JP7358914B2 - Channel material - Google Patents

Description

The present invention relates to a channel material for permeate used in a liquid separation membrane module. In particular, it relates to a channel material for a reverse osmosis separation membrane (hereinafter sometimes referred to as "RO separation membrane") module.

Spiral type liquid separation membrane modules using RO separation membranes have been widely known. Its structure is such that the channel material for the permeate is sandwiched between RO separation membranes, and the channel material for the feed liquid is placed outside the RO separation membrane to form a set of units.The unit is placed around a hollow central tube. It is constructed by winding one or more sets.

When such a liquid separation membrane module is used, a pressure difference of 4 to 5 MPa acts on the feed liquid side and the permeate side, so the channel material is required not to deform even when this pressure is applied.

The following are known as channel materials on the permeate side.

The first conventional technique, which has been known for a long time, is a tricot knitting machine with three reeds, in which two sets of fine-grained thermoplastic synthetic fiber filament yarns are used to knit the ground weave part. A tricot knitted fabric is knitted in which a set of thick thermoplastic synthetic fiber filament yarns is knitted into the needle loop part of the ground weave part to form a ridge part, and the yarns of the tricot knitted fabric are further heat-treated. A channel material is known in which the entire knitted fabric is stiffened by adhesive treatment (Patent Document 1).

As a comparative product described in Patent Document 1, a channel material was prepared by knitting two sheets of osa/tricot into a double denby knitted fabric using a mixed yarn of thermoplastic synthetic fiber filament yarns and heat-sealing the fabric. However, this comparative product had the problem of high flow resistance and the inability to reduce the thickness. Therefore, the invention of Patent Document 1 uses a tricot knitting machine with three reeds to further knit yarns that are thicker than the yarns that make up the ground weave part, thereby maintaining the flow path structure for a long period of time without impairing permeate productivity. This provides a channel material that can be maintained.

Furthermore, as a second prior art, a channel material has been proposed that is made of a warp knitted material knitted from single-component resin monofilaments having a diameter of 40 to 150 μm. (Patent Document 2).

This Patent Document 2 discloses that the warp knitted material constituting the channel material is knitted with a single component resin monofilament, thereby providing a channel material with excellent recyclability.
Furthermore, as a third prior art, a net made of parallel cross-shaped woven or knitted fabric has been proposed that utilizes the rigidity of resin monofilaments and does not undergo heat fusion or resin impregnation steps (Patent Document 3).

This Patent Document 3 discloses that by making the structure of the channel material into a cross-shaped structure using monofilament, the channel resistance is extremely suppressed, the porosity of the channel cross section is increased, and the separation performance is improved. To provide a channel material that allows water to flow in all directions without forming an abnormal stagnation part inside the channel.

Japanese Unexamined Patent Publication No. 60-19001 Japanese Patent Application Publication No. 2003-117355 Japanese Patent Application Publication No. 2010-94659

In the first conventional technology, in order to have a lower flow resistance and thinner thickness than a channel material made by knitting a double denby knitted fabric of two-layered tricot and heat-sealing it, the tricot has three-woven fabric. Using a knitting machine, two sets of fine-grained thermoplastic synthetic fiber filament yarns are used to knit the base fabric part, and one set of thick-gauge thermoplastic synthetic fiber filament yarns is knitted in the needle loop part of the base fabric part. However, all of the disclosed yarns are essentially multifilament yarns, and in addition to two sets of fine yarns, a thick yarn is knitted. Therefore, although the ridges can be made high, it is difficult to reduce the overall thickness of the tricot knitted fabric because the thick yarn is also knitted into the ground structure.

In addition, in the second conventional technology, in order to obtain a channel material with excellent recyclability, the warp-knitted fabric is knitted only from monofilament made of a single component resin. When incorporated into a liquid separation membrane module as a material, liquid separation membranes such as RO membranes are easily damaged, and countermeasures such as making the liquid separation membrane thicker are required to make it durable for long-term use.

In addition, in the third prior art, monofilaments and multifilaments are used to create a net made of cross-shaped woven or knitted fabric, but since each of the disclosed filaments is a filament made of a single component, it may cause misalignment, etc. It was difficult to maintain a simple and uniform channel material structure.

In view of the problems of the prior art, the present invention ensures a liquid flow path structure similar to that of a conventional thick flow path material even with a thin flow path material, and also enables the flow path to be formed in the process of fabricating a liquid separation membrane module. It is an object of the present invention to provide a channel material that has rigidity that prevents the material from being bent and wrinkled, and whose thickness does not change much even when high pressure of a stock solution is applied through an RO separation membrane during use.

In order to solve this problem, the present invention consists of one of the following configurations.

(1) A tricot knitted fabric formed by knitting synthetic fibers, the tricot knitted fabric being composed of at least two types of synthetic fibers with different finenesses, one of the synthetic fibers being a monofilament and the other being two or more types. A channel material for liquid separation membrane modules that is composed of multifilament polymers.

(2) The liquid separation membrane module according to (1) above, wherein the multifilament is selected from a mixed fiber yarn, a core-sheath type composite fiber, and a side-by-side type composite fiber.

(3) The liquid separation membrane according to (1) or (2) above, wherein the multifilament is a core-sheath composite fiber yarn, and the sheath component is composed of a component having a lower melting point or softening point than the core component. Channel material for modules.

(4) The channel material for a liquid separation membrane module according to any one of (1) to (3) above, wherein the multifilament is heat-sealed.

(5) The channel material for a liquid separation membrane module according to any one of (1) to (4) above, wherein the synthetic fiber A having a smaller fineness among the at least two types of fibers having different finenesses is 50 dtex or less. .

(6) The channel for a liquid separation membrane module according to any one of (1) to (5) above, wherein the synthetic fiber B having a larger fineness among the at least two types of fibers having different finenesses has a fineness of 33 to 90 dtex. Material.

(7) The channel material for a liquid separation membrane module according to any one of (1) to (6) above, wherein the synthetic fiber A having the smaller fineness is a monofilament.

(8) The channel material for a liquid separation membrane module according to any one of (1) to (7) above, wherein the synthetic fiber B having a larger fineness is a multifilament.

(9) A liquid separation membrane module having the channel material for a liquid separation membrane module according to any one of (1) to (8) above.

(10) The liquid separation membrane module according to (9) above, wherein the liquid separation membrane module further includes a reverse osmosis separation membrane, and the channel material is arranged on the permeation side of the reverse osmosis separation membrane.

According to the present invention, even with a thin channel material, the same liquid channel structure as a conventional thick channel material is ensured, and the channel material does not bend and wrinkle during the processing process into a liquid separation membrane module. It is possible to provide a channel material that has a rigidity that does not deteriorate and that does not change in thickness even when high pressure of the stock solution is applied through an RO separation membrane during use.

FIG. 1 is a schematic perspective view showing an example of a spiral type liquid separation membrane module. FIG. 2 is an enlarged photograph showing the shape of the fibers viewed from the convex portion side of the tricot knitted channel material for explaining the long side of the opening formed on the inner surface side of the double loop. FIG. 3 is a conceptual cross-sectional view of the tricot knitted channel material for explaining the measurement site of the channel (groove width, groove depth).

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated.

The channel material for a liquid separation membrane module of the present invention is a tricot knitted fabric formed by knitting synthetic fibers, the tricot knitted fabric being composed of at least two types of synthetic fibers having different finenesses, One of them is a monofilament, and the other is a multifilament made of two or more types of polymers.

The tricot knitted fabric has a base texture and a convex portion, and the convex portion is formed by double loops. A tricot knitting machine with at least two reeds is used to form the double loop, and at least two sets of warp threads made of synthetic fibers are used. Among these two sets of warp threads, at least one set of warp threads is used as back threads to form the needle loop portion of the ground weave, and at least one other set of warp threads is knitted as front threads into the needle loop portion of the ground weave to create a convex shape. It forms a part.

In the present invention, at least two types of synthetic fibers having different finenesses are usually used for at least two sets of warp yarns of the tricot knitted fabric. Among at least two sets of warp yarns made of synthetic fibers, synthetic fiber B (hereinafter referred to as synthetic fiber B) having a larger fineness is used as the front yarn, and synthetic fiber A having a smaller fineness (hereinafter referred to as synthetic fiber A) is used as the front yarn. ) is preferably used for the back yarn because the groove depth relative to the thickness can be further increased. As a result, even when the thickness of the channel material is made thinner than before, it is possible to maintain a liquid channel structure similar to that of a conventional thick channel material.

One of the above two types of synthetic fibers is a monofilament, and the other is a multifilament made of two or more types of polymers.

Furthermore, by using monofilament as the synthetic fiber that constitutes the knitted fabric, it is possible to ensure rigidity even when the fabric is made thin. When comparing multifilament and monofilament of the same fineness, when pressure is applied to the multifilament, which is an aggregate of many fine monofilaments, in a direction perpendicular to the length direction of the fibers, the multiple fine monofilaments spread out laterally and form a long, thin tape. monofilament, which is made of a single fiber, undergoes compressive deformation due to pressure, but does not deform like multifilament, so its thickness when subjected to pressure load There are few changes.

Further, the two or more types of polymers in the multifilament made of two or more types of polymers used in the present invention may be two or more types of polymers with different chemical structures, or at least some of them may have a common chemical structure. It may be a combination of two or more types of polymers that have different physical properties such as melting point and softening point by introducing other structural units to form a copolymer. As for the former, combinations having different melting points or softening points as a result of different chemical structures are preferable. Preferred examples of the latter include, for example, a combination of polyethylene terephthalate and a copolymerized polyethylene terephthalate copolymer having a lower melting point or softening point than polyethylene terephthalate. In the present invention, from the viewpoint of heat-sealing adhesion and processability, which will be described later, it is preferable to use a copolymer that has a common chemical structure in at least a part thereof, and that also incorporates other structural units. A combination of two or more types of polymers having different physical properties such as melting points is preferred.

As the multifilament made of two or more types of polymers used in the present invention, any of mixed yarns, core-sheath type composite fibers, and side-by-side type composite fibers can be used. The blended yarn is a blend of two or more individual yarns made of different polymer materials, such as a blended yarn that is a mixture of a single yarn made of polymer A and a single yarn made of polymer B. A core-sheath composite fiber is a multifilament in which a single yarn is composed of a core component and a sheath component, and a side-by-side composite fiber is a multifilament in which a single yarn is composed of two or more types of polymers side-by-side. It is a filament. Among these, a core-sheath composite fiber yarn is preferred, and it is more preferred that the sheath component of the core-sheath composite fiber yarn has a melting point or softening point lower than that of the core component. In the channel material for a liquid separation membrane module of the present invention, the multifilament is thermally fused to ensure a liquid channel structure and to have excellent rigidity during the processing process into a liquid separation membrane module. , and is preferable because it becomes possible to further suppress thickness changes even if high pressure of the stock solution acts through the RO separation membrane during use. For the same reason, even when using mixed yarns or side-by-side composite fibers, it is preferable to use a combination of two or more polymers that have different melting points or softening points.

By doing this, the knitted tricot fabric is heat-set to melt or soften the components with low melting points or softening points, and adhere and fuse with other fibers to solidify, thereby forming the knitted fabric. It becomes possible to fix fibers together.

Furthermore, among at least two types of fibers with different finenesses used in the present invention, synthetic fiber A, which is a synthetic fiber with a small fineness, is 50 dtex or less, and synthetic fiber B, which is a synthetic fiber with a large fineness, is 33 to 90 dtex. is preferred. By doing so, it is possible to ensure rigidity and liquid channel structure even if the channel material is made thin. In addition, in the above, it is assumed that synthetic fibers A and B have a relationship of fineness of synthetic fiber A < fineness of synthetic fiber B, so if synthetic fiber B is 33 dtex, synthetic fiber A is 33 dtex. Selected below. Preferably, the synthetic fiber A has a length of 10 dtex or more from the viewpoint of ease of handling during processing and prevention of thread breakage.

In the present invention, it is preferable that the synthetic fiber A having the smaller fineness is a monofilament, since the channel material can be made even thinner.

Further, it is preferable that the synthetic fiber B having a larger fineness is a multifilament, since the tricot knitted fabric can have more heat fusion points and can further improve rigidity and pressure resistance.

In the present invention, the most preferable embodiment is to use a monofilament as the synthetic fiber A to form the back yarn, and to use a multifilament as the synthetic fiber B to form the front yarn. As a result, even if the channel material is thin, it can ensure the same liquid channel structure as conventional thick channel materials, and it also prevents the channel material from bending and causing wrinkles during the processing process into liquid separation membrane modules. The effect of the present invention of having rigidity that is not found in other materials can be very clearly exhibited.

In the tricot knitted channel material of the present invention, the distance between the convex portions (hereinafter referred to as groove width) is preferably within the range of 80 to 330 μm. It is preferable that the groove width is 80 μm or more because it can lower the water flow resistance of the permeate, and it is preferable that the groove width is 330 μm or less because it prevents the RO separation membrane from collapsing. More preferably, the thickness is 150 to 300 μm.

The above groove width is determined by the well density of the tricot knitted fabric, the fineness of the synthetic fiber forming the double loop, the bulge of the double loop, the course density, etc. It is preferably within the range of book/2.54 cm. It is preferable that the well density of the tricot knitted fabric is 35 lines/2.54 cm or more because the distance between the double loops becomes narrow and the RO separation membrane does not drop. It is preferable that the distance is 2.54 cm or less because the distance between the double loops can ensure a necessary width and the water flow resistance of the permeated liquid can be kept low. More preferably, the length is 37 to 60 lines/2.54 cm.

Further, the course density of the tricot knitted fabric is preferably within the range of 40 to 65 lines/2.54 cm. Since the course density of the tricot knitted fabric is 40 lines/2.54cm or more, it is possible to suppress the decrease in thickness even when the pressure acting on the RO separation membrane is applied to the tricot knitted fabric that is the channel material. preferable. Further, by setting the course density of the tricot knitted fabric to 65 lines/2.54 cm or less, it is possible to suppress the basis weight of the tricot knitted fabric, and it is possible to suppress an increase in product weight and cost. More preferably, the course density is within the range of 45 to 60 lines/2.54 cm.

Examples of the structure of the tricot knitted fabric used in the present invention include half knitting, reverse half knitting, and queen's cord knitting, with reverse half knitting and double denby weaving being preferred. In particular, by employing the double denby weave, the number of threads constituting the double warp knitted ground weave can be reduced, so the flow path for permeated water can be widened. Further, by forming both the front and back sides with a double Denby structure, the distance from loop to loop on both the front and back sides is short and the dimensional stability is excellent, which is preferable. In addition, the distance from loop to loop is short, and even if the knitted fabric is constructed using a small amount of fiber, it can withstand water pressure during use.

Further, it is preferable to use a double Denby structure with closed eyes. There are two ways to form loops: closed loops and open loops. By closing loops, the bulge of the synthetic fiber that forms the double loops can be reduced, so the distance between the double loops should be as wide as necessary. This is preferable because it can ensure that the water flow resistance of the permeated liquid can be kept low.

The synthetic fibers forming these double loops are preferably heat-fused. By having a structure in which synthetic fibers are heat-fused and solidified, the fibers of the tricot knitted fabric are integrated with each other even when water pressure is applied during use, so there will be no deformation or damage, and the convex parts of the tricot knitted fabric will not be damaged. This is preferable because there is little deformation and the water flow resistance of the permeated liquid can be maintained low.

Examples of synthetic fibers used in the tricot knitted fabric used in the present invention include polyamide fibers such as nylon 6 and nylon 66, polyester fibers, polyacrylonitrile fibers, polyolefin fibers such as polyethylene and polypropylene, and polyvinyl chloride fibers. It is possible to select the synthetic fiber A and the synthetic fiber B as appropriate. In particular, polyester fibers are preferably used because they have sufficient strength even in the hydraulic environment during use and are less likely to elute components into the permeate.

A multifilament composed of two or more types of polymers will be explained below.

Taking polyester fiber as an example, it is preferable that the fiber is composed of two or more types of polyester having different melting points or softening points. This is because the tricot knitted fabric is composed of polyester with a high melting point (hereinafter abbreviated as polyester H) and polyester with a low melting point (hereinafter abbreviated as polyester L), so even in the water pressure environment during use, polyester L This is because the fibers can be strongly integrated with each other by having a structure in which the polyester H is heat-fused and solidified with each other.

Examples of embodiments in which the fiber is composed of two or more types of polyesters having different melting points or softening points include the use of mixed yarns made of filament yarns, core-sheath type or side-by-side type composite fibers. Compared to a mixed fiber yarn in which polyester H and polyester L are mixed at the single filament level, the filament single yarn is a core-sheath composite yarn composed of polyester H and polyester L, and the sheath component has a higher melting point than the core component. Alternatively, a material composed of components having a low softening point is preferable because it can increase the melting point for heat-sealing.

Since the liquid separation membrane module is sometimes washed with hot water before use, the melting point or softening point of the polyester L needs to be normally 80°C or higher, and may be 110°C or higher, to the extent that it can withstand such washing. preferable.

In the present invention, the melting point difference between polyester H and polyester L (in the present invention, the difference in softening point when the polyester H does not have a melting point but has a softening point is also referred to as a melting point difference) is at least 10°C, preferably 20°C or more. good. Since the melting point difference is 20° C. or more, it becomes easy to fuse only the polyester L and solidify each other while maintaining the shape of the convex portion. There is no upper limit to the melting point difference as long as a tricot knitted channel material that can provide a practical liquid separation membrane module is obtained, but 180°C is realistic.

Examples of the polyester H include polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, etc. in which alkylene terephthalate is the main repeating material.

As the polyester L, a difference in melting point can be created by copolymerizing the polyester mainly containing the above-mentioned alkylene terephthalate. Components to be copolymerized include isophthalic acid, phthalic anhydride, diethylene glycol, etc., and those that can provide a melting point difference of 10° C. or more are appropriately selected and used.

The composite ratio of polyester H and polyester L may be selected as appropriate, but if the weight ratio is within the range of 50:50 to 95:5, sufficient heat fusion can be ensured, and fiber strength and shrinkage rate are also required. It is preferable because it can be made within a range. More preferably, the ratio is 70:30 to 90:10.

In addition, for other fibers such as polyamide fibers, as with the above polyester fibers, mixed yarns made of two or more types of fibers with different melting points or softening points, or core-sheath type or side-by-side type composite fibers can be used. I can do it.

As for the monofilament to be combined with the multifilament composed of two or more types of polymers as described above, it is preferable that at least a portion thereof has a common chemical structure from the viewpoint of adhesion when thermally bonded. Among them, a polyester monofilament is used as the synthetic fiber A, and two or more types of polymers with different melting points or softening points are used as the synthetic fiber B, and the multifilament has a core-sheath structure in which polyester with a low melting point or softening point is arranged on the sheath side. That is most preferable.

The tricot knitted fabric having the double denby structure obtained in this manner is heat-set to heat-fuse the fibers to each other, thereby obtaining the tricot knitted fabric channel material of the present invention. When the synthetic fiber used is a core-sheath composite fiber yarn, it is preferable that the sheath component is composed of a component with a lower melting point or softening point than the core component, and by including a component with a lower melting point or softening point, it is heat-settable. This is preferable because the fibers can be easily thermally bonded to each other. The method of heat setting is not particularly limited as long as the double loop specified in the present invention can be obtained, such as an ordinary pin tenter dryer or cylinder dryer, but a pin tenter dryer whose width can be easily set is preferably used. When using synthetic fibers with a melting point or softening point of 170 to 240°C, the temperature of the pin tenter dryer should be set at least 5°C higher than that, preferably at least 10°C higher to prevent thermal fusion between the fibers. This is preferable because it makes it possible to proceed with the process. The upper limit is preferably set as high as 30°C or less from the viewpoint of economics and the ability to stably control the temperature of the dryer.

The tricot knitted fabric thus obtained can be suitably used as a channel material for liquid separation membrane modules, and is especially suitable for liquid separation membrane modules for pure water, ultrapure water, water softening, wastewater recovery, valuable resource recovery, etc. It can be used for.

The liquid separation membrane channel material of the present invention can ensure a high salt removal rate even when the raw solution acts at a high pressure of 4 to 5 MPa through the RO separation membrane during use. It can be particularly suitably used in liquid separation membrane modules for freshwater purification. The liquid separation membrane module preferably has a structure in which at least the reverse osmosis separation membrane and the permeation side channel material are wound around a central pipe. That is, a spiral type liquid separation membrane module is preferable. FIG. 1 is a schematic perspective view showing an example of a spiral type liquid separation membrane module. The liquid separation membrane module 6 has a permeate side channel material 1 sandwiched between two RO separation membranes 2. Further, on the opposite side of the RO separation membrane 2 from the permeate side channel material 1, a feed liquid passage material (supply liquid side passage material 3) is arranged. A mesh can be used as a channel material for the supply liquid. As a result, a unit is completed in which the feed liquid side channel material/RO separation membrane/permeate side channel material/RO separation membrane is arranged in this order. One or more sets of the units are wound around a hollow central pipe 5 having a water collection hole 4 to form a liquid separation membrane module. A case may be provided at the outermost part of this liquid separation membrane module. It is preferable to use the tricot channel material of the present invention as a channel material on the permeate side for forming a channel through which the permeate passes.

The present invention will be described below with reference to Examples, but the present invention is not necessarily limited thereto. The methods for measuring various properties and the criteria for comprehensive evaluation used in this example were as follows.

[Method of measuring characteristics]
Among the following measurement methods, unless otherwise specified, sample preparation and measurements were performed under the standard conditions of JIS-L-0105 (2006) (20±2° C., relative humidity 65±4%).

(1) Density (book/2.54cm)
In accordance with JIS-L-1096 (2010) Annex F, the number of wells and the number of courses of the tricot channel material were measured using a densimeter.

(2) Thickness (mm)
The thickness of the tricot knitted channel material was measured using a dial gauge (dial gauge No. 1109S-10 manufactured by Mitutoyo Co., Ltd., measuring element No. 101117 diameter 10 mmφ, stand No. 7002). The thickness of the tricot knitted channel material is the thickness of the tricot knitted channel material including the ground structure and double loops of the tricot knitted channel material.

(3) Bending resistance Measured in the well direction and course direction of the tricot channel material according to JIS-L-1096 (2010) A method (45° cantilever method).

(4) Channel groove width (μm) and channel groove depth (μm)
Observation was made at a magnification of 100 times using a digital microscope VHX-5000 manufactured by Keyence Corporation, and the groove width and groove depth of the channel were measured. To measure the groove depth of the channel, the channel material was cut perpendicular to the stitch direction, and the cross section was observed at the same magnification. The groove width of the channel and the groove depth of the channel were defined by the method shown in FIGS. 2 and 3. That is, the groove width of the flow path is the groove width 7 of the flow path formed between adjacent double loops 8, and corresponds to the water passage portion 9 of the permeate. The groove depth of the channel is 10, which is the depth from the top of the double loop 8 to the upper part of the ground structure 11 of the tricot knitted channel material. For the measurement, three points were randomly extracted from the entire width, each measurement was performed five times, and the results were averaged.

(5) Pressure resistance test The front and back surfaces of the tricot channel material were sandwiched between top plates at room temperature, pressurized at a pressure of 2.4 MPa for 30 minutes, and the thickness before and after pressurization was measured in the same manner as in (2) above. The rate of change in thickness was calculated from
Thickness change rate (%) = [(thickness after pressure/thickness before pressure)] x 100... (Formula 1)
In addition, in the above, the thickness after pressurization refers to the thickness measured 3 minutes±2 minutes after pressure is released after pressurization.

[Example 1]
Polyethylene terephthalate (melting point: 255°C) is used as the core and polyethylene terephthalate-based low melting point polyester (melting point: 225°C) is used as the front yarn. A 22 decitex monofilament consisting of only 255°C) was used as the backing yarn, and knitted into a double denby weave with a closed loop on a 32 gauge (number of needles per unit length of the knitting machine) tricot knitting machine with two reeds. .

At that time, the front yarn was fed in with a runner length of 130 cm/R, and the back yarn was fed in with a runner length of 117 cm/R to form a knitted fabric having a ground texture and convex portions. Thereafter, heat setting was performed using a pin tenter processing machine set at 245°C to heat-fuse the core-sheath composite fiber yarns, resulting in a tricot knitted fabric with a well density of 39 threads/2.54 cm and a course density of 52 threads/2.54 cm. A channel material was obtained.

[Comparative example 1]
A multifilament blend yarn (36 filaments, 84 dtex) made by blending polyethylene terephthalate filament (melting point: 255°C) with polyethylene terephthalate low melting point polyester filament (melting point: 225°C) is used as the front yarn, and polyethylene A regular yarn (18 filaments, 56 decitex) consisting only of terephthalate (melting point: 255°C) was used as the backing yarn, and knitted into a double denby weave with closed stitches using the same 32 gauge tricot knitting machine as in Example 1 with two reeds. did.

At that time, the front yarn was fed in with a runner length of 131 cm/R, and the back yarn was fed in with a runner length of 121 cm/R to form a knitted fabric having a ground texture and convex portions. Thereafter, heat setting was performed in the same manner as in Example 1, and the multifilament mixed yarn was heat-sealed to form a tricot knitted channel material with a well density of 38 threads/2.54 cm and a course density of 51 threads/2.54 cm. I got it.

[Comparative example 2]
A core-sheath composite fiber yarn (24 filaments, 56 dtex) with polyethylene terephthalate (melting point: 255°C) as the core and polyethylene terephthalate-based low melting point polyester (melting point: 225°C) as the sheath was used as the front yarn; A regular yarn (18 filaments, 56 decitex) consisting only of terephthalate (melting point: 255°C) was used as the backing yarn, and knitted into a double denby weave with closed stitches using the same 32 gauge tricot knitting machine as in Example 1 with two reeds. did.

At this time, a core-sheath composite fiber yarn with a runner length of 124 cm/R is fed into the front reed as a front yarn, and a monofilament with a runner length of 119 cm/R is fed into the back reed as a back yarn to separate the ground texture and convex portions. A knitted fabric having the following properties was formed. Thereafter, heat setting was performed in the same manner as in Example 1 to heat-seal the core-sheath composite fiber yarns to form a tricot knit with a well density of 39.3 threads/2.54 cm and a course density of 53.5 threads/2.54 cm. Ground flow channel material was obtained.

[Example 2]
A multifilament blend yarn (36 filaments, 84 decitex) made by blending polyethylene terephthalate filaments (melting point: 255 degrees Celsius) with polyethylene terephthalate-based low melting point polyester filaments (melting point: 225 degrees Celsius) is used as the front yarn. Using a 22 decitex monofilament consisting only of melting point: 255℃) as the backing yarn, it is knitted into a closed double denby weave using a 32 gauge (number of needles per unit length of the knitting machine) tricot knitting machine with two reeds. did.

At that time, the front yarn was fed in with a runner length of 130 cm/R, and the back yarn was fed in with a runner length of 117 cm/R to form a knitted fabric having a ground texture and convex portions. After that, the multifilament mixed fiber yarn was heat-sealed by heat setting with a pin tenter processing machine set at 245°C, and the well density was 37.3 pieces/2.54 cm, and the course density was 51.3 pieces/2.54 cm. A tricot knitted channel material was obtained.

[Example 3]
Using the same knitted fabric as in Example 2, it was heat-set with a pin tenter processing machine set at 245°C to heat-seal the multifilament mixed yarn, resulting in a well density of 44.8 threads/2.54 cm and a course density. A tricot knitted channel material having a length of 52.0 pieces/2.54 cm was obtained. Note that processing was performed by increasing the slack of the knitted fabric during heat setting so that the well density was higher than that in Example 2.

[Example 4]
Using the same knitted fabric as in Example 2, it was heat-set with a pin tenter processing machine set at 245°C to heat-seal the multifilament mixed yarn, resulting in a well density of 53.0/2.54 cm and a course density. A tricot knitted channel material having a length of 52.8 pieces/2.54 cm was obtained.

As shown in Table 1, although the thickness of Examples 1 and 2 was significantly reduced compared to Comparative Examples 1 and 2, the ratio of the groove depth to the thickness of the channel material was The lower value of degree and pressure resistance show values equivalent to those of the comparative example, and the channel material has a rigidity that does not bend and wrinkle during the processing process into a liquid separation membrane module, and , is a channel material whose thickness does not change much even when the high pressure of the stock solution is applied through the RO separation membrane during use. In addition, in Examples 3 and 4, even though the thickness was reduced compared to Comparative Example 1, the ratio of the groove depth to the thickness of the channel material and the pressure resistance were the same, and even though they were thinner, This channel material has the same fluid channel structure as conventional thick channel materials.

1: Channel material on permeate side 2: RO separation membrane 3: Channel material on feed liquid side 4: Water collection hole 5: Center pipe 6: Liquid separation membrane module 7: Channel groove width 8: Double loop 9: Permeated liquid passage portion 10: Channel depth 11: Texture of tricot knitted channel material

Claims (7)

A tricot knitted fabric formed by knitting synthetic fibers, the tricot knitted fabric being composed of at least two types of synthetic fibers with different finenesses, one of the synthetic fibers being a monofilament, and the other having a different melting point or softening point. Composed of multifilaments made of two or more types of polymers ,
Of the at least two types of fibers with different finenesses, the synthetic fiber A with the smaller fineness is 10 to 50 dtex, and the synthetic fiber B with the larger fineness is 33 to 90 dtex,
A channel material for a liquid separation membrane module , in which the multifilament is heat-sealed . The channel material for a liquid separation membrane module according to claim 1, wherein the multifilament is selected from a mixed fiber yarn, a core-sheath type composite fiber, and a side-by-side type composite fiber. The channel material for a liquid separation membrane module according to claim 1 or 2, wherein the multifilament is a core-sheath composite fiber yarn, and the sheath component is composed of a component having a lower melting point or softening point than the core component. The channel material for a liquid separation membrane module according to any one of claims 1 to 3 , wherein the synthetic fiber A having a smaller fineness is a monofilament. The channel material for a liquid separation membrane module according to any one of claims 1 to 4 , wherein the synthetic fiber B having a larger fineness is a multifilament. A liquid separation membrane module comprising the channel material for a liquid separation membrane module according to any one of claims 1 to 5 . 7. The liquid separation membrane module according to claim 6 , further comprising a reverse osmosis separation membrane, and wherein the channel material is disposed on the permeation side of the reverse osmosis separation membrane.