Flow path material for liquid separation device

Abstract

To provide a passage material for a liquid separation device which is hardly crushed when high pressure is applied to a passage material and has little decrease in a flow rate.SOLUTION: A passage material for a liquid separation device is made of tricot fabric including thermal plasticity sheath-core composite fibers composed of two kinds of polyester resin having different melting points and softening points. In the passage material for a liquid separation device, a high melting point component is arranged at a core part and a low melting point component is arranged at a sheath part in the thermal plasticity sheath-core composite fibers, the tricot fabric is formed by mutually adhering the thermal plasticity sheath-core composite fibers of tricot knitted fabric organized by using the thermal plasticity sheath-core composite fibers to front yarns and back yarns to be rigid by knitting machine of two sheets of reeds, the wale density thereof is 50 to 68 wales / 2.54 cm, and the course density is 50 to 68 courses / 2.54 cm, and a change rate of the thickness of the tricot fabric before and after press is 14% or less when the tricot fabric undergoes hot press at 90°C and with 7.0 MPa for three minutes.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a flow path material for a liquid separation device that supports the back surface side of a semi-permeable membrane that is pressurized with a stock solution in a liquid separation device used for concentrating and separating various liquids.

Background Art

[0002] As a liquid separation device using a semi-permeable membrane, generally, the semi-permeable membrane is formed in a cylindrical shape, and a flow path material that forms a flow path for passing the permeate inside the membrane by applying pressure from the outside is inserted, and the end of the flow path material is fixed to a hollow shaft and wound. A typical one uses a spiral-type liquid separation membrane module. In such a liquid separation membrane module, a stock solution at a high pressure equal to or higher than the reverse osmotic pressure is passed outside the membrane, and the permeate that has passed through the membrane is taken out through the inside of the membrane. Since the cylindrical separation membrane is pressurized from the outside at a high pressure, the flow path material inserted as the flow path for the permeate is crushed, deteriorating the liquid flow. Therefore, generally, the flow path material itself is rigidified so that it can withstand deformation even when pressurized from the outside inside the separation membrane. Such a liquid separation membrane module has been put into practical use as a water treatment device for boiler water pretreatment, wastewater reuse, seawater desalination, and production of ultrapure water.

[0003] Conventionally, fabrics such as woven fabrics and knitted fabrics have been used for such a flow path material for permeated water, and particularly those having a structure with fine grooves on the surface have been used. These fabrics were impregnated with an epoxy resin, a melamine resin, or the like to be rigidified so as not to be deformed by the pressure applied to the stock solution through the membrane. In that case, in order not to be crushed even at a high pressure, it was necessary to adhere resin up to nearly half of the weight of the fabric. However, problems have occurred due to elution of the impregnated resin in applications that require high-purity permeated water or in applications that process high-temperature liquids. In particular, when the stock solution to be treated is a food liquid or a medical liquid, it is required to be sterile. Therefore, in order to prevent contamination by miscellaneous bacteria before or after the start of membrane separation treatment, sterilization with hot water is performed, and at that time, elution of the resin impregnated in the flow path material has been a problem.

[0004] In order to solve the above problems, there has been proposed a flow path material that is rigidified by heat-treating a knitted fabric formed by knitting a thermoplastic synthetic fiber composed of a low melting point component and a high melting point component using a three-needle bar warp knitting machine, and forming ridges with a thermoplastic synthetic fiber having a fineness 1.2 times or more thicker than the fibers constituting the ground weave (Patent Document 1). However, since this flow path material uses a thermoplastic synthetic fiber with a thin fineness and a thermoplastic synthetic fiber with a thick fineness using three needle bars, there are problems such as low productivity and high costs. There is also a problem that the thickness of the flow path material cannot be reduced.

[0005] In order to solve the problems of this Patent Document 1, there have been proposed a technique of forming a back half structure with a warp knitted fabric composed of core-sheath composite fibers using two needle bars (Patent Document 2), and a technique of setting the well density of a warp knitted fabric composed of core-sheath composite fibers with a total fineness of 30 to 90 dtex to 35 to 45 pieces / 2.54 cm and the course density to 35 to 55 pieces / 2.54 cm (Patent Document 3).

[0006] In addition, since the osmotic pressure of sodium chloride with a concentration of 3.5 mass% in seawater is 2.8 MPa, considering the increase in salt concentration by the cross-flow method in desalination by reverse osmotic pressure, it is necessary to apply a pressure of at least 4 to 6 MPa inside the spiral element. In that case, the support on which the membrane is coated may sink, and there is a concern that the flow path material for permeated water may be crushed by long-term pressurization, resulting in a decrease in flow rate. Depending on the operating conditions, a very high pressure of 7.0 MPa or more is applied. Particularly under conditions of 7.0 MPa or more, the flow path material is more likely to be crushed by long-term pressurization.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, both Patent Documents 2 and 3 have the drawback that when used as a flow path material for high-pressure operation, the flow path is blocked by pressure and the flow rate becomes insufficient. Moreover, regarding the above-mentioned three prior documents, in all of them, a thermoplastic core-sheath composite fiber is knitted in a single tricot structure and heat-set to harden the entire tricot fabric, so that even when pressurized at the reverse osmotic pressure required for seawater desalination, the flow path is not blocked and the flow rate does not decrease. However, none of them have compared and studied the maintenance of the cross-sectional area of the flow path under actual reverse osmotic pressure. That is, the crushability of the flow path material under pressure has not been studied. Also, there is a method for inspecting the thickness of the flow path material after pressurization at room temperature, but it is necessary to apply pressure for a long time, and when performing a plurality of inspections, it takes a considerable amount of labor and cost.

[0009] Moreover, when inspecting the crushability at room temperature, since the material used for the flow path material is composed of a thermoplastic polymer and shows a behavior of returning to its original state when the pressure is released, it has been difficult to verify the crushability. Therefore, it has not been possible to easily find the configuration and conditions of a flow path material that is least likely to be crushed and has a small decrease in flow rate when a high pressure is applied to the flow path material.

[0010] The present invention has been made to solve the above problems, and an object thereof is to provide a flow path material for a liquid separation device that is thin in thickness, difficult to be crushed when a high pressure is applied to the flow path material, and has a small decrease in flow rate.

Means for Solving the Problems

[0011] So far, no comparison and study have been made on the maintenance of the cross-sectional area of the flow path and the flow rate at that time under conditions equivalent to those under actual reverse osmotic pressure. The inventor has found a method for easily determining the degree of crushing of a flow path material when it is pressurized at a high pressure for a long time. That is, by measuring the thickness of the flow path material after pressurizing the resin constituting the flow path material for water permeation under conditions above the glass transition temperature and the thickness of the flow path material before pressurization, the ease of crushing can be easily measured. Furthermore, using this method, the configuration and conditions of the flow path material that are least likely to be crushed and result in less reduction in flow rate when a high pressure is applied to the flow path material were found, leading to the present invention.

[0012] That is, an object of the present invention is a flow path material for a liquid separation device made of a tricot fabric containing thermoplastic core-sheath composite fibers composed of two types of polyester resins having different melting points or softening points. In the thermoplastic core-sheath composite fibers, the high melting point component is arranged in the core part and the low melting point component is arranged in the sheath part. The high melting point component is polyethylene terephthalate, and the melting point difference between the two components is 60 °C or more. The tricot fabric is It is a tricot knitted fabric composed only of a front yarn and a back yarn, and the front yarn and the back yarn are the thermoplastic core-sheath composite fibers. , a tricot fabric in which the thermoplastic core-sheath composite fibers are adhered to each other and rigidified. The well density of the tricot fabric is 50 to 68 threads / 2.54 cm, and the course density is 50 to 68 threads / 2.54 cm. When the tricot fabric is heat-pressed at 90 °C and 7.0 MPa for 3 minutes, the change ratio of the thickness of the tricot fabric before and after pressing is 14% or less, which is achieved by a flow path material for a liquid separation device.

[0013] Also, the total fineness of the front yarn and the back yarn of the thermoplastic core-sheath composite fibers constituting the tricot fabric is 80 to 140 dtex, the difference in the runner length between the front yarn and the back yarn is 40 cm or less, and the thickness of the tricot fabric is 0.18 to 0.26 mm is preferably.

[0014] Also, in the thermoplastic core-sheath composite fibers constituting the tricot, it is preferable that the difference in the total fineness between the convex part (front yarn) and the ground tissue part (back yarn) is 20 dtex or less.

[0015] In addition, the ratio of the core part / sheath part of the thermoplastic composite fibers of the front yarn and the back yarn constituting the tricot fabric is preferably 60 / 40 to 80 / 20 on a volume basis.

[0016] The tricot fabric is composed of a ground structure (back yarn) which is a sinker loop part with one of the two reeds, and a convex part (front yarn) which is a needle loop part with the other reed. The ratio (groove width / ridge width) of the width of the part between the convex parts (groove width) to the width of the convex part (ridge width) is preferably 0.4 to 0.8.

Effect of the Invention

[0017] The flow path material for a liquid separation device of the present invention is a flow path material for a liquid separation device that is thin in thickness, has high compression resistance and is not easily crushed when a high pressure is applied to the flow path material, and has little reduction in flow rate. Particularly, even under high pressure conditions of 7.0 MPa or more, Difficult to crush the reduction in flow rate is small.

Embodiments for Carrying out the Invention

[0018] The flow path material for a liquid separation device of the present invention is made of a tricot fabric containing thermoplastic core-sheath composite fibers composed of two types of polyester resins having different melting points or softening points. In the thermoplastic core-sheath composite fiber, the high melting point component is arranged in the core part and the low melting point component is arranged in the sheath part. The melting point difference between the two components is preferably 60 °C or more. In the present invention, the difference from the softening point in the case of having no melting point but having a softening point is also referred to as the melting point difference.

[0019] Preferred polyesters as the above-mentioned low melting point component include those mainly composed of terephthalic acid and ethylene glycol, and as copolymerization components, aliphatic dicarboxylic acids such as oxalic acid, malonic acid, azelaic acid, adipic acid, and sebacic acid, aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and naphthalenedicarboxylic acid, and / or alicyclic dicarboxylic acids such as hexahydroterephthalic acid, and one or a combination of two or more glycols of aliphatic, alicyclic or aromatic diols such as diethyl glycol, polyethylene glycol, propylene glycol, hexanediol, paraxylene glycol, and bis(hydroxyethoxyphenyl)propane, contained in a predetermined ratio, and a copolymerized ester added with oxyacids such as parahydroxybenzoic acid at a ratio of 50 mol% or less as desired is suitable.

[0020] Among the above, in particular, a polyester obtained by adding and copolymerizing isophthalic acid to terephthalic acid and ethylene glycol is suitable. And in such an isophthalic acid copolymerized polyester, a copolymerized product with 10 to 30 mol% of the isophthalic acid component is preferable from the viewpoints of ease of fusion fixation and knitting property. Note that the desired softening point can be adjusted by changing the copolymerization ratio of the above component monomers.

[0021] Examples of the above-mentioned high melting point component include homopolyesters such as polyethylene terephthalate, polybutylene terephthalate, and polytrimethylene terephthalate.

[0022] In the present invention, a core-sheath type composite polyester multifilament using isophthalic acid copolymerized polyester as the low melting point component of the sheath portion and homopolyester as the high melting point component of the core portion is optimal. Further, linear fatty acid diols such as 1,4-butanediol, 1,6-hexanediol, and 1,9-nonanediol may be used together with isophthalic acid. The ratio of the core portion / sheath portion is preferably set to 60 / 40 to 80 / 20 on a volume basis, and particularly preferably set to 68 / 32 to 75 / 25. If it is 60 / 40 to 80 / 20, since the sheath portion, which is the low melting point component, is not too thin, when heat-sealing and fixing, the sheath portions can adhere sufficiently to each other, and since there is a large amount of the core portion, which is the high melting point component, the strength of the fiber is sufficiently exhibited, and it can withstand the pressure even when a high pressure of 7.0 MPa or more is applied and is not easily crushed.

[0023] In the core-sheath type composite multifilament, the total fineness is preferably 30 to 110 dtex, the number of filaments is preferably 10 to 50, and the single filament fineness is preferably 1.0 to 6.2 dtex. When the total fineness is less than 30 dtex, the yarn is too thin and is likely to be crushed without being able to withstand the pressure when pressure is applied from above the loop. When the total fineness exceeds 110 dtex, the thickness of the fabric is large, the fabric becomes hard, and it tends to be unsuitable as a flow path material for permeating water. More preferably, the total fineness is 40 to 60 dtex.

[0024] The tricot fabric in the present invention is a tricot knitted fabric knitted using the thermoplastic core-sheath composite fiber as the front yarn and the back yarn of a two-bar knitting machine, in which the thermoplastic core-sheath composite fibers are adhered to each other and rigidified. The thermoplastic core-sheath composite fibers used for the front yarn and the back yarn may be fibers with the same or different compositions of the core-sheath components, but it is preferable that the melting point or softening point is the same.

[0025] The wale density of the tricot fabric is preferably 50 to 68 per 2.54 cm, and the course density is preferably 50 to 68 per 2.54 cm. When the well density is 50 or more per 2.54 cm and the course density is 50 or more per 2.54 cm, there are many convex portions of the needle loops in a certain area, and when pressure is applied from above the loops, it tends to be resistant to the pressure and not easily crushed. Also, when the well density is 68 or less per 2.54 cm and the course density is 68 or less per 2.54 cm, the thickness of the fabric does not increase, the fabric does not easily become hard, and it is suitable for the flow path material for permeated water.

[0026] Moreover, the product of the well density and the course density of the tricot fabric is preferably 2700 or more, more preferably 3000 or more. When the product of the well density and the course density of the tricot fabric is less than 2700, the convex portions of the needle loops in a certain area of the tricot fabric are reduced, and when pressure is applied from above the loops, it tends to be unable to withstand the pressure and is easily crushed. Also, the product of the well density and the course density of the tricot fabric is preferably 4600 or less. When the product of the well density and the course density of the tricot fabric exceeds 4600, the thickness of the fabric becomes large, the fabric becomes hard, and it tends not to be suitable for the flow path material for permeated water.

[0027] Examples of the knitting structure of the tricot fabric include single tricot knitting such as double denim structure, back half structure, and half tricot structure. Among them, double denim structure and half tricot structure are preferable. In double tricot knitting, the thickness of the fabric becomes large, the fabric becomes hard, and it tends not to be suitable for the flow path material for permeated water.

[0028] Moreover, the total fineness of the front yarn and the back yarn of the thermoplastic core-sheath composite fiber constituting the tricot fabric is preferably 80 to 140 dtex. If the total fineness of the front yarn and the back yarn of the thermoplastic core-sheath composite fiber constituting the tricot fabric is less than 80 dtex, the strength of the convex part of the needle loop becomes weak, and when pressure is applied from above the loop, it tends to be easily crushed without being able to withstand the pressure. Also, if the total fineness of the front yarn and the back yarn of the thermoplastic core-sheath composite fiber constituting the tricot fabric exceeds 140 dtex, the thickness of the fabric becomes large, the fabric becomes hard, and it tends to be unsuitable as a flow path material for permeating water.

[0029] The difference in the runner length between the front yarn and the back yarn of the tricot fabric is preferably 40 cm or less. If the difference in the runner length between the front yarn and the back yarn of the tricot fabric exceeds 40 cm, the balance between the ground tissue part which is the sinker loop part and the convex part which is the needle loop part deteriorates, and when the tricot fabric is heat set, it may tear or may not be able to be adjusted to the target properties.

[0030] Also, the thickness of the tricot fabric is preferably 0.18 to 0.26 mm. If the thickness of the tricot fabric is less than 0.18 mm, there are few voids formed by the ground tissue part which is the sinker loop part and the convex part which is the needle loop part of the tricot flow path material, and a sufficient flow rate cannot be ensured. If the thickness of the tricot fabric exceeds 0.26 mm, the thickness of the fabric becomes large, the fabric becomes hard, and it tends to be unsuitable as a flow path material for permeating water.

[0031] In the thermoplastic core-sheath composite fiber constituting the tricot fabric, the difference in the total fineness between the front yarn and the back yarn is preferably 20 dtex or less. If the difference in the total fineness between the front yarn and the back yarn is greater than 20 dtex, the strength of the convex part of the needle loop and the strength of the ground tissue of the sinker loop part become weak, and when pressure is applied from above the loop, it tends to be easily crushed without being able to withstand the pressure. Also, unevenness tends to occur in the thickness of the fabric, and it tends to be unsuitable as a flow path material for permeating water. Note that the total fineness of the front yarn and the total fineness of the back yarn may be either larger.

[0032] When the tricot fabric is hot-pressed at 90°C and 7.0 MPa for 3 minutes, it is necessary that the change ratio of the thickness of the tricot fabric before and after pressure application is 14% or less. When the change ratio of the thickness of the tricot fabric before and after pressure application when the tricot fabric is hot-pressed at 90°C and 7.0 MPa for 3 minutes exceeds 14%, it indicates that the strength of the convex part of the needle loop is weak and it is easily crushed without being able to withstand the pressure when pressure is applied from above the loop. Furthermore, it is more preferable that the change ratio of the thickness of the tricot fabric before and after pressure application when hot-pressed at 90°C and 7.0 MPa for 3 minutes is 7% or less. Also, regarding the resin constituting the flow path material for permeated water, by applying pressure to the resin in a state where the temperature is above the glass transition temperature, the strain received by the pressure can be fixed. Utilizing this, by measuring the thickness of the flow path material after pressurization and the flow path material before pressurization, the ease of crushing can be easily measured. In the present invention, a polyester-based resin is used. Since the glass transition point of the polyester-based resin is about 80°C, it is hot-pressed at 90°C.

[0033] The tricot fabric in the present invention uses two combs. One comb constitutes the part of the ground tissue which is the sinker loop part, and the other comb constitutes the convex part which is the needle loop part. However, the ratio (groove width / ridge width) of the width of the part between the convex parts (groove width) and the width of the convex part (ridge width) is preferably 0.4 to 0.8. At that time, the groove width is preferably 100 to 200 μm, and more preferably 110 to 190 μm is more preferable. The ridge width is preferably 150 to 350 μm, and more preferably 240 to 300 μm. If the ratio (groove width / ridge width) of the width of the portion between the convex portions of the needle loop (groove width) to the width of the convex portion (ridge width) is less than 0.4, there are few voids formed by the ground tissue portion of the sinker loop portion of the tricot flow path material and the convex portion of the needle loop portion, and it is impossible to secure a sufficient flow rate. If the ratio (groove width / ridge width) of the width of the portion between the convex portions of the needle loop (groove width) to the width of the convex portion (ridge width) exceeds 0.8, the strength of the convex portion of the needle loop becomes weak, and when pressure is applied from above the loop, it cannot withstand the pressure and is likely to collapse. Also, when pressure is applied, the separation membrane is likely to fall into the groove, and the flow rate tends to decrease. Also, the height of the groove is preferably 80 to 120 μm. If the height of the groove is 80 μm or more, a sufficient flow rate can be secured, and if it is 120 μm or less, it is difficult to collapse when a high pressure is applied. The height, width (groove width) of the portion between the convex portions (grooves) of the needle loop and the width of the convex portion (ridge width) can be adjusted according to the knitting density, the total fineness of the thermoplastic core-sheath composite fiber used, and the heat setting conditions, and may be set to the desired width and its ratio.

[0034] The tricot fabric according to the present invention is manufactured, for example, by the following method. The thermoplastic core-sheath composite fiber is used for the front yarn and the back yarn of a two-bar tricot knitting machine to knit a tricot knitted fabric. The obtained tricot knitted fabric is heat-set to adhere the thermoplastic core-sheath composite fibers to each other and rigidify them, thereby obtaining a tricot fabric. The gauge number of the tricot knitted fabric is preferably 28 or more. Also, the heat setting may be performed by a pin tenter heat treatment machine, a cylinder dryer, or the like.

[0035] The above tricot fabric can be suitably used as a flow path material on the water permeable side of a liquid separation device. The flow path material for the liquid separation device of the present invention has a sufficient flow rate despite its thin thickness, and especially even at a high pressure of 7.0 MPa or more and even when pressurized for a long time Crush without any reduction in the flow rate.

Example

[0036] Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not necessarily limited thereto. The measurement methods of various properties used in this example and the evaluation criteria for the tricot fabric are as follows.

[0037] (1) Rate of change in thickness (%) of the tricot fabric before and after heat pressing Using a tabletop hot press (manufactured by Technosupply Co., Ltd., small press G-12 type), when the tricot fabric was heat pressed at 90 °C, 7.0 MPa for 3 minutes, the thickness of the tricot fabric before and after pressurization was measured, and the rate of change in thickness was calculated from the following formula. Rate of change in thickness (%) = {(thickness before pressurization - thickness after pressurization) / thickness before pressurization} × 100

[0038] (2) Groove width (μm) and rib width (μm) of the tricot fabric Using an optical microscope, a plan view photograph and a cross-sectional photograph of the tricot fabric were taken to measure the groove width and the rib width.

[0039] (3) Thickness (mm) of the tricot fabric The thickness of the tricot fabric was measured using a Peacock dial gauge (manufactured by Ozaki Seisakusho Co., Ltd., H-30 type, 0.01 graduation, measuring head 30 mm φ).

[0040] (4) Density (per 2.54 cm) In accordance with JIS L 1096 8.6.2 Density of knitted fabrics, the number of wales and the number of courses in a 2.54 cm section of the tricot fabric were measured.

[0041] (5) Flow rate reduction rate The H-value described in U.S. Patent Application Publication No. 2005 / 0173333 was measured by a known method. Different from U.S. Patent Application Publication No. 2005 / 0173333, the flow rate under a predetermined pressure was measured as the H-value (ml / min). The flow rate reduction rate was calculated from the H-value (ml / min) when pressurized to 5.5 MPa and the H-value (ml / min) when pressurized to 5.5 MPa again after pressurization to 7.0 MPa. The flow rate reduction rate was evaluated as ⊙ when it was 5% or less, ○ when it was greater than 5% and 12% or less, and × when it was greater than 12%.

[0042] [Example 1] A thermoplastic core-sheath composite fiber (44 dtex / 24 f) was obtained with polyethylene terephthalate (melting point: 260 °C) as the core and a low-melting-point copolymerized polyester (melting point: 190 °C) obtained by copolymerizing 25 mol% of isophthalic acid as the acid component of polyethylene terephthalate as the sheath, and the core / sheath ratio at that time was 72 / 28 on a volume basis. Using the said composite fiber as the front yarn and the same thermoplastic composite fiber for the back yarn, on a 36-gauge double-bar tricot knitting machine, the runner length of the front yarn was 112.0 cm and the runner length of the back yarn was 112.0 cm, and it was knitted into a double denim structure (closed eyes).

[0043] The obtained tricot knitted fabric was heat-set for 1 minute with a pin tenter set at 200 °C to obtain a flow path material of a tricot fabric with a well density of 60 pieces / 2.54 cm and a course density of 60 pieces / 2.54 cm. Also, the rate of change (%) of the thickness of the obtained tricot fabric before and after heat pressing was 6.4%.

[0044] [Example 2] A flow path material was obtained in the same manner as in Example 1, except that the well density of the processed fabric after heat-setting for 1 minute with a pin tenter was 65 pieces / 2.54 cm.

[0045] The rate of change (%) of the thickness of the obtained tricot fabric before and after heat pressing was 10.0%.

[0046] [Example 3] Using the thermoplastic core-sheath composite fiber (56 dtex / 12 f) of the same resin combination as in Example 1 as the front yarn, a 36-gauge two-bar tricot knitting machine was used. Except that the runner length of the front yarn was 127.5 cm, the runner length of the back yarn was 94.0 cm, and it was knitted into a half stitch, in the same manner as in Example 1, a flow path material was obtained.

[0047] The rate of change (%) in thickness before and after heat pressing of the obtained tricot fabric was 13.5%.

[0048] [Example 4] Using the thermoplastic core-sheath composite fiber (56 dtex / 48 f) of the same resin combination as in Example 1 as the front yarn, a 36-gauge two-bar tricot knitting machine was used. Except that the runner length of the front yarn was 127.5 cm, the runner length of the back yarn was 94.0 cm, and it was knitted into a half stitch, in the same manner as in Example 1, a flow path material was obtained.

[0049] The rate of change (%) in thickness before and after heat pressing of the obtained tricot fabric was 8.0%. [Comparative Example 1]

[0050] Using the thermoplastic core-sheath composite fiber (56 dtex / 24 f) of the same resin combination as in Example 1 as the front yarn, a 36-gauge two-bar tricot knitting machine was used. Except that the runner length of the front yarn was 127.5 cm, the runner length of the back yarn was 94.0 cm, it was knitted into a half stitch, and after heat setting for 1 minute with a pin tenter, the well density of the processed fabric was set to 70 per 2.54 cm, in the same manner as in Example 1, a flow path material was obtained.

[0051] The rate of change (%) in thickness before and after the treatment when the obtained tricot fabric was heat pressed was 13.1%.

[0052] [Comparative Example 2] Using the thermoplastic core-sheath composite fiber (56 dtex / 24 f) with the same resin combination as in Example 1 as the front yarn, a 36-gauge two-bar tricot knitting machine was used. Except that the runner length of the front yarn was 94 cm and the runner length of the back yarn was 127.5 cm and it was knitted into a queen's coat structure, it was the same as in Example 1, and a flow path material was obtained.

[0053] The rate of change in thickness (%) before and after the treatment when the obtained tricot fabric was heat-pressed was 15%.

[0054]

Table 1

[0055] <Results> [Examples 1 to 4] The rate of change in thickness (%) before and after the treatment when the tricot fabric was heat-pressed was 14% or less, and the flow rate reduction rate at that time was also 12% or less. When evaluated as a flow path material, it was at a level where it could be stably used for a long time even under high-pressure conditions.

[0056] [Comparative Examples 1 to 2] In Comparative Example 1, the rate of change in thickness (%) before and after the treatment when the tricot fabric was heat-pressed was 14% or less, but the thickness of the flow path material was greater than 0.26 mm. In Comparative Example 2, the rate of change in thickness (%) exceeded 14%. Also, the flow rate reduction rate at that time exceeded 12%. When evaluated as a flow path material, the flow rate was low and it could not withstand actual use.

Claims

1. A channel material for a liquid separation device made of a tricot fabric containing thermoplastic core-sheath composite fibers composed of two types of polyester resins having different melting points or softening points. In the thermoplastic core-sheath composite fibers, the high melting point component is arranged in the core part and the low melting point component is arranged in the sheath part. The high melting point component is polyethylene terephthalate, the melting point difference between the two components is 60 °C or more, the tricot fabric is a tricot knitted fabric composed only of a front yarn and a back yarn, the front yarn and the back yarn are the thermoplastic core-sheath composite fibers, and the thermoplastic core-sheath composite fibers are adhered to each other and rigidified. Its wale density is 50 to 68 per 2.54 cm, and its course density is 50 to 68 per 2.54 cm. The rate of change in the thickness of the tricot fabric before and after heat pressing the tricot fabric at 90 °C and 7.0 MPa for 3 minutes is 14% or less. A channel material for a liquid separation device.

2. The total fineness of the thermoplastic core-sheath composite fiber of the front yarn and the thermoplastic core-sheath composite fiber of the back yarn constituting the tricot fabric is 80 to 140 dtex, the difference in the runner length between the front yarn and the back yarn is 40 cm or less, and the thickness of the tricot fabric is 0.18 to 0.26 mm. The channel material for a liquid separation device according to Claim 1.

3. The difference in the total fineness between the thermoplastic core-sheath composite fiber of the front yarn and the thermoplastic core-sheath composite fiber of the back yarn constituting the tricot fabric is 20 dtex or less. The channel material for a liquid separation device according to Claim 1 or 2.

4. The core / sheath ratio of the thermoplastic core-sheath composite fibers of the front yarn and the back yarn constituting the tricot fabric is 60 / 40 to 80 / 20 on a volume basis. The channel material for a liquid separation device according to any one of Claims 1 to 3.

5. The tricot fabric is formed by using one of the two sinkers to form a part of the ground tissue that is a sinker loop part, and the other sinker to form a convex part that is a needle loop part. The ratio (groove width / ridge width) of the width of the part between the convex parts (groove width) to the width of the convex part (ridge width) is 0.4 to 0.

8. The channel material for a liquid separation device according to any one of Claims 1 to 4.

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