nonwoven fabric tape was superposed on the core body and spirally wound so that the width was 1.5 mm. Next, while rotating and advancing this, an ultrasonic horn having a frequency of 25 KHz was pressed against the overlapping portion and heat-welded at a speed of 4.0 m / min to obtain a supporting tube with the overlapping portion welded.

On the inner surface of the obtained support tube, fluffing of fibers of 0.05 to 3 mm was observed, and a step having a thickness of 410 μm was formed at the welded portion where the tapes were overlapped.

Using this supporting tube, a reinforced tubular permeable membrane was produced by the same method as in Example 1, and after repeating the pressurizing operation in the same manner, the membrane surface was observed in detail. Shows a large number of cracks, and many spots where the red ink has passed are observed on the inner surface of the support tube other than the welded part.When these spots are observed with an electron microscope, they are pinholes due to fuzz on the inner surface of the support tube. It was confirmed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view for explaining a method of the present invention, and FIG. 2 is a partially enlarged view showing a superposed portion of a support tube according to a conventional method. 11 ... core, 12 ... first tape, 14 ... second tape, 16 ... first tape butting portion, 17 ... first tape butting portion, 18 ... heater, 19 …… Support tube.

 ─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-55-34144 (JP, A) JP-A-55-39279 (JP, A) JP-A-50-34680 (JP, A) JP-B 57- 24165 (JP, B1) SHOKO 59-40625 (JP, Y2)

Claims (7)

[Claims] 1. A first tape made of a non-woven fabric or a woven fabric containing heat-fusible fibers is wound spirally on the core body with its side edges abutted, and the side edges are not overlapped with the abutted portion. And a second tape made of a non-woven fabric or a woven fabric is spirally wound and then heated to melt or soften the heat-weldable fiber to maintain the porous structure and to mutually bond the tapes. A method for manufacturing a support tube for a permeable membrane, which comprises bonding. 2. A non-woven fabric or a woven fabric containing heat-fusible fibers is composed of composite fibers formed by coating at least a part of the surface of high melting point thermoplastic resin fibers with a low melting point thermoplastic resin. The method for manufacturing a support tube for a permeable membrane according to claim 1, wherein 3. A non-woven fabric or woven fabric containing heat-fusible fibers is a non-woven fabric or woven fabric made of a fiber mixture of high melting point thermoplastic resin fibers and low melting point thermoplastic resin fibers. A method of manufacturing a support tube for a permeable membrane according to claim 1. 4. A first tape made of a non-woven fabric or a woven fabric containing heat-fusible fibers is wound spirally with the side edges abutting on the core body, and the side edges are not overlapped with the abutting portion. And a second tape made of a non-woven fabric or a woven fabric is spirally wound, and then the heat-welding fiber is wound or braided, and then heated to melt or soften the heat-welding fiber in the first tape. Then, while maintaining the porous structure, while adhering the tapes to each other,
A method for manufacturing a support tube for a permeable membrane, which comprises welding the wound heat-fusible fiber to a tape. 5. A non-woven fabric or a woven fabric containing heat-fusible fibers is composed of composite fibers formed by coating at least a part of the surface of high melting point thermoplastic resin fibers with a low melting point thermoplastic resin. The method for producing a transparent film supporting tube according to claim 4, characterized in that: 6. A non-woven fabric or woven fabric containing heat-fusible fibers is a non-woven fabric or woven fabric made of a fiber mixture of high melting point thermoplastic resin fibers and low melting point thermoplastic resin fibers. A method for manufacturing a support tube for a permeable membrane according to claim 4. 7. The heat-fusible fiber for winding or braiding comprises a composite fiber in which at least a part of the surface of the high melting point thermoplastic resin fiber is coated with the low melting point thermoplastic resin. Claim 4 characterized by the following:
A method of manufacturing a support tube for a permeable membrane according to item.