JP2016101558A - Separation membrane support and separation membrane using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separation membrane support made of a nonwoven fabric having excellent durability and chemical resistance when supporting a microfiltration membrane, an ultrafiltration membrane, a nano filtration membrane and a separation membrane such as a reverse osmosis membrane and the like and to provide the separation membrane using the separation membrane support.SOLUTION: In a separation membrane support made of a nonwoven fabric constituted by a fiber composed mainly of a polyphenylene sulfide, the basis weight of the nonwoven fabric is 20-100 g/m, and the basis weight CV of the separation membrane support is 4.0% or less. The separation membrane: consists of core-sheath type conjugate fibers arranged with a low melting point polymer having a lower melting point than the melting point of a high melting point polymer around the high melting point polymer; and is a laminate composite nonwoven fabric integrated with a plurality of nonwoven webs by thermal compression.SELECTED DRAWING: None

Description

  The present invention relates to a separation membrane support comprising a nonwoven fabric for supporting separation membranes such as microfiltration membranes, ultrafiltration membranes, nanofiltration membranes and reverse osmosis membranes. The present invention also relates to a separation membrane using the separation membrane support.

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

  These separation membranes are roughly classified into flat membranes and hollow fiber membranes according to their shapes. Among these separation membranes, flat membranes formed mainly from synthetic polymers are generally used integrally with a support such as a nonwoven fabric or woven fabric because a membrane having a separation function is inferior in mechanical strength. There are many cases.

  In general, a membrane having a separation function and a support are integrated by a method of casting and fixing a polymer solution as a raw material for the membrane having a separation function on a support such as a nonwoven fabric or a woven fabric. The Moreover, in a semipermeable membrane such as a reverse osmosis membrane, a solution of a polymer is cast on a support such as a nonwoven fabric or a woven fabric to form a support layer, and then a semipermeable membrane is formed on the support layer. It is integrated by a method of forming.

  Therefore, for non-woven fabrics and woven fabrics that serve as a support, when a polymer solution is cast, it penetrates due to excessive permeation, the film substance peels off, and the support is fluffed, etc. Therefore, an excellent film forming property that does not cause defects such as non-uniform film formation and pinholes is required.

  Examples of the form of the fluid separation element for facilitating the handling of the separation membrane include flat membrane plate frame type, pleat type, and spiral type. For example, in the case of a plate frame type, a process of attaching a separation membrane cut to a predetermined size to the frame is required, and in the case of a spiral type, the outer peripheral portion of the separation membranes cut to a predetermined size is attached. In addition, a process of processing into an envelope shape and winding it around the water collecting pipe is necessary. Therefore, the separation membrane support is required to have excellent workability such that the membrane is not bent or rounded in these steps.

  Furthermore, 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 high dimensional stability.

  Furthermore, in the case of a reverse osmosis composite membrane used for seawater desalination etc., a seawater desalination apparatus incorporating the reverse osmosis composite membrane may be continuously operated at a certain operating pressure. If so, there is a case where the operation pressure is changed each time in response to a change in the quality and temperature of the supplied seawater or a change in the management value of the target water production amount. Actually, the latter type of operation is common, but in that case, the reverse osmosis composite membrane expands and contracts in the thickness direction due to fluctuations in the operating pressure applied in the thickness direction of the reverse osmosis composite membrane. Since the operation may be repeated and the support membrane of the reverse osmosis composite membrane may be peeled off, the separation membrane support is also required to have high peel strength when the separation membrane is formed.

  In recent years, the use of natural resources (shale gas, shale oil, etc.) existing in shale existing in the vicinity of several thousand meters underground has been promoted. Shale gas is recovered by hydraulically crushing the shale layer storing it and recovering resources from the cracks. For this purpose, a large amount of chemicals such as acids and surfactants that dissolve the formation are included. Of water. The wastewater generated by this mining operation contains many chemicals and oils. This waste water is reused after being subjected to pretreatment such as neutralization treatment and then subjected to membrane filtration treatment with a separation membrane.

  When oil is contained in the wastewater to be treated, the separation membrane is significantly contaminated. When the contamination of the separation membrane progresses, the processing capability of the separation membrane decreases. Therefore, membrane cleaning is performed using a cleaning liquid to which acid or alkali is added.

  Conventionally, as a separation membrane support, many separation membrane supports made of a nonwoven fabric using polyester fibers have been proposed from the viewpoint of required characteristics and cost. For example, a separation membrane support made of a nonwoven fabric having excellent mechanical strength that does not deform or break due to pressure applied when used as a separation membrane or a fluid separation element has been proposed (Patent Literature). 1). Separately, by using polyester fiber to make a nonwoven fabric with a three-layer structure of spunbond-meltblown-spunbond, it has excellent anti-back-through prevention and integrity with coating resin even if it is thin, and has practical strength. It has been proposed that a separation membrane support is obtained (see Patent Document 2).

  However, in the proposal of the conventional separation membrane support made of polyester fiber, no mention was made of durability against chemicals contained in waste water or cleaning liquid. In recent years, there has been a demand for a separation membrane and a separation membrane support that are excellent in oil resistance and chemical resistance and that can be suitably used for the treatment of waste liquid containing oil and chemicals.

JP2013-71106A JP 2012-76042 A

The object of the present invention is a separation membrane support that supports separation membranes such as microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, and reverse osmosis membranes, and is composed of a nonwoven fabric having excellent smoothness and chemical resistance. It is to provide a membrane support.
Another object of the present invention is to provide a separation membrane using the above-mentioned separation membrane support.

The present invention is to solve the above problems, and the separation membrane support of the present invention is a separation membrane support made of a nonwoven fabric, wherein the nonwoven fabric is composed of fibers mainly composed of polyphenylene sulfide. The basis weight of the nonwoven fabric is 20 g / m ² or more and 100 g / m ² or less, and the basis weight CV is 4.0% or less.

  According to a preferred aspect of the separation membrane support of the present invention, the fibers constituting the nonwoven fabric are core-sheath type composite fibers.

According to a preferred aspect of the separation membrane support of the present invention, the nonwoven fabric is a laminated composite nonwoven fabric in which a plurality of nonwoven webs are integrated by thermocompression bonding.
The separation membrane of the present invention is a separation membrane in which a membrane having a separation function is formed on the surface of the above-mentioned separation membrane support.

  According to the present invention, a separation membrane support comprising a nonwoven fabric that supports separation membranes such as microfiltration membranes, ultrafiltration membranes, nanofiltration membranes and reverse osmosis membranes, and has excellent smoothness and excellent chemical resistance A separation membrane support made of a nonwoven fabric is obtained. By having superior chemical resistance compared to conventional separation membrane supports, there is little deterioration due to chemicals and heat, and long-term operation is possible without reducing the performance of the separation membrane support and separation membrane. .

The separation membrane support of the present invention is a separation membrane support composed of a nonwoven fabric, wherein the nonwoven fabric is composed of fibers mainly composed of polyphenylene sulfide, and the basis weight of the nonwoven fabric is 20 g / m ² or more and 100 g / m. It is a separation membrane support having a CV of ² or less and a basis weight CV of 4.0% or less.

  The separation membrane support of the present invention is a separation membrane support used by forming a membrane having a separation function on the surface thereof. The separation membrane support of the present invention is composed of a nonwoven fabric composed of fibers mainly composed of polyphenylene sulfide. That is, it is important that the nonwoven fabric constituting the separation membrane support of the present invention is composed of fibers mainly composed of polyphenylene sulfide. By doing in this way, the outstanding heat resistance, a flame retardance, and chemical resistance can be obtained. Here, having polyphenylene sulfide as a main component means that polyphenylene sulfide accounts for 85% by mass or more of the whole.

  Examples of the fibers constituting the nonwoven fabric constituting the separation membrane support of the present invention include single-component fibers, multiple-component composite fibers, and so-called mixed fiber in which a plurality of types of fibers are mixed. However, in the separation membrane support of the present invention, a composite fiber in which a low melting point polymer having a melting point lower than that of the high melting point polymer is arranged around the high melting point polymer is preferably used. By using such composite fibers, the fibers in the nonwoven fabric are firmly bonded to each other by thermocompression bonding, so that in addition to improving the smoothness of the nonwoven fabric, when the nonwoven fabric is used as a separation membrane support, a polymer solution due to fluffing Non-uniformity during casting and film defects can be suppressed. In addition, composite fibers have a larger number of adhesion points than mixed fibers in which fibers consisting only of high-melting polymers and fibers consisting only of low-melting polymers are mixed. Lead to improved mechanical strength.

  The melting point difference between the high melting point polymer and the low melting point polymer in the composite fiber is preferably 10 to 140 ° C. When the difference in melting point is preferably 10 ° C. or higher, more preferably 20 ° C. or higher, and further preferably 30 ° C. or higher, thermal adhesiveness that contributes to improvement of mechanical strength can be obtained. On the other hand, when the difference in melting point is preferably 140 ° C. or less, more preferably 120 ° C. or less, and further preferably 100 ° C. or less, the low melting point polymer component is fused to the heat roll at the time of thermocompression bonding using the heat roll. And it can suppress that productivity falls.

  The melting point of the high-melting polymer is 160 to 320 ° C. from the viewpoint that the film-forming property when the separation membrane is formed on the separation membrane support of the present invention is good and a separation membrane having excellent durability can be obtained. It is preferable that The melting point of the high-melting polymer is preferably 160 ° C. or higher, more preferably 170 ° C. or higher, and even more preferably 180 ° C. or higher. Excellent in properties. On the other hand, the melting point of the high-melting polymer is preferably 320 ° C. or lower, more preferably 300 ° C. or lower, and further preferably 280 ° C. or lower. It can suppress that it falls.

  The melting point of the low melting point polymer is preferably 120 ° C. or higher, more preferably 140 ° C. or higher.

  The proportion of the low melting point polymer in the composite fiber is preferably 10 to 70% by mass from the viewpoint of obtaining a nonwoven fabric suitable for the separation membrane support. The proportion of the low-melting polymer is preferably 10% by mass or more, more preferably 15% by mass or more, and still more preferably 20% by mass or more to obtain thermal adhesiveness that can be used as a separation membrane support. Can do. On the other hand, the proportion of the low-melting point polymer is preferably 70% by mass or less, more preferably 60% by mass or less, and still more preferably 50% by mass or less. It can suppress that a coalescence component fuse | melts and productivity falls.

  Additives such as a crystal nucleating agent, a matting agent, a lubricant, a pigment, an antifungal agent, an antibacterial agent, and a flame retardant can be added to the nonwoven fabric as long as the effects of the present invention are not impaired. Especially, metal oxides, such as a titanium oxide, have the effect of improving the adhesiveness of a nonwoven fabric by increasing thermal conductivity in the case of the thermocompression-bonding by the hot roll of a nonwoven fabric. In addition, aliphatic bisamides such as ethylene bis-stearic acid amide and / or alkyl-substituted aliphatic monoamides have the effect of improving adhesion stability by increasing the releasability between the hot roll and the nonwoven web.

Examples of the composite form of the composite fiber include composite forms such as a concentric core-sheath type, an eccentric core-sheath type, and a sea-island type from the viewpoint that a thermal bonding point between fibers can be efficiently obtained.
Moreover, as cross-sectional shape of the fiber which comprises a nonwoven fabric, cross-sectional shapes, such as a circular cross section, a flat cross section, a polygonal cross section, a multileaf cross section, and a hollow cross section, can be mentioned.

  Among them, the concentric core-sheath type as a composite form is a circular cross section or a flat cross section as a fiber cross-sectional shape, and fibers can be firmly bonded together by thermocompression bonding. The body thickness can be reduced, the smoothness can be improved, and the separation membrane area per fluid separation element unit can be increased.

  It is preferable that the average single fiber diameter of the fiber which comprises a nonwoven fabric is 3-30 micrometers. By setting the average single fiber diameter of the fibers to preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 7 μm or more, the spinnability is hardly lowered during the production of the nonwoven fabric, and the voids inside the separation membrane support are maintained. Therefore, a polymer membrane solution cast at the time of film formation quickly penetrates into the inside of the separation membrane support and adheres firmly, whereby a separation membrane having excellent membrane peel strength can be obtained. On the other hand, when the average single fiber diameter of the fibers is preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 20 μm or less, a nonwoven fabric and a separation membrane support excellent in uniformity can be obtained. Since the support can be densified, there is little over-penetration during casting of the polymer solution, and good film forming properties can be obtained.

  As the nonwoven fabric constituting the separation membrane support of the present invention, a spunbond nonwoven fabric produced by a spunbond method is preferably used. By using a spunbond nonwoven fabric, which is a long-fiber nonwoven fabric composed of thermoplastic filaments, non-uniformity during casting of a polymer solution caused by fuzz, which tends to occur when short-fiber nonwoven fabric is used, and membrane defects Can be suppressed. In addition, the spunbonded nonwoven fabric is superior in mechanical strength, has good film-forming properties when used as a separation membrane support, and can provide a separation membrane sheet with excellent durability.

  In addition, the nonwoven fabric constituting the separation membrane support of the present invention can be a laminate composed of a plurality of nonwoven webs (laminated composite nonwoven fabric), which can provide a separation membrane support with better uniformity. Furthermore, the density distribution in the thickness direction of the support can be easily adjusted. As an aspect of the laminate, for example, a laminate of two layers of spunbond nonwoven fabric (nonwoven web) or a melt blown nonwoven fabric (nonwoven web) disposed between two layers of spunbond nonwoven fabric (nonwoven web) 3 A laminate having a layer structure and the like can be mentioned, and at least one layer is preferably a spunbond nonwoven fabric (nonwoven web), and a more preferable embodiment is composed of only a spunbond nonwoven fabric (nonwoven web).

It is important that the basis weight of the laminated composite nonwoven fabric constituting the separation membrane support of the present invention is 20 g / m ² or more and 100 g / m ² or less. By setting the basis weight to 20 g / m ² or more, preferably 30 g / m ² or more, more preferably 40 g / m ² or more, it is possible to obtain a good film-forming property with less over-penetration during casting of the polymer solution. A separation membrane support having high mechanical strength and excellent durability can be obtained. On the other hand, by setting the basis weight to 100 g / m ² or less, preferably 90 g / m ² or less, more preferably 80 g / m ² or less, the thickness of the separation membrane support is reduced, and the separation membrane per fluid separation element unit is reduced. The area can be increased.
When the laminated composite nonwoven fabric of the present invention is produced by the spunbond method, it can be adjusted to a desired basis weight by changing various conditions such as the collection speed of the nonwoven web and the discharge amount from the die. The basis weight of the laminated composite nonwoven fabric can be adjusted by adjusting the number of nonwoven webs to be laminated.

Nonwoven Fabric The thickness of the laminated composite nonwoven fabric constituting the separation membrane support of the present invention is preferably 0.03 to 0.20 mm. By setting the thickness of the nonwoven fabric to preferably 0.03 mm or more, more preferably 0.04 mm or more, and even more preferably 0.05 mm or more, a good film-forming property can be obtained with less excessive permeation and the like during casting of a polymer solution In addition, the curl after film formation can be suppressed, and a separation membrane support having high membrane peel strength and mechanical strength and excellent durability can be obtained. On the other hand, the thickness of the nonwoven fabric is preferably 0.13 mm or less, more preferably 0.12 mm or less, and even more preferably 0.11 mm or less, thereby reducing the thickness of the separation membrane support and per fluid separation element unit. The separation membrane area can be increased.
It is important that the basis weight CV of the laminated composite nonwoven fabric constituting the separation membrane support of the present invention is 4.0% or less. By setting the basis weight CV of the laminated composite nonwoven fabric to 4.0% or less, it is possible to reduce the number of portions having a low basis weight locally and to process the cast liquid without see-through during film formation. Further, the basis weight distribution of the separation membrane support can be reduced, and the separation membrane area per liquid separation element unit can be increased.

  Moreover, the nonwoven fabric with a basis weight CV of 4.0% or less constituting the separation membrane support of the present invention can be a laminated nonwoven fabric in which a plurality of nonwoven webs are laminated. As an aspect of the laminate, for example, a laminate of two layers of spunbond nonwoven fabric (nonwoven web) or a melt blown nonwoven fabric (nonwoven web) disposed between two layers of spunbond nonwoven fabric (nonwoven web) 3 A laminate having a layer structure and the like can be mentioned, and at least one layer is preferably a spunbond nonwoven fabric, and a more preferable embodiment is composed of only a spunbond nonwoven fabric.

  In the nonwoven fabric constituting the separation membrane support of the present invention, the back surface of the nonwoven fabric preferably has a Beck smoothness of 5 to 35 seconds according to JIS P8119 (1998 edition). The back surface of the non-woven fabric is preferably 5 seconds or more, more preferably 10 seconds or more, and even more preferably 15 seconds or more. The polymer solution cast on the support can be sufficiently solidified after being sufficiently infiltrated into the support, and the membrane separation strength of the formed separation membrane can be improved. In addition, it is possible to suppress scratches on the separation membrane surface caused by rubbing between the film-forming surface and the back surface in the winding process during the production of the separation membrane. On the other hand, by setting the Beck smoothness of the back surface of the nonwoven fabric to preferably 35 seconds or less, more preferably 30 seconds or less, and even more preferably 25 seconds or less, the air inside the separation membrane support is quickly discharged during the production of the separation membrane. It is possible to suppress a partial decrease in film peeling strength and to suppress the occurrence of film forming defects such as pinholes.

  The Beck smoothness of the laminated composite nonwoven fabric constituting the separation membrane support of the present invention can be adjusted by appropriately changing various conditions such as temperature, pressure and clearance when the nonwoven web is thermocompression bonded. .

Next, a method for producing the separation membrane support of the present invention will be described.
In the present invention, when a composite fiber such as a core-sheath type is used as the fiber constituting the nonwoven fabric, a normal composite method can be employed.

In the case of the spunbond method as a method for producing a nonwoven fabric, a molten thermoplastic polymer is extruded from a nozzle, drawn and drawn by a high-speed suction gas, and then spun. A long-fiber nonwoven fabric can be produced by forming a woven web and further integrating it by continuous thermocompression bonding. At that time, the spinning speed is preferably 2000 m / min or more, more preferably 3000 m / min or more, and still more preferably 4000 m / min or more in order to highly orient and crystallize the fibers constituting the fiber web.
In addition, when the melt blow method is used as a method for producing a nonwoven fabric, the thermoplastic polymer is stretched to ultrafine fibers by spraying a heated high-speed gas fluid on the molten thermoplastic polymer, and then collected and collected. A fiber nonwoven fabric can be produced.

  Moreover, if it is a short fiber nonwoven fabric, the method of cut | disconnecting a long fiber and making it into a short fiber, and making it a nonwoven fabric by the dry method or a wet method is used preferably.

  Moreover, as a manufacturing method of the lamination | stacking composite nonwoven fabric which consists of a laminated body of the several nonwoven web mentioned above, in the case of the manufacturing method of the lamination | stacking composite nonwoven fabric which consists of a nonwoven fabric of 2 layers, for example, the nonwoven web of a temporarily-bonded state A method in which two layers are laminated and then integrated by thermocompression bonding is preferably used. In addition, as a method for producing a laminated composite nonwoven fabric comprising a laminate having a three-layer structure in which a melt blown nonwoven web is disposed between two layers of a spunbond nonwoven web, a method for producing a layer between two layers of a temporarily bonded spunbond nonwoven web is used. In addition, the melt-blown nonwoven webs produced on separate lines are stacked so as to be sandwiched, and then integrated by thermocompression bonding. A method of collecting, laminating, and thermocompression-bonding the nonwoven webs extruded and fiberized from the nozzles in order can be preferably used.

  In the case of a dry short fiber nonwoven fabric or a papermaking nonwoven fabric, a method in which a plurality of wound nonwoven webs are overlapped and then integrated by thermocompression bonding can be preferably used.

  Here, as a method of thermocompression bonding for integrating the laminated nonwoven web, in order to obtain a separation membrane having excellent mechanical strength and durability and excellent smoothness, the surface is smooth and the machine From the viewpoint of excellent mechanical strength, a method of thermocompression bonding and integrating the nonwoven webs laminated by a pair of upper and lower flat rolls can be preferably used. This flat roll is a metal roll or elastic roll with no irregularities on the surface of the roll, and a pair of metal roll and metal roll or a pair of metal roll and elastic roll is used. Can do. In particular, it is possible to improve the smoothness of the separation membrane when it is used as a separation membrane support by suppressing the fusion of fibers on the surface of the nonwoven fabric and maintaining the form. A method of thermocompression bonding using a roll and an elastic roll is preferably used. Furthermore, since the excessive permeation of the polymer solution cast on the support during the production of the separation membrane can be suppressed, the surface of the nonwoven web in contact with the metal roll is used as the film formation surface of the separation membrane support, and the elastic roll It is preferable to use the surface in contact with the back surface of the separation membrane support.

  Here, the elastic roll is a roll made of a material having elasticity compared to a metal roll. Examples of the material of the elastic roll include so-called paper rolls such as paper, cotton, and aramid paper, and rolls made of resin such as urethane resin, epoxy resin, silicon resin, polyester resin, and hard rubber.

The hardness (Shore D) of the elastic roll is preferably 70 to 99. By setting the hardness (Shore D) of the elastic roll to preferably 70 or more, more preferably 75 or more, and even more preferably 80 or more, when the surface of the nonwoven web in contact with the elastic roll is used as the back surface, the separation membrane Improves the smoothness of the back surface of the support, suppresses permeation of coagulation liquid containing water as the main component into the separation membrane support during the production of the separation membrane, and the polymer solution cast on the support It is possible to improve the membrane peeling strength of the formed separation membrane by solidifying after sufficiently permeating into the membrane.
On the other hand, when the elastic roll has a hardness (Shore D) of preferably 99 or less, more preferably 95 or less, and even more preferably 91 or less, when the surface of the nonwoven web in contact with the elastic roll is used as the back surface, By suppressing excessive improvement in the smoothness of the back surface of the separation membrane support, it becomes possible for a coagulation liquid containing water as a main component to penetrate into the separation membrane support during the production of the separation membrane, It is possible to suppress excessive penetration of the extended polymer solution, that is, back-through.

  In addition, as a configuration of two or more flat rolls, a combination of metal / elastic rolls in a manufacturing process is used continuously or discontinuously. A three-roll method such as a method, elasticity / metal / elasticity, elasticity / metal / metal, and metal / elasticity / metal can also be preferably used.

  In the case of 2 rolls × 2 sets, since heat and pressure can be applied twice to the nonwoven fabric, it becomes easy to control the characteristics of the nonwoven web, and it is possible to increase the speed during production. Further, since the first and second sets of elastic roll contact surfaces can be easily reversed, the surface characteristics of the front and back surfaces of the nonwoven fabric can be easily controlled.

  On the other hand, in the case of the three-roll method, for example, by folding back a nonwoven fabric thermocompression bonded between elastic 1 / metal / elastic 2 elastic 1 / metal roll and further thermocompression bonding between 2 metal / elastic 2 rolls, Heat and pressure can be applied twice to the nonwoven fabric in the same manner as the roll × 2 set method, and the equipment cost can be reduced and the space can be saved as compared with the continuous two roll × 2 set method.

  In the production method using two or more of these elastic rolls, the hardness (Shore D) of the nonwoven fabric, the elastic roll contacting the first stage, and the elastic roll contacting the second stage can be changed.

  The surface temperature of the metal roll is preferably 20 to 90 ° C., more preferably 30 to 70 ° C. lower than the melting point of the polymer constituting at least the surface of the fibers constituting the nonwoven web. If the surface temperature of the metal roll is 20 ° C. or more lower than the melting point of the polymer constituting at least the surface of the fibers constituting the nonwoven web, excessive fusion of the nonwoven web surface fibers can be suppressed, A polymer support solution can easily penetrate and a separation membrane support excellent in membrane adhesive strength can be obtained. On the other hand, if the difference between the surface temperature of the metal roll and the melting point of the polymer constituting at least the surface of the fibers constituting the nonwoven web is 90 ° C. or less, the fibers constituting the nonwoven fabric are firmly bonded to each other. By increasing the density of the nonwoven fabric, it is possible to obtain a separation membrane support excellent in mechanical strength, and it is possible to obtain good film-forming properties with little over-permeation during casting of a polymer solution. .

Furthermore, it is also a preferable aspect to provide a temperature difference between the metal roll and the elastic roll so that the surface temperature of the elastic roll is 10 to 120 ° C. lower than the surface temperature of the metal roll.
As the heating method of the metal roll, an induction heat generation method, a heat medium circulation method, or the like can be preferably used, but since a separation membrane support excellent in uniformity can be obtained, the temperature difference in the nonwoven fabric width direction becomes a central value. On the other hand, it is preferably within ± 3 ° C., more preferably within ± 2 ° C.
The heating method for the elastic roll is a contact heating method that is heated by contact with a metal roll heated during pressurization, or a non-contact heating method that uses an infrared heater or the like that can control the surface temperature of the elastic roll more strictly. Etc. can be preferably used. The temperature difference in the nonwoven fabric width direction of the elastic roll is preferably within ± 10 ° C., more preferably within ± 5 ° C. with respect to the center value. In order to more strictly control the temperature difference in the width direction of the nonwoven fabric of the elastic roll, an infrared heater or the like can be divided and installed in the width direction, and the respective outputs can be adjusted.

  Moreover, it is preferable that the linear pressure of a flat roll is 196-4900 N / cm. The linear pressure of the flat roll is more preferably 490 to 4900 N / cm, and further preferably 980 to 4900 N / cm. If the linear pressure of the flat roll is 196 N / cm or more, a separation membrane support excellent in mechanical strength can be obtained by firmly bonding the fibers constituting the nonwoven fabric and increasing the density of the nonwoven fabric. In addition, it is possible to obtain a good film forming property with less permeation and the like during casting of the polymer solution. On the other hand, if the linear pressure of the flat roll is 4900 N / cm or less, excessive fusion of the nonwoven fabric surface fibers can be suppressed, and the penetration of the polymer solution into the nonwoven fabric is not hindered, and the membrane peel strength is increased. An excellent separation membrane support can be obtained.

In the method for producing a separation membrane support of the present invention, it is preferable that 2 to 5 laminated nonwoven web layers are integrated by thermocompression to form a laminated composite nonwoven fabric. If the number of laminated layers is two or more, the texture is improved as compared with a single layer, and sufficient uniformity can be obtained. Moreover, if the number of laminated layers is 5 or less, it is possible to suppress wrinkling during lamination and to suppress delamination between layers.
In addition, as a thermocompression bonding method for spunbond nonwoven webs, a two-stage adhesive method is used to control the nonwoven web properties more precisely, rather than thermocompressing the nonwoven webs with only one pair of flat rolls. Can also be adopted. That is, the nonwoven web is preliminarily bonded by preliminarily thermocompression bonding between a pair of flat rolls or by preliminarily thermocompression bonding between a single flat roll and a collection conveyor used for collecting fiber webs. It is also possible to preferably use a two-step bonding method in which after the step is obtained, the non-woven fabric in a temporarily bonded state is wound up in a continuous process, and then it is further thermocompression bonded between flat rolls.

  In the first stage pre-thermocompression bonding in this two-stage bonding method, the nonwoven fabric can be densified at the time of the second stage thermocompression bonding. 3 is preferable. In this case, the temperature of the flat roll used for the first stage pre-thermocompression bonding is preferably 20 to 120 ° C. lower than the melting point of the fibers constituting the nonwoven web, and the linear pressure is preferably 5 to 70 kg / cm.

  The separation membrane of the present invention is a separation membrane formed by forming a membrane having a separation function on the above-mentioned separation membrane support. Examples of such separation membranes include semipermeable membranes such as microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, and reverse osmosis membranes.

  As a method for producing the separation membrane, a method of forming a membrane having a separation function by casting a polymer solution on at least one surface of the above-mentioned separation membrane support is preferably used. In the case where the separation membrane is a semipermeable membrane, a membrane having a separation function is a composite membrane including a support layer and a semipermeable membrane layer, and the composite membrane is laminated on at least one surface of the separation membrane support. This is a preferred form.

  The polymer solution cast on the separation membrane support of the present invention has a separation function when it becomes a membrane. For example, polyarylethersulfone such as polysulfone and polyethersulfone, polyimide, polyfluoride, and the like. Solutions such as vinylidene chloride and cellulose acetate are preferably used. In particular, a solution of polysulfone and polyarylethersulfone is preferably used in terms of chemical, mechanical and thermal stability. The solvent can be appropriately selected according to the film forming substance. As the semipermeable membrane when the separation membrane is a composite membrane comprising 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.

  The separation membrane of the present invention can be housed in a casing or the like and used as a liquid separation element in a seawater desalination apparatus. Examples of the form include flat membrane plate frame type, pleated type and spiral type fluid separation elements. In particular, a spiral type fluid separation element is preferably used in which the separation membrane is spirally wound around the water collecting pipe together with the permeate flow path material and the supply liquid flow path material. A plurality of fluid separation elements can be connected in series or in parallel to form a separation membrane unit.

[Measuring 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. Further, in the differential scanning calorimeter, for a resin whose melting endotherm curve does not show an extreme value, 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) Melt flow rate (MFR) (g / 10 min)
The MFR of the resin used was measured under the conditions of a measurement temperature of 315.5 ° C. and a measurement load of 5 kg according to ASTM D1238-70.

(3) Average single fiber diameter (μm)
The average single fiber diameter is obtained by randomly collecting 10 small sample pieces from a nonwoven fabric, taking 500 to 3000 times photographs with a scanning electron microscope, and measuring the diameter of 100 single fibers, 10 from each sample. The average value was calculated by rounding off the first decimal place.

(4) Non-woven fabric thickness (mm)
The thickness of the nonwoven fabric is based on JIS L1906 (2000 edition) 5.1, using a pressurizer with a diameter of 10 mm, and 10 points in 0.01 mm increments at a load of 10 kPa at an equal interval per 1 m in the width direction of the nonwoven fabric. The average value was calculated by rounding off the third decimal place.

(5) Fabric weight of nonwoven fabric (g / m ² )
The basis weight of the nonwoven fabric is to collect three 30 cm × 50 cm nonwoven fabrics, measure the mass of each sample (nonwoven fabric), convert the average value of the obtained values per unit area, and place the first decimal place. Calculated by rounding off.

(6) Fabric basis weight CV (%)
The non-woven fabric CV is a total of 256 5 cm × 5 cm non-woven fabrics each in the longitudinal and lateral directions, and the mass of each sample (nonwoven fabric) is measured, and the average value of the obtained values is a unit. Converted per area, the first decimal place was rounded off, the basis weight of the nonwoven fabric was determined, and the CV value was determined.

[Example 1]
(Core component)
100 mol% linear polyphenylene sulfide resin (manufactured by Toray Industries, Inc., product number: E2280, melting point: 281 ° C., MFR: 160 g / 10 min) is dried at 160 ° C. for 10 hours in a nitrogen atmosphere as a core component. Using.

(Sheath component)
100 mol% linear polyphenylene sulfide (PPS) resin (manufactured by Toray Industries, Inc., product number: M2588, melting point: 281 ° C., MFR: 300 g / 10 min) was dried at 160 ° C. for 10 hours in a nitrogen atmosphere, Used as a sheath component.

(Spinning and nonwoven web collection)
The above core component and sheath component are each melted with an extruder and weighed so that the mass ratio of the core component to the sheath component is 80:20, and the spinning temperature is 315 ° C. and the pore diameter is 0.55 mm. A core-sheath type composite fiber was spun from the core-sheath type spinneret at a single hole discharge rate of 1.37 g / min. The spun core-sheath type composite fiber is cooled and solidified in an atmosphere at a room temperature of 20 ° C., passed through a rectangular ejector installed at a distance of 550 mm from the rectangular core-sheath type spinneret, and a temperature of 200 ° C. with an air heater. The heated air was sprayed from the ejector at an ejector pressure of 0.17 MPa, and the yarn was pulled, stretched, collected on a moving net, and formed into a nonwoven web. The obtained core-sheath type composite continuous fiber had an average single fiber diameter of 16 μm, a spinning speed of 4,800 m / min, and a spinnability of 0 times in 1 hour spinning.

(Temporary bonding)
Subsequently, the nonwoven web was temporarily bonded using a pair of metal upper and lower calendar rolls installed on the inline at a linear pressure of 200 N / cm and a temporary bonding temperature of 90 ° C., and the basis weight was 36 g / m ² . The resulting spunbond (SB) nonwoven web (a) was obtained.

(Laminated thermocompression bonding)
Two pieces of the obtained spunbond nonwoven web (a) in a temporarily bonded state are overlapped, and the laminated nonwoven web is a resin elastic roll having a hardness (Shore D) of 91 and a surface average roughness Ra of 4 μm. The inside is a metal roll, the bottom is hardness (Shore D) 75, the surface average roughness Ra is 4 μm, and a pair of elastic rolls made of resin. The laminated non-woven web is folded and thermocompression bonded through the top-intermediate, and the back surface of the laminated composite nonwoven fabric obtained by thermocompression bonding is contacted with a metal cold roll having a surface temperature of 45 ° C. A polyphenylene sulfide spunbonded non-woven fabric (laminated composite non-woven fabric) having a basis weight of 72 g / m ² , a thickness of 0.09 mm, and a basis weight CV of 3.0% to obtain a separation membrane support It was. The surface temperature of the three flat rolls at this time was 140 ° C. on the top, 180 ° C. on the inside, 140 ° C. on the bottom, and the linear pressure was 1715 N / cm. The evaluation results are shown in Table 1.

(Separation membrane formation)
The obtained separation membrane support was unwound at a speed of 12 m / min, and a 16% by mass dimethylformamide solution (casting solution) of polysulfone (“Udel” (registered trademark) -P3500, manufactured by Solvay Advanced Polymers) was further formed thereon. Was cast at room temperature (20 ° C.) with a thickness of 50 μm, and immediately immersed in pure water at room temperature (20 ° C.) for 10 seconds, then immersed in pure water at a temperature of 75 ° C. for 120 seconds, followed by 90 ° C. The film was immersed in pure water at a temperature for 120 seconds, wound up with a tension of 100 N / full width, a polysulfone membrane was formed on the separation membrane support, and a separation membrane was prepared. The produced separation membrane was excellent in smoothness and chemical resistance, and could be suitably used for wastewater treatment containing oil and chemicals.

[Example 2]
In the spinning, non-woven web collection and temporary bonding steps, a temporarily bonded spunbonded non-woven web (b) was obtained so that the basis weight was 25 g / m ² . A polyphenylene sulfide span having a basis weight of 50 g / m ² , a thickness of 0.07 mm, and a basis weight of CV 3.3%, except that this spunbond nonwoven web (b) is used. A bond nonwoven fabric (laminated composite nonwoven fabric) was produced to obtain a separation membrane support. The evaluation results are shown in Table 1.

[Example 3]
In the spinning, non-woven web collection, and temporary bonding steps, a temporarily bonded spunbond nonwoven web (c) was obtained so that the basis weight was 15 g / m ² . A polyphenylene sulfide having a basis weight of 30 g / m ² , a thickness of 0.04 mm and a basis weight of CV of 3.2%, except that this spunbond nonwoven web (c) is used. A spunbond nonwoven fabric (laminated composite nonwoven fabric) was produced to obtain a separation membrane support. The evaluation results are shown in Table 1.

[Example 4]
(Spinning and nonwoven web collection)
The core component used in Example 1 was melted with an extruder and spun at a spinning temperature of 315 ° C. from a spinneret with a hole diameter of 0.55 mm at a single hole discharge rate of 1.37 g / min. The spun fiber was cooled and solidified in an atmosphere at a room temperature of 20 ° C., passed through a rectangular ejector installed at a distance of 550 mm from the die, and air heated to a temperature of 200 ° C. with an air heater was ejector pressure 0.17 MPa. And then ejected from the ejector, pulled and stretched the yarn, and collected on a moving net to form a nonwoven web. The discharge rate was adjusted so that the basis weight of the spunbond nonwoven web (d) was 30 g / m ² .

Subsequently, after the polyphenylene sulfide resin having a MFR of 160 g / min and a melting point of 281 ° C. dried to a moisture content of 10 ppm was melted at a temperature of 315 ° C. and spun from the pores of the spinneret, 1000 Nm ³ / hr The melt-blown nonwoven web (e) was collected on the spunbond nonwoven web (d) on a moving net conveyor by spinning / spraying by spraying heated air / m. The discharge rate was adjusted so that the basis weight of the melt blown (MB) nonwoven web (e) was 10 g / m ² .

Further, the spunbond nonwoven web (f) was collected on the meltblown nonwoven web (e) under the same conditions as the spunbond nonwoven web (d). The discharge rate was adjusted so that the basis weight of the spunbond nonwoven web (f) was 30 g / m ² .

(Preliminary thermocompression bonding)
The laminated non-woven web collected as described above is passed between a metal flat roll and a net conveyor, preliminarily thermocompression bonded with a flat roll surface temperature of 180 ° C., a linear pressure of 294 N / cm, and a basis weight of 70 g / m. ² to produce a laminated composite nonwoven web having a three-layer structure of spunbond / meltblown / spunbond in a temporarily bonded state having a thickness of 0.35 mm.

(Laminated thermocompression bonding)
The obtained laminated composite nonwoven web in a temporarily bonded state is thermocompression-bonded between a pair of two flat rolls with a metal roll on top, the basis weight is 70 g / m ² , the thickness is 0.09 mm, A polyphenylene sulfide composite nonwoven fabric having a basis weight CV of 2.8% was produced to obtain a separation membrane support. Obtained. The surface temperature of the two flat rolls at this time was 230 ° C. on the top, 130 ° C. on the bottom, and the linear pressure was 1519 N / cm. The evaluation results are shown in Table 1.

(Separation membrane formation)
Using the obtained laminated composite nonwoven fabric, a polysulfone membrane was formed on the separation membrane support in the same manner as in Example 1 to obtain a separation membrane. The obtained separation membrane was extremely excellent in smoothness, excellent in chemical resistance, and could be suitably used for waste water treatment containing oil and chemicals.

[Comparative Example 1]
(Core component and sheath component)
The same PPS resin as in Example 1 was used as the core component and the sheath component.

(Spinning and nonwoven web collection)
In the same manner as in Example 1, it was collected as a nonwoven web on a net conveyor.

(Temporary bonding and thermal bonding)
Subsequently, the nonwoven web was temporarily bonded at a linear pressure of 200 N / cm and a temporary bonding temperature of 90 ° C. using a pair of upper and lower metal calendar rolls installed on the inline. Subsequently, a nonwoven fabric was manufactured by thermal bonding at a linear pressure of 1000 N / cm and a thermal bonding temperature of 200 ° C. with a pair of upper and lower metal calender rolls to obtain a separation membrane support. The obtained membrane support had a basis weight of 72 g / m ² , a thickness of 0.09 mm, and a basis weight CV of 4.8%. The evaluation results are shown in Table 2.

(Separation membrane formation)
A separation membrane was obtained in the same manner as in Example 1 using the composite nonwoven fabric obtained above. The obtained separation membrane was inferior in smoothness and could not be suitably used when a liquid separation element unit was formed.

[Comparative Example 2]
(Core component)
The same PPS resin as in Example 1 was used as the core component.

(Sheath component)
The sheath component was not used.

(Spinning, nonwoven web collection, temporary bonding and thermal bonding)
The core component was melted with an extruder and weighed, and was spun from a rectangular single component spinneret with a spinning temperature of 315 ° C. and a hole diameter of φ0.50 mm at a single hole discharge rate of 1.37 g / min. Thereafter, in the same manner as in Comparative Example 1, spinning and nonwoven web formation were performed to produce a nonwoven fabric, and a separation membrane support was obtained. The obtained membrane support had a basis weight of 72 g / m ² , a thickness of 0.09 mm, and a basis weight CV of 5.3%. The evaluation results are shown in Table 2.

(Separation membrane formation)
Using the obtained nonwoven fabric, a separation membrane support was obtained in the same manner as in Example 1. The obtained separation membrane was inferior in smoothness and could not be suitably used when a liquid separation element unit was formed.

[Comparative Example 3]
(Core component)
An intrinsic viscosity IV of 0.65, a melting point of 260 ° C., and a polyethylene terephthalate resin having a titanium oxide content of 0.3 mass% dried to a moisture content of 50 ppm or less were used as a core component.

(Sheath component)
A copolymer polyethylene terephthalate resin having an intrinsic viscosity IV of 0.66, an isophthalic acid copolymerization ratio of 11 mol%, a melting point of 230 ° C., and a titanium oxide content of 0.2 mass% is reduced to a water content of 50 ppm or less. The dried product was used as a sheath component.

(Spinning and nonwoven web collection)
The core component and the sheath component are melted at temperatures of 295 ° C. and 270 ° C., respectively. After spinning from the pores, the yarn was spun by an ejector at a spinning speed of 4400 m / min, and collected as a nonwoven web on a moving net conveyor.

(Preliminary thermocompression bonding)
The collected non-woven web is passed between a pair of upper and lower metal flat rolls, each flat roll surface temperature is 140 ° C., pre-thermocompression bonding is performed at a linear pressure of 60 kg / cm, the fiber diameter is 10 μm, and the basis weight is 36 g. A spunbond nonwoven web (g) in a temporarily bonded state with a thickness of 0.16 mm / m ² was obtained.

(Laminated thermocompression bonding)
Two sheets of the temporarily bonded spunbond nonwoven web (g) thus obtained were superposed and a laminated composite nonwoven fabric was produced in the same manner as in Example 1 to obtain a separation membrane support. The surface temperature of the three flat rolls at this time was 100 ° C. on the top, 180 ° C. on the inside, 140 ° C. on the bottom, and the linear pressure was 1715 N / cm. The evaluation results are shown in Table 2.

(Separation membrane formation)
Using the obtained laminated composite nonwoven fabric, a separation membrane was obtained in the same manner as in Example 1. Although the produced separation membrane was excellent in smoothness, it was inferior in chemical resistance and could not be suitably used for wastewater treatment containing oil and chemicals.

[Comparative Example 4]
In the spinning, nonwoven web collection and temporary bonding steps, a temporarily bonded spunbond nonwoven web (h) having a basis weight of 25 g / m ² was obtained. A polyester having a basis weight of 50 g / m ² , a thickness of 0.07 mm, and a basis weight CV of 3.5%, except that this spunbond nonwoven web (h) was used. A spunbond laminated composite nonwoven fabric was produced to obtain a separation membrane support. The evaluation results are shown in Table 2.

[Comparative Example 5]
In the spinning, nonwoven web collection and temporary bonding steps, a temporarily bonded spunbond nonwoven web (i) having a basis weight of 15 g / m ² was obtained. A polyester span having a basis weight of 30 g / m ² , a thickness of 0.04 mm, and a basis weight CV of 3.9%, except that this spunbond nonwoven web (i) is used. A bonded laminated composite nonwoven fabric was produced to obtain a separation membrane support. The evaluation results are shown in Table 2.

[Comparative Example 6]
(Spinning and nonwoven web collection)
A polyethylene terephthalate (PET) resin dried at a moisture content of 50 ppm or less and having an intrinsic viscosity IV of 0.65, a melting point of 260 ° C., and 0.3% by mass of titanium oxide is melted at a temperature of 295 ° C. After spinning from the pores at 300 ° C, spinning on a rectangular ejector with slits in the width direction of the nonwoven fabric at a spinning speed of 4400 m / min to form filaments (circular cross section). Collected as a non-woven web. The discharge rate was adjusted so that the basis weight of the spunbond nonwoven web (j) was 30 g / m ² .

Subsequently, after the polyethylene terephthalate resin having an intrinsic viscosity IV of 0.50 and a melting point of 260 ° C. dried to a moisture content of 50 ppm or less was melted at a temperature of 295 ° C. and spouted from the pores at a die temperature of 300 ° C., The melt blown nonwoven web (k) was collected on the spunbond nonwoven web (j) on the moving net conveyor by spinning and spraying by blowing heated air of 1000 Nm ³ / hr / m. The discharge rate was adjusted so that the basis weight of the melt blown (MB) nonwoven web (k) was 10 g / m ² .

Further, the spunbond nonwoven web (l) was laminated and collected on the meltblown nonwoven web (k) under the same conditions as the spunbond nonwoven web (j). The discharge rate was adjusted so that the basis weight of the spunbond nonwoven web (l) was 30 g / m ² .

(Preliminary thermocompression bonding)
The laminated non-woven web collected as described above is passed between a metal flat roll and a net conveyor, preliminarily thermocompression bonded with a flat roll surface temperature of 180 ° C., a linear pressure of 294 N / cm, and a basis weight of 70 g / m. ² to produce a laminated nonwoven web having a three-layer structure of spunbond / meltblown / spunbond in a temporarily bonded state having a thickness of 0.35 mm.

(Laminated thermocompression bonding)
The obtained laminated non-woven web in a temporarily bonded state is thermocompression-bonded through a pair of two flat rolls of a resin elastic roll having a metal roll on the top and a hardness (Shore D) 75 on the bottom. A laminated composite nonwoven fabric was produced to obtain a separation membrane support. The obtained separation membrane support had a basis weight of 70 g / m ² and a thickness of 0.09 mm. The surface temperature of the two flat rolls at this time was 230 ° C. on the top and 130 ° C. on the bottom, and the linear pressure was 1519 N / cm. The evaluation results are shown in Table 2.

(Separation membrane formation)
Using the obtained composite nonwoven fabric, a separation membrane was obtained in the same manner as in Example 1. Although the produced separation membrane was excellent in smoothness, it was inferior in chemical resistance and could not be suitably used for wastewater treatment containing oil and chemicals.

Claims (4)

A separation membrane support made of a nonwoven fabric, wherein the nonwoven fabric is composed of fibers mainly composed of polyphenylene sulfide, and the basis weight of the nonwoven fabric is 20 g / m ² or more and 100 g / m ² or less, and the basis weight CV is A separation membrane support, which is 4.0% or less. The separation membrane support according to claim 1, wherein the fibers constituting the nonwoven fabric are core-sheath type composite fibers. The separation membrane support according to claim 1 or 2, wherein the nonwoven fabric is a laminated composite nonwoven fabric in which a plurality of nonwoven webs are integrated by thermocompression bonding. A separation membrane in which a membrane having a separation function is formed on the surface of the separation membrane support according to any one of claims 1 to 3.