JP2009131840A - Separation membrane support, and separation membrane and fluid separation element using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly durable separation membrane support which suppresses decrease of the amount of produced water due to inhibition of water flow caused by falling of a separation membrane into the hollow part of a feed water passage material when reverse osmosis is high. <P>SOLUTION: The separation membrane support is made of a long fiber nonwoven fabric comprising thermoplastic continuous filaments, and is made to have a tensile strength in the transverse direction of 50-900 N/5 cm and a longitudinal to transverse ratio of tensile strength of 1.0-2.7, thereby obtaining a highly durable separation membrane support having high strength capable of suppressing decrease of the amount of produced water due to inhibition of water flow caused by curving of a separation membrane into the hollow part of a feed water passage material, or the breaking of the membrane when reverse osmosis is high. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a support that supports a separation membrane such as a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, and a reverse osmosis membrane, which is made of a long-fiber nonwoven fabric composed of thermoplastic continuous filaments. The present invention also relates to a separation membrane and a fluid separation element using the same.

  Membrane technology is often applied to water treatment in recent years. For example, microfiltration membranes or ultrafiltration membranes are used for water purification plants, reverse osmosis membranes for seawater desalination, reverse osmosis membranes and nanofiltration for the production of semiconductor manufacturing water, boiler water, medical water, laboratory pure water, etc. Membranes are used, and a membrane separation activated sludge method using microfiltration membranes or ultrafiltration membranes is also applied to sewage wastewater treatment.

  These separation membranes are roughly classified into flat membranes and hollow fiber membranes according to their shapes, but flat membranes formed mainly from synthetic polymers are generally non-woven fabrics because the membrane itself having a separation function is inferior in mechanical strength. In many cases, it is used integrally with a support such as woven fabric or cloth.

  In general, a membrane having a separating function and a support are a method of casting and fixing a polymer solution that is a raw material of a membrane having a separating function on a nonwoven fabric or a woven fabric, or a semipermeable membrane such as a reverse osmosis membrane. Are integrated by, for example, a method in which a polymer solution is cast on a nonwoven fabric or a woven fabric to form a support layer, and then a semipermeable membrane is formed on the support layer. Therefore, the nonwoven fabric or woven fabric used as the support may be broken through by permeation when the polymer solution is cast, the membrane substance may be peeled off, or the membrane may be fluffed or curved due to the support. An excellent film forming property that does not cause defects such as non-uniformity and pinholes is required.

  In addition, particularly in the case of a semipermeable membrane such as a reverse osmosis membrane that is often used under high pressure, the support is required to have high mechanical strength and dimensional stability.

As such a separation membrane support and a method for producing the same, a surface layer using a thick fiber and a surface layer having a large surface roughness, and a back surface layer using a thin fiber and a small opening and a dense structure are used. Separation membrane support characterized by comprising a multilayer structure non-woven fabric based on a heavy structure (see Patent Document 1), a non-woven fabric for casting a polymer solution for forming a semipermeable membrane to form a membrane in semipermeable membrane support made from the nonwoven, low density layer of air permeability 5~50cc ^/ cm 2 ^/ sec and, 5 cc ^/ cm less than 2 / sec at air permeability 0.1 cc ^/ cm 2 / sec or more a nonwoven two-layer structure of integrating the dense layer of semipermeable, wherein the air permeability of the whole is 0.1cc ^/ cm ² /sec~4.5cc/cm 2 ^/ sec Membrane supports are known (see Patent Document 2) See). However, since these supports are made of short fibers, there is a risk that the film may become non-uniform or have defects due to fluffing, and further, there is no description about the strength of the nonwoven fabric, or there is no detailed description. There was a problem that the mechanical strength and dimensional stability could not be obtained.

Further, as such a separation membrane support and a method for producing the same, the average value of the longitudinal length (MD) and the transverse direction (CD) at 5% elongation is 4.0 km or more and the air permeability is 0. There is known a semipermeable membrane support characterized by comprising a nonwoven fabric of ^{2 to} 10.0 cc / cm ² · sec (see Patent Document 3). However, the support is a non-woven fabric produced by a papermaking method, and in order to obtain the characteristic mechanical strength, it is stretched in a hot water bath after melt spinning and subsequently subjected to tension heat treatment and / or relaxation heat treatment. For example, the birefringence of the polyester fiber constituting the nonwoven fabric is greatly increased, and the heat shrinkage stress is set to a specific range, which increases the manufacturing cost. There was a problem that there was a risk that a defect would occur.

  Furthermore, it is known that when the strength aspect ratio in the paper flow direction and the width direction is high, the curvature in the width direction becomes large when the separation membrane liquid is applied to the support, which causes non-uniform separation membrane production. Yes. Although this curvature can be reduced by increasing the basis weight of the nonwoven fabric to be used, the increase in the basis weight is not preferable because it increases the cost and increases the thickness of the nonwoven fabric itself, leading to a reduction in the membrane area within a certain volume.

  In addition, when the aspect ratio is high, the load resistance in the horizontal direction is weaker than the vertical direction when actually applied with a high reverse osmotic pressure, so it bends into the depression of the feed water flow path material and inhibits the flow of the feed water In addition to reducing the amount of water produced, the membrane may be destroyed in some cases.

Adjusting the strong aspect ratio In the papermaking method, a method to adjust the strong aspect ratio has been proposed to reduce the curvature in the width direction, but the concentration and flow rate of the raw material dispersion, the wire speed of the inclined wire mesh, and the inclination angle. In addition, since only the strength ratio is specified and there is no description of the strength, there is a problem that sufficient mechanical strength and dimensional stability as a support cannot be obtained. (See Patent Document 4)
Japanese Examined Patent Publication No. 4-21526 Japanese Patent Publication No. 5-35009 Japanese Patent No. 3153487 JP 2002-95937 A

  The present invention comprises a long-fiber nonwoven fabric composed of thermoplastic continuous filaments, and has excellent film-forming properties when supporting separation membranes such as microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, and reverse osmosis membranes. And providing a highly durable separation membrane support having high strength that suppresses a decrease in the amount of water produced when the separation membrane is bent into the supply water channel material depression when high reverse osmosis pressure is applied, or the membrane breakage. The purpose is to do.

  In order to solve this problem, the present inventors have repeatedly studied and found that a long fiber nonwoven fabric produced with a thermoplastic continuous filament made of a polyester polymer is suitable for a separation membrane support. In addition, the long-fiber nonwoven fabric has a tensile strength in the transverse direction that exceeds a certain level, and has excellent film-forming properties by having a tensile strength aspect ratio in a specific range. It has been found that a separation membrane support that maintains a high amount of fresh water is obtained.

  That is, the present invention has a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, a reverse filtration strength characterized by a transverse tensile strength of 50 to 900 N / 5 cm and a tensile strength aspect ratio of 1.0 to 2.7. A support for supporting a separation membrane such as an osmosis membrane, a separation membrane using the support, and a fluid separation element.

  According to the present invention, it consists of a long-fiber nonwoven fabric composed of thermoplastic continuous filaments, and since the difference in longitudinal and transverse strength is small, even when high reverse osmotic pressure is applied, there is little drop into the feed water channel material recess and stable supply By passing water, it is possible to obtain a support that can secure a large amount of fresh water and that can form a membrane uniformly while suppressing the bending in the lateral direction when forming a separation membrane.

  The separation membrane support of the present invention is a support for forming a membrane having a separation function (separation membrane) on the surface thereof.

  It is important that the separation membrane support of the present invention is composed of a long-fiber nonwoven fabric composed of thermoplastic continuous filaments. By comprising a long-fiber nonwoven fabric composed of thermoplastic continuous filaments, it is possible to suppress non-uniformity and membrane defects during casting of a polymer solution caused by fuzz, which occurs when a short-fiber nonwoven fabric is used. Also, because it is composed of thermoplastic continuous filaments, it has high mechanical strength compared to short fiber nonwoven fabrics, especially papermaking nonwoven fabrics with short fiber lengths, and as a separation membrane support, particularly as a semipermeable membrane support that can be subjected to high pressure during use. Excellent durability can be expressed, and a decrease in the amount of water produced due to a drop in the feed water channel material depression or a membrane breakage due to this can be suppressed.

  In order to produce a separation membrane support having such characteristics, the tensile strength in the nonwoven fabric transverse direction (CD) of the long-fiber nonwoven fabric used as the support is 50 to 900 N / 5 cm, and the tensile strength aspect ratio is 1. It is important that it is between 0.0 and 2.7. Moreover, it is preferable that the tensile strength to the nonwoven fabric horizontal direction (CD) of a long-fiber nonwoven fabric is 70-900N / 5cm, and a tensile strength aspect ratio is 1.0-2.5, and the nonwoven fabric side of a long-fiber nonwoven fabric is preferable. More preferably, the tensile strength in the direction (CD) is 90 to 900 N / 5 cm, and the tensile strength aspect ratio is 1.0 to 2.3. The tensile strength aspect ratio in the present invention refers to tensile strength in the nonwoven fabric longitudinal direction (MD) / tensile strength in the nonwoven fabric transverse direction (CD).

  The long fiber nonwoven fabric constituting the separation membrane support of the present invention is composed of a continuous thermoplastic filament such as a spunbond nonwoven fabric produced by a spunbond method or a meltblown nonwoven fabric produced by a meltblown method. In addition, although the manufacturing method of a nonwoven fabric will not be specifically limited if comprised by the thermoplastic continuous filament, since it is excellent by mechanical strength and dimensional stability, it is preferable that it is a spun bond nonwoven fabric.

  The long fiber nonwoven fabric constituting the separation membrane support of the present invention is preferably a laminated nonwoven fabric obtained by laminating and integrating. By laminating and using long fiber nonwoven fabrics, a separation membrane support having excellent uniformity can be obtained. Furthermore, by forming the laminated interface, the back penetration is further reduced by suppressing the excessive permeation during casting of the polymer solution, and it can be suitably used as a separation membrane support. The number of laminated long fiber nonwoven fabrics is preferably 2 to 5 layers. If there are two or more layers, the basis weight uniformity is improved as compared with the case of a single layer, and sufficient uniformity is obtained. If it is below a layer, it can wrinkle at the time of lamination | stacking and can suppress peeling between layers.

  Examples of the combination of the laminated long fiber nonwoven fabric include a laminated nonwoven fabric having a three-layer structure in which a single layer of melt blown nonwoven fabric is disposed between two layers of spunbond nonwoven fabric. In order to set the tensile strength to CD) to 50 to 900 N / 5 cm, at least one layer is preferably a spunbonded nonwoven fabric. Moreover, it is a more preferable form that it consists essentially of a spunbonded nonwoven fabric, such as a laminate composed of two layers of spunbonded nonwoven fabric.

  The surface of the laminated long-fiber nonwoven fabric is preferably smooth from the viewpoint of film-forming properties at least on the side on which the film is formed. The smooth surface as used in the field of this invention means the surface without the intentional unevenness | corrugation by an engraving roll etc., for example, means the surface processed by the flat roll etc.

  In the present invention, the thermoplastic continuous filament constituting the long fiber nonwoven fabric may be a thermoplastic continuous filament composed of a single component or a composite thermoplastic continuous filament composed of a plurality of components, but in the separation membrane support of the present invention, Is a long fiber nonwoven fabric composed of composite thermoplastic continuous filaments, in which a low melting point polymer having a melting point lower by 10 to 140 ° C. than the melting point of the high melting point polymer is disposed around the high melting point polymer. It is preferable. A low-melting polymer having a melting point lower by 10 to 140 ° C. than the melting point of the high-melting polymer is disposed around the high-melting polymer to form a long fiber nonwoven fabric by thermocompression bonding and used as a separation membrane support. In this case, since the filaments constituting the nonwoven fabric are firmly bonded to each other, nonuniformity at the time of casting the polymer solution due to fluffing and film defects can be suppressed. Further, by using such a composite thermoplastic continuous filament, the filaments constituting the nonwoven fabric are firmly bonded to each other, and the number of bonding points is increased as compared with the mixed fiber type. In particular, it leads to dimensional stability and durability when used as a semipermeable membrane support to which a high pressure is applied during use. If the melting point difference between the high melting point polymer and the low melting point polymer is 10 ° C. or higher, the desired thermal adhesiveness can be obtained, and if it is 140 ° C. or lower, the low melting point polymer component is applied to the thermocompression bonding roll during thermocompression bonding. Can be prevented from being fused and the productivity is lowered. A more preferable range of the melting point difference between the high melting point polymer and the low melting point polymer is 20 to 120 ° C, and a further preferable range is 30 to 100 ° C.

  Further, in the separation membrane support of the present invention, a composite thermoplastic continuous filament in which a low melting point polymer having a melting point lower by 10 to 140 ° C. than the melting point of the high melting point polymer is disposed around the high melting point polymer. When the separation membrane is formed on the separation membrane support of the present invention, the melting point of the high-melting polymer in the case of the long-fiber nonwoven fabric composed of the separation membrane is excellent in film forming properties and excellent in durability. Although it will not be limited if it can be obtained, it is preferable that it is the range of 160-320 degreeC. When the melting point of the high-melting polymer is 160 ° C. or higher, when a long-fiber nonwoven fabric is formed and used as a separation membrane support, even if it passes through a process of applying heat during the production of the separation membrane or fluid separation element, the shape stability is improved. If it is excellent and it is 320 degrees C or less, it can suppress that the heat energy for melting at the time of long-fiber nonwoven fabric manufacture is consumed greatly, and productivity falls. A more preferable range of the melting point of the high melting point polymer is 170 to 300 ° C, and a more preferable range is 180 to 280 ° C.

  The proportion of the low melting point polymer in the composite thermoplastic continuous filament is not limited as long as a long-fiber nonwoven fabric suitable for the separation membrane support can be obtained, but it is preferably 10 to 70 wt%. More preferably, it is 15-60 wt%, and it is further more preferable that it is 20-50 wt%. If the proportion of the low melting point polymer is 10 wt% or more, the desired thermal adhesiveness can be obtained, and if it is 70 wt% or less, the low melting point polymer component is fused to the thermocompression-bonding roll at the time of thermocompression bonding. It can suppress that property falls.

  The composite form of the composite thermoplastic continuous filament is not limited as long as a long fiber nonwoven fabric suitable for the separation membrane support can be obtained. For example, a concentric core-sheath type, an eccentric core-sheath type, a sea-island type, etc. In addition, examples of the filament cross-sectional shape include a circular cross-section, a flat cross-section, a polygonal cross-section, a multi-leaf cross-section, and a hollow cross-section. Above all, filaments can be firmly bonded to each other by thermocompression bonding. Furthermore, the thickness of the resulting separation membrane support can be reduced, and the separation membrane area per unit when used as a fluid separation element can be increased. Therefore, it is preferable to use a concentric core-sheath type for the composite form and a circular cross section or a flat cross section as the filament shape.

  In the present invention, the raw material of the thermoplastic continuous filament constituting the long fiber nonwoven fabric is not particularly limited as long as a long fiber nonwoven fabric suitable for the separation membrane support can be obtained. For example, a polyester polymer, a polyamide polymer, a polyolefin polymer, or a mixture or copolymer thereof is not limited at all, but more mechanical strength, heat resistance, water resistance, chemical resistance, etc. From the viewpoint of obtaining a separation membrane support having excellent durability such as the above, a polyester polymer is preferable. The polyester polymer used in the present invention is a polyester composed of an acid component and an alcohol component, and the acidic component includes aromatic carboxylic acids such as terephthalic acid, isophthalic acid and phthalic acid, adipic acid, sebacic acid and the like. Aliphatic dicarboxylic acids such as aliphatic dicarboxylic acid and cyclohexanecarboxylic acid can be used, and ethylene glycol, diethylene glycol, polyethylene glycol and the like can be used as the alcohol component. Examples of the polyester polymer include polyethylene terephthalate resin, polybutylene terephthalate resin, polytrimethylene terephthalate resin, polyethylene naphthalate resin, polylactic acid resin, polybutylene succinate resin, and the like. Examples include coalescence. Further, a high melting point and a low melting point weight in the case of a composite thermoplastic continuous filament in which a low melting point polymer having a melting point lower by 10 to 140 ° C. than the melting point of the high melting point polymer is arranged around the high melting point polymer. The combination (high-melting point polymer / low-melting point polymer) is not limited as long as a long-fiber nonwoven fabric suitable for the separation membrane support can be obtained, but polyethylene terephthalate resin / polybutylene terephthalate resin, Examples include a combination of polyethylene terephthalate resin / polytrimethylene terephthalate resin, polyethylene terephthalate resin / polylactic acid resin, polyethylene terephthalate resin / copolymerized polyethylene terephthalate resin, and the copolymer component of the copolymerized polyethylene terephthalate resin includes isophthalic acid and the like. Preferably It is.

  Furthermore, when the separation membrane support is discarded after being used, the biodegradable resin is also preferably used as a raw material for the thermoplastic continuous filament constituting the long-fiber nonwoven fabric because it is easy to discard and the environmental load is small. Examples of the biodegradable resin used in the present invention include polylactic acid resin, polybutylene succinate resin, polycaprolactone resin, polyethylene succinate resin, polyglycolic acid resin, polyhydroxybutyrate resin, etc. However, it is a plant-derived resin that does not deplete petroleum resources, has relatively high mechanical properties and heat resistance, and has recently been highlighted as a biodegradable resin with low production costs. The polylactic acid resin used is preferably used as a raw material for fibers constituting the nonwoven fabric. The polylactic acid resin used in the present invention is preferably poly (D-lactic acid), poly (L-lactic acid), a copolymer of D-lactic acid and L-lactic acid, or a blend thereof.

  The long fiber nonwoven fabric constituting the separation membrane support of the present invention has a crystal nucleating agent, a matting agent, a lubricant, a pigment, an antifungal agent, an antibacterial agent, a flame retardant, as long as the effects of the present invention are not impaired. A hydrophilic agent or the like may be added. Especially when thermocompression molding of long fiber nonwoven fabrics, metal oxides such as titanium oxide have the effect of improving the adhesion of long fiber nonwoven fabrics by increasing the thermal conductivity, and the mold release property between the thermocompression roll and web. It is preferable to add an aliphatic bisamide such as ethylenebisstearic acid amide and / or an alkyl-substituted aliphatic monoamide, which has an effect of improving the adhesion stability by increasing the number. These various additives may be present in the thermoplastic continuous filament or may be present on the surface thereof.

In the long-fiber non-woven fabric constituting the separation membrane support of the present invention, the average fiber diameter of the thermoplastic continuous filament is 3 to 17 μm (average fineness 0.1 to 3.3 in terms of density of polyethylene terephthalate fiber 1.38 g / cm ²⁾ . 0 dtex), preferably 5 to 15 μm (0.3 to 2.5 dtex), and more preferably 7 to 14 μm (0.5 to 2.0 dtex). If the average fiber diameter of the thermoplastic continuous filament constituting the long-fiber nonwoven fabric is 3 μm or more (average fineness is 0.1 dtex or more), the spinnability is less likely to deteriorate during the production of the long-fiber nonwoven fabric. Since air permeability can be maintained, good film-forming properties can be obtained with little film peeling or the like during casting of the polymer solution. On the other hand, when the average fiber diameter of the thermoplastic continuous filament constituting the long fiber nonwoven fabric is 17 μm or less (average fineness is 3.0 dtex or less), a long fiber nonwoven fabric and a separation membrane support excellent in uniformity can be obtained. In addition, since the density of the separation membrane support can be increased, it is possible to obtain a good membrane forming property with less permeation and the like during casting of the polymer solution. Moreover, the average fiber diameter or average fineness of a thermoplastic continuous filament may differ between each long-fiber nonwoven fabric in lamination | stacking. For example, the average fiber diameter of the long-fiber nonwoven fabric may be 10 μm (the average fineness is 1.0 dtex), and the average fiber diameter of the other long-fiber nonwoven fabric may be 17 μm (the average fineness is 3.0 dtex). Here, the average fiber diameter of the thermoplastic filament constituting the long-fiber nonwoven fabric refers to that measured by the method described in Example (3) below.

Basis weight of the long-fiber nonwoven fabric composing the support for a separation membrane present invention is preferably 20 to 150 g / ^{m 2,} more preferably from 30 to 120 g / ^{m 2,} is 40~90g / ^{m 2} More preferably. If the basis weight of the long-fiber nonwoven fabric constituting the separation membrane support is 20 g / m ² or more, good membrane-forming property can be obtained with less permeation and the like during casting of a polymer solution, mechanical strength, A separation membrane having excellent durability can be obtained. On the other hand, if the basis weight of the separation membrane support is 150 g / m ² or less, the thickness of the separation membrane can be reduced and the separation membrane area per fluid separation element unit can be increased. The basis weight of each long-fiber nonwoven fabric to be laminated is not limited as long as the basis weight of the final separation membrane support is in the range of ²⁰ to 150 g / m ^2. For example, the basis weight is 10 g / m ² . Lamination, 30 g / m ² two-layer lamination, etc. are appropriately determined according to the product design. Here, the basis weight of the separation membrane support refers to that measured by the method described in Example (5) below.

  The thickness of the separation membrane support of the present invention is preferably 30 to 200 μm. By making the thickness of the separation membrane support 30 μm or more, more preferably 40 μm or more, and even more preferably 50 μm or more, it is possible to obtain good film-forming properties with little over-permeation at the time of casting a polymer solution, A separation membrane having excellent mechanical strength and durability can be obtained. On the other hand, by setting the thickness of the separation membrane support to 200 μm or less, more preferably 160 μm or less, and even more preferably 120 μm or less, the thickness of the separation membrane is reduced and the separation membrane area per fluid separation element unit is increased. Can be made. Here, the thickness of the separation membrane support refers to that measured by the method described in Example (6) below.

  The production method of the long-fiber nonwoven fabric constituting the separation membrane support of the present invention is not limited as long as a separation membrane having good film forming properties and excellent durability can be obtained when the separation membrane is formed on the support. However, a spunbond method, a melt blow method, and a method of laminating these long fiber nonwoven fabrics are preferably used. As a method of lamination and integration, a temporarily bonded sheet is prepared by a spunbond method, and a temporarily bonded spunbond nonwoven fabric is bonded by post-processing, or a spunbond nonwoven fabric is bonded to each other with an adhesive substance. The former is a preferred method because it is easy to reduce workability and thickness.

  As a method for adjusting the longitudinal / lateral strength ratio of the long-fiber nonwoven fabric to 1.0 to 2.7, for example, when the spunbond method is used, the molten thermoplastic polymer is extruded from a rectangular nozzle, and this is a high-speed suction gas. After drawing and spinning by the method, the fibers are uniformly collected on a moving conveyor whose distance from the airflow rectifier is 300 to 1000 mm through an airflow rectifier having an uneven shape, and is made into a web. When integrating by applying thermocompression bonding, entanglement, etc., to the method of adjusting the uneven shape of the airflow rectifier and the fiber passage length of the airflow rectifier, or when collecting the fibers on a moving conveyor Examples include a method of adjusting the number of lateral fibers using an injection device having a certain amount of amplitude. The spinning speed is preferably 2000 m / min or more, more preferably 3000 m / min or more, and further preferably 4000 m / min or more in order to cause oriented fibers to be highly oriented and crystallized. When the thermoplastic continuous filament is formed into a composite form such as a core-sheath type, a normal composite method can be employed.

  In the case of the melt-blowing method, the thermoplastic polymer can be stretched by drawing a heated high-speed gas fluid onto the molten thermoplastic polymer to form ultrafine fibers, which can be collected.

  Furthermore, in order to obtain a separation membrane with good film-forming properties and excellent durability, a long-fiber nonwoven fabric obtained by the spunbond method is thermocompression bonded with a pair of upper and lower flat rolls in terms of suppressing fuzz. More preferably, they are integrated. The flat roll is a roll having no irregularities on the surface of the roll, and a metal roll or an elastic roll can be adopted. Examples of the elastic roll include so-called paper rolls such as paper, cotton, and aramid paper, and resin rolls such as urethane resin, silicon resin, and hard rubber. As a combination of a pair of flat rolls, a metal roll and a metal roll can be paired, or a metal roll and an elastic roll can be paired. In particular, by suppressing the fusion of fibers on the surface of the long-fiber nonwoven fabric and maintaining the form, it is possible to obtain an anchoring effect that suppresses separation of the separation membrane when used as a separation membrane support, so a pair of flat rolls It is also a preferable method to make a temperature difference between the rolls. In particular, a method of thermocompression bonding with a heated metal roll and a non-heated elastic roll can be preferably employed from the viewpoint of the anchoring effect.

  The temperature of the high temperature side or the heated flat roll is preferably 80 to 20 ° C lower than the melting point of the polymer constituting at least the surface of the thermoplastic continuous filament constituting the long fiber nonwoven fabric, and more preferably 70 to 30 ° C lower. Preferably, the temperature is 60 to 30 ° C lower. Further, the temperature of the other flat roll (on the low temperature side) of the pair of flat rolls is preferably 40 to 120 ° C. lower than the temperature of the flat roll on the high temperature side. By setting the temperature difference between the flat roll on the low temperature side and the flat roll on the high temperature side to 40 ° C. or more, more preferably 60 ° C. or more, it is possible to suppress the occurrence of extremely high density portions on the surface of the long-fiber nonwoven fabric. There is little film peeling due to insufficient permeation during casting of the molecular solution, and good film forming properties can be obtained. On the other hand, by making the temperature difference between the flat roll on the low temperature side and the flat roll on the high temperature side 120 ° C. or less, more preferably 100 ° C. or less, delamination of the laminated long fiber nonwoven fabric can be suppressed, Good film-forming properties can be obtained with little over-permeation during casting.

  Further, the temperature during processing of the upper and lower rolls is preferably in the range of ± 15 ° C. or less, more preferably in the range of ± 10 ° C. or less, centering on the temperature at the start of processing, and ± 5 ° C. or less. More preferably, it is the range. Although it is generally difficult to strictly control the temperature of the non-heated elastic roll, preliminary operation is performed in a state where it is in contact with a heated metal roll before processing, or the temperature of the elastic roll during processing. If it becomes too high, contact with air blow, shower ring, cooling roll, etc. If it becomes too low, heat with an infrared heater, heat medium circulation inside the roll, contact with heating roll, etc. Can be controlled.

  The linear pressure of the flat roll is preferably 20 to 500 kg / cm. Further, when the linear pressure of the flat roll is 20 kg / cm or more, more preferably 50 kg / cm or more, and even more preferably 100 kg / cm or more, delamination of the long-fiber nonwoven fabric can be suppressed, and when the polymer solution is cast Therefore, good film forming property can be obtained. On the other hand, by setting the linear pressure of the flat roll to 500 kg / cm or less, it is possible to suppress the formation of extremely high density portions on the surface of the long-fiber nonwoven fabric, and there is little film peeling due to insufficient penetration when the polymer solution is cast. Good film forming properties can be obtained.

  In addition, the thermocompression bonding was continuously or once wound up after a temporarily bonded long fiber nonwoven fabric was obtained by a pair of flat rolls or by a collecting conveyor used for collecting one flat roll and a web. A two-stage pressure bonding method is also preferable in which the heat pressure bonding is performed once again with a flat roll. By doing so, the characteristic of a long-fiber nonwoven fabric can be controlled more precisely.

  Also in the case of laminated long-fiber nonwoven fabric, a high-density surface layer is formed on the surface of each layer by thermocompression in the first stage, and a laminate is formed by thermocompression in the second stage, so that a high-density layer is formed at the lamination interface. Can be obtained, and a good film-forming property can be obtained with less permeation and the like during casting of the polymer solution.

  In the first-stage thermocompression bonding in the two-stage crimping method, since the nonwoven fabric can be densified at the time of the second-stage thermocompression bonding, the filling density of the temporarily bonded nonwoven fabric is 0.1 to 0.3. Preferably, the temperature of the heat roll at that time is 180 to 20 ° C. lower than the melting point of the fiber (or the low melting point portion) constituting the long fiber nonwoven fabric, and the linear pressure is preferably 5 to 100 kg / cm. .

  The difference in melting point between the temperature of the flat roll and the thermoplastic continuous filament (or its low melting point portion) in the first stage of thermocompression bonding is 180 ° C. or less, more preferably 160 ° C. or less, more preferably 140 ° C. or less, more preferably By setting it to 120 ° C. or lower, more preferably 100 ° C. or lower, a high-density layer can be formed on the front side and / or the back side of the long fiber nonwoven fabric. On the other hand, the difference between the temperature of the flat roll and the melting point of the thermoplastic continuous filament is 20 ° C. or higher, more preferably 40 ° C. or higher, further preferably 60 ° C. or higher, more preferably 80 ° C. or higher, and further preferably 100 ° C. or higher. In this way, it is possible to prevent the fusion on the front side and / or the back side of the long fiber nonwoven fabric from proceeding excessively and becoming difficult to integrate.

  Moreover, a high-density layer can be formed on the front side and / or the back side of the long-fiber nonwoven fabric by setting the linear pressure in the first-stage thermocompression bonding to 5 kg / cm or more, more preferably 10 kg / cm or more. . On the other hand, it is 100 kg / cm or less, more preferably 80 kg / cm or less, further preferably 70 kg / cm or less, and further preferably 60 kg / cm or less, so that the front side and / or the back side of the long fiber nonwoven fabric can be fused. It is possible to prevent excessive progress and integration.

  The temperature of the flat roll in the second stage (final stage) thermocompression bonding is preferably 80 to 20 ° C. lower than the melting point of the thermoplastic filament (or its low melting point portion) constituting the long fiber nonwoven fabric, and 70 to 30 ° C. It is more preferable that it is low, and it is more preferable that it is 60 to 30 ° C.

  The linear pressure of the flat roll in the second stage (final stage) thermocompression bonding is preferably 20 to 500 kg / cm. By making the linear pressure of the flat roll 20 kg / cm or more, more preferably 50 kg / cm or more, and even more preferably 100 kg / cm or more, delamination of the long-fiber nonwoven fabric can be suppressed, and at the time of casting the polymer solution Good film-forming properties can be obtained with little over-penetration and the like.

  In addition, as a method for producing a laminate having a three-layer structure in which a melt-blown nonwoven fabric is disposed between two layers of a temporarily bonded spunbond nonwoven fabric, the above-described method, between two layers of the temporarily bonded spunbond nonwoven fabric obtained, After stacking the melt-blown nonwoven fabrics produced on a separate line, the method may be thermocompression bonded under the same conditions as the two layers of the above temporarily bonded spunbond nonwoven fabrics, or placed on top of a series of collection conveyors. The spunbond nozzle, meltblown nozzle and spunbond nozzle that are extruded and fiberized webs are collected and laminated in order, and the method of thermocompression bonding under the above-mentioned lamination conditions is preferably used. it can. Further, the spunbond nozzle, melt blow nozzle, and spunbond nozzle arranged on the upper part of the collection conveyor are respectively collected and laminated in order, and the laminated web is collected. There is also a method of thermocompression bonding between a heat roll installed on a conveyor and the conveyor to produce a temporarily bonded sheet, which is continuously wound or once wound, and then thermocompression bonded under the above-mentioned conditions during lamination. It can be preferably used.

  The polymer solution cast on the separation membrane support is not limited as long as it has a separation function when it becomes a membrane, but polyarylethersulfone such as polysulfone and polyethersulfone, polyimide A solution of polyvinylidene fluoride, cellulose acetate or the like is preferably used, and in particular, a solution of polysulfone or polyarylethersulfone is more preferably used from the viewpoint of chemical, mechanical and thermal stability. The solvent can be appropriately selected according to the film-forming substance. Further, as a semipermeable membrane in the case where the separation membrane is a composite membrane including a support layer and a semipermeable membrane layer, a crosslinked polyamide membrane obtained by polycondensation of a polyfunctional acid halide and a polyfunctional amine is preferably used. it can.

  The fluid separation element of the present invention is a fluid separation element in which the above-described separation membrane is housed in a housing for easy handling, and the form thereof is not limited at all, but a flat membrane plate frame type In particular, a pleat type, a spiral type, and the like are preferable. In particular, a spiral type in which a separation membrane is spirally wound around a water collecting pipe together with a permeate flow path material and a supply liquid flow path material is preferably used. A plurality of fluid separation elements can be connected in series or in parallel to form a separation membrane unit.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited by these Examples. The characteristic values of the separation membrane support, the long-fiber nonwoven fabric constituting the separation membrane support, and the thermoplastic continuous filament constituting the long-fiber nonwoven fabric, and the characteristic values in the following examples are as follows: It is measured by the method.

(1) Melting point (° C)
Using a differential scanning calorimeter DSC-2 manufactured by Perkin Elma Co., Ltd., measurement was performed under the condition of a temperature rising rate of 20 ° C./min, and the temperature giving an extreme value in the obtained melting endotherm curve was defined as the melting point. Further, for a resin whose melting endotherm curve does not show an extreme value in a differential scanning calorimeter, the resin was heated on a hot plate, and the temperature at which the resin was completely melted by microscopic observation was taken as the melting point.

(2) Intrinsic viscosity IV
The intrinsic viscosity IV of the polyethylene terephthalate resin was measured by the following method.
8 g of a sample was dissolved in 100 ml of orthochlorophenol, and a relative viscosity η _r was determined by the following formula using an Ostwald viscometer at a temperature of 25 ° C.
η _r = η / η ₀ = (t × d) / (t ₀ × d ₀ )
Where η: viscosity of polymer solution η ₀ : viscosity of orthochlorophenol t: drop time of solution (seconds)
d: density of the solution (g / cm ³ )
t ₀ : Fall time of orthochlorophenol (seconds)
d ₀ : Orthochlorophenol density (g / cm ³ )
Then, from the relative viscosity η _r , the following formula:
IV = 0.0242η _r +0.2634
Was used to calculate the intrinsic viscosity IV.

(3) Average fiber diameter (μm)
Ten small sample samples are taken at random from the nonwoven fabric, photographed with a scanning electron microscope at a magnification of 500 to 3000 times, 10 from each sample, the diameter of a total of 100 fibers is measured, and the average value is calculated. Calculated by rounding off the second decimal place.

(4) Average fineness (dtex)
The average fineness was calculated from the average fiber diameter obtained above by the following formula.
Average fineness (dtex) = (d × D ² × π / 4) × 10 ⁻⁸
Where d: density (g / cm ³ )
D: Single fiber diameter by number average (nm)
The fiber density in this example is 1.38 g / cm ³ for polyethylene terephthalate resin and copolymerized polyester resin, 1.32 g / cm ³ for polybutylene terephthalate resin, and 1.27 g / cm for polylactic acid resin. Each m ³ was used.

(5) Weight per unit area (g / m ² )
Three non-woven fabrics of 30 cm × 50 cm were collected, the weight of each sample was measured, the average value of the obtained values was converted per unit area, and the first decimal place was rounded off.

(6) Thickness (μm)
Based on JIS L 1906: 2000 5.1, using a pressurizer with a diameter of 10 mm, measure 10 points at 10 μm intervals per 1 m in the width direction of the nonwoven fabric with a load of 10 kPa. Rounded off.

(7) Tensile strength (N / 5cm) and elongation at break (%)
Based on JIS L 1906: 2000 5.3.1, a sample of 5 cm × 30 cm was measured by measuring 5 points in the longitudinal direction and the transverse direction under the conditions of a grip interval of 20 cm and a tensile speed of 10 cm / min. The value was calculated by rounding off the first decimal place after the decimal point. The tensile strength aspect ratio was obtained by dividing the machine direction (MD) strength by the transverse direction (CD) strength and rounding off the second decimal place.

(8) Penetration of cast liquid during membrane formation A 15% by weight dimethylformamide solution of polysulfone (“Udel” (registered trademark) -P3500, manufactured by Solvay Advanced Polymers) on each separation membrane support fixed on a glass plate ( Casting liquid) is cast at room temperature (20 ° C) with a thickness of 50μm, immediately immersed in pure water at room temperature (20 ° C) and left for 5 minutes to produce a polysulfone separation membrane for seawater desalination did.
Next, the reverse surface of the produced reverse osmosis membrane was visually observed, and the penetration property of the cast liquid was evaluated in the following five stages.
5 points: There is no see-through of the casting solution.
4 points: There is almost no see-through of the casting liquid (area ratio of the show-through part is less than 5%).
3 points: See-through of cast liquid is observed (area ratio of back-through part is 5 to 50%).
2 points: Cast-through of the cast liquid is observed in the majority (area ratio of the back-through portion of 51 to 80%).
1 point: The cast liquid can be seen through almost the entire surface.

(9) Separation amount of separation membrane (μm)
Supply liquid channel material made of mesh fabric, seawater desalination reverse osmosis membrane, pressure-resistant sheet, and permeate channel material (groove width 200 μm, groove depth 150 μm, groove density 40 / 2.54 cm, thickness A spiral type fluid separation element (element) having an effective membrane area of 40 m ² was produced using a polyester single tricot having a thickness of 200 μm.
Next, the manufactured fluid separation element was subjected to a durability test under conditions of a reverse osmosis pressure of 7 MPa, a seawater salt concentration of 3 wt%, and an operating temperature of 40 ° C., and the fluid separation element was disassembled after 1000 hours of operation. Then, the amount of the separation membrane dropped into the permeate channel material was measured. The amount of sagging is measured by taking 500-3000 times photographs with a scanning electron microscope (unit: μm) for any three cross sections of the separation membrane in one fluid separation element. Calculated by rounding to the first place. The direction in which the separation membrane support and the permeate flow channel material overlap is the width direction of the nonwoven fabric when the length direction of the nonwoven fabric of the separation membrane support (nonwoven fabric direction length) is perpendicular to the groove direction of the permeate flow channel material. The test was carried out for each of the cases where the width of the nonwoven fabric was orthogonal.

Example 1
Inherent viscosity IV0.65 dried to a moisture content of 50 ppm or less, melting point 260 ° C., polyethylene terephthalate resin containing 0.3 wt% titanium dioxide, intrinsic viscosity IV0.66 dried to a moisture content of 50 ppm or less, isophthalic acid copolymerization rate 10 mol%, melting point 230 ° C., copolymer polyester resin containing 0.2 wt% titanium oxide, melted at 295 ° C. and 280 ° C., respectively, using polyethylene terephthalate resin as the core component and copolymer polyester resin as the sheath component, After spinning from the pores at a base temperature of 300 ° C. and a weight ratio of core: sheath = 80: 20, it is spun at a spinning speed of 4300 m / min by an ejector to form a concentric core-sheath filament (cross-sectional circle), and a moving net conveyor Collected as a fiber web on top. The collected fiber web is thermocompression bonded with a pair of upper and lower steel flat rolls at a flat roll surface temperature of 190 ° C. and a linear pressure of 60 kg / cm, and the average fiber diameter of the constituent filaments is 10 μm (single fiber fineness is 1.2 dtex). A spunbond nonwoven fabric having a thickness of 110 μm and a basis weight of 30 g / m ^{2 and} a spunbond nonwoven fabric having an average fiber diameter of 10 μm (single fiber fineness of 1.2 dtex), a thickness of 120 μm and a basis weight of 40 g / m ² were produced.

The obtained two spunbond nonwoven fabrics are overlapped, and a pair of flat rolls, a steel roll on the upper side and a urethane resin roll on the lower side, are used, and only the upper steel roll is heated to a temperature of 170 ° C. When the roll was stabilized at a surface temperature of 100 ° C., it was further thermocompression bonded at a linear pressure of 170 kg / cm to produce a spunbonded nonwoven fabric having a thickness of 100 μm and a basis weight of 70 g / m ² , thereby obtaining a separation membrane support.

  The obtained separation membrane support had a transverse tensile strength of 203 N / 5 cm and a tensile strength aspect ratio of 2.0.

(Example 2)
Except for the spinning speed of 4500 m / min, a spunbonded nonwoven fabric having a mean filament diameter of 10 μm (single fiber fineness of 1.2 dtex), a thickness of 230 μm, and a basis weight of 80 g / m ² by the same production method as in Example 1. Got.

The obtained spunbonded nonwoven fabric was heated to a temperature of 170 ° C. using only a pair of flat rolls, a steel roll on the upper side and a urethane resin roll on the lower side. When the temperature was stabilized at 100 ° C., thermocompression bonding was further performed at a linear pressure of 170 kg / cm to produce a spunbond nonwoven fabric having a thickness of 100 μm and a basis weight of 80 g / m ² to obtain a separation membrane support.

  The obtained separation membrane support had a transverse tensile strength of 197 N / 5 cm and a tensile strength aspect ratio of 2.1.

(Example 3)
A spunbonded nonwoven fabric having an average fiber diameter of the constituent filaments of 11 μm (single fiber fineness: 1.3 dtex), a thickness of 160 μm, and a basis weight of 50 g / m ² was obtained by the same production method as in Example 1.

The obtained spunbonded nonwoven fabric was heated to a temperature of 170 ° C. using only a pair of flat rolls, a steel roll on the upper side and a urethane resin roll on the lower side. When the temperature was stabilized at 100 ° C., thermocompression bonding was further performed at a linear pressure of 170 kg / cm to produce a spunbond nonwoven fabric having a thickness of 80 μm and a basis weight of 50 g / m ² to obtain a separation membrane support.

  The obtained separation membrane support had a transverse tensile strength of 105 N / 5 cm and a tensile strength aspect ratio of 2.2.

(Comparative Example 1)
Stretched polyethylene terephthalate short fibers having an average fiber diameter of 10 μm (fineness of 1.0 dtex) and a length of 10 mm, stretched polyethylene terephthalate short fibers having an average fiber diameter of 13 μm (fineness of 1.7 dtex) and a length of 10 mm, and average fibers Unstretched polyethylene terephthalate short fibers having a diameter of 11 μm (fineness of 1.2 dtex) and a length of 5 mm were mixed in water at a weight ratio of 20:40:40, respectively, and then sufficiently dispersed to obtain a fiber concentration of 0.05%. An aqueous slurry was prepared. This was sent to a circular paper machine, and after paper making, it was dried with a Yankee dryer at a temperature of 120 ° C. and wound up to produce a paper web. Using the pair of flat rolls, the upper side of which is a steel roll and the lower side is a cotton roll, the upper steel roll is heated to a temperature of 150 ° C., and the cotton roll is heated to a surface temperature of 80 ° C. Then, thermocompression bonding was performed at a linear pressure of 150 kg / cm to produce a papermaking nonwoven fabric having a basis weight of 80 g / m ² and a thickness of 110 μm, and a separation membrane support was obtained.

  The resulting separation membrane support had a transverse tensile strength of 85 N / 5 cm and a tensile strength aspect ratio of 5.4.

  The characteristics of the obtained separation membrane support are as shown in Table 1, but the separation membrane supports of Examples 1 to 3 all have a cast liquid back-through property of 4 or more during film formation, Moreover, there was no peeling, non-uniformity of the film, pinhole defects, etc., and the film forming property was good. In addition, the separation membrane supports of Examples 1 to 3 have a transverse tensile strength of 50 to 900 N / 5 cm and a tensile strength aspect ratio of 1.0 to 2.7. Was 50 μm or less, and was excellent in durability.

(Comparative Example 2)
A stretched polyethylene terephthalate short fiber having an average fiber diameter of 12 μm (fineness of 1.5 dtex) and a length of 10 mm, a stretched polyethylene terephthalate short fiber having an average fiber diameter of 15 μm (fineness of 2.5 dtex) and a length of 10 mm, and an average fiber A non-stretched polyethylene terephthalate short fiber having a diameter of 10 μm (fineness of 1.2 dtex) and a length of 5 mm was used to produce a papermaking nonwoven fabric having a basis weight of 50 g / m ² and a thickness of 90 μm by the same method as in Comparative Example 1. A membrane support was obtained.

  The obtained separation membrane support had a transverse tensile strength of 37 N / 5 cm and a tensile strength aspect ratio of 4.3.

(Comparative Example 3)
A polyethylene terephthalate resin dried to a moisture content of 50 ppm or less and having an intrinsic viscosity of 0.65 and a melting point of 260 ° C. and containing 0.3 wt% of titanium dioxide is spun from the pores at a die temperature of 300 ° C., and then the spinning speed by an ejector Spinning at 4000 m / min was made into a concentric core-sheath filament (circular cross section) and collected as a fiber web on a moving net conveyor. The collected fiber web is thermocompression bonded with a pair of upper and lower steel flat rolls at a flat roll surface temperature of 190 ° C. and a linear pressure of 60 kg / cm, and the average fiber diameter of the constituent filaments is 12 μm (single fiber fineness is 1.5 dtex). A spunbonded nonwoven fabric having a thickness of 200 μm and a basis weight of 60 g / m ² was obtained.

The obtained non-woven fabric was heated using a pair of flat rolls with a steel roll on the upper side and a urethane resin roll on the lower side, and only the upper steel roll was heated to a temperature of 180 ° C., and the resin roll was heated to a surface temperature of 110 ° C. Then, thermocompression bonding was further performed at a linear pressure of 170 kg / cm to produce a spunbonded nonwoven fabric having a thickness of 100 μm and a basis weight of 60 g / m ² to obtain a separation membrane support.

  The resulting separation membrane support had a transverse tensile strength of 102 N / 5 cm and a tensile strength aspect ratio of 2.8.

  The characteristics of the obtained separation membrane support are as shown in Table 1, but the separation membrane supports of Comparative Examples 1 and 2 had a cast liquid penetration through property of 4 or more during film formation. There was a membrane defect in which the separation membrane support fibers protruded from the separation membrane surface. The separation membrane support of Comparative Example 2 had a separation membrane drop of more than 50 μm, and was inferior in durability. Further, the separation membrane support of Comparative Example 3 had a tensile strength aspect ratio exceeding 2.7 and was inferior in durability.

Claims (7)

  It consists of a long-fiber non-woven fabric composed of thermoplastic continuous filaments, the tensile strength in the transverse direction of the long-fiber non-woven fabric is 50 to 900 N / 5 cm, and the tensile strength aspect ratio of the long-fiber non-woven fabric is 1.0 to 2 A separation membrane support characterized in that it is .7.   The thermoplastic continuous filament is a composite filament in which a low melting point polymer having a melting point lower by 10 to 140 ° C than the melting point of the high melting point polymer is disposed around the high melting point polymer. 2. The separation membrane support according to 1.   The separation membrane support according to claim 1, wherein the thermoplastic continuous filament is made of a polyester polymer.   The separation membrane support according to any one of claims 1 to 3, wherein an average fiber diameter of the thermoplastic continuous filament is 3 to 17 µm. 5. The separation membrane support according to claim 1, wherein the basis weight is 20 to 150 g / m ² and the thickness is 30 to 200 μm.   A separation membrane comprising a membrane having a separation function formed on the surface of the separation membrane support according to any one of claims 1 to 5.   A fluid separation element comprising the separation membrane according to claim 6.