JPS6377501A - Production of supporting pipe for permeable membrane - Google Patents

Abstract

PURPOSE:To produce the title supporting pipe without any fuzz by abutting a first and a second sheet fibrous material-based tape on each other so that the respective side edges are not placed on each other, shaping the tapes into a pipe, and uniformly welding both tapes to each other by the hot-melt fiber contained in the tape. CONSTITUTION:The first tape 12 consisting of a sheet fibrous base material contg. the hot-melt fiber of polyethylene, etc., and the second tape 14 are introduced into a hollow convergent taper pipe 11, the respective side edges 13 and 15 of the tapes are abutted on each other in the axial direction of the pipe so that the abutted parts 16 and 17 do not over-lap, and the tapes are shaped in the form of a pipe. The material is then introduced into a heater 18, the whole is uniformly heated, and the hot-melt resin contained in the first tape is melted or softened, and the first tape and the second tape are uniformly welded to obtain the supporting pipe 19.

Description

[Detailed description of the invention] 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 sheet-like fibrous base materials and has excellent mechanical strength. The present invention also relates to a method of manufacturing a support tube for a permeable membrane whose entire inner surface is substantially flat.

Separation methods using permeable membranes such as ultrafiltration membranes and reverse osmosis membranes are 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 low. In this way, the permeable membrane is reinforced with a support tube and is used as a reinforced tubular permeable membrane.

Conventionally, as a manufacturing method of a support tube for such a reinforced tubular permeable membrane, as described in Japanese Patent Publication No. 57-24165, a nonwoven fabric tape made of thermoplastic resin fibers is placed on a mandrel and its side edges are A method is known in which the materials are overlapped with each other, wound spirally, and the overlapping portion is heat-welded.

However, in this method, in order to give the resulting support tube good negative pressure resistance and mechanical strength, it is usually necessary to
Since a relatively thick non-woven tape having a thickness of about 0.00 μm is used, as shown in FIG. The support tube has a uniform inner diameter and an uneven inner surface. Therefore, when forming a permeable membrane on the inner surface of such a support tube, the permeable membrane is
4, it becomes thinner and the strength of the permeable membrane decreases.
The permeable membrane is easily damaged during membrane treatment. Moreover, since the nonwoven fabric loses porosity in the welded overlapping portion 23,
Such overlaps become impermeable, reducing the flow path for membrane permeate. Moreover, the permeable membrane formed in such an overlapping portion is easily separated fJJ from the support tube when negative pressure is generated within the permeable membrane during membrane processing, causing damage to the membrane.

Furthermore, when the nonwoven fabric tape is wrapped around the six bodies, the friction between them causes fluff of the nonwoven fabric fibers on the inner surface of the support tube, so when forming a permeable membrane on the inner surface of the support tube, the fluff is Penetrates through the membrane, producing membrane defects such as pinholes, and significantly impairing the authenticity of the membrane.

On the other hand, a nonwoven fabric sheet containing heat-fusible fibers is wound around a mandrel to form a predetermined outer diameter, and then heat-treated to melt only the heat-fusible fibers, resulting in a wall thickness that is obtained by bonding the entire body. A method for manufacturing Juryu's cylindrical filter is described, for example, in Japanese Patent Application Laid-Open No. 34680/1983.

However, in the support tube for the permeable membrane, in order to ensure a high membrane permeate flux, it is necessary to ensure the porosity of the six laminated nonwoven fabric tapes, and to ensure that the inner diameter is uniform. Since it is strongly required that the inner surface be flat, it is not possible to obtain a support tube for a permeable membrane that can meet the above requirements by simply wrapping six pieces of nonwoven fabric tape and then heating it.

(1) Problem to be Solved The present invention has been made to meet the above-mentioned requirements, and is aimed at achieving uniform bonding of laminated sheet-like fibrous base materials while maintaining their porous structure. □Moreover, there is no fluff on the inner surface, and the entire inner surface is substantially flat. Therefore, a permeable membrane such as a reverse osmosis membrane or an ultrafiltration membrane is formed on the inner surface. An object of the present invention is to provide a method for producing a support tube for a permeable membrane, which does not cause membrane defects such as pinholes in the membrane and can obtain an extremely highly reliable reinforced permeable membrane.

A first method for manufacturing a support tube for a permeable membrane according to the present invention is to attach a first tape made of a sheet-like fibrous base material containing heat-fusible fibers to a side edge in the tube axis direction. After abutting each other and shaping it into a tubular shape, a second tape made of a sheet-like fibrous base material is placed on top of it with the side edges abutting each other so as not to completely overlap the abutted portion. The method is characterized in that the tapes are bonded to each other by heating to melt or soften the heat-fusible fibers.

Further, the second method for producing a support tube for a permeable membrane according to the present invention includes a first method comprising a sheet-like fibrous base material containing heat-fusible fibers.
The tape is shaped into a tube by abutting the side edges against each other in the direction of the tube axis, and on top of that, the side edges are abutted against each other so as not to completely overlap with the abutted portion, and the tape is formed from a sheet-like fibrous base material. Next, after wrapping or braiding the heat-fusible fibers, the heat-fusible fibers in the first tape are heated to melt or soften the heat-fusible fibers, thereby bonding the tapes together. , the above-mentioned wound heat-fusible fiber is made to be compatible with the tape).

In the present invention, the sheet-like fibrous base material containing heat-fusible fibers is preferably a thermoplastic resin (hereinafter referred to as low melting point Thermoplastic resins that do not substantially soften or melt at the temperature at which the low melting point resins are heated for welding are hereinafter referred to as high melting point resins. ) is a sheet-like fibrous base material formed from a composite fiber consisting of a non-woven fabric. The first tape consists of such a sheet-like fibrous base material.

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

In addition, in the present invention, as a sheet-like fibrous base material containing heat-fusible fibers, low melting point thermoplastic resin fibers and high melting point thermoplastic resin fibers are used as the sheet-like fibrous base material containing heat-fusible fibers. It is also possible to use a web blended with a resin, or a fiber-mixed nonwoven fabric or woven fabric obtained by heating the web to thermally weld the fibers together.

The above-mentioned low melting point resin and high melting point resin are not particularly limited, but in consideration of the melting point or softening point, for example, polyethylene, polypropylene, polyamide, polyester, etc. are used in appropriate combinations. Natural fibers may also be used if desired.

In the method of the present invention, among the sheet-like fibrous base materials containing the heat-fusible fibers described above, in particular, about 10 to 10% of the fiber weight is
Preferably used is a sheet-like fibrous base material containing heat-fusible fibers containing 70% of the above-mentioned low melting point resin and a low melting point resin having a melting point or softening point lower than that of the high melting point resin by at least about 10°C or more. It will be done. When the low melting point resin in the sheet-like fibrous base material containing heat-fusible fibers is less than about 10%, even if a support tube is formed by the method described later, welding between the fibers will be insufficient. Poor mechanical strength. On the other hand, when the amount is more than about 70%, excessive welding between fibers occurs due to heating, which reduces the porosity of the support tube and increases the permeation resistance of the membrane-permeated liquid.

In addition, 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 will melt or soften due to heating, and the support tube will be melted or softened as described above. This is not preferred because it reduces the porosity of the material. In order to maintain the porous structure of the sheet-like 41-quality base material, weld them together and bond them uniformly over the entire surface,
In particular, it is preferred that the difference in melting point or softening point between the low melting point resin and the high melting point resin is greater than about 30°C.

In the method of the present invention, the thickness of the first tape made of a sheet-like fibrous base material containing heat-fusible fibers is not particularly limited, but it is usually preferably 100 μm or less.

The second tape made of a sheet-like fibrous base material may or may not contain the heat-fusible fibers described above. When the second tape includes heat-fusible fibers, the second tape may be the same as the first tape. In this case, in the method of the present invention, the support tube is constituted by at least 2N of tape made of a sheet-like fibrous base material containing heat-fusible fibers. As described later, the second
When the tape is placed over the first tape shaped into a tubular shape, its side edges may be brought into contact with each other in the tube axis direction in the same manner as the first tape, or it may be wound spirally.

Two or more layers of the second tape can be placed over the first tape shaped into a tubular shape, but if the second tape does not contain heat-fusible fibers, the first tape can be placed in between. It is necessary to intervene.

However, in this case, the first tape interposed between the second tapes may have their side edges abutted along the tube axis, or may be wound spirally.

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

In this way, after shaping the first tape and the second tape into a tubular shape, they are guided to a heater to uniformly heat the whole,
The heat-welding fibers contained in the first tape are melted or softened to uniformly weld the entire tape, thus obtaining a support tube according to the present invention. The heating means is not limited at all, and for example, a hot plate, infrared rays, heated steam, etc. can be used. Further, when welding the tape, pressure may be applied from the inside and outside of the tape shaped into a tubular shape.

In the method of the present invention, in order to obtain a support tube that is porous and has excellent strength by uniformly bonding the entire tape in a network shape by welding the tape by heating, the first step is to weld the tape by heating. and the second tape, its basis weight is a(
g/rrr), the thickness is t (1 m), and the density of the material polymer is ρ (g/cd), then 1-(a/lρ)XIO-
It is preferable to use a tape whose apparent porosity defined by ' is 0.05 to 0.85, preferably 0.10 to 0.80.

Further, according to the method of the present invention, after the first and second tapes are shaped into a tubular shape as described above, the heat-fusible fiber itself can be further wound or braided thereon. According to this method, a support tube that is further reinforced can be obtained. As the heat-fusible fiber for this purpose, a composite fiber formed by covering at least a portion of the surface of a high melting point resin fiber with a low melting point resin as described above is preferably used.

The present invention will be explained in detail based on FIGS. 1 and 2.

A first tape 12 and a second tape 14 made of a sheet-like fibrous base material containing heat-fusible fibers are guided into a hollow tapered pipe 11, and the side edges 13 of each tape are connected to each other and the side edges are 15 against each other in the tube axis direction,
That is, the first tape is formed into a tubular shape by forming an inner layer so that the abutted portion extends in the tube axis direction. At this time, the abutting portions 16 and 17 of the first tape 12 and the second tape 14 are prevented from overlapping each other. In this way, the second tape that is placed over the first tape may have its side edges abutted in the tube axis direction in the same way as the first tape, but it may be , it may be wound spirally. In this case, the abutting portion of the first tape and the abutting portion of the second tape inevitably partially overlap, but such overlap is permitted in the present invention as a state in which the abutting portions do not completely overlap. .

In the present invention, if necessary, a first tape (not shown) can be formed in one or more layers along the outside of the first tape. At this time, the abutting portion of the first tape that is placed along the outer layer does not need to completely overlap the abutting portion of the first tape that is the inner layer. They may be butted against each other in the axial direction of the tube, or they may be wound spirally while their side edges are abutted against each other in the circumferential direction of the tube.

Next, the first tape and the second tape, which have been shaped into a tubular shape in this way, are introduced into the heater 18 to uniformly heat the whole, melting or softening the low melting point resin of the first tape, and thus , the support tube 19 according to the present invention is obtained by welding the first tape and the second tape uniformly throughout.

In addition, when welding the first tape and the second tape, by installing the mandrel 20 inside the tape shaped into a tubular shape, it is possible to apply pressure and obtain a uniform support tube.

In the method of the present invention, it is desirable that the tapes are completely abutted and formed into a tubular shape, but unavoidable overlapping or gaps between the side edges are allowed.

Effects of the Invention As described above, according to the method of the present invention, the sheet-like fibrous base tapes are butted against each other so that their side edges do not overlap each other to form a tubular shape, and the thermal welding contained in the tape is The adhesive fibers uniformly weld the entire tape. Therefore, unlike conventional support tubes, the support tube obtained in this way does not have a stepped part based on welded overlapping parts or a non-porous part, and has a laminated sheet-like fibrous base material. Since it is uniformly welded to the entire surface of the tube while maintaining a uniform porous structure over the entire surface of the tube, it has excellent mechanical strength, and there is no fuzz 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,
It has no film defects such as pinholes and has high reliability.

EXAMPLES The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 Polyethylene is coated around polypropylene fibers as an inner layer in a layered manner, and the weight ratio of polyethylene is 50.
Width 37.7 m, thickness 7.
0. crm, heat-fusible nonwoven fabric tapes with an apparent porosity of 0.75 are abutted against each other in the tube axis direction, and the abutting portions of the outer layer tapes do not overlap with the abutting portions of the inner layer, 2. It was shaped into a tube consisting of layers of tape.

Furthermore, on the outside of this, a width 3 made of the same heat-fusible fiber as above is provided.
A heat-fusible nonwoven fabric tape measuring 8.2 mm, 150 μm thick, and having an apparent porosity of 0.40 was wound around the tube with its side edges abutting each other in the circumferential direction.

Next, this three-layer nonwoven fabric tape was passed through a heater equipped with a 160° C. hot plate to uniformly heat the entire nonwoven fabric tape to obtain a support tube according to the present invention.

The support tube obtained in this way maintains a porous structure as a whole, with no non-porous parts, a uniform inner diameter, a flat inner surface, and no fuzz. There wasn't.

- After applying 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 the inner surface of this support tube to a thickness of 300 μm, it is immersed in water to coagulate the cellulose acetate, A reinforced tubular permeable membrane was obtained.

This reinforced tubular permeable membrane was inserted into a perforated stainless steel pipe with an inner diameter of 13.0 mm, and while water colored with red ink was circulated inside the tubular permeable membrane, the internal pressure was increased to 50 kg/a + I, and then the atmospheric pressure I returned it to . Similarly, after repeating this pressurizing operation 100 times, the reinforced tubular permeable membrane was taken out from the stainless steel tube and the membrane surface was observed in detail, but no abnormality was observed.

In addition, 5 layers cm were added in the reinforced tubular permeable membrane obtained in the same manner.
Negative pressure of Hg was applied for 3 minutes, but no peeling of the membrane occurred.

Example 2 Pulp fibers made of polypropylene fibers and polyethylene are blended at a weight ratio of 2:3. Width 37, 7 x*
A heat-fusible nonwoven fabric tape having a thickness of 100 μm and an apparent porosity of 0.65 was shaped into a tube by abutting their side edges against each other in the tube axis direction. Furthermore, on the outside of this, a heat-fusible nonwoven fabric tape made of the same heat-fusible composite fiber as in Example 1, having a width of 38.4 mm, a thickness of 150 μm, and an apparent porosity of 0.40, was placed against the edges in the tube axis direction. The inner layer tape was placed along the abutting portion of the inner layer so as not to overlap with the abutting portion. Then,
This two-layer nonwoven fabric tape was heated as a whole with a hot plate at 160° C. in a heater in the same manner as in Example 1 to obtain a support tube according to the present invention.

The support tube obtained in this way maintains a porous structure as a whole, with no non-porous parts, and has a uniform inner diameter and a flat inner surface.
There was no fluff.

Using this support tube, a reinforced tubular permeable membrane was manufactured in the same manner as in Example 1, and after repeating the same pressurizing operation, the membrane surface was observed in detail, but no abnormalities were observed. Ta. Furthermore, negative pressure of 5 cmHg was applied for 3 minutes to the reinforced tubular permeable membrane obtained in the same manner, but no peeling of the membrane occurred.

Comparative Example A heat-fusible nonwoven fabric tape made of the same heat-fusible fibers as in Example 1, with a width of 28.0 fins, a thickness of 300 μm, and an apparent porosity of 0.41, was overlaid on the mandrel to give a width of 1.511 mm. It was wrapped in a spiral. Next, while rotating and advancing this, an ultrasonic horn with a frequency of 15 KHz is pressed against the overlapping portion, and 4. Thermal welding was carried out at a rate of 0m/min to obtain a support tube in which the overlapped portions were welded.

Fuzziness of fibers of 0.05 to 31 m was observed on the inner surface of the obtained support tube, and a step with a thickness of 410 μm was formed at the welded portion where the tapes were overlapped.

Using this support tube, a reinforced tubular permeable membrane was manufactured in the same manner as in Example 1, and after repeating the same pressurizing operation, the membrane surface was observed in detail. Many cracks were observed in the support tube, and many spots where red ink had passed were also observed on the inner surface of the support tube other than the welded parts. When these spots were observed with an electron microscope, they were found to be pinholes caused by fuzz on the inner surface of the support tube. It was confirmed that there is.

[Brief explanation of the drawing]

FIG. 1 is a plan view for explaining the present invention in detail, FIG. 2 is a front view thereof, and FIG. 3 is a partially enlarged view showing an overlapping portion of support tubes according to a conventional method. 11... Tapered pipe, 12... First tape, 14
...Second tape, 16...Abutment part of first tape, 17...Abutment part of first tape, 18
...heater, 19...support tube, 20...mandrel.

Claims (7)

[Claims] (1) A first tape made of a sheet-like fibrous base material containing heat-fusible fibers is formed into a tubular shape by abutting the side edges against each other in the tube axis direction, and further, on top of the tape, the abutted portion is completely After a second tape made of a sheet-like fibrous base material is placed along the side edges so as not to overlap, heating is performed to melt or soften the heat-fusible fibers, and the tapes are bonded to each other. A method for manufacturing a support tube for a permeable membrane, characterized by adhesion. (2) The sheet-like fibrous base material containing heat-fusible fibers is characterized by being made of composite fibers formed by covering at least a portion of the surface of high-melting point thermoplastic resin fibers with a low-melting point thermoplastic resin. A method for manufacturing a support tube for a permeable membrane according to claim 1. (3) A patent claim characterized in that the sheet-like fibrous base material containing heat-fusible fibers is a sheet-like fibrous base material made of a fiber mixture of high-melting point thermoplastic resin fibers and low-melting point thermoplastic resin fibers. A method for producing a support tube for a permeable membrane according to item 1. (4) A first tape made of a sheet-like fibrous base material containing heat-fusible fibers is shaped into a tube by abutting the side edges against each other in the tube axis direction, and further, on top of the tape, the abutted portion is completely A second tape made of a sheet-like fibrous base material is placed along the side edges of the first tape so that they do not overlap, and then heat-fusible fibers are wound or braided and heated to form the first tape. A method for producing a support tube for a permeable membrane, comprising melting or softening the heat-fusible fibers to adhere the tapes to each other and welding the wound heat-fusible fibers to the tape. (5) The sheet-like fibrous base material containing heat-fusible fibers is characterized by being composed of composite fibers formed by covering at least a portion of the surface of high-melting point thermoplastic resin fibers with a low-melting point thermoplastic resin. A method for manufacturing a support tube for a permeable membrane according to claim 4. (6) A patent characterized in that the sheet-like fibrous base material containing heat-fusible fibers is a sheet-like fibrous base material 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 fibers for winding or braiding are characterized in that they are composed of composite fibers formed by covering at least a portion of the surface of high-melting point thermoplastic resin fibers with a low-melting point thermoplastic resin. A method for manufacturing a support tube for a permeable membrane according to claim 4.